ROS Produced via BsRBOHD Plays an Important Role in Low Temperature-Induced Anthocyanin Biosynthesis in Begonia semperflorens

Low temperature (LT) is an important elicitor that triggers anthocyanin biosynthesis. To investigate whether the reactive oxygen species (ROS) produced via RBOH are involved in this process, we analysed the function and mechanism of ROS produced via RBOH during LT-induced anthocyanin biosynthesis in Begonia semperflorens Link & Otto. The results showed that BsRBOHD transcription was upregulated in LT-grown seedlings at the 3rd hour, which was followed by the upregulation of anthocyanin-biosynthesis genes at the 5–9th hour, leading to anthocyanin accumulation on the 2nd day. The LT-induced increases in ROS production, BsRBOHD and anthocyanin-biosynthesis gene transcription, and anthocyanin content were abolished by the pre-treatment of seedlings with DPI [an inhibitor of nicotinamide adenine nucleoside phosphorylase (NADPH) oxidase or DMTU (a H2O2 scavenger)], but were promoted by pre-treatment with NADPH (a substrate of NADPH oxidase). Changes in the chlorophyll fluorescence parameters showed that pre-treatment of DPI or DMTU alleviated the LT-induced decrease in the seedling chlorophyll content and a/b ratio, which subsequently alleviated the LT-induced decreases in the ABS/CSm, TRo/CSm, RC/CSm, ETo/CSm and REo/CSm values. In contrast, NAPDH pre-treatment intensified these changes. Therefore, we suggest that ROS produced via BsRBOHD may be involved in the LT-induced anthocyanin biosynthesis by strengthening the overaccumulation of ROS produced by the overexcitation of PSII reaction centres and overflux from $${\text{Q}}_{{\text{A}}}^{ - }$$ to NADP+ in B. semperflorens.