近日，华中农业大学农业微生物资源发掘与利用全国重点实验室、纳米化学生物学团队韩鹤友教授课题组在Environment Science nano上发表题为“Manganese-based nanozyme enabled efficient mitigation of Huanglongbing-induced oxidative damage inCitrus”的研究论文。本研究通过构建一种锰氧化物纳米酶（MONPs），实现对黄龙病感染柑橘组织氧代谢的清除和调节，从而保护叶组织对抗氧化胁迫的损伤 （图1）。
图1. MONPs对黄龙病柑橘的保护作用示意图
论文研究了生理环境下MONPs是否具有清除活性氧的能力，在体外模拟了多种活性氧环境用于评估MONPs的抗氧化活性。结果表明MONPs具有多种类酶活性，具有广谱的活性氧直接清除功能。图2解析了MONPs在柑橘叶组织中的内化和分布情况：通过透射电子显微镜对喷洒和渗透MONPs的柑橘叶片进行精细扫描，可观察到大量的MONPs特征性纳米花结构定位于细胞壁周围的细胞外间隙，表明MONPs能够被柑橘叶有效吸收。这种基于MONPs的递送系统有望为解决柑橘和其他植物的递送问题提供一种更有效且环保的替代方法。
图2. 柑橘叶组织中MONPs内化的电镜图像
通过研究MONPs在柑橘体内的抗氧化机制，结果表明，MONPs处理展现出对患病柑橘中氧化防御相关基因表达和酶活性等显著的正调控，从而通过间接的抗氧化途径减轻CLas侵染所引起的胁迫。图3展现了MONP处理是否能够预防和保护柑橘免受黄龙病感染，通过对黄龙病感染初期的柑橘进行MONPs对长期处理，表明MONPs可通过抗氧化作用有效缓解黄龙病的相关症状。图4结果显示，MONPs处理后大幅改善了患病柑橘中相关生理指标，相关基因表达和酶活性，展现了对患病柑橘生长的有效保护。
图3.MONPs处理后黄龙病柑橘的表型进展
图4.MONP处理的黄龙病柑橘和健康柑橘的生理指标
综上，这种基于锰基纳米酶（MONPs）的防治策略，多功能、高稳定性和易于批量制备，可通过叶片喷雾和注射等施用方式有效地内化进患病柑橘内部，减轻氧化损伤，保护植物组织并缓解黄龙病症状。有潜力拓展纳米材料在柑橘黄龙病防治中的应用，服务于柑橘产业的发展。
本文的第一作者为华中农业大学生命科学技术学院博士研究生李烁钧（现中国科学院分子细胞卓越创新中心博士后）与化学学院硕士研究生龙玉滢，通讯作者为我校韩鹤友教授。该研究得到国家重点研发计划项目（2021YFD1400803）的资助。
【英文摘要】
Huanglongbing (HLB) is a severe disease in Citrus caused by the infection ofCandidatusLiberibacter 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 theCLas-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.
论文链接：
https://doi.org/10.1039/D4EN00519H
