Fatty acid export from the chloroplast. Molecular characterization of a major plastidial acyl-coenzyme A synthetase from Arabidopsis.
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.
Institute of Biological Chemistry, Washington State University, P.O. Box 646340, Pullman, Washington 99164-6340, USA.
Judy A
JA
Schnurr
Jay M
JM
Shockey
Gert-Jan
GJ
de Boer
John A
JA
Browse
D000214:Acyl Coenzyme A / Q000378:metabolism; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002736:Chloroplasts / Q000201:enzymology / Q000378:metabolism*; D003066:Coenzyme A Ligases / Q000235:genetics* / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D049452:Green Fluorescent Proteins; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D019697:Onions / Q000235:genetics / Q000378:metabolism; D018532:Pisum sativum / Q000166:cytology / Q000378:metabolism; D010641:Phenotype; D019441:Plant Epidermis / Q000235:genetics / Q000378:metabolism
D000214:Acyl Coenzyme A; D029681:Arabidopsis Proteins; D005227:Fatty Acids; D007527:Isoenzymes; D008164:Luminescent Proteins; D049452:Green Fluorescent Proteins; D003066:Coenzyme A Ligases; C468564:LACS9 protein, Arabidopsis