We study polar growth in Arabidopsis root hairs and aim to uncover mechanisms that enable rapid modulation of growth rates under changing environments. Project A14 will investigate interactions between ROP-GTPases and the WAVE Regulatory Complex (WRC) and their spatial organization into plasma membrane nanodomains to understand their role in organizing apical F-actin and guiding vesicle fusion. A combination of cell biology and biochemistry will address: (1) the lateral organization and ultrastructure of growing and non-growing hair apices using live imaging and electron tomography, (2) the formation and composition of ROP nanodomains within the root hair initiation domain using proteomics and lipidomics, and (3) the regulatory function of the lateral sorting into nanodomains through optogenetic manipulation.