AUXIN-DEPENDENT CELL EXPANSION MEDIATED BY OVEREXPRESSED AUXIN-BINDING PROTEIN-1

To test the hypothesis that auxin-binding protein 1 (ABP1) is a recept or controlling auxin-mediated plant cell expansion, ABP1 complementary DNAs were expressed in a controllable fashion in tobacco plants and c onstitutively in maize cell lines. Induction of Arabidopsis ABP1 expre ssion in tobacco leaf strips resulted in an increased capacity for aux in-mediated cell expansion, whereas induction of ABP1 in intact plants resulted in leaves with a normal morphology, but larger cells. Simila rly, constitutive expression of maize ABP1 in maize cell lines conferr ed on them the capacity to respond to auxin by increasing cell size. T hese results support a role of ABP1 as an auxin receptor controlling p lant growth.