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Necrotrophic Pathogens Use the Salicylic Acid Signaling Pathway to Promote Disease Development in Tomato

December 2012 , Volume 25 , Number  12
Pages  1,584 - 1,593

Taha Abd El Rahman, Mohamed El Oirdi, Rocio Gonzalez-Lamothe, and Kamal Bouarab

Centre de Recherche en Amélioration Végétale, Département de Biologie, Faculté des Sciences, Université de Sherbrooke, 2500 Boulevard de l'Université, Sherbrooke, Québec, J1K2R1, Canada

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Accepted 29 August 2012.

Plants use different immune pathways to combat pathogens. The activation of the jasmonic acid (JA)-signaling pathway is required for resistance against necrotrophic pathogens; however, to combat biotrophic pathogens, the plants activate mainly the salicylic acid (SA)-signaling pathway. SA can antagonize JA signaling and vice versa. NPR1 (noninducible pathogenesis-related 1) is considered a master regulator of SA signaling. NPR1 interacts with TGA transcription factors, ultimately leading to the activation of SA-dependent responses. SA has been shown to promote disease development caused by the necrotrophic pathogen Botrytis cinerea through NPR1, by suppressing the expression of two JA-dependent defense genes, proteinase inhibitors I and II. We show here that the transcription factor TGA1.a contributes to disease development caused by B. cinerea in tomato by suppressing the expression of proteinase inhibitors I and II. Finally, we present evidence that the SA-signaling pathway contributes to disease development caused by another necrotrophic pathogen, Alternaria solani, in tomato. Disease development promoted by SA through NPR1 requires the TGA1.a transcription factor. These data highlight how necrotrophs manipulate the SA-signaling pathway to promote their disease in tomato.

© 2012 The American Phytopathological Society