ZHANG, J., NODZYNSKI, T., PĚNČÍK, Aleš, ROLČÍK, Jakub, FRIML, J. PIN phosphorylation is sufficient to mediate PIN polarity and direct auxin transport. Proceedings of the National Academy of Sciences of the United States of America. 2010, 107(2), 918-922. ISSN 0027-8424. E-ISSN 1091-6490

The plant hormone auxin plays a crucial role in regulating plant development and plant architecture. The directional auxin distribution within tissues depends on PIN transporters that are polarly localized on the plasma membrane. The PIN polarity and the resulting auxin flow directionality are mediated by the antagonistic actions of PINOID kinase and protein phosphatase 2A. However, the contribution of the PIN phosphorylation to the polar PIN sorting is still unclear. Here, we identified an evolutionarily conserved phosphorylation site within the central hydrophilic loop of PIN proteins that is important for the apical and basal polar PIN localizations. Inactivation of the phosphorylation site in PIN1(Ala) resulted in a predominantly basal targeting and increased the auxin flow to the root tip. In contrast, the outcome of the phosphomimic PIN1(Asp) manipulation was a constitutive, PINOID-independent apical targeting of PIN1 and an increased auxin flow in the opposite direction.