Recessive mutations in
fem-1 and
fem-2 cause XX animals to develop as spermless hermaphrodites. Temperature sensitive mutations in these genes have allowed us to revert them by looking for self-fertile hermaphrodites at the restrictive temperature. Specifically, the F1 of EMS mutagenized parents homozygous for either
fem-1(
hc17) or
fem-2(
b245) was screened for fertile worms. In this way we have isolated ten dominant fem suppressors, three of
b245 and seven of
hc17. Dominant suppressors of
hc17 appear at a frequency of 1.5x10+E-5. The best characterized of these is
q20. This allele, when crossed out of the
hc17 background, causes a masculinization of the germ line (Mgl) of XX animals. No oocytes but only sperm are made in an otherwise normal hermaphrodite gonad. Mature sperm fill up the entire proximal arm of the gonad and spermatogenesis extends back into the distal arm. The
q20 allele is temperature sensitive. Hermaphrodites homozygous for
q20 are Mgl at 25 C but fertile at 15 C. At 15 C, animals homozygous for
q20 have an average brood size of 445 (n=36) indicating that more sperm are made even at permissive temperature. A semi- dominant effect is observed at 25 C; about half the
q20/+ hermaphrodite progeny from the cross
q20/+ males x
unc-5 hermaphrodites are Mgl (25 C). Males homozygous for
q20 are fertile at 25 C. The map position of
q20 (on chromosome IV between
unc-5 and
dpy-20) suggested that it might lie at the
fem-3 locus. Therefore, an F1 reversion of animals, fertile animals homozygous for
q20 was performed. Revertants segregate Mgl animals, fertile animals and Fem animals. We have shown that one of the revertants does not complement a known
fem-3 allele (
e1996). These results suggest that
q20 is in fact at the
fem-3 locus. The map positions and/or phenotypes of four other alleles (
q24,
q60,
q61 and
q62) make it likely that they too are
fem-3 dominants. Of the remaining two
hc17 suppressors, one,
q21, appears to be an intragenic revertant. Another
q63, is not linked to chromosome IV. Dominant suppressors of
b245 also occur at a frequency of 1.5x10+E-5. Two of these,
q22 and
q23, have been partially characterized. After removal from the
b245 background, both are temperature sensitive sterile with a Mgl phenotype. Both also map to chromosome IV.
q22 has been mapped more closely and lies between
unc-24 and
dpy-20, placing it within 0.5% of
fem-3. These suppressors are probably
fem-3 dominant alleles as well.