ISOLATION AND CHARACTERIZATION OF A CDNA FOR GONADOTROPIN II-BETA OF PACIFIC HERRING, AN ANCIENT TELEOST

The purpose of the study was to identify the pituitary hormone that co ntrols reproduction in Pacific herring Clupea harengus pallasi, a basa l teleost lineage. A complete complementary DNA (cDNA) encoding herrin g gonadotropin (GtH) II-beta protein is presented. The cDNA encodes a signal peptide of 24 amino acids and a GtH polypeptide of 149 amino ac ids. The identity of the herring molecule as GtH II-beta is based on 1 2 conserved cysteine residues, an N-glycosylation site, and a teleost- specific CSGH sequence, thought to be similar to the CAGY motif of mam malian LH-beta. Unlike other early evolving teleosts (Anguilliformes, Salmoniformes, Cypriniformes, Siluriformes), the amino terminus of the mature herring GtH II-beta hormone begins with phenylalanine, more ty pical of lineages that appeared much later (Cyprinodontiformes, Percif ormes). Phylogenetic analysis of LH, FSH, and fish GtH II- and I-beta subunits shows that groups of GtH II-beta subunits of closely related fish species form distinct sister clades to each other and to a clade containing LH, FSH, and fish GtH I-beta. This result suggests that the beta subunit of both LH and FSH may have evolved from the lineage of fish GtH I-beta rather than that of GtH II-beta. (C) 1997 The Fisherie s Society of the British Isles.