title: Acylated monogalactosyl diacylglycerol: prevalence in the plant kingdom and identification of an enzyme catalyzing galactolipid head group acylation in Arabidopsis thaliana.
abstract: The lipid phase of the thylakoid membrane is mainly composed of the galactolipids mono- and digalactosyl diacylglycerol (MGDG and DGDG, respectively). It has been known since the late 1960s that MGDG can be acylated with a third fatty acid to the galactose head group (acyl-MGDG) in plant leaf homogenates. In certain brassicaceous plants like Arabidopsis thaliana, the acyl-MGDG frequently incorporates oxidized fatty acids in the form of the jasmonic acid precursor 12-oxo-phytodienoic acid (OPDA). In the present study we further investigated the distribution of acylated and OPDA-containing galactolipids in the plant kingdom. While acyl-MGDG was found to be ubiquitous in green tissue of plants ranging from non-vascular plants to angiosperms, OPDA-containing galactolipids were only present in plants from a few genera. A candidate protein responsible for the acyl transfer was identified in Avena sativa (oat) leaf tissue using biochemical fractionation and proteomics. Knockout of the orthologous gene in A. thaliana resulted in an almost total elimination of the ability to form both non-oxidized and OPDA-containing acyl-MGDG. In addition, heterologous expression of the A. thaliana gene in E. coli demonstrated that the protein catalyzed acylation of MGDG. We thus demonstrate that a phylogenetically conserved enzyme is responsible for the accumulation of acyl-MGDG in A. thaliana. The activity of this enzyme in vivo is strongly enhanced by freezing damage and the hypersensitive response.
authors.affiliation: Department of Biological- and Environmental Sciences, University of Gothenburg, Box 461, Göteborg, SE-405 30, Sweden.
authors.forename: Anders K
authors.initials: AK
authors.lastname: Nilsson
authors.affiliation: Department of Biological- and Environmental Sciences, University of Gothenburg, Box 461, Göteborg, SE-405 30, Sweden.
authors.forename: Oskar N
authors.initials: ON
authors.lastname: Johansson
authors.affiliation: Department of Biological- and Environmental Sciences, University of Gothenburg, Box 461, Göteborg, SE-405 30, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Fahlberg
authors.affiliation: Department of Biological- and Environmental Sciences, University of Gothenburg, Box 461, Göteborg, SE-405 30, Sweden.
authors.forename: Murali
authors.initials: M
authors.lastname: Kommuri
authors.affiliation: Department of Biological- and Environmental Sciences, University of Gothenburg, Box 461, Göteborg, SE-405 30, Sweden.
authors.forename: Mats
authors.initials: M
authors.lastname: Töpel
authors.affiliation: Department of Biological- and Environmental Sciences, University of Gothenburg, Box 461, Göteborg, SE-405 30, Sweden.
authors.forename: Lovisa J
authors.initials: LJ
authors.lastname: Bodin
authors.affiliation: Department of Biological- and Environmental Sciences, University of Gothenburg, Box 461, Göteborg, SE-405 30, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Sikora
authors.affiliation: Department of Biological- and Environmental Sciences, University of Gothenburg, Box 461, Göteborg, SE-405 30, Sweden.
authors.forename: Masoomeh
authors.initials: M
authors.lastname: Modarres
authors.affiliation: Department of Glycoscience, School of Biotechnology, KTH Royal Institute of Technology, Stockholm, SE-106 91, Sweden.
authors.forename: Sophia
authors.initials: S
authors.lastname: Ekengren
authors.affiliation: Department of Plant Molecular Biology, University of Lausanne, Biophore, 1015, Lausanne, Switzerland.
authors.forename: Chi T
authors.initials: CT
authors.lastname: Nguyen
authors.affiliation: Department of Plant Molecular Biology, University of Lausanne, Biophore, 1015, Lausanne, Switzerland.
authors.forename: Edward E
authors.initials: EE
authors.lastname: Farmer
authors.affiliation: Department of Pure and Applied Biochemistry, Lund University, Lund, SE-221 00, Sweden.
authors.forename: Olof
authors.initials: O
authors.lastname: Olsson
authors.affiliation: Department of Biological- and Environmental Sciences, University of Gothenburg, Box 461, Göteborg, SE-405 30, Sweden.
authors.forename: Mats
authors.initials: M
authors.lastname: Ellerström
authors.affiliation: Department of Biological- and Environmental Sciences, University of Gothenburg, Box 461, Göteborg, SE-405 30, Sweden.
authors.forename: Mats X
authors.initials: MX
authors.lastname: Andersson
mesh_terms: D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D038983:Galactolipids / Q000737:chemistry / Q000378:metabolism*; D017353:Gene Deletion; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D010802:Phylogeny; D014026:Nicotiana / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D038983:Galactolipids; C009909:monogalactosyldiacylglycerol; D000217:Acyltransferases; C000611664:At2g42690 protein, Arabidopsis
keywords: Arabidopsis thaliana; Avena sativa; acylated MGDG; galactolipids; hypersensitive response; thylakoid membrane; wounding