Research at the Laboratory of Molecular Biology

Since its origin in 1972, the department of Molecular Biology has made major contributions to the development of molecular biological technology for fundamental and applied research. Over the past three decades students conducting research at our department have found positions in a wide variety of research areas including medical research, plant and animal sciences and biotechnology. Thus, students mastering the molecular technology offered at our department will have a sound basis for future careers in human, animal, and plant sciences.

The department of Molecular Biology has several research groups that are active at different areas of plant (developmental) molecular biology. Their research programs aim to understand fundamental processes of plant biology and to use this fundamental knowledge in applied projects. For this we make use of two inportant model systems; Medicago root nodule development and Arabidopsis root development. Advanced techniques based on fluorescence microscopy are used in many of the ongoing project in order to be able to study processes within cells: this allows us to follow the interaction between proteins (for example between receptor and ligand) in living cells, to determine how and where genes are stored in the nucleus, and to determine the mobility of molecules. A brief description can be found below, for a more elaborate description use the links shown at the right side.

The research described here is being carried out in collaborations with Dutch and foreign colleagues, so there are also good possibilities for internship projects.

Rhizobium infection and root nodule formation

Legumes comprise one of the most important agricultural taxa worldwide providing a major source of proteins for humans and animals, and nitrogen for soil improvement. Especially for development of sustainable agricultural systems legumes will play a major role, since they are able to establish a symbiotic relation with bacteria. Under nitrogen limiting conditions, the leguminous plants will form root nodules in where the bacteria are hosted and will find the proper conditions to reduce atmospheric nitrogen into ammonia. Rhizobium induced nodule formation on legume roots starts with (1) reprogramming of differentiated root cortical cells in order to form a nodule primordium and (2) infection of the root by the bacteria. For both processes the bacterial secreted signals, named nodulation (Nod) factors play a crucial role. From genetic screens carried out at molecular biology and several other groups, a small set of 8 genes has been identified that are involved in Nod factor perception and signaling cascade. Research now is concentrated on the function of the proteins encoded by these genes and how these proteins interact with other plant components (like receptors, transcription and membrane factors and peptide growth regulators) to induce a nodule meristem and to allow Rhizobium to enter the root and infect cells by forming symbiosomes (specialized membrane compartments. To determine how these crucial genes for nodule formation have evolved, also the function of closely related genes in non-nodulating legume species is studied.

The influence of chromatin structure on development

Recent data from various biological systems indicate that the way the genomic DNA is organized in the cell nucleus is very important. This organization contributes to the regulation of expression of genes during growth and development. Depending on the position in the nucleus, DNA can be present in more condensed or less condensed structures called heterochromatin and euchromatin respectively. Each structure has a characteristic DNA methylation and histone acetylation/methylation pattern (histone code). Genes that are located in heterochromatin are usually silenced, and whether certain regions are heterochromatic is regulated during development. Such mechanisms controlling gene silencing play an important role in suppressing cancer and in terminal differentiation. We will look in detail to the nucleus during development of cells in the Arabidopsis root in order to understand how and when a cell decides to divide and develop. Changes in organisation are direct indications for modified chromatin and a changed gene expression pattern. Furthermore, we look at the role of various chromatin remodelers and chromatin binding proteins in these processes. Experimental approaches used for these studies include molecular and cytological analysis of nuclear organisation of Arabidopsis chromatin mutants, and studying localisation and mobility of GFP-tagged chromatin proteins. In addition we are developing a polymer based molecular dynamics model that mimics the behaviour of chromosomes in an interphase nucleus. Since the mechanisms controlling nuclear organization are conserved from animals to plants, Arabidopsis can be used as a model to obtain insight in such general mechanisms that are also relevant for human nuclear organization. This has an impact for e.g. tumour biology and in vitro formation of human organs.