mRNA Translation and Germline Evolution in Caenorhabditis

进化生物学的一个重大挑战是理解新的解剖特征是如何在不破坏整体发展一致性的情况下出现的。因为许多控制发育的基因是广泛保守的，所以这个过程必须混合古老的成分和新的特征，比如物种特异性基因或基因之间的调节联系。本研究考察了在线虫中反复进化的一种重要的生态学新现象——自育雌雄同体。自我生育进化的关键一步是雌性蠕虫产生有限数量精子的能力，这使它们变成了雌雄同体。雌雄同体精子的产生受存在于生殖细胞（配子的前体）中的信使rna结合蛋白（rbp）的调节。其中一种rbp， GLD-1，是一种古老的，进化缓慢的蛋白质，可以调节数百种目标mrna。GLD-1在秀丽隐杆线虫（C. elegans）和秀丽隐杆线虫（C. briggsae）两种不同物种的雌雄同体生殖系性别决定中被独立利用。然而，在秀丽隐杆线虫中，GLD-1促进精子命运，而在秀丽隐杆线虫中，GLD-1抑制精子命运。这种矛盾可以通过GLD-1蛋白辅助因子的物种特异性进化和GLD-1结合的mRNA分子序列的变化来解释。该项目将与几个隐杆线虫物种合作，系统地研究辅助因子和mRNA序列的变化如何改变GLD-1活性的背景，从而允许出现新的生殖策略。更广泛地说，这项研究将有助于揭示旧分子如何发挥新作用，从而将生物组织的分子和有机体尺度上的进化联系起来。我们将利用这个项目帮助当地的高中教师了解科学研究的兴奋，以便他们将这些课程传达给他们的班级。

One of the grand challenges of evolutionary biology is to understand how new anatomical features emerge without disrupting the overall coherence of development. Because many genes that control development are widely conserved, the process must blend both ancient components and new features, such as species-specific genes or regulatory connections between genes. This research examines an ecologically important novelty that has evolved repeatedly in Caenorhabditis nematodes--self-fertile hermaphroditism. A key step in the evolution of self-fertility was the ability of otherwise female worms to produce a limited number of sperm, which turned them into hermaphrodites. Hermaphrodite sperm production is regulated by messenger RNA-binding proteins (RBPs) present in the germ cells (the precursors of gametes). One of these RBPs, GLD-1, is an ancient, slow-evolving protein that regulates hundreds of target mRNAs. GLD-1 was coopted into hermaphrodite germ line sex determination independently in two different species, C. elegans and C. briggsae. However, in C. elegans GLD-1 promotes sperm fate, whereas in C. briggsae GLD-1 represses it. This paradox is explained by the species-specific evolution of GLD-1 protein cofactors and by changes in the sequences of the mRNA molecules that GLD-1 binds. This project will work with several Caenorhabditis species to systematically examine how both cofactors and mRNA sequence changes alter the context of GLD-1 activity to allow the emergence of a new reproductive strategy. More generally, this research will help reveal how old molecules can take on new roles, thereby linking evolution at the molecular and organismal scales of biological organization. We will use this project to help local high school teachers understand the excitment of scientific research so they can convey these lessons to their classes.