Worm Breeder's Gazette 14(4): 41 (October 1, 1996)
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.
MPI fuer Entwicklungsbiologie, Abteilung Zellbiologie, Spemannstrasse 35, 72076 Tuebingen, Germany
We have analyzed two previously isolated strains of Pristionchus pacificus for the occurrence of restriction fragment length polymorphisms. 14 of 17 randomly choosen cDNA clones give polymorphisms after hybridization to EcoRI digested genomic DNA of the populations from southern California and Washington State. This polymorphism is much higher as polymorphism found among different strains in C. elegans (Emmons et al., PNAS 76, 1333ff.). Two different scenarios could account for the observed RFLPs. First, the polymorphisms could be caused by an active transposon. Second, the two populations could be separated from one another for a long time. In order to distinguish between these two possibilities, we have started to compare most of the nucleotide sequence of the previously cloned Ppa-let-60/ras gene. Several nucleotide substitutions at third codon positions have been observed in the coding region betwen the two populations. None of these substitutions results in an aminoacid replacement. Within the intron sequences, four nucleotide substitutions as well as the deletion of three nucleotides (at two positions), have been observed. This high level of sequence diversity gives a first indication for a long evolutionary separation time of the two populations. This issue is analyzed further by sequence analysis. Nonetheless, animals of both populations can be crossed. The use of mutant animals in these crosses indicates that the F1 progeny (California/Washington) is completely fertile. These results suggest that the observed RFLPs are useful as molecular markers for chromosomal walking procedures. We have also tested, if an active transposon is present in any of the two populations. The mutant Ppa-unc-1(sy306) has a small diameter and the body muscles twitch constantly. Mutants with this phenotype have been isolated at high frequency, suggesting that the mutation causing this phenotype is a mutation in a gene homologous to the unc-22 gene of C. elegans. We have used protocols to isolate spontaneous twitcher-mutants, without being succesful to date.