Post-transcriptional control of the Arabidopsis auxin efflux carrier EIR1 requires AXR1

Curr Biol. 2000 Dec 14-28;10(24):1595-8. doi: 10.1016/s0960-9822(00)00861-7.


The auxin efflux carrier EIR1 (also known as AGR and AtPIN2) is a key mediator of the response of Arabidopsis roots to gravity [1,2]. This response is thought to require the establishment of a transient auxin gradient in the root meristem, resulting in differential cell elongation [3]. Recent reports suggest that EIR1 is essential for the asymmetric distribution of auxin in the root meristem [4-7], but the regulatory aspects of this process are still not fully understood. Here, we studied the regulation of EIR1 in Arabidopsis using two reporters: one was a translational fusion that contained the entire EIR1 coding sequence, and the other a transcriptional fusion that had no EIR1 coding sequence. We found that EIR1 is controlled at the post-transcriptional level. The translational fusion was unstable in response to changes in auxin homeostasis, and was destabilized by cycloheximide. In contrast, the protein was stabilized in the axr1-3 mutant, which is auxin resistant and defective in auxin responses such as root gravitropism [8,9]. AXR1 is thought to participate in ubiquitin-mediated control of protein stability [10-12]. The dependence of EIR1 reporter expression on auxin concentrations and AXR1 suggests that auxin transport is regulated through a feedback regulatory loop that affects protein stability in response to auxin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / genetics
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins*
  • Blotting, Northern
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Genes, Plant
  • Genes, Reporter / genetics*
  • Growth Substances*
  • Immunohistochemistry
  • Indoleacetic Acids / metabolism*
  • Membrane Transport Proteins*
  • Meristem / anatomy & histology
  • Meristem / physiology
  • Plant Proteins / genetics
  • Plant Proteins / metabolism*
  • Plants, Genetically Modified
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism


  • AXR1 protein, Arabidopsis
  • Arabidopsis Proteins
  • Carrier Proteins
  • Growth Substances
  • Indoleacetic Acids
  • Membrane Transport Proteins
  • PIN2 protein, Arabidopsis
  • Plant Proteins
  • Recombinant Fusion Proteins