We identified two olfactory mutants,
ky27 and
ky185 , in two independent screens for mutants defective in chemotaxis towards the volatile odorant diacetyl. Complementation tests showed that
ky27 and
ky185 are allelic to the known mutant
egl-4 .
egl-4 has five previously identified alleles:
n477 ,
n478 ,
n479 ,
n579 and
n612 , four of which are available for analysis. All six
odr-9/egl-4 alleles we tested exhibit strong defects in diacetyl chemotaxis. All alleles also show widespread defects in other olfactory responses mediated by both AWA and AWC neurons, although the diacetyl response is the most severely affected.
odr-9/egl-4 mutants also display several other pleiotropies. They are egl-d, with mutants holding ~3 X as many eggs in utero as wildtype, and ~30% of these eggs being past the 1 1/2-fold stage.
odr-9/egl-4 mutants are also hyperforaging, male mating defective and hypersensitive to dauer pheromone. The dauer pheromone hypersensitivity may contribute to the weak daf-c phenotype of
odr-9/egl-4 . Mutants are 17%-26% longer in body length than wildtype and have dark intestines. The many pleiotropies of
odr-9/egl-4 mutants suggest that ODR-9/EGL-4 functions in multiple pathways. Interestingly, although all mutant alleles tested show all the above phenotypes, they do not fall into a perfect allelic series; for example, the mutant with the strongest defect in pyrazine chemotaxis also has the weakest defect in diacetyl chemotaxis. Generally,
n478 and
n479 have strong defects in most of the categories tested, whereas
n477 and
ky185 have weaker defects. Data compiled suggest
n478 is the most likely candidate for a null allele of
odr-9/egl-4 . Currently we are focusing on further characterization of
odr-9/egl-4 alleles, double mutant analysis and cloning efforts. We are using PCR-based polymorphism mapping to narrow down the region of interest to facilitate identification of candidate genes. We hope that the molecular cloning of
odr-9/egl-4 will help us to understand more about not only olfactory signaling in worms, but also about the relationships among diverse processes, such as chemoattraction, dauer formation, egg-laying and body size determination, all of which seem to require
odr-9/egl-4 .