Genome sequence analysis and expression of two CHH genes in tiger shrimp (Penaeus monodon)

Two genes encoding crustacean hyperglycemic hormones, named as PmCHH and PmHHLPP, were found in tiger shrimp (Penaeus monodon). In the analysis of genomic sequence, a typical domain of CHH-I gene called CPRP (CHH precursor-related peptide) was found between the signal and the mature peptides in these two genes, and all aligned sequences shared a homogeneous structure of genome. They were alike other CHHs when being blasted in the NCBI. The similarity was over 50% and the maximum was 99%. Besides, PmCHH and PmHHLPP were clustered with the non-CHH-I genes in the phylogenetic analysis. The bioinformatics analysis of their sequences predicts that the transcription initiation site "A" as well as its core promoter region in both genes located at 99 bp and 190 bp upstream of the ORF (open reading frame), and both had four α-helices in the predictive proteins. The expression analysis of different tissues and larval development of P.monodon provides evidence that PmCHH and PmHHLPP could not be easily identified as hyperglycemic genes: the highest expression level was detected in gut, while they expressed low in tissues regulating blood glucose, hepatopancreas and muscle. For the larval development, the stages of Nauplius Ⅲ-Ⅳ, Zoea Ⅰ and Mysis witnessed the peaks and declines of the expression of both genes, which seemed irrelevant to glycemic regulation. In conclusion, PmCHH and PmHHLPP could be identified as members of the CHH family according to their CHH-I like structure.