Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 105, Issue 46, Pages 17812-17817Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0808073105
Keywords
gravitropism; polar auxin transport; posttranslational regulation; vesicle trafficking
Categories
Funding
- Research Foundation Flanders (Odysseus)
- European Molecular Biology Organization Young Investigator Program
- Fonds zur Forderung der Wissenschaftlichen Forschung [P19585]
- Vienna Science and Technology Fund [LS0535]
- Austrian Science Fund (FWF) [P19585] Funding Source: Austrian Science Fund (FWF)
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All eukaryotic cells present at the cell surface a specific set of plasma membrane proteins that modulate responses to internal and external cues and whose activity is also regulated by protein degradation. We characterized the lytic vacuole-dependent degradation of membrane proteins in Arabidopsis thaliana by means of in vivo visualization of vacuolar targeting combined with quantitative protein analysis. We show that the vacuolar targeting pathway is used by multiple cargos including PIN-FORMED (PIN) efflux carriers for the phytohormone auxin. In vivo visualization of PIN2 vacuolar targeting revealed its differential degradation in response to environmental signals, such as gravity. In contrast to polar PIN delivery to the basal plasma membrane, which depends on the vesicle trafficking regulator ARF-GEF GNOM, PIN sorting to the lytic vacuolar pathway requires additional brefeldin A-sensitive ARF-GEF activity. Furthermore, we identified putative retromer components SORTING NEXIN1 (SNX1) and VACUOLAR PROTEIN SORTING29 (VPS29) as important factors in this pathway and propose that the retromer complex acts to retrieve PIN proteins from a late/pre-vacuolar compartment back to the recycling pathways. Our data suggest that ARF GEF- and retromer-dependent processes regulate PIN sorting to the vacuole in an antagonistic manner and illustrate instrumentalization of this mechanism for fine-tuning the auxin fluxes during gravitropic response.
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