Adventitious roots are formed post-embryonically and can functionally replace the primary root system. This principle is exploited economically for the clonal propagation of many elite varieties in horticulture. For many crops, exposure to light inhibits rooting, whereas a dark incubation improves adventitious rooting. Despite its economic importance, little is known about the light regulation of adventitious rooting. In ongoing research, we found that the light signaling transcription factor HY5 plays a central role in this inhibition. To our surprise, this transcription factor seems to exert its inhibitory effect non-cell autonomously. This project sets out to resolve the underlying mechanism. On the one hand, I will test the involvement of symplastic transport, and its interplay with the adventitious rooting plant hormone auxin. On the other hand, I will perform a dedicated mutant screen to identify key elements of this non-cell autonomous signaling pathway. The results are pivotal to further our insight into the function of adventitious rooting and to develop tools that improve the rooting of shoots which is a vital component of clonal propagation of crops.