High Light Tolerance is Enhanced by Overexpressed PEPC in Rice Under Drought Stress

Overexpression of phosphoenolpyruvate carboxylase (PEPC) gene in transgenic rice (Oryza sativa L.) may alleviate inhibition on photosynthesis under drought stress condition. In the present research, photosynthetic light curve, chlorophyll α fluorescence parameters, pigment content, and reactive oxygen metabolism were studied in 2 PEPC transgenic rice lines under drought stress at flowering stage. The results showed that under drought stress, especially severely drought stress, net photosynthetic rate decreased dramatically under high photosynthetic active radiation (PAR) in untransformed wild type rice, while maintained unchanging in the PEPC transgenic lines under high PAR higher than 1200 μmol m⁻² s⁻¹. The photochemistry activities (F_v/F_m, ϕ_PSII, and q_P) decreased slightly under drought stress in both PEPC transgenic lines. These results indicated that PEPC enhanced the photoinhibition tolerance of rice under drought stress. The increased zeaxanthin content in leaves of the PEPC transgenic rice lines dispersed more light energy as heat under drought stress, thus decreased the producing rate in photosystem II. At the same time, the activities of superoxide dismutase, peroxidase, and catalase were higher in the PEPC transgenic rice plants than the untransformed wild type under drought stress. These enzymes could effectively diminish the reactive oxygen species and reduce the membrane lipid peroxidation.