Plant development is characterized by a profound ability to regenerate and form tissues with new axes of polarity. An unsolved question concerns how the position within a tissue and cues from neighboring cells are integrated to specify the polarity of individual cells. The canalization hypothesis proposes a feedback effect of the
phytohormone auxin on the directionality of intercellular
auxin flow as a
means to
polarize tissues. Here we identify a cellular and molecular mechanism for canalization. Local
auxin application,
wounding, or
auxin accumulation during de novo
organ formation lead to
rearrangements in the
subcellular polar localization of PIN
auxin transport components. This
auxin effect on PIN polarity is cell-specific, does not depend on PIN transcription, and involves the Aux/IAA-ARF (indole-3-acetic acid-auxin
response factor)
signaling pathway. Our data suggest that
auxin acts as
polarizing cue, which links individual cell polarity with tissue and
organ polarity through control of PIN polar targeting. This feedback regulation provides a conceptual framework for
polarization during multiple regenerative and
patterning processes in plants.
