Abstract: Paired box gene 7（PAX7）is crucially important to the cellular renewal, differentiation and apoptosis, especially in neural crest development, gastrulation, and muscle self-renewal. The PAX7 domains sequence is conserved among several species, such as zebrafish, apteronotidae, and rainbow trout, and the conserved sequence zebrafish was used to design degenerate primers for reverse-transcription PCR（RT-PCR）. A partial sequence of PAX7 from grass carp was obtained for a 645 bp segment encoding a 214 amino acid peptide, containing a paired box domain with 128 amino acids. The deduced protein showed homology to zebrafish（Danio rerio）, apteronotidae（Sternopygus macrurus）, Japanese Medaka（Oryzias latipes）, gilthead bream（Sparus aurata）, rainbow trout（Oncorhynchus mykiss）, Atlantic salmon（Salmo salar）, Arctic charr（Salvelinus alpinus）, human（Homo sapiens）, wild yak（Bos grunniens mutus）, brown rat（Rattus norvegicus）, and mouse（Mus musculus）with 90%-97% identities. Analysis of the PAX7 phylogenetic tree revealed that the grass carp joined with zebrafish, and there was a confluence of Japanese medaka, Arctic charr, Atlantic salmon, rainbow trout, apteronotidae and gilthead bream. The other branch was consisted of mouse, brown rat, wild yak and human. These results conformed to the traditional species classification evolution status. The expression in tissues was detected by Real-time quantitative PCR, which indicated that the highest level of PAX7 gene expression was found in muscle, a lower expression level was found in foregut and skin, and the lowest detectable level was found in heart, brain, kidney and liver. The results are in agreement with the function of the gene.

Key words: PAX7 gene , Grass carp, （Ctenopharyngodon idellus） , Sequence analysis Tissue differential expression