We are interested in how the germline is protected during stressful conditions. We have found that when animals are subjected to stress 1) translational rates slow down, 2) more germ cells undergo apoptosis, and 3) germ granules are formed in the gonad. TIAR-1, one of the three homologs of the TIA-1/TIAR-1 family of RNA binding proteins in C. elegans, is required to induce germ cell apoptosis downstream from CED-9. In mammalian cells these proteins are required for Fas -induced apoptosis, and are important for stress granules formation. Our aim is to investigate TIAR-1 fuction in normal and stressful conditions in the germline.Two main classes of ribonucleoprotein complexes are formed in the gonad during stress: one in the core of the gonad and another in the oocytes. Upon starvation in the presence of cycloheximide, the gonad core granules did not form, but the oocyte granules did. This supports the hypothesis that RNP complexes found in the C. elegans gonad have different nature and perhaps functions. A TIAR-1::GFP transgene (produced by CRISPR-Cas9) had its highest expression in the animals' germ line, in which was mostly localized in the cytoplasm and associated to P granules. When animals were exposed to stress, the TIAR-1::GFP aggregated in both gonad core and oocye granules. In animals that lack tiar-1, we observed that gonad core granules did not form but oocyte granules were still present after starvation, heat shock, and prolonged meiotic arrest. tiar-1(-) animals had small brood size and embryonic lethality; both phenotypes were stronger at higher temperature. A high incidence of males in tiar-1(-) was also observed. We further explored if tiar-1(-) animals' germline defects are accentuated during stress. Thus animals were exposed to heat shock and starvation and their progeny was analyzed for embryonic lethality, and sterility. tiar-1(-) animals had increased embryonic lethality in the progeny that had been fertilized before, during, and immediately after stress, but not in the progeny that was produced long after stress. tiar-1(-) animals that survive heat shock are often sterile. We found that starvation has little to no effect on embryonic survival or fertility, neither in wild type nor in tiar-1(-) strains. These results suggest that TIAR-1 has a role in protecting the oocytes during and shortly after heat shock, nevertheless nematodes seem to have other protective mechanisms against starvation.

Affiliations:
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis MN
- Instituto de Fisiologia Celular, UNAM, Circuito Exterior s/n, Ciudad Universitaria, Mexico D.F. 04510