In contrast to animals, plants show an indeterminate mode of development, where organ formation mainly occurs post-embryonically and is highly adaptive to the environment. The above ground organs of higher plants are generated through the activity of stem cell centres, the so-called shoot meristems. To ensure correct growth, the plant must tightly balance the ratio between pluripotent stem cells and differentiating cells, which are consumed by organ formation. This requires constant intercellular communication achieved by complex interactions of numerous signalling molecules. In addition to this short range communication in the meristem plants also developed sophisticated long range signals to communicate between meristems to concert overall growth. We are interested in the molecular nature and function of these signals, which in some respect represent an analogous communication system to the neuronal network of animals.

Apart from gaining essential new insights in the molecular control of plant growth the knowledge should be applicable to improve the production of food and renewable energy resources. Shoot system architecture affects light harvesting potential, the synchrony of flowering and seed set, and the number of flowers and seeds per plant. Thus, changes in architectural characteristics have been, and continue to be central breeding targets in agriculture, horticulture and forestry.

We developed an highly interdisciplinary approach to define novel pathways and mechanisms, which control the growth rate and architecture of shoots (Fig. 1). Besides modern functional genomic tools to identify and characterize genes of interest, we perform phenotypic and reporter-based screens to find small molecules affecting these processes. Those compounds are then used to determine their molecular targets in the plant by biochemical and genetic means. Currently we are focusing on the following projects: 1) the AMP1 pathway, which controls stem cell pool size and leaf initiation rate. 2) the strigolactone pathway, which regulates the outgrowth of lateral branches (Fig. 2).