Molecular Microbiology (2004) 54, 533-545

Nienke Westerink, Bas F. Brandwagt, Pierre J.G.M. de Wit and Matthieu H.A.J. Joosten (2004)
Cladosporium fulvum circumvents the second functional resistance gene homologue at the Cf-4 locus (Hcr9-4E ) by secretion of a stable avr4E isoform
Molecular Microbiology 54 (2), 533-545
Abstract: Introgression of resistance trait Cf-4 from wild tomato species into tomato cultivar MoneyMaker (MM-Cf0) has resulted in the near-isogenic line MM-Cf4 that confers resistance to the fungal tomato pathogen Cladosporium fulvum. At the Cf-4 locus, five homologues of Cladosporium resistance gene Cf-9 (Hcr9s) are present. While Hcr9-4D represents the functional Cf-4 resistance gene matching Avr4, Hcr9-4E confers resistance towards C. fulvum by mediating recognition of the novel avirulence determinant Avr4E. Here, we report the isolation of the Avr4E gene, which encodes a cysteine-rich protein of 101 amino acids that is secreted by C. fulvum during colonization of the apoplastic space of tomato leaves. By complementation we show that Avr4E confers avirulence to strains of C. fulvum that are normally virulent on Hcr9-4E-transgenic plants, indicating that Avr4E is a genuine, race-specific avirulence determinant. Strains of C. fulvum evade Hcr9-4E-mediated resistance either by a deletion of the Avr4E gene or by production of a stable Avr4E mutant protein that carries two amino acid substitutions, Phe⁸²Leu and Met⁹³Thr. Moreover, we demonstrate by site-directed mutagenesis that the single amino acid substitution Phe⁸²Leu in Avr4E is sufficient to evade Hcr9-4E-mediated resistance.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Matthieu H. A. J. Joosten

Research topic(s) for pests/diseases/weeds:
resistance/tolerance/defence of host
molecular biology - genes

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Fulvia fulva	Tomato (Solanum lycopersicum)