RESUMO
Objective: To clone the full length cDNA encoding squalene synthase (SS) from Trichosanthes rubriflos and to carry on its sequence analysis, so as to lay the foundation for the further study on the positively selected sites and function correlation analysis of SS which is the key enzyme for triterpene synthesis pathway. Methods: According to the cDNA comparison on SS gene from Gynostemma pentaphyllum and Siraitia grosvenorii, 5'-upstream degenerate primers of the cDNA of SS gene from T. rubriflos were designed and the full length cDNA of SS gene from T. rubriflos was amplified by 3'RACE kit. Results: The full length cDNA of SS gene from T. rubriflos composed of 1 466 nucleotides was obtained. The open reading frame (ORF) of SS gene from T. rubriflos was 1 254 bp in length, corresponding to a predicted polypeptide of 417 amino acid residues. The results of homologous alignment analysis in GenBank demonstrated that the cDNA sequence of SS gene from T. rubriflos had 78%-94% similarity on the nucleotide sequence compared with SS from known plant and 74%-93% similarity on the deduced amino acid sequence compared with SS gene from other plants. Conclusion: The full length cDNA of SS gene from T. rubriflos has been cloned, which not only lays a foundation for the further study on the gene expression, gene structure, and gene mutation, but also provides the important data base for the association study between the positively selected sites and function correlation analysis of which is the key enzyme for triterpene synthesis pathway.