Four different Sox genes in Amur sturgeon Acipenser schrenckii and five Sox genes in chum salmon Oncorhynchus keta were identified for the first time in this paper, and there was no sexual difference for these genes in these two fishes. For Amur sturgeon, the encoded amino acid sequences exhibited 98%, 98%, 98%, 86% of sequence homology with those reported for human SOX HMG box, respectively, and for chum salmon, the encoded amino acid sequences exhibited 93%,98%,98%,98%,96% of sequence homology with those reported for human SOX HMG box, respectively. Two different forms of Sox9 gene in chum salmon were found, and Sox9 contained a 303 bp and 258 bp introns in the HMG box for chum salmon respectively while 572 bp for Amur sturgeon. No clear similarity was observed between the introns in the Sox9 HMG box of different fishes, but the introns occur in the HMG box region between the second and third bases of the codon for arginine at residue 42 in HMG box for the three fishes, and obey the rule of “GT AG”. and the encoded amino acid sequences in the three Sox9 genes HMG box are very conservative in the two fishes (100% identification). Identification of these genes is a potential step in understanding development regulations including sex determination in Amur sturgeon.
