l-rhamnose-binding lectins (RBLs) in turbot (Scophthalmus maximus L.): Characterization and expression profiling in mucosal tissues.

Rhamnose-binding lectin (RBL) were mostly identified from egg cortex and ovary cells from vertebrates and invertebrates, with the specific binding activities to l-rhamnose or d-galactose. Previously, we found that a RBL gene was dramatically down-regulated (-11.90 fold at 1 h, -48.95 fold at 4 h, -905.94 fold at 12 h) in the intestine of turbot following Vibrio anguillarum challenge using RNA-seq expression analysis. In this regard, we sought here to identify RBLs in turbot, as well as the analysis of genomic structure, phylogenetic relationships, basal tissue distribution and the expression patterns following different bacteria challenge in mucosal tissues. In this study, two RBLs were captured in turbot with two conserved type 5 CRD5s, which were belong to type IIIc RBL. In phylogenetic tree analysis, turbot RBLs were clustered with tilapia, European sea bass and snakehead. In addition, in comparison of genomic architecture of turbot RBLs with the available published RBL genes revealed a high degree of conservation in the exon/intron organization among the teleost species. Moreover, both RBLs were significantly up-regulated in mucosal tissues following V. anguillarum and Streptococcus iniae challenge, indicated their critical roles in turbot mucosal immunity. Further studies are needed to expand functional characterization of detailed mechanisms of RBLs in fish innate immunity.