Koste A. Yadeta,1
Jelle A. Hiemstra,3
Yves Marco,2 and
Bart P. H. J. Thomma1
1Laboratory of Phytopathology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands; 2Laboratoire des Interactions Plantes Microorganismes, Unité Mixte de Recherche, Centre National de la Recherche Scientifique-Institut National de la Recherche Agronomique 2594/441, F-31320 Castanet-Tolosan, France; 3Applied Plant Research, Wageningen University and Research Centre, P.O. Box 85, 2160AB Lisse, The Netherlands; 4Virginia Bioinformatics Institute, Virginia Tech, Blacksburg 24061, U.S.A.
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Accepted 16 August 2011.
Verticillium spp. are destructive soilborne fungal pathogens that cause vascular wilt diseases in a wide range of plant species. Verticillium wilts are particularly notorious, and genetic resistance in crop plants is the most favorable means of disease control. In a gain-of-function screen using an activation-tagged Arabidopsis mutant collection, we identified four mutants, A1 to A4, which displayed enhanced resistance toward the vascular wilt species Verticillium dahliae, V. albo-atrum and V. longisporum but not to Fusarium oxysporum f. sp. raphani. Further testing revealed that mutant A2 displayed enhanced Ralstonia solanacearum resistance, while mutants A1 and A3 were more susceptible toward Pseudomonas syringae pv. tomato. Identification of the activation tag insertion site in the A1 mutant revealed an insertion in close proximity to the gene encoding AHL19, which was constitutively expressed in the mutant. AHL19 knock-out alleles were found to display enhanced Verticillium susceptibility whereas overexpression of AHL19 resulted in enhanced Verticillium resistance, showing that AHL19 acts as a positive regulator of plant defense.
© 2011 The American Phytopathological Society