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北京林業大學丨菌根通過維持植物NO3-的吸收以應對鹽脅迫
期刊：New Phytologist
主題：菌根通過維持植物NO3-的吸收以應對鹽脅迫
標題：Amelioration of nitrate uptake under salt stress by ectomycorrhiza with and without a Hartig net
影響因子：7.433
檢測指標：NO3-流速
檢測部位：楊樹根（距離根尖300-400μm）
NO3-流速流實驗處理方法：
小植株楊樹在無/有菌株（MAJ和NAU）的情況下培養30d，之后在0或100mM NaCl處理24h/7d
NO3-流速流實驗測試液成份：
NO3- measuring solution: 0.1 mM KNO3, 0.1 mM KCl, 0.1 mM CaCl2, pH 5.3 was adjusted with KOH and HCl.
H+ measuring solution: 0.1 mM NaCl, 0.1 mM MgCl2, 0.1 mM CaCl2 and 0.5 mM KCl, pH 5.3 was adjusted with KOH and HCl.
作者：北京林業大學陳少良、撒剛、鄧晨
英文摘要
Salt stress is an important environmental cue impeding poplar nitrogen nutrition. Here, we characterized the impact of salinity on proton‐driven nitrate fluxes in ectomycorrhizal roots and the importance of a Hartig net for nitrate uptake.
We employed two Paxillus involutus strains for root colonization: MAJ, which forms typical ectomycorrhizal structures (mantle and Hartig net), and NAU, colonizing roots with a thin, loose hyphal sheath. Fungus‐colonized and noncolonized Populus × canescens were exposed to sodium chloride and used to measure root surface pH, nitrate (NO3−) flux and transcription of NO3− transporters (NRTs; PcNRT1.1, ‐1.2, ‐2.1), and plasmalemma proton ATPases (HAs; PcHA4, ‐8, ‐11).
Paxillus colonization enhanced root NO3− uptake, decreased surface pH, and stimulated NRTs and HA4 of the host regardless the presence or absence of a Hartig net. Under salt stress, noncolonized roots exhibited strong net NO3− efflux, whereas beneficial effects of fungal colonization on surface pH and HAs prevented NO3− loss. Inhibition of HAs abolished NO3− influx under all conditions.
We found that stimulation of HAs was crucial for the beneficial influence of ectomycorrhiza on NO3− uptake, whereas the presence of a Hartig net was not required for improved NO3− translocation. Mycorrhizas may contribute to host adaptation to salt‐affected environments by keeping up NO3− nutrition.
中文摘要（谷歌機翻）
鹽脅迫是阻礙楊樹氮素營養的重要環境提示。在這里，我們描述了鹽度對外生菌根中質子驅動的**鹽通量的影響以及Hartig網對**鹽吸收的重要性。
我們采用了兩種漸開線Paxillus菌株進行根定居：MAJ形成典型的外生菌根結構（地幔和Hartig網），而NAU則定植帶有薄而疏松的菌絲鞘的根。將真菌定殖的和非定殖的楊×錐蟲暴露于氯化鈉中，用于測量根部表面的pH值，**鹽（NO3-）通量和NO3-轉運蛋白（NRT； PcNRT1.1，-1.2，-2.1）和質膜質子的轉錄。 ATPase（HAs; PcHA4，‐8，‐11）。
不論是否存在Hartig網，Paxillus菌落定植都能增強根系NO3-的吸收，降低表面pH值并刺激宿主的NRT和HA4。在鹽脅迫下，未定殖的根表現出較強的凈NO3-流出，而真菌定植對表面pH和HA的有益作用阻止了NO3-的流失。在所有情況下，抑制HA均消除了NO3-的涌入。
我們發現刺激HAs對于更生菌根對NO3-吸收的有益影響至關重要，而Hartig網的存在并不是改善NO3-轉運所必需的。菌根可能會通過保持NO3-營養來促進宿主適應食鹽環境。
結果表明：NM根尖顯示中等的NO3-吸收，而真菌定殖的根則顯示高7.4至11.8倍的吸收（圖a）。MAJ或NAU菌根定植與NM根相比，NO3-吸收增加（圖a）。此外，真菌定殖的根在鹽度下保持凈NO3-吸收，而NM根在短期和長期鹽接觸下均顯示凈NO3-釋放。