Cloning and expression analysis of a cytoplasmic juvenile hormone-binding protein from the mud crab, Scylla paramamosain (Decapoda, Brachyura, Portunidae)

Juvenile hormone (JH) has an important role in regulating the development of arthropods, and methyl farnesoate (MF) is the only juvenile hormone found in Crustacea to date. Juvenile hormone-binding proteins (JHBPs) bind to JHs and transport or deliver JH signals. In this study, the complete cDNA sequence of cytoplasmic JHBP (cJHBP) was obtained from Scylla paramamosain, which we named Sp-cJHBP. The putative protein sequence of Sp-cJHBP contains two conserved glyoxalase domains. Expression analysis revealed that Sp-cJHBP expression varied greatly among larval developmental stages, with a significant reduction at the Zoea-5 stage. Sp-cJHBP had the highest expression in the ovary, with low expression in other tissues of the female adult crabs. During ovarian development, the expression of Sp-cJHBP changed significantly in the ovary, though its trends correlated poorly with the ovarian developmental process. While the expression in the mandibular organ (MO) was similar to 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR), which is a key gene involved in MF biosynthesis. After unilateral eyestalk ablation (ESA), the expression of Sp-cJHBP altered significantly in the ovary and MO, but not in cerebral ganglion and thoracic ganglion. Altogether, these results suggest that Sp-cJHBP is likely to function primarily in the ovary, probably through binding to MF.