Worm Breeder's Gazette 1(1): 11
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.
Following methods similar to those described by Hirsh and Vanderslice (1976), we have isolated more than 100 ethyl methane sulfonate induced temperature sensitive (TS) mutants. All these mutants propagate at 20 C (permissive temperature) and do not propagate at 25 C (nonpermissive temperature). These mutants fall into four broad classes: 1) mutants blocked in embryogenesis (over 30 mutants); 2) mutants blocked in fertilization (nearly 30 mutants); 3) mutants defective in gonadogenesis (over 30 mutants); 4) mutants accumulating in one of the postembryonic larval stages (over a dozen mutants). From this pool of mutants, we have chosen to analyze those mutants that are blocked in fertilization and those that are blocked in embryogenesis. Of the 30 or more embryonic mutants that we have examined, mutants are found which produce embryos blocked in the 1-2, 12-16, 20-30, 40- 60, and 100-150 cell stages. Twelve mutants which we have tested so far lay embryos that appear to be uniformly blocked in one particular cell stage at restrictive temperature. Their phenotype is recessive to wild type. From temperature shift experiments, we have found that the temperature sensitive period in the mutants varied from the first larval stage to the adult animal. We have also asked whether the embryonic defects of these mutants show a maternal effect. Our criteria for maternal effect is the same as that described by Vanderslice and Hirsh (1976). 1) When a homozygous TS/TS hermaphrodite is mated at nonpermissive temperature with wild-type males (+/+), no viable progeny should be produced. 2) When a heterozygous hermaphrodite (+/TS) is grown at the nonpermissive temperature for the TS mutation, one fourth of the progeny produced should be homozygous for the TS mutation. A dozen embryonic mutants blocked in the 1-2, 12-16, 20-30, 40-60, and 100-150 cell stages have been characterized. We have found they all exhibit a maternal effect. Two mutants that die after the 150 cell stage may not show a maternal effect. Since the spectrum of the mutants that we tested probably represents the general developmental stages of the worm and since all mutants so far tested exhibited maternal effect, one can conclude that maternal genome plays a major role in the embryonic development of C. elegans at least through the 150 cell stage.