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<p>Grape downy mildew, caused by the pathogen <i>Plasmopara viticola</i>, is a devastating oomycete disease. RxLR effectors are secreted by oomycetes. In this study, we investigated an RxLR effector, <i>PvRxLR31197</i>, which was isolated from the <i>P. viticola</i> transcriptome. <i>PvRxLR31197</i> features a typical RxLR motif ‘RSLR’ following the ‘DESR’, ‘W’, and ‘Y’ motifs in the N-terminus. <i>PvRxLR31197</i> was identified as a secretory protein via a signal sequence trap (SST) assay and is orthologous to the avirulence gene <i>PiAvr4</i> from <i>Phytophthora infestans</i>. <i>PvRxLR31197</i> is upregulated during <i>P. viticola</i> infection and is localized in the nucleus, cytoplasm, and endoplasmic reticulum. Functional assays demonstrated that <i>PvRxLR31197</i> effectively suppresses pathogen colonization in both <i>N. benthamiana</i> and grapevine. Moreover, <i>PvRxLR31197</i> triggers plant immunity independent of its nuclear localization. This effector <i>PvRxLR31197</i> potentially induces pattern-triggered immunity (PTI), as evidenced by the elevated expression of PTI marker genes (<i>NbWRKY7</i> and <i>NbWRKY8</i>) in <i>PvRxLR31197</i>-overexpressing <i>N. benthamiana</i>. Further investigation revealed that the expression of marker genes related to the salicylic acid (SA) signaling pathway decreased, whereas those associated with the ethylene (ET) and jasmonic acid (JA) signaling pathways significantly increased in <i>PvRxLR31197</i>-overexpressing <i>N. benthamiana</i>, suggesting that <i>PvRxLR31197</i>-triggered PTI may not depend on the SA-mediated pathway but rather involves the ET/JA-mediated signaling pathways. Moreover, yeast two-hybrid screening identified vesicle-associated protein 1.1 (VAP1.1) as a host target of <i>PvRxLR31197</i>. Subsequent BiFC and colocalization analyses further confirmed their interaction in the endoplasmic reticulum. These findings elucidate <i>PvRxLR31197</i>’s role in <i>P. viticola</i>-plant interactions and its immune induction mechanism.</p>

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An RxLR effector from Plasmopara viticola induces immunity responses in grapevine and Nicotiana benthamiana

  • 期刊论文

  • 发表日期：

    2025年12月15日

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  • Siyu Li,
  • Ruonan Li,
  • Shuang Chen,
  • Zihan Shi,
  • Bianbian Wang,
  • Haoke Wang,
  • Wenjing Xue,
  • Xin Feng,
  • Zhengzhe Li,
  • Fangfang Wang,
  • Ruiqi Liu,
  • Zaozhu Niu,
  • Yan Xu,
  • Guotian Liu

摘要

Grape downy mildew, caused by the pathogen Plasmopara viticola, is a devastating oomycete disease. RxLR effectors are secreted by oomycetes. In this study, we investigated an RxLR effector, PvRxLR31197, which was isolated from the P. viticola transcriptome. PvRxLR31197 features a typical RxLR motif ‘RSLR’ following the ‘DESR’, ‘W’, and ‘Y’ motifs in the N-terminus. PvRxLR31197 was identified as a secretory protein via a signal sequence trap (SST) assay and is orthologous to the avirulence gene PiAvr4 from Phytophthora infestans. PvRxLR31197 is upregulated during P. viticola infection and is localized in the nucleus, cytoplasm, and endoplasmic reticulum. Functional assays demonstrated that PvRxLR31197 effectively suppresses pathogen colonization in both N. benthamiana and grapevine. Moreover, PvRxLR31197 triggers plant immunity independent of its nuclear localization. This effector PvRxLR31197 potentially induces pattern-triggered immunity (PTI), as evidenced by the elevated expression of PTI marker genes (NbWRKY7 and NbWRKY8) in PvRxLR31197-overexpressing N. benthamiana. Further investigation revealed that the expression of marker genes related to the salicylic acid (SA) signaling pathway decreased, whereas those associated with the ethylene (ET) and jasmonic acid (JA) signaling pathways significantly increased in PvRxLR31197-overexpressing N. benthamiana, suggesting that PvRxLR31197-triggered PTI may not depend on the SA-mediated pathway but rather involves the ET/JA-mediated signaling pathways. Moreover, yeast two-hybrid screening identified vesicle-associated protein 1.1 (VAP1.1) as a host target of PvRxLR31197. Subsequent BiFC and colocalization analyses further confirmed their interaction in the endoplasmic reticulum. These findings elucidate PvRxLR31197’s role in P. viticola-plant interactions and its immune induction mechanism.