Analysis of sequence characterization and spatiotemporal expression pattern of goat gene in bighead carp（Hypophthalmichthys nobilis）

【Objective】The purpose of the study was to investigate the sequence characterization and spatiotemporal expression pattern of ghrelin O-acyltransferase(goat)gene of bighead carp(Hypophthalmichthys nobilis), and to analyze the potential biological functions of goat gene. 【Method】The full-length sequence of goat gene cDNA was obtained using the RACE amplification,and its expression characteristics in early developmental stages, different tissues and four tissues(brain,intestine,muscle and liver)in summer and winter were detected by real-time fluorescence quantitative PCR(qRTPCR). The distribution of the goat gene in the intestine tissue was characterized through in situ hybridization and immunocytochemistry at the gene and protein levels, respectively. Moreover, co-expression patterns of goat gene and pathwayrelated genes were assessed by qRT-PCR. 【Result】The cDNA sequence of the goat gene was identified as 2255 bp in length, with an open reading frame(ORF) of 1116 bp, encoding 371 amino acids residues. The deduced amino acid sequence contained seven transmembrane regions and contained asparagine(the 251^st position) and histidine(the 282nd position), which were involved in catalysis. Homology analysis revealed that goat gene of bighead carp was very similar to that of Cypriniformes species. The goat gene expression levels at the time of early hatching stage and 5 d after membrane emergence were significantly higher than those at other periods(P<0.05, the same below). Differential expression analysis of adult tissues found that goat gene expression was the highest in the intestine. The goat gene expression in brain, intestine and muscle tissues was significantly higher in summer than in winter. Furthermore, in situ hybridization experiments revealed that goat gene was expressed with a strong signal in the intestine,and immunohistochemistry in intestinal sections showed the presence of positive signals of GOAT co-localized with GHRL in the intestinal mucosa. There was a co-expression relationship between goat gene and related genes in the synthesis, secretion and action pathway of growth hormone(ko04935). 【Conclusion】The goat gene has the typical structural characteristics of MBOAT family and may participate in biological processes such as bighead carp feeding regulation,growth and metabolic adaptation by cooperating with feeding-related genes(ghrl, etc.).