Effects of UV-B on the activity and gene expression of several antioxidant enzymes in peppermint (Mentha x piperita L.)

Peppermint infusion is a popular herbal drink with a number of benefits on cardiovascular, digestive, respiratory systems. Recent researches demonstrated that ultraviolet radiation can have an effect on peppermint essential oil. Considering the actual increasing of UV-B in the sun radiation, it’s important to estimate real conditions and which economic consequences it may have. Mentha x piperita L. plants grown in field were irradiated for one hour with UV-B light (310 nm, 3.8 Wm-2), in the middle of the day, for two days. The five upper leaves were collected at 4, 20, 24, 28, 44 and 48 h after the first treatment. Plants of M. x piperita cultivated under the same circumstances without the treatment were utilized as the control at each time point. Results showed that the biosynthesis of peppermint essential oil is modulated by UV-B irradiation, but the plants have also their mechanisms of protection from UV by increasing the ROS-scavenging enzymes activity. Also, expression of some involved genes in pathway modified in the presence of UV and showed regulating effect in essential oil biosynthesis significantly. Another confirmation of the protection from UV-B light was the stable concentration of photosynthetic pigments. Analysis of ROS-scavenging enzymes suggests that plants had an oxidative stress. In conclusion, this work is a one step to understand the regulation of terpenoid biosynthesis and the effects of UV-B radiation on it. Complex analysis of whole plant’ response will be helpful for this aim.