Liu Mengxia, Jaber Emad, Zeng Zhen, Kovalchuk Andriy, Asiegbu Fred O
Department of Forest Sciences, Faculty of Agriculture and Forestry, University of Helsinki, PO Box 27, FIN-00014, Helsinki, Finland.
Tree Physiol. 2021 May 14;41(5):791-800. doi: 10.1093/treephys/tpaa141.
In the forest of Northern Hemisphere, the fungi Heterobasidion annosum (Fr.) Bref. s.l. causes severe root and stem rot diseases, dramatically reducing the wood quality of conifer trees. The hallmark of the host response during the infection process is the formation of necrotic lesions and reaction zones. To characterize physiochemical and molecular features of the necrotic lesion, we conducted artificial inoculations on Norway spruce plants at different developmental stages: seedlings, young and mature trees. The results were further compared against data available on the formation of reaction zones. Strong necrosis browning or enlarged necrotic lesions were observed in infected tissues. This was accompanied by elevated pH. However, the increased pH, around 6.0 in necrotic lesions, was not as high as that documented in reaction zones, above 7.0 as marked by the intensity of the blue colour in response to 2,6-dichlorophenol indophenol dye. Peroxidase activity increased in infected plants and RNA-seq analysis of necrotic lesions showed marked upregulation of defence-related genes. Our findings highlight similarities and differences between the reaction zone and necrotic lesion formation in response of conifer trees to biotic stress.
在北半球的森林中，异担子菌（Heterobasidion annosum (Fr.) Bref. s.l.）会引发严重的根腐和茎腐病，显著降低针叶树的木材质量。感染过程中宿主反应的标志是坏死病斑和反应区的形成。为了表征坏死病斑的物理化学和分子特征，我们对处于不同发育阶段的挪威云杉植株进行了人工接种：幼苗、幼树和成熟树木。研究结果进一步与反应区形成的现有数据进行了比较。在受感染组织中观察到强烈的坏死褐变或扩大的坏死病斑。这伴随着pH值的升高。然而，坏死病斑中的pH值升高至约6.0，并不像反应区中记录的那么高，反应区中pH值高于7.0，以2,6 - 二氯酚靛酚染料反应产生的蓝色强度为标志。感染植株中的过氧化物酶活性增加，对坏死病斑的RNA测序分析显示防御相关基因显著上调。我们的研究结果突出了针叶树对生物胁迫反应中反应区和坏死病斑形成之间的异同。
