The role of UV-B radiation in modulating secondary metabolite biosynthesis and regulatory mechanisms in medicinal plants

The impact of UV-B (Ultraviolet-B) radiation is reviewed relative to the biosynthesis and regulation of secondary metabolites (SMs) in medicinal plants. Plants sense UV-B radiation through the photoreceptor UVR8, which is present as a dimer in the absence of UV-B and monomerizes upon UV-B exposure, interacting with proteins to regulate gene expression. In medicinal plants, UVR8-mediated signaling can regulate the activity of key enzymes, thereby affecting accumulation of secondary metabolites. For instance, in Arabidopsis thaliana, UVR8-mediated signaling regulates the expression of flavonoid biosynthesis genes. UV-B radiation influences the yield of SMs in medicinal plants, impacting the biosynthesis of phenolics, terpenoids, and alkaloids, though the effects vary under different UV-B conditions. Furthermore, UV-B radiation induces gene regulation in secondary metabolism, with most genes being upregulated. UV-B interacts with other stress factors, e.g. chromium, UV-A, water availability, and temperature, which affect the accumulation of secondary metabolites. However, these mechanisms are complex and require further investigation. Current research exhibits limitations, including uneven study coverage, a lack of standardized methodologies, and insufficient exploration of interactions between UV-B and other factors. Future studies should expand the research scope, adopt multifactorial approaches, and investigate molecular mechanisms, thereby advancing agricultural practices and the development of medicinal plants.