特异性积累土壤中镉的大型真菌富镉机理研究

Some macrofungi has stronger cadmium bioaccumulation ability than green plants, especially some species in certain genera have hyper-bioaccumulative potential, such as Agaricus macrosporus and A.silvicola in Agaricus spp. Even some species can accumulate very high cadmium contents in fruiting body from unpolluted or little polluted soil and the BCF could exceed 300.By the characteristics of strong cadmium bioaccumulation ability, species and environment denpendence, some macrofungi could be as indicator for cadmium polluted soil; some could be auxiliary bio-material for remediation contaminated soil and promote phytoremediation.For explaining the phenomenon of cadmium biocentration by macrofungi, there are many hypothesis, but lack of the direct and powerful evidence.This program, on the base of studying species dependence and spatial differences of cadmium bioconcentration , preferentially selecting strains with high ability in mercury bioaccumulation, will concurrently research the outer environmental and inner cellular mechanisms including uptake, distribution and transportation also mechanisms of mycelium’s cadmium concentration in cellular partition.The purpose is mastering characteristics of macrofungi’s cadmium bioconcentration, establishing relationship between fungi bioconcentration and outer environment, obtaining strains with high cadmium concentration ability, obtaining direct and powerful evidences in explaining bioconcentration mechanisms，providing guaidance for safe consumtion of edible fungi, providing suggestions for cadmium contaminated soil phytoremediation.

某些大型真菌有很强的积累镉能力，特别是一些属的某些种富集镉能力极强，如蘑菇属中的大孢蘑菇、白林地蘑菇，体内镉含量达28-101mg/kg鲜重。一些种即使在环境未受或微受镉污染的情况下，体内镉含量也很高，BCF值可超过300。籍真菌强烈的镉富集能力和种的特异性及受环境的影响性，某些真菌可望作为镉污染土壤指示生物，某些可成为土壤污染治理和促进植物修复的辅助材料。为解释大型真菌富集镉的现象，有过多种假设，但尚缺乏直接而有力的证据。本项目在大型真菌生物富集镉的种特异性和空间分异研究的基础上，优选对镉富集能力强的菌株，开展环境外部机制和细胞内部机制的并行研究，包括体内镉的吸收、分布和转移及胞内分区菌丝体富集镉的机制。掌握真菌富集镉的特点，建立真菌富镉与外部环境的相互关系，获得富镉能力强的菌株和科学解释特异积累土壤中镉的大型真菌富镉机理的直接证据。为食用菌消费提供指导，为镉污染土壤的植物修复建议菌株。

框栽出菇试验发现，双孢蘑菇（Agaricus bisporus）对 Cd 具有较强的耐受和积累能力，能够忍受浓度414 mg Cd/kg风干土，完成正常完整的生命周期，菌盖是 Cd 的主要积累部位，Cd 含量最高，可达18.38 mg/kg干重。双孢蘑菇的盐酸提取态Cd是主要化学存在形态，储存于可溶性组分中。Cd的胁迫时间和胁迫浓度均对双孢蘑菇生理生化代谢产生强烈影响，导致体内可溶性蛋白质、糖、丙二醛和脯氨酸强烈变化，同时激活抗氧化系统的强烈反应和有机酸代谢响应。代谢组学研究发现，Cd胁迫能导致双孢蘑菇代谢改变，82种代谢物质的含量在无Cd和Cd胁迫处理间存在显著差异，差异代谢物被注释到59条KEGG代谢途径，主要涉及的路径为代谢、次级代谢、氨基酸生物合成、甘油磷脂代谢和苯丙酸生物合成等。转录组学研究发现，在无Cd和Cd胁迫处理间共有165个基因存在显著性差异，主要涉及与重金属解毒有关的催化活性、相关转运活性和抗氧化活性等，参与氨基酸代谢和减数分裂等过程。研究成果为 Cd污染土壤的生物修复提供理论和技术支撑。