The biological mechanisms by which neural circuits are modulated by an animal's sex ("gender") is poorly understood. We have previously found that C. elegans males and hermaphrodites differ in their response to several odorants detected by shared circuitry. In particular, hermaphrodites are more attracted than males to the odorant diacetyl, a food cue sensed by the chemoreceptor
odr-10, expressed in the AWA sensory neuron. Recently, we have shown that regulated
odr-10 expression underlies sex differences in diacetyl attraction. In adult males,
odr-10 expression is significantly reduced compared to hermaphrodites, allowing these animals to prioritize exploratory behavior over feeding. Moreover, transient starvation upregulates
odr-10 in males to promote feeding. Through a candidate screen, we identified the TGFbeta ligand
daf-7 as a regulator of
odr-10 expression. Males with mutations in
daf-7 or the downstream SMAD
daf-8 have increased expression of
odr-10. In contrast, these mutations have no apparent effect on
odr-10 expression in hermaphrodites. Animals with mutations in
daf-5, a transcription factor inhibited by DAF-7 signaling, show decreased expression of
odr-10; moreover,
daf-5 males show no increase in
odr-10 expression in response to starvation. These findings suggest that DAF-7 regulates feeding-state-mediated changes in
odr-10 expression in a sex-dependent manner. We are currently working to understand how the sex determination pathway intersects with DAF-7 signaling to bring about state-dependent changes in
odr-10 expression and behavior.