Gallinger Jannicke, Zikeli Kerstin, Zimmermann Matthias R, Görg Louisa M, Mithöfer Axel, Reichelt Michael, Seemüller Erich, Gross Jürgen, Furch Alexandra C U
Institute for Plant Protection in Fruit Crops and Viticulture, Julius Kühn-Institut, Federal Research Institute for Cultivated Plants, Dossenheim, Germany.
Plant Physiology, Matthias-Schleiden-Institute for Genetics, Bioinformatics and Molecular Botany, Faculty of Biological Science, Friedrich-Schiller-University Jena, Jena, Germany.
PLoS Pathog. 2021 Mar 25;17(3):e1009459. doi: 10.1371/journal.ppat.1009459. eCollection 2021 Mar.
The host-pathogen combinations-Malus domestica (apple)/Candidatus Phytoplasma mali´, Prunus persica (peach)/Ca. P. prunorum´ and Pyrus communis (pear)/`Ca. P. pyri´ show different courses of diseases although the phytoplasma strains belong to the same 16SrX group. While infected apple trees can survive for decades, peach and pear trees die within weeks to few years. To this date, neither morphological nor physiological differences caused by phytoplasmas have been studied in these host plants. In this study, phytoplasma-induced morphological changes of the vascular system as well as physiological changes of the phloem sap and leaf phytohormones were analysed and compared with non-infected plants. Unlike peach and pear, infected apple trees showed substantial reductions in leaf and vascular area, affecting phloem mass flow. In contrast, in infected pear mass flow and physicochemical characteristics of phloem sap increased. Additionally, an increased callose deposition was detected in pear and peach leaves but not in apple trees in response to phytoplasma infection. The phytohormone levels in pear were not affected by an infection, while in apple and peach trees concentrations of defence- and stress-related phytohormones were increased. Compared with peach and pear trees, data from apple suggest that the long-lasting morphological adaptations in the vascular system, which likely cause reduced sap flow, triggers the ability of apple trees to survive phytoplasma infection. Some phytohormone-mediated defences might support the tolerance.
宿主-病原体组合——苹果（Malus domestica）/‘苹果植原体（Candidatus Phytoplasma mali）’、桃（Prunus persica）/‘李属植原体（Ca. P. prunorum）’和梨（Pyrus communis）/‘梨植原体（Ca. P. pyri）’，尽管植原体菌株属于同一16SrX组，但呈现出不同的病程。受感染的苹果树可以存活数十年，而桃树和梨树在数周内至数年内死亡。迄今为止，尚未对这些宿主植物中由植原体引起的形态学和生理学差异进行研究。在本研究中，分析了植原体诱导的维管系统形态变化以及韧皮部汁液和叶片植物激素的生理变化，并与未感染的植物进行了比较。与桃树和梨树不同，受感染的苹果树叶片和维管面积大幅减少，影响了韧皮部的物质运输。相比之下，受感染梨树的物质运输和韧皮部汁液的物理化学特性增加。此外，在梨和桃树叶中检测到胼胝质沉积增加，但在受植原体感染的苹果树中未检测到。梨中的植物激素水平不受感染影响，而在苹果树和桃树中，与防御和胁迫相关的植物激素浓度增加。与桃树和梨树相比，来自苹果的数据表明，维管系统中持久的形态适应可能导致汁液流动减少，从而触发了苹果树在植原体感染下存活的能力。一些植物激素介导的防御可能支持这种耐受性。
