PhD Defence Dorottya Veres
Post-translational regulation of glucosinolate
transporters
Summary:
Transport proteins represent the connection between the interior of the cell and its environment. Therefore, they play a crucial role in multiple cellular functions such as nutrient uptake, maintenance of cellular homeostasis and intercellular communication. In plants, on a higher level, transporters affect the distribution of their substrates throughout the entire plant. Therefore, transport processes need to be tightly regulated in response to environmental cues, to ensure appropriate distribution of nutrients and secondary metabolites. Protein-level regulation allows for a fast response and post-translational modifications have an important role in transporter regulation. However, post-translational modifications in plant transporters remain largely unexplored.
In this PhD thesis, the post-translational regulation of the two glucosinolate transporters GTR1 and GTR2 was investigated. We used untargeted screening to identify interacting proteins of the two transporters with the aim to find modifying enzymes involved in post-translational modifications. Among the interacting proteins, we found several candidates that are involved in response to biotic and abiotic stress and several redox-regulators. To validate and further characterize the interactions, a combination of targeted yeast two-hybrid assays and FRET was used, however we encountered challenges with both methods. From the several kinases found to interact with the transporters, one kinase was found to negatively regulate the transport activity of GTR2 in Xenopus oocytes and results indicate that two others potentially increase the activity of GTR1.
Identification of post-translational modifications and the interaction partner involved requires knowledge of transporter function. However, for some transporters characterization of transport function is already a challenge. This thesis describes three cases, where problems with the characterization of transporters in the Xenopus oocyte system were encountered.
The results presented in this thesis, represent the first step in characterizing the post-translational regulation of the glucosinolate transporters and contribute to the understanding on how plants coordinate the distribution of glucosinolates in different environmental conditions.
Supervisors:
Professor Barbara Ann Halkier, Molecular Plant Biology
Associate Professor Hussam Hassan Nour-Eldin, Molecular Plant Biology
Assessment committee:
Professor Enrico Martinoia, University of Zurich, Switzerland
MPG Group Leader Tonni Grube Andersen, Max Planck Institute, Cologne, Germany
Associate Professor Anja Thoe Fuglsang, Transport Biology (chair)