The secretory pathway synthesizes and delivers proteins, lipids and carbohydrates to various locations in the cell. Due to its tremendous importance in the production of edible protein for humankind and its potential for the production of vaccines and high value proteins, a good understanding of this fundamental pathway is timely and important. Our research focuses on the mechanisms controlling protein synthesis by the endoplasmic reticulum and the transport of proteins to the vacuoles or the extracellular matrix. In order to dissect individual steps in these pathways, we use a broad range of methods including genetic engineering, protein chemistry, live bio-imaging using confocal laser scanning microscopy and quantitative biochemical transport assays. Although most of our work is fundamental and curiosity driven, we have started to implement our expertise to establish innovative bio-fermentation and cell perfusion reactors. Products include high value pharmaceutical proteins as well as hydrolases for the sustainable plant-based bio-fuel production.
Current research topics include:
The role of ER chaperones during plant stress responses
We have discovered a novel regulatory pathway that up-regulates chaperone synthesis independently of the unfolded protein response, which is also one of the earliest responses of plants to pathogen attack. Furthermore, we have shown evidence for vacuolar targeting of the ER chaperone BiP. The biological relevance of these two key-findings is currently explored using engineered transgenic plants, Arabidopsis gene-knock-out and precision gene-replacement in Physcomitrella patens.
ER export and vacuolar sorting
Although a lot is known about protein transport signals of soluble proteins, little is known about the way in which sorting receptors progress through the cell. Since many of the key-players of the transport pathways have now been identified, plant cell biology is entering an exciting phase in which progress can no longer be made with gene knock-outs alone. We will actually have to work with the gene-products themselves to understand how receptors initiate vesicle budding and how they recycle once the ligands are released. Using the plant vacuolar sorting receptor BP80 as a model receptor, we are currently trying to map the variety of sorting reactions that take place within the vacuolar sorting pathway.
Secretory pathway engineering
We are currently exploring the possibility to modify protein transport in the secretory pathway to minimize proteolysis and maximize productivity. The strategies are tested in our well-established transient expression system, but also implemented in newly designed bio-fermentation units optimized for plant cell cultures.