title: Barley has two peroxisomal ABC transporters with multiple functions in β-oxidation.
abstract: In oilseed plants, peroxisomal β-oxidation functions not only in lipid catabolism but also in jasmonate biosynthesis and metabolism of pro-auxins. Subfamily D ATP-binding cassette (ABC) transporters mediate import of β-oxidation substrates into the peroxisome, and the Arabidopsis ABCD protein, COMATOSE (CTS), is essential for this function. Here, the roles of peroxisomal ABCD transporters were investigated in barley, where the main storage compound is starch. Barley has two CTS homologues, designated HvABCD1 and HvABCD2, which are widely expressed and present in embryo and aleurone tissues during germination. Suppression of both genes in barley RNA interference (RNAi) lines indicated roles in metabolism of 2,4-dichlorophenoxybutyrate (2,4-DB) and indole butyric acid (IBA), jasmonate biosynthesis, and determination of grain size. Transformation of the Arabidopsis cts-1 null mutant with HvABCD1 and HvABCD2 confirmed these findings. HvABCD2 partially or completely complemented all tested phenotypes of cts-1. In contrast, HvABCD1 failed to complement the germination and establishment phenotypes of cts-1 but increased the sensitivity of hypocotyls to 100 μM IBA and partially complemented the seed size phenotype. HvABCD1 also partially complemented the yeast pxa1/pxa2Δ mutant for fatty acid β-oxidation. It is concluded that the core biochemical functions of peroxisomal ABC transporters are largely conserved between oilseeds and cereals but that their physiological roles and importance may differ.
authors.affiliation: Division of Plant and Crop Sciences, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, UK.
authors.forename: Guillermina M
authors.initials: GM
authors.lastname: Mendiondo
authors.affiliation: Division of Plant and Crop Sciences, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, UK.
authors.forename: Anne
authors.initials: A
authors.lastname: Medhurst
authors.affiliation: Laboratory of Genetic Metabolic Diseases, Academic Medical Centre, University of Amsterdam, 1105 AZ, Amsterdam, The Netherlands.
authors.forename: Carlo W
authors.initials: CW
authors.lastname: van Roermund
authors.affiliation: Biological Chemistry and Crop Protection Department, Rothamsted Research, Harpenden AL5 2JQ, UK.
authors.forename: Xuebin
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Plant Biology and Crop Science Department, Rothamsted Research, Harpenden AL5 2JQ, UK.
authors.forename: Jean
authors.initials: J
authors.lastname: Devonshire
authors.affiliation: Division of Plant and Crop Sciences, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, UK.
authors.forename: Duncan
authors.initials: D
authors.lastname: Scholefield
authors.affiliation: Division of Plant and Crop Sciences, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, UK.
authors.forename: José
authors.initials: J
authors.lastname: Fernández
authors.affiliation: SABMiller plc., SABMiller House, Church Street, West Woking, Surrey GU21 6HS, UK.
authors.forename: Barry
authors.initials: B
authors.lastname: Axcell
authors.affiliation: Division of Plant Sciences, College of life Sciences, University of Dundee and The James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK.
authors.forename: Luke
authors.initials: L
authors.lastname: Ramsay
authors.affiliation: Laboratory of Genetic Metabolic Diseases, Academic Medical Centre, University of Amsterdam, 1105 AZ, Amsterdam, The Netherlands.
authors.forename: Hans R
authors.initials: HR
authors.lastname: Waterham
authors.affiliation: Division of Plant Sciences, College of life Sciences, University of Dundee and The James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK.
authors.forename: Robbie
authors.initials: R
authors.lastname: Waugh
authors.affiliation: Biological Chemistry and Crop Protection Department, Rothamsted Research, Harpenden AL5 2JQ, UK freddie.theodoulou@rothamsted.ac.uk michael.holdsworth@nottingham.ac.uk.
authors.forename: Frederica L
authors.initials: FL
authors.lastname: Theodoulou
authors.affiliation: Division of Plant and Crop Sciences, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, UK freddie.theodoulou@rothamsted.ac.uk michael.holdsworth@nottingham.ac.uk.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Holdsworth
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics* / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001467:Hordeum / Q000235:genetics* / Q000378:metabolism; D030781:Organisms, Genetically Modified / Q000235:genetics / Q000378:metabolism; D010084:Oxidation-Reduction; D020675:Peroxisomes / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; D029681:Arabidopsis Proteins
keywords: Aleurone; gene duplication; germination; indole butyric acid; oil body; seed size.