Department of Plant Pathology, MOA Key Lab of Pest Monitoring and Green Management, College of Plant Protection, China Agricultural University, Beijing, China.
State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing, China.
J Exp Bot. 2022 Apr 5;73(7):2125-2141. doi: 10.1093/jxb/erab530.
Oxysterol-binding protein-related proteins (ORPs) are a conserved class of lipid transfer proteins that are closely involved in multiple cellular processes in eukaryotes, but their roles in plant-pathogen interactions are mostly unknown. We show that transient expression of ORPs of Magnaporthe oryzae (MoORPs) in Nicotiana benthamina plants triggered oxidative bursts and cell death; treatment of tobacco Bright Yellow-2 suspension cells with recombinant MoORPs elicited the production of reactive oxygen species. Despite ORPs being normally described as intracellular proteins, we detected MoORPs in fungal culture filtrates and intercellular fluids from barley plants infected with the fungus. More importantly, infiltration of Arabidopsis plants with recombinant Arabidopsis or fungal ORPs activated oxidative bursts, callose deposition, and PR1 gene expression, and enhanced plant disease resistance, implying that ORPs may function as endogenous and exogenous danger signals triggering plant innate immunity. Extracellular application of fungal ORPs exerted an opposite impact on salicylic acid and jasmonic acid/ethylene signaling pathways. Brassinosteroid Insensitive 1-associated Kinase 1 was dispensable for the ORP-activated defense. Besides, simultaneous knockout of MoORP1 and MoORP3 abolished fungal colony radial growth and conidiation, whereas double knockout of MoORP1 and MoORP2 compromised fungal virulence on barley and rice plants. These observations collectively highlight the multifaceted role of MoORPs in the modulation of plant innate immunity and promotion of fungal development and virulence in M. oryzae.
氧化固醇结合蛋白相关蛋白（ORPs）是一类保守的脂质转运蛋白，它们在真核生物的多种细胞过程中密切相关，但它们在植物-病原体相互作用中的作用大多未知。我们表明，稻瘟病菌（Magnaporthe oryzae）的 ORP 瞬时表达在本氏烟植物中引发了氧化爆发和细胞死亡；用重组 MoORPs 处理烟草 Bright Yellow-2 悬浮细胞会引发活性氧的产生。尽管 ORPs 通常被描述为细胞内蛋白，但我们在真菌培养液滤液和感染真菌的大麦植物细胞间液中检测到了 MoORPs。更重要的是，用重组拟南芥或真菌 ORP 浸润拟南芥植物会引发氧化爆发、胼胝质沉积和 PR1 基因表达，并增强植物的抗病性，这意味着 ORP 可能作为内源性和外源性危险信号触发植物先天免疫。真菌 ORP 的细胞外应用对水杨酸和茉莉酸/乙烯信号通路产生了相反的影响。油菜素内酯不敏感 1 相关激酶 1 对于 ORP 激活的防御是可有可无的。此外，MoORP1 和 MoORP3 的同时敲除消除了真菌菌落的径向生长和分生孢子形成，而 MoORP1 和 MoORP2 的双重敲除削弱了真菌对大麦和水稻植物的毒力。这些观察结果共同强调了 MoORPs 在调节植物先天免疫以及促进稻瘟病菌发育和毒力方面的多方面作用。
