We are studying the evolution of developmental processes by comparing vulva development between C. elegans and Pristionchus pacificus . In P. pacificus , seven of the twelve ventral epidermal cells undergo programmed cell death during late embryogenesis. We have previously shown that mutations in the
ced-3 homolog of P. pacificus prevent apoptosis of P(1-4,9-11).p and that
Ppa-ced-3 mutants suppress the vulvaless phenotype of the homeotic gene
Ppa-lin-39 . We have used other genetic screens to isolate new components of the cell death machinery in the ventral epidermis: in a Nomarski F2 screen, we have isolated two mutations that block programmed cell death, like
Ppa-ced-3 . Complementation tests revealed these two mutations to be allelic to each other, but not allelic to
Ppa-ced-3 . We are currently testing the hypothesis that these mutations, originally called
Ppa-ipa-2 , correspond to the
Ppa-ced-4 gene. To clone the
ced-4 homolog of P. pacificus we want to use the syntenic organization of the C. elegans and P. pacificus genome, that has been shown to be present in at least some areas of the genome.
Cel-ced-4 is closely linked (appr. 40 kb) to
Cel-pal-1 . We have cloned the
Ppa-pal-1 by polymerase chain reaction and have isolated a genomic Lambda clone of this gene. We are now using a chromosomal walking strategy to find
Ppa-ced-4 . In addition, we are using new genetic strategies to isolate more cell death defective mutants in P. pacificus .