The PIN auxin efflux facilitator network controls growth and patterning in Arabidopsis roots

Abstract

Local accumulation of the plant growth regulator auxin mediates pattern formation in Arabidopsis roots and influences outgrowth and development of lateral root- and shoot-derived primordia. However, it has remained unclear how auxin can simultaneously regulate patterning and organ outgrowth and how its distribution is stabilized in a primordium-specific manner. Here we show that five PIN genes collectively control auxin distribution to regulate cell division and cell expansion in the primary root. Furthermore, the joint action of these genes has an important role in pattern formation by focusing the auxin maximum and restricting the expression domain of PLETHORA (PLT) genes, major determinants for root stem cell specification. In turn, PLT genes are required for PIN gene transcription to stabilize the auxin maximum at the distal root tip. Our data reveal an interaction network of auxin transport facilitators and root fate determinants that control patterning and growth of the root primordium.

Divide and conquer: development and cell cycle genes in plant transformation

“…The processes of plant transformation and regeneration from a transgenic cell can stall at several key points, including: (1) the acquisition of a stem-cell-like state in cells as they re-enter the cell cycle [7]; (2) progression between the G1 and S phases of the cycle [8,9] (Box 1); and (3) the differentiation of the transformed cell into a new embryo or meristem [10][11][12][13]. In this manuscript, we consider transformation to be the recovery of cells expressing a foreign gene for use as a selectable marker, and regeneration to be the organogenesis or embryogenesis from the genetically transformed cells.…”

Multiscale modelling of auxin transport in the plant-root elongation zone

“…We base our analysis on the cell-scale model of Swarup et al (2005), who consider auxin transport in the epidermal, cortical and endodermal layers of the root elongation zone with the distribution of efflux carriers reported by Blilou et al (2005) (see Fig. 1).…”

“…Following Swarup et al (2005), we have based our analysis on data from Blilou et al (2005) in which the elongation-zone cortical cells have efflux carriers on their rootward side; however, other sources suggest that efflux carriers are present instead on the shootward face of these cortical cells (Peer et al 2004). This is of particular interest as a recent experimental study (Rahman et al 2010) (focussing on the meristem) suggests that changing the direction of the cortical cells' efflux carriers significantly alters the auxin distribution and gravitropic response.…”

“…Considering the outer tissue layers in the root elongation zone, the epidermal cell membranes contain PIN1 and PIN2 carriers on their shootward face (upwards), whereas the endodermal cell membranes contain PIN1 carriers only, on their rootward face (downwards) (Blilou et al 2005). On the cortical cell membranes, the location of the PIN1 and PIN2 carriers is currently unclear, with some sources reporting a rootward location (Blilou et al 2005) and others a shootward one (Peer et al 2004). There are also spatial variations in the AUX1 influx carriers, these being present on all sides of the epidermal cell membranes, but not on the cortical and endodermal cell membranes (Swarup et al 2005).…”

“…There are also spatial variations in the AUX1 influx carriers, these being present on all sides of the epidermal cell membranes, but not on the cortical and endodermal cell membranes (Swarup et al 2005). With this spatial distribution, the carriers create a shootward auxin flux in the outer layers of the elongation zone that balances the rootward flux through the root centre (Blilou et al 2005;Friml et al 2002). In Arabidoposis thaliana, various mutants demonstrate the importance of the carriers; for example, both aux1 and pin2 mutants (which have dysfunctional AUX1 carriers and PIN2 carriers, respectively) have disrupted auxin transport and are agravitropic (Rashotte et al 2000;Swarup et al 2005).…”