Document Detail

Involvement of Arabidopsis ACYL-COENZYME A DESATURASE-LIKE2 (At2g31360) in the biosynthesis of the very-long-chain monounsaturated fatty acid components of membrane lipids.
MedLine Citation:
PMID:  23175755     Owner:  NLM     Status:  MEDLINE    
The Arabidopsis (Arabidopsis thaliana) acyl-coenzyme A (CoA) desaturase-like (ADS) gene family contains nine genes encoding fatty acid desaturase-like proteins. The biological function of only one member of the family, fatty acid desaturase5 (AtADS3/FAD5, At3g15850), is known, and this gene encodes the plastidic palmitoyl-monogalactosyldiacylglycerol Δ7 desaturase. We cloned seven members of the gene family that are predicted not to have a chloroplast transit peptide and expressed them in the yeast Saccharomyces cerevisiae. All seven have previously undescribed desaturase activity on very-long-chain fatty acid (VLCFA) substrates and exhibit diverse regiospecificity, catalyzing introduction of double bonds relative to the methyl end of the molecule (n-x) at n-6 (AtADS4, At1g06350), n-7 (AtADS1.3, At1g06100 and AtADS4.2, At1g06360), n-9 (AtADS1, At1g06080 and AtADS2, At2g31360) or Δ9 (relative to the carboxyl end of the molecule) positions (AtADS1.2, At1g06090 and AtADS1.4, At1g06120). Through forward and reverse genetics it was shown that AtADS2 is involved in the synthesis of the 24:1(n-9) and 26:1(n-9) components (X:Y, where X is chain length and Y is number of double bonds) of seed lipids, sphingolipids, and the membrane phospholipids phosphatidylserine, and phosphatidylethanolamine. Plants deficient in AtADS2 expression showed no obvious phenotype when grown under normal growing conditions, but showed an almost complete loss of phosphatidylethanolamine(42:4), phosphatidylserine(42:4), dihydroxy-monohexosylceramide(42:2)-2, trihydroxy-monohexosylceramide(42:2)-3, and trihydroxy-glycosylinositolphosphoceramide(42:2)-3, lipid species that contain the VLCFA 24:1(n-9), and trihydroxy-glycosylinositolphosphoceramide(44:2)-3, a lipid containing 26:1(n-9). Acyl-CoA profiling of these plants revealed a major reduction in 24:1-CoA and a small reduction in 26:1-CoA. Overexpression of AtADS2 resulted in a substantial increase in the percentage of glycerolipid and sphingolipids species containing 24:1 and a dramatic increase in the percentage of very-long-chain monounsaturated fatty acids in the acyl-CoA pool. Plants deficient in AtADS1 expression had reduced levels of 26:1(n-9) in seed lipids, but no significant changes in leaf phospholipids or sphingolipids were observed. These findings indicate that the 24-carbon and 26-carbon monounsaturated VLCFAs of Arabidopsis result primarily from VLCFA desaturation, rather than by elongation of long chain monounsaturated fatty acids.
Mark A Smith; Melanie Dauk; Hussein Ramadan; Hui Yang; Laura E Seamons; Richard P Haslam; Frédéric Beaudoin; Irving Ramirez-Erosa; Li Forseille
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2012-11-21
Journal Detail:
Title:  Plant physiology     Volume:  161     ISSN:  1532-2548     ISO Abbreviation:  Plant Physiol.     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2012-12-31     Completed Date:  2013-06-18     Revised Date:  2014-01-09    
Medline Journal Info:
Nlm Unique ID:  0401224     Medline TA:  Plant Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  81-96     Citation Subset:  IM    
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MeSH Terms
Acyl Coenzyme A / metabolism
Arabidopsis / enzymology*,  genetics
Arabidopsis Proteins / genetics,  metabolism*
Cloning, Molecular
DNA, Complementary / genetics,  metabolism
Enzyme Activation
Fatty Acid Desaturases / genetics,  metabolism*
Fatty Acids, Monounsaturated / metabolism*
Genes, Plant
Genetic Vectors / genetics,  metabolism
Membrane Lipids
Multigene Family
Phosphatidylethanolamines / metabolism
Plant Leaves / enzymology,  genetics
Reverse Genetics / methods
Saccharomyces cerevisiae / genetics,  metabolism
Seeds / genetics,  metabolism
Sphingolipids / metabolism
Substrate Specificity
Tobacco / genetics,  metabolism
Grant Support
//Biotechnology and Biological Sciences Research Council
Reg. No./Substance:
0/Acyl Coenzyme A; 0/Arabidopsis Proteins; 0/DNA, Complementary; 0/Fatty Acids, Monounsaturated; 0/Membrane Lipids; 0/Phosphatidylethanolamines; 0/Sphingolipids; EC 1.14.19.-/Fatty Acid Desaturases

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