Meeting Abstract
Developmental mechanisms often remain stable despite changes in the architecture of underlying gene regulatory networks (GRNs). This evolutionary process is termed developmental systems drift. We explore developmental drift through comparisons of tunicate GRNs, including the recently assembled genomes of Corella inflata and Boltenia Villosa along with that of the well-characterized model organism, Ciona robusta. We have begun to deploy this comparative analysis to examine changes in the regulatory elements for three different neural genes (Otx, DMRT, and Foxc). Despite any discernable sequence conservation, regulatory elements for the Corella Inflata orthologs to these genes are capable of driving neural expression in Ciona embryos. These Corella elements contain binding motifs for upstream trans-factors (Ets and GATA) characterized in Ciona. This preliminary data suggests that drift has occurred in the arrangement of binding sites while upstream trans-factor inputs have remained constrained. However further testing is required to determine whether these candidate sites are required for regulation of neural gene expression in Corella. We have also identified regulatory elements for Boltenia orthologs of two of these neural genes (DMRT and Otx) along with three cardiac progenitor lineage genes (Mesp, FoxF and Hand-like). Corella and Ciona are much more closely related to each other then they are to Boltenia villosa. Thus, comparisons between all three species will help to address questions about the rate and nature of developmental drift across different levels of divergence.
