Cloning, expression analysis, and the photoperiodic response of CHH gene in Panulirus homarus

Abstract

Two subtypes of the Crustacean Hyperglycemic Hormone (CHH) gene and the cDNA of Panulirus homarus (PhCHHA and PhCHH-B) were been successfully cloned and characterized in this study. The length of PhCHH-A was 1186 bp with a 384 bp open reading frame that encodes a 127 amino acid. The length of PhCHH-B was 662 bp with a 394 bp open reading frame that encodes 131 amino acids. PhCHH-A and PhCHH-B possess most of the characteristics of eyestalk type-I CHH/MIH/GIH family neuropeptides. Both have a “signal peptide, CPRP, and mature peptide” structure. Their mature peptide comprised 74 amino acids and 6 cysteine residues in a conserved position. Homology and phylogenetic analysis showed that PhCHH-A and PhCHH-B were conserved in several functional domains. They showed the highest homology with CHH of Rock lobster (Jasus lalandii). Additionally, high levels of PhCHH-A transcripts were detected in both the intestine and eyestalks, where the expression of PhCHH-B was the highest in eyestalk. In female lobsters, PhCHH-A and PhCHH-B expression levelin eyestalk gradually increased with ovarian development. The photoperiod experiment results showed that ovarian development was optimal at 14 L:10D, and the expression levels of PhCHH-A and PhCHH-B in the eyestalk increased to the peak. In conclusion, these results indicate that PhCHH-A and PhCHH-B might play a critical role in the ovarian developmental cycle of P. homarus. In addition, a photoperiod of 14 L:10D had the most apparent effect on promoting the expression of PhCHH-A and PhCHH-B, and ovarian development.