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Title: 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 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 ArabidopsisAAE13(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 cytosolicAAE13 protein is not essential, due to the presence of a redundant malonyl‐CoA generating system provided by a cytosolic acetyl‐CoA carboxylase, the mitochondrialAAE13 protein is essential for plant growth. Phenotypes of theaae13‐1mutant are transgenically reversed only if the mitochondrial pre‐sequence is present in the ectopically expressedAAE13 proteins. Theaae13‐1mutant 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 theaae13‐1mutant is grown in a non‐photorespiratory condition (i.e. a 1%CO2atmosphere), demonstrating that they are a consequence of the deficiency in photorespiration due to the inability to generate lipoic acid from mitochondrially synthesized fatty acids.

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Author(s) / Creator(s):
Publisher / Repository:
Date Published:
Journal Name:
The Plant Journal
Page Range / eLocation ID:
p. 581-593
Medium: X
Sponsoring Org:
National Science Foundation
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