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Abstract:
The detailed understanding of Caenorhabditis elegans biology and particularly its developmental biology makes nematodes an attractive group of organisms for comparative evolutionary studies. More specifically, development of the vulva, the egg-laying struc- ture of nematode females and hermaphrodites, has been studied in great detail. Since developmental processes can be analyzed at the cellular, the genetic, and the molecular levels, the comparative analysis of nematode vulva development can serve as a case study in evolutionary developmental biology. In Pristionchus pacificus, vulva formation differs from C. elegans with respect to (i) the mechanism of vulva induction, (ii) the evolution of a new signaling center in the posterior body region, and (iii) the fate of nonvulval epidermal cells. More than 100 vulva-defective mutants have been isolated in P. pacificus over the years. To allow cloning of the corresponding genes, a genomic approach has been used, generating a genetic linkage map and a physical map of the P. pacificus genome. The genetic and molecular analysis of vulva development now indicates that some vulva genes show conservation and change of function simultaneously; that is, they have functions that are conserved while other functions clearly differ between the two species. Other genes are only involved in vulva development in one but not the other species. Thus, the molecular, genetic, and cellular processes can change dramatically during evolution, even when the developmental structure under consideration is homologous between species.
