GLH-1 and GLH-2 are members of a family of Vasa-like germline helicases in C. elegans. Both proteins contain eight conserved RNA helicase motifs, glycine-rich motifs, and retroviral-like CCHC zinc fingers. Based on antibody staining, both GLH proteins are associated with P granules at all stages of germline development. We have used reverse genetics to study the function of these genes in germline development. Injection of dsRNA to both
glh-1 and
glh-2 caused the injected worms to produce sterile progeny, with a higher percent sterile progeny at elevated temperature than at lower temperature. The sterile progeny had stunted gonad arms, lacked gametes, and lacked detectable accumulation of GLH-1 and GLH-2. In addition, they failed to show P-granule staining for PGL-1 and for four other P-granule epitopes. Similar levels of sterility were induced by injection of dsRNA specific for
glh-1, but not by dsRNA specific to
glh-2. To address whether the sterility is maternal-effect or zygotic and the issue of redundancy, we sought mutants. We isolated a Tc1 insertion in
glh-1 from Michael Hengartner's transposon library. The Tc1 insertion is in exon 4 of
glh-1.
glh-1::Tc1 mutants show both maternal-effect and zygotic sterility, both of which are sensitive to temperature -
glh-1::Tc1 homozygous mutants produce 100% sterile offspring at elevated temperature, but only 10-15% sterile offspring at low temperatures. These phenotypes are very similar to the phenotypes seen in
pgl-1 mutants, a gene encoding another P-granule component. In addition, P-granules in
glh-1::Tc1 homozygotes fail to stain for GLH-1, PGL-1, and four other P-granule epitopes, but do stain positively for GLH-2, MEX-1, and MEX-3. Western analysis on this strain revealed that GLH-1 protein accumulation was not detectable while PGL-1 protein was present. This suggests that PGL-1 protein does accumulate but is not localized to P granules in this mutant. These results suggest that at least
glh-1 function is required for germline development mainly at high temperatures.