Because plant cells are immobile, they have to spatially control their divisions in order to establish the overall body plan of the plant. Control over the orientation of cell divisions is also crucial to generate new organs. This occurs via specialized divisions that are called formative divisions. These divisions are mostly asymmetric and lead to the formation of daughter cells with different cell fate. The very first step of lateral root formation requires two rounds of formative divisions and provides an excellent system to study this process. Lateral root formation is also developmentally important as it provides the plant with a complex network of root branches, indispensable for anchorage of the plant in the soil and efficient uptake of nutrients. We have recently shown that the two members of the alpha aurora kinase family play a key role in controlling the orientation of formative divisions throughout plant development. A double mutant in both alpha aurora kinases is macroscopically highly impaired in lateral root formation and contains defective orientations of formative divisions from embryogenesis onward. The aim of this project is to unravel the underlying mechanism-of-action whereby alpha aurora kinases control the orientation of formative divisions. We will analyze these defects using a marker-based approach and life cell imaging of the initial lateral root divisions. Secondly, we will identify substrates of alpha aurora kinases involved in the early developmental stages of lateral root development.