Identification of a mitochondrial glycerol-3-phosphate dehydrogenase from Arabidopsis thaliana: Evidence for a mitochondrial glycerol-3-phosphate shuttle in plants

We report molecular characterization of an Arabidopsis gene encoding a mitochondrial FAD-dependent glycerol-3-phosphate dehydrogenase (FAD-GPDH) that oxidizes glycerol-3-phosphate (G-3-P) to dihydroxyacetone phosphate. We demonstrate through in vitro targeting assays that the encoded gene product can be imported into mitochondrial membrane systems. Enzyme activity of the protein was confirmed through heterologous expression in Escherichia coli. The Arabidopsis gene is expressed throughout plant development, but at the highest level during seed germination. We also show that expression of the Arabidopsis FAD-GPDH gene is coupled to oxygen consumption and affected by ABA and stress conditions. Together with an NAD⁺-dependent GPDH, this enzyme could form a G-3-P shuttle, as previously established in other eukaryotic organisms, and links cytosolic G-3-P metabolism to carbon source utilization and energy metabolism in plants.