Identification and characterization of light-responsive genes in pre-settlement eyed veligers of Mytilus coruscus

Abstract

Mytilus coruscus is one of large bivalve mollusks that is wildly distributed along the coasts of Korea, Japan and China and as a potential economic shellfish candidate. Efforts to propagate and culture M. coruscus have expanded worldwide recent years. The larval stage of bivalves is a vital life-history phase, of which the eyed veligers larva with a pigmented eyespot is the pre-settlement phase of M. coruscus. However, information on light conditions for the breeding of its larval during the eye-spotting period is still limited. In our study, based on the transcriptome analysis of the different light cycles from M. coruscus were performed with the DNBSEQ to screen for light-response genes. Comparative transcriptome analysis identified 853 differentially expressed genes (DEGs) in the 12 h vs 0 h group and 696 genes were differentially expressed between 12 h vs 24 h group. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses revealed that DEGs were assigned to 1078 and 969 pathways, respectively. The DEGs were enriched in organismal systems pathways such as immune system pathway, endocrine system pathway, development pathway, and environmental adaptation pathway. Further analysis revealed that DEGs, including CRY and CLOCK, were significantly overrepresented in the circadian rhythm pathway. We also identified a visual OPIN gene, which affects the detection of relevant visual signals. Quantitative real-time PCR (qRTPCR) showed that CRY and CLOCK were down-regulated, whereas OPIN was up-regulated. The data from this study provides important insights into the light response of M. coruscus, which will aid future investigations into the management of M. coruscus breeding in Bivalvia.

Keywords

• Mytilus coruscus
• Transcriptome
• Light-responsive Genes
• Quantitative real-time PCR