Identification and characterization of 2-oxindole acetic acid synthetases in A. thaliana. (A) Simplified auxin metabolic pathway via IPyA. IAA-AA, indole-3-acetic acid-amino acid conjugate; IAA-Glc, indole-3-acetic acid-glucose; oxIAA-AA, 2-oxindole-3-acetic acid-amino acid conjugate; oxIAA-Glc, 2-oxindole-3-acetic acid-glucose; Trp, tryptophan. (B) Pictogram of conserved domains among OsDAO, AtDAO1, AtDAO2, and the nearest clade of a subfamily of 2-oxoglutarate oxygenases in Arabidopsis. (C) Enzyme assays of rDAO (rDAO1 and rDAO2) with buffer control, empty vector control, and heat-inactivated (boiled) enzyme control with IAA as a substrate. Data are means ± SD of at least independent 10 experiments.