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

在大多数动物中，性别是由遗传构成决定的(人类的性别是XX/XY染色体，鸟类的性别是ZZ/ZW)，其他动物的性别是由环境温度(TSD)决定的，包括海龟。值得注意的是，经历了性别决定机制转变的海龟血统显示，染色体数量的进化速度增加了20倍，但尚不清楚这些特征为什么或如何相关。这个项目是阐明这两个特征之间功能联系的第一步，通过测试染色体重排扰乱位置的假设，从而破坏控制性发育的基因的调节，这反过来又导致海龟性别决定机制之间的转换。通过结合分子细胞遗传学、转录学、生物信息学和系统发育分析，该项目将重建祖先海龟基因组的组织；描述海龟在2.1亿年的进化过程中发生的染色体重排；并建立关于性发育调控网络中的关键元素的机械假说，这些网络是海龟性别决定机制转变的基础，以便进一步研究。这个项目提出了一个新的假说，关于大跨度时间跨度的基因组进化和性别决定的关系，如果这是真的，可能会改变我们对性别决定进化机制的理解。广泛影响这个项目的教育活动将通过培训学生和他们的导师，通过扩大活动吸引妇女和少数族裔，并通过加强PI作为代表不足群体的榜样的资格，帮助整合基于发现的学习，并扩大代表不足群体在生物学方面的参与。

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.