Engineered nanomaterials interfaced with plant seeds can improve stress tolerance during the vulnerable seedling stage. Herein, we investigated how priming seeds with antioxidant poly(acrylic acid)-coated cerium oxide nanoparticles (PNC) impacts cotton ( Gossypium hirsutum L.) seedling morphological, physiological, biochemical, and transcriptomic traits under salinity stress. Seeds primed with 500 mg L −1 PNC in water (24 h) and germinated under salinity stress (200 mM NaCl) retained nanoparticles in the seed coat inner tegmen, cotyledon, and root apical meristem. Seed priming with PNC significantly ( P < 0.05) increased seedling root length (56%), fresh weight (41%), and dry weight (38%), modified root anatomical structure, and increased root vitality (114%) under salt stress compared with controls (water). PNC seed priming led to a decrease in reactive oxygen species (ROS) accumulation in seedling roots (46%) and alleviated root morphological and physiological changes induced by salinity stress. Roots from exposed seeds exhibited similar Na content, significantly decreased K (6%), greater Ca (22%) and Mg content (60%) compared to controls. A total of 4779 root transcripts were differentially expressed by PNC seed priming alone relative to controls with no nanoparticles under non-saline conditions. Under salinity stress, differentially expressed genes (DEGs) in PNC seed priming treatments relative to non-nanoparticle controls were associated with ROS pathways (13) and ion homeostasis (10), indicating that ROS and conserved Ca 2+ plant signaling pathways likely play pivotal roles in PNC-induced improvement of salinity tolerance. These results provide potential unifying molecular mechanisms of nanoparticle-seed priming enhancement of plant salinity tolerance.
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Hydroxyl radical scavenging by cerium oxide nanoparticles improves Arabidopsis salinity tolerance by enhancing leaf mesophyll potassium retention
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.
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- Award ID(s):
- 1817363
- NSF-PAR ID:
- 10274633
- Date Published:
- Journal Name:
- Environmental Science: Nano
- Volume:
- 5
- Issue:
- 7
- ISSN:
- 2051-8153
- Page Range / eLocation ID:
- 1567 to 1583
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/C8EN00323H
