Project description:Epigenetic inheritance plays an important role in mediating alternative phenotype in highly social species. In order to gain a greater understanding of epigenetic effects in societies, we investigated DNA methylation in the termite Zootermopsis nevadensis. Termites are the most ancient social insects, and developmentally distinct from highly-studied, hymenopteran social insects. We used replicated bisulfite-sequencing to investigate patterns of DNA methylation in both sexes and among castes of Z. nevadensis. We discovered that Z. nevadensis displayed some of the highest levels of DNA methylation found in insects. We also found strong differences in methylation between castes. Methylated genes tended to be uniformly and highly expressed demonstrating the antiquity of associations between intragenic methylation and gene expression. Differentially methylated genes were more likely to be alternatively spliced than not differentially methylated genes, and possessed considerable enrichment for development-associated functions. We further observed strong overrepresentation of multiple transcription factor binding sites and miRNA profiles associated with differential methylation, providing new insights into the possible function of DNA methylation. Overall, our results show that DNA methylation is widespread and associated with caste differences in termites. More generally, this study provides insights into the function of DNA methylation and the success of insect societies.
Project description:One of the most striking examples of phenotypic plasticity is the different phenotypes (i.e., castes) within a same nest of social insects. Castes usually derive from a single genotype initially by receiving social cues among individuals during development. Specific gene expression changes may be involved in caste differentiation, and thus, the regulatory mechanism of these changes should be clarified in order to understand social maintenance and evolution. The damp-wood termite Zootermopsis nevadensis is one of the most important model termite species, due to not only the availability of genomic, transcriptomic, and epigenomic information but also evidence that soldier- and worker-destined individuals can be identified in natural conditions. Given that the nutritional intakes via social interactions are crucial for caste differentiation in this species, there is a possibility that transcriptomic changes are influenced by the nutritional difference among these individuals. Here, whole body RNA-seq analysis of 3rd-instar larvae with biological replications and Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were conducted. We found the drastic expression differences during caste developments between soldier- and worker-destined individuals. The results indicated that there are several key signaling pathways responsible for caste formations, which are involved in developments and social interactions. Particularly, the nutritional sensitive signaling was upregulated in soldier-destined individuals, while some metabolic pathways were identified in worker-destined individuals. These bioinformatic data obtained should be utilized to examine the molecular mechanisms of caste determination in social insects.