Abstract:

Overexpression of ppc gene in transgenic rice to improve photosynthesis and yield have brought extensive interest in the world. Many attempts have been made to transfer maize ppc gene to rice plants using genetic engineering techniques. But there was still a controversy on whether overexpression of PEPC could increase photosynthetic rates (P_n) in transgenic rice plants. We thought the different results were caused by the difference on materials, ppc gene inserting site and the measuremental circumstance. In order to validate our ideas, we repeated to introduce maize ppc gene into rice plants by Agrobacterium-mediated transformation and a lot of transgenic rice plants were obtained. PCR, Southern, Western analyse and PEPC activity detection indicated that the maize ppc gene was integrated into rice genome and expressed correctly and efficiently. The Pn was 27.3% higher in one transgenic line with the highest PEPC activity than in untransformed plants. The increase is at least in part due to the enhanced stomatal conductivity and higher internal CO₂ concentration. Nearly all the ppc transgenic rice lines showed higher Pn (up to 68.8%) than untransformed plants grown in dry field and full sunlight. Compared with that in appropriated conditions, the 6 transgenic lines showed higher Pn in stress condition. These results indicated that photosynthesis can be improved by introduction of PEPC into rice, especially in stress conditions.

Key words: Rice, Phosphoenolpyruvate carboxylase, Transgene, Photosynthesis