Transcriptome survey of phototransduction and clock genes in marine bivalves

Abstract

ABSTRACT. Marine animals exhibit a variety of biological rhythms, such as solar and lunar-related cycles; however, our current molecular understanding of biological rhythms in marine animals is quite limited. Identifying and understanding the expression patterns of clock genes from available transcriptomes will help elucidate biological rhythms in marine species. Here, we perform a comprehensive survey of phototransduction and circadian genes using the mantle transcriptome of the scallop Patinopecten yessoensis and compare the results with those from three other bivalves. The comparison reveals the presence of transcripts for most of the core members of the phototransduction and circadian networks seen in terrestrial model species in the four marine bivalves. Matches were found for all 37 queried genes, and the expressed transcripts from the deep sequencing data matched 8 key insect and mammalian circadian genes. This demonstrates the high level 2 X.J. Sun et al. Genetics and Molecular Research 15 (4): gmr15048726 of conservation of the timekeeping mechanism from terrestrial species to marine bivalves. The results provide a valuable gene resource for studies of "marine rhythms" and also further our understanding of the diversification and evolution of rhythms in marine species.

Influence of light and temperature cycles on the expression of circadian clock genes in the mussel Mytilus edulis

“…Clock genes and their protein complexes interact via negative feedback loops, forming the molecular clock mechanism at the heart of biological timekeeping (Hardin, 2005;Young & Kay, 2001;Shearman et al, 2000). The single Per homolog present in molluscs (Sun et al, 2016;Constance et al, 2002) was isolated in M. edulis herein and grouped phylogenetically with other molluscan PER sequences (Figure S3). Also isolated was M. edulis Rev-erb (E75) containing the characteristic DNA-binding and ligand-binding domains (Figure S4) and shared most sequence similarity with other mollusc sequences (Figure S5).…”

“…However, second peaks in expression apparent during the subjective night for a number of M. edulis genes under LD (Cry1 and Reverb) and DD (Cry1, Clk and ROR) suggest a possible ultradian (<24 hr) rhythm. Hypothetical models of bivalve molecular clocks have been proposed to incorporate elements of both mammalian and insect core interactions Sun et al, 2016), though functional studies are required to further clarify bivalve clock organisation. The molecular mechanisms by which ultradian rhythms, such 12 hr tidal rhythms, are regulated are also yet to be elucidated.…”

“…Despite the importance of clock genes in regulating endogenous rhythmic processes in diverse phyla, the molecular mechanisms governing timekeeping ability are an understudied aspect of molluscan ecology. Recently emerging studies have characterised clock genes in gastropods (Cook et al, 2018;Duback et al, 2018;Schnytzer et al, 2018;Bao et al, 2017;Constance et al, 2002), cephalopods (Heath-Heckman et al, 2013), and bivalves Sun et al, 2016;Pairett & Serb, 2013) including mussels (Chapman et al, 2017;Connor & Gracey, 2011). Blue mussels, Mytilus edulis, are an edible species of commercial importance (FAO, 2018), a biogenic keystone species (Gutiérrez et al, 2003) and are considered early indicators of the effects of climate change (Zippay and Helmuth, 2012).…”