Regulating cytoplasmic oxalate homeostasis by Acyl activating enzyme3 is critical for plant Al tolerance.

Oxalic acid is the simplest of the dicarboxylic acids. In addition to its role in biological and metabolic processes, oxalate has been implicated in biotic and abiotic stresses. Being a strong chelator of Al, oxalate also has pivotal role in Al resistance mechanisms. However, we demonstrated that cytoplasmic oxalate accumulation is a critical event leading to root growth inhibition under Al stress. Transcriptome analysis from three crop plants identified Acyl Activating Enzyme3 (AAE3) genes to be upregulated by Al stress. These AAE3 proteins display high sequence identity to known AAE3 proteins, suggesting they are oxalyl-CoA synthetases specifically involved in oxalate degradation. However, phylogenetic analysis revealed divergence of AAE3 between monocots and dicots, pointing to the necessity for functional characterization of AAE3 proteins from other plant species with respect to Al stress.