dr. W (Wouter) Kohlen

Plants have the remarkable capability of continuously re-activating organogenesis throughout their life. Because of this, the full form of the plant body is not predefined during embryogenesis. This plasticity is achieved post-embryonically through the formation of new axes of growth: so-called secondary meristems. These meristems harbor plant stem cells, which are undifferentiated cells that provide a steady supply of organ precursor cells. As a plant physiologist I am mainly interested in the mechanisms controlling a plants ability to initiate such meristems, and what defines that some tissues are able to do this whereas other tissues cannot.

The main mechanism by which secondary meristems are initiated is through the activation of lateral organ founder cells. A key feature of this type of meristem initiation is that cells are set aside and retain a stem cell-like identity until they are activated later to form a new meristem. However, in some cases an even greater form of plasticity is achieved: so called de novo meristem initiation. In contrast to founder cell initiation, these meristems are initiated from fully differentiated cells. It has been postulated that these cells revert to an undifferentiated state in order to re-differentiate into a meristem.

Although shoot branching is crucial to determine the overall plant architecture in response to the environment, in agriculture this is often regarded as a problem. Much of a plant’s resources is invested in the formation of axillary buds and their outgrowth, thus reducing yield. However, complete removal of buds is also not desired, as this would create the risk of plant loss due to shoot apical meristem damaging. A combination of genetic removal of buds with the ability to induce de novo meristems when needed would be preferred. As such, understanding - and ultimately controlling – de novo axillary meristem formation would contribute considerably to the improvement of agricultural practice. Detailed knowledge on how axillary meristems are formed is therefore crucial. My research focusses on understanding how de novo meristem initiation in plants is accomplished. In a sense, to control de novo meristem initiation is to control plant architecture.