Characterization of an additional molt inhibiting hormone-like neuropeptide from the shrimp Metapenaeus ensis

Abstract

We have identified a second form of the type-II neuropeptide encoding a molt inhibiting hormone-like (MeeMIH-B) neuropeptide. MeeMIH-B showed only a 70% amino acid identity to the MIH-A (formerly MIH) isolated from the same species, suggesting a possible different function of the deduced neuropeptide. Like other neuropeptide members of the CHH family, the MIH-B gene consists of three exons separated by two introns. The levels of MIH-B mRNA transcript in the eyestalk decrease in the initial phase of gonad maturation and increase towards the end of maturation. The drop in MIH-B level suggests an inhibitory role for this neuropeptide in the initiation of vitellogenesis. MIH-B transcripts can also be detected in the brain, thoracic ganglion and ventral nerve cord. Together with the CHH-B peptide that we have previously described, this is the second peptide of the CHH family that can also be identified in the ventral nerve cord and in the XOSG complex. A recombinant MIH-B was produced and a polyclonal antibody against rMIH-B was subsequently generated. Specific anti-rMIH-B antiserum recognized the presence of MIH-B in the sinus gland, X-organs, as well as a giant neuron of the ventral nerve cord. Injection of rMIH-B delayed the molting cycle of the maturing female. Taken together, the results of this study suggest that a drop in MIH-B level may be required for the delay in the molting of the maturing females. © 2002 Elsevier Science Inc. All rights reserved.