Light-Regulated Growth, Anatomical, Metabolites Biosynthesis and Transcriptional Changes in Angelica sinensis

<i>Angelica sinensis</i> is an alpine medicinal plant that has been widely used as a general blood tonic and gynecological indications over 2000 years, which depend on the bioactive metabolites (e.g., volatile oils, organic acids, and flavonoids). Although the accumulation of these metabolites is significantly affected by the environmental factors (e.g., altitude, temperature, and sunshine) as found in previous studies, the regulatory mechanism of different lights has not been clearly revealed. Here, growth parameters, contents of bioactive metabolites, and expression levels of related genes were examined when <i>A. sinensis</i> was exposed to different white-light (WL) and UV-B radiation treatments. The results showed that the differences in growth parameters (e.g., plant height, root length, and plant biomass) and leaf tissue characteristics (e.g., leaf thickness, stomatal density and shape, and chloroplast density) were observed under different light treatments. The contents of Z-ligustilide and ferulic acid elevated with the increase of WL (50 to 150 µmol·m²/s) and maximized under the combination of WL-100 and UV-B (107 µW/m², UV-107) radiation, while the total flavonoids and polysaccharides contents, as well as in vitro antioxidant capacity, elevated with the increasing of WL and UV-B. mRNA transcripts encoding for the biosynthesis of volatile oils, ferulic acid, flavonoids, and polysaccharides were found to be differentially regulated under the different WL and UV-B treatments. These morphological, anatomical, and transcriptional changes are consistent with the elevated bioactive metabolites in <i>A. sinensis</i> under the combination of WL and UV-B. These findings will provide useful references for improving bioactive metabolite production via the cultivation and bioengineering of <i>A. sinensis</i>.