Worm Breeder's Gazette 13(5): 19 (February 1, 1995)
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
HHMI & California Institute of Technology, Division of Biology 156-29, Pasadena, CA
Vulva development in Pristionchus is different from Caenorhabditis with respect to early and late specification events (WBG, 13, 107). Most dramatic is the reduction of the number of P-ectoblasts in the central body region to four, P(5-8).p. Although P(5-7).p form the vulva with a lineage very similar to Caenorhabditis, a major difference is the fact that P8.p is not a VPC. To get a better understanding of the processes leading to this presumably highly derived character state, we started genetic analysis in this species. Furthermore, we wanted to see what kind of phenotypes can be found in a genetic F2 screen standard to Caenorhabditis. The generation time of Pristionchus is 3 days at 20¡ C; the average number of progeny is 200. Males can be obtained with a frequency of 50 per plate under starving conditions (mass transfer of worms from plate to plate). We screened approx. 6600 genomes in a standard F2 screen, looking for morphological mutations. We identified 20 mutations with an Unc phenotype, 21 mutations with a Dpy phenotype, l mutation with a Rol phenotype and 99 mutations with an Egl phenotype, and backcrossed them. All mutants except for most of the Egl mutants are in permanent culture. Except for one case we cannot correlate these mutants to specific mutants in Caenorhabditis. Concerning the Caenorhabditis unc-22 gene, we observed a mutant in Pristionchus, called unc-l, that has the same twitching phenotype as unc-22. Furthermore, mutants with this phenotype were observed with a very high frequency, consistent with the molecular characterization of unc-22. We observed ca. 25 mutants with the twitching phenotype in this screen of 6600 gametes. Our primary interest was in the Egl mutants which could include phenotypes with an altered specification of the ventral cord ectoblasts. Nomarski analysis of Egl mutants after backcrossing revealed four vulvaless mutations: P(5-8).p do not divide in these mutants, thus they resemble the phenotype of gonad ablated wild-type animals. More surprising was the finding of 12 mutants where the number of P-ectoblasts in the ventral cord is altered in comparison to wild-type. Some mutants cause a reduction, others cause an increase in the number of P-ectoblasts. We call these Ped mutants for P-Ectoblast Determination mutants. They will be described, together with the corresponding cell ablation experiments, in the next WBG.....