GIH CDNA Cloning And Mrna Expression In Litopenaeus Vannamei

Gonad-inhibiting hormone (GIH) is one of the important neuropeptide hormones which are secreted by X-organ-sinus gland (XO-SG) complex. It inhibits gonadal development, molting and secretion of MF (methyl farnesoate) in both males and females. The GIH partial cDNA sequences were isolated from the eyestalks of Litopenaeus vannamei by RACE. Structure of the predicted GIH protein was analyzed by bioinformatics. Expressions of GIH mRNA were examined using semi-quantitative RT-PCR in eight stages (fertilized eggs, nauplius, zoea, mysis, 25d juveniles, 30d juveniles, 35d juveniles, and 40d juveniles) and different tissues in adult males and females (muscles, brains, eyestalks, stomach and intestine, gills, heart, ovaries and testes). Expressions of GIH were also examined in eyestalks of female L. vannamei following the immersion treatment with nonylphenol (NP, 100μg/L and 0.01μg/L). Results showed that the GIH partial cDNA was 683 bp in length, and the 3'un-translated region (3'UTR) were 518 bp with a potential polyadenylation signal AATAAA located at 15bp upstream of the poly (A) tail. The open reading frame (ORF) was 162 bp, and sequence of predicted 54 amino acids recidues was encoded. Four conserved Cys residues were found in GIH partial peptide in L. vannamei, which was a common characteristic in CHH family. The L. vannamei GIH shared a highest amino acid identity of 96% with Penaeus monodon and 72% with metapenaeus ensis. Expressions of L. vannamei GIH were found in fertilized eggs, larvae and juveniles with the highest mean (0.936±0.021) at the 35d juveniles, which had a significant difference compared with that of other stages (P<0.05). There were significant different GIH expressions between larvae and fertilized eggs (P<0.05), and higher in the former but lower in the later. Similar situation appeared between larvae and juveniles (P<0.05), and higher in larvae but lower in juveniles. Expressions of L. vannamei GIH were not found in the examined tissues except in eyestalks and brains, which indicated that GIH was related to the neural activities in L. vannamei. Nonylphenol inhibited the expressions of GIH in a dose-dependent manner in the eyestalks of female L. vannamei, but no significant difference were found between the control and the NP-treated L. vannamei (P>0.05).