The phytohormone auxin triggers transcriptional reprogramming through a well-characterized perception machinery in the nucleus. By contrast, mechanisms that underlie fast effects of auxin, such as the regulation of ion fluxes, rapid phosphorylation of proteins or auxin feedback on its transport, remain unclear1-3. Whether auxin-binding protein 1 (ABP1) is an auxin receptor has been a source of debate for decades1,4. Here we show that a fraction of Arabidopsis thaliana ABP1 is secreted and binds auxin specifically at an acidic pH that is typical of the apoplast. ABP1 and its plasma-membrane-localized partner, transmembrane kinase 1 (TMK1), are required for the auxin-induced ultrafast global phospho-response and for downstream processes that include the activation of H+-ATPase and accelerated cytoplasmic streaming. abp1 and tmk mutants cannot establish auxin-transporting channels and show defective auxin-induced vasculature formation and regeneration. An ABP1(M2X) variant that lacks the capacity to bind auxin is unable to complement these defects in abp1 mutants. These data indicate that ABP1 is the auxin receptor for TMK1-based cell-surface signalling, which mediates the global phospho-response and auxin canalization.

• MeSH
• Arabidopsis * genetics   metabolism   MeSH
• Phosphorylation MeSH
• Hydrogen-Ion Concentration MeSH
• Indoleacetic Acids * metabolism   MeSH
• Mutation MeSH
• Protein Serine-Threonine Kinases * genetics   metabolism   MeSH
• Arabidopsis Proteins * genetics   metabolism   MeSH
• Proton-Translocating ATPases metabolism   MeSH
• Cytoplasmic Streaming MeSH
• Plant Growth Regulators metabolism   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• AT1G66150 protein, Arabidopsis MeSH Browser
• auxin-binding protein 1 MeSH Browser
• Indoleacetic Acids * MeSH
• Protein Serine-Threonine Kinases * MeSH
• Arabidopsis Proteins * MeSH
• Proton-Translocating ATPases MeSH
• Plant Growth Regulators MeSH

Plants, in contrast to animals, are unique in their capacity to postembryonically develop new organs due to the activity of stem cell populations, located in specialized tissues called meristems. Above ground, the shoot apical meristem generates aerial organs and tissues throughout plant life. It is well established that auxin plays a central role in the functioning of the shoot apical meristem. Auxin distribution in the meristem is not uniform and depends on the interplay between biosynthesis, transport, and degradation. Auxin maxima and minima are created, and result in transcriptional outputs that drive the development of new organs and contribute to meristem maintenance. To uncover and understand complex signaling networks such as the one regulating auxin responses in the shoot apical meristem remains a challenge. Here, we will discuss our current understanding and point to important research directions for the future.

• MeSH
• Indoleacetic Acids * metabolism   MeSH
• Meristem * physiology   MeSH
• Gene Expression Regulation, Plant MeSH
• Signal Transduction physiology   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH
• Names of Substances
• Indoleacetic Acids * MeSH

• Publication type
• Journal Article MeSH