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Abstract:
We compare vulva development between Caenorhabditis elegans and Pristionchus pacificus to study the evolution of developmental processes. Cell fate specification during vulva development differs in these two nematodes. In C.elegans, P8.p is part of the vulva equivalence group and adopts a 3° fate under wild-type conditions. In contrast, several experiments indicate that P8.p in P.pacificus represents a new cell type. First, P8.p is unable to respond to an inductive signal from the gonad and fuses with the epidermis, but can respond to lateral signal from P6.p and form vulval tissue. Second, P8.p provides a lateral inhibitory signal that prevents P5.p and P7.p to adopt a 1° fate. Third, P8.p provides a negative signal that inhibits gonad-independent vulva formation of P(5-7).p. To study P8.p specification we screened for mutants with P8.p specification defects and identified three candidate mutants in which P8.p behaves like a normal VPC. In one of the mutants, named tu151, the nucleus of P8.p has an abnormal size. Cell ablation experiments in tu151 revealed that P8.p is able to respond to the inductive signal from the gonad to form vulval tissue. Also, P8.p in this mutant cannot provide the lateral inhibitory signal so that after P6.p ablation, P5.p and P7.p can adopt the 1° fate. In addtion, P8.p loses the function of providing negative signal in tu151 mutant animals since gonad-independent vulva formation occurs. Positional cloning of tu151 is currently in progress.
