Sequence polymorphism in a marine bivalve (Perna canaliculus) orphan G protein‐coupled receptor gene: Preliminary description and possible implications

Abstract

G protein‐coupled receptors (GPCRs) form a protein superfamily whose members mediate the detection of a diverse range of extracellular signals across a wide taxonomic range. With the exception of opsins, data on molluscan GPCRs are still sparse. Here, we report a preliminary characterisation of a novel GPCR gene, denoted dq646643, from a commercially significant marine bivalve, the green‐lipped mussel (Perna canaliculus). Levels of dq646643 transcripts varied widely between different tissues and were detected at their highest levels in the posterior adductor mussel and mantle edge. Phylogenetic analyses were unable to identify any clear dq646643 orthologues, although it was apparent that the dq646643 lineage arose from an early divergence within the metazoan GPCR rhodopsin superfamily. Despite having an ancient lineage, dq646643 displays high levels of translated sequence polymorphism. Although we have no definitive explanation for these high levels of polymorphism, this finding is consistent with reports from other marine invertebrates. These results suggest that, as apparently for oysters, P. canaliculus may carry a significant “genetic load” which needs to be considered during any selective breeding of this species.