NSF PRFB FY 2023: Investigating proximate mechanisms and ultimate drivers of temperature-dependent development of male:female ratios in reptiles

该行动资助了美国国家科学基金会2023财年生物学博士后研究奖学金，研究基因组，环境和表型之间相互作用的生命规则的综合研究。该奖学金支持将以创新方式对生活规则领域作出贡献的研究员的研究和培训。在许多爬行动物中，个体发育为雄性还是雌性取决于它们在卵内发育时所经历的温度。了解这一过程的生物学机制日益紧迫，因为气候变暖可能会在个人和种群水平上影响这些过程。尽管这种发育系统自20世纪60年代以来就被研究过，但我们仍然对温度究竟如何影响这些物种的发育和生存知之甚少。1)相同的温度如何在不同的物种中产生相反的结果，2)卵子发育过程中所经历的温度如何影响存活的概率，这些仍然未知。这项研究将直接促进我们对雄性和雌性爬行动物发育调节机制的理解，并将为针对脆弱种群和物种的保护工作提供信息。该研究员将接受基因组技术和建模方面的培训，并将通过向经济落后地区的当地学校展示研究成果，扩大对科学的参与。雌性或雄性表型的温度依赖性代表了发育可塑性的一个简单例子，在这个例子中，在离散的发育窗口期间经历的温度决定了这种发育。尽管对类似的热信号的分子和遗传反应似乎是保守的，但由此产生的发育结果在物种之间是不同的。例如，低温会导致红耳滑龟（Trachemys scripta）和美洲鳄（Alligator mississippi）保守的染色质修饰因子上调，但低温会导致红耳滑龟（T. scripta）产生雄性，而密西西比鳄（A. mississippi）产生雌性。本研究的第一个目标将使用ChIP-seq和ATAC-seq方法来检验染色质修饰因子与海龟和鳄鱼基因组中不同遗传位点相互作用以产生物种特异性反应规范的假设。其次，最近的理论和实证数据支持了孵化温度对雄性和雌性存活到成熟的影响，这是发育可塑性的适应价值的基础。本研究的第二个目标是通过在实验室中不同的波动温度下孵化密西西比南鳄（A. mississippi）卵后的再捕获努力，研究日益温暖的气候将如何影响鳄鱼的雌雄比例、随之而来的种群结构，并最终确定这种温度依赖的发育可塑性的适应价值。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This action funds an NSF Postdoctoral Research Fellowship in Biology for FY 2023, Integrative Research Investigating the Rules of Life Governing Interactions Between Genomes, Environment, and Phenotypes. The fellowship supports research and training of the fellow that will contribute to the area of Rules of Life in innovative ways. In many reptiles, whether an individual develops as a male or a female depends upon the temperatures that they experienced while developing inside the egg. There is increased urgency to understand the biological mechanisms of this process, as a warming climate will likely influence these processes at both individual and population levels. Even though this developmental system has been studied since the 1960s, we still know very little about how exactly temperature influences this development and the survival of these species. It remains unknown 1) how the same temperature produces opposite outcomes across different species and 2) how temperatures experienced while developing in the egg affect the probability of survival. This research will directly advance our understanding of mechanisms regulating the development of male and female reptiles and will inform conservation efforts aimed at vulnerable populations and species. The fellow will be trained in genomic techniques and modeling and will also broaden participation in science by presenting the research to local schools in an economically disadvantaged area. The temperature-dependence of female or male phenotype represents a straightforward case of developmental plasticity, in which the temperature experienced during discrete developmental windows dictates this development. Whereas the molecular and genetic responses to similar thermal cues appear to be conserved, the resultant developmental outcomes vary across species. For example, cool temperatures lead to the upregulation of conserved chromatin modifiers in the red-eared slider turtle (Trachemys scripta) and the American Alligator (Alligator mississippiensis), but these temperatures produce males in T. scripta and females in A. mississippiensis. The first objective of this research will use ChIP-seq and ATAC-seq approaches to test the hypothesis that chromatin modifiers interact with different genetic loci across the turtle and crocodilian genome to produce species-specific reaction norms. Second, recent theoretical and empirical data support the idea that incubation temperature-mediated effects on male vs female survival to maturity underlie the adaptive value of developmental plasticity. Using recapture efforts after incubating A. mississippiensis eggs in the lab at different fluctuating temperatures representing future warming scenarios, the second objective of this research is aimed at addressing how increasingly warm climates will affect crocodilian male: female ratios, attendant population structures, and, ultimately the adaptive value of this temperature-dependent developmental plasticity.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.