Proteomic analysis of Morus leaf epidermis indicates the roles of photosystems and ROS in UV-B response

Abstract

The epidermis is the first layer of cells on leaves that receive UV-B radiation and the place where guard cells distribute. Their stress response mechanism was different from the mesophyll. However, there has been little research on leaf epidermis. To assess the response mechanism of epidermis to UV-B radiation, tissue-specific proteomics were performed on the epidermis of Morus leaf under UV-B radiation and UV-B radiation following dark incubation. A total of 935 proteins were identified and quantified. Changes of proteins involved in light reaction and Calvin cycle were not simultaneous. Antioxidant enzymes showed different patterns. And the contents of H2O2 and Ca2+ were increased after treatments. A UV-B radiation response mechanism of epidermis was proposed based on these results, in which photosystems perceives the stimulus of UV-B radiation to produce reactive oxygen species, and then the antioxidant system and protein homeostasis system were induced through the Ca2+ crosstalk with reactive oxygen species signaling pathway.