The AWA olfactory neurons mediate chemoattraction to a subset of volatile odorants. The orphan nuclear receptor gene
odr-7 is required for the sensory functions of the AWA neurons. We are interested in investigating the specification of AWA fate by ODR-7 and other factors. In
odr-7 null mutants, the AWA neurons fail to express the diacetyl receptor gene
odr-10 , the G-alpha protein subunit
gpa-5 , and the trp / trpl channel related gene
osm-9 . In addition, ODR-7 is required to maintain its expression by autoregulation. It is not known if ODR-7 regulates gene expression directly or indirectly. Many nuclear receptors function as heterodimers. ODR-7 may have a partner or multiple partners for regulation of different genes. To understand how
odr-7 functions, we are currently defining the promoter elements required for ODR-7 regulated gene expression in the AWA neurons. These regions will be examined for common sequence features that might represent a cognate DNA binding sequence for ODR-7 or other transcription factors. We are also examining the promoter of ODR-7 to determine what regions are important for early and late expression. To further explore
odr-7 function, we are examining the effects of misexpression of
odr-7 in other chemosensory neurons. We misexpressed
odr-7 in the AWB and AWC olfactory neurons using the
odr-1 promoter. Misexpression of
odr-7 is not sufficient to result in misexpression of
odr-10 ::GFP. However, expression of ODR-7 from this construct leads to the repression of the AWC-specific marker
str-2 ::GFP. These worms still chemotax to the AWC-sensed attractant isoamyl alcohol, indicating that the sensory function of AWC is not grossly altered. We are currently examining this in further detail and also examining the affects of this construct on the function of the AWB neurons. To define the domains of ODR-7 required for its gene regulatory functions, we have created an
odr-7 minigene. We are creating point mutations in the DNA binding domain and other regions of
odr-7 to examine their effects. Finally, we are currently mapping
sns-1 ( s ensory n euron s pecification).
sns-1 mutants fail to chemoattract to diacetyl and there is reduced expression of
odr-10 ::GFP in
sns-1 mutants. However, ODR-7 is expressed, suggesting that
sns-1 could be a binding partner or a downstream target of
odr-7 .