Hermaphroditism (sperm production in the XX ovotestis) is one of the traits that has made C. elegans such a powerful genetic model, but most species in the genus have a male/female mating system. The genetic pathway used to determine somatic and germline sex in C. elegans is well understood; however the genes in the pathway are poorly conserved within Caenorhabditis. We have been interested in how sex determination, a rapidly evolving process in Caenorhabditis, can provide insights into how biological pathways can be modified from a common set of ancestral genes to provide novel traits, such as the XX hermaphrodite. Previous work from our lab and the Haag lab has shown that the control of sperm production in a female gonad is different in C. briggsae as compared to C. elegans. fem mutants in C. elegans result in XX and XO females, while in C. briggsae both XX and XO fem mutants are hermaphrodites.We have now extended that work, by isolating and characterizing suppressors of
Cb-tra-2 ts mutations, in hope of identifying missense mutations which will help with the analysis of Fem protein function. Over 70
tra-2 suppressors were identified in the Pilgrim and Haag labs by looking for the restoration of self-fertility to tra(ts) animals at the restrictive temperature. As expected, most of these lie in the Cb-fem genes, however some represent novel phenotypes/alleles not previously observed in either system. I will present the current understanding of the C. briggsae sex determination pathway and how this differs from C. elegans. Additionally, I will discuss how comparative genomics within the Caenorhabditis species may provide us with clues to the relationship between molecular changes and the evolution of novel traits. .