Fatty Acid Export from the Chloroplast. Molecular Characterization of a Major Plastidial Acyl-Coenzyme A Synthetase from Arabidopsis

• Published in: Plant physiology (Bethesda) Vol. 129; no. 4; pp. 1700 - 1709
• Main Authors: Judy A. Schnurr, Jay M. Shockey, Gert-Jan de Boer, Browse, John A.
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Biologists 01.08.2002; American Society of Plant Physiologists
• Subjects: Acyl Coenzyme A - metabolism; Agronomy. Soil science and plant productions; Arabidopsis - enzymology; Arabidopsis - genetics; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Biochemical Processes and Macromolecular Structures; Biological and medical sciences; Chloroplasts; Chloroplasts - enzymology; Chloroplasts - metabolism; Coenzyme A Ligases - genetics; Coenzyme A Ligases - metabolism; Economic plant physiology; Fatty acids; Fatty Acids - metabolism; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; Genetics; Green Fluorescent Proteins; Isoenzymes - genetics; Isoenzymes - metabolism; Leaves; Lipid metabolism; Lipids; Luminescent Proteins - genetics; Luminescent Proteins - metabolism; Metabolism; Metabolism. Physicochemical requirements; Mutation; Nitrogen metabolism and other ones (excepting carbon metabolism); Nutrition. Photosynthesis. Respiration. Metabolism; Onions - genetics; Onions - metabolism; Phenotype; Pisum sativum - cytology; Pisum sativum - metabolism; Plant cells; Plant Epidermis - genetics; Plant Epidermis - metabolism; Plant growth; Plant physiology and development; Plants; Plastids; Protein isoforms; RNA; Enzyme; Isozyme; Biological transport; Carbon-sulfur ligases; Biosynthesis; Identification; Metabolic pathway; Fatty acids; Long-chain-fatty-acid-CoA ligase; Arabidopsis thaliana; Characterization; Cruciferae; Ligases; Dicotyledones; Angiospermae; Spermatophyta; Experimental plant; Localization; Chloroplast
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.003251

Acyl-coenzyme A (CoA) synthetases (ACSs, EC 6.2.1.3) catalyze the formation of fatty acyl-CoAs from free fatty acid, ATP, and CoA. Essentially all de novo fatty acid synthesis occurs in the plastid. Fatty acids destined for membrane glycerolipid and triacylglycerol synthesis in the endoplasmic reticulum must be first activated to acyl-CoAs via an ACS. Within a family of nine ACS genes from Arabidopsis, we identified a chloroplast isoform, LACS9. LACS9 is highly expressed in developing seeds and young rosette leaves. Both in vitro chloroplast import assays and transient expression of a green fluorescent protein fusion indicated that the LACS9 protein is localized in the plastid envelope. A T-DNA knockout mutant (lacs9-1) was identified by reverse genetics and these mutant plants were indistinguishable from wild type in growth and appearance. Analysis of leaf lipids provided no evidence for compromised export of acyl groups from chloroplasts. However, direct assays demonstrated that lacs9-1 plants contained only 10% of the chloroplast long-chain ACS activity found for wild type. The residual long-chain ACS activity in mutant chloroplasts was comparable with calculated rates of fatty acid synthesis. Although another isozyme contributes to the activation of fatty acids during their export from the chloroplast, LACS9 is a major chloroplast ACS.