Hydroxyl radical scavenging by cerium oxide nanoparticles improves Arabidopsis salinity tolerance by enhancing leaf mesophyll potassium retention
Hydroxyl radical scavenging by cerium oxide nanoparticles improves Arabidopsis salinity tolerance by enhancing leaf mesophyll potassium retention
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DOI：
10.1039/c8en00323h
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发表时间：
2018-07
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通讯作者：
Honghong Wu;L. Shabala;S. Shabala;J. P. Giraldo
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作者：
Honghong Wu;L. Shabala;S. Shabala;J. P. Giraldo
盐度是一种广泛存在的环境压力，严重限制了世界范围内的作物产量。氧化铈纳米颗粒（nanoceria）具有独特的催化能力，可以降低缺乏酶清除途径的应激诱导的活性氧（ROS）水平，包括羟基自由基（OH）。纳米粒活性氧清除如何增强植物对环境胁迫的耐受性的潜在机制尚不清楚。本研究表明，拟南芥叶片中纳米粒的催化˙OH清除作用显著提高了叶肉K+潴留，这是与盐胁迫耐受性相关的一个关键性状。经100 mM NaCl处理3天后，叶肉细胞与50 mg L−1聚丙烯酸包被纳米膜（PNC）界面的叶片的碳同化率（85%）、光系统II量子效率（9%）和叶绿素含量（14%）显著高于对照（P < 0.05）。盐度胁迫下的PNC浸渍叶片（PNC-叶片）表现出较低的ROS水平（包括羟基自由基（41%）及其前体过氧化氢（44%）），叶肉细胞胞质K+染料强度比对照高1倍（P < 0.05）。非侵入性微电极离子通量电生理（MIFE）测量表明，在暴露于盐度胁迫下，pnc叶片叶肉细胞中nacl诱导的K+外排比对照组低约3倍。结果表明，叶肉细胞质膜上活性氧激活的非选择性阳离子通道（ROS-NSCC）是主要的˙oh诱导的K+外排通道。PNC长期催化清除叶片中的˙OH，通过使质膜通道/转运体协调地在叶肉细胞细胞质中保留更高水平的K+，提高了植物在盐度胁迫下的光合性能。PNC增强植物活性氧清除能力为理解和提高植物对非生物胁迫（如盐度）的耐受性提供了关键工具。
Salinity is a widespread environmental stress that severely limits crop yield worldwide. Cerium oxide nanoparticles (nanoceria) have the unique capability of catalytically reducing levels of stress-induced reactive oxygen species (ROS) including hydroxyl radicals (˙OH) that lack enzymatic scavenging pathways. The underlying mechanisms of how nanoceria ROS scavenging augments plant tolerance to environmental stress are not well understood. Herein, we demonstrate that catalytic ˙OH scavenging by nanoceria in Arabidopsis thaliana leaves significantly improves mesophyll K+ retention, a key trait associated with salinity stress tolerance. Leaves with mesophyll cells interfaced with 50 mg L−1 poly(acrylic acid) coated nanoceria (PNC) have significantly higher (P < 0.05) carbon assimilation rates (85%), quantum efficiency of photosystem II (9%), and chlorophyll content (14%) compared to controls after being exposed to 100 mM NaCl for 3 days. PNC infiltrated leaves (PNC-leaves) under salinity stress exhibit lower ROS levels – including hydroxyl radical (41%) and its precursor hydrogen peroxide (44%) – and one fold higher (P < 0.05) cytosolic K+ dye intensity in leaf mesophyll cells relative to controls. Non-invasive microelectrode ion flux electrophysiological (MIFE) measurements indicated that PNC-leaves have about three-fold lower NaCl-induced K+ efflux from leaf mesophyll cells compared to controls upon exposure to salinity stress. The ROS-activated nonselective cation channels (ROS-NSCC) in the plasma membrane of leaf mesophyll cells were identified as the main ˙OH-inducible K+ efflux channels. Long term catalytic scavenging of ˙OH in leaves by PNC enhances plant photosynthetic performance under salinity stress by enabling plasma membrane channels/transporters to coordinately retain higher levels of K+ in the leaf mesophyll cell cytosol. PNC augmented plant ROS scavenging provides a key tool for understanding and improving plant tolerance against abiotic stresses such as salinity.