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Abstract

To study the evolution of developmental processes, we analyse vulva development in P. pacificus and compare it to C. elegans. In P. pacificus, 7 of the 12 ventral epidermal cells undergo apoptosis, whereas the corresponding cells in C. elegansfuse with the surrounding hypodermis. Phylogenetic analyses suggest that the cell death of these epidermal cells represents a derived character. To understand the evolutionary changes responsible for these evolutionary alterations in the apoptotic mechanism, we are characterising cell death mutants in P. pacificus. Genetic screens lead to the isolation of mutations in the cell death pathway in P. pacificus that result in the survival of P(1-4,9-11).p. Complementation tests have shown, that these mutants fall into two complementation groups, one of which has been proven to encode the P. pacificus ortholog of ced-3 (Sommer et al., 1998). The second complementation group had been originally characterized as ipa-2 (inhibitor of P-ectoblast apoptosis) and is a good candidate for the Ppa-ced-4homolog. We have mapped ipa-2 to chromosome III in the neighborhood of pal-1 and have isolated the BAC clone 7-E-22 by hybridization with a Ppa-pal-1probe. Sequencing this BAC clone indicated small-scale synteny to C.elegans in that region. However, we could not identify a ced-4 like molecule on that BAC. Further mapping placed ipa-2 between the two SNP markers S55 and tra-1, which are adjacent to the pal-1 locus. Further fine mapping is in progress to clone ipa-2by BAC walking.