Worm Breeder's Gazette 2(2): 8
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.
The temperature-sensitive mutant ts L 48 was obtained in the F3 progeny of worms of the Bergerac strain (NIGON 1949) mutagenized at the fourth larval stage with EMS, 0.5 M. This mutant develops with wild behavior and wild size at 17 C (the permissive temperature), but displays roller and dumpy phenotypes when grown at 22 C. At this restrictive temperature, ts L 48 rotates only to the left. MODE OF INHERITANCE Genetic studies prove that ts L 48 carries a single autosomal recessive mutation (or two very linked mutations without detectable recombination). The fact that a single pleitropic mutation can lead to both roller and dumpy phenotypes was already observed in C. elegans, Bristol, by BRENNER (1974), with non-temperature-sensitive mutants (alleles of dpy-2 gene on L.G. II). The maternal or non-maternal inheritance was determined by the A and B tests (HIRSH and col.1976). Both prove non-maternal inheritance of the two temperature-sensitive phenotypes. This was not surprising according to the temperature sensitive periods, (see below) and indicates that roller and dumpy phenotypes of ts L 48 are not due to contribution of an oocyte component. THE TEMPERATURE SENSITIVE PERIODS The temperature-sensitive periods (TSP) of the two ts L 48 phenotypes were inferred from schift-up and schift-down experiments. A TSP is delineated by the earliest time of shift-down (from 22 C to 17 C) at which the mutant phenotype is observed and the latest time of shift-up at which mutant phenotype occurs. The TSP of the roller phenotype begins a few hours after hatching. It is entirely situated in the first larval stage (L1), from 18 hrs to 25 hrs of development at 22 C after fertilized eggs deposition). The TSP of the dumpy phenotype is more extended. It includes later L1 stage, all the L2 stage, and the beginning of the L3 stage (from 18 hrs to 42 hrs of development at 22 C, after fertilized eggs deposition) . MUTANT PHENOTYPES EXPRESSION AT 22 C ts L 48 size growth curves at 17 C and 22 C, demonstrate that dumpiness expression starts at the beginning of the L3 stage, near the end of the dumpy phenotype TSP. Regarding roller phenotype, it never be expressed until the adult stage. CONCLUSIONS The study of this mutant agrees with the conception that cuticular alterations can lead both to roller and dumpy phenotypes. Nevertheless, in contrast with the observations of Higgins and Hirsh ( 1977) on the temperature-sensitive roller mutant ts B 238, in C. elegans Bergerac - for ts L 48 at least - the roller TSP needs not coincide with the time of formation of the adult cuticule but may be very earlier.