Cloning and characterization of CbHMGR and CbSQS genes in Conyza blinii.

Conyza blinii H.Lév. is a traditional medicine for the treatment of bronchitis cough. Triterpene saponins (conyzasaponins) are major pharmacological components in C. blinii. Here, two C. blinii genes coding for the important regulatory enzymes of the conyzasaponins biosynthetic pathway, 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) and squalene synthase (SQS), were cloned and characterized. The open reading frames of CbHMGR and CbSQS were 1740 bp and 1257 bp in length, respectively. Gene structure display server analysis revealed that there were four introns in the gDNA of CbHMGR and no intron in the gDNA of CbSQS. The analyses of their deduced amino acid sequences showed that these two genes had the typical domains shown in homologous proteins. The phylogenetic relationship between the two genes and their homologous genes were consistent with their natural evolution. The GCMS results of enzymatic activity assays showed that CbHMGR catalysed the formation of mevalonate from HMG-CoA. CbSQS catalysed the synthesis of squalene with farnesyl diphosphate as a substrate. These findings will provide a sound base for further research on the conyzasaponins biosynthetic pathway and may have applications in the synthetic biology of conyzasaponins production. [ABSTRACT FROM AUTHOR]