鎘是引起糧食減產(chǎn)的主要金屬之一，其具有高溶解性及高遷移性，易被植物吸收和積累。近年來農(nóng)田土壤鎘污染修復(fù)成為國內(nèi)外學(xué)者研究的熱點(diǎn)，微生物參與了水稻對土壤中鎘的吸收，然而微生物如何影響水稻對土壤鎘吸收及解毒的分子機(jī)制并不清楚。

 

　　課題組發(fā)現(xiàn)了當(dāng)腸桿菌和叢毛單胞菌共同培養(yǎng)時(shí)，可以將溶液中的鎘離子沉淀并完全去除。將這種混合菌劑應(yīng)用于鎘污染水稻盆栽實(shí)驗(yàn)中，該混合菌劑可以有效鈍化土壤中的鎘，減少水稻對鎘離子的吸收，使稻米中鎘含量顯著下降。采用原位雜交和掃描電鏡分析，發(fā)現(xiàn)兩株菌可以在水稻根部定殖，并進(jìn)入水稻根部的維管組織和細(xì)胞間隙。水稻轉(zhuǎn)錄組學(xué)分析表明，兩株菌通過激活水稻中的超敏反應(yīng)和防御感應(yīng)系統(tǒng)來增強(qiáng)水稻對鎘的抗性。此外，兩株菌產(chǎn)生的代謝產(chǎn)物琥珀酸和苯丙氨酸可以激活水稻根部鎘結(jié)合蛋白和鎘外排蛋白的表達(dá)，抑制鎘攝入蛋白的表達(dá)，從而減少水稻中鎘的含量。

 

　　該研究發(fā)現(xiàn)了一種新的菌植互作降低水稻鎘吸收的現(xiàn)象并闡明了其機(jī)制，其研究結(jié)果為菌植互作在鎘污染修復(fù)中的重要作用揭開了新的一頁，具有重要理論價(jià)值和應(yīng)用潛力。

 

　　我校生命科學(xué)技術(shù)學(xué)院博士后王杏為論文第一作者，王革嬌教授和史凱祥副研究員為通訊作者。該研究得到國家自然科學(xué)基金和華中農(nóng)業(yè)大學(xué)自主科技創(chuàng)新基金的資助。

 

　　【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.

 

　　論文鏈接： https://doi.org/10.1094/MPMI-09-22-0186-R