Characterization of a dwarf mutant allele of Arabidopsis MDR-like ABC transporter AtPGP1 gene.

Asymmetric auxin distribution caused by polar auxin transport (PAT) regulates many plant developmental and physiological processes. Plant two closely ABC (ATP-binding cassette) transporter, AtPGP1 and AtPGP19 (AtMDR1), have been implicated in auxin transport. However, unlike atpgp19 mutant and atpgp1 atmdr1 double mutant show decreased apical dominance, reduced growth, and impaired basipetal auxin transport, atpgp1 mutant exhibit no significant difference from wild type. We report a new allele of atpgp1 mutants, designated as atpgp1-2, which showed shorter hypocotyl and dwarf phenotype under long-day condition. Auxin transport activity was greatly impaired and NPA-sensitivity was decreased in the mutant. Moreover, we detected transcript in the atpgp1 mutants reported previously, but not in atpgp1-2. These results suggest a direct involvement of AtPGP1 in auxin transport processes controlling plant growth.