Guanosine-specific single-stranded ribonuclease effectors of a phytopathogenic fungus potentiate host immune responses
Guanosine-specific single-stranded ribonuclease effectors of a phytopathogenic fungus potentiate host immune responses
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DOI：
10.1101/2021.10.13.464185
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发表时间：
2021-10
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通讯作者：
Naoyoshi Kumakura;Suthitar Singkaravanit-Ogawa;P. Gan;A. Tsushima;N. Ishihama;Shunsuke Watanabe;M. Seo;Shintaro Iwasaki;M. Narusaka;Y. Narusaka;Y. Takano;K. Shirasu
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文献类型：
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作者：
Naoyoshi Kumakura;Suthitar Singkaravanit-Ogawa;P. Gan;A. Tsushima;N. Ishihama;Shunsuke Watanabe;M. Seo;Shintaro Iwasaki;M. Narusaka;Y. Narusaka;Y. Takano;K. Shirasu
植物在识别病原体相关分子模式后激活免疫。虽然植物病原体已经进化出一系列效应蛋白来对抗植物免疫，但一些效应蛋白被宿主感知并诱导免疫应答。在这里，我们表明，两个分泌的核糖核酸酶效应，SRN1和SRN2，编码的植物病原真菌，炭疽菌orbiculare，诱导细胞死亡的信号肽和催化残基依赖的方式，瞬时表达时，在烟草本氏。SRN基因在炭疽菌属物种中的普遍存在表明了保守的作用。利用瞬时基因表达系统在黄瓜（Cucumis sativus）中进行表达。我们发现SRN 1和SRN 2增强宿主模式触发的免疫。与此同时，C。Orbiculare SRN 1和SRN 2缺失突变体对宿主的毒力增强。体外分析显示，SRN1特异性地在鸟苷处切割单链RNA，留下3′端磷酸。在植物中没有报道过这种活性。重要的是，C. SRN 1和SRN 2的反应依赖于信号肽和核糖核酸酶催化残基，表明分泌的SRN在质外体切割RNA并被宿主检测到。我们认为病原体来源的质外体鸟苷特异性单链核糖核酸内切酶导致植物免疫增强。
Plants activate immunity upon recognition of pathogen-associated molecular patterns. Although phytopathogens have evolved a set of effector proteins to counteract plant immunity, some effectors are perceived by hosts and induce immune responses. Here, we show that two secreted ribonuclease effectors, SRN1 and SRN2, encoded in a phytopathogenic fungus, Colletotrichum orbiculare, induce cell death in a signal peptide- and catalytic residue-dependent manner, when transiently expressed in Nicotiana benthamiana. The pervasive presence of SRN genes across Colletotrichum species suggested the conserved roles. Using a transient gene expression system in cucumber (Cucumis sativus), an original host of C. orbiculare, we show that SRN1 and SRN2 potentiate host pattern-triggered immunity. Consistent with this, C. orbiculare SRN1 and SRN2 deletion mutants exhibited increased virulence on the host. In vitro analysis revealed that SRN1 specifically cleaves single-stranded RNAs at guanosine, leaving a 3′-end phosphate. This activity has not been reported in plants. Importantly, the potentiation of C. sativus responses by SRN1 and SRN2 depends on the signal peptide and ribonuclease catalytic residues, suggesting that secreted SRNs cleave RNAs in apoplast and are detected by the host. We propose that the pathogen-derived apoplastic guanosine-specific single-stranded endoribonucleases lead to immunity potentiation in plants.