The Genetic and Behavioral Analysis of Insulin Signaling in Caenorhabditis Elegans Learning and Memory

Insulin signaling plays a prominent role in regulation of dauer formation and longevity in Caenorhabditis elegans. Here, I show that insulin signaling also is required in benzaldehyde-starvation associative plasticity, where worms pre-exposed to the odor attractant benzaldehyde in the absence of food subsequently demonstrate a conditioned aversion response towards the odorant. Animals with mutations in ins-1, daf-2, and age-1 which encode the homolog of human insulin, insulin/IGF-1 receptor, and PI-3 kinase, respectively, have significant deficits in benzaldehyde-starvation associative plasticity. Using a conditional allele I show that the behavioral roles of DAF-2 signaling in associative plasticity can be dissociated, with DAF-2 signaling playing a more significant role in the memory retrieval than in memory acquisition. I propose DAF-2 signaling acts as a learning specific starvation signal in the memory acquisition phase of benzaldehyde-starvation associative plasticity but functions to switch benzaldehyde-sensing AWC neurons into an avoidance signaling mode during memory retrieval.MAS