Functional analysis of RXLR effectors from the New Zealand kauri dieback pathogen Phytophthora agathidicida

Yanan Guo, Pierre Yves Dupont, Carl H. Mesarich, Bo Yang, Rebecca L. McDougal, Preeti Panda, Paul Dijkwel, David J. Studholme, Christine Sambles, Joe Win, Yuanchao Wang, Nari M. Williams, Rosie E. Bradshaw

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New Zealand kauri is an ancient, iconic, gymnosperm tree species that is under threat from a lethal dieback disease caused by the oomycete Phytophthora agathidicida. To gain insight into this pathogen, we determined whether proteinaceous effectors of P. agathidicida interact with the immune system of a model angiosperm, Nicotiana, as previously shown for Phytophthora pathogens of angiosperms. From the P. agathidicida genome, we defined and analysed a set of RXLR effectors, a class of proteins that typically have important roles in suppressing or activating the plant immune system. RXLRs were screened for their ability to activate or suppress the Nicotiana plant immune system using Agrobacterium tumefaciens transient transformation assays. Nine P. agathidicida RXLRs triggered cell death or suppressed plant immunity in Nicotiana, of which three were expressed in kauri. For the most highly expressed, P. agathidicida (Pa) RXLR24, candidate cognate immune receptors associated with cell death were identified in Nicotiana benthamiana using RNA silencing-based approaches. Our results show that RXLRs of a pathogen of gymnosperms can interact with the immune system of an angiosperm species. This study provides an important foundation for studying the molecular basis of plant–pathogen interactions in gymnosperm forest trees, including kauri.

Original languageEnglish
Pages (from-to)1131-1148
Number of pages18
JournalMolecular Plant Pathology
Issue number9
Early online date8 Jul 2020
Publication statusPublished - 1 Sep 2020


  • effectors
  • forest pathogen
  • kauri dieback
  • NBS-LRR immune receptors
  • Phytophthora agathidicida
  • RXLR

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