title: Mechanical regulation of auxin-mediated growth.
abstract: BACKGROUND
  The phytohormone auxin is a primary regulator of growth and developmental pattern formation in plants. Auxin accumulates at specific sites (e.g., organ primordia) and induces localized growth within a tissue. Auxin also mediates developmental responses to intrinsic and external physical stimuli; however, exactly how mechanics influences auxin distribution is unknown.
  
  
  RESULTS
  Here we show that mechanical strain can regulate auxin transport and accumulation in the tomato shoot apex, where new leaves emerge and rapidly grow. Modification of turgor pressure, application of external force, and artificial growth induction collectively show that the amount and intracellular localization of the auxin efflux carrier PIN1 are sensitive to mechanical alterations. In general, the more strained the tissue was, the more PIN1 was present per cell and the higher the proportion localized to the plasma membrane. Modulation of the membrane properties alone was sufficient to explain most of the mechanical effects.
  
  
  CONCLUSIONS
  Our experiments support the hypothesis that the plasma membrane acts as a sensor of tissue mechanics that translates the cell wall strain into cellular responses, such as the intracellular localization of membrane-embedded proteins. One implication of this fundamental mechanism is the mechanical enhancement of auxin-mediated growth in young organ primordia. We propose that growth-induced mechanical strain upregulates PIN1 function and auxin accumulation, thereby promoting further growth, in a robust positive feedback loop.
authors: Institute of Plant Sciences, University of Bern, Altenbergrain 21, CH-3013 Bern, Switzerland.
authors: Naomi
authors: N
authors: Nakayama
authors: Richard S
authors: RS
authors: Smith
authors: Therese
authors: T
authors: Mandel
authors: Sarah
authors: S
authors: Robinson
authors: Seisuke
authors: S
authors: Kimura
authors: Arezki
authors: A
authors: Boudaoud
authors: Cris
authors: C
authors: Kuhlemeier
mesh_terms: D002462:Cell Membrane / Q000502:physiology; D003463:Cues; D025461:Feedback, Physiological; D007210:Indoleacetic Acids / Q000378:metabolism*; D018551:Solanum lycopersicum / Q000254:growth & development* / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D009997:Osmotic Pressure; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000254:growth & development / Q000378:metabolism; D013314:Stress, Mechanical; D015854:Up-Regulation
chemical_list: D007210:Indoleacetic Acids; D026901:Membrane Transport Proteins; D010940:Plant Proteins