Cloning and expression analysis of 1-deoxy-D-xylulose-5-phosphate synthase gene from the medicinal plant Conyza blinii H.Lév.

Conyza blinii H.Lév. is a traditional Chinese medicinal plant that is distributed mainly in southwestern Sichuan and northern Yunnan. Its characteristic product is blinin, which has, among other properties, antigastric ulcer activity, and can serve as a qualitycontrol standard for such medicine. The problem is that C. blinii only produces low yields of blinin. As a diterpene, blinin is likely formed by the methylerythritol phosphate pathway. While 1-deoxy-D-xylulose-5-phosphate synthase (DXS) is the first rate-limiting enzyme in diterpenoid biosynthesis, it is a switch in the pathway. The DXS gene was successfully cloned and characterized from C. blinii by homologous cloning and rapid-amplification of cDNA ends (RACE). It was designated cbDXS and contains a 2190-bp open reading frame encoding 730 amino acids (aa), including a 17-aa signal peptide and a 713-aa mature protein. Semiquantitative RTPCR was used to determine the expression levels of cbDXS in different C. blinii tissues at the seedling stage. The corresponding blinin concentrations were also analyzed by high-performance liquid chromatography (HPLC). The cbDXS gene showed tissue specificity. Moreover, its expression levels were highly correlated to blinin concentrations. In summary, it is suggested that overexpression of this gene may increase flux toward blinin synthesis.