导入外源玉米C_4型NADP-ME基因对小麦光合效能的影响

Photosynthetic Characteristics of Transgenic Wheat Expressing Maize C_4-Type NADP-ME Gene

为研究玉米C_4型NADP-ME基因对小麦光合特性的影响,以T_3代转NADP-ME基因小麦株系10T(9)-1-1和10T(9)-225-4及其对照周麦23为试材,进行了分子特征鉴定、光合生理特性分析和单株产量性状调查,并对其作用机制进行了初步解析。结果表明,外源基因已整合到转基因小麦的基因组中,并能正确转录和翻译;与对照周麦23相比,两个转基因株系在4个测定时期旗叶NADP-ME酶活性均明显提高,而旗叶净光合速率(P_n)则明显下降;尤其在花后第7天,两个转基因株系的酶活性较对照分别提高1.33倍和1.13倍,P_n分别较对照下降17.26%和10.35%;千粒重和籽粒产量较对照均显著下降。与对照周麦23相比,转基因株系10T(9)-225-4利用强光和同化CO_2能力下降,光合效率下降;旗叶气孔张开率和气孔导度均显著下降;苹果酸含量降低了5.6%,丙酮酸含量则提高了17.1%;外施苹果酸可恢复其光合速率。以上研究结果表明,玉米C_4型NADP-ME基因的导入降低了小麦的光合特性,苹果酸含量降低引起的气孔导度下降可能是导致转基因小麦光合效能降低的原因。

To explore the physiological characteristics of the transgenic wheat expressing maize C4-type NADP-ME, we introduced NADP-ME into the C3 crop wheat by using particle bombardment transformation. Two transgenic wheat lines（10T（9）-1-1, 10T（9）-225-4） and parental control（Zhoumai 23） were used to study molecular characteristics and photosynthesis property, to reveal the mechanism. The results showed that the NADP-ME sequence was integrated into wheat genome, and the transcription and translation were exactly same as expect. The enzyme activity of NADP-ME in flag leaf in transgenic plants were increased significantly than untransformed plants, for instance it was increased 1.33 and 1.13 times on the 7th day after flowering. Net photosynthetic rate（Pn） of flag leaf in transgenic plants obviously decreased when compared to the untransformed plants. On the 7th day after anthesis, Pn of transgenic wheat decreased by 17.26% and 10.35%. The yield and 1000-grain weight were decreased than the control. Utilization efficiency on strong light utilizing and ability of CO2 assimilation in transgenic line 10T（9）-225-4 were significantly declined, photosynthesis rate was also decreased. Stomatal opening rate and stomatal conductance were significant decrease, malic acid content of transgenic wheat reducing 5.6% while pyruvate level is raised by 17.1%, and Pn of transgenic wheat can be restored by feeding with exogenous malate. Those results indicated that the transgenic wheat expressing maize NADP-ME gene showed lower photosynthetic characteristics than the control, the reason was maybe the decrease of stomatal aperture caused by decline of malic acid content.