title: Antagonistic role of 9-lipoxygenase-derived oxylipins and ethylene in the control of oxidative stress, lipid peroxidation and plant defence.
abstract: 9-lipoxygenases (9-LOXs) initiate fatty acid oxygenation in plant tissues, with formation of 9-hydroxy-10,12,15-octadecatrienoic acid (9-HOT) from linolenic acid. A lox1 lox5 mutant, which is deficient in 9-LOX activity, and two mutants noxy6 and noxy22 (non-responding to oxylipins), which are insensitive to 9-HOT, have been used to investigate 9-HOT signalling. Map-based cloning indicated that the noxy6 and noxy22 mutations are located at the CTR1 (CONSTITUTIVE ETHYLENE RESPONSE1) and ETO1 (ETHYLENE-OVERPRODUCER1) loci, respectively. In agreement, the noxy6 and noxy22 mutants, renamed as ctr1-15 and eto1-14, respectively, showed enhanced ethylene (ET) production. The correlation between increased ET production and reduced 9-HOT sensitivity indicated by these results was supported by experiments in which exogenously added ethylene precursor ACC (1-aminocyclopropane-1-carboxylic acid) impaired the responses to 9-HOT. Moreover, a reciprocal interaction between ET and 9-HOT signalling was indicated by results showing that the effect of ACC was reduced in the presence of 9-HOT. We found that the 9-LOX and ET pathways regulate the response to the lipid peroxidation-inducer singlet oxygen. Thus, the massive transcriptional changes seen in wild-type plants in response to singlet oxygen were greatly affected in the lox1 lox5 and eto1-14 mutants. Furthermore, these mutants displayed enhanced susceptibility to both singlet oxygen and Pseudomonas syringae pv. tomato, in the latter case leading to increased accumulation of the lipid peroxidation product malondialdehyde. These findings demonstrate an antagonistic relationship between products of the 9-LOX and ET pathways, and suggest a role for the 9-LOX pathway in modulating oxidative stress, lipid peroxidation and plant defence.
authors.affiliation: Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, CSIC, Campus Universidad Autónoma, Cantoblanco, E-28049 Madrid, Spain.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: López
authors.forename: Jorge
authors.initials: J
authors.lastname: Vicente
authors.forename: Satish
authors.initials: S
authors.lastname: Kulasekaran
authors.forename: Tamara
authors.initials: T
authors.lastname: Vellosillo
authors.forename: Marta
authors.initials: M
authors.lastname: Martínez
authors.forename: Maria L
authors.initials: ML
authors.lastname: Irigoyen
authors.forename: Tomas
authors.initials: T
authors.lastname: Cascón
authors.forename: Gerard
authors.initials: G
authors.lastname: Bannenberg
authors.forename: Mats
authors.initials: M
authors.lastname: Hamberg
authors.forename: Carmen
authors.initials: C
authors.lastname: Castresana
mesh_terms: D000598:Amino Acids, Cyclic / Q000494:pharmacology; D017360:Arabidopsis / Q000187:drug effects* / Q000235:genetics / Q000382:microbiology / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D005030:Ethylenes / Q000378:metabolism*; D005227:Fatty Acids / Q000494:pharmacology; D005453:Fluorescence; D018506:Gene Expression Regulation, Plant; D007651:Keto Acids / Q000494:pharmacology; D015227:Lipid Peroxidation; D008315:Malondialdehyde / Q000378:metabolism; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D054883:Oxylipins / Q000138:chemical synthesis / Q000494:pharmacology*; D010641:Phenotype; D010935:Plant Diseases / Q000382:microbiology; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D044224:Pseudomonas syringae / Q000472:pathogenicity; D036226:Seedlings / Q000187:drug effects / Q000502:physiology; D015398:Signal Transduction; D026082:Singlet Oxygen / Q000494:pharmacology; D014158:Transcription, Genetic
chemical_list: C562212:9-keto-10(E),12(Z),15(Z)-octadecatrienoic acid; D000598:Amino Acids, Cyclic; D029681:Arabidopsis Proteins; C485242:ETO1 protein, Arabidopsis; D005030:Ethylenes; D005227:Fatty Acids; D007651:Keto Acids; D054883:Oxylipins; D026082:Singlet Oxygen; C054931:9-oxononanoic acid; C023863:1-aminocyclopropane-1-carboxylic acid; D008315:Malondialdehyde; C036216:ethylene; D011494:Protein Kinases; C477753:CTR1 protein, Arabidopsis