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Regulation of AtPGP1-mediated auxin transport by phosphorylation

English title Regulation of AtPGP1-mediated auxin transport by phosphorylation
Applicant Geisler Markus
Number 111912
Funding scheme Project funding
Research institution Molekulare Pflanzenphysiologie Institut für Pflanzenbiologie Universität Zürich
Institution of higher education University of Zurich - ZH
Main discipline Botany
Start/End 01.07.2006 - 30.06.2009
Approved amount 186'071.00
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Keywords (6)

auxin; plant hormones; p-glycoprotein; ABC transporter; phosphorylation; regulation

Lay Summary (English)

Lead
Lay summary
Auxin - principally indole-3-acetic acid (IAA) - has proven as unique signaling molecule virtually controlling all plant developmental processes. Recent research has concentrated on the fascinating feature auxin being transported in a directed or polar fashion. Polar auxin transport (PAT) is regulated at the cellular level and is apparently both a product and determinant of cellular polarity. Auxin unloading is thought to be mediated by protein complexes that are characterized by members of the p-plycoprotein (PGP) and pin-shaped (PIN) protein families.
The establishment of auxin gradients is controlled by reversible protein phosphorylation, however, the individual targets of protein kinases and phosphatases are unknown. Several lines of evidence point to components of auxin efflux complexes and/or NPA-binding proteins as targets of phosphorylation. While PIN proteins are apparently unlikely candidates two findings favor PGP as targets: PGP1 has been shown recently to catalyze the primary active export of auxin and to be modulated by NPA binding.
Moreover, in a recent phosphoproteomic approach, PGP1 has been demonstrated to be phosphorylated in conserved phosphorylation sites in a so-called regulatory linker domain. This domain is known to modulate the activity mammalian PGPs by phosphorylation via PKC.
In this project we envisage to demonstrate that PGP1-mediated auxin transport is modulated by phosphorylation in its regulatory linker domain.Phosphoproteomic data, a yeast-based mutant screen, and site directed mutagenesis will be used to determine the impact of phosphorylation on transport activity. The outcome of the yeast work will allow us to engineer relevant phosphorylation sites in the linker domain of PGP1 that alter protein activity and/or location. Additionally, TILLING technology will be used to identify relevant point mutations in the linker domain.
Finally, in order to identify plant-borne kinases/phosphatases responsible for (de)phosphorylation of PGP1, a classical yeast two-hybrid screen using the linker domain as bait will be carried out. In an inverse approach, the phosphorylation status of PGP1 will be upon will be determined biochemically and by mass spectrometry applying physiological, chemical and genetic tools.
The outcome should provide a deep insight into the regulation of auxin transport via PGPs and the establishment of local auxin gradients controlling virtually all steps of plant development. Transfer of this knowledge might later on open new strategies for the directed genetic or chemical manipulation of plant development.
Direct link to Lay Summary Last update: 21.02.2013

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