Characterization and expression analysis of seven putative JHBPs in the mud crab Scylla paramamosain: Putative...

Juvenile hormone binding proteins (JHBPs) serve as the carriers that transport juvenile hormone (JH) to target tissues to activate JH signals. In this study, seven JHBPs from mud crab Scylla paramamosain were obtained. All Sp-JHBPs contained one JHBP domain, and Sp-JHBP4, 5, 6 also contained one Grp7_allergen domain. The predicted secondary and 3D structures are conserved among the seven Sp-JHBP domains, but the complete 3D structure of Sp-JHBP4, 5, 6 were more similar to lipopolysaccharide binding protein. Additionally, the potential ligands for Sp-JHBP1, 2, 3, 7 were ubiquinone 8 (UQ8) and JH II or JH III, and the predicted binding location and sites for JHs were similar to the structured known BmJHBP, suggesting that MF is a potential ligand for these Sp-JHBPs. Furthermore, the expression analysis showed that Sp-JHBP1 expression is relatively low in the 14 detected tissues, and Sp-JHBP2 has the highest expression in the ovary, while the other five JHBPs are highly expressed in the hepatopancreas. During larval development, Sp-JHBP2 is highly expressed during the Z1, M and C1 stages, which are three post-metamorphosis stages, while Sp-JHBP3 and 4 expression levels were significantly lower during the Z5 and M stages, which are two pre-metamorphosis stages. Moreover, the in vivo and in vitro study revealed that Sp-JHBP2 expression was reduced by MF, while the in vitro studies showed that Sp-JHBP3, 6, 7 are induced by MF in a concentration-independent manner. Taken together, we hypothesized Sp-JHBP1, 2, 3, 7 has the potential to bind MF and Sp-JHBP2, 3, 7 play a more important roles in MF signal, while Sp-JHBP4, 5, 6 were more likely to participate in immune response.