We have been investigating natural variation in the neuronal expression of a TGF-ß signaling molecule, DAF-7, that plays a pivotal role in the regulation of diverse behaviors of C. elegans such as the dauer developmental decision, reproductive egg laying, and feeding. Normally expressed only in the ASI pair of chemosensory neurons, recent work in our lab (Meisel, JD et. al. Cell, 2014) has demonstrated that daf- 7 expression is induced in the ASJ neurons upon exposure to the bacterial pathogen, Pseudomonas aeruginosa, and that this change in expression is functionally important in producing a pathogen avoidance behavior. To investigate natural variation in this response to the microbial environment, we have examined a panel of 25 C. elegans wild isolate strains for differences in pathogen-induced
daf-7 expression. We observe a wide range in the kinetics of
daf-7 expression changes in the response of wild strains to pathogenic bacteria. Two strains were identified as having distinctly different phenotypes from N2: one which has constitutive expression of
daf-7 in ASJ and another which only weakly induces
daf-7 expression in response to P. aeruginosa .We have identified distinct genomic loci underlying these phenotypes and are currently working to define the natural polymorphisms that cause variation in the pathogen-induced neuronal expression of
daf-7.