Intracellular trafficking and PIN-mediated cell polarity during tropic responses in plants

Subcellular trafficking and cell polarity are basic cellular processes crucial for plant development including tropisms - directional growth responses to environmental stimuli such as light or gravity. Tropisms involve auxin gradient across the stimulated organ that underlies the differential cell elongation and bending. The perception of light or gravity is followed by changes in the polar, cellular distribution of the PIN auxin transporters. Such re-specification of polar trafficking pathways is a part of the mechanism, by which plants adjust their phenotype to environmental changes. Recent genetic and biochemical studies provided the important insights into mechanisms of PIN polarization during tropisms. In this review, we summarize the present state of knowledge on dynamic PIN repolarization and its specific regulations during hypocotyl tropisms.