A PINOID-Dependent Binary Switch in Apical-Basal PIN Polar Targeting Directs Auxin Efflux

TLDR

Auxin accumulates locally via polar transport, providing positional cues for plant patterning, and this directional flow relies on the polar subcellular localization of PIN auxin efflux regulators. A PINOID-dependent binary switch controls PIN polarity, shifting PIN localization from basal to apical when PINOID is overexpressed and from apical to basal when PINOID is lost, thereby disrupting auxin gradients and causing defects in embryo, root, and organ development.

Abstract

Polar transport-dependent local accumulation of auxin provides positional cues for multiple plant patterning processes. This directional auxin flow depends on the polar subcellular localization of the PIN auxin efflux regulators. Overexpression of the PINOID protein kinase induces a basal-to-apical shift in PIN localization, resulting in the loss of auxin gradients and strong defects in embryo and seedling roots. Conversely, pid loss of function induces an apical-to-basal shift in PIN1 polar targeting at the inflorescence apex, accompanied by defective organogenesis. Our results show that a PINOID-dependent binary switch controls PIN polarity and mediates changes in auxin flow to create local gradients for patterning processes.