Paxillus-灰杨外生菌根CaPCs介导Cd2+富集的调控机制研究

The presence of highly toxic cadmium (Cd2+) in the environment is a serious threat to human health as heavy metals can be enriched in plants and eventually enter the human body through the food chain. The woody Cd2+ hyperaccumulator Populus × canescens can form ectomycorrhizas (EMs) with Paxillus involutus strains MAJ (compatible isolate) and NAU (incompatible isolate). It is notable to find that Paxillus involutus ectomycorrhizas enhanced both cadmium uptake and tolerance in P. × canescens. In Cd2+-polluted soils, the high external Cd2+ concentrations establish a large electrochemical gradient facilitating the rapid movement of Cd2+ ions through plasma membrane (PM) Ca2+-permeable channels (CaPCs). We attempt to explore the regulation mechanism of heavy metals uptake and enrichment in the ectomycorrhizae formed by these fungi with Populus × canescens. The EMs exhibit enhanced H2O2 production and upregulated H+-pumping activity in ectomycorrhizal roots. The aim is to elucidate whether the Cd2+ influx through CaPCs is mediated by (i) H2O2 derived from the symbioses and (ii) PM H+-ATPase in mycorrhizal roots. Moreover, we plan to examine the subcellular Cd2+ compartmentation within the ectomycorrhizal associations formed by competent strain MAJ and incompatible fungal isolate NAU. The experimental results are beneficial for utilizing ectomycorrhizal fungi to enhance the ability of trees for phytoremediation of Cd2+-polluted soils.

土壤环境中的Cd2+通过食物链危害人类健康，对重金属污染的环境进行生物修复迫在眉睫。对Cd2+具有超强富集能力的灰杨(Populus × canescens)能与卷边桩菇Paxillus involutus的兼容性菌株MAJ和非兼容性菌株NAU形成外生菌根，并进一步增强其对Cd2+的富集和耐受性。在Cd2+污染的土壤中，根际高浓度的Cd2+可顺电化学势梯度经由质膜(PM)Ca2+通透性离子通道(CaPCs)进入细胞。本项目拟探讨Paxillus-灰杨菌根PM CaPCs介导Cd2+富集的调控机制。由于P. involutus侵染灰杨产生H2O2并激活寄主细胞PM H+-ATPase，因此重点研究菌根PM H+-ATPase和共生体内的H2O2对CaPCs介导Cd2+内流的调控作用，揭示兼容性和非兼容性菌根共生体内Cd2+的区隔化模式，预期结果对利用菌根真菌提高树木生物修复能力具有重要意义。

环境中的重金属镉（Cd2+）能够通过食物链进入人体，损害人类健康。对重金属污染的土壤进行生物修复，可为生态文明建设提供重要保障。灰杨（Populus × canescens）对Cd2+具有超富集能力，在与真菌Paxillus involutus共生形成外生菌根后，能促进Cd2+在体内的积累。本项目从离子通道角度探讨了P. involutus-灰杨菌根质膜（PM）Ca2+通透性离子通道（CaPCs）介导Cd2+富集的调控机制，发现P. involutus能诱导灰杨膜联蛋白annexins的基因表达。在Cd2+胁迫下annexins可能调控CaPCs介导Cd2+的富集。P. involutus侵染灰杨产生的H2O2能提高CaPCs对Cd2+的通透性，从而促进Cd2+在菌根中的富集。再者，P. involutus侵染灰杨能上调PM H+-ATPase编码基因PcHAs的表达，调高了质子泵活性，驱动Cd2+ 通过CaPCs进行富集。本项目还比较研究了兼容性菌根（MAJ-root）与非兼容性菌根（NAU-root）对Cd2+的富集模式。研究成果能为利用菌根真菌提高树木的生物修复能力提供了理论和技术支撑。