ccaA and FBP/SBPase Derived From Cyanobacteria Improved Photosynthetic Capacity in Rice

Two cyanobacterial genes ccaA and FBP/SBPase related to CO2 hydration and Calvin cycle were induced into rice plants. Three homologous transgenic strains were generated with ccaA and FBP/SBPase alone or in combination independently and grown under field conditions. The biochemical, physiological, and leaf anatomic results indicated that stomatal and mesophyll conductance to CO2, net photosynthetic rate, carboxylation efficiency, and other physiological and biochemical parameters increased significantly in the overexpression strains with FBP/SBPase and CcaA + FBP/SBPase but not in the CcaA strain. Leaf anatomy structure showed no significant modifications between the transgenic and wild-type strains. The CcaA protein was shown to be located in the cytoplasm. These results showed that the effect on improving photosynthetic capacity by FBP/SBPase was better than by CcaA, and only when CcaA was co-transformed with FBP/SBPase was the synergistic effect observed. The multigene-stacking approaches and their synergistic action for improving the photosynthetic capacity in rice are discussed.