Molecular cloning, characterization and expression of FSH and LH beta subunits from grass carp (Ctenopharyngodon idella)

Follicle-stimulating hormone beta subunit (FSHβ) and luteinizing hormone beta subunit (LHβ) have been cloned and characterized from the pituitary of grass carp (Ctenopharyngodon idella). The full length of FSHβ and LHβ cDNA was 393 bp and 441 bp, with open reading frame encoding proteins of 130 and 146 amino acids, respectively. Phylogenetic analysis of the proteins of FSHβ and LHβ showed a high homology with other fishes. Homology analysis also indicated that LHβ has higher conservation than FSHβ. The expression analysis of grass carp FSHβ and LHβ by RT-PCR suggested that they were only expressed in the pituitary. Real-time quantitative PCR protocols were developed and validated to measure FSHβ and LHβ mRNAs during ovarian development. The FSHβ and LHβ mRNA level was very low in the pituitaries of early-pubertal fish and significantly increased during the ovulation period. These results suggested that in grass carp the gonadotropins synthesized synchronously in order for asynchronous oogenesis to take place.