Identification and characterization of the calcineurin B in Fenneropenaeus chinensis: its implications in competitive ability

Competitive behavior exists widely in animal and plant groups. When groups or individuals have the same needs for the limited resources, competition will occur in intra-species or inter-species. The existence of competitive behavior can significantly affect the growth performance of individuals. There is strong competitive behavior in the breeding of Fenneropenaeus chinensis, and we have proved that the competitive behavior among individuals of F. chinensis has a significant effect on individual growth traits, and this effect can be inherited. However, little information was available for the molecular mechanism of competition behavior in shrimp. Candidate genes involved in competitive behavior of F. chinensis have been identified by comparative transcriptome analysis in our previous study, among which there is a calcineurin (CN) B gene. CN is a highly conserved Ca²⁺/calmodulin (CaM)-dependent serine/threonine phosphatase, which is composes of a catalytic subunit (CNA) and a regulatory subunit (CNB). Previous studies reported that CN-B played an important role in the central nervous system mediated by Ca²⁺/CaM. In order to further prove the role of CN-B gene in the competitive behavior, in the present study, the full-length cDNA of CN-B of F. chinensis (FcCN-B) was cloned by RACE technology, and its expression in different tissues (ganglion, heart, stomach, hepatopancreas, and intestine) between high competitive group (HCG) and low competitive group (LCG) was analyzed by Real-time PCR. The results show that the full-length cDNA of FcCN-B is 2 867 bp, containing 95 bp of 5′ untranslated regions (UTR), 540 bp of open reading frame (ORF), and 2 232 bp of 3′ UTR. There are four conserved EF-hand Ca²⁺ binding domains in the ORF of FcCN-B. Protein homology analysis indicated that the amino acid sequence of FcCN-B has high homology with other species (78.8%-93.8%), among which FcCN-B has the highest homology with Eriocheir sinensis (93.8%) and then with Drosophila. melanogaster (90.5%). The phylogenetic relationship analysis showed that vertebrates and invertebrates were independently clustered into two branches. Furthermore, F. chinensis was clustered with E. sinensis into an independent branch, and then it was clustered to D. melanogaster, which suggesting that FcCN-B might have similar functions as it did in D. melanogaster. The results of Real-time PCR showed that the expression of FcCN-B in the ganglion was significantly higher in HCG than in LCG, but its expression in heart was significantly lower in HCG than in LCG. This study preliminarily proved that the calcineurin B may play a certain role in the competition behavior of F. chinensis, and will lay an important foundation for investigating the molecular mechanism of the competition behavior of F. chinensis.