Department of Biochemistry, Institute of Science, Banaras Hindu University, Varanasi, 221005, India.
Protoplasma. 2021 Mar;258(2):319-335. doi: 10.1007/s00709-020-01575-0. Epub 2020 Oct 18.
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 O, HO, 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.
锰（Mn）是植物生长所必需的元素，但在较高浓度下会产生植物毒性。本研究在水培介质中研究了过量的锰对水稻（Oryza sativa L.）幼苗生长、氧化应激、叶绿体和线粒体超微结构变化以及蛋白质组学改变的影响。在营养培养基中用 1mM 和 2mM Mn 处理 8 天的幼苗表现出长度和鲜重减少，净光合速率、蒸腾速率和气孔导度降低。与根相比，幼苗的地上部分 Mn 含量更高。与未处理的幼苗相比，Mn 处理的幼苗表现出 O、HO 和 OH 生成增加，脂质过氧化增加，蛋白质羰基化增加，蛋白水解活性增加。透射电镜图像显示 Mn 处理的幼苗叶绿体排列紊乱肿胀，出现质体小球，线粒体形状畸形。使用共聚焦显微镜观察到 Mn 处理的根中 JC-1 染料单体的绿色荧光标记线粒体膜去极化。对 Mn 处理的幼苗叶片进行蛋白质组学研究，包括 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 下调与光合作用相关的蛋白质，即与 PSII 相关的放氧复合体蛋白、PAP-3、参与蛋白质折叠的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-1,6-二磷酸醛缩酶、转酮醇酶和异柠檬酸脱氢酶，而由于 Mn 处理，ATP 依赖性 Clp 蛋白酶、过氧化物酶和核酸结合蛋白下调。结果表明，过量的 Mn 抑制水稻植株的生长，诱导氧化应激，导致叶绿体、线粒体结构改变，抑制光合作用，并下调许多与光合作用和碳水化合物代谢相关的蛋白质。
