Bödeker Inga T M, Clemmensen Karina E, de Boer Wietse, Martin Francis, Olson Åke, Lindahl Björn D
Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, Box 7026, 75007, Uppsala, Sweden; Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences, Box 49, 230 53, Alnarp, Sweden.
New Phytol. 2014 Jul;203(1):245-56. doi: 10.1111/nph.12791. Epub 2014 Apr 14.
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.
在北方森林中，复杂有机库中氮（N）的地下固存限制了植物对养分的获取。外生菌根真菌产生的氧化细胞外酶可能通过提供对大分子复合物中氮的获取途径来帮助植物获取氮。我们检验了以下假设：外生菌根丝膜菌属物种产生依赖锰的过氧化物酶，并且这些酶的活性在无机氮浓度升高时会下降。在北方松树林和亚北极桦树林中，通过对ITS扩增子进行454测序来评估丝膜菌属的DNA，并将其与经过和未经过先前氮添加处理的腐殖质样品中的锰过氧化物酶活性相关联。在野外样品中研究了丝膜菌属锰过氧化物酶基因的转录情况。对丝膜菌属过氧化物酶扩增子和基因组序列进行了系统发育分析。我们发现过氧化物酶高活性与丝膜菌属物种的DNA存在显著的共定位。高铵浓度会降低过氧化物酶活性。mRNA序列的扩增表明在野外条件下丝膜菌属锰过氧化物酶基因的转录。灰丝膜菌的基因组编码11种过氧化物酶，这一数量与许多白腐木材分解菌相当。这些结果支持了以下假设：一些外生菌根真菌，特别是丝膜菌属物种，可能在复杂有机物的分解中发挥重要作用，这与其对有机结合氮的动员有关。
