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.

Spontaneous daf and dpy Mutants Isolated from Mutator Strains

P.S. Albert and D.L. Riddle

Figure 1

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}

Figure 1