title: The activity of HYDROPEROXIDE LYASE 1 regulates accumulation of galactolipids containing 12-oxo-phytodienoic acid in Arabidopsis.
abstract: Arabidopsis produces galactolipids containing esters of 12-oxo-phytodienoic acid (OPDA) and dinor-12-oxo-phytodienoic acid (dnOPDA). These lipids are referred to as arabidopsides and accumulate in response to abiotic and biotic stress. We explored the natural genetic variation found in 14 different Arabidopsis accessions to identify genes involved in the formation of arabidopsides. The accession C24 was identified as a poor accumulator of arabidopsides whereas the commonly used accession Col-0 was found to accumulate comparably large amounts of arabidopsides in response to tissue damage. A quantitative trait loci analysis of an F2 population created from a cross between C24 and Col-0 located a region on chromosome four strongly linked to the capacity to form arabidopsides. Expression analysis of HYDROPEROXIDE LYASE 1 (HPL1) showed large differences in transcript abundance between accessions. Transformation of Col-0 plants with the C24 HPL1 allele under transcriptional regulation of the 35S promoter revealed a strong negative correlation between HPL1 expression and arabidopside accumulation after tissue damage, thereby strengthening the view that HPL1 competes with ALLENE OXIDE SYNTHASE (AOS) for lipid-bound hydroperoxide fatty acids. We further show that the last step in the synthesis of galactolipid-bound OPDA and dnOPDA from unstable allene oxides is exclusively enzyme-catalyzed and not the result of spontaneous cyclization. Thus, the results presented here together with previous studies suggest that all steps in arabidopside biosynthesis are enzyme-dependent and apparently all reactions can take place with substrates being esterified to galactolipids.
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, Box 461, SE-405 30 Göteborg, Sweden.
authors.forename: Anders K
authors.initials: AK
authors.lastname: Nilsson
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, Box 461, SE-405 30 Göteborg, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Fahlberg
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, Box 461, SE-405 30 Göteborg, Sweden.
authors.forename: Oskar N
authors.initials: ON
authors.lastname: Johansson
authors.affiliation: Division of Chemistry II, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17 177 Stockholm, Sweden.
authors.forename: Mats
authors.initials: M
authors.lastname: Hamberg
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, Box 461, SE-405 30 Göteborg, Sweden.
authors.forename: Mats X
authors.initials: MX
authors.lastname: Andersson
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, Box 461, SE-405 30 Göteborg, Sweden mats.ellerstrom@gmail.com.
authors.forename: Mats
authors.initials: M
authors.lastname: Ellerström
mesh_terms: D000446:Aldehyde-Lyases / Q000235:genetics / Q000502:physiology*; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology*; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000502:physiology*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D038983:Galactolipids / Q000378:metabolism*; D014644:Genetic Variation; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000502:physiology*; D040641:Quantitative Trait Loci / Q000235:genetics / Q000502:physiology; D060888:Real-Time Polymerase Chain Reaction; D013312:Stress, Physiological / Q000235:genetics / Q000502:physiology
chemical_list: D029681:Arabidopsis Proteins; D005231:Fatty Acids, Unsaturated; D038983:Galactolipids; C025999:12-oxophytodienoic acid; D003577:Cytochrome P-450 Enzyme System; C000624429:HPL1 protein, Arabidopsis; D006899:Mixed Function Oxygenases; D000446:Aldehyde-Lyases; C054540:hydroperoxide lyase
keywords: Acyl-MGDG; Arabidopsis accessions; OPDA; arabidopsides; hydroperoxide lyase; jasmonates; natural variation.