ORIGINAL ARTICLE Vitis vinifera VvNPR1.1 is the functional ortholog of AtNPR1 and its overexpression in grapevine triggers constitutive activation of PR genes and enhanced resistance to powdery mildew Gae ¨lle Le Henanff • Sibylle Farine • Flore Kieffer-Mazet • Anne-Sophie Miclot • Thierry Heitz • Pere Mestre • Christophe Bertsch • Julie Chong Received: 16 February 2011 / Accepted: 31 March 2011 / Published online: 20 April 2011 Ó Springer-Verlag 2011 Abstract Studying grapevine (Vitis vinifera) innate defense mechanisms is a prerequisite to the development of new protection strategies, based on the stimulation of plant signaling pathways to trigger pathogen resistance. Two transcriptional coactivators (VvNPR1.1 and VvNPR1.2) with similarity to Arabidopsis thaliana NPR1 (Non- Expressor of PR genes 1), a well-characterized and key signaling element of the salicylic acid (SA) pathway, were recently isolated in Vitis vinifera. In this study, functional characterization of VvNPR1.1 and VvNPR1.2, including complementation of the Arabidopsis npr1 mutant, revealed that VvNPR1.1 is a functional ortholog of AtNPR1, whereas VvNPR1.2 likely has a different function. Ectopic overexpression of VvNPR1.1 in the Arabidopsis npr1-2 mutant restored plant growth at a high SA concentration, Pathogenesis Related 1 (PR1) gene expression after treat- ment with SA or bacterial inoculation, and resistance to virulent Pseudomonas syringae pv. maculicola bacteria. Moreover, stable overexpression of VvNPR1.1-GFP in V. vinifera resulted in constitutive nuclear localization of the fusion protein and enhanced PR gene expression in unin- fected plants. Furthermore, grapevine plants overexpressing VvNPR1.1-GFP exhibited an enhanced resistance to pow- dery mildew infection. This work highlights the importance of the conserved SA/NPR1 signaling pathway for resistance to biotrophic pathogens in V. vinifera. Keywords Vitis vinifera Á Arabidopsis thaliana Á Defense response signaling Á Salicylic acid Á Disease resistance Abbreviations BTH Benzothiadiazole EDS1 Enhanced disease susceptibility ET Ethylene INA 2.6-dichloroisonicotinic acid JA Jasmonic acid MeJA Methyljasmonate NPR1 Non-expressor of PR genes 1 PR Pathogenesis related SA Salicylic acid SAR Systemic acquired resistance Introduction Grapes are a major fruit crop but grapevine is generally susceptible to attack by diverse pathogens including G. Le Henanff Á S. Farine Á F. Kieffer-Mazet Á C. Bertsch Á J. Chong (&) Universite ´ de Haute Alsace, Laboratoire Vigne, Biotechnologies et Environnement (EA3991), 33 rue de Herrlisheim, 68000 Colmar, France e-mail: julie.chong@uha.fr A.-S. Miclot Á P. Mestre INRA, UMR1131 Sante ´ de la Vigne et Qualite ´ du Vin, 68000 Colmar, France A.-S. Miclot Á P. Mestre Universite ´ de Strasbourg, UMR 1131 Sante ´ de la Vigne et Qualite ´ du Vin, 68000 Colmar, France Present Address: A.-S. Miclot UMR Ge ´ne ´tique et Horticulture (GenHort), IFR149 QUASAV, Centre INRA Angers-Nantes, BP 60057, 49071 Beaucouze ´, France T. Heitz IBMP du CNRS (UPR2357), De ´partement Re ´seaux Me ´taboliques chez les Ve ´ge ´taux, 12 rue du ge ´ne ´ral Zimmer, 67000 Strasbourg, France 123 Planta (2011) 234:405–417 DOI 10.1007/s00425-011-1412-1