The Biomolecular Imaging group of Jan Willem Borst utilises fluorescence imaging and spectroscopy tools to understand how proteins function in their natural habitat. In our research, we fuse fluorescent tags (GFP variants) to proteins of interest and apply functional imaging modules like confocal imaging, Förster resonance energy transfer (FRET), fluorescence lifetime imaging microscopy (FLIM) and fluorescence correlation spectroscopy (FCS) to resolve protein localisations and interactions in living cells.
We focus on studying the nuclear auxin signaling pathway in the liverwort Marchantia polymorpha, which is an early diverging land plant that has the simplest possible complete auxin system with a limited number of auxin response proteins. The aim of this project is to obtain quantitative parameters including concentrations of each response protein in the live organism, protein turnover rates and dissociation constants of all protein-protein interactions and integrate these parameters into a mathematical model. We will use this model to identify critical factors within the protein network that affect signal output and expect to reveal principles of dynamic auxin response, and thereby providing a quantitative framework for plant hormone biology.
Recently, in a joint effort with Carlo van Mierlo and Dolf Weijers, we investigate the roles of intrinsic disorder and phase separation for the plant transcription factor proteins of the AUXIN RESPONSE FACTOR (ARF) family. ARFs contain an intrinsically disordered (ID) domain, which lacks an ordered three-dimensional structure and facilitates liquid-liquid phase separation (LLPS), thereby forming protein condensates or membrane-less organelles. In mammalian systems, these condensates have been shown to play a role in DNA-protein complex formation, protein buffering or regulating protein activities. However, the significance of ARF phase separation in plants is still unknown. In this new initiative, we aim to reveal the biological significance of ARF phase separation in the regulation of auxin dependent gene expression in plants.