转玉米C_4光合酶基因水稻株系中的光合C_4微循环

Photosynthetic C_4-Microcycle in Transgenic Rice Plant Lines Expressing the Maize C_4-Photosynthetic Enzymes

用转PEPC、PPDK、NADP ME、PEPC +PPDK等酶基因的水稻株系及原种野生型 (WT)为材料 ,研究了不同基因型水稻叶片中的C4光合微循环及其功能。用外源OAA或MA饲喂叶切片或离体叶绿体后 ,光合放氧速率在野生型水稻中增加了 5 0 % ,在NADP ME 和PPDK 转基因水稻中增加了 5 0 %～ 5 4 % ,在PEPC 和PEPC +PPDK 转基因水稻中增加了10 0 %～ 15 0 %。证明原种水稻Kitaake叶片中具有一个原初的和有限的C4光合微循环 ,除PPDK基因、NADP ME基因外 ,外源PEPC基因或PEPC +PPDK双基因导入原种水稻Kitaake后 ,可大幅度提高C4光合微循环的运行。水稻中C4光合微循环的增强有降低光呼吸速率 (Pr)、增加净光合速率 (Pn)的作用 ,在光能利用上 ,可增加PSⅡ光化学效率 (Fv/Fm)、光化学猝灭 (qp)、降低非光化学猝灭 (qN)的作用 ;

Photosynthetic C 4 microcycle and its function in photosynthetic apparatus were explored by comparing the transgenic rice lines expressing the maize C 4 specific PEPC gene, PPDK gene, NADP ME gene and PEPC+PPDK double genes with their wild type rice Kitaake. The activities of photosynthetic C 4 pathway related key enzymes, PEPC, NADP ME, PPDK were detected in both wild type rice Kitaake and transgenic rice. Photosynthetic oxygen evolution rates of leaf segments or intact chloroplasts in vitro fed with oxaloacetate (OAA) or malate (MA) increased by 50% in wild type rice Kitaake, by 50%-54% in NADP ME and PPDK transgenic rices (no significant difference with wild type rice Kitaake), by 100%-150% in PEPC and PEPC+PPDK transgenic rices, which indicated that there was a primitive and limited photosynthetic C 4 microcycle in wild type C 3 rice Kitaake, and heterogenous PEPC gene and/or PEPC+PPDK double genes, with the exception of PPDK gene and NADP ME gene, from C 4 plant could enhance the operation of existed C 4 microcycle in C 3 transgenic rice Kitaake. As the photosynthetic C 4 microcycle enhanced, the rates of photorespiration ( P r) were lowered and the net photosynthetic rates increased by determining the CO 2 exchanging rates, and as a consequence, PSⅡphotochemical efficiency ( F v/ F m) and photochemical quenching ( q p) increased accompanied with a decrease in the non photochemical quenching ( q N) by determining the chlorophyll fluorescence characteristics. Above results might offer the experimental evidences for photosynthetic efficiency raising gene engineering of rice.