Abstract
Indole-3-acetic acid is the most abundant natural auxin. In Arabidopsis, several biosynthetic pathways of IAA via tryptophan have been studied hitherto, and indole derivatives have been proposed to be intermediate of the pathways. However, the mechanism of auxin biosynthesis remains elusive. It has not yet revealed as well, whether the proposed intermediates are IAA precursors. Using an auxin biosynthesis inhibitor, L-amino-oxyphenylpropionicacid (L-AOPP), we examined which putative intermediates are the precursors of IAA in Arabidopsis. The roots of seedling skewed to left and the elongation was inhibited by L-AOPP. Since IAA treatment recovered the skewing and elongation, we analyzed the root recovery to examine putative intermediate. To clarify further which putative auxin intermediate is converted to active auxin, putative intermediates were applied to seedlings, and we investigated induction of two auxin-inducible marker genes. The results suggest indole-3-pyruvic acid and some indole derivatives are potential IAA precursors. We will also report newly developed compounds and their inhibitory effects on IAA biosynthesis.
