磷与信号抑制剂对外生菌根真菌分泌草酸的调控作用

Effect of phosphorus supply and signal inhibitors on oxalate efflux in ectomycorrhizal fungi

【目的】磷是树木生长的必需营养元素之一,磷素营养丰缺条件下,研究外生菌根真菌的草酸分泌及调控有益于揭示它们活化利用土壤无机磷的机理。【方法】试验设置低、正常、高3种不同磷浓度,液体培养外生菌根真菌,研究了磷和Ca2+信号/阴离子通道抑制剂对草酸分泌的调控作用。【结果】外生菌根真菌能分泌大量的氢离子和草酸、乙酸、苹果酸、柠檬酸和丁二酸等多种有机酸,对溶解难溶性无机磷有重要作用。在外生菌根真菌分泌的有机酸中,草酸占15.14%-36.01%;低磷促进草酸分泌,正常和高磷则产生抑制作用;培养液磷浓度和菌丝含磷量分别与供试菌种的草酸分泌速率呈显著或极显著负相关,相关系数依次为r=-0.264*和r=-0.349**,n=60,*表示显著(P0.05),**表示极显著(P0.01),说明磷能调控外生菌根真菌分泌草酸。在低磷胁迫下,钙调蛋白抑制剂、Ca2+通道抑制剂、Ca2+内膜通道抑制剂和阴离子通道抑制剂显著抑制外生菌根真菌分泌草酸。但是,在正常和高磷条件下,草酸分泌速率低,未响应Ca2+信号/阴离子通道抑制剂。【结论】供试外生菌根真菌能分泌大量的氢离子和有机酸(尤其是草酸),有益于溶解土壤无机磷,改善寄主植物的磷营养;供磷水平调控草酸分泌速率;在低磷胁迫下,Ca2+信号是介导外生菌根真菌分泌草酸的信号因子。

[Objective] Phosphorous（P） is one of the essential elements for tree growth in forests.It is beneficial to characterize oxalate secretion by ectomycorrhizal fungi in response to P supply for understanding the mechanism of P mobilization in soils.[Method] In the present experiment,the influence of P supplies and inhibitors of Ca2 ＋signal /anion channel on oxalate efflux in ectomycorrhizal fungi was studied in the pure liquid culture with various P concentrations.[Results] Ectomycorrhizal fungi released a large amount of H＋and organic acids such as oxalate,acetate,malate,citrate and succinate,which are important for mobilization of insoluble P in the soils.Oxalate accounted for 15.14% to 36.01% of the total organic acids released by the fungi and was accelerated in culture solution under the condition of low P supply,but inhibited under normal and high P.[Conclusion] Ectomycorrhizal fungi released a large amount of H＋and organic acids,particularly oxalate,which might be beneficial to inorganic P mobilization in the soils and improvement of P nutrition for their host plants.