Steiner Ulrike, Oerke Erich-Christian
Institute of Crop Science and Resource Conservation-Plant Pathology, Rheinische Friedrich-Wilhelms-Universitaet Bonn, 53115 Bonn, Germany.
J Fungi (Basel). 2024 Nov 29;10(12):831. doi: 10.3390/jof10120831.
Microscopic evidence demonstrated a strictly biotrophic lifestyle of the scab fungus on growing apple leaves and characterised its hemibiotrophy as the combination of biotrophy and saprotrophy not described before. The pathogen-host interface was characterised by the formation of knob-like structures of the fungal stroma appressed to epidermal cells as early as 1 day after host penetration, very thin fan-shaped cells covering large parts of the host cell lumen, and enzymatic cuticle penetration from the subcuticular space limited to the protruding conidiophores. The cell wall had numerous orifices, facilitating intimate contact with the host tissue. Pathogen-induced modifications of host cells included partial degradation of the cell wall, transition of epidermal cells into transfer cells, modification of epidermal pit fields to manipulate the flow of nutrients and other compounds, and formation of globular protuberances of mesophyll cells without contact with the pathogen. The non-haustorial biotrophy was characterised by enlarged areas of intimate contact with host cells, often mediated by a matrix between the pathogen and plant structures. The new microscopic evidence and information on the pathogens' biochemistry and secretome from the literature gave rise to a model of the lifestyle of , lacking a necrotrophic stage that covers and explains its holomorphic development.
微观证据表明，痂病菌在生长中的苹果叶片上具有严格的活体营养型生活方式，并将其半活体营养型特征描述为前所未有的活体营养型和腐生营养型的结合。病原体与宿主的界面特征如下：早在宿主被侵染1天后，真菌基质就形成了紧贴表皮细胞的瘤状结构；非常薄的扇形细胞覆盖了宿主细胞腔的大部分区域；酶促角质层穿透仅限于突出的分生孢子梗的皮下空间。细胞壁有许多小孔，便于与宿主组织紧密接触。病原体诱导的宿主细胞变化包括细胞壁部分降解、表皮细胞转变为传递细胞、表皮纹孔场改变以控制营养物质和其他化合物的流动，以及叶肉细胞形成球状突起且不与病原体接触。非吸器活体营养型的特征是与宿主细胞紧密接触的面积增大，这通常由病原体与植物结构之间的基质介导。新的微观证据以及文献中关于病原体生物化学和分泌组的信息，产生了一个关于该病菌生活方式的模型，该模型没有坏死营养阶段，涵盖并解释了其全型发育过程。
