AAE13 encodes a dual‐localized malonyl‐CoA synthetase that is crucial for mitochondrial fatty acid biosynthesis

Malonyl‐CoA is a key intermediate in a number of metabolic processes associated with its role as a substrate in acylation and condensation reactions. These types of reactions occur in plastids, the cytosol and mitochondria, and although carboxylation of acetyl‐CoA is the known mechanism for generati...

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Published in:	The Plant journal : for cell and molecular biology 2016-03, Vol.85 (5), p.581-593
Main Authors:	Guan, Xin, Nikolau, Basil J
Format:	Article
Language:	eng
Subjects:	Accumulation acetyl coenzyme A Acetyl-CoA carboxylase Acylation Arabidopsis Arabidopsis Proteins - genetics Arabidopsis Proteins - metabolism Arabidopsis thaliana Atmosphere Bacterial Proteins - genetics Bacterial Proteins - metabolism Base Sequence Biosynthesis Blotting, Western Carbon dioxide Carboxylation Coding Coenzyme A Ligases - genetics Coenzyme A Ligases - metabolism Condensation condensation reactions Cytosol Cytosol - enzymology Depletion Fatty acids Fatty Acids - biosynthesis Fatty-acid synthase Gene Expression Profiling - methods Gene Expression Regulation, Plant genes Genetic Complementation Test genetically modified organisms Glycine glycine decarboxylase Green Fluorescent Proteins - genetics Green Fluorescent Proteins - metabolism Isoforms Lipoic acid Malonates - metabolism malonyl coenzyme A malonyl‐CoA synthetase Metabolism Microscopy, Confocal Mitochondria Mitochondria - enzymology Mitochondria - metabolism mitochondrial fatty acid synthase mutants Mutation palmitoylation phenotype Photorespiration Plant growth Plants, Genetically Modified Plastids Pools Proteins Redundancy Reverse Transcriptase Polymerase Chain Reaction Sequence Homology, Nucleic Acid Sucrose Sugars Transgenic plants
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Summary:	Malonyl‐CoA is a key intermediate in a number of metabolic processes associated with its role as a substrate in acylation and condensation reactions. These types of reactions occur in plastids, the cytosol and mitochondria, and although carboxylation of acetyl‐CoA is the known mechanism for generating the distinct plastidial and cytosolic pools, the metabolic origin of the mitochondrial malonyl‐CoA pool is still unclear. In this study we demonstrate that malonyl‐CoA synthetase encoded by the Arabidopsis AAE13 (AT3G16170) gene is localized in both the cytosol and the mitochondria. These isoforms are translated from two types of transcripts, one that contains and one that does not contain a mitochondrial‐targeting pre‐sequence. Whereas the cytosolic AAE13 protein is not essential, due to the presence of a redundant malonyl‐CoA generating system provided by a cytosolic acetyl‐CoA carboxylase, the mitochondrial AAE13 protein is essential for plant growth. Phenotypes of the aae13‐1 mutant are transgenically reversed only if the mitochondrial pre‐sequence is present in the ectopically expressed AAE13 proteins. The aae13‐1 mutant exhibits typical metabolic phenotypes associated with a deficiency in the mitochondrial fatty acid synthase system, namely depleted lipoylation of the H subunit of the photorespiratory enzyme glycine decarboxylase, increased accumulation of glycine and glycolate and reduced levels of sucrose. Most of these metabolic alterations, and associated morphological changes, are reversed when the aae13‐1 mutant is grown in a non‐photorespiratory condition (i.e. a 1% CO₂ atmosphere), demonstrating that they are a consequence of the deficiency in photorespiration due to the inability to generate lipoic acid from mitochondrially synthesized fatty acids.
ISSN:	0960-7412 1365-313X