RNA interference (RNAi) of 2-Cys Prx gene enhances PSII photoinhibition but does not affect PSI activity in tobacco leaves under high-temperature stress

ABSTRACT This study aimed to evaluate the effects of 2-Cys Prx gene inhibition on photochemical reaction and reactive oxygen species (ROS) metabolism under high temperature (35°C) with low light (HT + LL) or high temperature with high light (HT + HL) in tobacco. The results showed that HT significantly increased the production of and H2O2 compared with CK (25°C). Particularly, the oxidative damage of RNAi plants was significantly greater than that of wild type (WT) under HT + HL treatment, possibly due to the inhibition of superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities. HT treatment inhibited the photosystem II (PSII) activity, and the oxygen evolution complex (OEC) was the main injury site. Notably, the photosystem I (PSI) activity of WT and RNAi plants did not change significantly under HT + LL treatment compared with CK. Although the PSI activity of WT and RNAi plants decreased significantly under HT + HL treatment, there was no significant difference between WT and RNAi plants. Collectively, these findings indicate that high light increases the photoinhibition of PSII and PSI and oxidative damage under high-temperature stress. The results also revealed that 2-Cys Prx plays a crucial role in alleviating oxidative damage and PSII photoinhibition under high-temperature stress in tobacco.