Overexpression of thylakoidal ascorbate peroxidase shows enhanced resistance to chilling stress in tomato

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• 作者：Ming Duan ; Hai-Long Feng ; Li-Yan Wang ; Dong Li ; Qing-Wei Meng ; ^{qwmeng@sdau.edu.cn}
• 关键词：ABA ; abscisic acid ; APX ; ascorbate peroxidase ; AsA ; ascorbate ; DAB ; diaminobenzidin ; DHA ; dehydroascorbate ; Fv/Fm ; the maximal photochemical efficiency of PSII ; GFP ; green fluorescence protein ; GSH ; reduced glutathione ; GSSG ; oxidized glutathione ; MDA ; ma
• 刊名：Journal of Plant Physiology
• 出版年：2012
• 期刊代码：10_01761617
• 类别：abs
• 出版时间：15 June, 2012
• 卷：169
• 期：9
• 页码：867-877
• 文件大小：1456 K

摘要

Photosynthesis provides a strong reducing power and a high risk for generation of reactive oxygen species (ROS) particularly under chilling stress. Ascorbate peroxidases (APXs) reduce H₂O₂ to water and play an important role in the antioxidant system of plants. Though thylakoid ascorbate peroxidase (tAPX) has been thought to be key regulator of intracellular levels of H₂O₂, its physiological significance in the response to chilling stress is still under discussion. To study the contribution of tAPX to the ROS scavenging, a tomato thylakoidal ascorbate peroxidase gene (LetAPX) was isolated and transgenic tomatoes were obtained. The LetAPX-GFP fusion protein was targeted to chloroplast in Arabidopsis mesophyll protoplast. RNA blotting analysis revealed that the LetAPX transcript expression was up-regulated by chilling, high light, exogenous salicylic acid (SA) and methyl viologen (MV). Over expression of LetAPX in tomatoes conferred tolerance to chilling stress by maintaining higher reduced glutathione (GSH) content, chlorophyll and APX activities compared with wild type (WT) plants. Furthermore, transgenic plants showed lower levels of hydrogen peroxide (H₂O₂) and ion leakage, lower malendialdehyde (MDA) content, higher net photosynthetic rate (Pn) and higher maximal photochemical efficiency of PSII (Fv/Fm). The oxidizable P700 decreased more obviously in WT than that in transgenic plants under chilling stress in low irradiance. The results suggested that over expression of tAPX played a key role both in alleviating photo inhibition of PSI and PSII and enhancing their tolerance to chilling stress.