铝胁迫下钙信号抑制剂对外生菌根真菌分泌草酸的影响

【目的】探讨铝胁迫条件下，外生菌根真菌分泌草酸的调控机理，为减轻树木铝害、指导抗（耐）铝菌株的筛选和保持森林健康奠定理论基础。【方法】以从强酸性森林土壤中分离获得的菌株Suillus luteus（Sl 08和Sl 14）、Boletus sp.（Bo 15）为材料，采用液体培养的方法，研究铝胁迫下外生菌根真菌的生长与草酸分泌的关系，以及钙信号抑制剂对抗铝菌株草酸分泌的影响。【结果】在培养液铝浓度为0.4 mmol•L-1时，Sl 14的生物量显著降低，Sl 08 和Bo 15在铝浓度达到1.2 mmol•L-1时，生物量才受到显著抑制。说明Sl 14对铝敏感，Sl 08 和Bo 15的抗铝性较强。同时，Sl 14的草酸分泌量很低，不随铝浓度的增加而变化；Sl 08 和Bo 15在铝浓度为0.2—0.8 mmol•L-1范围内，随铝浓度提高草酸分泌量显著增加，说明草酸分泌是外生菌根真菌拮抗铝胁迫的重要因子。无铝培养时，钙离子通道抑制剂异搏定（VP）、内膜钙通道抑制剂钌红（RR）、钙离子螯合剂乙二醇双（2-氨基乙基）四乙酸（EGTA）、钙调蛋白抑制剂三氟拉嗪（TFP）对Bo 15分泌草酸无显著影响，但VP、TFP和EGTA均不同程度地显著抑制Sl 08分泌草酸。说明在无铝时，Bo 15未启动钙参与诱导草酸分泌的信号转导，而Sl 08则启动了钙参与的信号转导。在铝胁迫条件下，钙信号抑制剂都不同程度地显著降低Sl 08和Bo 15分泌草酸。说明铝诱导下，Bo 15和 Sl 08的草酸分泌均受到钙信号转导的调控。其中，Bo 15分泌草酸对TFP敏感；而Sl 08分泌草酸对RR和TFP敏感，草酸分泌量减少最多。【结论】在铝胁迫条件下，钙信号是介导外生菌根真菌分泌草酸的信号因子。

Effects of Ca2+ Signal Inhibitors on Oxalate Effluxes by Ectomycorrhizal Fungi Under Aluminum Stress

【Objective】 An experiment was carried out to study the mechanism of oxalate effluxes by ectomycorrhizal fungi (ECMF) under Al stress and to establish a theoretical foundation for alleviating the Al toxicity of trees, guide the selection of Al-resisted ECMF and preserve forest health. 【Method】 The growth and the oxalate effluxes by ectomycorrhizal species, Suillus luteus (Sl 08 and Sl 14 ) and Boletus sp. (Bo 15), which were isolated from acid forest soil, were studied in pure culture in liquid media with variable concentrations of Al3+ and Ca2+ signal inhibitors. 【Result】 Compared to the control without Al3+, when Al3+ concentration was 0.4 mmol•L-1, the growth of Sl 14 was inhibited significantly. But the growth of Sl 08 and Bo 15 was inhibited significantly in 1.2 mmol•L-1 Al3+ culture. It was showed that Sl 14 was sensitive to Al; Sl 08 and Bo 15 were resistant to Al. Meanwhile, the oxalate efflux by Sl 14 was few and invariable with the increase of Al3+ concentration in culture. But the oxalate effluxes by Sl 08 and Bo 15 increased with the increase of Al3+ concentration in the range of 0.2-0.8 mmol•L-1 Al3+ culture. It showed that the oxalate effluxes by ECMF were closely related with the tolerance of ECMF to Al. In the culture without Al3+, compared to without Ca2+ signal inhibitors, there was no significant change in the oxalate efflux by Bo 15 in the respective presence of verapamil (VP), ruthenium red (RR), trifluoperazine (TFP) and ethylene glycol tetraacetic acid (EGTA), while the oxalate efflux by Sl 08 was decreased significantly in the respective presence of VP, TFP, and EGTA. So Ca2+ signals could regulate oxalate efflux by Sl 08 but not by Bo 15 in culture without Al3+. Under Al stress, however, the oxalate effluxes by Sl 08 and Bo 15 were reduced significantly by four Ca2+ signal inhibitors. It was showed that Ca2+ signals could regulate oxalate efflux by Sl 08 and Bo 15 under Al stress. Oxalate efflux by Bo 15 was most sensitive to TFP, which led oxalate effluxes to a most greatly reduction, and Sl 08 was most sensitive to RR and TFP, compared to any other Ca2+ signal inhibitors.【Conclusion】 These results showed that Ca2+ signal participated in oxalate effluxes to accommodate Al stress in the fungi.