Neuronal Circuit And The Underlying Molecular Mechanisms For Food Odor Choice Behavior In Caenorhabditis Elegans

Backgrounds:Sensory neurons play important roles in regulating the response of Caenorhabditis elegans to changed signals in the environment. Recent studys have shown that sensory neurons are closely associated with the food odor choice behavior. However, it is largely unclear for the neuronal circuit and the underlying mechansms for food odor choice behavior.Aims:Using C. elegans as a model organism to elucidate the possible neuronal circuit and the underlying molecular mechanisms for food odor choice behavior.Methods:We used the food odor choice behavior model constructed by two signals (OP50 and PA14) to investigate the involved neuronal circuit and the underlying mechansms. We identified the genes encoding GPCRs, and neuropeptides involved in regulating food odor choice. We further examined the neuronal circuit and the underlying molecular mechanisms for food odor choice via technologies of double mutation, overexpression, and recuse assay. We also investigated the molecular signals functioning in regulating food odor choice in AIB interneurons.Results:Between ASH and ADL sensory neurons, optogenetics activated ADL sensory neurons led to the increased preference to PA14 in the model of food odor choice behavior; however, killing ADL sensory neuron caused the decreased preference to PA14 in the model of food odor choice behavior. Compared with control, arr-1mutant had the reduced preference to PA 14, rescuing its expression in ADL neurons led to phenotype similar to control. Moreover, srh-220 (RNAi) showed the increased preference to PA14, rescuing its expression in ADL neurons resulted in phenotype similar to control. srh-220(RNAi) strengthened the preference to PA14 of Psrh-220-ChR2 transgenic animals, whereas srh-220 overexpression reduced the preference to PA14 of Psrh-220-ChR2 transgenic animals. After testing functions of genes involved in secretion of neuropeptides in ADL neurons, we found neuron-specific RNAi of these genes in ADL neurons altered the food odor choice behavior. RNAi of neuropeptide encoding gene(flp-4 or nlp-10) caused the reduced preference to PA14, and rescuing their expression, respectively, in ADL neurons led to phenotype similar to control. Furthermore, mutation of flp-4 or nlp-10 gene reversed the phenotype of food odor choice in srh-220(RNAi) animals. Finally, we found that RNAi of npr-4 gene encoding receptor of FLP-4 reduced the preference to PA14, and rescuing its expression in AIB interneurons led to phenotype similar to control.Conclusion:A neuronal circuit of "ADL sensory neuron-AIB interneuron" was identified to regulate the food odor choice behavior in C. elegans. In ADL sensory neurons, the molecular signal pathway mediated byARR-1, GPCR/SRH-220, and neuropeptides of FLP-4 and NLP-10 was formed to controling the food odor choice behavior. Moreover, in AIB interneurons, NPR-4, receptor of FLP-4 neuropeptide, may positively regulate the food odor choice behavior in nematodes.