Genome-wide characterization of gap junction (connexins and pannexins) genes in turbot (Scophthalmus maximus L.): evolution and immune response following Vibrio anguillarum infection.

Abstract Gap junction (GJ), a special intercellular junction between different cell types, directly connects the cytoplasm of adjacent cells, allows various molecules, ions and electrical impulses to pass through the intercellular regulatory gate, and plays vital roles in response to bacterial infection. Up to date, the information about the GJ in turbot (Scophthalmus maximus) is still limited. In the current study, 43 gap junction genes were identified in turbot, phylogeny analysis suggested that gap junctions from turbot and other species were clustered into six groups, GJA, GJB, GJC, GJD, GJE and PANX, and turbot GJs together with respective GJs from Japanese flounder, half-smooth tongue sole and large yellow croaker have the same ancestors. In addition, these 43 genes distributed in different chromosomes unevenly. According to gene structure and domain analysis, these genes (in GJA-GJE group) are highly conserved in that most of them contain the transmembrane area, connexin domain (CNX) and cysteine-rich domain (connexin CCC), while PANXs contain Pfam Innexin. Although only one tandem duplication is identified in turbot gap junction gene, 235 pairs of segmental duplication are identified in turbot whole genome. To further investigate their evolutionary relationships, Ka/Ks was calculated, and results show that most ratios were lower than 1, indicating they had undergone negative selection. Finally, expression analysis showed that gap junction genes are widely distributed in turbot tissues and significantly regulated after Vibrio anguillarum infection. Taken together, our research could provide valuable information for further exploration of the function of gap junction genes in teleost.