Wang Liyan, Meng Xia, Yang Dongyue, Ma Nana, Wang Guodong, Meng Qingwei
College of Life Science, Dezhou University, Dezhou, 253023, Shandong, People's Republic of China.
Plant Cell Rep. 2014 Sep;33(9):1441-51. doi: 10.1007/s00299-014-1627-2. Epub 2014 May 16.
The overexpression of tomato GDP- l -galactose phosphorylase gene enhanced tolerance to chilling stress and reduced photoinhibition of photosystems I and II in transgenic tobacco. Chilling stress is a crucial factor that limits the geographical distribution and yield of chilling-sensitive plants. Ascorbate (AsA) protects plants by scavenging reactive oxygen species and reduces photoinhibition by promoting the conversion of violaxanthin to zeaxanthin in the xanthophyll cycle to dissipate excess excitation energy. Possible mechanisms of AsA for plant photoprotection under chilling stress were investigated by isolating the tomato GDP-L-galactose phosphorylase gene (SlGGP) and producing transgenic tobacco plants with overexpression of SlGGP. The transgenic plants subjected to chilling stress accumulated less H(2)O(2), demonstrated lower levels of ion leakage and malondialdehyde, and acquired higher net photosynthetic rate, higher maximum photochemical efficiency of PSII, and higher D1 protein content compared with the wild-type (WT) plants. The transgenic plants subjected to chilling stress also showed higher GDP-L-galactose phosphorylase activity, increased AsA content as well as ascorbate peroxidase and oxidizable P700 activities than WT plants. Thus, SlGGP overexpression is crucial in promoting AsA synthesis and alleviating photoinhibition of two photosystems.
番茄GDP-L-半乳糖磷酸化酶基因的过表达增强了转基因烟草对低温胁迫的耐受性，并减轻了光系统I和II的光抑制。低温胁迫是限制冷敏感植物地理分布和产量的关键因素。抗坏血酸（AsA）通过清除活性氧来保护植物，并通过促进叶黄素循环中紫黄质向玉米黄质的转化来减少光抑制，从而消散多余的激发能。通过分离番茄GDP-L-半乳糖磷酸化酶基因（SlGGP）并培育SlGGP过表达的转基因烟草植株，研究了AsA在低温胁迫下对植物光保护的可能机制。与野生型（WT）植株相比，遭受低温胁迫的转基因植株积累的H₂O₂更少，离子渗漏和丙二醛水平更低，净光合速率更高，PSII的最大光化学效率更高，D1蛋白含量更高。遭受低温胁迫的转基因植株还表现出比WT植株更高的GDP-L-半乳糖磷酸化酶活性、增加的AsA含量以及抗坏血酸过氧化物酶和可氧化P700活性。因此，SlGGP的过表达对于促进AsA合成和减轻两个光系统的光抑制至关重要。
