玉米C_4光合酶基因导入对拟南芥光合特性及抗旱性的影响

为了解玉米C_4型光合酶基因对C3植物拟南芥光合特性的影响及其对干旱胁迫的响应,分别以过表达ZmPEPC(磷酸烯醇式丙酮酸羧化酶)、ZmPPDK(丙酮酸磷酸二激酶)和ZmNADP-ME(依赖于NADP的苹果酸酶)单个酶基因的拟南芥株系(分别简写为PC、PK、ME),以及过表达PEPC+PPDK和PPDK+NADP-ME两个酶基因的拟南芥株系(分别简写为PCK、PKM)为供试材料,在开花期停止浇水,并分别于干旱胁迫处理前1天、第5天、第10天和结束干旱胁迫复水处理5d时测定转基因拟南芥中目标基因的表达量、光合速率、水分利用效率和酶活性。结果表明,在正常生长条件下,PCK类型株系的PEPC酶活性、PPDK酶活性、净光合速率(Pn)以及水分利用效率(WUE)较野生型拟南芥分别高52%、20%、24%和55%,除PPDK酶活性外,PCK类型株系各指标测定值的增幅均高于其他转基因类型株系,综合表现最优。不同类型株系的上述测定指标总体表现为PCKPCPK、PKMME。干旱胁迫处理5d时,各类型株系中目标基因的表达量、光合酶活性、Pn和WUE均有所上升。干旱胁迫处理10d时,拟南芥受到严重损伤,上述指标的测定值均下降。复水5d时上述指标得到不同程度的恢复,不同类型转基因株系的各项测定指标在不同干旱胁迫处理中总体仍表现为PCK最优,PC次之。各转基因株系均优于受体非转基因拟南芥。

Effect of Maize C4-specific Photosynthesis Genes on Photosynthesis and Drought Resistance of Arabidopsis thaliana

The three key C4-specific photosynthesis genes of maize,ZmPEPC,ZmPPDK and ZmNADP-ME,hold great promise for increasing photosynthetic rate of C3 type plants.To investigate the effects of overexpression of those C4-specific photosynthesis genes on photosynthetic rate and drought tolerance of C3 plants,we obtained Arabidopsis thaliana plants overexpressing ZmPEPC (phosphoenopyruvate carboxylase),ZmPPDK (pyruratedikinase),ZmNADP-ME (NADP-malic enzyme),ZmPEPC+ZmPPDK,and ZmPPDK+ZmNADP-ME,respectively,using agrobacterium mediated transformation.Wild type and transgenic Arabidopsis plants were firstly grown under well-water conditions and then under drought stress at flowering stage by stopping watering.Samples were collected at 1 d before water stress,5 d and 10 d after water stress,and 5 d after rewatering to analyze the relative expressions of transgenes,the enzymic activities of PEPC,NADP-ME and PPDK,net Photosynthetic rate(Pn) and water use efficiency(WUE).The results showed that the activities of PEPC and PPDK,Pn and WUE of the ZmPEPC+ZmPPDK transgenic plants were 52%,20%,24% and 55% higher than those of wild-type under normal water condition,respectively.The ZmPEPC+ZmPPDK transgenic plants had the largest increase in these parameters,except PPDK activity,compared to the plants with other transgenes.Based on the above measured parameters,the performances of the different transgenes can be ranked as ZmPEPC+ZmPPDK>ZmPEPC>ZmPPDK,ZmPPDK+ZmNADP-ME>ZmNADP-ME.All the measured parameters in the transgenic Arabidopsis leaves increased compared with their non-stressed controls at 5 d of drought stress,and decreased at 10 d of drought stress due to severe damage by drought,but were recovered in various degrees at 5 d after watering restored.Overall,ZmPEPC+ZmPPDK transgenic plants had the highest increase in these measured parameters under different drought stress conditions,and ZmPEPC transgenic plants were as the second.All transgenic Arabidopsis plants with different transgenes showed better drought tolerance than the wild type control.