title: Arabidopsis acyl-CoA-binding proteins ACBP4 and ACBP5 are subcellularly localized to the cytosol and ACBP4 depletion affects membrane lipid composition.
abstract: In Arabidopsis thaliana, acyl-CoA-binding proteins (ACBPs) are encoded by six genes, and they display varying affinities for acyl-CoA esters. Recombinant ACBP4 and ACBP5 have been shown to bind oleoyl-CoA esters in vitro. In this study, the subcellular localizations of ACBP4 and ACBP5 were determined by biochemical fractionation followed by western blot analyses using anti-ACBP4 and anti-ACBP5 antibodies and immuno-electron microscopy. Confocal microscopy of autofluorescence-tagged ACBP4 and ACBP5, expressed transiently in onion epidermal cells and in transgenic Arabidopsis, confirmed their expression in the cytosol. Taken together, ACBP4 and ACBP5 are available in the cytosol to bind and transfer cytosolic oleoyl-CoA esters. Lipid profile analysis further revealed that an acbp4 knockout mutant showed decreases in membrane lipids (digalactosyldiacylglycerol, monogalactosyldiacylglycerol, phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol) while acbp4-complemented lines attained levels similar to wild type, suggesting that ACBP4 plays a role in the biosynthesis of membrane lipids including galactolipids and phospholipids.
authors.affiliation: School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Shi
authors.initials: S
authors.lastname: Xiao
authors.forename: Hong-Ye
authors.initials: HY
authors.lastname: Li
authors.forename: Jiao-Ping
authors.initials: JP
authors.lastname: Zhang
authors.forename: Suk-Wah
authors.initials: SW
authors.lastname: Chan
authors.forename: Mee-Len
authors.initials: ML
authors.lastname: Chye
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D001483:Base Sequence; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism*; D017931:DNA Primers; D055786:Gene Knockout Techniques; D008563:Membrane Lipids / Q000378:metabolism*; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D030821:Plants, Genetically Modified; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: C495420:ACBP4 protein, Arabidopsis; C495421:ACBP5 protein, Arabidopsis; D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D017931:DNA Primers; D008563:Membrane Lipids; D011993:Recombinant Fusion Proteins
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