MOLECULAR-CLONING AND SEQUENCE-ANALYSIS OF STRIPED BASS (MORONE-SAXATILIS) GONADOTROPIN-I AND GONADOTROPIN-II SUBUNITS

Two types of cDNA, each encoding a different beta-subunit of striped b ass (Morone saxatilis, Teleostei) gonadotrophins (GTH-I beta and GTH-I I beta), as well as the glycoprotein alpha-subunit, were cloned by scr eening a striped bass pituitary cDNA library. The probes used for scre ening the library were cloned cDNA fragments, generated by PCR amplifi cation of reverse-transcribed mRNA obtained from two pituitaries. The nucleotide sequences of the alpha-subunit, GTH-I beta and GTH-II beta are 626, 524 and 580 bases long, encoding peptides of 117, 120 and 147 amino acids respectively. Striped bass GTH-I beta and GTH-II beta sha re a sequence identity of 48% at the nucleic acid level, and 30% at th e amino acid level. A cluster analysis of vertebrate pituitary glycopr otein beta-subunits suggests that teleost GTH-II beta is more closely related to tetrapod LH than to FSH. Administration of gonadotrophin-re leasing hormone analogue ([D-Ala(6),Pro(9)Net]-LHRH) to juvenile strip ed bass resulted in ten-, two- and fivefold increases in the expressio n of the alpha-subunit, GTH-I beta and GTH-II beta respectively. These results suggest that each of the GTH subunits is differentially regul ated, and further corroborate the functional duality of teleost gonado trophins. The nucleotide sequences of the alpha-subunit, GTH-I beta an d GTH-II beta reported in this paper have been deposited in the GenEMB L database with the respective accession numbers L35071, L35070 and L3 5096.