title: Oleic acid-dependent modulation of NITRIC OXIDE ASSOCIATED1 protein levels regulates nitric oxide-mediated defense signaling in Arabidopsis.
abstract: The conserved cellular metabolites nitric oxide (NO) and oleic acid (18:1) are well-known regulators of disease physiologies in diverse organism. We show that NO production in plants is regulated via 18:1. Reduction in 18:1 levels, via a genetic mutation in the 18:1-synthesizing gene SUPPRESSOR OF SA INSENSITIVITY OF npr1-5 (SSI2) or exogenous application of glycerol, induced NO accumulation. Furthermore, both NO application and reduction in 18:1 induced the expression of similar sets of nuclear genes. The altered defense signaling in the ssi2 mutant was partially restored by a mutation in NITRIC OXIDE ASSOCIATED1 (NOA1) and completely restored by double mutations in NOA1 and either of the nitrate reductases. Biochemical studies showed that 18:1 physically bound NOA1, in turn leading to its degradation in a protease-dependent manner. In concurrence, overexpression of NOA1 did not promote NO-derived defense signaling in wild-type plants unless 18:1 levels were lowered. Subcellular localization showed that NOA1 and the 18:1 synthesizing SSI2 proteins were present in close proximity within the nucleoids of chloroplasts. Indeed, pathogen-induced or low-18:1-induced accumulation of NO was primarily detected in the chloroplasts and their nucleoids. Together, these data suggest that 18:1 levels regulate NO synthesis, and, thereby, NO-mediated signaling, by regulating NOA1 levels.
authors.affiliation: Department of Plant Pathology, University of Kentucky, Lexington, Kentucky 40546, USA.
authors.forename: Mihir Kumar
authors.initials: MK
authors.lastname: Mandal
authors.forename: A C
authors.initials: AC
authors.lastname: Chandra-Shekara
authors.forename: Rae-Dong
authors.initials: RD
authors.lastname: Jeong
authors.forename: Keshun
authors.initials: K
authors.lastname: Yu
authors.forename: Shifeng
authors.initials: S
authors.lastname: Zhu
authors.forename: Bidisha
authors.initials: B
authors.lastname: Chanda
authors.forename: Duroy
authors.initials: D
authors.lastname: Navarre
authors.forename: Aardra
authors.initials: A
authors.lastname: Kachroo
authors.forename: Pradeep
authors.initials: P
authors.lastname: Kachroo
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000187:drug effects / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D009569:Nitric Oxide / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism*; D019301:Oleic Acid / Q000378:metabolism*; D010641:Phenotype; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D029681:Arabidopsis Proteins; D019301:Oleic Acid; D009569:Nitric Oxide; C521947:NOA1 protein, Arabidopsis; D019001:Nitric Oxide Synthase; D020558:GTP Phosphohydrolases