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- Creator:
- Schack, Leigh-Ann N.
- Description:
- Organizational culture has been studied in many different disciplines. In Management and Business studies, organizational culture is often viewed as a concept that can be influenced or changed within organizations. Having a System’s Theory basis, many models of organizational culture are compatible within Critical Ecological System’s Theory which is often used by Social Workers. Critical Ecological System’s Theory recognizes organizations as a system to interface with clients. Values are an essential aspect of organizational culture and are foundational in the Social Work profession. Organizational culture models may be useful in aiding the application of values throughout social work organizations. This paper uses organizational culture concepts to inform guided interviews of behavioral health employees of a single organization with two sites that have reportedly different cultures. Information gained from these interviews as well as principles from organizational culture models are used to formulate the guidebook, Cultivating a Workplace Culture for Social Workers.
- Resource Type:
- Thesis
- Campus Tesim:
- Chico
- Department:
- Social Work
- Creator:
- Koehn, Marcia
- Description:
- This study examined the policies of schools of social work within the California State University system regarding how they evaluate for admission and inform in-coming students with criminal convictions of the challenges they may face upon graduation. Data was collected through secondary sources and two online surveys, one for faculty of programs and one from currently enrolled and alumni students of those programs. Findings revealed that few programs have policies regarding students with criminal convictions, a small number of faculty were aware of those policies, and students did not feel informed of the challenges they would face upon graduation due to their criminal convictions.
- Resource Type:
- Thesis
- Campus Tesim:
- Chico
- Department:
- Social Work
- Creator:
- Johnson, Austin
- Description:
- As of 2017, California is spending over $70,000 to house each inmate every year in the country with the most prisoners per capita in the world (Legislative Analyst’s Office, 2017). In accordance with realignment policies, restorative justice programs have developed to meet the need of reducing the prison population in a cost-effective way. While recidivism rates have shown to be lower for many participants, simply having the offender out of jail is not the only measure of a successful rehabilitation program. Building upon the cornerstones of restorative practice, collective empathy was developed and utilized as a framework for an original survey instrument, the Collective Empathy Scale (CES). This project introduces the CES as a method to measure four domains of collective empathy: self-compassion, empathic concern, community connection, and perspective taking. The CES attempts to measure a change in behavior that promotes each of these domains. Collective empathy is an indicator for less harmful behaviors as there already exists a correlation between empathy and recidivism. Building collective empathy within communities could similarly reduce the harm imposed on one another. The literature shows strong supporting research behind measuring empathy, while conceptual frameworks of collectivism, humanism, and social ecology share a focus on community building. Various limitations were considered in the development and for future use. Methods for survey evaluation and validation are included to further the development of the instrument.
- Resource Type:
- Thesis
- Campus Tesim:
- Chico
- Department:
- Social Work
- Creator:
- Clanton, Marc William
- Description:
- This study attempts to elucidate some of the complexity of the Romanian and California Child Welfare systems and provide insight that will enhance the outcomes of the children within them. This is done by synthesizing 1) the history of these agencies, 2) literature on the effects of these systems on children and effective treatments for traumatized children, and 3) the efficacy of the systems as perceived by the social service workers in close proximity to these systems. Six participants were recruited, three from Romania and three from California. They were interviewed to determine their views on their respective system. Relevant themes were gleaned from the data, such as the prevalence of stigma toward children in these systems, the role of attachment in the development and treatment of trauma, and the overall desire for change within these systems. These, along with other themes, were analyzed in relation to existing literature and several key concepts were identified. These concepts included the need for a shift in cultural perspective in order to reduce stigma toward foster youth, especially LGBTQ foster youth, as well as the need for systemic change. Consistency, permanency, early intervention, and trauma informed care were identified as crucial elements of successful interventions, and steps should be taken in order to incorporate them into these systems of care.
- Resource Type:
- Thesis
- Campus Tesim:
- Chico
- Department:
- Social Work
- Creator:
- Bradford, Aubree
- Description:
- As the number of first-generation college students (FGCS) increase at California State University, Chico (CSUC), there is much to learn about their involvement on campus. First-generation college students struggle with classroom and campus involvement on campus. This Project offers data from first-generation and non-first generation college students (NFGCS) on campus. This Project focused on the level of involvement of first generation college students and barriers to classroom and campus involvement. The first goal of this Project was to investigate and understand how classroom and campus climate influence student involvement and participation on CSUC campus. The second goal was the development of a campus report for the university that provides faculty, staff, and departments on campus with recommendations on how to create a more inclusive and diverse classroom and campus environment.
- Resource Type:
- Thesis
- Campus Tesim:
- Chico
- Department:
- Social Work
- Creator:
- Maziarz, Jacob
- Description:
- Wetland ecosystems are among the most biologically productive ecosystems on Earth, yet they are being lost and degraded at an alarming rate. A growing trend to offset this loss is to construct artificial wetlands to replace the destroyed natural wetlands, yet our understanding of how to construct artificial wetlands, and make them functional, is vastly underdeveloped. This study sampled stocks of nitrogen (N) and carbon (C) in an artificial wetland on the California State University San Marcos (CSUSM) campus and compared them to stocks from local wetlands. Samples were taken from both plant biomass and soil to assess the stocks of C and N throughout the wetlands. Plant cover was also measured at each site via a line-intercept method. We hypothesized that C and N stocks would be significantly lower in the artificial wetland than the natural wetlands due to the young age of the artificial wetland while plant cover and biodiversity (species richness) would be similar across all wetlands. The study revealed a large degree of variation among the three wetlands and that soil and vegetation C and N stocks of the CSUSM wetland appeared to plateau after 11 years. However, the CSUSM wetland C and N stocks and plant cover were higher than, or comparable to, the two local wetlands. Plant species composition was unique for each wetland, with only five species shared among two or more sites. The local wetlands showed a great deal of variation between themselves. Batiquitos showed very low soil and plant C and N stocks, while the site at Cannon Road had much higher stocks, especially in its plant biomass. While this study demonstrated that CSUSM was functioning at least on par with local wetlands, it also raises a number of implications regarding the functional status of wetlands in California. The two local wetlands have a history of anthropogenic disturbance and alteration. California wetlands, both those sampled in this study and those from other studies, showed high variability amongst themselves. In some comparisons, artificial wetlands seem to sequester nutrients even better than a natural wetland, but in other comparisons, failed to match nutrient stocks. This high variability can originate from differences in wetland hydrology, plant abundance and species composition, differences in surrounding terrain, and anthropogenic alterations. California wetlands had much lower nutrient stocks compared to wetlands in other parts of the U.S., which is presumably caused by regional differences in hydrology.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Naumann, Kenneth
- Description:
- DNA storage in the nuclei of cells is important for both compaction and the regulation of gene expression. DNA packaging is altered by chemical modifications to the tails of the histone octamer around which the DNA is wrapped, specifically histones H3 and H4. Collectively these various histone marks make up a pattern which has been termed the “histone code”. The multiple interactions between histone modifications and gene expression is not well known in diseased cells. The objective of this study is to better understand the histone modification differences between normal and cancerous cells, and the potential for manipulating this code, due to the reversible state of modifications. By comparing malignant and non-malignant cells before and after treatment with inhibitors targeting histone modification pathways, we are able to observe changes in histone post-translational modification (PTM) levels. These changes indicate it is possible to change the histone pathways to effect gene expression.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Ainslie, Nicholas
- Description:
- Paralemanea is a freshwater red alga genus in the family Lemaneaceae, of which Paralemanea catenata is a member. The cues by which it regulates its triphasic sexual life history are not well known, either in terms of environmental stimuli or mechanisms. The P. catenata genome has not been sequenced, and RNA sequencing was used to perform the initial investigation. Comparing morphological and ecological measurements (total length, internodal length, spermatangial ring height, number of nodes, and node width; temperature, pH, total dissolved solids, photoperiod, salinity, and conductivity) taken over its growing season, in concert with the RNA sequencing data, suggests photoperiod is the environmental stimulus by which P. catenata regulates its life cycle. Involved in this regulation are phototropins and cryptochromes, which are light-sensitive proteins that allow the alga to continuously monitor light levels and respond to this stimulus.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Holt, Kali
- Description:
- A large portion of nitrogen deposition on southern California’s chaparral and coastal sage scrub (CSS) is due to anthropogenic sources. The implications of increasing soil nitrogen, and the relationship between soil nitrogen and carbon on soil microorganism growth and activity, are not well understood. Possible interactions between N inputs and soil C availability on soil respiration and microbial biomass were assessed in chaparral and CSS plots that have been experimentally treated with N for about 12 years. Soil (microbial + autotrophic) respiration and microbial biomass were measured in four conditions: in plots exposed to added and ambient N, and within these plots, under shrubs and in open spaces, which represent microsites with differing N and C availability. We measured soil respiration and microbial biomass in these conditions every 3 months for a period of 1 year to test the hypothesis that respiration and microbial biomass would (1) increase in plots with higher C and N availability and (2) be higher during the winter and spring because of higher soil water availability. Our results indicate that soil respiration was significantly higher under shrubs but not in plots exposed to added N while microbial biomass was significantly higher in plots exposed to added N but not under shrubs. Soil respiration and microbial biomass were higher in the summer months than during the winter and spring months. These results were observed for both CSS and chaparral, indicating that the effects of long-term N exposure on soil microbial activity and biomass may be general for semiarid shrublands. While speculative, the N-induced increase in microbial biomass, without an increase in activity (respiration), suggests that N exposure has altered the soil microbial community. A change in the soil microbial community has important implications for soil N and C cycling and storage, especially in semi-arid chaparral ecosystems subject to large inputs of atmospheric N.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Lopez, Sarah
- Description:
- In the push to determine a means to decrease the rate of biological aging in humans, conclusions about over-the-counter use of some anti-aging drugs may be premature. Rapamycin is one drug that, while currently prescribed as an immunosuppressant for various organ transplant recipients, is also being investigated by the National Institutes of Health for over-the-counter use. The presence of intestinal parasites (such as helminths) in the United States is rarely noticed, but intestinal parasitic infections do occur in the United States and citizens of the United States have wide access to over-the-counter drugs. Using rapamycin as an over-the-counter option to combat biological aging, without understanding the effects of rapamycin on susceptibility to parasites, may be deleterious. For my thesis, I examined the effects of rapamycin ingestion by hosts on (1) host susceptibility to two parasite species and (2) on growth and reproduction of the parasites. I found that parasitized hosts food intake, or body mass did not differ between diets, but there was a significant initial increase in body mass and food intake decreased after infection regardless of diet. The rapamycin-fed hosts that were infected with nematodes had a significant decrease in parasite specific immunoglobulin (Ig) G1 when compared to the parasitized hosts on control chow, but for mice infected with the cestode there was no difference in parasite-specific IgG1. Despite changes in IgG1 production, the thymus wet mass, total number of thymus cells, and differential white blood cell counts did not differ for parasitized hosts on rapamycin diet compared to parasitized hosts on control diet. Increase in eosinophil production occurred as expected during nematode infection regardless of diet, but was lessened during cestode infection for rapamycin-fed mice. The infection intensity in the host from either parasite did not differ between diets. The worm length for nematodes did not differ between the host diets, but worms taken from hosts on the rapamycin diet had a significant increase in egg output when compared to worms taken from mice on control chow. Cestodes from hosts on the rapamycin diet had a significant increase in worm mass and egg output when compared to worms taken from mice on the control diet. My pursuit to gain knowledge of the effects of rapamycin on hosts with intestinal parasites has left several questions unanswered, but we have determined that rapamycin ingestion by the host may benefit growth and reproduction of some helminth parasites.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Dunning, Andrea
- Description:
- Roads are recognized as a source of increased mortality and restricted movement among populations, and are expected to impact population connectivity. However, roads that are permeable barriers would still allow some degree of gene flow, and reduced abundance near roads might partially offset the smaller number of migrants across the road by increasing the genetic dissimilarity of individuals on either side of the road. Matings that do occur across the road may therefore be negatively assortative with respect to genotype, increasing levels of gene flow. I examined dispersal and gene flow in simulated populations of terrestrial territorial vertebrate organisms with juvenile dispersal, roughly based on Agassiz's Desert Tortoise (Gopherus agassizii), a species known to show population-level changes in abundance near roads. I looked at population abundance and gene flow in the absence roads, compared with populations with roads that are impermeable barriers, roads that are permeable with different levels of mortality, and roads that are impermeable barriers with crossing areas. Increased levels of road mortality significantly decreased population abundance immediately surrounding the road, with the width of the population depletion zone increasing with increasing road mortality. Allele frequency in the immediate vicinity of the road was not affected by the decreased population, and gene flow was maintained across the roads, with only the most deadly road showing some long-term attenuation of gene flow. Decreased population abundance around the road was not accompanied by a corresponding decrease in gene flow. Although roads have well documented negative effects on population abundance, managers should not assume that reduced abundance means reduced gene flow in all cases, and fencing to avoid road mortality is expected to reduce gene flow more than road mortality does in many cases. Conservation actions to prevent road mortality need to also address potential loss of gene flow, and follow up to make sure mitigation measures are effective.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Hentz, Cloe
- Description:
- The tropical savanna of Brazil (cerrado) is extremely species diverse and it encompasses many different physiological features. These physiological differences are influenced by rainfall and nutrient availability in the soil. Plant litter decomposition recycles nutrients from plants to soil and in turn, affects nutrient availability and plant growth. However, the rate at which these nutrients become available to the soil, and how mineralization is affected by litter inputs, are poorly understood. Thus, a field experiment was conducted to assess how litter inputs and reductions affect nitrogen (N) and phosphorus (P) availability. It was hypothesized that N and P mineralization would be significantly influenced by manipulation of the surface litter and that there would be a positive correlation between soil moisture and nutrient mineralization. Results showed that litter inputs or reductions did not significantly affect net mineralization, extractable soil organic carbon (SOC), P, and N, and total mineralization. There were significant differences between sites and over time for net N and SOC mineralization, extractable SOC, N, and P, and total mineralization. There were also site versus time interactions found for net N and SOC mineralization and extractable N and SOC due to the transition between wet to dry seasons within the duration of the experiment. Four variable step-wise regressions (air temperature, relative humidity, soil moisture, and precipitation) helped explain the abiotic factors that contribute to the variance in P, N, and SOC mineralization and extractable P, N, SOC at each site. Our results indicate that a short term manipulative experiment (six months) was not an adequate amount of time to alter nutrient availability in response to litter manipulation. Extending this study could produce significant results and help explain the effects of land use changes on nutrient output in these highly manipulated tropical forests.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Fenner, Andrea
- Description:
- Anthropogenic nitrogen (N) deposition represents a significant input of N into coastal sage scrub (CSS) and chaparral ecosystems of Southern California. Increased N deposition has the potential to alter the decomposition rate of soil organic matter (SOM) in N limited terrestrial ecosystems through altering the enzymatic activity of soil microorganisms that play a key role in the decomposition process. Since few reports have examined the effects of N deposition on the enzymatic activity of soil microorganisms in semi-arid shrublands, this study aimed to determine how N deposition affects the enzymatic activity of microorganisms that drive the decomposition process. Based on results from other ecosystems, we hypothesized that added N would suppress the enzymatic activity of ligninolytic enzymes (phenol oxidase and peroxidase) and would increase the enzymatic activity of the cellulolytic enzyme, p-Nitrophenyl-ß-D-glucosidase. Enzyme assays were conducted on soil samples collected from eight plots located at two field sites where N addition experiments had been conducted over the last 10 years. Field sites were composed of four unmanipulated control plots and four experimental plots, which received 50 kg N/ha annually. Data collected from the chaparral site indicated that there was a significant difference in peroxidase activity between control and N treatment plots (p-value= 0.016) and a significant difference over time for control and treatment plots in p-Nitrophenyl-ß-D-glucosidase activity (p-value= 0.032) and phenol oxidase activity (p-value= 0.003). Data collected from the CSS site indicated that there was a significant difference in peroxidase activity between control and N treatment plots (p-value= 0.010) and a significant difference over time in peroxidase activity (p-value= 0.001). In addition, there was a significant difference over time for control and treatment plots in p-Nitrophenyl-ß-D-glucosidase activity (p-value= 0.0003) and phenol oxidase activity (p-value= 0.001). The decrease in p-Nitrophenyl-ß-D-glucosidase activity and the lack of suppression of phenol oxidase in some added N plots when compared to control plots differed from our initial hypothesis and was inconsistent with other findings from previous literature. However, much of the findings from previous literature focus on how N deposition affects the activity of enzymes involved in the decomposition of litter not SOM, and because peroxidase may be important in the degradation of older structural C, which is typical of soils, it may not be too surprising that our results indicate that only peroxidase was significantly affected by N addition. Little is known about how N deposition affects the enzymatic activity of enzymes involved in the decomposition of SOM, and whether the activity of these enzymes follow the same patterns of those involved in the decomposition of litter. Findings from this study may provide the insight needed to determine how N deposition affects the activity of enzymes involved in the decomposition of SOM thus, giving us a better understanding of how N deposition affects decomposition rates of SOM in semi-arid shrublands.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Snow, Robin M
- Description:
- The importance of perennial access to water for invasive plants in arid environments was examined at eighteen sites containing Eucalyptus groves in proximity to a water source within San Diego County between June I stand September 30111, 2009. Diameter at breast height (d.b.h.) measurements, a useful indicator of tree size, were measured along transect lines at each site prior to September. D.b.h. distribution curves were examined for significant gaps which should indicate missing cohorts, which were expected where water is intermittent due to variation in germination rates and seedling mortality during drought conditions. In September, the peak of the dry season, each site was evaluated for water presence in the stream bed, evidence of seedling mortality and surface soil moisture. Arc View 9.2 software was used to gather data on elevation, slope (mean, s), proportion of sandy loam type soil present, and to digitize polygons around the canopy area of study sites. Soil type, surface soil moisture, seedling prevalence, slope, and September presence of water were evaluated as predictors of total canopy area, proportion of seedlings present, and proportion of significant gaps in the size class distribution. The total canopy area and proportion of seedlings could not be predicted using the measured variables, however, the proportion of significant gaps was explained by slope (s), seedling proportion, gap cutoff size, soil moisture at Om from the stream bed and September water presence (an indicator of perennial access to water). The low number of gaps seen at sites with access to perennial water sources suggests that continuous access to water is a risk factor for river red gum establishment and recruitment. Alteration of the natural flow regime, from seasonal to perennial, by supplemental water inputs may represent an emerging threat to riparian ecosystems in semi-arid environments. KEYWORDS California, Eucalyptus, impacts, invasive, riparian, water Item only available to the CSUSM community. Authentication with campus user name and password required.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Kroon, Joanna L
- Description:
- Cortaderia selloana, or pampas grass, is a serious invader of disturbed, coastal and riparian ecosystems in Southern California. The purpose of this study was to determine how the growth and physiology of C. selloana respond to various combinations of soil nitrogen and water table depth. Growth factors examined included plant biomass, plant height and width, number of tillers per plant and specific leaf area (SLA). Physiological factors examined included water use, photosynthesis and tissue nitrogen and phosphorous contents. These response variables were examined in a manipulative study using a 2 x 3 random factoral design with two water table and three nitrogen levels. Water, nitrogen and the interaction between the two were found to have a significant influence on many of the growth and physiological factors of Cortaderia selloana. Added nitrogen caused increases in plant biomass that were 5 to 9 times higher than plants exposed to ambient nitrogen. Both water and nitrogen influenced the number of tillers per plant, where a lower water table and higher nitrogen availability caused an increase in the number of tillers. C. selloana also responded to increased water and nitrogen with greater average plant height and reduced plant width. By examining which plant response factors are enhanced by the various combinations of water and nitrogen treatments, we hope to gain insight into the invasive nature and success of C. selloana in order to ultimately find less destructive methods to control and prevent the invasion of this invasive grass in the future. Keywords: Biomass, Cortaderia selloana, Disturbed ecosystems, Invasive species, Pampas grass, Riparian ecosystems, Specific leaf area
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Williams, David Earl
- Description:
- While performing, racehorses use the transverse gallop gait. When a racehorse begins to gallop, it must use either the right lead stride pattern (RLSP) or the left lead stride pattern (LLSP). When racehorses make a trot-to-gallop transition, 91% start with their RLSP and 9% start with their LLSP (n=209). When breaking from the gate, 90% of all racehorses use their RLSP and 10% use their LLSP (n=9,116). When individual horses were observed breaking from the gate in five to seven races, they used the same lead 94% of the time (n=32). When a mirror image of the hoofprints from a RLSP was superimposed on the hoofprints of a LLSP for the same racehorse, the placement of the hoofprints was not identical. This suggests that running efficiency might be different in the RLSP and the LLSP. The preference of stride patterns, along with a potential differences in efficiency, could have important consequences for racehorse performance.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Veazey, Gregory Darryl
- Description:
- White Spot Syndrome Virus (WSSV), a dsDNA virus, is the most important viral pathogen in cultured penaeid shrimp worldwide. In cultured shrimp, WSSV infection can reach a cumulative mortality of up to 100% within 3-10 days upon infection. Intensive shrimp cultivation, inadequate sanitation, and worldwide trade have aggravated the disease dissemination. As such, WSSV has become an epizootic disease and is not only a major threat to shrimp culture but also to marine ecology. In recent years, considerable progress has been made in characterizing the WSSV at the molecular level and developing highly sensitive methods for WSSV detection. However, information pertaining to shrimp cellular genes that are involved in WSSVhost interaction is very limited. To address this issue, this research project took an expressed sequence tags (ESTs) approach to isolate and characterize randomly selected eDNA clones from a hepatopancreas eDNA library ofWSSV-infected shrimp, in order to isolate genes that might play a role in WSSV pathogenesis. The expression of immune/receptor genes, lectin (PsEST 640) and a low-density lipoprotein receptor (PsEST 160) were identified by EST analysis, were measured by RT-PCR. Real-time quantitative (RT-PCR) using SYBR Green chemistry has been shown to be a rapid and highly sensitive detection method for shrimp viruses as well as to measure cellular gene expression in shrimp. A statistically significant difference was observed in the expression of lectin at 32 h p.i. with upregulation in healthy compared to that ofWSSV-infected. LDLr, a receptor known to interact with viruses, had increased expression in the WSSV-infected individuals at 4 h p.i. compared to the healthy. Our data suggests that lectin is a highly diverse, inducible protein that may play a direct/indirect role in either binding WSSV and/or initiating some humoral defense mechanism (i.e. prophenoloxidase cascade). In addition, LDLr gene was found to play a role in shrimp-WSSV interaction, and possibly be a receptor to which the virus binds.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Urbach, Michael Jay
- Description:
- In aquaculture facilities worldwide, T enacibaculum maritimum is a common marine pathogen that infects important marine fish species causing flexibacteriosis. Monitoring T. maritimum levels is important for effective treatment to mediate possible outbreaks and to avoid the spread of disease and associated mortalities. In an effort to improve surveillance for the presence of T. maritimum, a rapid, real time PCR assay was developed. By amplification and detection of the 16s ribosomal gene using TaqMan chemistry, relative quantitation of the pathogen is possible from mixed environmental water samples. This protocol allows T. maritimum levels to be assayed quickly from seawater samples without obtaining invasive tissue samples and prior to presentation of gross signs of infection. Keywords: Real-time PCR, Tenacibaculum maritimus, Pathogen assay, TaqMan
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Tamulis, Walter Gregory
- Description:
- Retrotransposons encompass a specific class of mobile genetic elements that are widespread across eukaryotic genomes, the impact of which are just beginning to be deciphered. In a step towards understanding their role in litopenaied shrimp, we have herein identified ten non-LTR retrotransposons and their putative phylogenetic placement. Two Litopenaeus stylirostris elements were discovered through standard and degenerate PCR amplification using previously defined non-L TR primers. A third genomic L. stylirostris element was identified using specific priming from an amplification protocol. These three PCR-derived sequences showed conserved domains of the non-LTR reverse transcriptase gene. A degenerate, 3' located non-L TR retrotransposon showing homology to ZEPP elements was isolated through screening of an L. stylirostris genomic library. In silica searching of genome databases and subsequent contig construction yielded six non-LTR retrotransposons (both genomic and expressed) in the Litopenaeus vannamei genome that also exhibited the highly conserved domains. Phylogenetic placement among representatives from all non-LTR clades showed a possibly novel monophyletic group. This group included elements from both L. stylirostris and L. vannamei and appeared most closely related to the highly active R TE clade. Our remaining four sequences placed in the CRl and I clades of retrotransposons, with one showing high similarity to ancient Penelope elements. This research identifies active retrotransposons in litopenaied genomes. Keywords: retrotransposon, litopenaied, penaied, non-LTR, IHHNV
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Stutzer, Gregory Martin
- Description:
- Biotelemetry studies assume that vital biological processes are unaffected by the attachment method and presence of the transmitter. I examined the effects surgically implanted transmitters (representing 0.2-0.9 % of body weight) had on feeding activity, growth, tissue reaction, and survival of 70 adult white seabass, Atractoscion nobilis, (72.5-120.4 em total length) over a 451-day period. On day 97 (expected transmitter life), analysis of growth in standard length revealed no significant difference among fish exposed only to handling and anesthesia (controls), surgery but no implanted transmitter (sham-surgery), dummy transmitters surgically implanted (dummy-surgery), and functional transmitters surgically implanted (active-surgery). However, during this period active-surgery fish gained significantly less weight than sham-surgery fish. No significant difference in growth occurred among control, sham-surgery, and dummy-tagged fish over the remaining 354 days of the study. Differences in feeding activity of fish among the four treatment groups were significant during 12 recorded feeding trials over the first 32 days, but were likely influenced by the behavior of a few dominant individuals .. Incision healing was complete after 97 days, with light necrosis at the insertion points of sutures. All transmitters were completely encapsulated by fibrous connective tissue within 97 days. No gross morphological differences were observed in the tissue encapsulating dummy or active transmitters, and no fish expelled transmitters through the body wall, via the intestinal tract, or incision site over the 451 day study period. Two mortalities occurred during the study when sham-surgery fish died on day 17 and 41. My results show that with the described surgical procedures, intraperitoneal implantation provides a suitable technique for future biotelemetry studies on adult white seabass.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Steinberg, Judith Skye
- Description:
- Serial analysis of gene expression (SAGE) was used to examine gene expression profiles of healthy (pathogen-free) Litopenaeus stylirostris. Of the one thousand eight hundred forty-two SAGE clones sequenced, we found seven thousand six hundred and sixtysix SAGE tags. Transcript identification of the healthy L. stylirostris SAGE tags was completed using the reference databases, from SAGEmap. A total of six thousand five hundred forty SAGE tags to gene assignments were matched to a UniGene ID. The set of reliable SAGE tags were used to biologically characterize their function using the Gene Ontology database. SAGE tags that represented transcripts that encode genes found in the Gene Ontology database were divided into seventeen categories according to the major functions of their encoded proteins. From these characterized genes, one hundred four genes were found to be immunity related genes, some which have been seen for the first time in penaeid shrimp, such as neutrophil cytosolic factor 1, and eosonophil peroxidase. The genes identified in this healthy L. stylirostris SAGE library are just the beginning to understanding global gene expression in shrimp. Future research includes sequencing an infectious hypodermal and hematopoietic necrosis virus (lliHNV) infected L. stylirostris SAGE library to compare to the healthy L. stylirostris SAGE library and analyze gene expression of immune related genes including what has been found in this research. Key Words: Litopenaeus. stylirostris, Serial Analysis of Gene Expression; penaeid, innate immunity, ditag, SAGEmap
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Sendall, Kerrie
- Description:
- Measurements of the leaf photosynthetic light response, water potential, and specific leaf area of two tropical transitional forest tree species, Tovomita schomburgkii and Brosimum lactescens, were quantified to establish how these properties are affected by seasonal variations in rainfall and leaf canopy position. The study was conducted at a site near Sinop Mato Grosso, Brazil, which is located within the ecotone of savanna and tropical rain forest. Understory T. schomburgkii leaves showed no significant difference in water potential ('I'L) between the dry season (June-Sept.) and the wet season (Dec.-Feb.); however mid-and upper-canopy leaves of both species exhibited significantly lower water potential during the dry season. Both species exhibited seasonal variations in light saturated photosynthesis (P m), dark respiration (Rd), and maximum stomatal conductance (gmax) which were positively correlated with precipitation. Internal leaf C02 concentrations (Ci) were consistently lower during the dry season suggesting that declines in stomatal conductance of C02 caused decreased levels of maximum photosynthesis. During the wet season P m and RI of both species were significantly negatively correlated with specific leaf area (SLA) but during the dry season this correlation was only observed in T. schomburgkii. These results suggest that seasonal drought has important implications for the physiology of semi-deciduous Amazonian forest trees and that the seasonal trends ofPm, RJ, and gmax are more comparable to savanna than to tropical rain forest. Keywords: photosynthesis, seasonality, tropical transitional forest, Tovomita schomburgkii, Brosimum lactescens
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Rosaler, Jeffrey R
- Description:
- The annealing algorithm in MARXAN was used to build possible marine reserves by selecting the best of 26 heterogeneous rocky intertidal sites using various modeling parameters. Because comprehensive data on biological diversity is impractical to gather for large areas, four surrogate data sets were used to design marine reserves; habitat, substrate, mobile species abundance and sessile species percent coverage. Habitat data was quantitatively assessed for the entire 7.12 miles of Laguna Beach coastline. Habitat characteristics observed were; substrate type; formation type; slope; habitat heterogeneity; presence of microhabitats and wave exposure. The habitat data was used to develop a map and database of these heterogeneous intertidal areas in ArcGIS. Using the ArcGIS, substrate coverage in square feet was determined for each site. Species assemblage data was collected for 26 of the rocky intertidal sites. Macro-algae and macro-invertebrate abundance and coverage were quantified for a 30 m2 area of each site. Three transeets and nine quadrats were placed at random within the 30 rn2 area to determine mobile species abundance and sessile species percent coverage. Variable by site Multi Dimensional Scaling showed similarities between surrogates and Canonical Correspondence Analysis ordination displayed a significant correlation between substrate and species distribution. MARXAN was used to develop a network of sites for each biodiversity surrogate, conserving 10%, 30% and 50% of the surrogate input variables and minimizing the sites chosen. Mean species richness and diversity were higher in the sites chosen to be included in a reserve than outside a reserve, for the mobile and sessile surrogates. Mean species richness and diversity were higher for reserves designed based on species assemblages than reserves designed based on habitat or substrate, but not significantly so. These findings suggest that habitat level surrogates would be an effective method to identify valuable intertidal areas as high priority sites for inclusion in a larger MP A network. Site irreplaceability analysis determined that several sites were chosen > 65% of the time for all annealing runs. The habitat at these sites suggests that two different types of intertidal produce unique species assemblages: low sloping boulder fields and large areas of bedrock bench. Given that different habitats produce diverse species assemblages, it would therefore be important to include representatives of multiple intertidal habitat variations in a reserve network. Keywords Marine reserves, habitat diversity, species richness, species diversity, rocky intertidal habitat, marine protected areas, MARXAN, coastal resource management.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Robles-Sikisaka, Refugio
- Description:
- Taura syndrome disease, caused by Taura syndrome virus (TSV), is one of the most important viral diseases of penaeid shrimp in the Western Hemisphere. A 3278 bp eDNA representing the 3' end of the TSV genome was cloned and sequenced. Sequence analyses revealed a 5'-terminal 19 non -coding bases followed by a long open reading frame encoding 10 11 amino acids (aa), and a 3' untranslated region of 225 nts. The deduced aa sequence of TSV showed significant similarities with those of the coat proteins of several insect picomaviruses. A single transcript of approximately 10 kb was detected by Northern blot hybridization suggesting that the TSV coat protein gene is not expressed as a subgenomic RNA. The genome organization ofTSV is similar to insect picornaviruses. Therefore, this is the first molecular evidence of occurrence of a picomavirus in the class Decapoda. The putative VP2 and VP3 capsid protein genes ofTSV from 17 geographical isolates collected from US, Mexico and Taiwan were amplified by RT-PCR to assess the genetic diversity and phylogenetic relationships among isolates. Alignment of the capsid proteins showed nonconservative changes that may be involved in antigenicity and/ or virulence of the isolates. Phylogenetic analyses revealed that the TSV isolates clustered in two main groups, one Mexican group and one mixed group of Mexican, Taiwan and Texas isolates indicating a shared phylogenetic relationship and a possible common origin.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Robertson, Lyndsey
- Description:
- The overall objective of this research was to identify and characterize the myostatin or myostatin-like gene sequence in the commercially important aquaculture species Litopenaeus stylirostris. Myostatin is a negative regulator of muscle growth and when disrupted can cause a "double muscled" phenotype (McPherron et al., 1997). Two main approaches were taken: the first was to isolate an mRNA (eDNA) copy and the second was to identify a genomic copy of the gene. The methodologies used were a eDNA PCR screen, screening a genomic library and a genomic PCR screen. Our results indicate there is at least one form of the TGF-B superfamily of genes present in the L. stylirostris genome. The isolated gene fragment is an exact match to the L. vannamei TGF-B sequence. Additional characterization of our sequence indicates that it most closely resembles a BMP6 type TGF-B gene. Our fragment is located in the 3' highly conserved C terminus region, common to all TGF-B gene members, and just downstream of the proteolytic processing site. This research lays the groundwork and provides promising progress towards the isolation and characterization of important TGF-B genes in L. stylirostris that potentially control or regulate growth in this important aquaculture shrimp. The characterization of growth related genes from an animal of commercial importance such as L. stylirostris can lead to important contributions that will positively impact the shrimp aquaculture industry. Key words: Litopenaeus stylirostris, shrimp, myostatin, transforming growth factor beta superfamily (TGF-B).
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Lawrence, Shelley
- Description:
- Coastal sage scrub and chaparral vegetation of Southern California have become fragmented due to a loss of habitat over the past several decades, which has been caused by several contributing factors such as agriculture, urbanization, increased fire frequency and intensity. Although nitrogen deposition has also been found to be a contributing factor to the loss of coastal sage scrub (CSS) and chaparral habitats in previous studies, the mechanism for these effects not been examined. Leaf tissue from existing field plots, fertilized with nitrogen since 2003, was analyzed for carbon allocation patterns and nutrient retention on a seasonal and annual basis from 2006, 2008 and 2010. Nitrogen fertilization did not have an effect on carbon allocation to cellulose, holocellulose or lignin fractions of leaf tissue in CSS California sagebrush (Artemisia californica) or chaparral chamise (Adenostoma fasciculatum) shrubs. However, it was found that seasonal and interannual variation in soluble carbon were highest in both species, but without any N treatment interaction. It was also found that year and season did have a significant effect on carbon allocation, and these temporal variations were correlated with precipitation rates and nutrient availability. The lack of nitrogen effect in the soluble carbon, holocellulose and lignin fractions suggests these avenues of carbon allocation are linked to life history traits that are specific to each species such as drought tolerance, woodiness, and maturation.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Moore, Brenda Juanita
- Description:
- To understand the complex network of the biological processes of an organism, transcription factors (TFs) and their direct target genes must be identified. In Arabidopsis, the TF GLABRA3 (GL3) is involved in trichome initiation and development. To identify the direct target genes of GL3, an inducible activation system coupled with microarray analysis was performed. To this end, two week old Arabidopsis seedling plants expressing the GL3-GR (glucocorticoid receptor) fusion protein with a native promoter (pGL3) were treated for two hours with dexamethasone alone (DEX), dexamethasone + cycloheximide (DEX +CHX), cycloheximide (CHX) and mock solution (M). Ten genes were selected as candidate genes in DEX and DEX +CHX (in relation to Mock and CHX) respectively and validated by real-time RT-PCR. The results showed that the ten genes were not up-regulated greater than two-fold and the induction of these genes did not occur rapidly after the two hour treatment in the pGL3::GL3-GR plants, indicating these candidate genes may in fact be indirect targets. Gene Ontology analysis of the candidate genes revealed that the GL3 pathway have involvement in biological processes related to abiotic or biotic stress, signal transduction, transcription, and transport. These target genes suggest that GL3 is associated with other TFs and proteins in combinatorial manner. Keywords Arabidopsis, GL3, trichomes, transcription factor, microarray, real-time RT-PCR
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Mikse, Oliver Roland
- Description:
- The global aim ofthis research is to elucidate the role of retrotransposons in stress and immune response. As cloning and sequencing of genes has become commonplace, researchers are finding that the insertion and activity of transposable elements including retrotransposons may directly influence phenotype. There is now evidence that external as well as internal stress, such as that caused by pathogens, will activate the movement of retrotransposons within the genome and this movement may play a role in the organism's immune response (Wessler 1996; Grandbastien 1998). An understanding of the mechanisms behind this movement and determining the identity of the genes that are disrupted due to retrotransposon insertion will lead us to an understanding of the genes involved in the immune pathway. Preliminary data indicates that stress may also induce retrotransposon expression in shrimp (Penaeus stylirostris) making this an informative system for further investigation. In a previous study, genetic markers were identified for infectious hypodermal and hematopoietic virus (IHHNV) resistant and susceptible shrimp populations (Hizer et al. 2002). Sequence characterization of two of the markers revealed partial coding regions of the reverse transcriptase gene for retrotransposable elements. In addition, increased expression activity and movement of the retrotransposon in the virally infected shrimp was observed using real-time PCR. Therefore, the overall goal of this project is to isolate the full-length retrotransposable element and to determine its genomic and expression activity in response to viral stress. The specific objectives of this study are: to identify the full non-long terminal repeat (L TR) element; to identify differences in number of elements present between healthy and virally challenged shrimp; to determine if these elements lie within important genes; and to determine if activation of these elements is important in viral pathogenesis. These studies will increase the limited body ofknowledge ofnon-LTR retrotransposons role in response to stress. Specifically, it will begin to address whether transposition events are consequential in stress immune response to viral pathogenesis. Key Words: Representational Difference Analysis, Penaeus stylirostris, IHHNV, Retrotransposon
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- McCague, Jennifer
- Description:
- Quinones are a class of molecules whose effect on cell growth and apoptosis pathways are poorly understood, yet several quinones are widely used as food preservatives and in cosmetics. This study takes advantage of protein microarray technology to identify specific protein-quinone interactions and to establish which class of proteins that quinones commonly interact with. This will enable us to gain a greater understanding of the biological pathways quinones may influence. Protein microarrays are sophisticated biological tools that allow the simultaneous examination of vast numbers of protein interactions. In this study protein microarray technology was used to examine the interaction oftertbutylhydroquinone (tBHQ) with ~5000 yeast and ~3000 human proteins. Strong interactions identified using the protein arrays were subsequently validated using traditional biochemical assays. The results indicated that tBHQ has a tendency to interact with DNA binding proteins, especially kinases, and exhibits a non-specific, weak kinase inhibitory effect. The results of this study indicated that tBHQ (1) reduced the growth rate of yeast in culture, (2) positively interacted with the yeast, Sir2 protein, and (3) it specifically inhibited the deacetylase activity of human Sir2. Keywords: Microarray, tert-butylhydroquinone, quinones, SIR2, Antioxidant Response Element
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Kaufman, Jessica A
- Description:
- Anoxygenic phototrophic purple sulfur bacteria belonging to the Ectothiorhodospiraceae inhabit alkaline saline to hypersaline eniviromnents, such as soda lakes. Mono Lake, located in California s Eastern Sierras (63 83 feet above sea level), is a saline ( -8% N aCl) and alkaline (-pH 1 0) meromictic lake. Enrichment cultures of sediment samples taken from the eastern shore of Mono Lake yielded a pure culture of Ectothiorhodospira strain MM2. Pigment analysis showed absorption maxima at 866 nm and 800 nm in whole cells, and 771 nm in methanol extracted cells indicating the presence of bacteriochlorophyll a. The major carotenoid present in strain MM2 was spirilloxanthin. Phylogenetic analyses of strain MM2 indicated that it groups within the genus Ectohiorhodo!>pira, and is most closely related to E. haloalkaliphila BN9902, the most alkaliphilic strains in this genus isolated to date. Strain MM2 grew at NaCl levels ranging from 0%-25%, with an optimum at 8% and good growth obtained at up to 20%, thus making it perhaps the most versatile halophilic member of the genus. Strain MM2 was able to grow photoautotrophically and several carbon sources supported good photoheterotrophic growth of this organism. In addition, strain MM2 was capable of aerobic chemoheterotrophic growth in the dark, a property described for only two other species in the Ectothiorhodospiracea. Our initial studies on the regulation of nitrogen metabolism in strain MM2 indicated that atmospheric dinitrogen, ammonia, glutamate, and glutamine could serve as sole nitrogen sources. Growth on low levels of ammonia ( 100 /-LM) and glutamate served to stimulate N2 fixation suggesting the presence of regulatory mechanisms employed by other anoxygenic phototrophic bacteria. Assays of crude extracts of strain MM2 indicated that fixed N2 or exogenous ammonia was incorporated into an organic form via the induction of two parallel pathways under nitrogen limitation conditions: (1) the GDH pathway, and (2) the GS/GOGAT pathway. To our knowledge this is the first report of a bacterium coordinating a dual system for regulating ammonia assimilation under both high and low fixed nitrogen conditions, and presents the question as to why this organism might require such a strategy. Significant GDH activities were also present in N2 versus ammoniagrown cells, suggesting that strain MM2 possesses a novel GDH enzyme with a low Krn for ammonia. All enzyme activities in strain MM2 were NADPHdependent. Experiments are currently in progress to identify and clone genes involved in nitrogen fixation and nitrogen metabolism in this haloalkaliphilic phototroph. A regulatory mechanism linking carbon and nitrogen metabolism as described recently for nonsulfur purple bacteria (Joshi and Tabita, 1996) may also be present in strain MM2. Physiological studies of wild type cells grown anaerobically in the dark in minimal media containing C02 and malate showed that large volumes of H2 gas were produced, suggesting induction of nitrogenase, or some other hydrogenase system as a redox balancing mechanism permitting growth under these conditions. Experiments are currently in progress to characterize this global regulatory phenomenon in Ectothiorhodospira strain MM2.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Coole, Robyn
- Description:
- Habitat loss is thought to be the biggest factor contributing to the decline of shorebirds worldwide. The California coast provides many of the water rich stopovers, wintering and breeding sites that North American shorebird populations depend on during their annual migration cycle. However, most of these sites are heavily managed for human uses, which results in habitat loss and alteration. Even state protected reserves that implement restoration techniques to preserve or restore natural habitat still cause shorebirds to repeatedly return to altered habitat. Losses in shorebird habitat will affect shorebird distribution and abundance at a site. Alternatively, changes in shorebird numbers locally could be due to declines in the species regionally from a loss of habitat in other areas along their migratory route, which causes declines at a local site as a side-effect of declines in regional numbers. This study measured the loss of mudflat habitat in the San Elijo Lagoon in southern California from 2002 - 2012 after tidal flushing was restored in 2001 and related mudflat loss to changes in eight shorebird populations abundance and community composition using monthly bird surveys. Five out of the eight shorebird species analyzed showed decline, but surprisingly only one of those declining species, the American Avocet (Recurvirostra americana), could be explained by the loss of mudflats in the lagoon. Regional numbers did not predict local numbers in San Elijo. Bird species composition among the different survey zones in San Elijo significantly changed over time as species abundances changed at different rates, even though relative numbers were not explainable by changes in mudflat. This suggests that other factors resulting from the change in habitat after the restoration in the lagoon, possibly food abundance and distribution, were affecting the shorebirds there. Based on these results, the species most negatively affected by loss of mudflat are species that breed at the reserve, particularly the American Avocet, and habitat management efforts should be directed at the needs of these species. Given the dependence of shorebird numbers on habitats found within the reserve and the lack of evidence of regional effects, managing habitat for shorebirds at the reserve is likely to increase the numbers there, and benefit the species as a whole.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Wright, Terrence Michael
- Description:
- The primary goal of my thesis project is to classify and characterize mechanisms of neuromodulation in the central nervous system of the medicinal leech, Hirudo medicinafis. In the first set of experiments, N-cells were tested for the presence of autoreceptors to the putative peptide transmitter. There was no effect of A VP on N-cells (2-sample t, p>0.05). Although the statistical power of the test was low, the sample sizes required to detect a significant difference strongly suggest that N-cells do not possess autoreceptors. In a second set of experiments, longitudinal motor neurons (L-cells) were exposed to A VP and recorded from continuously. There was a significant hyperpolarizing effect of A VP on the L-cells (paired Hest=3.26, u=6, p=0.017).This effect was blocked in both High-magnesium and High-calcium salines, implying that the effect of A VP is indirect. This result suggests that the effect of A VP on L-cells is to relax certain defined behaviors, such as bending and swimming. As a means of studying neuromodulation in a sensory input-motor output system, Pressure cells (P-cells) were exposed to lO.oM pilocarpine, and electrical properties measured. There was a highly significant decrease in peak depolarization (paired t= 5.16, u=9, p=0.001) and a highly significant increase in depolarization duration (paired t= 5.16, u=9, p=0.006). This effect was further characterized by investigating the P-Anterior Pagoda synapse. There was no effect of pilocarpine on the P-AP synapse (t-test, p>0.05). These results suggest that AVP's affects are widespread, and provide evidence for other forms of simple learning in the leech.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Hizer, Suzanne Elizabeth
- Description:
- RAPD fingerprints of two shrimp populations (Penaeus stylirostris) were compared to find genetic marker(s) that may be associated with Infectious Hypodermal and Hematopoietic Necrosis Virus (lHHNV) resistance or susceptibility. Of the one hundred 10-mer random primers and one hundred inter-simple sequence repeat (ISSR) primers screened, five primers provided markers specific to the Super Shrimp population and three primers provided markers specific to the wild caught population. The two populations were further characterized for relative viral load (reported as cycle threshold, CT) using real-time quantitative PCR with primers specific to the lHHNV genome. The 13-actin gene was amplified to serve as a control for normalization of the IHHNV viral load. The mean viral load was significantly lower (CT = 34.58; equivalent to 3.3 x 101 copies of IHHNV genome/ng of DNA) in Super Shrimp than in the wild caught population (CT = 23.49; equivalent to 4.2 x 104 copies/ng of DNA; p<0.001; CTvalues are inversely related to viral load). A prediction model was created with Classification and Regression Tree (CART) software where the resultant decision tree uses the presence or absence of three RAPD markers as predictors of the relative viral load. Therefore, an assessment of IHHNV resistance or susceptibility in P. stylirostris is based on the RAPD data only.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Herrera, Karina Noemi Gonzalez
- Description:
- Organisms from each of the three domains of life, including the cosmopolitan unicellular marine alga Emiliania huxleyi, require the trace element selenium for growth:~ Selenium is incorporated into the active site of select proteins, known as selenoproteins, in the form of the 21st amino acid selenocysteine (Sec). Although the function of many selenoproteins remains unknown, many selenoproteins are oxidoreductases involved in redox homeostasis and anti-oxidant defense systems. We have performed a genome-wide analysis of E. huxleyi 's selenoproteins using two approaches. The first approach was to use a BLAST search to identify selenoproteins based on homology, and the second approach was to identify novel selenoproteins using a computational algorithm and a ribonucleoprotein immunoprecipitation (RIP) procedure. Although the RIP procedure did not yield meaningful results, a total of 49 selenoproteins belonging to 19 protein families were identified based on homology, and 22 candidate selenoproteins containing motifs were identified using a computational algorithm. Real time R T-PCR was used to analyze the expression of a subset of selenoproteins under various physiological stress conditions and demonstrated no uniform expression pattern suggesting that these proteins assume several different functional roles in the cell in addition to serving as anti-oxidants.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Henderson, Ryan T
- Description:
- CD4+ T -cell activity, including major histocompatibility class II (MHC II) responses, is vital for proper immune system function including CDS+ T -cell and B cell activation. The identification of antigen specific responses are understudied during chronic Lymphocytic Choriomeningitis virus (LCMV) infection. Therefore, it is pertinent to characterize the functionality and clonal expansion of antigen specific CD4+ T-cell populations to establish a murine model for infection where variables such as viral strain can be manipulated to properly track MHC II restricted CD4+ T cell responses. The expansion of antigen specific CD4+ T cell populations were tracked following the infection of female C57BL/6J mice with LCMV Armstrong (Arm), an acute strain, and LCMV clone 13, a chronic strain. Previously characterized MHC-II l-Ab restricted epitopes, arising from glycoprotein (GP) of the viral proteome, were developed into MHC-11 tetramers. These tetramers were subsequently used to test for the presence of antigen specific CD4+ T -cell populations following exposure to LCMV Arm and clone 13. Fluorescence activated cell sorting (FACS) was used to characterize the expression of a known inhibitory molecule, Programmed Death 1 (PD1), on CD4+ T-cells during acute and chronic infection. Results show that the proliferation and overall degree of CD4+ T -cell expansion are dependent on the specific peptide being presented to CD4+ T -cells by antigen presenting cells (APC's). Following acute infection, CD4+ T-cells expanded on a peptide specific basis, ex vivo, when compared to naive mouse groups. The greatest CD4+ T cell expansion was observed when tracking populations specific for glycoprotein 66 (GP66). Data show PD1 is over expressed on the surface of CD4+ T -cells during clone 13 infection. PDl is also disproportionately over expressed on antigen specific CD4+ T -cells at days 15 and 30 post infection. We here show CD4+ T -cells are dysregulated at the cytokine level following infection with a chronic strain of LCMV, clone 13. Furthermore, this dysfunction coincides with the over expression of a known T -cell lymphocyte inhibitory molecule PDl on the surface of antigen specific CD4+ T -cells. The characterization of PDl expression provides a valuable target for the rescue of CD4+ T cell responses during chronic viral infection in a mammalian model. Keywords: murine, peptide, Lymphocyte dysfunction, T-cell exhaustion, interferon gamma
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Faber, David N
- Description:
- Anthropogenic input may double atmospheric carbon dioxide (C02) by the year 2100. Elevating the carbon dioxide concentration in ocean surface waters alters the carbonate system, lowers the carbonate ion (C03-2) concentration and consequently the saturation state of CaC03. These conditions may impact both the production of CaC03 as well as its persistence in the water column. Laboratory experiments simulating these conditions of elevated pC02 and reduced C03 -2 concentration have been shown to reduce CaC03 production in many marine organisms, including the marine coccolithophorid Emiliania hu.xleyi. Coccolith formation in E. huxleyi increases under phosphorus limitation, demonstrating that factors other than carbonate chemistry can alter CaC03 production in these algae. As a consequence, investigations predicting net carbon flux may require close consideration of factors such as nutrient levels. This investigation focuses on E. huxleyi, grown in a closed system under initial conditions simulating present day and projected atmospheric C02 levels ( -360 and -780!-latm, respectively) and minimal (0.6!-lmol r1) phosphate loading. We found that the elevated pC02 caused a reduction in net calcification owing to a combination of reduced calcification per cell and an observed a "fertilization effect" that caused a proliferation of non-calcified cells. Any enhanced calcification due to phosphate limitation was offset by the effect of elevated pC02• If this shift is representative of natural populations, then there is the potential for a drastic reduction in surface ocean carbonate production by this ubiquitous alga. Furthermore, the decrease in CaC03 may reduce the flux of particulate organic carbon (POC) and particulate inorganic carbon (PIC) to the deep sea.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Davis, Kimberly Ann
- Description:
- The semi-arid shrublands of Southern California are subject to some of the highest rates of atmospheric nitrogen deposition in North America. Little is known about the effects of nitrogen (N) pollution on drought-deciduous coastal sage scrub species (CSS) such as California sage (Artemisia californica) and black sage (Salvia mellifera), and sclerophyllous chamise chaparral species such as chamise (Adenostoma fasciculatum) that inhabit this region. This study monitored the photosynthetic and respiration rates, leaf conductance, leaf nitrogen content and specific leaf area of these species quarterly over the course of two years in a mature CSS stand and a pre-and post-fire chaparral stand. An in-situ experiment was conducted; half of the 10 X 10 meter study plots at each site were subjected to an additional 50 kg N ha-1 in the form of NH4N03 fertilizer in October of 2003 and 2004. The remaining plots served as controls subject to ambient N deposition. Rainfall dependent seasonal changes of these physiological measures that are typical of Mediterranean-type ecosystems were observed, however a multiple analysis of variance (MANOVA) indicates that there were no significant differences between control and experimental plots due to N addition. This may be due to the temporal asynchrony of the artificial nitrogen addition and seasonal rainfall, as the nitrogen was added in the fall when the shrubs are physiologically dormant (CSS) or minimal (CC). The first rains may have flushed the N into downslope streams, away from the rooting zones of the shrubs. Alternatively, the lack of significant differences may be because the shrubs had been engaging in luxury consumption, or were already existing in a state of N saturation. Key words: Adenostoma fasciculatum, Artemisia californica, Salvia mellifera, coastal sage scrub, chaparral, nitrogen deposition.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Wilde, Christina Lynn
- Description:
- One of the major tasks of modem neurobiology is explaining at the neuron level how specific behaviors are produced. Recent work in our laboratory has identified a putative peptidergic neuron in the medicinal leech, Hirudo medicinalis, which we believe, uses an Arg-vasopressin-like peptide as its transmitter. However, before further characterization of this neuron can precede the vasopressin-like molecule needs to be isolated and its molecular structure identified. In the course of this work, we designed an acetone-based extraction of nerve cords, developed a dot-immunoblot assay (DIA) that can be used to monitor the molecule throughout the purification process, and used size exclusion chromatography (SEC) to partially purify the vasopressin-like molecule. Additionally, using enzyme-linked immunosorbent assays (ELISAs), preliminary results suggest that 1.47X10-5 pg/nerve cord is being extracted. Partially purified nerve cord extracts, whole nerve cords and crude leech CNS extracts, were also sent to Dr. Lingjun Li at the University of Wisconsin-Madison for matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI-MS) analysis. Unfortunately, we were unable to sequence the vasopressin-like peptide from the partially purified SEC fractions due to a contamination problem. In addition, MALDI-MS sequencing from intact leech nerve cords or crude extracts were unsuccessful due to a large number of peaks.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Pasquini, Sarah Cecilia
- Description:
- Mediterranean-type ecosystems of southern California are exposed to atmospheric nitrogen deposition with some areas receiving 20-45 kg N ha-1 annually. Although nitrogen is a limiting nutrient to plant growth, most nitrogen deposition in southern California occurs as dry deposition when plants are physiologically inactive due to seasonal drought. Due to this inactivity, it is unclear whether or not plants can utilize the additional nitrogen. The effects of nitrogen fertilization on aboveground plant production were tested in coastal sage scrub and chaparral ecosystems, and the effects of nitrogen deposition on post-fire recovery were observed in chaparral ecosystems. I found that experimentally added nitrogen did not result in increased production in either coastal sage scrub or chaparral sites. The vegetation did absorb added nitrogen but did not allocate aboveground production. Chaparral ecosystems did not respond to nitrogen deposition with increased rates of total or shrub biomass production post-fire but did show low density of large shrubs at high nitrogen deposition sites and high density of small shrubs at low nitrogen deposition sites. Since vegetation absorbs nitrogen but does not allocate it to increased production, it is important to discover the fate of the nitrogen because nitrogen deposition is projected to increase in southern California in future years. Key words: disturbance, Mediterranean-type ecosystems, semi-arid ecosystems, Adenostoma fasciculatum, Ceanothus, air pollution
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Nguyen, Binh T
- Description:
- The aim of this study is to identify genes involved in calcification and coccolith production in Emiliania huxleyi using Suppressive Subtractive Hybridization (SSH) and microarray analysis techniques. Suppressive subtractive hybridization detected 168 differentially expressed transcripts in comparing lithforming cells grown in phosphate-limited (f/50) media and non-lith forming cells grown in phosphate-replete media (f/2). The SSH library of differentially expressed genes in lith-forming cells is comprised predominately of transcripts showing no significant matches to sequences in GenBank as a function of BLAST X homology searches. A number of transcripts from the SSH library of differentially expressed genes in non-lith forming cells showed significant homology to genes encoding ribosomal proteins and RNA polymerase subunits. To validate these differentially expressed genes, cDNA microarray analysis was employed. SSH library clones along with 188 cDNA clones previously identified as being differentially expressed by microarrays, were printed as targets on glass slides and hybridized to RNA probe molecules extracted from lith and non-lith forming cells. In this study, preliminary results indicated 80 differentially expressed genes (22.5%) out of a total of344 target clones. Among the 188 up/down regulated genes from previous microarray study, 59 genes were validated (31 %), and among 156 SSH differentially expressed genes 21 were validated (13.5%).
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Martus, Carolyn
- Description:
- The Mexican fan palm (Washingtonia robusta) is a non-native plant species which commonly grows in riparian communities throughout Southern California, but there is no documentation of the extent of its range or quantification of its specific impacts on biodiversity. Invasive plants are one of the leading causes of endangered species and riparian plant communities are critical for the recovery of these species. Mexican fan palms are common ornamental plants in this region so there is a continuous source of seed, but it is unknown how much of the spread of this species is due to increased plantings as opposed to natural recruitment of established trees. Additionally, runoff from storm drains may have altered hydrological conditions to the point that small tributaries that were previously too dry are now able to support palms. This study documents the extent of the Mexican fan palm's range in portions of the San Luis Rey River and Carlsbad watersheds and measures its impact on soil temperature and light availability. At both study sites, Mexican fan palms were more frequent within 100 m of the seed and freshwater source and able to survive 800 m away. Streams of all orders have the potential for invasion by Mexican fan palms if there is a direct source of freshwater and seed. Streams of lower order are at greater risk than higher order streams. Mexican fan palms impact the microclimate in riparian areas because they are more effective shaders and produce cooler soil temperatures and have less light available under their canopy than one native species, Quercus agrifolia. Keywords: Washingtonia robusta, invasive species, Southern California wetlands
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Knight, Crystel Lea
- Description:
- The Common Raven (Corvus corax) and the American Crow (Corvus brachyrhnchos) are both subsidized by anthropogenic resources. Two patterns of subsidized predation have been identified, spillover predation and hyperpredation, and spillover predation is likely to occur when predators use human-provided resources that are adjacent to natural habitats. In order to employ appropriate conservation strategies, it is important to understand the different predation patterns as these corvids do affect many threatened and/or endangered species. In this study crow and raven populations throughout the San Diego Zoological Society's Wild Animal Park were examined. Corvids are abundant there, often found in and around animal enclosures, where animal food and waste is present as well as where human provided resources are found. Corvid abundance declined with increasing distance to animal enclosures, but abundance was not affected by distance to public access areas. In contrast, attacks on artificial nests baited with both real and clay eggs did not significantly decrease with distance from either enclosures or public access areas. Furthermore, the number of ravens in the area did not help determine how long it would take for a nest to be attacked. It did, however, take longer for the ravens to find and attack nests that were far from both animal enclosures and public access areas, which suggests that spillover predation is occurring in the undeveloped habitat. Because spillover predation is occurring, it is possible that the ravens in the areas that are supported by anthropogenic resources could inhibit the growth of a prey population in the backcountry areas of the park. Key Words; spatial distribution, corvids, predation risk, crows, ravens, subsidized predators
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Jones, Letitia D
- Description:
- Two serial analyses of gene expression (SAGE) libraries of healthy and infectious hypodermal and hematopoietic necrosis virus (IHHNV) infected shrimp species, Litopenaeus stylirostris, were constructed to identify genes associated with immune response. Invertebrates rely on the innate immune system when under a pathogenesis attack due to the lack of an adaptive immune response. Therefore, we are interested in genes involved in innate immune defense. The healthy library had 287,139 total tags and the infected library had 300,858 tags. 2,839 tags were differentially expressed of which 2% of these tags mapped to immune related genes. Of these 2,839 tags 35% of these tags were unmatched. The major problem with SAGE tags is their short length which often leads to inability to match SAGE tags to specific genes in databases. In an effort to better understand the innate response, those unknown genes were addressed. Through the rapid amplification of complementary DNA ends (RACE) in the 3' and 5' direction, a portion ofthese genes were successfully extended and matched. In total, 61 immune related genes were identified through SAGE and 3' and 5' RACE. These immune related genes coded for proteins whose function includes antimicrobial peptides, apoptosis, stress response and phagocytosis. One of the most interesting genes identified was the gene that encodes for the protein, Tripartite Motif -Containing Protein 5 (TRIM5alpha). TRIMS alpha serves an important role in inhibiting viral infectivity. Keywords: SAGE, innate, shrimp, Litopenaeus stylirostris, TRIM
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Greco, Brian J
- Description:
- Little is known about the ways in which elephants solve novel foraging problems or how conspecifics may influence problem solving. However, anecdotal evidence suggests that social learning may play an important role in elephant behavioral ecology. In my thesis research I asked if learning is facilitated after viewing a conspecific's interactions with a novel task. Serving as the model, the most dominant female in an African elephant herd at the San Diego Zoo Safari Park learned how to extract food from each of six apparatus. Five subdominant females each interacted with three apparatus after watching the model; they also interacted with three other apparatus without having first watched the model (unmodeled condition). Contrary to my hypotheses, the elephants did not necessarily solve the task in the way the model solved it, nor did they solve it more quickly in the modeled condition, suggesting that the elephants did not engage in imitative social learning. However, the subjects spent 16% more time interacting with the novel apparatus in the modeled than in the unmodeled condition, and solve time was correlated with the focus time, a measure that was designed to reflect engagement in the task. These results suggest that in elephants, the efficiency of learning a novel task may be improved through the social enhancement of exploratory behavior. Future research should be directed towards the development of social learning methodologies that better suit elephants, and should place greater emphasis on non-imitative forms and mechanisms of social learning. Keywords: Elephants, African Elephants (Loxodonta africana africana), Social Learning, Non-Imitative Social Learning, Cognition
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Chuven, Justin
- Description:
- The main objective of this project was to develop a technique that can be used in field studies to increase the probability of locating dholes ( Cuon alpinus) in the wild. The dhole is an endangered canid, occupying a wide variety of habitats in southern and eastern Asia. Dholes have proven to be a very difficult species to locate and study in the wild; therefore, the current status in much of its range, its ecology, and habitat requirements are not well known. Currently, field researchers lack a reliable method for capturing dholes in the wild, and nearly all field studies to date have been primarily observational in nature. This study evaluated the response of Chinese dholes ( Cuon alpinus lepturus) to auditory playbacks employing a variety of vocalizations. The primary objective of this research was to determine a vocalization that would cause the dholes to approach the source of the sound. The subjects of this study were five captive dholes at the San Diego Wild Animal Park. The sounds used in playback can be divided into four different categories: dhole (unknown individuals), dOOle (known individuals), prey sounds, and control (white noise). The results of this study show the use of auditory playbacks may have implications for field conservation projects. All sounds used in playback elicited an approach response by at least one animal. The dhole whistle vocalization, specifically the unknown whistle, elicited the greatest relative approach response from the dholes in this study with two dholes approaching in four of four trials and one responding in three of four trials. KEYWORDS: Cuon a/pinus, vocal communication, playback, dhole, bioacoustics
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Cantor, Elvia M
- Description:
- Advances in molecular biology using different types of cells, vectors, and novel methods of DNA delivery, are paving the way for the development of reproducible bioprocesses that yield large amounts of recombinant proteins. A new mammalian cell expression technology has been applied in this study. The FreeStyle TM MAX Expression System offers the advantages of a completely animal origin-free, large-scale transient transfection system that produces high quantity recombinant proteins. Different combinations of plasmid DNAs and transfection reagents with FreeStyle TM CHO-S and FreeStyleTM 293-F cells were tested in order to identify the combination yielding optimal transfection efficiencies. The use of different culture systems, such as shake flasks, Wave Bioreactors, and Stir Tank Bioreactors, to analyze and compare the cell viability, transfection efficiencies, and expression levels using cultures at 1 liter, 1 0 liter, and 30 liter scales for FreeStyleTM CHO or FreeStyleTM 293-F cells. The results demonstrated that the system was able to achieve over 60% transfection efficiency for GFP expression and over 14 mg/L of human lgG production from 10 liter FreeStyleTM CHO-S cell cultures. In terms of yield, functionality, and fully modified proteins, these results suggest optimal production of proteins in FreeStyleTM CHO requires the use of the FreeStyle TM MAX transfection reagent.. Keywords: Transient expression, mammalian cells, liposome, transfection efficiency, recombinant protein, bioreactor, ELISA
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Brock, Bethany
- Description:
- The Pacific Pond Turtle (PPT), Actinemys (Clemmys) marmorata, is a small, highly aquatic turtle whose populations along its entire distribution range are in decline. As most of the published papers focus on the populations in the central and northern portions of the distribution range, the southern California PPT populations' demographics and overwintering ecology are not well-known or understood. A protected population of PTTs in Riverside County, California, was studied and the demographics of population size, survivorship and recapture probabilities, population structure, growth and sexual size dimorphism were analyzed. The overwintering ecology, including overwintering behaviors, timing and microhabitat characteristics of overwintering sites, of the same population were also studied using radiotelemetry. It was found that the southern California PPT population in 2008 contained approximately 120 individuals, had high adult female and juvenile survivorship rates, and lower than expected adult male survivorship rates. The population structure appeared to be that of a healthy, undisturbed population. The adult females were found to be significantly larger than the males. The PPTs exhibited terrestrial overwintering behavior as the seven turtles in the study all left the water to overwinter in upland locations. They utilized fewer locations than PPTs in northern populations and returned to the water earlier than northern PPTs. None of the study turtles were observed thermoregulating, as has been observed for all other PPT studies. The overwintering sites were located in a variety of habitat types. The knowledge gained from this study will help resource managers understand the population demographics and overwintering ecology of a robust southern California PPT population and utilize the knowledge to protect other PPT populations. Keywords: population size and structure, survivorship, sexual size dimorphism, overwintering, turtle, Pacific Pond Turtle
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Bowers, Robert M
- Description:
- The major goal of this study was to identify genes involved in the calcification and coccolithogenesis in the marine alga, Emiliania huxleyi using microarray analysis. Previous Suppressive Subtractive Hybridization (SSH) identified 168 differentially expressed transcripts between calcifying and non-calcifying cultures, and an earlier eDNA microarray analysis identified 188 differentially expressed genes using Expressed Sequence Tag's (EST's) as targets. To this point, E. huxleyi, strain 1516 has been used in all experiments, including the construction of both the SSH libraries and the EST libraries. The trigger for calcification had been phosphate stress. In strain 1516, calcification occurs in phosphate deplete media (1.67 [!M) and is inhibited in phosphate replete media (41.7 [!M). E. huxleyi, strain B39 recently was adopted in our lab as an experimental culture to compare to 1516 as it tends to calcify in phosphate replete media. A time course study was designed to compare gene expression profiles in a calcifying strain (B39) and a non-calcifying strain (1516) following the dissolution of calcite coccoliths with a dilute acid treatment. A eDNA microarray was constructed with a total of 368 elements printed in triplicate on glass slides. Target elements originated from both SSH and EST libraries. Total RNA was isolated from 12 L ofB39 cells and 12 L of 1516 cells. RNA was reverse transcribed and differentially labeled with Cy3 and Cy5 fluorescent dyes using Invotrogen's Superscript direct labeling system. Following the hybridizations, 60 genes were selected for further analysis based on exhibiting fluorescence intensities above two times the background fluorescence for at least two of the six time points. A repeated measures ANOV A was performed using these 60 clones to determine if there was an overall treatment effect over time. Of the 60 clones, 44 (73%) had a significant overall treatment effect. These 44 clones were then analyzed further using a factorial ANOVA to determine significant gene expression changes between time points of a single treatment.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Bernard, Chrystal L
- Description:
- Exotic plant invasion is a major environmental and ecological concern and is a particular issue for wetland ecosystems. I present statistical models that predict the locations of three exotic invasive plants (Arundo donax, Eucalyptus species (Eucalyptus globulus, Eucalyptus calmodulensis), and Tamarix ramosissima) that invade wetland areas throughout San Diego County based on their spectral signatures. I used three images that differed in their spectral resolutions and spectral coverage: Color-infrared (1m pixel size, infrared, blue and green bands), high resolution true color imagery (lm pixel size, red, blue and green bands), and hyperspectral Landsat imagery (30m pixel size, blue, green, red, near infrared, (2), mid infrared, and thermal infrared bands). For each invasive plant, three well-known multivariate statistical analyses, Discriminant Function Analysis (D.F.A.), Quadratic Discriminant Function Analysis (Q.D.F.A.), and CART, were used to identifY the models that best separated invasive plants from surrounding vegetation. A predictive accuracy analysis was preformed for each model by predicting which points should contain the invasive species based on their spectral values, then comparing these predictions to the actual presence or absence of the species. The best model for both Arundo and Eucalyptus species was obtained from the Q.D.F.A. using spectral values calculated from a combination ofNAIP and Landsat wavebands. CART using spectral values obtained from Landsat imagery produced the best results for Tamarix. Past studies show that plant species do in fact have distinct spectral signatures however; further investigation of classification techniques for this study is needed in order to create a more successful predictive model for each invasive plant species. Key-words: Discriminant Function Analysis, CART Model, hyperspectral imagery, invasive plants, predictive model, spectral signatures.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science
- Creator:
- Araji, Soha Ahmadzadeh
- Description:
- The polyphenol oxidase enzyme (PPO) is almost ubiquitous in Kingdom Plantae. PPO catalyzes the oxidation of phenolic compounds to quinones, which polymerize to form brown-colored phytomelanins. Although the physiological function of PPO in plants is unclear, recent studies have suggested that PPO has potential roles in seed coat coloration, pathogen resistance, and insect resistance. Walnut (Juglans regia) generates an exceptionally diverse group of phenolic compounds in leaf and hull tissues, but little is known about PPO in walnut. Recently, we cloned a single PPO-encoding gene from walnut and designated the gene jrPPOJ. In order to investigate the physiological function(s) of this walnut PPO, we constructed transgene vectors designed to either overexpress or silence jrPPOJ. Eight jrPPOJ-silenced transgenic walnut lines with PPO-activities :=::: 1% of wild type were identified, but none of the plants transformed with the jrPPOJ overexpression construct displayed elevated PPO activity. Using protein extracts from the leaves of wild-type and jrPPOJ-silenced walnuts, we identified the likely phenolic substrates for JrPPOl in planta and performed basic biochemical characterization of the enzyme. Preliminary studies suggest that PPO may play a role in defense against the causal agent of walnut blight, Xanthomonas campestris pv. juglandis, since this pathogen appears to replicate more rapidly in the leaves of jrPPOJ-silenced plants than in wild-type plants. PPO may also have an as-yet uncharacterized role in the control of cell death, since jrP PO ]-silenced lines exhibit a lesionmimic phenotype (necrotic leaf spots) whose severity increases over the course of the growing season. Keywords: Polyphenol Oxidase (PPO); Phenolic Compounds; Walnut (Juglans regia); Xanthomonas campestris; Enzyme.
- Resource Type:
- Thesis
- Campus Tesim:
- San Marcos
- Department:
- Biological Science