Flowering is of unprecedented importance and plants have evolved an elaborate genetic network that integrates both environmental (e.g. light, temperature, nutrient status) and endogenous signals (e.g. hormonal levels), to ensure that flowering occurs when conditions are most favorable. Flowering has been studied intensively by genetic approaches, resulting in the identification of a comprehensive list of key regulatory genes including a large number of genes from the MADS box transcription factor family. Despite this wealth of knowledge, the molecular mode-of-action of flowering time regulating MADS domain proteins is not fully understood and quantitative information about the system is lacking.
Members from the MADS box transcription factor family act as central players in the flowering network and function either as activators or inhibitors of flowering. MADS box proteins are known to bind DNA as dimers and are able to multimerize into higher-order complexes. Furthermore, these proteins regulate their own and each other’s expression via positive and negative (auto-) regulatory loops. We are investigating how the balance between activation and repression of the floral transition is established at the molecular level. For this purpose we perform comprehensive protein-protein interaction studies, native MADS domain protein complex isolations, genome-wide target gene identifications by ChIPseq, and localization and quantification of protein expression levels. Ultimately, this should result in an ordinary differential equation (ODE) model that can predict accurately when a plant starts to flower as a function of transcription factor concentrations and behavior.
In addition we are interested in the molecular mechanisms underlying the functioning of 'ABC-class' MADS box proteins that specify the identity of the four different floral organs in a combinatorial manner. For this purpose a similar approach is followed and a mathematical model has been developed.