内生真菌与宿主植物协同调控砷胁迫作用机制研究进展

Synergistic mechanism of endophytic fungi and host plants against arsenic stress

摘要:

丛枝菌根真菌(arbuscular mycorrhizal fungi, AMF)和深色有隔内生真菌(dark septate endophytes, DSE)是植物根系中最主要的两大类内生真菌，均可与植物根系形成菌根共生体，在促进植物生长，提高重金属等胁迫抗性方面发挥着重要作用。砷(arsenic, As)及砷化合物具有较强的毒性，可在植物中富集，造成生物链毒害。本团队一直致力于内生真菌与药用植物生长、活性物质合成，砷吸收、积累关系的研究，并取得了一定的进展。结合团队现有研究和前人研究成果，本文分析归纳了砷胁迫条件下，AMF定殖对宿主植物生长和砷吸收、积累的影响；详细阐述了砷胁迫条件下，宿主植物生理活动、抗氧化系统、激素水平、转录水平响应AMF调控的变化。其后，从宿主植物细胞内、外两个方面总结内生真菌与宿主植物协同调控砷胁迫的作用机制，归纳为“生长稀释效应” “菌丝隔离” “螯合过滤” “菌根固定化(mycorrhizal immobilization)” “转运体抑制效应”“生物转化作用”和“保宿主、降氧化”等7项作用机制，并绘制了不同机制之间的作用关系图。DSE-宿主植物调控砷胁迫的研究相对较少，对已有研究进行梳理归纳，发现DSE增强宿主植物砷耐性机制与AMF类似。本文对研究内生真菌与宿主植物协同调控砷胁迫作用机制，解决土壤砷污染问题，实施生态农业或中药材生态化种植，降低植物关键部位砷积累具有重要的参考价值。

Abstract:

Arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) are the two key types of root symbiotic fungi that enhance plant growth and resistance of plants to heavy metal stress. Arsenic (As) and As compounds are highly toxic, which accumulate in plants and then enter biologic chain. Our team has been committed to the study of relationship between endophytic fungi and the growth, synthesis of active substances, and arsenic absorption and accumulation of medicinal plants and has made some progress. According to our previous research outcomes and available research results, we summarized the role of AMF colonization in the growth and As uptake and accumulation in host plants under As stress, expounded the responses of host plants to AMF regulation under As stress in terms of physiological activities, antioxidant system, hormone level, and transcription level. In addition, 7 synergistic regulatory mechanisms involved in improving the As resistance were summarized at cellular level: ‘growth dilution effect’, ‘isolation of hyphae’, ‘chelating and filtration’, ‘mycorrhizal immobilization’, ‘transporter inhibition’, ‘biotransformation’, and ‘protecting the host and reducing oxidative stress’. The interaction among mechanisms was plotted. There are limited studies on the regulation of As stress by DSE-host plants. We found that the mechanism of DSE in enhancing arsenic tolerance of plants is similar to that of AMF. Our work has important reference value for studying synergistic antagonistic mechanism of endophytic fungi and host plants against As stress, alleviating As-polluted soil, implementing ecological agriculture or ecological planting of Chinese medicinal materials, and reducing As accumulation in key parts of plants.