Gonadotropins beta-GtHI and beta-GtHII from the gilthead seabream, Sparus aurata

Full-length cDNA sequences encoding the beta-subunits of the gonadotrophins GtHI and GtHII were isolated, cloned, and sequenced from a single gilthead seabream (Sparus aurata) pituitary using RACE PCR. Beta-GtHI and beta-GtHII degenerate PCR primers were designed according to regions of high amino acid sequence homology between the chum salmon and the bonito beta-GtHI or beta-GtHII. DNA sequence analysis of the cloned PCR products confirmed the presence of the predicted complete coding region as well as 5' and 3' untranslated sequences. The deduced amino acid sequences of beta-GtHI and beta-GtHII from the gilthead seabream were compared to GtH sequences from a number of teleosts. Seabream beta-GtHI shows the highest homology to the bonito beta-GtHI (76%) and the striped bass (74%), while seabream beta-GtHII is 98% homologous to the yellow fin porgy, 87% homologous to the bonito, and 93% homologous to the striped bass beta-GtHII. Northern blot analysis showed the transcripts of the gilthead seabream beta-GtHI and beta-GtHII to be about 700 and 740 bases, respectively. During the spawning season, beta-GtHI is expressed at higher levels in males than in females while beta-GtHII is expressed at similar levels in both sexes.