title: Single-cell-based system to monitor carrier driven cellular auxin homeostasis.
abstract: BACKGROUND
  Abundance and distribution of the plant hormone auxin play important roles in plant development. Besides other metabolic processes, various auxin carriers control the cellular level of active auxin and, hence, are major regulators of cellular auxin homeostasis. Despite the developmental importance of auxin transporters, a simple medium-to-high throughput approach to assess carrier activities is still missing. Here we show that carrier driven depletion of cellular auxin correlates with reduced nuclear auxin signaling in tobacco Bright Yellow-2 (BY-2) cell cultures.
  
  
  RESULTS
  We developed an easy to use transient single-cell-based system to detect carrier activity. We use the relative changes in signaling output of the auxin responsive promoter element DR5 to indirectly visualize auxin carrier activity. The feasibility of the transient approach was demonstrated by pharmacological and genetic interference with auxin signaling and transport. As a proof of concept, we provide visual evidence that the prominent auxin transport proteins PIN-FORMED (PIN)2 and PIN5 regulate cellular auxin homeostasis at the plasma membrane and endoplasmic reticulum (ER), respectively. Our data suggest that PIN2 and PIN5 have different sensitivities to the auxin transport inhibitor 1-naphthylphthalamic acid (NPA). Also the putative PIN-LIKES (PILS) auxin carrier activity at the ER is insensitive to NPA in our system, indicating that NPA blocks intercellular, but not intracellular auxin transport.
  
  
  CONCLUSIONS
  This single-cell-based system is a useful tool by which the activity of putative auxin carriers, such as PINs, PILS and WALLS ARE THIN1 (WAT1), can be indirectly visualized in a medium-to-high throughput manner. Moreover, our single cell system might be useful to investigate also other hormonal signaling pathways, such as cytokinin.
authors: Department of Plant Systems Biology, VIB and Department of Plant Biotechnology and Genetics, Ghent University, 9052, Gent, Belgium.
authors: Elke
authors: E
authors: Barbez
authors: Martina
authors: M
authors: Laňková
authors: Markéta
authors: M
authors: Pařezová
authors: Alexis
authors: A
authors: Maizel
authors: Eva
authors: E
authors: Zažímalová
authors: Jan
authors: J
authors: Petrášek
authors: Jiří
authors: J
authors: Friml
authors: Jürgen
authors: J
authors: Kleine-Vehn
mesh_terms: D001692:Biological Transport / Q000235:genetics / Q000502:physiology; D007210:Indoleacetic Acids / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D014026:Nicotiana / Q000378:metabolism
chemical_list: D007210:Indoleacetic Acids; D010940:Plant Proteins
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