PROTEIN-PHOSPHATASE INHIBITORS BLOCK ROOT HAIR-GROWTH AND ALTER CORTICAL CELL-SHAPE OF ARABIDOPSIS ROOTS

Emerging evidence suggests that protein phosphatases play an important role in the growth and development of higher plants. We report here on the effects of okadaic acid and calyculin-A, two specific and potent inhibitors of the type-1 and type-2A families of serine/threonine protein phosphatases, on the growth and development of Arabidopsis thaliana L. roots. Application of these drugs in nanomolar ranges arrested root hair growth, severely affected the shape of cells within the zone of elongation and inhibited root growth rates. Root hair elongation was inhibited by concentrations of okadaic acid and calyculin-A as low as 3nM. The pleiotropic effects of okadaic acid and calyculin-A point to multiple functions for type-1 and -2A protein phosphatases in controlling root growth and development.