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.

RFLPs in Pristionchus pacificus populations.

Isabel Schlak, Ralf J. Sommer

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.