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

Nat Cell Biol. 2006 Mar;8(3):249-56. doi: 10.1038/ncb1369. Epub 2006 Feb 19.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / growth & development
  • Arabidopsis / metabolism
  • Arabidopsis / physiology*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism
  • Arabidopsis Proteins / physiology*
  • Endosomes / metabolism
  • Gravitropism*
  • Hydrolysis
  • Indoleacetic Acids / metabolism*
  • Meristem / growth & development
  • Meristem / metabolism
  • Meristem / physiology
  • Plant Roots / growth & development
  • Plant Roots / metabolism
  • Plant Roots / physiology*
  • Promoter Regions, Genetic
  • Proteasome Endopeptidase Complex / metabolism
  • Protein Transport


  • Arabidopsis Proteins
  • Indoleacetic Acids
  • PIN2 protein, Arabidopsis
  • Proteasome Endopeptidase Complex