Salicylic acid production in response to biotic and abiotic stress depends on isochorismate in Nicotiana benthamiana

Edited by Michael R. Sussman

Received 19 November 2007; received in revised form 9 December 2007; accepted 21 December 2007. published online 15 January 2008.

Abstract

Salicylic acid (SA) is an important signal involved in the activation of defence responses against abiotic and biotic stress. In tobacco, benzoic acid or glucosyl benzoate were proposed to be precursors of SA. This is in sharp contrast with studies in Arabidopsis thaliana, where SA derives from isochorismate. We have determined the importance of isochorismate for SA biosynthesis in Nicotiana benthamiana using virus-induced gene silencing of the isochorismate synthase (ICS) gene. Plants with silenced ICS expression do not accumulate SA after exposure to UV or to pathogen stress. Plants with silenced ICS expression also exhibit strongly decreased levels of phylloquinone, a product of isochorismate. Our data provide evidence for an isochorismate-derived synthesis of SA in N. benthamiana

Keywords: Isochorismate synthase, Pathogen stress, Phylloquinone, Salicylic acid, UV stress, Nicotiana

Department of Biology, University of Fribourg, Ch. du Musée 10, 1700 Fribourg, Switzerland

Corresponding author. Fax: +41 26 300 97 40.

PII: S0014-5793(08)00018-5

doi:10.1016/j.febslet.2007.12.039

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