MDR‐like ABC transporter AtPGP4 is involved in auxin‐mediated lateral root and root hair development

Here we show that related isoform AtPGP4 is expressed predominantly during early root development. AtPGP4 loss‐of‐function plants reveal enhanced lateral root initiation and root hair lengths both known to be under the control of auxin. Further, atpgp4 plants show altered sensitivities toward auxin and the auxin transport inhibitor, NPA. Finally, mutant roots reveal elevated free auxin levels and reduced auxin transport capacities. These results together with yeast growth assays suggest a direct involvement of AtPGP4 in auxin transport processes controlling lateral root and root hair development.