Transcriptomic analyses reveal dynamic changes of defense response in Glycyrrhiza uralensis leaves under enhanced ultraviolet-B radiation

Abstract

The amount of solar ultraviolet-B (UV-B) radiation reaching the Earth's surface is increasing due to stratospheric ozone dynamics and global climate change. Increased UV-B radiation poses a major threat to ecosystems. Although many studies have focused on the potential effects of enhanced UV-B radiation on plants, the dynamic changes of defense response in plants under continuous UV-B radiation remains enigmatic. In this study, we investigated the effect of UV-B radiation at 0.024 W/m² on the UVR8-and reactive oxygen species (ROS-) signaling pathways, antioxidant system, and wax synthesis of G. uralensis. These parameters were investigated at different UV-B radiation stages (2 h, 6 h, 12 h, 24 h, 48 h, and 96 h). The results revealed that the uvr8 expression level was significantly repressed after 2 h of UV-B radiation, partly because G. uralensis rapidly acclimated to UV-B. Significant H₂O₂ accumulation occurred after 12 h UV-B radiation, resulting in activation of the ROS signaling pathway and the antioxidant system. After 24 h of UV-B radiation, wax synthesis was enhanced alongside a decrease in the capacity of the main antioxidant system. The dynamic and ordered changes in these pathways reveal how different strategies function in G. uralensis at different times during adaption to enhanced UV-B radiation. This study will help us better understand dynamic changes of defense response in plant under enhanced UV-B radiation, further providing fundamental knowledge to develop plant resistance gene resources.

Keywords: Antioxidase system; ROS signal Pathway; UV-B radiation; UVR8 signal pathway; Wax synthesis.