Molecular cloning and characterization of SoxB2 gene from Zhikong scallop Chlamys farreri

The Sox proteins play critical roles during the development of animals,including sex determination and central nervous system development.In this study,the SoxB2 gene was cloned from a mollusk,the Zhikong scallop(Chlamys farreri),and characterized with respect to phylogeny and tissue distribution.The full-length cDNA and genomic DNA sequences of C.farreri SoxB2(CfSoxB2) were obtained by rapid amplification of cDNA ends and genome walking,respectively,using a partial cDNA fragment from the highly conserved DNA-binding domain,i.e.,the High Mobility Group(HMG) box.The full-length cDNA sequence of CfSoxB2 was 2 048 bp and encoded 268 amino acids protein.The genomic sequence was 5 551 bp in length with only one exon.Several conserved elements,such as the TATA-box,GC-box,CAAT-box,GATA-box,and Sox/sry-sex/testis-determining and related HMG box factors,were found in the promoter region.Furthermore,real-time quantitative reverse transcription PCR assays were carried out to assess the mRNA expression of CfSoxB2 in different tissues.SoxB2 was highly expressed in the mantle,moderately in the digestive gland and gill,and weakly expressed in the gonad,kidney and adductor muscle.In male and female gonads at different developmental stages of reproduction,the expression levels of CfSoxB2 were similar.Considering the specific expression and roles of SoxB2 in other animals,in particular vertebrates,and the fact that there are many pallial nerves in the mantle,cerebral ganglia in the digestive gland and gill nerves in gill,we propose a possible essential role in nervous tissue function for SoxB2 in C.farreri.