丛枝菌根真菌分泌球囊霉素对植物吸收PAHs的影响及机制

Polycyclic aromatic hydrocarbons (PAHs) are recognized as a group of persistent organic pollutants (POPs), and demonstrate carcinogenic and mutagenic toxicities. PAHs were frequently observed in soils at relatively high concentrations (at mg/kg) all over the world. Plants can absorb these contaminants from soils, and cause deleterious impacts to human and animal health via consumption of the contaminated vegetables. Therefore, an improved understanding of plant uptake of PAHs is essential to assessing the exposure to humans and ecological species and potential risk of PAH-contaminated sites. How to reduce the uptake of PAHs as well as other POPs by plants is of worldwide concerns. Plant-microbe symbioses are ubiquitous in the environment. As the most widespread type of mycorrhizae, arbuscular mycorrhizal fungi (AMF) are drrawing much attention. Recent studies have shown that AMF have positive effects on plant establishment, survival in contaminated soils, and lower the accumulation of PAHs in shoots, suggesting the potential of AMF in reducing plant risks of PAHs. Unfornately, the involved mechanisms are hitherto still under elucidation. Glomalin (or glomalin-related soil protein) is produced by AMF. The contents of glomalin were 2~24 times larger than that of humus in soil, and accounts at most for 27% of the total soil organic carbons. However, little information is available on the function of glomalin in the uptake of PAHs by plants. To this end, utilizing the isotope technique, nuclear magnetic resonance (NMR), laser scanning confocal microscopy (LSCM), and other analysis techniques, this project seeks to (1) elucidate the responses of glomalin released by AMF to the soil PAH contamiation, and reveal the distribution, composition, and structure of glomalin obtained under test conditions; (2) investigate the impacts of glomalin on the uptake of PAHs by plants; (3) clarify the involved mechnisms of the glomalin-influenced uptake of PAHs by plants, basing on the observations of glomalin-PAH combination, glomalin-influenced forms and availability of PAHs in soil, and glomalin-influenced activity of enzymes in inner plants. To our knowledge, this is a primary investigation into the correlations of AMF-released glomalin with plant uptake of PAHs. Results of this work would provide insight into the glomalin-influenced uptake of PAHs by plants, and contribute a new perspective that the application of AMF and glomalin potentially reduces the accumulation of organic contaminants in plants, hence reducing the risks to food safety and human health.

利用与植物共生的丛枝菌根真菌（AMF），有望调控植物吸收多环芳烃（PAHs）、进而规避植物污染风险；但至今AMF影响植物吸收PAHs的内在本质仍不甚清楚。球囊酶素是迄今发现的唯一一类由AMF菌丝产生并释放到土壤中的蛋白质。本项目尝试研究AMF分泌球囊霉素对PAHs污染的响应，分析土壤中球囊霉素的时空分布及组成，研究球囊霉素对土壤中PAHs有效性的影响，探讨球囊霉素影响植物吸收PAHs的基本规律。通过开展本项目，试图为进一步利用AMF及球囊霉素调控植物吸收PAHs、减低作物污染风险、保障农产品安全、指导农业安全生产等提供思路和依据。

球囊酶素相关土壤蛋白（GRSP）是土壤有机质的重要组成部分，也是土壤中最重要的碳库之一，其含量是腐殖质的2~24倍，占土壤有机碳源的比例可高达27%。然而，丛枝菌根真菌分泌GRSP对土壤中PAHs环境行为和植物吸收有何影响？国内外相关研究仍几近空白。本项目为两年期小额预研项目，取得的主要研究成果：（1）揭示了林地、草地、水稻田、茶园土、菜园土等不同土地利用方式土壤中GRSP的含量、组成及剖面分布特征，明确了总球囊酶素相关土壤蛋白（T-GRSP）和易提取球囊酶素相关土壤蛋白（EE-GRSP）的含量与土壤因子的相关性。（2）阐明了PAHs污染土壤中GRSP对接种丛枝菌根真菌（AMF）的响应。以侵染率、丛枝率、菌根长度、菌丝密度、泡囊数、孢子数为指标，系统地解析了PAHs污染对AMF生物学性状的影响，探明了接种AMF对菲污染土壤中GRSP含量的影响，明确了土壤中PAHs残留与GRSP含量间的关系。（3）揭示了GRSP与PAHs的结合作用，阐明了GRSP对土壤中PAHs吸附、解吸和有效性的影响。发现EE-GRSP和T-GRSP（~50mg/L）抑制了几种地带性土壤吸附PAHs；T-GRSP和EE-GRSP（~60mg/L）均能促进土壤中菲、芘的解吸，但同一浓度下T-GRSP对PAHs解吸的促进作用强于EE-GRSP；加入T-GRSP和EE-GRSP（~60mg/kg）显著提高土壤中PAHs的有效性。（4）阐明了GRSP对植物吸收PAHs的影响。以萘、苊、菲、荧蒽和芘为PAHs的代表，采用水培体系，揭示了外加T-GRSP和EE-GRSP对黑麦草吸收PAHs的影响，解析了GRSP作用下弱吸附态、强吸附态和吸收态PAHs对根中PAHs积累的贡献，明确了T-GRSP和EE-GRSP影响根和茎叶中PAHs积累的差异。依托本项目，发表论文16篇，其中SCI论文11篇。研究成果揭示了GRSP对土壤中PAHs环境行为和植物吸收的影响，这将为进一步利用AMF和GRSP来减低土壤和作物PAHs污染风险、保障污染区农产品安全等提供基础依据。依托本项目，开展国际合作与交流2人次，培养博士/硕士研究生4名。