CDNA cloning and mRNA expression of growth hormone in Belontiidae (Anabantoidei suborder)

Abstract

Complete cDNA encoding for the growth hormone (GH) of the Belontiidae fish family (Anabantoidei suborder) was cloned by RACE PCR using several sets of degenerate oligonu- cleotides. GH cDNA of the pearl gourami (Trichogaster leeri; pgGH), cloned from the pituitary, included the 5’ and 3’ noncoding sequences of 44 bp and 181 bp, respectively, and consisted of 840 bp that encoded for a prehormone of 204 amino acid (aa) residues. GH cDNA of the blue gourami (T. trichopterus; bgGH) and its deduced aa sequence had the same lengths as those of the pgGH, with nucleotide and aa identities of 97% and 99%, respectively. GH cDNA cloned from the dwarf gourami (Colisa lalia; dgGH) differed from both pgGH and bgGH. The identity of the dgGH cDNA nucleotides was 88%, compared to pgGH and bgGH. However, the identity of the deduced dgGH aa sequence was 97% when compared to bgGH and 96% when compared to pgGH. Nucleotides of GH cDNA of the fighting fish (Betta splendens; ffGH) had an identity of 82% to those of pgGH and bgGH, and 81% to the dwarf gourami. Higher identity was found among the aa sequences than among the nucleotide sequences. The identity of the cloned aa ffGH compared to bgGH, pgGH, and dgGH was 93%, 92%, and 91%, respectively. Higher levels of GH mRNA were found in females in immature, vitellogenic, and mature stages than in males in various stages of gonadal development. No significant differences in the GH transcription level were found between immature and mature females and males. However, the mRNA level decreased significantly during sexual behavior in males. GH sequence and expression may be used as systematic markers for Belontiidae fish and possibly other fish.