title: Nitric oxide-mediated maintenance of redox homeostasis contributes to NPR1-dependent plant innate immunity triggered by lipopolysaccharides.
abstract: The perception of lipopolysaccharides (LPS) by plant cells can lead to nitric oxide (NO) production and defense gene induction. However, the signaling cascades underlying these cellular responses have not yet been resolved. This work investigated the biosynthetic origin of NO and the role of NONEXPRESSOR OF PATHOGENESIS-RELATED GENES1 (NPR1) to gain insight into the mechanism involved in LPS-induced resistance of Arabidopsis (Arabidopsis thaliana). Analysis of inhibitors and mutants showed that LPS-induced NO synthesis was mainly mediated by an arginine-utilizing source of NO generation. Furthermore, LPS-induced NO caused transcript accumulation of alternative oxidase genes and increased antioxidant enzyme activity, which enhanced antioxidant capacity and modulated redox state. We also analyzed the subcellular localization of NPR1 to identify the mechanism for protein-modulated plant innate immunity triggered by LPS. LPS-activated defense responses, including callose deposition and defense-related gene expression, were found to be regulated through an NPR1-dependent pathway. In summary, a significant NO synthesis induced by LPS contributes to the LPS-induced defense responses by up-regulation of defense genes and modulation of cellular redox state. Moreover, NPR1 plays an important role in LPS-triggered plant innate immunity.
authors.affiliation: Ministry of Education Key Laboratory of Laser Life Science and Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China.
authors.forename: Aizhen
authors.initials: A
authors.lastname: Sun
authors.forename: Shengjun
authors.initials: S
authors.lastname: Nie
authors.forename: Da
authors.initials: D
authors.lastname: Xing
mesh_terms: D021581:Active Transport, Cell Nucleus; D000975:Antioxidants / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D060467:Disease Resistance; D004789:Enzyme Activation; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005936:Glucans / Q000378:metabolism; D006706:Homeostasis; D008070:Lipopolysaccharides / Q000276:immunology*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D010935:Plant Diseases / Q000276:immunology / Q000382:microbiology; D057865:Plant Immunity; D018515:Plant Leaves / Q000276:immunology / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D044224:Pseudomonas syringae / Q000276:immunology / Q000472:pathogenicity; D000099188:Alternative Oxidase
chemical_list: D000975:Antioxidants; D029681:Arabidopsis Proteins; D005936:Glucans; D008070:Lipopolysaccharides; D024101:Mitochondrial Proteins; D009569:Nitric Oxide; D010088:Oxidoreductases; D010940:Plant Proteins; D000099188:Alternative Oxidase; C105496:NPR1 protein, Arabidopsis; C048306:callose