P. lobata roots have been utilized to prevent cardiovascular diseases in Chinese traditional medicine, attributed to the presence of an isoflavone C-glucoside, puerarin (daidzein 8-C-glucoside). Interestingly, puerarin is biosynthesized only in P. lobata plant, and is not found in any other plant species, indicative of unique biosynthetic enzymes in this plant. However, the knowledge regarding how the C-glucosylation is formed in the pathway to puerarin remains scant.
Under the supervision of Prof. ZHANG Yansheng from Wuhan Botanical Garden, WANG Xin and LIChangfu started a research on the P. lobata plant.
Puerarin accumulates mostly in the P. lobata roots, and therefore the root-specific glycosyltransferases fall into the focus of the study. More than one hundred glycosyltranserase genes have been isolated from P. lobata plant with 22 genes showing preferential expressions in its roots. One gene, donated as PlUGT43, has been found to be involved in puerarin biosynthesis, and its encoded enzyme showed the activity of converting daidzein to puerarin. The PlUGT43 gene and its homologs have not been found in other plant species including legumes other than P. lobata plant. This data may explain why puerarin is biosynthesized only in P.lobata plant. Interestingly, when the PlUGT43 gene was manually transferred to soybean plant, the production of puerarin was detected in transgenic soybean roots.
With the development of synthetic biology, the discovery of PlUGT43 would pave the way to produce puerarin in microorganisms by metabolic engineering.
This research was funded by the Natural Science Foundation of China. The results have been published in Plant Journal entitled “Molecular characterization of the C-glucosylation for puerarin biosynthesis in Pueraria lobata”.
Recombinant PlUGT43 catalyzes the C-glucosyltransferase reactions with daidzein and genistein (Image by Prof. ZHANG)