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Plant Physiol. 2017 Apr;173(4):2010-2028. doi: 10.1104/pp.16.01732. Epub 2017 Feb 15.

Discovery and Characterization of the 3-Hydroxyacyl-ACP Dehydratase Component of the Plant Mitochondrial Fatty Acid Synthase System.

Guan X1,2,3, Okazaki Y1,2,3, Lithio A1,2,3, Li L1,2,3, Zhao X1,2,3, Jin H1,2,3, Nettleton D1,2,3, Saito K1,2,3, Nikolau BJ4,5,6.

Author information

1
Department of Biochemistry, Biophysics, and Molecular Biology (X.G., H.J., B.J.N.), National Science Foundation Engineering Research Center for Biorenewable Chemicals (X.G., B.J.N.), Department of Statistics (A.L., D.N.), Department of Genetics, Development, and Cellular Biology (L.L.), Laurence H. Baker Center for Bioinformatics and Biological Statistics (X.Z.), and Center for Metabolic Biology (B.J.N.), Iowa State University, Ames, Iowa 50011.
2
Metabolomics Research Group, RIKEN Center for Sustainable Resource Science, Yokohama 230-0045, Japan (Y.O., K.S.); and.
3
Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 260-8675, Japan (K.S.).
4
Department of Biochemistry, Biophysics, and Molecular Biology (X.G., H.J., B.J.N.), National Science Foundation Engineering Research Center for Biorenewable Chemicals (X.G., B.J.N.), Department of Statistics (A.L., D.N.), Department of Genetics, Development, and Cellular Biology (L.L.), Laurence H. Baker Center for Bioinformatics and Biological Statistics (X.Z.), and Center for Metabolic Biology (B.J.N.), Iowa State University, Ames, Iowa 50011; dimmas@iastate.edu.
5
Metabolomics Research Group, RIKEN Center for Sustainable Resource Science, Yokohama 230-0045, Japan (Y.O., K.S.); and dimmas@iastate.edu.
6
Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 260-8675, Japan (K.S.) dimmas@iastate.edu.

Abstract

We report the characterization of the Arabidopsis (Arabidopsis thaliana) 3-hydroxyacyl-acyl carrier protein dehydratase (mtHD) component of the mitochondrial fatty acid synthase (mtFAS) system, encoded by AT5G60335. The mitochondrial localization and catalytic capability of mtHD were demonstrated with a green fluorescent protein transgenesis experiment and by in vivo complementation and in vitro enzymatic assays. RNA interference (RNAi) knockdown lines with reduced mtHD expression exhibit traits typically associated with mtFAS mutants, namely a miniaturized morphological appearance, reduced lipoylation of lipoylated proteins, and altered metabolomes consistent with the reduced catalytic activity of lipoylated enzymes. These alterations are reversed when mthd-rnai mutant plants are grown in a 1% CO2 atmosphere, indicating the link between mtFAS and photorespiratory deficiency due to the reduced lipoylation of glycine decarboxylase. In vivo biochemical feeding experiments illustrate that sucrose and glycolate are the metabolic modulators that mediate the alterations in morphology and lipid accumulation. In addition, both mthd-rnai and mtkas mutants exhibit reduced accumulation of 3-hydroxytetradecanoic acid (i.e. a hallmark of lipid A-like molecules) and abnormal chloroplastic starch granules; these changes are not reversible by the 1% CO2 atmosphere, demonstrating two novel mtFAS functions that are independent of photorespiration. Finally, RNA sequencing analysis revealed that mthd-rnai and mtkas mutants are nearly equivalent to each other in altering the transcriptome, and these analyses further identified genes whose expression is affected by a functional mtFAS system but independent of photorespiratory deficiency. These data demonstrate the nonredundant nature of the mtFAS system, which contributes unique lipid components needed to support plant cell structure and metabolism.

PMID:
28202596
PMCID:
PMC5373057
DOI:
10.1104/pp.16.01732
[Indexed for MEDLINE]
Free PMC Article

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