Worm Breeder's Gazette 8(2): 46
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 mutations fem-2(b245) (a ts feminizing mutation) and tra-3(e1767) (a weak masculinizing mutation) are mutually suppressive at 25 C, so that the double mutant is an abnormal intersexual animal, occasionally self-fertile. A double mutant strain CB3688 was persuaded to grow at 25 C as a self-fertile stock. Initially the strain was barely viable even at 25 C, but after some generations it improved to the point where it could be mutagenized. On shift-down from 25 C to 20 C or 15 C, the suppressive effect of b245 is removed and the Tra-3 phenotype ( an abnormal sterile male) is expressed, unless another suppressor has been induced. Since CB3688 grows as a self-fertile stock, dominant or recessive or even maternal effect suppressors can be selected, depending on how many generations elapse between mutagenesis and shift down. Strong suppression may lead to a female phenotype; fortunately there are usually stray fertile XO males in the CB3688 population after shift-down, which can fertilize the females. Thus, both male/female and hermaphrodite revertant strains can be recovered. This simple and powerful technique has yielded a large number of suppressors. So far I have characterized 20 of these: tra-1(dom) 8 alleles fem-1 2 alleles fem-2 3 alleles (i.e., double mutants with b245 in cis) fem-3 7 alleles The last gene is a new sex-determining gene on LGIV (see map below), with effects similar to those of fem-1. Although the null phenotypes of fem-2 and fem-3 are not yet certain, it is likely that the three fem genes are similar, because they have the following properties in 1) Strong recessive mutations transform both XX and XO animals into fertile females. 2) These mutations are epistatic to tra-2 and tra-3 mutations. 3) These mutations are epistatic to tra-1 mutations in the germline, but not in the soma. 4) There is maternal rescue by the wild type gene product ( fem-2 shows the most rescue and fem-3 the least) The fem-3 gene has a novel property: fem-3/+ XO males from fem-3 XX mothers are frequently abnormal in gonadal development, but those from fem-3/+ XX mothers are wildtype. Therefore it appears that maternal, as well as zygotic, expression of fem-3 is essential for normal male development, in contrast to fem-1 and fem-2, for which zygotic expression is sufficient. [see Figure 1]