Mitochondrial Fatty Acid Synthase Utilizes Multiple Acyl Carrier Protein Isoforms1[OPEN]

Acyl carrier protein (ACP) is a highly conserved cofactor protein that is required by Type II fatty acid synthases (FASs). Here, we demonstrate that up to three mitochondrial ACP (mtACP) isoforms support the Arabidopsis (Arabidopsis thaliana) mitochondrially localized Type II FAS. The physiological importance of the three mtACPs was evaluated by characterizing the single, double, and triple mutants. ThemtACP1(At2g44620),mtACP2(At1g65290), andmtACP3(At5g47630) single mutants showed no discernible morphological growth phenotype. Functional redundancy among the three mtACPs was indicated by the embryo-lethal phenotype associated with simultaneous loss of all threemtACPgenes. Characterization of all double mutant combinations revealed that although themtacp1 mtacp3andmtacp2 mtacp3double mutant combinations showed no observable growth defect, themtacp1 mtacp2double mutant was viable but displayed delayed growth, reduced levels of posttranslationally lipoylated mitochondrial proteins, hyperaccumulation of photorespiratory Gly, and reduced accumulation of many intermediates in central metabolism. These alterations were partially reversed when themtacp1 mtacp2double mutant plants were grown in a nonphotorespiratory condition (i.e. 1% CO(2)atmosphere) or in the presence of 2% Suc. In summary, mtACP, as a key component of mitochondrial fatty acid biosynthesis, is important in generating the fatty acid precursor of lipoic acid biosynthesis. Thus, the incomplete lipoylation of mitochondrial proteins inmtacpmutants, particularly Gly decarboxylase, affects the recovery of photorespiratory carbon, and this appears to be critical during embryogenesis. Three partially redundant acyl carrier protein isoforms support mitochondrial fatty acid biosynthesis.