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 (Fv/Fm, ϕPSII, and qP) 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. 以过表达磷酸烯醇式丙酮酸羧化酶(PEPC)的水稻为材料, 研究了不同程度干旱胁迫下开花期剑叶光合作用的光响应过程、叶绿素荧光参数、色素含量和活性氧代谢。结果表明, 在干旱特别是重度干旱胁迫下, 野生型水稻在强光下净光合速率迅速下降, 而转Zmppc基因水稻没有明显的下降现象; 而且表示光化学活性的叶绿素荧光参数Fv/Fm、ΦPSII和qP下降程度低, 说明PEPC增强了干旱胁迫下水稻抵御强光胁迫的能力。这可能是因为干旱胁迫下转Zmppc基因水稻玉米黄质含量高, 光系统对过剩光能的耗散能力强, 能够保护光系统免受过剩光能的伤害, 从而减小O2−产生速率; 同时干旱胁迫下转PEPC基因水稻抗氧化酶SOD、POD和CAT活性高, 能有效清除活性氧, 减轻膜质过氧化。