Production and functional characterization of a soluble recombinant molt-inhibiting hormone in the mud crab Scylla olivacea

The molt-inhibiting hormone gene of the mud crab Scylla olivacea (ScoMIH) was successfully cloned and characterized, encoding a 113-amino-acid precursor with a 78-amino-acid mature peptide. Similar to other Brachyuran crabs, ScoMIH is exclusively expressed in the eyestalk ganglia (ES) with slightly higher expression levels during the intermolt stage. To produce a biologically active recombinant ScoMIH, a fusion construct incorporating thioredoxin (Trx) and a His₆ tag was designed, yielding a soluble 27 kDa protein. Functional assays demonstrated that Trx-ScoMIH effectively suppressed the expression of cytochrome P450 monooxygenases in activated Y-organs, leading to reduced ecdysteroid secretion. Furthermore, in vivo administration of Trx-ScoMIH delayed and prolonged the molting process, mimicking the natural molt cycle observed in intact crabs. This study reports the successful production of a soluble, biologically active recombinant ScoMIH, providing a valuable tool for investigating MIH signaling.