Microarray analysis of Emiliania huxleyi under conditions that promote coccolithogenesis
Emiliania huxleyi, a unicellular marine alga, is notably recognized for its ability to form calcium carbonate structures known as coccoliths via a process referred to as coccolithogenesis. While E. huxleyi is a model organism among the coccolithophorids, few studies have used molecular techniques to address the biology of this globally important alga. There is little information known about the genome of this organism, and essentially no information on the genes and proteins involved in coccolithogenesis. In this study, microarrays of a selected set of 2,298 characterized cDNA clones were competitively hybridized with the goal of identifying genes whose expression ratio was significantly different under conditions inhibiting or promoting coccolithogenesis. Analysis often independent hybridizations identified 183 differentially expressed cDNAs, 121 of which were up-regulated and 62 were downregulated. Based upon EST analysis, functions for a number of these transcripts were hypothesized including vacuolar processing, anion diffusion, and sulfite oxidation. This is the first report describing gene expression patterns in a marine coccolithophorid under calcifying growth conditions, and provides a foundation for more detailed molecular genetic analysis of coccolithogenesis in E. huxleyi. Experiments are in progress to obtain full-length sequences of differentially expressed genes and to employ real-time PCR to quantitate their expression levels.