Animals adequately change their behavioral patterns according to their internal states such as the extent of sexual maturation. To examine whether some signal(s) from gonad affect on worm''s behavior, first we analyzed
glp-1(ts) hermaphrodite animals which were raised at the restrictive temperature (25 deg C) during L2 stage to induce a germline proliferation defect. We found that the germline-defective
glp-1(both
or178ts and
e2141ts) animals show a mild chemotaxis defect to diacetyl, an AWA-sensed volatile attractant. Chemotaxis to another AWA-sensed attractant, pyrazine, and AWC sensed attractants, benzaldehyde and isoamylalcohol, were not affected in these animals, suggesting that germline signal(s) modify the diacetyl specific pathway of chemotaxis. To confirm the germline effect, we ablated the germline precursor cells (Z2, Z3) in wild-type animals with a laser microbeam and found that the chemotactic response to diacetyl but not to pyrazine was reduced in these animals. It is possible that the gonad signal(s) affect the diacetyl sensitivity by regulating the expression of the diacetyl receptor ODR-10 at AWA cilia. We, however, could not observe any changes in the expression pattern and level of ODR-10 tagged gfp in the germline-defective
glp-1 animals. To examine directly whether signal transduction in the AWA sensory neurons is affected in the germline-defective
glp-1 mutant, we observed the diacetyl-evoked calcium transients by expressing a calcium indicator, Cameleon under the AWA-specific promoter. Utilizing the PDMS microfulidic device (olfactory chip), we found that the AWA neurons, in the control animals with normally developed gonads, responded to diacetyl (1/1000 solution) presentation with sharp increases in calcium levels. The sharp increases were followed by relatively low increases which were sustained during the diacetyl application. The AWA neurons in germline-defective
glp-1 animals also responded to diacetyl (1/1000) similarly to control animals. We are currently analyzing with diacetyl in lower concentrations to see possible changes in the sensitivity in the germline-defective animals. Finally, we are attempting to isolate suppressors of the chemotaxis defect to diacetyl of the germline-defective
glp-1 mutant. By clonal mutant screening with ~1800 haploid genomes, we have isolated several candidate mutants in which germline defect did not affect diacetyl chemotactic response. Further analyses including the identification of responsible genes will reveal the molecular and cellular mechanism by which gonad signals control the olfactory sensitivity to a specific attractant.