Auxins are a class of compounds that are key regulators of plant cell growth.
The exact mechanism of action of auxin-induced growth is unknown but involves many rapid cellular changes to prepare the cell to expand under turgor pressure. One of the effects of auxin is an increase in cell wall synthesis by stimulating the secretion of wall precursors. Molecular genetic evidence for an auxin receptor mediating wall synthesis or any other requisite aspect of auxin-induced growth is lacking. The effect of constitutive overexpression of maize ABP1 was examined using cell lines to avoid the problem of counterselection of ABP1 expression during whole plant regeneration after transformation. We found two lines overexpressing ABP1 and in both lines, cells are larger, contain thick cell walls, and have the morphology of transfer cells.