Quaternary Ammonium Salts of Iminofullerenes Promote Root Growth and Osmotic-stress Tolerance of Maize via Scavenging ROS and Enhancing Energy Production

Abstract In the present study, the positive roles of cationic quaternary ammonium salts of iminofullerenes (IFQA) on the root growth of plant seedlings and response to osmotic stress were investigated. The root elongation of Arabidopsis and maize exposed to 20 and 50 mg/L of IFQA under polyethylene glycol (PEG) stress were obviously promoted, respectively. Under PEG stress, the activities of superoxide dismutase, catalase, the accumulation of proline, and chlorophyll were significantly improved in leaves of maize when exposed to 50 mg/L IFQA; the contents of hydrogen peroxide (H2O2) and malondialdehyde (MDA) were downregulated. IFQA application improved the activities of glutathione transferase, glutathione reductase, the ratios of glutathione/oxidized glutathione, ascorbic acid/dehydroascorbic acid, and restored the inhibition of root elongation caused by the exceeded accumulation of H2O2 under PEG stress. Meanwhile, the root active absorption area and ATP content of roots were also enhanced by IFQA. Furthermore, the expressions of fourteen proteins involved in cell growth, energy metabolism, and stress response were upregulated in maize roots evaluated by two-dimensional electrophoresis combination with mass spectrometry. It revealed that IFQA stimulated the redox pathway to maintain the low levels of reactive oxygen species to ensure cell normal metabolism, promoted energy production for root growths, and enhanced osmotic-stress tolerance. This study provides important information to understand the mechanism of root growths of crop seedlings enhanced by water-soluble fullerene-based nanomaterials.