Long-distance communication and signal amplification in systemic acquired resistance
- 1Department of Biological Sciences, University of North Texas, Denton, TX, USA
- 2Department of Biology, Heinrich-Heine-University, Düsseldorf, Germany
Systemic acquired resistance (SAR) is an inducible defense mechanism in plants that confers enhanced resistance against a variety of pathogens. SAR is activated in the uninfected systemic (distal) organs in response to a prior (primary) infection elsewhere in the plant. SAR is associated with the activation of salicylic acid (SA) signaling and the priming of defense responses for robust activation in response to subsequent infections. The activation of SAR requires communication by the primary infected tissues with the distal organs. The vasculature functions as a conduit for the translocation of factors that facilitate long-distance intra-plant communication. In recent years, several metabolites putatively involved in long-distance signaling have been identified. These include the methyl ester of SA (MeSA), the abietane diterpenoid dehydroabietinal (DA), the dicarboxylic acid azelaic acid (AzA), and a glycerol-3-phosphate (G3P)-dependent factor. Long-distance signaling by some of these metabolites also requires the lipid-transfer protein DIR1 (DEFECTIVE IN INDUCED RESISTANCE 1). The relative contribution of these factors in long-distance signaling is likely influenced by environmental conditions, for example light. In the systemic leaves, the AGD2-LIKE DEFENSE RESPONSE PROTEIN1 (ALD1)-dependent production of the lysine catabolite pipecolic acid (Pip), FLAVIN-DEPENDENT MONOOXYGENASE1 (FMO1) signaling, as well as SA synthesis and downstream signaling are required for the activation of SAR. This review summarizes the involvement and interaction between long-distance SAR signals and details the recently discovered role of Pip in defense amplification and priming that allows plants to acquire immunity at the systemic level. Recent advances in SA signaling and perception are also highlighted.
Keywords: azelaic acid, dehydroabietinal, glycerol-3-phosphate, methyl salicylate, pipecolic acid, DIR1
Citation: Shah J and Zeier J (2013) Long-distance communication and signal amplification in systemic acquired resistance. Front. Plant Sci. 4:30. doi: 10.3389/fpls.2013.00030
Received: 20 December 2012; Paper pending published: 28 January 2013;
Accepted: 06 February 2013; Published online: 22 February 2013.
Edited by:Saskia C. M. Van Wees, Utrecht University, Netherlands
Reviewed by:Keiko Yoshioka, University of Toronto, Canada
Robin K. Cameron, McMaster University, Canada
Copyright © 2013 Shah and Zeier. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in other forums, provided the original authors and source are credited and subject to any copyright notices concerning any third-party graphics etc.
*Correspondence: Jyoti Shah, Department of Biological Sciences, University of North Texas, Life Sciences Building-B, Room # 418, 1155 Union Circle #305220, Denton, TX 76203, USA. e-mail: email@example.com
Jürgen Zeier, Department of Biology, Heinrich-Heine-University, 40225 Düsseldorf, Germany. e-mail: firstname.lastname@example.org