Cloning and characterization ofRARs andRXRs from noble scallopChlamys nobilis, a bivalve rich in carotenoids

Abstract

The noble scallop Chlamys nobilis that rich in carotenoids is one of the most popular scallop species for aquaculture. Very little is known whether bivalve SRB-like-3 gene expression is regulated by retinoic acid receptor (RAR) and/or retinoic X receptor (RXR). In this study, the full-length cDNA of RAR and RXR genes of C. nobilis was cloned and characterized for the first time, and then, the tissue differential expression of RAR and RXR mRNA in polymorphic C. nobilis was assessed. The roles of RAR and RXR in carotenoid accumulation in C. nobilis were assessed by manipulating the carotenoid content in tissues of C. nobilis via inhibiting the expression of SRB-like-3 gene. The results revealed that two isoforms of RAR (cnRARa (1958 bp/434 aa) and cnRARb (1901 bp/415 aa)) and four RXR isoforms (cnRXRa (1353-bp/450 aa), cnRXRb (1341-bp/446 aa), cnRXRc (1298-bp/436 aa) and cnRXRd (1286-bp/432 aa)) were cloned and characterized from C. nobilis. The reduction of carotenoid content caused by inhibition of SRB-like-3 gene induced the up-regulation of RAR and RXR genes, suggesting that RAR and RXR genes may play a role in the regulation of carotenoid accumulation in haemolymph of C. nobilis. The findings of this study provide important clues for the regulation mechanism of total carotenoid accumulation in C. nobilis.