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Cellular efflux of auxin catalyzed by the Arabidopsis MDR/PGP transporter AtPGP1
Author(s) -
Geisler Markus,
Blakeslee Joshua J.,
Bouchard Rodolphe,
Lee Ok Ran,
Vincenzetti Vincent,
Bandyopadhyay Anindita,
Titapiwatanakun Boosaree,
Peer Wendy Ann,
Bailly Aurèlien,
Richards Elizabeth L.,
Ejendal Karin F. K.,
Smith Aaron P.,
Baroux Célia,
Grossniklaus Ueli,
Müller Axel,
Hrycyna Christine A.,
Dudler Robert,
Murphy Angus S.,
Martinoia Enrico
Publication year - 2005
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2005.02519.x
Subject(s) - auxin , polar auxin transport , efflux , arabidopsis , biochemistry , atp binding cassette transporter , biology , microbiology and biotechnology , transporter , arabidopsis thaliana , chemistry , gene , mutant
Summary Directional transport of the phytohormone auxin is required for the establishment and maintenance of plant polarity, but the underlying molecular mechanisms have not been fully elucidated. Plant homologs of human multiple drug resistance/P‐glycoproteins (MDR/PGPs) have been implicated in auxin transport, as defects in MDR1 ( AtPGP19 ) and AtPGP1 result in reductions of growth and auxin transport in Arabidopsis ( atpgp1 , atpgp19 ), maize ( brachytic2 ) and sorghum ( dwarf3 ). Here we examine the localization, activity, substrate specificity and inhibitor sensitivity of AtPGP1. AtPGP1 exhibits non‐polar plasma membrane localization at the shoot and root apices, as well as polar localization above the root apex. Protoplasts from Arabidopsis pgp1 leaf mesophyll cells exhibit reduced efflux of natural and synthetic auxins with reduced sensitivity to auxin efflux inhibitors. Expression of AtPGP1 in yeast and in the standard mammalian expression system used to analyze human MDR‐type proteins results in enhanced efflux of indole‐3‐acetic acid (IAA) and the synthetic auxin 1‐naphthalene acetic acid (1‐NAA), but not the inactive auxin 2‐NAA. AtPGP1‐mediated efflux is sensitive to auxin efflux and ABC transporter inhibitors. As is seen in planta , AtPGP1 also appears to mediate some efflux of IAA oxidative breakdown products associated with apical sites of high auxin accumulation. However, unlike what is seen in planta , some additional transport of the benzoic acid is observed in yeast and mammalian cells expressing AtPGP1 , suggesting that other factors present in plant tissues confer enhanced auxin specificity to PGP‐mediated transport.