Two olfactory mutants,
ky27 and
ky185, were identified in two separate screens for mutants defective in chemotaxis towards the volatile odorant diacetyl. Complementation tests showed that
ky27 and
ky185 are alleles of the same gene, named
odr-9. Three-factor cross mapping of
odr-9 placed it in the interval between
dpy-9 and
lin-1, on the left arm of LG IV. The
egl-4 locus is also found in this interval, at approximately the same genetic map position as was calculated for
odr-9. Complementation tests showed that
odr-9 and
egl-4 are the same gene.
egl-4 has five previously identified alleles:
n477,
n478,
n479,
n579 and
n612, four of which were available for analysis. All six
odr-9 /egl-4 alleles tested exhibit a strong defect in sensing diacetyl. In addition,
odr-9 exhibits a number of other pleiotropies.
odr-9 has defects in chemotaxis towards several other volatile attractants, including odorants sensed by both AWA and AWC neurons, although the diacetyl response is the most strongly affected. Preliminary data suggest
odr-9 also has a defect in sensing the water soluble chemical, lysine. Futhermore,
odr-9 mutants display an egl-d phenotype, hyperforaging behavior and hypersensitivity to dauer pheromone. The dauer pheromone hypersensitivity may contribute to the weak daf-c phenotype observed in these mutants.
odr-9 mutants are larger in body size than wildtype and they have dark-colored intestines. The many pleiotropies of
odr-9 mutants leads us to believe that the ODR-9 protein may be a component of multiple sensory signal transduction pathways. Currently we are working on further behavioral and morphological characterization of
odr-9 . We are also using multiple approaches to try to clone
odr-9/egl-4. We are using PCR polymorphisms to narrow down the region of interest to facilitate further transformation rescue experiments and identification of candidate genes . Additionally, we are screening for a Tc1 insertion allele of
odr-9 in a
mut-7 background. 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.