Worm Breeder's Gazette 10(1): 114

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.

A Temperature Sensitive Gain-of-function Allele of tra-1

P. Graham, M.K. Barton and J. Kimble

We have isolated several gain-of-function (gf) alleles of tra-1 as 
suppressors of fem-3(q96gf).  One of these, q183, is temperature 
sensitive for its XX (but apparently not for its XO) mutant phenotype. 
q183 was identified as tra-1 by mapping and reversion to tra-1(lf).  
At 25 C, both q183/q183 and q183/+ XX animals are female (n>200); at 
15 C, q183/q183 XX animals are still always female (n>200), but q183/+ 
XX animals are sometimes hermaphrodite.  XO animals homozygous or 
heterozygous for q183 are intersexual at both 15 C and 25 C.  A 
maternal effect of q183 can be observed when q183/+ XX progeny derived 
from homozygous or heterozygous mothers are compared.  At 15 C, a 
homozygous q183 XX female crossed with N2 males produces q183/+ XX 
offspring that are 97% female and 3% hermaphrodite (n=181).  (In this 
experiment, XX progeny were distinguished from XO progeny solely on 
the basis of phenotypic sex.  Since hermaphrodites plus females (
presumed XX) were about half and intersexual animals with masculinized 
tails (presumably XO) were about half the progeny, use of phenotypic 
sex to distinguish XX and XO animals is reasonable.) A heterozygous XX 
parent selfing at 15 C produces XX heterozygous progeny that are 50% 
female and 50% hermaphrodite.  The maternal effect of q183 suggests 
that wild-type tra-1 product, too, may be contributed to the embryo by 
the heterozygous mother.  The temperature sensitive period of tra-1(gf)
for hermaphrodite spermatogenesis has been examined in q183/+ XX 
animals.  Animals shifted from 15 C to 25 C prior to the end of the L2 
stage are all female, but are 50% hermaphrodite and 50% female if 
shifted up at the end of L2.  The percentage of XX animals that can 
make some sperm decreases as they are shifted from 25 C to 15 C during 
L1, L2, and L3.  These shifts suggest that the time of tra-1(gf) 
synthesis and/or function is during L2 and/or L3.  The tra-1(gf) TSP 
is prior to that of fem-3(lf) (Hodkgin, 1986) and fog-1 (Barton and 
Kimble, Abstracts for C.  elegans meeting, 1987, p. 173).  This data 
is consistent with a role of tra-1 in the regulation of the fem genes 
and fog-1 in the hermaphrodite germ line.  [Although the results of 
double mutant experiments (e.g.  tra-1(lf); fem(lf) doubles) suggest 
that the fem genes regulate tra-1 in somatic tissues, they also 
suggest that tra-1 regulates the fem genes and fog-1 in the germ line.
]  We are currently extending our maternal effect experiments with 
strains marked to distinguish XX and XO animals and we are seeking 
extragenic suppressors of tra-1(gf).