title: Pathway for lipid A biosynthesis in Arabidopsis thaliana resembling that of Escherichia coli.
abstract: The lipid A moiety of Escherichia coli lipopolysaccharide is a hexa-acylated disaccharide of glucosamine that makes up the outer monolayer of the outer membrane. Arabidopsis thaliana contains nuclear genes encoding orthologs of key enzymes of bacterial lipid A biosynthesis, including LpxA, LpxC, LpxD, LpxB, LpxK and KdtA. Although structurally related lipid A molecules are found in most other gram-negative bacteria, lipid A and its precursors have not been directly detected in plants previously. However, homozygous insertional knockout mutations or RNAi knock-down constructs of Arabidopsis lpx and kdtA mutants revealed accumulation (or disappearance) of the expected monosaccharide or disaccharide lipid A precursors by mass spectrometry of total lipids extracted from 10-day old seedlings of these mutants. In addition, fluorescence microscopy of lpx-gfp fusions in transgenic Arabidopsis plants suggests that the Lpx and KdtA proteins are expressed and targeted to mitochondria. Although the structure of the lipid A end product generated by plants is still unknown, our work demonstrates that plants synthesize lipid A precursors using the same enzymatic pathway present in E. coli.
authors.affiliation: Department of Biochemistry, Duke University Medical Center, P.O. Box 3711, Durham, NC 27710, USA.
authors.forename: Chijun
authors.initials: C
authors.lastname: Li
authors.forename: Ziqiang
authors.initials: Z
authors.lastname: Guan
authors.forename: Dan
authors.initials: D
authors.lastname: Liu
authors.forename: Christian R H
authors.initials: CR
authors.lastname: Raetz
mesh_terms: D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D002874:Chromosome Mapping; D018744:DNA, Plant / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D055786:Gene Knockout Techniques; D017343:Genes, Plant; D006017:Glycolipids / Q000378:metabolism; D008050:Lipid A / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D053858:Metabolic Networks and Pathways; D008928:Mitochondria / Q000378:metabolism; D015394:Molecular Structure; D009154:Mutation; D030821:Plants, Genetically Modified; D013045:Species Specificity
chemical_list: D018744:DNA, Plant; D006017:Glycolipids; D008050:Lipid A; C044283:lipid X; D000217:Acyltransferases