Effect of UV-B radiation on growth, flavonoid and podophyllotoxin accumulation, and related gene expression in Sinopodophyllum hexandrum.

Sinopodophyllum hexandrum is an alpine medicinal plant that produces the anticancer compound podophyllotoxin (PPT). Although a positive relationship between PPT content and altitude has been proved and low temperature enhances plant growth and PPT accumulation has also been revealed, the role of UV radiation in regulating growth and PPT accumulation is still unclear In this study, morphophysiological traits, metabolites content and related genes expression were investigated by exposing S. hexandrum seedlings to treatment with UV-B radiation. The results showed that the contents of soluble sugars and flavonoids, and the expression levels of genes involved in glycometabolism (XET and β-1,3-glucanase) and flavonoid biosynthesis (PAL,C4H,4CL,CHS1 and DTX41) were enhanced in response to UV-B compared to CK. Moreover, genes involved in stress tolerance (MYB, WRKY,APX3 and EX2) were also upregulated in response to UV-B radiation. Although the whole plant biomass exhibited slightly increased values that depended largely on root development, the contents of chlorophyll and PPT and the expression levels of genes involved in photosynthesis (matK, ndhF,rbcL and ycf5) and PPT biosynthesis (C3H,CCoAMT,CCR,CAD, DPO, PLR,SDH, CPY719A23,OMT3,CYP71CU1,OMT1and 2-ODD) were significantly decreased in response to UV-B compared to CK. It can be concluded that UV-B radiation promotes soluble sugars and flavonoids accumulation, but inhibits PPT biosynthesis in S. hexandrum.