mRNA Translation and Germline Evolution in Caenorhabditis

进化生物学的重大挑战之一是理解新的解剖特征是如何在不破坏发育的整体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，这个过程必须融合古老的成分和新的特征，例如物种特有的基因或基因之间的调控联系。这项研究考察了一种在线虫中反复进化的生态上重要的新奇现象--自育两性。自我繁殖进化的关键一步是雌虫产生有限数量的精子的能力，这将它们变成两性。两性精子的产生受生殖细胞(配子的前体)中存在的信使RNA结合蛋白(RBPs)的调节。其中一种限制性商业惯例，GLD-1，是一种古老的、进化缓慢的蛋白质，调节着数百个靶向mRNAs。将GLD-1分别加入到两个不同物种的两性生殖系的性别决定中。然而，在秀丽线虫中，GLD-1促进精子命运，而在布里奇萨线虫中，GLD-1抑制精子命运。这一悖论可以通过GLD-1蛋白辅因子的物种特异性进化以及GLD-1结合的mRNA分子序列的变化来解释。该项目将与几个线虫物种合作，系统地研究辅助因子和信使核糖核酸序列的变化如何改变GLD-1活动的背景，以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承担新的角色，从而将生物组织的分子和组织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理解科学研究的兴奋之处，以便他们能够将这些课程传达到他们的课堂上。

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.