Rapid Inactivation of Chloroplastic Ascorbate Peroxidase is Responsible for Oxidative Modification to Rubisco in Tomato (Lycopersicon esculentum) under Cadmium Stress

文献类型： 外文期刊

第一作者： Liu, Kai-Lang

作者： Liu, Kai-Lang;Shen, Lin;Sheng, Ji-Ping;Liu, Kai-Lang;Wang, Jia-Qi

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期刊名称：JOURNAL OF INTEGRATIVE PLANT BIOLOGY （ 影响因子：7.061； 五年影响因子：6.002 ）

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收录情况： SCI

摘要： To investigate the sensitive site of antioxidant systems in chloroplast under cadmium stress and its consequence on reactive oxygen species production and action, the sub-organellar localization of chloroplast superoxide dismutases (SOD, EC 1.15.1.1) and ascorbic peroxidase (APX, EC 1.11.1.11) isoenzymes and changes of enzymes activities under cadmium stress were investigated in tomato seedlings. Two APX isoforms, one thylakoid-bound and one stromal, were detected. Cd at 50 oM induced a moderate increase of SOD activities but a rapid inactivation of both APX isoenzymes. APX inactivation was mainly related to the decrease of ascorbate concentration, as supported by in vitro treatment of exogenous ascorbate and APX kinetic properties under Cd stress. HO accumulation in chloroplast, as a consequence of APX inactivation, was associated with a 60% loss of Rubisco (EC 4.1.1.39) activity, which could be partially accounted for by a 10% loss of Rubisco content. Protein oxidation assay found that the Rubisco large subunit was the most prominent carbonylated protein; the level of carbonylated Rubisco large subunit increased fivefold after Cd exposure. Thiol groups in the Rubisco large subunit were oxidized, as indicated by non-reducing electrophoresis. Treating crude extract with HO resulted in a similar pattern of protein oxidation and thiols oxidation with that observed in Cd-treated plants. Our study indicates that APXs in the chloroplast is a highly sensitive site of antioxidant systems under Cd stress, and the inactivation of APX could be mainly responsible for oxidative modification to Rubisco and subsequent decrease in its activity.

分类号： Q94

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