Hydroxyl radical scavenging by cerium oxide nanoparticles improves Arabidopsis salinity tolerance by enhancing leaf mesophyll potassium retention

• Published in: Environmental science. Nano Vol. 5; no. 7; pp. 1567 - 1583
• Main Authors: Wu, Honghong, Shabala, Lana, Shabala, Sergey, Giraldo, Juan Pablo
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 2018
• Subjects: Acrylic acid; Arabidopsis thaliana; carbon dioxide fixation; Carbon fixation; Catalysis; Cations; Cells; Cerium; Cerium oxides; Channels; Chlorophyll; Chlorophylls; Crop yield; Cytosol; Dyes; Efflux; Electrophysiology; environmental science; Environmental stress; Free radicals; Hydrogen peroxide; Hydroxyl radicals; Ion channels; Ion flux; Leaves; Membrane channels; Mesophyll; Microelectrodes; nanoceria; Nanoparticles; Photosynthesis; Photosystem II; Plants; plasma membrane; Potassium; Quantum efficiency; Retention; Salinity; Salinity effects; Salinity tolerance; salt stress; salt tolerance; Scavenging; Sodium chloride; stress tolerance; Stresses
• ISSN: 2051-8153; 2051-8161
• DOI: 10.1039/C8EN00323H

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.