Recognition of Phytophthora infestans Avr4 by potato R4 is triggered by C-terminal domains comprising W motifs

Authors

  • PIETER M. J. A. VAN POPPEL,

    1. Laboratory of Phytopathology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
    2. Centre for BioSystems Genomics (CBSG), P.O. Box 98, 6700 AB Wageningen, The Netherlands
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    • Present address: De Ruiter Seeds R&D NL B.V., PO Box 1050, 2660 BB Bergschenhoek, The Netherlands.

  • RAYS H. Y. JIANG,

    1. Laboratory of Phytopathology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
    2. Centre for BioSystems Genomics (CBSG), P.O. Box 98, 6700 AB Wageningen, The Netherlands
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    • Present address: Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA.

  • JADWIGA ŚLIWKA,

    1. Laboratory of Phytopathology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
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    • §

      Permanent address: Research Centre Młochów, Plant Breeding and Acclimatization Institute, Platanowa 19, 05-831 Mlochow, Poland.

  • FRANCINE GOVERS

    Corresponding author
    1. Laboratory of Phytopathology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
    2. Centre for BioSystems Genomics (CBSG), P.O. Box 98, 6700 AB Wageningen, The Netherlands
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*E-mail: Francine.Govers@wur.nl

SUMMARY

Oomycete RXLR-dEER effector proteins are rapidly evolving proteins with the selective pressure targeted predominantly at their C-terminal ends. The majority of RXLR-dEER proteins have recognizable motifs of 21–30 amino acids in the C-terminal domain that are named after conserved amino acid residues at fixed positions within the respective motifs. In this article, it is reported that the Phytophthora infestans RXLR-dEER protein Avr4 contains three W motifs and one Y motif in its C-terminal domain. Agroinfection assays using constructs encoding modified forms of PiAvr4 have shown that the region containing the W2 motif, in combination with either the W1 or W3 motif, triggers a necrotic response in potato plants carrying the resistance gene R4. By mining the superfamily of avirulence homologues (Avh) deduced from three sequenced Phytophthora genomes, several Avh proteins were identified as homologues of PiAvr4: six in P. infestans, one in P. ramorum and seven in P. sojae. One very close homologue of PiAvr4 was cloned from the sibling species, P. mirabilis. This species is not pathogenic on potato but, similar to PiAvr4, PmirAvh4 triggered a necrotic response on potato clones carrying R4, but not on clones lacking R4. Genes encoding RXLR-dEER effectors are often located in regions showing genome rearrangements. Alignment of the genomic region harbouring PiAvr4 with syntenic regions in P. sojae and P. ramorum revealed that PiAvr4 is located on a 100-kb indel block and is surrounded by transposable elements.

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