植物内生菌Bacillus megaterium YJB3降低菜心吸收累积PAEs的机理研究

Substantial phthalate esters (PAEs) pollution in soils and vegetables has been found in many areas across China, which has adversely affected the safety of agricultural products and thus increases health risk for humans through dietary ingestion. Therefore, there is an urgency to reduce uptake and accumulation of PAEs by vegetables. In our previous study, we have screened out low-PAE accumulating cultivar of Chinese flowering cabbage (Brassica parachinensis L.) and PAEs-degrading endophytic bacterium, and ensured that the inoculation of Chinese flowering cabbage with this strain can significantly reduce the concentration of PAEs. However, the mechanisms involved are not yet well understood. The present project will study the mechanisms of action of endophytic inoculation on environmental behavior of PAEs at the micro-interface in rhizospheric soil. Moreover, this project will further investigate the effects of inoculation of endophyte on the physiological and biochemical processes of Chinese flowering cabbage involved in lowering accumulation of PAEs, elucidate the enzymatic mechanisms of enhanced biotransformation of PAEs in endophyte-inoculated Chinese flowering cabbage by investigating the subcellular distribution of PAEs and related metabolic products and the activities of PAE-degrading enzymes, reveal the molecular biology mechanisms of enhanced transformation of PAEs in Chinese flowering cabbage through comparative transcriptome and iTRAQ proteome analysis for identifying differentially expressed genes and proteins of endophyte-inoculated Chinese flowering cabbage. It will provide an important insight in endophyte-aided reduction of uptake and accumulation of PAEs in Chinese flowering cabbage and scientific basis for the safe qualities of agricultural products.

我国土壤和蔬菜邻苯二甲酸酯（PAEs）污染普遍，严重危害农产品安全和人体健康。我们前期筛选获得了PAEs低累积菜心品种和降解PAEs植物内生菌，明确了接种该菌能进一步显著降低菜心体内PAEs含量，但其机理尚不清楚。本项目拟研究内生菌对根际土壤微界面PAEs环境行为的作用机制；探讨内生菌对菜心吸收累积PAEs的生理生化的影响过程；通过考察内生菌定殖的菜心体内PAEs亚细胞分配、代谢产物分布、代谢酶活性，查明内生菌促进菜心体内代谢PAEs的酶学机制；采用转录组学和蛋白组学比较分析内生菌定殖的菜心在代谢PAEs过程中的关键基因（或蛋白）差异表达，阐明内生菌促进菜心代谢PAEs的分子机制。从而将揭示植物内生菌降低菜心吸收累积PAEs的机理，为高效利用污染土壤生产安全农产品提供科学依据。

邻苯二甲酸酯（PAEs）是一类具有环境激素性质的新污染物，土壤和蔬菜PAEs污染问题受到广泛关注。具有PAEs降解功能的内生菌YJB3可以有效降低蔬菜PAEs污染，但其机理尚不清楚。本项目重点围绕着功能内生菌-蔬菜系统对根际微界面PAEs迁移分布的影响及机制、菌株YJB3定殖的菜心吸收累积PAEs的生理生化、酶学和分子生物学机制等方面开展研究。研究了菌株YJB3在菜心体内定殖和分布特征、菜心体内PAEs亚细胞分布、吸收动力学、迁移富集系数等，明确了菌株YJB3的定殖能够显著降低菜心累积PAEs；分析了菌株YJB3定殖的菜心根系表型、根际土壤理化性质、土壤酶活性、PAEs赋存形态及不同根区细菌多样性和群落结构特征，阐明了菌株YJB3-植物系统互作促进根际微界面PAEs降解的作用机制；研究了菌株YJB3对菜心生长、光合作用、糖代谢、活性氧代谢和植物激素代谢等方面的影响，阐明了菌株YJB3降低菜心吸收累积PAEs的生理生化机制和酶学机制；利用转录组测序，结合RT-qPCR技术，明确了菜心糖代谢、活性氧代谢和植物激素代谢途径中受菌株YJB3调控的相关通路及相关基因的分子调控网络，初步揭示了菌株YJB3降低菜心吸收累积和抵御PAEs胁迫的过程中分子机理。研究结果增加了对功能内生菌YJB3降低菜心吸收累积PAEs作用机理的新认识，为合理利用污染农田土壤和保障农产品安全提供理论依据和技术支持。