The Role of Acetyl-CoA Synthetase in Arabidopsis

The acs1 knockout mutant that has a disruption in the plastidic acetyl-CoA synthetase (ACS, At5g36880) gene was used to explore the role of this protein and plastidic acetate metabolism in Arabidopsis thaliana. Disruption of the ACS gene decreased acetyl-CoA synthetase activity by 90% and largely blocked the incorporation of exogenous C-acetate and C-ethanol into fatty acids. While the disruption had no significant effect on the synthesis of bulk seed triacylglycerols, the acs1 plants were smaller and flowered later. This suggests that the pyruvate dehydrogenase bypass provided by the aerobic fermentation pathway that converts pyruvate to acetate and probably on to fatty acids is important to the plants during normal growth. The role of ACS in destroying fermentative intermediates is supported by the increased sensitivity of the acs1 mutant to exogenous acetate, ethanol and acetaldehyde compared to wildtype plants. While these observations suggest that flux through the aerobic fermentation pathway is important, the reason for this flux is unclear. Interestingly, acetate is able to support high rates of plant growth on media and this growth is blocked in the acs1 mutant.