Construction of a massive genetic resource by transcriptome sequencing and genetic characterization of Megasyllis nipponica (Annelida: Syllidae).

Understanding the processes and consequences of the morphological diversity of organisms is one of the major goals of evolutionary biology. Studies on the evolution of developmental mechanisms of morphologies, or evo-devo, have been extensively conducted in many taxa and have revealed many interesting phenomena at the molecular level. However, many other taxa exhibiting intriguing morphological diversity remain unexplored in the field of evo-devo. Although the annelid family Syllidae shows spectacular diversity in morphological development associated with reproduction, its evo-devo study, especially on molecular development, has progressed slowly. In this study, we focused on Megasyllis nipponica as a new model species for evo-devo in syllids and performed transcriptome sequencing to develop a massive genetic resource, which will be useful for future molecular studies. From the transcriptome data, we identified candidate genes that are likely involved in morphogenesis, including genes involved in hormone regulation, sex determination and appendage development. Furthermore, a computational analysis of the transcriptome sequence data indicated the occurrence of DNA methylation in coding regions of the M. nipponica genome. In addition, flow cytometry analysis showed that the genome size of M. nipponica was approximately 524 megabases. These results facilitate the study of morphogenesis in molecular terms and contribute to our understanding of the morphological diversity in syllids.