玉米-微生物相互作用对玉米吸收累积邻苯二甲酸酯的影响及机理

Phthalic acid esters (PAEs) are a class of organic contaminants with endocrine disrupting effects. At present, many studies have focused on plant-promoted microbial degradation of organic contaminants (e.g., PAEs) in soil. Nevertheless, the effects of the interaction between plant and microorganism on the environmental process of organic contaminants in soil and its mechanism remain unclear, especially on the uptake and accumulation of organic contaminants by crops. This project will be focused on the high risk area of PAEs in agricultural soil of China. Efficient PAE-degrading strain and low-PAE accumulation cultivar of maize (Zea mays) screened previously by our team will be selected as materials. Series experiments including pot experiments, in vivo plant experiments, and batch experiments will be conducted. The samples of plants, soil and solution will be collected, and PAEs in these samples will be extracted and measured by gas chromatography coupled with mass spectrometry (GC/MS). Microbial communities in rhizospheric and non- rhizospheric soil will be investigated by high-throughput sequencing and quantitative real-time PCR. This project will be aimed to (1) investigate the effects of the interaction between plant and microorganism, especially between plant roots (including its exudates) and PAE-degrading strain (including extracellular polymeric substances), on the activation and sequestration (corresponding sorption and desorption) of PAEs in soil; (2) explore the metabolism and degradation of PAEs by plant enzymes, rhizospheric microorganism, and PAE-degrading strain (including plant endophyte and extracellular polymeric substances) as well as their interaction; (3) observe the colonization of PAE-degrading strain marked with a green fluorescent protein in roots of maize by confocal laser scanning microscopy and investigate its effect on uptake and accumulation of PAEs by maize. All results above will be helpful to elucidate the effects of the interaction between plant and microorganism on uptake and accumulation of PAEs by maize and its mechanism, and will provide scientific basis for bioremediation of soil contaminated by organic contaminants and for the safety of agricultural products.

邻苯二甲酸酯(PAEs)是一类具有内分泌干扰效应的有机污染物。目前国内外对植物促进微生物降解土壤PAEs等有机污染物研究较多，但关于作物-微生物互作对土壤有机污染物环境过程(尤其是作物吸收累积有机污染物)的影响及机制尚不明确。本项目拟针对我国农田土壤PAEs高风险区，在前期筛选获得PAEs高效降解菌和PAEs低累积玉米品种的基础上，利用盆栽试验和组培实验及批处理方法，采用气相色谱-质谱联机分析和微生物高通量测序技术，研究玉米与微生物互作尤其是根系(及分泌物) 与降解菌(及胞外聚合物)对土壤PAEs的活化/锁定(吸附/解吸)作用，探讨植物酶、根际微生物与降解菌等互作对PAEs的代谢降解及机制，并采用绿色荧光蛋白技术结合激光共聚焦显微镜观察降解菌在玉米根系定殖情况及对玉米累积PAEs影响，从而阐明玉米与微生物互作对玉米吸收累积的影响及机理，为污染土壤生物修复和保障农产品安全提供科学依据。

邻苯二甲酸酯(PAE)是一类全球关注的毒性有机污染物。本项目针对我国农田土壤普遍受到PAEs污染的突出问题，采用合成微生物和高通量测序技术等方法研究植物-微生物相互作用及其对土壤-植物系统PAEs去除的影响机制。项目筛选获得了PAE高效降解菌群，研究了降解菌群胞外聚合物、不同土壤组分、根系分泌物等对PAE的吸附-解吸作用，揭示了它们对土壤PAE的促溶解效果和锁定作用的影响机制。而且PAE降解菌群和土壤微生物接种于玉米无菌苗根际对土壤PAE具有活化作用，提高了土壤PAE的生物有效性、促进土壤PAE消减。16S rRNA高通量测序揭示，玉米根际生态位间（非根际-根际-根表-根内）细菌群落结构多样性、结构和功能组成均存在显著的差异，且PAE污染使细菌群落多样性差异更显著、与植物共生的根表细菌群落多样性降低、共现网络复杂性提高。采用合成微生物技术分别构建了来源于土壤和根系组织的细菌菌群并研究其在玉米根表面的定殖规律。绿色荧光蛋白标记技术结合扫描电镜和高通量测序结果证明，来源于根系组织的合成菌群能成功在玉米根表定殖，激发了玉米的免疫应答，提高根系植物激素水平，且合成菌群能在玉米根表面形成生物膜以避开玉米根系免疫响应，但PAE污染使定殖微生物群落多样性下降、生物膜变薄；来源于土壤的合成菌群在玉米根表定殖较少。PAE高效降解菌与合成菌群具有很好共生关系并形成生物膜，高效降解溶液和土壤中PAE，显著降低了盆栽土壤中PAE残留和玉米对PAE吸收累积，表明PAE高效降解菌和合成菌群可通过与玉米相互作用，促进土壤PAE降解和减少玉米累积PAEs。本项目从植物根系分泌物和微生物胞外聚合物对土壤PAE活化作用、合成微生物在玉米根表定殖及植物-微生物互作对土壤-植物系统PAE环境归趋等阐明了植物-微生物相互作用对玉米累积PAE的影响及机理，为保障农产品安全提供了科学依据。. 依托本项目，发表了论文18篇（其中SCI收录论文17篇）；申请专利3件，获授权专利3件；培养了2名博士后、1名博士生、9名硕士生。