mRNA Translation and Germline Evolution in Caenorhabditis

University Of Maryland, College Park, College Park MD

Investigators

Abstract

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.