ROOT PHOTOTROPISM 2 (RPT2) is a KAT1 potassium channel regulator required for its accumulation

In plants, inward rectifying potassium channels regulate potassium entry into guard cells and are a key factor controlling stomatal opening. KAT1 is a major inward rectifying potassium channel present in Arabidopsis thaliana guard cell membranes. The identification of regulators of channels like KAT1 is a promising approach for the development of strategies to improve plant drought tolerance. Using a high-throughput Split-ubiquitin screening in yeast, we identified RPT2 (ROOT PHOTOTROPISM 2) as a KAT1 interactor. Here, we present the results of the characterization of this interaction in yeast and plants. Importantly, we also observe increased KAT1-mediated currents in oocytes co-expressing RPT2, suggesting a functional link between the two proteins. Moreover, using stably transformed KAT1-YFP lines, we show that RPT2 is necessary for KAT1 protein accumulation in A. thaliana. Our data suggest an unexpected role for RPT2 in KAT1 post-translational regulation that may represent a novel connection between light signaling and potassium channel activity.