Go polar: Regulation of Rho GTPases by ARO proteins (Nature Plants)

Polar cell growth is a key feature in plant organs like root hairs, trichomes and pollen tubes. Kulich and co-workers have identified novel regulatory elements governing the polar growth of root hairs and trichomes in Arabidopsis thaliana. Studying a group of proteins named ARMADILLO REPEAT ONLY (ARO), the authors found them to specifically localize to and be essential for the growth of polar ends of root hairs and leaf trichomes. Redundancy in function of multiple AROs was evident, as only the double and triple mutants displayed severe phenotypes. Analyzing potential interactors of AROs, the authors found them to redundantly interact with another group of proteins known as RENGAPs (RENs), which are known regulators of Rho of plant (ROP) GTPases. Further analyses showed AROs to interact with RENs as well as GTP-bound, active ROPs, and also that AROs are essential for the localization of RENs and ROPs to polar ends to ensure polar growth of root hairs. Thus, this study highlights a group of proteins that act as central regulators in driving polar growth of plant cells. (Summary by Pavithran Narayanan @pavi_narayanan) Nature Plants 10.1038/s41477-020-00781-1