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Intracellular trafficking and proteolysis of the Arabidopsis auxin-efflux facilitator PIN2 are involved in root gravitropism

An Erratum to this article was published on 01 April 2006

Abstract

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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Figure 1: Analysis of PIN2 expression and subcellular localization in primary root meristems.
Figure 2: Control of proteasome activity and vesicular transport affects the steady-state levels of PIN2.
Figure 3: Gravi-stimulation mediates the establishment of a PIN2 gradient that is sensitive to inhibition of vesicular transport and depends on proteasome activity.
Figure 4: Intracellular distribution of PIN2:HA after gravi-stimulation in eir1–1 PIN2:PIN2:HA.
Figure 5: Analysis of wav6-52 roots.
Figure 6: Auxin promotes degradation of PIN2.
Figure 7: A diagram illustrating the role of PIN proteins in the regulation of root gravitropism.

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Acknowledgements

This work has been supported by grants from the Austrian Science Fund (FWF, P16311 and P15441) to C.L., by Volkswagenstiftung to J.F. and J.W, the Deutsche Forschungsgemeinschaft (SFB 446) to T.P., the Foundation for Polish Science to J.W., by the Institute of Applied Genetics and Cell Biology (MSM0021622415) and by the 'Hochschuljubiläumsfonds der Stadt Wien'. R.B. was a recipient of a TALENT fellowship from the Netherlands Organisation for Scientific Research. We would like to thank M. Bennett, L. Mach, E. Benková, M. Hauser, O. Mittelsten Scheid and K. Stockhammer for advice and valuable comments on the manuscript. L.A. thanks M. Guppy for good discussions. C.L. is indebted to J. Glössl for his ongoing and substantial support.

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Correspondence to Christian Luschnig.

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Abas, L., Benjamins, R., Malenica, N. et al. Intracellular trafficking and proteolysis of the Arabidopsis auxin-efflux facilitator PIN2 are involved in root gravitropism. Nat Cell Biol 8, 249–256 (2006). https://doi.org/10.1038/ncb1369

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