15th International Conference on Arabidopsis Research - TAIR

T08-015
Non-Genomic Effect Of Auxin On Protein Trafficking
Tomasz Paciorek(1), Juergen Kleine-Vehn(1), Eva Zazimalova(2), Jan Petrasek(2),
David Morris(2), Neil Emans(3), Nadia Ruthardt(3), Gerd Juergens(1), Niko
Geldner(1), Jiri Friml(1)
1-Center for Plant Molecular Biology, University of Tubingen, 72076 Tubingen, Germany.
2-Institute of Experimental Botany, ASCR, 16502 Praha 6, Czech Republic.
3-Imaging and Cellular Biotechnology Group, RWTH, Aachen, Biology VII, 52074 Aachen, Germany.
The plant hormone auxin is one of the major regulators of plant development
implicated in variety of processes such as organ initiation, directional
growth (tropism), meristem activity and apical dominance. Auxin is distributed
throughout the plant by a polar auxin transport system, which requires
asymmetrically localized regulators from the PIN family. Using a specific
agent for inhibiting recycling of proteins in cells - brefeledine A- we show
that many plant plasma membrane proteins exhibit constitutive cycling. In
animals signalling molecules such as hormones can regulate protein activity
by modulating their constitutive cycling. We present data demonstrating that
auxin is able to modulate cycling of PIN proteins and thus regulate their levels
at the plasma membrane. This auxin effect is not dependent on protein and
mRNA synthesis and does not require known components of auxin signalling
pathway. Our data imply a model how auxin, by influencing protein trafficking,
can regulate various cellular processes including its own efflux.
T08 Long Distance Transport (Signals Including Silencing and Metabolites)
T08-016
Novel Feedback Regulations in Efflux-Dependent
Auxin Distribution
Jiri Friml(1), Anne Vieten(1), Michael. Sauer(1), Marta Michniewicz(1), Tomasz
Paciorek(1), Justyna Wisniewska(1), Gerd Juergens(1)
1-Zentrum für Molekularbiologie der Pflanzen, Universität Tübingen, Auf der Morgenstelle 3,
72076 Tübingen, Germany
More than a century of physiological work as well as recent contributions
from molecular genetics identified auxin as a prominent intercellular signal
in plants. Auxin distributed over long distances largely contributes to the
coordination and integration of growth at the whole plant level. On the other
hand, directional, active, cell-to-cell transport over short distances mediates
local, differential auxin distributions (gradients), required for various patterning
processes, including apical-basal axis formation and organogenesis.
Also growth responses to environmental cues such as light or gravity utilize
a similar mechanism involving auxin gradients. Differentially expressed auxin
transport regulators of the PIN family, each with specific polar, subcellular
localization form a network for auxin distribution and formation of these local
gradients. The activity of PIN proteins can be regulated at the single cell level
by changes in their vesicle trafficking-dependent polar targeting in response
to developmental and environmental cues. Thus, this auxin distribution
network, whose directional throughput is modulated by both endogenous and
exogenous signals, provides, by means of mediating auxin fluxes and creating
local gradients, a common mechanism for the plasticity and adaptability
of plant development. New insights in the complex regulatory mechanism for
controlling expression, polarity and activity of auxin efflux components will be
presented.
15 th <strong>International</strong> <strong>Conference</strong> on Arabidopsis Research 2004 · Berlin