Life at the edge - the cytology and physiology of the biotroph to necrotroph transition in Hymenoscyphus fraxineus during lesion formation in ash
Life at the edge - the cytology and physiology of the biotroph to necrotroph transition in Hymenoscyphus fraxineus during lesion formation in ash
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DOI：
10.1111/ppa.13014
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发表时间：
2019-06-01
期刊：
影响因子：
2.7
通讯作者：
Papp-Rupar, M.
中科院分区：
文献类型：
--
作者：
Mansfield, J.;Brown, I.;Papp-Rupar, M.
用光学显微镜和电子显微镜观察了白蜡膜囊菌子囊孢子接种体在白蜡茎上的定殖过程。该研究的主要目的是表征病变形成过程中的活体营养型向坏死营养型转变的细胞学特征。在直接穿透表皮细胞后，真菌产生细胞内菌丝，在植物细胞死亡前侵入多达5个细胞。菌丝细胞壁与植物细胞膜之间缺乏紧密的附着。在感染中心的植物细胞死亡，但在边缘的菌丝通常在活的植物细胞中发现，甚至在大的病变周围。在活体营养型入侵过程中，尽管植物细胞膜与真菌细胞壁直接接触，但穿透的植物细胞的细胞质几乎没有反应。在植物细胞死亡前，细胞质染色加深，小泡增生，但细胞器保持正常的超微结构。死亡的植物细胞含有深褐色的嗜锇小滴。表皮或厚角组织细胞之间的渗透通常是针对共享的凹坑，并涉及菌丝的收缩。向坏死型的转变与菌丝形态的明显变化无关。活体营养的胞内菌丝含有致密的细胞质，而死细胞中的菌丝则更多地空泡化。尽管真菌穿透多达18个细胞深入茎组织，但观察到的植物细胞壁降解非常少。灰枯梢病真菌的发展特点进行了比较与其他半自养病原体。
The progress of colonization of ash stems from ascospore inocula of Hymenoscyphus fraxineus was examined by light and electron microscopy. The main aim of the study was to characterize the cytology of the biotroph to necrotroph transition during lesion formation. Following direct penetration into epidermal cells, the fungus produced intracellular hyphae that invaded up to five cells before plant cells died. A lack of close attachment between the hyphal cell wall and plant cell membrane was revealed by plasmolysis of epidermal cells. Plant cells died at the centre of the infection but hyphae at the edge were typically found in living plant cells even around large lesions. During biotrophic invasion, the cytoplasm of penetrated plant cells showed very little response despite the plant cell membrane being in direct contact with the fungal cell wall. Before plant cell death, dark staining of the cytoplasm and proliferation of small vesicles was noted, but organelles retained normal ultrastructure. Dead plant cells contained dark brown, osmiophilic droplets. Penetration between epidermal or collenchyma cells was usually targeted to shared pits and involved constriction of hyphae. The transition to necrotrophy was not associated with a clear change in hyphal morphology. Biotrophic intracellular hyphae contained dense cytoplasm but hyphae in dead plant cells were more vacuolated. Remarkably little plant cell wall degradation was observed despite the fungus penetrating up to 18 cells deep into stem tissue. Features of the development of the ash dieback fungus are compared with other hemibiotrophic pathogens.