Projects

Cell surface receptors mediate responses to environmental and developmental cues. The activity of surface receptors is location specific, dependent upon the highly dynamic membrane trafficking network and receptor-mediated endocytosis (RME). The spatio-temporal dynamics of RME are therefore critical to receptor function. The pattern recognition receptor (PRR) for bacterial flagellin (flg22) FLS2 resides in the plasma membrane and is internalized upon activation by flg22. Yet, it remained unknown which endosomal pathways were engaged by FLS2 and to what extent FLS2 endocytosis intercepts with the flg22 responses. Open key questions in FLS2 endocytosis are: What are the molecular components required for FLS2 uptake? What is the molecular mechanism, by which the signal of the activated receptor is triggering internalization?

To dissect FLS2 endocytic trafficking we established Arabidopsis cotyledon leaves and N. benthamiana leaves as model systems for studying cell biological questions, and apply a combination of co-localization studies, chemical inhibition and genetic interference of membrane trafficking. The transient behaviour of FLS2 endocytosis raises technical challenges for studying this process in detail. To address this issue, we employed cutting-edge quantitative high-throughput confocal imaging techniques and developed custom algorithms for quantifying membrane objects. Our approach to identify regulators of FLS2 endocytosis combines chemical inhibition followed by mass spectrometry, and reverse genetics. Future visions for this project include subcellular analysis of other PRRs, and genetic screenings. Also, if PRR endocytosis is crucial for plant immunity, we hypothesize that effectors will target components of the PRR endocytic pathway.

2. Are receptor kinases involved in ROS signaling? (PROSIG)

The main objective of this project is therefore to determine how single RLKs discriminate diverse functions and supply specificity in stress signaling. More information at: http://www.erapg.org

3. How do plants open and close stomata? (STORM)

Successful pathogens overcome PAMP-induced stomatal closure to gain access to the plant leaf. It is therefore critical to study the molecular strategies used by the pathogens that succeed in stomatal opening. Stomatal apertures are regulated by differences in turgor pressure resulting in an increase or decrease of guard cell volume. There is good evidence that the changes in volume are accommodated by changes in perimeter, which involves exocytic and endocytic trafficking, and we exploit high throughput imaging technologies to determine the pathways underlying stomatal closure. This project is supported by the European Research Council (ERC).

4. What can we do with high throughput imaging in plants to understand biological processes?

To drive our research it is important to continuously develop novel methods and algorithms for high throughput imaging. This will places us at the forefront of bioimaging in plants and will provide novel insights into the plant processes we are researching. We are continuously developing new algorithms on the basis of the Acapella software platform for analyzing images generated by high throughput and standard confocal microscopy. The algorithms and their application are listed here: