Promotive Effect of ATP on Photosynthesis and Photooxidation in Transgenic Rice Expressing PEPC, PPDK and ME Enzyme Genes

Untransformed rice (WT) and transgenic rice containing maize phosphoenolpyruvate (PEPC), pyruvate orthophosphate dikinase (PPDK), and NADP-malic enzyme (ME) genes were studied. In addition, the activity of C-4 photosynthetic enzymes, photosynthetic response to light/temperature and the metabolic index of active oxygen were also measured and analyzed. The activities of C-4 photosynthetic enzymes in WT were very low, while those of corresponding enzymes in transgenic rice with PEPC, PPDK, and ME genes (PKM) were highly expressed. Under the conditions of high light intensity and high temperature, the photosynthetic rate of PKM after adenosine triphosphate (ATP) treatment increased by 15.7% and 13.3%, respectively, as compared with that without ATP treatment. The photosynthetic rate of PKM after ATP treatment was similar to that of maize, accounting for 80.7%. Moreover, its tolerance against photooxidation was enhanced. The photosynthetic productivity of PKM after ATP treatment was improved. This demonstrates that ATP is the key factor in enhancing photosynthetic capacity in transgenic rice containing C-4 genes. These results provide a new technical approach for rice breeding with high photosynthetic efficiency.