Abstract
Across the tree of life, an organism’s survival and reproduction is dependent on the ability to sense, respond, and in some instances predict their environment. Organisms that can properly integrate environmental and internal cues to form adaptive behaviors can increase their fitness. One critically important sensory modality in animals is olfaction, which enables animals to locate sources of food and mates, as well as pathogens or predators. Responses of animals to food or chemical stimuli can vary based on their internal state and experience. How experience, particularly experiences during development, modulates behavioral differences in adult animals and how these experiences are encoded in the nervous system remains to be fully explained. Using the nematode worm Caenorhabditis elegans, our lab and others previously showed that adult animals which transiently experienced stress-induced dauer arrest, an evolutionarily conserved developmental diapause, (post-dauer) exhibit distinct gene expression profiles and behavioral responses compared to control adults which bypassed the dauer stage. Here I show that post-dauer adults also exhibit significantly enhanced responses to volatile attractive odors, including odors sensed by the AWA and AWC olfactory neurons, as compared to control adults that bypassed the dauer stage. In contrast, responses of post-dauer adults to repellents remain intact. We find that dauer larvae and post-dauer adults upregulate the diacetyl olfactory receptor ODR-10 in the AWA chemosensory neuron pair. Expression of this receptor in AWA neurons is known to drive food searching behavior in adult worms and is regulated in a sexual dimorphic manner. The dauer-induced upregulation of this receptor in AWA neurons requires the stress response transcription factor DAF-16/FOXO. Via spatiotemporally regulated depletion of DAF-16 in AWA, I have established that DAF-16 acts early in development prior to dauer entry to transcriptionally upregulate odr-10 expression, and that it is dispensable for the maintenance of higher expression levels in post-dauer adults. My data suggest a model in which early developmental stress is encoded at the level of regulation of olfactory receptor gene expression, and may modulate behavioral differences between adult animals based on their respective developmental experiences. In support of this model, I have also characterized additional genes of sensory molecules that are also subject to similar experience-dependent regulation.