State Key Laboratory of Crop Biology, College of Life Science, Shandong Agricultural University, Tai'an, Shandong 271018, P.R. China.
Physiol Plant. 2010 Aug 1;139(4):421-34. doi: 10.1111/j.1399-3054.2010.01369.x. Epub 2010 Mar 8.
A tomato (Lycopersicon esculentum Mill.) monodehydroascorbate reductase gene (LeMDAR) was isolated. The LeMDAR-green fluorescence protein (GFP) fusion protein was targeted to chloroplast in Arabidopsis mesophyll protoplast. RNA and protein gel blot analyses confirmed that the sense- and antisense- LeMDAR were integrated into the tomato genome. The MDAR activities and the levels of reduced ascorbate (AsA) were markedly increased in sense transgenic lines and decreased in antisense transgenic lines compared with wild-type (WT) plants. Under low and high temperature stresses, the sense transgenic plants showed lower level of hydrogen peroxide (H(2)O(2)), lower thiobarbituric acid reactive substance (TBARS) content, higher net photosynthetic rate (P(n)), higher maximal photochemical efficiency of PSII (F(v)/F(m)) and fresh weight compared with WT plants. The oxidizable P700 decreased more obviously in WT and antisense plants than that in sense plants at chilling temperature under low irradiance. Furthermore, the sense transgenic plants exhibited significantly lower H(2)O(2) level, higher ascorbate peroxidase (APX) activity, greater P(n) and F(v)/F(m) under methyl viologen (MV)-mediated oxidative stresses. These results indicated that overexpression of chloroplastic MDAR played an important role in alleviating photoinhibition of PSI and PSII and enhancing the tolerance to various abiotic stresses by elevating AsA level.
从番茄中克隆到单脱氢抗坏血酸还原酶基因（LeMDAR）。构建 LeMDAR-绿色荧光蛋白（GFP）融合蛋白表达载体，转化拟南芥原生质体，激光共聚焦显微镜观察结果表明该融合蛋白定位于叶绿体。通过 RNA 和蛋白凝胶电泳分析证明，正义和反义 LeMDAR 基因已整合到番茄基因组中。与野生型（WT）植株相比，过表达植株的 MDAR 活性和还原型抗坏血酸（AsA）含量明显升高，反义植株的 MDAR 活性和 AsA 含量则明显降低。在低温和高温胁迫下，过表达植株的过氧化氢（H2O2）含量、丙二醛（TBARS）含量比 WT 植株低，净光合速率（Pn）、最大光化学效率（Fv/Fm）和鲜重比 WT 植株高。在弱光低温下，WT 和反义植株的可氧化型 P700 比过表达植株降低更明显。过表达植株在 MV 介导的氧化胁迫下，H2O2 含量更低，抗坏血酸过氧化物酶（APX）活性更高，净光合速率（Pn）和最大光化学效率（Fv/Fm）更高。这些结果表明，过表达叶绿体 MDAR 通过提高 AsA 含量，缓解 PSI 和 PSII 的光抑制，增强植株对各种非生物胁迫的耐受性。
