Connective Auxin Transport in the Shoot Facilitates Communication between Shoot Apices.
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.
Sainsbury Laboratory, University of Cambridge, Bateman Street, Cambridge, United Kingdom.
Tom
T
Bennett
Sainsbury Laboratory, University of Cambridge, Bateman Street, Cambridge, United Kingdom.
Geneviève
G
Hines
Sainsbury Laboratory, University of Cambridge, Bateman Street, Cambridge, United Kingdom.
Martin
M
van Rongen
Sainsbury Laboratory, University of Cambridge, Bateman Street, Cambridge, United Kingdom.
Tanya
http://orcid.org/0000-0001-7760-0950
T
Waldie
Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.
Megan G
MG
Sawchuk
Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.
Enrico
E
Scarpella
Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå, Sweden.
Karin
K
Ljung
Sainsbury Laboratory, University of Cambridge, Bateman Street, Cambridge, United Kingdom.
Ottoline
http://orcid.org/0000-0003-2161-3829
O
Leyser
D001692:Biological Transport; D007210:Indoleacetic Acids / Q000378:metabolism*; D007700:Kinetics; D010940:Plant Proteins / Q000378:metabolism; D018520:Plant Shoots / Q000378:metabolism*; D018547:Plant Stems / Q000378:metabolism
D007210:Indoleacetic Acids; D010940:Plant Proteins