利用微生物强化植物萃取是修复土壤重金属污染的有效途径。有益微生物可通过诱导植物合成水杨酸(SA)来缓解重金属毒害，然而诱导因子及其调控机制尚不明确。申请者在前期研究中发现，镉胁迫下巨大芽孢杆菌NCT-2的分泌蛋白是调控龙葵SA合成的重要诱导因子，但其种类和调控方式有待进一步深入研究。本课题拟采用分泌蛋白质组学技术系统解析镉胁迫下NCT-2菌株的差异分泌蛋白，结合生物信息学分析预测分泌蛋白种类，通过构建随机组合基因缺失突变菌株明确有效分泌蛋白；利用GST pull-down、EMSA等方法，考察分泌蛋白对SA合成酶及其转录因子的调控作用；通过有效分泌蛋白过表达、转染龙葵等手段促进SA合成，探讨微生物分泌蛋白提高龙葵萃取镉的普适性，揭示NCT-2菌株对龙葵SA合成的诱导机制。本研究为发挥芽孢杆菌等有益微生物的生物强化修复作用提供科学依据，同时为提高超积累植物萃取镉的效率提供理论依据和技术支持。

The strengthen measure of microorganisms on phytoextraction is effective for remediation of heavy metal contaminated soils. Beneficial microbes can alleviate the toxicity of heavy metals by inducing synthesis of salicylic acid (SA) in plant, however, the inducing factors and regulatory mechanisms are not clear yet. It was shown that under cadmium stress, the secretory protein of Bacillus megaterium NCT-2 was essential for inducing SA synthesis in S. nigrum L., but the types of protein and its regulatory mechanism need to be further studied. For B. megaterium NCT-2, the different proteins will be systematically investigated by secretome under cadmium stress. Then the protein types will be analyzed by bioinformatics. The shuffling genes deletion mutants will be constructed to identify the types of proteins which could induce the synthesis of SA . After that, the regulatory effects of secretory proteins on SA synthase and its key transcription factors will be investigated through GST pull-down and EMSA. Finally, the effective secretory proteins will be overexpressioned in B. megaterium NCT-2 and S. nigrum L. to promote the synthesis of SA. The general applicability of strengthen measure of microbial secretory proteins on cadmium phytoextraction will be understand, as well as the induction mechanism of SA synthesis. The study will provide theoretical basis for the strengthen measure of beneficial microbes, such as Bacillus, which are effective on remediation of heavy metal contaminated soils，and provide technical support for for improving cadmium phytoextraction efficiency.