Manganese (Mn) is an essential element for plant growth but it becomes phytotoxic at higher concentrations. The effect of Mn-excess in hydroponics medium was examined on growth, oxidative stress, and ultrastructural changes in chloroplasts and mitochondria as well proteomic alterations in rice (Oryza sativa L.) seedlings. Seedlings grown with 1 mM and 2 mM Mn in nutrient medium for 8 days showed decline in length and fresh biomass, and decline in net photosynthetic rate, transpiration rate, and stomatal conductance. Shoots of the seedlings had higher Mn content than roots. Mn-treated seedlings showed increased production of O2·-, H2O2, and .OH, increased lipid peroxidation, increased carbonylation of proteins, and increased proteolytic activity compared to untreated seedlings. Mn-treated seedlings showed disorganization and swelling of chloroplasts with appearance of plastoglobuli in TEM images and deformity in shape of mitochondria. Using confocal microscopy depolarization of mitochondrial membrane was observed marked by green fluorescence of JC-1 dye monomers in Mn-treated roots. Proteomics studies from leaves of Mn-treated seedlings involving 2DE and PDQuest analysis showed differential expression of 23 proteins, among which MALDI-TOF/TOF mass spectrometry analysis revealed Mn-led downregulation of photosynthesis-related proteins, namely oxygen-evolving complex protein associated with PSII, PAP-3, enzyme involved in protein folding peptidyl-prolyl cis-trans isomerase (PPIase) and carbohydrate metabolizing enzymes hydrolase, fructose-bisphosphate aldolase, transketolase, and isocitrate dehydrogenase, whereas ATP-dependent Clp protease, peroxidase, and nucleic acid-binding proteins were downregulated due to Mn treatment. Results indicate that Mn-excess inhibits growth of rice plants with induction of oxidative stress, causing structural alterations in chloroplasts, mitochondria, inhibiting photosynthesis, and downregulating many photosynthesis and carbohydrate metabolism-related proteins.

中文翻译：

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锰诱导的水稻氧化应激、超微结构变化和蛋白质组学研究

锰 (Mn) 是植物生长的必需元素，但在较高浓度时会产生植物毒性。检查了水培培养基中锰过量对叶绿体和线粒体的生长、氧化应激和超微结构变化以及水稻 (Oryza sativa L.) 幼苗的蛋白质组学改变的影响。在营养培养基中用 1 mM 和 2 mM Mn 生长 8 天的幼苗显示长度和新鲜生物量下降，净光合速率、蒸腾速率和气孔导度下降。幼苗芽的锰含量高于根。与未处理的幼苗相比，Mn 处理的幼苗表现出增加的 O2·-、H2O2 和 .OH 的产生，增加脂质过氧化，增加蛋白质的羰基化，并增加蛋白水解活性。Mn 处理的幼苗显示叶绿体解体和肿胀，TEM 图像中出现质体球，线粒体形状畸形。使用共聚焦显微镜观察到线粒体膜的去极化由 Mn 处理的根中 JC-1 染料单体的绿色荧光标记。Mn 处理幼苗叶片的蛋白质组学研究涉及 2DE 和 PDQuest 分析显示 23 种蛋白质的差异表达，其中 MALDI-TOF/TOF 质谱分析显示 Mn 导致光合作用相关蛋白质的下调，即与PSII、PAP-3、参与蛋白质折叠肽基-脯氨酰顺反异构酶（PPIase）和碳水化合物代谢酶水解酶、果糖-二磷酸醛缩酶、转酮醇酶和异柠檬酸脱氢酶的酶，而 ATP 依赖性 Clp 蛋白酶、过氧化物酶和核酸结合蛋白由于锰处理而下调。结果表明，锰过量通过诱导氧化应激抑制水稻植株的生长，引起叶绿体、线粒体的结构改变，抑制光合作用，并下调许多光合作用和碳水化合物代谢相关蛋白。