Ectomycorrhizal Cortinarius species participate in enzymatic oxidation of humus in northern forest ecosystems
Ectomycorrhizal Cortinarius species participate in enzymatic oxidation of humus in northern forest ecosystems
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DOI：
10.1111/nph.12791
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发表时间：
2014-07-01
期刊：
影响因子：
9.4
通讯作者：
Lindahl, Bjorn D.
中科院分区：
文献类型：
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作者：
Bodeker, Inga T. M.;Clemmensen, Karina E.;Lindahl, Bjorn D.
在北方森林中，氮（N）在复杂有机库中的地下固存限制了植物的养分有效性。由外生菌根真菌产生的氧化性胞外酶可以通过在大分子复合物中提供氮来帮助植物获得氮。我们测试了这样的假设：外生菌根丝膜菌物种产生锰依赖性过氧化物酶，并且这些酶的活性在无机氮浓度升高时下降。在北方松林和亚北极桦树林中，通过ITS扩增子的454-测序评估了丝膜菌DNA，并与有和没有之前的氮修正的腐殖质样品中的锰过氧化物酶活性相关。在田间样品中研究了丝膜菌锰过氧化物酶基因的转录。通过对丝膜菌过氧化物酶扩增产物和基因组序列的系统发育分析，发现高过氧化物酶活性的丝膜菌与DNA存在明显的共定位关系。过氧化物酶活性降低高铵浓度。mRNA序列的扩增表明在田间条件下丝膜菌锰过氧化物酶基因的转录。这些结果支持了一个假设，即某些外生菌根真菌，特别是丝膜菌属的物种，可能在复杂有机物的分解中发挥重要作用，与它们动员有机结合的N有关。
In northern forests, belowground sequestration of nitrogen (N) in complex organic pools restricts nutrient availability to plants. Oxidative extracellular enzymes produced by ectomycorrhizal fungi may aid plant N acquisition by providing access to N in macromolecular complexes. We test the hypotheses that ectomycorrhizal Cortinarius species produce Mn-dependent peroxidases, and that the activity of these enzymes declines at elevated concentrations of inorganic N.In a boreal pine forest and a sub-arctic birch forest, Cortinarius DNA was assessed by 454-sequencing of ITS amplicons and related to Mn-peroxidase activity in humus samples with- and without previous N amendment. Transcription of Cortinarius Mn-peroxidase genes was investigated in field samples. Phylogenetic analyses of Cortinarius peroxidase amplicons and genome sequences were performed.We found a significant co-localization of high peroxidase activity and DNA from Cortinarius species. Peroxidase activity was reduced by high ammonium concentrations. Amplification of mRNA sequences indicated transcription of Cortinarius Mn-peroxidase genes under field conditions. The Cortinarius glaucopus genome encodes 11 peroxidases - a number comparable to many white-rot wood decomposers.These results support the hypothesis that some ectomycorrhizal fungi - Cortinarius species in particular - may play an important role in decomposition of complex organic matter, linked to their mobilization of organically bound N.