近日，华中农业大学生命科学技术学院、农业微生物学国家重点实验室王革娇教授课题组即环境微生物课题组在国际学术期刊Molecular Plant-Microbe Interactions上发表了关于微生物与水稻互作降低稻米镉含量的最新研究成果。论文以“A coculture of Enterobacter and Comamonas reduces Cd accumulation in rice”为题，阐明了微生物菌剂通过代谢产物促进水稻镉转运及结合蛋白活性的分子机制。
镉是引起粮食减产的主要金属之一，其具有高溶解性及高迁移性，易被植物吸收和积累。近年来农田土壤镉污染修复成为国内外学者研究的热点，微生物参与了水稻对土壤中镉的吸收，然而微生物如何影响水稻对土壤镉吸收及解毒的分子机制并不清楚。
课题组发现了当肠杆菌和丛毛单胞菌共同培养时，可以将溶液中的镉离子沉淀并完全去除。将这种混合菌剂应用于镉污染水稻盆栽实验中，该混合菌剂可以有效钝化土壤中的镉，减少水稻对镉离子的吸收，使稻米中镉含量显著下降。采用原位杂交和扫描电镜分析，发现两株菌可以在水稻根部定殖，并进入水稻根部的维管组织和细胞间隙。水稻转录组学分析表明，两株菌通过激活水稻中的超敏反应和防御感应系统来增强水稻对镉的抗性。此外，两株菌产生的代谢产物琥珀酸和苯丙氨酸可以激活水稻根部镉结合蛋白和镉外排蛋白的表达，抑制镉摄入蛋白的表达，从而减少水稻中镉的含量。
该研究发现了一种新的菌植互作降低水稻镉吸收的现象并阐明了其机制，其研究结果为菌植互作在镉污染修复中的重要作用揭开了新的一页，具有重要理论价值和应用潜力。
我校生命科学技术学院博士后王杏为论文第一作者，王革娇教授和史凯祥副研究员为通讯作者。该研究得到国家自然科学基金和华中农业大学自主科技创新基金的资助。
【英文摘要】
The accumulation of cadmium （Cd） in plants is strongly impacted by soil microbes, but its mechanism remains poorly understood. Here, we report the mechanism of reduced Cd accumulation in rice by coculture of Enterobacter and Comamonas. In pot experiments, inoculation with the coculture decreased Cd content in rice grain and increased non-bioavailable Cd amount in Cd-spiked soils. Fluorescence in situ hybridization （FISH） and scanning electron microscopy （SEM） detection showed that the coculture colonized in the rhizosphere and rice roots' vascular tissue and intercellular space. Soil metagenomics data showed that the coculture increased the abundance of sulfate reduction and biofilm formation genes and related bacterial species. Moreover, the coculture increased the content of organic matter, available nitrogen, and potassium, and increased the activities of arylsulfatase, β-galactosidase, phenoloxidase, arylamidase, urease, dehydrogenase, and peroxidase in soils. In subsequent rice transcriptomics assays, we found that the inoculation with coculture activated hypersensitive response, defense-related induction, and MAPK signaling pathway in rice. Heterologous protein expression in yeast confirmed the function of four Cd binding proteins （HIP28-1, HIP28-4, BCP2, and CID8）， a Cd efflux protein （BCP1）， and three Cd uptake proteins （COPT4, NRAM5, and HKT6） in rice. Succinic acid and phenylalanine were subsequently proved to inhibit rice Cd（II） uptake and activate Cd（II） efflux in rice roots. Thus, we propose a model that the coculture protects rice against Cd stress via Cd immobilization in soils and reducing Cd uptake in rice.
论文链接： https://doi.org/10.1094/MPMI-09-22-0186-R
