Communities and populations of sebacinoid basidiomycetes associated with the achlorophyllous orchid Neottia nidus-avis (L.) LCM Rich. and neighbouring tree ectomycorrhizae
Communities and populations of sebacinoid basidiomycetes associated with the achlorophyllous orchid Neottia nidus-avis (L.) LCM Rich. and neighbouring tree ectomycorrhizae
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DOI：
10.1046/j.1365-294x.2002.01553.x
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发表时间：
2002-09-01
影响因子：
4.9
通讯作者：
Tillier, A
中科院分区：
文献类型：
--
作者：
Selosse, MA;Weiss, M;Tillier, A
几种非绿叶兰花与外生菌根膜菌联系在一起，为植物从周围的树木中获取碳。然而，与丝核菌相关的非绿叶兰花却没有表现出这一点，丝核菌是最常见的兰花伙伴，由膜菌的基本谱系组成的复合体。我们分析了一种与丝核菌共生的非绿叶兰科植物新丝核兰属，通过内部转录间隔区(ITS)测序鉴定了其共生体。对23个法国居群的61个根系的分析表明，北极星与一组番泻科植物有很高的专一性。它们的多样性强调了对景天科系统学进行进一步研究的必要性。在兰科植物种群内，Sebacinid ITS序列往往是相同的，并观察到共生体有区域变异的趋势。利用ITS和基因间隔区(IGS)的多态性，我们发现每个根系统只有一个物种，但有几个基因定植它。然而，这些标记在每个根的不同部分之间没有发现多态性：这与真菌从根茎进入根的假定模式一致，但不是从土壤重复进入。此外，外生菌根总是存在于北冰草的根系中：在144个外生菌根中，有120个外生菌根由一种与各自兰花共生体序列相同的番荔枝状真菌定植(在某些情况下甚至存在IGS多态)。由于番泻素类化合物最近被证明是外生菌根，兰花的资源可能来自周围的树木，这是一种菌根欺骗策略，类似于迄今研究的其他菌根异养植物。
Several achlorophyllous orchids associate with ectomycorrhizal hymenomycetes deriving carbon from surrounding trees for the plant. However, this has not been shown for achlorophyllous orchids associating with species of Rhizoctonia , a complex of basal lineages of hymenomycetes that are the most common orchid partners. We analysed Neottia nidus-avis , an achlorophyllous orchid symbiotic with a Rhizoctonia , to identify its symbionts by internal transcribed spacer (ITS) sequencing. Analysis of 61 root systems from 23 French populations showed that N. nidus-avis associates highly specifically with a group of species of Sebacinaceae. Their diversity emphasizes the need for further investigations in the Sebacinaceae systematics. Sebacinoid ITS sequences were often identical within orchid populations and a trend to regional variation in symbionts was observed. Using ITS and intergenic spacer (IGS) polymorphism, we showed that each root system harboured a single species, but that several genets colonized it. However, no polymorphism of these markers was found among portions of each root: this is consistent with the putative mode of entry of the fungus, i.e. from the rhizome into roots but not repeatedly from the soil. In addition, ectomycorrhizae were always found within the N. nidus-avis root systems: 120 of the 144 ectomycorrhizae typed by ITS sequencing were colonized by a sebacinoid fungus identical in ITS sequence to the respective orchid symbiont (even for the IGS polymorphism in some cases). Because sebacinoids were demonstrated recently to be ectomycorrhizal, the orchid is likely to derive its resources from surrounding trees, a mycorrhizal cheating strategy similar to other myco-heterotrophic plants studied to date.