title: Free radicals mediate systemic acquired resistance.
abstract: Systemic acquired resistance (SAR) is a form of resistance that protects plants against a broad spectrum of secondary infections. However, exploiting SAR for the protection of agriculturally important plants warrants a thorough investigation of the mutual interrelationships among the various signals that mediate SAR. Here, we show that nitric oxide (NO) and reactive oxygen species (ROS) serve as inducers of SAR in a concentration-dependent manner. Thus, genetic mutations that either inhibit NO/ROS production or increase NO accumulation (e.g., a mutation in S-nitrosoglutathione reductase [GSNOR]) abrogate SAR. Different ROS function additively to generate the fatty-acid-derived azelaic acid (AzA), which in turn induces production of the SAR inducer glycerol-3-phosphate (G3P). Notably, this NO/ROS→AzA→G3P-induced signaling functions in parallel with salicylic acid-derived signaling. We propose that the parallel operation of NO/ROS and SA pathways facilitates coordinated regulation in order to ensure optimal induction of SAR.
authors.affiliation: College of Agronomy and Plant Protection, Qingdao Agricultural University, Qingdao 266109, P.R. China; Department of Plant Pathology, University of Kentucky, Lexington, KY 40546, USA.
authors.forename: Caixia
authors.initials: C
authors.lastname: Wang
authors.affiliation: Department of Plant Pathology, University of Kentucky, Lexington, KY 40546, USA.
authors.forename: Mohamed
authors.initials: M
authors.lastname: El-Shetehy
authors.affiliation: Department of Plant Pathology, University of Kentucky, Lexington, KY 40546, USA.
authors.forename: M B
authors.initials: MB
authors.lastname: Shine
authors.affiliation: Department of Plant Pathology, University of Kentucky, Lexington, KY 40546, USA.
authors.forename: Keshun
authors.initials: K
authors.lastname: Yu
authors.affiliation: U.S. Department of Agriculture - Agricultural Research Service, Washington State University, Prosser, WA 99350, USA.
authors.forename: Duroy
authors.initials: D
authors.lastname: Navarre
authors.affiliation: Université de Bourgogne, ERL CNRS 6300, UMR 1347 Agroécologie, BP 86510, 21065 Dijon, France.
authors.forename: David
authors.initials: D
authors.lastname: Wendehenne
authors.affiliation: Department of Plant Pathology, University of Kentucky, Lexington, KY 40546, USA.
authors.forename: Aardra
authors.initials: A
authors.lastname: Kachroo
authors.affiliation: Department of Plant Pathology, University of Kentucky, Lexington, KY 40546, USA. Electronic address: pk62@uky.edu.
authors.forename: Pradeep
authors.initials: P
authors.lastname: Kachroo
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D003998:Dicarboxylic Acids / Q000378:metabolism; D005980:Glutathione Reductase / Q000235:genetics / Q000378:metabolism; D005994:Glycerophosphates / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism; D057865:Plant Immunity; D044224:Pseudomonas syringae / Q000472:pathogenicity; D017382:Reactive Oxygen Species / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D003998:Dicarboxylic Acids; D005994:Glycerophosphates; D017382:Reactive Oxygen Species; D009569:Nitric Oxide; C029620:alpha-glycerophosphoric acid; C521947:NOA1 protein, Arabidopsis; D019001:Nitric Oxide Synthase; D005980:Glutathione Reductase; C521253:S-nitrosoglutathione reductase, Arabidopsis; C010038:azelaic acid