Minisymposium 13: Membrane Transport
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M1301: Immunophilin-like TWISTED DWARF1 functions as a sensor in p-glycoprotein mediated auxin transport
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Presenter: |
Geisler, Markus Contact Presenter | Authors | Bailly, Aurelien (A) Bouchard, Rodolphe (A) Vincenzetti, Vincent (A) Mancuso, Stefano (B) Murphy, Angus (C) Schulz, Burkhard (C) Martinoia, Enrico (A) Geisler, Markus (A) | | Affiliations: |
(A): University of Zurich, Institute of Plant Biology, Zurich, Switzerland
(B): University of Firenze, Department of Horticulture, Firenze, Italy
(C): Purdue University, Department of Horticulture, West Lafayette, USA
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Previously, the immunophilin-like protein TWD1 (TWISTED DWARF1/FKBP42) from Arabidopsis has been demonstrated to physically interact with MDR/PGP ABC transporters PGP1 and PGP19 (AtMDR1). Phenotypic and biochemical analysis of overlapping dwarf phenotypes of pgp1 pgp19 and of twd1 suggested a positive regulatory role of TWD1 on PGP-mediated auxin export activities.
Here we verify the regulatory effect of TWD1 on PGP-mediated auxin efflux by using plant and yeast auxin transport systems. Secondary effects due to delocalization of auxin efflux complex components were excluded. Using an IAA-specific microelectrode we demonstrate that IAA influx in the root elongation zone is reduced and shifted apically in pgp and twd1 mutant roots. As a consequence, pgp1 pgp19 and twd1 mutant roots reveal strongly elevated levels of free IAA in the elongation zone and above. Moreover, yeast and plant transport data suggest that TWD1 defines not only transport activities but also substrate specificities.
Using a yeast-based BRET system we show that TWD1-PGP1 interaction is specifically disrupted by flavonols, known to inhibit plant and mammalian PGPs as well as auxin transport. Surprisingly, flavonol-mediated alterations in auxin transport are dependent on co-expression with TWD1 while flavonols have only a mild inhibitory effect on PGP1 alone.
In summary, we demonstrate a novel mode of MDR/PGP regulation via FKBP-like immunophilins functioning both as sensor and regulator of auxin transport.
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