Most cellular processes require inputs from multiple gene products. We have been studying genetic interactions that include
mel-28, a conserved and essential gene with key roles in the post-mitotic rebuilding of the nuclear pore. As a classic maternal-effect lethal gene,
mel-28 mutants from heterozygous mothers live to produce normal-sized broods that consist entirely of dead embryos. We did an RNAi screen to identify genes that cause sterility in
mel-28 mutants. Among the genes we found were those encoding components of dynein, a minus-end directed MT motor, and dynactin, a complex known to help couple dynein to its cargo. To better characterize phenotypes caused by disrupting these genes simultaneously, we have generated double and triple mutants using a severe hypomorphic
mel-28 allele and temperature sensitive mutants of
dhc-1, which encodes the heavy chain of dynein, and
dnc-1, which encodes the
p150glued subunit of dynactin. We have found that
mel-28(
t1684);
dhc-1(
or483ts) double mutants show a severely reduced brood size compared with each single mutant. Reciprocal crosses suggest the female gonad is defective in
mel-28;
dhc-1 double mutants, and indeed the proximal gonad is disorganized in these animals. The
dnc-1(
or404ts) mutant has a fertilization defect that is rescued in the
dnc-1;
mel-28 double mutant, suggesting that
dnc-1 and
mel-28 act antagonistically in fertilization. While
dhc-1;
dnc-1 double mutants showed a similar fertilization defect compared to the
dnc-1 single mutant,
dnc-1;
mel-28;
dhc-1 triple mutants resembled the rescued
mel-28;
dnc-1 double mutant. This suggests that the
dhc-1(
or404ts) defect does not influence the loss of fertility in
dnc-1 mutants nor its rescue by disruption of
mel-28. The triple mutant brood size was significantly larger than the brood size in the
dhc-1;
mel-28 double mutant, suggesting that loss of
dnc-1 function mitigates the fertility defects caused by disruption of
mel-28 and
dhc-1. Taken together this suggests that
dnc-1 and
mel-28 act antagonistically in a fertilization process that is indifferent to defects caused by
dhc-1(
or404ts). In contrast fertility defects caused by the
mel-28;
dhc-1 lesions affect processes that are sensitive to dynactin function.