[Molecular cloning and sequence analysis of full length cDNA encoding molt-inhibiting hormone from Fennropenaeus...

Molt-inhibiting hormone (MIH) is a neuropeptide member belonging to the eyestalk CHH family. Molting in shrimp is controlled by MIH and ecdysone. By inhibiting the synthesis of ecdysone in the Y-organ, MIH indirectly suppress the molting activity of shrimp. A 697 bp full-length encoding molt-inhibiting hormone precursor cDNA, which has been accepted by GenBank (accession number: AF469187), was firstly amplified from the total RNA of eyestalk from Fennropenaeus chinensis by the 3' and 5' rapid amplification of cDNA ends (RACE) method. The 697 bp full-length cDNA encoding MIH precursor was assembled with a 320 bp 3' RACE product and 468 bp 5' RACE product. Results derived from searching by Blast revealed the 697 bp cDNA had high similarity with MIH gene of crustacean. By using Clustal X program, alignment of the amino acid sequence deduced from the 697 bp cDNA with amino acid sequences of 7 MIHs revealed that the deduced amino acid sequence had very high identity with amino acid sequences of MIHs of shrimps. The identities between the deduced amino acid sequence with that of MIH of Marsupenaeus japonicus, Penaeus monodon and Metapenaeus ensis were respectively 95.1%, 83.1% and 79.1%. On the base of all the data, we concluded that the 697 bp full-length cDNA was the cDNA encoding MIH precursor of F. chinensis. Sequence analysis of the 697 bp cDNA revealed a 312 bp open reading frame, and 81 bp 5' untranslated region, and a 302 bp 3' untranslated region. The deduced 103 amino acid polypeptide consisted of a 28 amino acid region of signal peptide and a 75 amino acid region of mature peptide. The six cysteine residues were very conserved in the mature peptide.