Affiliations: 1) Auburn University; 2) University of Alabama at Huntsville
Keywords: b. meiosis; j. epigenetics
Changes in the environment affect organisms in several aspects including the cellular, population, and ecosystem levels. At higher levels, populations are affected by changes in fecundity and longevity, whereas at molecular levels organisms can be impacted at the genetic level leading to heritable variation if changes are in the germline. Genomic instability results from the increased stress response in multiple pathways, including during meiosis, regulation of chromatin, and DNA repair. In this study, the primary aim was to investigate mechanisms of genomic instability by assessing the relationships between chromatin availability, DNA damage, and differential gene expression. Two species were used to compare, the model system (Drosophila melanogaster, DMEL) to a species (Drosophila pseudoobscura, DPSE) that is more vulnerable to changes in environmental temperatures. Species-specific treatment crosses were set up at appropriate temperature ranges (standard vs high temperature), early and late meiotic stages were compared by assessing ovaries dissected from females before and after the first mature eggs developed. RNA from the ovaries was used to assay differential gene expression, pinpointing expression differences during early and late phases of meiotic events of pachytene checkpoint, double-strand break formation, and eggshell chorion assembly. Moreover, the ovaries were used to assay apoptosis to measure the DNA damage using DAPI staining to observe the effect of heat stress. Lastly, nuclei from ovaries were extracted to generate ATAC-seq libraries to investigate changes in chromatin availability in each treatment and time point. Results from this study allow for the comparison between species with different thermal tolerances and provide a mechanistic explanation of the relationship between stress response and genomic instability in the context of meiotic recombination.