Homayouni, A.; Damodaran, S.; Schreiber, K.; Michniewicz, M.; Gunther, L.; Strader, L. C.

Proper spatiotemporal distribution of the phytohormone auxin throughout plant tissues mediates a variety of developmental processes. Auxin levels are tightly regulated via de novo synthesis, transport, and conversion from its conjugated forms and precursors. These levels can be regulated through conversion of the auxin precursor, indole 3-butyric acid (IBA), into the active auxin, indole-3-acetic acid (IAA), in a peroxisomal {beta}-oxidation process. Defects in IBA-to-IAA conversion cause multiple developmental defects in Arabidopsis, demonstrating IBA-derived IAA is physiologically important to the active auxin pool. Similar to IAA, transport of IBA modulates development. However, the mechanisms governing transport of this molecule remain largely unknown. Here, we identify a mutation in the ABCC10 gene of Arabidopsis that suppresses the abcg36 hypersensitivity to IBA and its synthetic analog, 2,4-dichlorophenoxy butyric acid (2,4-DB) and the abcg36 hyperaccumulation of [3H]-IBA. We found that ABCC10 acts as a direct vacuolar transporter of IBA. Further, ABCC10 is necessary for proper development of the root apical meristem and leaf tissue. Our findings uncover a previously uncharacterized method of IBA transport that regulates aspects of plant development.