Thesis

Identification of DNA Sequences Potentially Responsible for Chalcone Resistance in Caenorhabditis Elegans ssing an Ethyl Methanesulfonate-Based Deep Sequencing Mapping Approach

Chalcones are aromatic ketones that form the central core for a variety of important biological compounds. Previous research in Dr. Calderón-Urrea’s laboratory showed the efficacy of eight chalcones (1, 16, 17, 18, 19, 22, 25, and 30) to kill Caenorhabditis elegans. The chalcones cause 100% mortality, not only in C. elegans but also the plant parasitic nematode Meloidogyne incognita, at concentrations of 10-4 M (Singh, 2013). Furthermore, chalcones 17, 25, and 30 effectively kill at even lower concentrations (10-5 M). However, the mechanism by which the chalcones kill the nematodes is not known. Previous work, also from Dr. Calderón-Urrea’s laboratory, identified a mutant in the C. elegans strain PD4251 that is resistance to Chalcone 17, and this new mutant strain was named strain RT-Ch17.1.2. Here we set out to identify the DNA sequence responsible for the mutant phenotype of strain RT-Ch17.1.2 using a combination of genetics, whole genome sequencing (WGS), and bioinformatics tools. I identified six single nucleotide polymorphisms (SNPs), corresponding to two genes; these two genes are therefore candidates involved in resistance of RT-Ch17.1.2 to chalcone 17. These two genes are the mitochondrial ribosomal protein large subunit (mrlp-15), and a 5'-to-3' DNA helicase (pif-1). Both of these genes play a role in the proper functioning of the mitochondria, which suggest that the chalcones may target essential elements of the mitochondria to cause lethality in the nematodes.

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