The foraging capacity of plants mainly relies on their branched root systems. Lateral roots grow along the main axis at regular intervals to explore the biggest soil volume. Plants display remarkable cell fate reprogramming ability leading to post-embryonic lateral root development. In the model plant Arabidopsis thaliana, lateral roots only arise from the pericycle, a single cell layer surrounding the vascular bundle of the primary root. The aims of this project are to discover novel molecular determinants of pericycle cell fate reprogramming and to provide a revised model of early lateral root formation. The canonical ARF7/ARF19 plant hormone auxin signaling module is critical for controlling the very first steps of lateral root development. However the molecular determinants of such processes and how they are connected with other modules remain largely unknown. We carried out an EMS suppressor screen of the arf7arf19 mutant to identify molecular factors restoring lateral root organogenesis. The functions of the identified genes will be analyzed with our innovative live-imaging system to decipher the dynamics underlying the cell fate reprogramming with a precision never achieved before. Eventually, we expect to unravel the ARF7/ARF19 signaling cascade and how its connection with other modules. This project we will shed light on a largely uncharacterized phase during lateral root initiation and our findings will generate a robust framework to coordinate future research.