Control of dissected leaf form in the Arabidopsis thaliana relative Cardamine hirsuta

A key problem in biology is to understand how different organisms come to have different forms. In plants this variation in form is obvious in the many different leaf shapes one sees during a walk in the park. Leaves are also interesting to study because they play a key role in the food chain being the main photosynthetic organs of land plants and thus responsible for CO2 fixation in terrestrial ecosystems. For these reasons, understanding how diversity in leaf form in generated is of considerable interest to scientists. To study this problem we work with the hairy bittercress (Cardamine hirsuta), which is a plant that has leaves fully subdivided into small leaflets. The presence of leaflets makes this plant very different to its close relative the thale cress (Arabidopsis thaliana), which has entire, undivided leaves. We already know a lot about how entire leaf shape is produced in A.thaliana because it is easy to grow and do experiments with. Hairy bittercress is also very easy to work with in the lab, so we will use it to understand how leaflets are produced, what controls their number, and ultimately why this plant makes leaflets whereas its relative the thale cress does not.

We will study mechanisms controlling leaflet development and natural variation in leaflet number in Cardamine hirsuta, which is a dissected leaf relative of the model organism Arabidopsis thaliana. We will do this by using clonal analysis to directly examine which cells within the leaf are responsible for leaflet production and by investigating whether regulated cell division activity controls leaflet development. We will also map genes controlling natural variation in leaflet number by performing QTL analysis in natural variants of C. hirsuta. We will study whether these genes, act to change the position, timing or rate of leaflet initiation. This work will help understand how the reconfiguration of leaf growth and development pathways during evolution has produced different leaf forms.