Nature Cell Biology 8, 249 - 256 (2006)
Published online: 19 February 2006; | doi:10.1038/ncb1369
There is an Erratum (March 2006) associated with this Letter.
Intracellular trafficking and proteolysis of the Arabidopsis auxin-efflux facilitator PIN2 are involved in root gravitropismLindy Abas1, 5, René Benjamins1, 5, Nenad Malenica1, 5, Tomasz Paciorek2, Justyna Wi niewska2, 3, Jeanette C. Moulinier–Anzola1, Tobias Sieberer1, Ji í Friml2, 4
& Christian Luschnig11
Institute for Applied Genetics and Cell Biology, University of Natural Resources and Applied Life Sciences – BOKU, Muthgasse 18, A-1190 Wien, Austria. 2
Center for Molecular Biology of Plants, University Tübingen, Auf der Morgenstelle 3, D-72076 Tübingen, Germany. 3
Department of Biotechnology, Institute of General and Molecular Biology, 87–100 Torun, Poland. 4
Masaryk University, Department of Functional Genomics and Proteomics, Laboratory of Molecular Plant Physiology, Kamenice 5, CZ-625 00, Brno, Czech Republic. 5
These authors contributed equally to this work.
Correspondence should be addressed to Christian Luschnig christian.luschnig@boku.ac.at Root gravitropism describes the orientation of root growth along the gravity vector and is mediated by differential cell elongation in the root meristem. This response requires the coordinated, asymmetric distribution of the phytohormone auxin within the root meristem, and depends on the concerted activities of PIN proteins and AUX1 — members of the auxin transport pathway. Here, we show that intracellular trafficking and proteasome activity combine to control PIN2 degradation during root gravitropism. Following gravi-stimulation, proteasome-dependent variations in PIN2 localization and degradation at the upper and lower sides of the root result in asymmetric distribution of PIN2. Ubiquitination of PIN2 occurs in a proteasome-dependent manner, indicating that the proteasome is involved in the control of PIN2 turnover. Stabilization of PIN2 affects its abundance and distribution, and leads to defects in auxin distribution and gravitropic responses. We describe the effects of auxin on PIN2 localization and protein levels, indicating that redistribution of auxin during the gravitropic response may be involved in the regulation of PIN2 protein.
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