Integration of C4-specific ppdk gene of Echinochloa to C3 upland rice and its photosynthesis characteristics analysis

Pyruvate orthophosphate dikinase (PPDK) plays a key role in C4 photosynthetic pathway. The enzymatic reaction is one of the rate-limiting steps of the C4 photosynthetic pathway. In this paper, the gene encoding Echinochloa pyruvate orthosphate dikinase (GenBank accession number: AB289641) was introduced into H65, a upland rice variety, using an Agrobacterium-mediated system. Southern hybridization, Northern hybridization and enzyme activity determination all confirmed the effective expression of Echinochloa C4 type PPDK in upland rice with the enzyme activity being elevated 1 - 11 folds. However, no appreciable change demonstrated in carbon assimilation of the transgenic upland rice though increased photoinhibition was noted under high light intensity.