Worm Breeder's Gazette 9(3): 28
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.
In an effort to tag genes that affect dauer larva formation, we have been using mutator strains to screen for spontaneous dauer- constitutive (daf) mutants, which form dauer larvae in the presence of food. The three strains used were TR679, DR842, and RW7097. TR679 has been described by Anderson et al., WBG 9(1): 29. DR842 is an unc-22(+) revertant of RW7080. The latter strain has approximately 70 copies of Tc1 and mutator loci on both LG I (mut-4) and LG II (mut-5). RW7097 contains 50-70 copies of Tc1 and a mutator, mut-6 IV. (Descriptions of RW7080 and RW7097 provided by Ikue Mori and Don Moerman, personal communication.) One worm was placed on each of many large plates at 20 C and the progeny (F2-F3 generations) screened just before the food supply was depleted (1,000 - 3,000 worms per plate). Populations of TR679 had to be screened visually because dauer larvae formed by this strain are SDS-sensitive. DR842 and RW7097 were screened visually and with SDS. We found mutations in three dauer-constitutive genes -- daf-1 IV, daf-24 11 (a new gene), and an X-linked daf that has a phenotype similar to daf-9(e1406). We also saved spontaneous dumpy mutants from visual screening, including three alleles of dpy-13, which are of interest to us because of the close proximity of dpy-13 to ama-1 IV ( see Bird and Riddle, this issue). Twitchers, presumably unc-22, were found quite frequently but not kept. Screens were performed on worms grown at 20 C, because fertility is low at 25 C. In having to select for dauer larvae formed at 20 C, we biased the screen against temperature-sensitive mutants. All three alleles of daf-24 are non- conditional, as is the X-linked daf, and both spontaneous mutant alleles of daf - I form a high percentage of dauer larvae at I 5 C. We have concluded that Tc1 does not insert into dauer-constitutive genes at high frequency (perhaps with the exceptions of daf-1 and daf-24) and that spontaneous mutations in dpy-13 appear to be quite common (at least in DR842 and RW7097). One spontaneous revertant of daf-1 has been found thus far, and three spontaneous intragenic dpy-13 revertants have been found. Hence, these mutants exhibit some properties consistent with transposon insertions. {Figure 1}