Competitive canalization of PIN‐dependent auxin flow from axillary buds controls pea bud outgrowth

Abstract

SUMMARYShoot branching is one of the major determinants of plant architecture. Polar auxin transport in stems is necessary for the control of bud outgrowth by a dominant apex. Here, we show that following decapitation in pea (Pisum sativum L.), the axillary buds establish directional auxin export by subcellular polarization of PIN auxin transporters. Apical auxin application on the decapitated stem prevents this PIN polarization and canalization of laterally applied auxin. These results support a model in which the apical and lateral auxin sources compete for primary channels of auxin transport in the stem to control the outgrowth of axillary buds.

Auxin and Strigolactone Signaling Are Required for Modulation of Arabidopsis Shoot Branching by Nitrogen Supply

“…8). There is a substantial body of evidence that auxin in the main stem can inhibit bud activation by preventing auxin transport canalization out of buds, thereby preventing their growth (Li and Bangerth, 1999;Bennett et al, 2006;Prusinkiewicz et al, 2009;Balla et al, 2011;Shinohara et al, 2013). A rapid primary response to SLs is to reduce PIN1 accumulation at the plasma membrane, making canalization harder to achieve, thus reducing the number of buds that can activate (Crawford et al, 2010;Shinohara et al, 2013).…”

“…Auxin moving in the PATS does not enter the bud in appreciable amounts, indicating an indirect mode of action (Brown et al, 1979;Everat-Bourbouloux and Bonnemain, 1980;Prasad et al, 1993;Booker et al, 2003). There is good evidence to suggest that auxin transport in the main stem inhibits bud outgrowth by preventing axillary buds from establishing their own PATS out into the main stem (Li and Bangerth, 1999;Bennett et al, 2006;Prusinkiewicz et al, 2009;Balla et al, 2011;Shinohara et al, 2013). In addition, auxin may act by regulating the production of one or more second messengers in the stem, which move up into the bud to regulate bud activity locally and directly (Snow, 1937).…”

Cytokinins Are Initial Targets of Light in the Control of Bud Outgrowth

“…According to the auxin canalization model, auxin export from the axillary bud is necessary for bud outgrowth and is blocked, during apical dominance, by polar auxin transport in the stem (Li and Bangerth, 1999;Bennett et al, 2006;Balla et al, 2011). In the second messenger model, auxin acts indirectly in the control of bud outgrowth (i.e.…”

Using Arabidopsis to Study Shoot Branching in Biomass Willow

“…SLs, when directly applied to buds, can inhibit them (Gomez-Roldan et al, 2008;Brewer et al, 2009), evidence that contributed to the proposal that they may be acting as second messengers for auxin, relaying the inhibitory signal from the stem to buds. Alternatively, it has been proposed that PAT in the main stem can inhibit bud activity through influencing stem sink strength for auxin, thereby affecting the crucial establishment of auxin export from the bud and thus bud activation (Li and Bangerth, 1999;Bennett et al, 2006;Prusinkiewicz et al, 2009;Balla et al, 2011). SL action in this case would be through systemically dampening auxin transport canalization.…”

“…Auxin transport canalization involves an initial flow of auxin from a source to a sink, which both upregulates and polarizes auxin transport in the direction of this initial flow, gradually "canalizing" it into files of cells with high auxin transport capacity toward the sink (Sachs, 1981). This process strongly correlates with bud activation (Morris, 1977;Li and Bangerth, 1999;Prusinkiewicz et al, 2009;Balla et al, 2011).…”