cDNA CLONE AND SEQUENCE ANALYSIS OF PROOPIOMELANOCORTIN IN CHINESE STURGEON (ACIPENSER SINENSIS)

The Chinese sturgeon (Acipenser sinensis) is an endangered national protected species and also an important resource for sturgeon culture industry. However, only a few genes have been identified in this species. We report here the two subtypes of its proopiomelanocortin, POMC from a pituitary cDNA library of a 24 years old female Chinese sturgeon just after its spawning. Among all the 2025 EST clones, the AsPOMC-A and AsPOMC-B appeared 128 and 19 times, respectively. The nucleotide sequences of AsPOMC-A and AsPOMC-B are 1122 and 1216 bp in length, respectively, and encode for mature peptides both of 264 aa. The Chinese sturgeon POMC contains the segment corresponding to -melanocyte stimulating hormone (-MSH) (Y76-S97), adrenocorticotropic hormone (ACTH) (S140-I178), -lipotropic hormone (-LPH) (D181-E209), -melanocyte stimulating hormone, (-MSH) (AsPOMC-A: D212-D228; AsPOMC-B: G212-D228) and -endorphin (Y231-Q264), respectively. The phylogenetic tree of POMCs among Chinese sturgeon and other fishes was constructed by neighbour-joining method and maximum parsimony which indicated a divergence of the fish in Neopterygii and other fishes. The Chinese sturgeon POMCs showed greater sequence identity on average with ancient ray-finned fishes including acipenseriformes (89%-99%) and semionotiformes (70%) than with agnathan (31%-33%), elasmobranchii (40%-45%), chimaeriformes (33%-36%), and dipnoi POMCs (57%-63%). Interestingly, Chinese sturgeon POMCs showed obvious variety in sequence identity in teleostean (35%-70%). Furthermore, we analyzed their phylogenetic significance and suggested that AsPOMC-B might be an ancestral gene, and might play significant roles in reproduction regulation of ancestral fishes.