Data_Sheet_2_Arabidopsis Iron Superoxide Dismutase FSD1 Protects Against Methyl Viologen-Induced Oxidative Stress in a Copper-Dependent Manner.XLSX

Iron superoxide dismutase 1 (FSD1) was recently characterized as a plastidial, cytoplasmic, and nuclear enzyme with osmoprotective and antioxidant functions. However, the current knowledge on its role in oxidative stress tolerance is ambiguous. Here, we characterized the role of FSD1 in response to methyl viologen (MV)-induced oxidative stress in Arabidopsis thaliana. In accordance with the known regulation of FSD1 expression, abundance, and activity, the findings demonstrated that the antioxidant function of FSD1 depends on the availability of Cu2+ in growth media. Arabidopsis fsd1 mutants showed lower capacity to decompose superoxide at low Cu2+ concentrations in the medium. Prolonged exposure to MV led to reduced ascorbate levels and higher protein carbonylation in fsd1 mutants and transgenic plants lacking a plastid FSD1 pool as compared to the wild type. MV induced a rapid increase in FSD1 activity, followed by a decrease after 4 h long exposure. Genetic disruption of FSD1 negatively affected the hydrogen peroxide-decomposing ascorbate peroxidase in fsd1 mutants. Chloroplastic localization of FSD1 is crucial to maintain redox homeostasis. Proteomic analysis showed that the sensitivity of fsd1 mutants to MV coincided with decreased abundances of ferredoxin and photosystem II light-harvesting complex proteins. These mutants have higher levels of chloroplastic proteases indicating an altered protein turnover in chloroplasts. Moreover, FSD1 disruption affects the abundance of proteins involved in the defense response. Collectively, the study provides evidence for the conditional antioxidative function of FSD1 and its possible role in signaling.

铁超氧化物歧化酶1（Iron superoxide dismutase 1, FSD1）近日被鉴定为一种同时定位于质体、细胞质与细胞核的酶，兼具渗透保护与抗氧化功能。然而，目前学界对其在氧化应激耐受中发挥的作用尚存在歧义。本研究以拟南芥（Arabidopsis thaliana）为材料，解析了FSD1在响应甲基紫精（methyl viologen, MV）诱导的氧化应激中的功能。结合已知的FSD1表达、丰度及活性调控规律，本研究结果表明，FSD1的抗氧化功能依赖于培养基中Cu²+的可获得性。当培养基中Cu²+浓度较低时，fsd1突变体清除超氧化物的能力显著降低。与野生型相比，长期暴露于MV的fsd1突变体以及缺失质体FSD1库的转基因植株，其抗坏血酸水平下降，蛋白质羰基化程度升高。MV可快速诱导FSD1活性上升，在暴露4小时后活性则出现下降。FSD1的遗传破坏会负向影响fsd1突变体中分解过氧化氢的抗坏血酸过氧化物酶的功能。FSD1的叶绿体定位对维持细胞氧化还原稳态至关重要。蛋白质组学分析显示，fsd1突变体对MV的敏感性与铁氧还蛋白及光系统II捕光复合物蛋白的丰度降低相吻合。这类突变体的叶绿体蛋白酶水平更高，表明叶绿体中的蛋白质周转发生了改变。此外，FSD1功能缺失会影响参与防御响应的蛋白质的丰度。综上，本研究为FSD1的条件性抗氧化功能及其在信号传导中的潜在作用提供了实验证据。