Connective Auxin Transport in the Shoot Facilitates Communication between Shoot Apices

PLoS Biol. 2016 Apr 27;14(4):e1002446. doi: 10.1371/journal.pbio.1002446. eCollection 2016 Apr.


The bulk polar movement of the plant signaling molecule auxin through the stem is a long-recognized but poorly understood phenomenon. Here we show that the highly polar, high conductance polar auxin transport stream (PATS) is only part of a multimodal auxin transport network in the stem. The dynamics of auxin movement through stems are inconsistent with a single polar transport regime and instead suggest widespread low conductance, less polar auxin transport in the stem, which we term connective auxin transport (CAT). The bidirectional movement of auxin between the PATS and the surrounding tissues, mediated by CAT, can explain the complex auxin transport kinetics we observe. We show that the auxin efflux carriers PIN3, PIN4, and PIN7 are major contributors to this auxin transport connectivity and that their activity is important for communication between shoot apices in the regulation of shoot branching. We propose that the PATS provides a long-range, consolidated stream of information throughout the plant, while CAT acts locally, allowing tissues to modulate and be modulated by information in the PATS.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biological Transport
  • Indoleacetic Acids / metabolism*
  • Kinetics
  • Plant Proteins / metabolism
  • Plant Shoots / metabolism*
  • Plant Stems / metabolism


  • Indoleacetic Acids
  • Plant Proteins

Grants and funding

The funders of this research are the European Research Council,, N° 294514 – EnCoDe to OL; the Gatsby Charitable Foundation,, GAT3272C to OL; the Swedish Research Council,, to KL; the Swedish Governmental Agency for Innovation Systems,, to KL; the Natural Sciences and Engineering Research Council of Canada,, Discovery Grants to ES and scholarships to MGS. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.