title: Roles of a membrane-bound caleosin and putative peroxygenase in biotic and abiotic stress responses in Arabidopsis.
abstract: We report here the localisation and properties of a new membrane-bound isoform of caleosin and its putative role as a peroxygenase involved in oxylipin metabolism during biotic and abiotic stress responses in Arabidopsis. Caleosins are a family of lipid-associated proteins that are ubiquitous in plants and true fungi. Previous research has focused on lipid-body associated, seed-specific caleosins that have peroxygenase activity. Here, we demonstrate that a separate membrane-bound constitutively expressed caleosin isoform (Clo-3) is highly upregulated following exposure to abiotic stresses, such as salt and drought, and to biotic stress such as pathogen infection. The Clo-3 protein binds one atom of calcium per molecule, is phosphorylated in response to stress, and has a similar peroxygenase activity to the seed-specific Clo-1 isoform. Clo-3 is present in microsomal and chloroplast envelope fractions and has a type I membrane orientation with about 2 kDa of the C terminal exposed to the cytosol. Analysis of Arabidopsis ABA and related mutant lines implies that Clo-3 is involved in the generation of oxidised fatty acids in stress related signalling pathways involving both ABA and salicylic acid. We propose that Clo-3 is part of an oxylipin pathway induced by multiple stresses and may also generate fatty acid derived anti-fungal compounds for plant defence.
authors.affiliation: Biotechnology Unit, Division of Biological Sciences, University of Glamorgan, Treforest, CF37 1DL, United Kingdom.
authors.forename: Mark
authors.initials: M
authors.lastname: Partridge
authors.forename: Denis J
authors.initials: DJ
authors.lastname: Murphy
mesh_terms: D017360:Arabidopsis / Q000235:genetics*; D002135:Calcium-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D019286:Endopeptidase K / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D018745:Genome, Plant; D008055:Lipids; D008565:Membrane Proteins / Q000378:metabolism; D008954:Models, Biological; D010766:Phosphorylation; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D020033:Protein Isoforms; D012459:Salicylates / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; D008055:Lipids; D008565:Membrane Proteins; D010940:Plant Proteins; D020033:Protein Isoforms; D012459:Salicylates; C402836:caleosin protein, Sesamum indicum; D019286:Endopeptidase K