Plant acclimation to stressful environment such as heat, light and toxic compounds is of paramount importance to maintain fitness and high yield. The redox regulatory signaling network of the plant cell senses metabolic disequilibria and orchestrates the in part extremely fast responses at transcriptional and translational levels.
Prof. Dr. Karl-Joseph Dietz
Previous and Current Research
Organisms often encounter rapidly changing or extreme environmental conditions. Such changes challenge plant metabolism and cause redox disequilibria and reactive oxygen (ROS) or reactive nitrogen species formation which may cause cell damage and cell death. Such processes are involved in yield losses in plants and disease development in animals. To counter such imbalances cells operate a redox signalling network. The network senses environmentally induced redox imbalances and initiates compensatory responses either to readjust redox homeostasis or to repair oxidative damage. The network consists of redox input elements, redox transmitters, redox targets and redox sensors. The basic structure and many components of the thiol-disulfide redox regulatory network are conserved among all cells and most cell compartments. The significance of this network is well established for some pathways, but still emergent for additional functions due to the ongoing identification of novel redox targets.
Peroxiredoxins are thiol-dependent redox sensors. They decompose peroxides and thereby undergo major conformational changes between oxidized dimer, reduced dimer, hyperoxidized decamer and higher order aggregate. These conformers have different functions as peroxidase, chaperone and binding partner.
The kinetics of plant responses to the environment at the transcriptional level is dissected. As early as 2 minutes after transfer from low to high light, a whole transcriptional network of specific transcription factors responds with transient upregulation of mRNA levels and control the acclimation of plants. The results show that plants can respond efficiently and on the same time scale as specialized animal cells.
Novel tools are developed to measure protein protein interactions in vivo e.g. by Förster Resonance Energy transfer between two or three interacting proteins (one step or two step FRET) or to elicit single cells with signal-driving stimuli such as local heat with newly deviced thermocapillaries or functionalized nanoparticles (cooperation with Dr. S. Herth and Prof. G. Reiss, Faculty of Physics).
Future Projects and Aims
The redox regulatory network of the cell is a major determinant of cell function and whole organism fitness, but also of disease and pathology. A more complete understanding of the network will enable targeted improvement of acclimation responses. To this end we have to expand our knowledge in both the empirical and theoretical direction: (i) Dissecting the upstream sensors and downstream targets of the transcriptional high light network. (ii) Developing a quantitative model of the redox regulatory network of the chloroplast. (iii) Devlop novel tools to manipulate and measure single cell responses to a varying environment. (iv) Application of the knowledge to crop plants for stress improvement.