Plasma membrane domain patterning and self-reinforcing polarity in Arabidopsis (Devel. Cell)

Phosphoinositides (PIs) are specialized membrane lipids that contribute to membrane nanodomains, which affect protein localizations and vesicle trafficking. Previous studies have implicated PIs in the polar localization of auxin-transporter PIN proteins, and, in roots, the PIN-regulators PAX and BRX. Here, Marhava et al. show that BRX and PAX recruit phosphatidylinositol-4-phosphate 5-kinases [PIP5Ks; kinases that convert PI4P to PI(4,5)P₂] to the rootward plasma membrane, thus altering the abundance of PI(4,5)P₂. Because PI(4,5)P₂ promotes PAX plasma membrane association, local PI(4,5)P₂ biosynthesis reinforces the polarity of all three components. Furthermore, elevated PI(4,5)P₂ promotes PIN endocytosis. Thus, BRX, PAX, and PIP5Ks constitute a self-reinforcing polarity module. (Summary by Mary Williams) Devel. Cell 10.1016/j.devcel.2019.11.015