The full-length cDNA encoding growth hormone (PLGH) of Southern flounder (Paralichthys lethostigma) was cloned by Switching Mechanism At 5' end of the RNA Transcript (SMART) RACE. The sequence was 902 nucleotides long, coding a polypeptide of 190 amino acids and a signal peptide of 17 amino acids. The 5' and 3' UTR of the messenger RNA were 131 and 198 nucleotides long respectively. After alignment of the deduced amino acid sequence with other Pleuronectiformes species, a consecutive absence of 14 amino acids segment in the C-terminal was found in all three species of Paralichthyidae. It can be proved that GHs of Paralichthyidae have the shortest length in Pleuronectiformes species. Homology analysis of PLGH cDNA showed the highest score with Paralichthys orbignyanu and the lowest score with Solea senegalensis. The phylogenetic analysis on complete GH ORF sequences was performed with the maximum parsimony method. In the topology founded, the species fell into three groups: Soleoidei, Paralichthyidae and Pleuronectidae. The exclusive species of Soleoidei selected in this work, Solea senegalensis formed an independent branch and showed relatively high mean difference with Paralichthyidae and Pleuronectidae. The results of phylogenetic analysis based on the GH ORF sequences were consistent with the earlier results based on 12S, 16S rDNA and mitochondrial DNA sequences within Pleuronectiformes species, which would suggest the potential credible application of GH ORF sequences in Pleuronectiformes phylogeny.

The full-length cDNA encoding growth hormone (PLGH) of Southern flounder (Paralichthys lethostigma) was cloned by Switching Mechanism At 5' end of the RNA Transcript (SMART) RACE. The sequence was 902 nucleotides long, coding a polypeptide of 190 amino acids and a signal peptide of 17 amino acids. The 5' and 3' UTR of the messenger RNA were 131 and 198 nucleotides long respectively. After alignment of the deduced amino acid sequence with other Pleuronectiformes species, a consecutive absence of 14 amino acids segment in the C-terminal was found in all three species of Paralichthyidae. It can be proved that GHs of Paralichthyidae have the shortest length in Pleuronectiformes species. Homology analysis of PLGH cDNA showed the highest score with Paralichthys orbignyanu and the lowest score with Solea senegalensis. The phylogenetic analysis on complete GH ORF sequences was performed with the maximum parsimony method. In the topology founded, the species fell into three groups: Soleoidei, Paralichthyidae and Pleuronectidae. The exclusive species of Soleoidei selected in this work, Solea senegalensis formed an independent branch and showed relatively high mean difference with Paralichthyidae and Pleuronectidae. The results of phylogenetic analysis based on the GH ORF sequences were consistent with the earlier results based on 12S, 16S rDNA and mitochondrial DNA sequences within Pleuronectiformes species, which would suggest the potential credible application of GH ORF sequences in Pleuronectiformes phylogeny.