Manganese-Enhanced Nanopesticides Augment Plant Resistance against Viral Infection via an Untapped Macroautophagy Pathway

Manganese is vital for plant growth and disease resistance but remains underutilized as a bioactive agent due to its toxicity at high concentrations. Here, an effective antiviral nanopesticide system utilizing Mn ions (Mn 2+ ) within safe limits is described. Briefly, cellulose nanocrystals (CNCs) are employed as bio-sourced carrier surfaces and polydopamine (PDA) as a stabilizing and chelating agent for Mn 2+ . By impregnating Mn 2+ onto PDA-coated CNCs, the stable CNC@PDA@Mn 2+ (CPM) composite is fabricated. The CPM composite exhibits a substantially strengthened inhibitory effect on virus infectivity and curtails virus accumulation in Nicotiana benthamiana . The synergistic effects of CPM stem from its ability to directly disrupt viral particles and activate the plant-immunity-related antioxidant systems. Additionally, H 2 O 2 generated by the CPM-activated superoxide dismutase potentially serves as a molecular signal to overexpress the disease-resistance gene harpin-induced 1 ( NbHin1 ) by sulfinylating CCA1 Hiking Expedition and enhance its binding to NbHin1 promoter. Subsequently, this upregulation coordinates the activation of NbHin1 -dependent macroautophagy, triggering multiple antiviral defense mechanisms. Thus, this design achieves highly potent broad-spectrum antiviral activity at low concentrations of manganese (16 µg mL −1 ). Notably, this work pioneers the use of Mn 2+ in triggering plant antiviral defense, offering a solid foundation for designing novel antiviral agents.