title: Reduced Biosynthesis of Digalactosyldiacylglycerol, a Major Chloroplast Membrane Lipid, Leads to Oxylipin Overproduction and Phloem Cap Lignification in Arabidopsis.
abstract: DIGALACTOSYLDIACYLGLYCEROL SYNTHASE1 (DGD1) is a chloroplast outer membrane protein responsible for the biosynthesis of the lipid digalactosyldiacylglycerol (DGDG) from monogalactosyldiacylglycerol (MGDG). The Arabidopsis thaliana dgd1 mutants have a greater than 90% reduction in DGDG content, reduced photosynthesis, and altered chloroplast morphology. However, the most pronounced visible phenotype is the extremely short inflorescence stem, but how deficient DGDG biosynthesis causes this phenotype is unclear. We found that, in dgd1 mutants, phloem cap cells were lignified and jasmonic acid (JA)-responsive genes were highly upregulated under normal growth conditions. The coronative insensitive1 dgd1 and allene oxide synthase dgd1 double mutants no longer exhibited the short inflorescence stem and lignification phenotypes but still had the same lipid profile and reduced photosynthesis as dgd1 single mutants. Hormone and lipidomics analyses showed higher levels of JA, JA-isoleucine, 12-oxo-phytodienoic acid, and arabidopsides in dgd1 mutants. Transcript and protein level analyses further suggest that JA biosynthesis in dgd1 is initially activated through the increased expression of genes encoding 13-lipoxygenases (LOXs) and phospholipase A-Iγ3 (At1g51440), a plastid lipase with a high substrate preference for MGDG, and is sustained by further increases in LOX and allene oxide cyclase mRNA and protein levels. Our results demonstrate a link between the biosynthesis of DGDG and JA.
authors.affiliation: Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan.
authors.forename: Yang-Tsung
authors.identifier: http://orcid.org/0000-0001-8826-4251
authors.initials: YT
authors.lastname: Lin
authors.affiliation: Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan.
authors.forename: Lih-Jen
authors.initials: LJ
authors.lastname: Chen
authors.affiliation: Georg-August-University Goettingen, Albrecht-von-Haller-Institute for Plant Sciences, Department of Plant Biochemistry, D-37077 Goettingen, Germany.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Herrfurth
authors.affiliation: Georg-August-University Goettingen, Albrecht-von-Haller-Institute for Plant Sciences, Department of Plant Biochemistry, D-37077 Goettingen, Germany Georg-August-University Goettingen, Goettingen Center for Molecular Biosciences, Department of Plant Biochemistry, D-37077 Goettingen, Germany.
authors.forename: Ivo
authors.identifier: http://orcid.org/0000-0002-9888-7003
authors.initials: I
authors.lastname: Feussner
authors.affiliation: Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan mbhmli@gate.sinica.edu.tw.
authors.forename: Hsou-Min
authors.identifier: http://orcid.org/0000-0002-0211-7339
authors.initials: HM
authors.lastname: Li
mesh_terms: D000483:Alleles; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D053898:Biosynthetic Pathways / Q000187:drug effects; D002736:Chloroplasts / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D003517:Cyclopentanes / Q000494:pharmacology; D005030:Ethylenes / Q000378:metabolism; D038983:Galactolipids / Q000096:biosynthesis*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D007210:Indoleacetic Acids / Q000378:metabolism; D056626:Inflorescence / Q000033:anatomy & histology; D008031:Lignin / Q000378:metabolism*; D008563:Membrane Lipids / Q000096:biosynthesis*; D009154:Mutation / Q000235:genetics; D054883:Oxylipins / Q000378:metabolism* / Q000494:pharmacology; D010641:Phenotype; D052585:Phloem / Q000187:drug effects / Q000378:metabolism*; D010788:Photosynthesis / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics
chemical_list: D003517:Cyclopentanes; D005030:Ethylenes; D038983:Galactolipids; D007210:Indoleacetic Acids; D008563:Membrane Lipids; D054883:Oxylipins; C007388:digalactosyldiacylglycerol; C011006:jasmonic acid; D008031:Lignin; C036216:ethylene