High impact information on ATPGP1

• PGP4, an ATP binding cassette P-glycoprotein, catalyzes auxin transport in Arabidopsis thaliana roots [1].
• More recently, members of the multidrug resistance P-glycoprotein (MDR/PGP) subfamily of ABC transporters have been shown to function in the transport of the phytohormone auxin in both monocots and dicots [1].
• Auxin transport activity was greatly impaired in atmdr1 and atmdr1 atpgp1 double mutant plants [2].
• The results indicate that these two MDR-like genes of Arabidopsis encode 1-naphthylphthalamic acid binding proteins that are required for normal auxin distribution and auxin-mediated development [2].
• Arabidopsis possesses several genes related to the multidrug resistance (MDR) genes of animals, one of which, AtMDR1, was shown to be induced by the hormone auxin [2].

Biological context of ATPGP1

• On the basis of these and other supporting data, we hypothesize that the hydrolysis of extracellular ATP by phosphatases and ATPases may be necessary for the resistance conferred by P-glycoprotein [3].
• The single gene mutation twd1-1 and double atpgp1-1/atpgp19-1 (atmdr1-1) mutants exhibit similar phenotypes including epinastic growth, reduced inflorescence size, and reduced polar auxin transport, suggesting that a functional TWD1-AtPGP1/AtPGP19 complex is required for proper plant development [4].
• Seven of the nine introns in the atpgp1 gene match introns in the mammalian mdr genes to within a few nucleotides, and the positions of these suggest that P-glycoprotein genes evolved by duplication and subsequent fusion of an intron-containing primordial gene prior to the evolutionary separation of plants and mammals [5].
• Here we examine the localization, activity, substrate specificity and inhibitor sensitivity of AtPGP1 [6].
• Consistent with the proposed role of AtMDR1 in basipetal auxin transport, we found that expression of the auxin responsive DR5::GUS reporter gene in the central elongation zone is significantly reduced in the atmdr1-100 mutant roots treated with 1-NAA at the root tips, compared to similarly treated wild-type plants [7].

Anatomical context of ATPGP1

• Unlike all other FKBPs, TWD1 is shown to be an integral membrane protein that colocalizes with its interacting partner AtPGP1 on the plasma membrane [4].
• Protoplasts from Arabidopsis pgp1 leaf mesophyll cells exhibit reduced efflux of natural and synthetic auxins with reduced sensitivity to auxin efflux inhibitors [6].

Associations of ATPGP1 with chemical compounds

• Constitutive overexpression of PGP1 and PGP19, but not TWD1, enhanced auxin export [8].

Physical interactions of ATPGP1

• Mapping of protein interaction domains shows that AtPGP1 surprisingly binds to the N-terminus of TWD1 harboring the cis-trans peptidyl-prolyl isomerase-like domain and not to the tetratrico-peptide repeat domain, which has been shown to mediate protein-protein interaction [4].

Other interactions of ATPGP1

• Employing an IAA-specific microelectrode demonstrated that IAA influx in the root elongation zone was perturbed and apically shifted in pgp1/pgp19 and twd1 roots [8].
• Our data suggest a novel mode of PGP regulation via FK506-binding protein-like immunophilins, implicating possible alternative strategies to overcome multidrug resistance [8].
• AtPGP1-mediated efflux is sensitive to auxin efflux and ABC transporter inhibitors [6].
• The plant multidrug resistance ABC transporter AtMRP5 is involved in guard cell hormonal signalling and water use [9].
• They included eight glycosylphosphatidylinositol-anchored proteins, several plasma membrane (PM) ATPases, multidrug resistance proteins, and proteins of the stomatin/prohibitin/hypersensitive response family, suggesting that the DRMs originated from PM domains [10].

References