转ppc基因水稻苗期抗旱特性研究

通过C₄转基因技术改善C₃作物光合作用, 以期提高作物产量是国内外研究的热点之一。然而, 目前关于转磷酸烯醇式丙酮酸羧化酶(PEPC)基因对水稻的光合作用、产量和抗旱性的影响及其调节机理仍不很清楚。本研究以T₄代转ppc基因水稻为材料, 进行产量和苗期抗旱性研究。结果表明, 在旱作栽培条件下, 两个转ppc基因株系(T1, T2)单株产量分别比未转基因的对照(WT)增产28%和42%, 分蘖增加27%和40%; T1和T2可维持较高的光合速率、气孔导度和水分利用效率; 干旱胁迫使超氧化物歧化酶(SOD)活性和丙二醛(MDA)含量增加, T1和T2 SOD活性增幅(+25%)都显著高于WT(+9%), 而MDA含量增幅显著低于WT, 表明转ppc基因水稻具有较强的抗氧化能力; T1和T2比WT具有较高的脯氨酸含量和渗透势下降幅度, 说明转PEPC基因水稻的渗透调节能力高于对照。PEG-6000处理下, 得到的结果相似。

Characteristics of Drought Tolerance in ppc Overexpressed Rice Seedlings

Introducing enzymes involved in C₄ photosynthesis into C₃ crops is supposed to enhance the photosynthesis and crop productivity. Several attempts have been made to transfer phosphoenolpyruvate carboxylase (PEPC) gene from maize into rice, however, the relation of photosynthetic capacity, productivity and stress tolerance in transgenic rice was not analyzed. In the present research, the productivity and photosynthesis in T₄ offspring of ppc gene overexpressed rice were investigated under drought stress. The results indicated that the yield increased by 28% and 42%, and the number of tillers increased by 27% and 40%, respectively, in two transgenic lines T1 and T2 compared with those of the wild type under upland cultivation. Under drought stress, the transgenic rice seedlings maintained higher photosynthesis (A), stomatal conductance (G_s) and water use efficiency (WUE), as well as higher superoxide dismutase (SOD) activity and lower malondialdehyde (MDA) content than the wild type. It is suggested that the overexpression of ppc gene in rice makes higher antioxidation ability under drought stress. In addition, the transgenic lines T1 and T2 exhibited higher proline content and lower increase of osmotic potential under drought stress, suggesting that the ppc gene transgenic rice has the higher osmoregulation ability than the wild type. The similar results were also found in the ex-periments treated by PEG-6000. Therefore, the present results suggested that, the ppc gene overexpressed rice confers higher photosynthesis and drought tolerance under drought stress, which is helpful to increase the number of tillers, then contribute to enhance the rice yield.