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Zusammenfassung:
We are studying the evolution of cell fate specification, using vulva development as a model system. Comparative analysis between C. elegans and Pristionchus pacificus revealed that the specification of the vulva is highly diverse at the cellular level between these two nematodes. Vulva formation in P. pacificus, for instance, depends on continuous gonadal induction by multiple cells, whereas in C. elegans the single anchor cell is sufficient for inducing the vulva. Mutagenesis experiments in P. pacificus identified four classes of vulvaless mutants. Besides generation and induction vulvaless mutants, two classes of mutants show defects restricted to the 2° and 1° cell fate, respectively. Two strong induction vulvaless mutants were isolated, namely vul-1 and vul-2. Cell lineage analysis indicates that vul-1 mutant animals can be defective in the specification at P (5-7).p. In some animals, only one vulval precursor cell undergoes vulva differentiation, adopting a 1° or 2° cell fate depending on its position. Mutations in vul-2 affect P (5, 7).p more severely than P6.p. Linkage analyses using genetic and molecular markers revealed that these two mutants are on P. pacificus chromosome IV. Fine mapping of vul-1 reveals that this mutation is closely linked to the SNP marker S181. Positional cloning is currently in progress.
