Meeting Abstract
S1-2.4 Thursday, Jan. 3 Evolution of the gene regulatory network underlying sexual differentiation in turtles with alternative sex determining mechanisms NICOLE, Valenzuela; Iowa State University nvalenzu@iastate.edu
The evolution of sex determining mechanisms has fascinated biologists and laymen alike. Sex determination has paramount consequences for the evolution of a multitude of traits, from sex allocation to speciation and extinction. Yet the evolution of sex determination in vertebrates remains an enigma, partly because the functional mechanics (ecological and molecular) of alternative sex-determining mechanisms in closely related taxa are not fully known (TSD or temperature-dependent, and GSD or genotypic). Here I will focus on the following pending questions. (1) What renders TSD systems thermo-sensitive? (2) Is there one developmentally-conserved TSD mechanism, or have multiple TSD molecular pathways evolved to produce ecologically equivalent outcomes? (3) Have derived GSD species lost all ancestral thermal-sensitivity? These questions are addressed using gene expression analyses in Chrysemys picta (TSD) and Apalone mutica (GSD) turtles. Results pinpoint at some conserved elements of the sexual differentiation pathways (Wt1, Sf1) as potential master thermal switches that bestow thermal-sensitivity to vertebrate sexual differentiation. Additionally, a candidate sex-determining gene for A. mutica is proposed based on these data (Sf1). Analyses reveal significant divergence in gene expression within and among TSD and GSD sex determining mechanisms. Finally, my findings show that GSD species derived from TSD ancestors can retain a relic thermal sensitivity in gene expression (Wt1) over evolutionary time. This novel finding reveals an undocumented source of raw material for future evolutionary change that may exist in other GSD taxa, and one that enhances the evolutionary potential of the gene networks underlying sexual differentiation and contributes to the astonishing lability of sex-determining mechanisms.
