The temperature sensitivity of the germline is conserved across phyla but the molecular pathways that are sensitive to temperature in the germline are unknown. The study of mutants that show a loss of fertility at temperatures lower than wild type organisms may allow us to uncover pathways that are important for buffering fertility at high temperature. We have uncovered a unique temperature sensitive phenotype in the primordial germ cells of
lin-35 mutants;
lin-35 L1s raised at 26 deg C fail to form canonical perinuclear punctate P granules ~20% of the time. Does LIN-35 therefore play a role in buffering germline function in response to temperature as it does in somatic tissues?
lin-35 mutants are known to have a reduced brood size even at 20 deg C but the temperature sensitivity of
lin-35 germline defects have not been explored as
lin-35 mutants raised at 26 deg C demonstrate ~100% larval arrest. We have developed two transgenic strains that rescue
lin-35 expression in either all somatic cells or solely in intestinal cells which rescues
lin-35 high temperature larval arrest, allowing investigation of the role of
lin-35 in the germline at 26 deg C. Interestingly, both transgenic lines partially rescue the fertility defects of
lin-35 mutants at 20 deg C, indicating that part of the loss of fertility in
lin-35 mutants is due to a loss of LIN-35 function in the soma. However, both transgenic lines are almost completely sterile at 26 deg C, a temperature 1 deg C below that which causes sterility in wild type. This suggests that LIN-35 functions within the germline to buffer high temperature stress. The buffering of temperature effects appears to be a conserved feature of LIN-35 function as many
lin-35 phenotypes, including synMuv and somatic germline gene repression, are temperature sensitive. However, unlike these other phenotypes, we have found that
lin-35 temperature sensitive fertility is not maternal effect and can be rescued by zygotic expression. As loss of fertility in wild type germlines has been linked to loss of sperm function, we supplied
lin-35 transgenic worms with wild-type sperm. Sterility was not rescued at 26 deg C in either transgenic background. However, there was ectopic localization of male sperm in the uterus in mutants expressing
lin-35(+) only in the intestine, but proper localization of male sperm in the spermatheca in the mutants expressing
lin-35(+) pan-somatically. This data suggests that LIN-35 may be necessary in the somatic gonad under high temperature stress conditions. We are currently testing this hypothesis with tissue specific expression. Taken together, we have found unique roles for LIN-35 in the both the soma and germline that are necessary for fertility in C. elegans when faced with high temperature stress.