Carbon uptake and the metabolism and transport of lipids in an arbuscular mycorrhiza
Carbon uptake and the metabolism and transport of lipids in an arbuscular mycorrhiza
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DOI：
10.1104/pp.120.2.587
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发表时间：
1999-06-01
期刊：
影响因子：
7.4
通讯作者：
Shachar-Hill, Y
中科院分区：
文献类型：
--
作者：
Pfeffer, PE;Douds, DD;Shachar-Hill, Y
在丛枝菌根共生中，植物和真菌都受益于营养：寄主植物获得增强的矿物质吸收，真菌获得固定碳。在这种交换中，真菌伴侣对碳的摄取、代谢和转运知之甚少。因此，我们使用核磁共振波谱分析了同位素标记的底物在丛枝菌根（由Glomus intraradices定植的Ri t - dna转化的胡萝卜根的离体培养物）中的命运。在向菌根根或根外菌丝体提供底物后，在脂质和碳水化合物中观察到的标记模式表明：(a) c -13标记的葡萄糖和果糖（但不是甘露醇或琥珀酸）被根内的真菌有效吸收并代谢产生标记的碳水化合物和脂质；(b)根外菌丝体不使用外源糖进行分解代谢、储存或向宿主转移；(c)真菌将根室吸收的糖转化为脂质，然后转运到根外菌丝体（在外部菌丝体中很少或没有脂质合成）；(d)真菌组织中的己糖通过氧化戊糖磷酸途径比宿主植物中的己糖经历更高的通量。
Both the plant and the fungus benefit nutritionally in the arbuscular mycorrhizal symbiosis: The host plant enjoys enhanced mineral uptake and the fungus receives fixed carbon. In this exchange the uptake, metabolism, and translocation of carbon by the fungal partner are poorly understood. We therefore analyzed the fate of isotopically labeled substrates in an arbuscular mycorrhiza (in vitro cultures of Ri T-DNA-transformed carrot [Daucus carota] roots colonized by Glomus intraradices) using nuclear magnetic resonance spectroscopy. Labeling patterns observed in lipids and carbohydrates after substrates were supplied to the mycorrhizal roots or the extraradical mycelium indicated that: (a) C-13-labeled glucose and fructose (but not mannitol or succinate) are effectively taken up by the fungus within the root and are metabolized to yield labeled carbohydrates and lipids; (b) the extraradical mycelium does not use exogenous sugars for catabolism, storage, or transfer to the host; (c) the fungus converts sugars taken up in the root compartment into lipids that are then translocated to the extraradical mycelium (there being little or no lipid synthesis in the external mycelium); and (d) hexose in fungal tissue undergoes substantially higher fluxes through an oxidative pentose phosphate pathway than does hexose in the host plant.