XVI International Botanical Congess

We have focused on aldehyde oxidase (AO) for its possible involvement in biosynthesis of a plant hormone, indole-3-acetic acid (IAA). Three AO isoforms (AOa, b, g ) in Arabidopsis seedlings are homodimer and heterodimer composed of atAO-1 and atAO-2 gene products. To investigate the biochemical properties of the AOs, we produced recombinant proteins using yeast (Pichia pastoris) expression system. The mobility of the recombinant AOs after native PAGE was the same as that of AOs extracted from Arabidopsis seedlings. Furthermore substrate preferences of the recombinant AOs were very similar to those of Arabidopsis AOs. A low Km value (about 30mM) of atAO-1 products (AOa) against indole-3-acetaldehyde, a possible precursor of IAA, indicates that the AO has a role on IAA biosynthesis.