Document Detail

No induction of beta-oxidation in leaves of Arabidopsis that over-produce lauric acid.
MedLine Citation:
PMID:  9951734     Owner:  NLM     Status:  MEDLINE    
Leaves from transgenic Brassica napus L. plants engineered to produce lauric acid show increased levels of enzyme activities of the pathways associated with fatty acid catabolism (V.A. Eccleston and J.B. Ohlrogge, 1998, Plant Cell 10: 613-621). In order to determine if the increases in enzyme activity are mirrored by increases in the expression of genes encoding enzymes of beta-oxidation, which is the major pathway of fatty acid catabolism in plants, the medium-chain acyl-acyl carrier protein (ACP) thioesterase MCTE from California bay (Umbellularia california) was over-expressed under the control of the cauliflower mosaic virus 35S promoter in Arabidopsis thaliana (L.) Heynh. Arabidopsis was the most suitable choice for these studies since gene expression could be analyzed in a large number of independent MCTE-expressing lines using already well-characterized beta-oxidation genes. Levels of MCTE transcripts in leaves varied widely over the population of plants analyzed. Furthermore, active MCTE was produced as determined by enzymatic analysis of leaf extracts of MCTE-expressing plants. These plants incorporated laurate into triacylglycerol of seeds, but not into lipids of leaves as shown by gaschromatographic analysis of total fatty acid extracts. The expression levels of the beta-oxidation and other genes that are highly expressed during developmental stages involving rapid fatty acid degradation were measured. No significant difference in gene expression was observed among MCTE-expressing plants and transgenic and non-transgenic controls. To eliminate the possibility that post-translational mechanisms are responsible for the observed increases in enzyme activity acyl-CoA oxidase activity was also measured in leaves of MCTE-expressing plants using medium and long chain acyl-CoA substrates. No significant increases in either medium- or long-chain acyl-CoA oxidase activities were detected. We conclude that endogenous beta-oxidation is sufficient to account for the complete degradation of laurate produced in rosette leaves of Arabidopsis expressing MCTE.
M A Hooks; Y Fleming; T R Larson; I A Graham
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Planta     Volume:  207     ISSN:  0032-0935     ISO Abbreviation:  Planta     Publication Date:  1999 Jan 
Date Detail:
Created Date:  1999-03-25     Completed Date:  1999-03-25     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  1250576     Medline TA:  Planta     Country:  GERMANY    
Other Details:
Languages:  eng     Pagination:  385-92     Citation Subset:  IM    
Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, UK.
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MeSH Terms
Acyl-CoA Oxidase
Arabidopsis / metabolism
Arabidopsis Proteins*
Gene Expression
Lauric Acids / metabolism*
Lipid Metabolism
Oxidoreductases / genetics
Plant Extracts
Plant Leaves / metabolism
Plants, Genetically Modified
Seeds / metabolism
Thiolester Hydrolases / genetics
Reg. No./Substance:
0/Arabidopsis Proteins; 0/Lauric Acids; 0/Plant Extracts; EC 1.-/Oxidoreductases; EC protein, Arabidopsis; EC Oxidase; EC 3.1.2.-/Thiolester Hydrolases; EC hydrolase

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