We are interested in identifying genes whose products interact with
glp-1 during embryogenesis. Our approach has been to identify and characterize mutations which suppress the temperature sensitive maternal effect embryonic lethal phenotype of
glp-1(
e2142). EMS- induced suppressors of
glp-1(
e2142), (called sog), have been isolated in a screen which demanded that the suppressors be dominant sog alleles of genes which were expressed in the germ line. L1 larvae from
glp-1(
e2142); permissive temperature were mutagenized and shifted up to restrictive temperature. Offspring would hatch and grow only if a suppressor mutation had been induced, since
glp-1(
e2142) produces no viable embryos at 25 C. If the sog mutation had occurred in the soma of the hermaphrodite parent, the suppression would not be heritable in the surviving progeny. However, if the sog had occurred in one of the two germ line progenitor cells, the suppression would be heritable. The EMS-induced suppressors define three sog loci. Eight of these suppressors map to two loci on LGI, and 30 are linked to LGIII. One of the sog loci on LGI is extremely close to the left of
dpy-5, and the other is between
unc-29 and
unc-75. The sog locus on LGIII was positioned approximately halfway between
unc-79 and
dpy-17. These suppressors only suppress the
e2142 allele of
glp-1.Surprisingly, we recovered dominant suppressors at a frequency expected for loss of function mutations. If these were loss of function mutations, we anticipated that we might be able to isolate additional sog alleles from a strain which would generate transposable element induced mutations. Both dominant and recessive suppressors were isolated from
glp-1(
e2142);
unc-22. The dominant suppressors are likely to be allelic with the loci identified by the EMS-induced mutations, however their dominance precludes simple tests for complementation. One dominant mutator-induced sog on LGIII has been isolated. It maps to the same region as the EMS-induced sog. Of thirteen dominant suppressors on LGI, eleven map close to
dpy-5 and two map to the right. Ten of the eleven alleles are associated with an apparent Tc1 insertion in the region to the left of
dpy-5.Another way to test the hypothesis that these are loss of function alleles is to see how they behave in strains with different ratios of mutant and wild-type alleles. hDp20 has been used to supply an extra wild-type allele of the sog locus close to
dpy-5. sog/sog suppresses twice as well as +/sog. +/sog/sog suppresses with a similar efficiency to +/sog, but +/+/sog shows almost no suppression. A deficiency which includes this locus, sDf4, suppresses
glp-1(
e2142) indicating that simply reducing the amount of the sog(+) product suppresses
glp-1(
e2142). We asked whether increasing the amount of the sog(+) product would exacerbate the
glp-1(
e2142) defect. We find that a strain with three copies of sog(+) produces mostly Glp embryos at a temperature normally permissive for growth. The suppressed strains appear wild-type. We removed
glp-1(
e2142) from the suppressor strains to determine whether the suppressors had any other phenotype. A mutator-induced allele of each of the three loci was tested. The Sog mutant strains have no visible phenotype and have normal levels of embryonic viability and fertility. It is possible that these genes are functionally redundant members of a gene family, so we are constructing strains with multiple sog mutations to look for a phenotype. A Sog double mutant strain containing both of the LGI sogs also has no phenotype. We are currently constructing a Sog triple mutant strain.