Genome Repatterning Underlying the Co-evolution of Diploid Number and Gender Determination in Turtles

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Gender is determined by genetic constitution in most animals (as by sex XX/XY chromosomes in humans, or ZZ/ZW in birds), and by environmental temperature (TSD) in others, including turtles. Notably, turtle lineages that underwent a transition in the gender-determining mechanism show a 20-fold increase in the rate of evolution of chromosome number, but it is unclear why or how these traits are associated. This project represents the first step to elucidate the functional link between these two traits by testing the hypothesis that chromosomal rearrangements disrupt the location and consequently the regulation of genes controlling sexual development, which in turn cause the transition between gender-determining mechanisms among turtles. By combining molecular cytogenetics, transcriptomics, bioinformatics and phylogenetic analyses, this project will reconstruct the organization of the ancestral turtle genome; characterize the chromosomal rearrangements that have taken place among turtles over 210 million years of turtle evolution; and build mechanistic hypotheses about the critical elements in the regulatory network of sexual development that underlie transitions in gender-determining mechanisms in turtles for further study. This project proposes a novel hypothesis about the relationship of genome evolution over large spans of time and gender determination, which if true, could transform our understanding of the mechanism by which gender determination evolves.Broader ImpactsThe educational activities of this project will help integrate undergraduate discovery-based learning and broaden the participation of underrepresented groups in biology by training students and their mentors; by engaging women and minorities through outreach activities; and by strengthening the PI's qualifications as role model for underrepresented groups.