Agriculture Reference
In-Depth Information
Auxin distributed over long distances largely contributes to the coordination and in-
tegration of growth and development at the level of the whole plant (it coordinates,
for example, initiation of side roots with growth of aerial tissues). Auxin distributed
over short distances by the polar transport system forms local gradients and thus me-
diates various patterning events. Furthermore, growth responses to external stimuli
such as light or gravity also utilize auxin as a signal and appear to use the same mech-
anism involving auxin gradients. These auxin gradients are established, maintained
and modulated by an active transport system, requiring regulators from the PIN fam-
ily. The activity of these auxin transport regulators can be modulated at the single
cell level by changes in their vesicle-trafficking-dependent polar targeting. Thus, the
directional throughput of this complex auxin distribution network can be modulated
by both endogenous and exogenous signals and provides, by means of mediating
auxin fluxes and creating local gradients, a common mechanism for the plasticity
and adaptability of plant development. Another level of control in the whole system
occurs downstream of the gradients where a large variety of mutually interacting
transcription activators and repressors provide the molecular basis for the multitude
of developmental programs, which can be initiated and controlled by auxin.
Acknowledgements
The authors acknowledge the support for their work from VolkswagenStiftung (J.F.)
and the Foundation for Polish Science (J.W.).
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