Manganese-based nanozyme enabled efficient mitigation of Huanglongbing-induced oxidative damage in Citrus†

Abstract

Huanglongbing (HLB) is a severe disease in Citrus caused by the infection of Candidatus Liberibacter asiaticus (CLas), which has brought about substantial economic losses in the global Citrus industry. Recently, HLB has been recognized as a plant immune-mediated disease resulting from the CLas-colonization stimulated immune responses and the accumulation of excessive reactive oxygen species (ROS) in Citrus tissues. Here, we report a manganese oxide nanozyme (MONPs) based strategy to scavenge and regulate the ROS metabolism in HLB infected Citrus, thereby protecting leaf tissues against oxidative stress. Transmission electron microscopy (TEM) imaging revealed that MONPs enable efficient delivery into the intercellular space by spraying dispersion. ROS detection indicated the direct ROS scavenging ability of MONPs with high efficiency in HLB-Citrus with about 60% of ROS decreasing. Enzyme activation and gene expression analysis exhibited that the MONP treatment could regulate the ROS metabolism gene in Citrus to alleviate oxidative stress. Current research demonstrated that the HLB-Citrus sprayed with MONPs showed a noticeable protective effect within 22 days to alleviate the blotchy mottle symptoms. Furthermore, various physiological indexes such as MDA, starch, total soluble sugar, carotenoid and chlorophyll in HLB-Citrus leaves exhibited significant improvement post-MONP treatment. This MONP-based approach provides a promising alternative strategy to modulate and mitigate oxidative stress in HLB-Citrus, thereby serving the Citrus industry.