Overexpression of Phosphoenolpyruvate Carboxykinase Increases Photosynthetic Efficiency and Salt Tolerance in Rice

Salinity stress is one of the major obstacles to glycophytic crop production worldwide, including rice. It alters cellular metabolism, causing significant crop destruction that results in substantial reductions in yield. The overexpression of C₄ enzymes, such as phosphoenolpyruvate carboxykinase (PEPCK), at high levels in C₃ transgenic plants through genetic engineering can decrease oxidative stress while increasing photosynthetic capabilities. In this research, we evaluate the efficiency of transgenic rice plants (Oryza sativa L. cv. IR64) overexpressing PEPCK genes in mitigating salinity stress and increasing photosynthetic efficiency. The T1 transgenics showed increased levels of several biochemical factors, including ascorbate peroxidase (APX), catalase (CAT), proline, glutathione reductase (GR), and guaiacol peroxidase (GPX) activities. This was accompanied by reduced levels of malondialdehyde (MDA), hydrogen peroxide (H₂O₂), and electrolytic leakage, suggesting an effective antioxidant defense mechanism against the oxidative damage driven by salt stress. Photosynthetic parameters-such as chlorophyll content, net photosynthetic rate, intercellular CO₂ content, and stomatal conductance-were elevated in transgenic plants compared to control plants. The transgenics also exhibited superior agronomic characteristics. Our findings provide conclusive evidence of the PEPCK gene's potential role in regulating salt stress response and tolerance in rice plants.