Item

Abstract

The nematode Pristionchus pacificus has been established as a model system in evolutionary developmental biology and evolutionary ecology. Previous studies focused on macroevolutionary differences between the reference strains of P. pacificus (PS312) and Caenorhabditis elegans (N2). To add a microevolutionary perspective to the evo-devo studies in P. pacificus, we isolated more than 150 different strains of the species from around the world and examined natural variation. These strains showed high diversity, both at the molecular and the phenotypic level. One of the observed variations involves development of the vulva specifically due to induction by the gonad. The vulva (the egg laying organ of nematodes) develops from three vulva precursor cells (VPCs). In PS312 differentiation of the VPCs depends on a continuous and redundant Wnt signal from the somatic gonad and the posterior of the animal. However in some of the P. pacificus strains, VPCs were still able to differentiate after ablation of the gonad. To identify the involved loci we crossed the two isolates showing the most extreme phenotypes. We obtained recombinant inbred lines (RILs) by selfing individual F2 and near isogenic lines (NILs) by continuously backcrossing the RILs to PS312 animals. Gonad ablation experiments and genotyping of more than 200 RILs revealed a 430kb region on Chromosome I associated with the VPC differentiation trait. Currently we are testing a candidate gene in this interval by transgenesis experiments. Together, the microevolutionary perspective of P. pacificus vulva development is an effort to integrate evo-devo studies in evolutionary theory.