Genetic studies on diversity and plasticity of nictation behavior

Abstract

Animal behavior is the most complex phenotypes arising from the interaction of genes and environment through biological systems and exhibits significantly higher phenotypic diversity and plasticity than other traits. For the successful execution of behavior, the entire biological system must develop properly and function accurately. This overall process involves some regulatory mechanisms programmed in the genome, and some of these regulatory mechanisms work robustly without being greatly affected by the environment, while some regulatory mechanisms are sensitive to the given condition and contribute to behavioral plasticity. Also, the genetic variation among different individuals produces heritable behavior variation. In this study, I performed genetic analysis on nictation behavior, a hitchhiking behavior of C. elegans, to reduce the genetic diversity and environmental plasticity of behavior to gene level. Specifically, I analyzed the heritable variation of nictation behavior among wild isolates of C. elegans sampled from all over the world. Using quantitative genetic techniques, I identified a single genetic locus which underlies behavioral variation between N2 strain from Bristol and CB4856 strain from Hawaii. Genetic analysis of the locus revealed that small RNAs might serve as potential regulators of the nictation behavior variation. Additional genetic analysis between two strains showed that the neuropeptide receptor gene which had been artificially selected in the laboratory is involved in regulation of nictation behavior. I also investigated the plasticity of nictation behavior according to environmental cues and related regulatory signaling pathways. Feeding pathogenic bacteria and nematode pheromone treatment can lead to quantitative differences in nictation behavior, which is mediated by TGF-β signaling pathway and cGMP signaling pathway. In summary, genetic approach on nictation behavior successfully analyzed the genetic basis of behavioral variation and plasticity at the gene level. These findings suggest a molecular mechanism of behavior adaptation and evolution in nature.