Worm Breeder's Gazette 9(3): 34

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.

An Efficient Selection for fog-1 Alleles

K. Barton, S. Maples and J. Kimble

To identify additional genes involved in germline sex determination, 
we have isolated second site suppressors of fem-3(q96gf). XX animals 
homozygous for fem-3(q96gf) are Mog at restrictive temperature (25 C). 
They make tons of sperm in an otherwise hermaphrodite body. This 
particular gain-of-function allele of fem-3 was chosen because fem-3(
q96gf)/ y fertile (about 2% are fertile). 
Thus, very few fem-3 loss-of-function alleles are obtained.
A total of 45 independently isolated dominant suppressors of fem- 3(
q96gf) have been isolated thus far (frequency = 1/5000 haploid genomes)
. Among these are at least 18 alleles of fog-1. These alleles are 
similar to the fog-1 alleles found by Doniach (1985, CSH). They 
feminize the germ line of both XX and XO animals but have no effect on 
the XO soma. fog-1 mutations are dominant in the XO germ line but 
recessive in the XX germ line. None of the 18 alleles are t.s. One 
allele,q187, has been combined with loss-of-function alleles of tra-1 
and tra-2. The XX tra-1(e1099); 7) double mutant 
makes oocytes and no sperm. The same is true for the XX tra-2(e1425); 
double mutant. In the absence of fog-1 then, 
no sperm can be made.
It appears that fem-3(q96gf); als are 
fertile whereas fem-3(q96gf);  Thus, the dose 
of fog-1 limits the potential of fem-3(q96gf) to promote 
spermatogenesis. Additionally,
/ + XX animals produce fewer sperm than wild-type (as determined by 
brood size). It is possible that the wild-type function of fog-1 is to 
act as part of a sperm counting mechanism.
Finally, an unselected fog-1 allele (q155, found in an F2 visual 
screen for steriles), when heterozygous, also suppresses fem-3(q96gf). 
It seems likely therefore that the fog-1 alleles isolated as fem- 3(
q96gf) suppressors represent generic loss-of-function mutations in fog-
1 and that this will be an efficient way to isolate spontaneous fog-1 
alleles. To this end, fem-3(q96gf) has been backcrossed into TR403, a 
strain active for transposition of Tc1.