title: Arabidopsis ECERIFERUM2 is a component of the fatty acid elongation machinery required for fatty acid extension to exceptional lengths.
abstract: Primary aerial surfaces of land plants are coated by a lipidic cuticle, which forms a barrier against transpirational water loss and protects the plant from diverse stresses. Four enzymes of a fatty acid elongase complex are required for the synthesis of very-long-chain fatty acid (VLCFA) precursors of cuticular waxes. Fatty acid elongase substrate specificity is determined by a condensing enzyme that catalyzes the first reaction carried out by the complex. In Arabidopsis (Arabidopsis thaliana), characterized condensing enzymes involved in wax synthesis can only elongate VLCFAs up to 28 carbons (C28) in length, despite the predominance of C29 to C31 monomers in Arabidopsis stem wax. This suggests additional proteins are required for elongation beyond C28. The wax-deficient mutant eceriferum2 (cer2) lacks waxes longer than C28, implying that CER2, a putative BAHD acyltransferase, is required for C28 elongation. Here, we characterize the cer2 mutant and demonstrate that green fluorescent protein-tagged CER2 localizes to the endoplasmic reticulum, the site of VLCFA biosynthesis. We use site-directed mutagenesis to show that the classification of CER2 as a BAHD acyltransferase based on sequence homology does not fit with CER2 catalytic activity. Finally, we provide evidence for the function of CER2 in C28 elongation by an assay in yeast (Saccharomyces cerevisiae).
authors.affiliation: Department of Botany, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada.
authors.forename: Tegan M
authors.initials: TM
authors.lastname: Haslam
authors.forename: Aurora
authors.initials: A
authors.lastname: Mañas-Fernández
authors.forename: Lifang
authors.initials: L
authors.lastname: Zhao
authors.forename: Ljerka
authors.initials: L
authors.lastname: Kunst
mesh_terms: D000217:Acyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020816:Amino Acid Motifs; D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D055162:Biocatalysis; D004721:Endoplasmic Reticulum / Q000201:enzymology; D005227:Fatty Acids / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009928:Organ Specificity; D010641:Phenotype; D019441:Plant Epidermis / Q000201:enzymology; D018515:Plant Leaves / Q000201:enzymology; D018547:Plant Stems / Q000648:ultrastructure; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014885:Waxes / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C101547:CER protein, Arabidopsis; D005227:Fatty Acids; D011993:Recombinant Fusion Proteins; D014885:Waxes; D049452:Green Fluorescent Proteins; D000217:Acyltransferases