To study the evolution of developmental processes we compare vulva development between the nematodes Caenorhabditis elegans (Rhabditidae) and Pristionchus pacificus (Diplogastridae), which shared a last common ancestor around 300 million years ago. In C. elegans, the EGF/RAS/MAPK-pathway is involved in vulva induction. In contrast, it is not clear whether EGF- or other signalling pathways are required to induce vulva development in P. pacificus. In genetic screens for vulva defective phenotypes, P. pacificus mutations in the
lin-17/Frz-gene were isolated (Zheng, Roeseler and Sommer, see contribution to this meeting). This result suggests that Wnt-signalling is one of the signalling pathways necessary for vulva development in P. pacificus.Using degenerate primers, we cloned several possible downstream interactors of the WNT-signalling pathway. For further investigation of these genes, we are taking two different approaches. First, we started to analyze the function of
mig-5/Dsh,
apr-1/APC and
pop-1/TCF by Morpholino knockdown experiments. We observed an increase in frequency of bivulva phenotype after injection of
mig-5 Morpholino in a sensitized background. Second, we are investigating proteins that might interact with POP-1 using yeast two-hybrid screens. With this approach we expect to find more components involved in Wnt signal transduction in P. pacificus. These experiments might provide insight into the molecular evolution of vulva induction resulting in different patterns such as those found in P. pacificus and C. elegans.