Molecular Systems Biology - University of Vienna

Plant Signalling - Markus Teige group

Contact

Room: 3.055
Djerassiplatz 1
1030 Vienna, Austria
+43-1-4277-76530
markus.teige(at)univie.ac.at

Markus Teige

We study how plants adapt and acclimate to a changing environment or to stress conditions. How are environmental signals perceived and further processed in plants, and which processes are regulated? To answer these questions, we investigate different pathways, which are triggered by calcium-signals and test different mutants for a physiological phenotype. We are particularly interested in the subcellular localization of the signalling molecules with a special focus on chloroplast-related metabolism.

Therefore we performed directed proteomic studies and bioinformatics in order to identify new signalling components in chloroplasts (Bayer et al. 2011, 2012, 2014, and 2015) and studied effects of protein modification in the subcellular targeting of protein kinases (Stael et al. 2011 and 2012). Detailed functional studies of chloroplast-related signalling were initially performed within the Marie-Curie training network (ITN) COSI and are now being followed-up in the framework of the newly funded Marie-Curie ITN CALIPSO. Within this network of 9 European Universities and 3 private partners we study Ca2+- and light-signalling pathways in photosynthetic organisms.

Image: Isolated Arabidopsis chloroplasts on a Percoll gradient (upper part) and three chloroplasts expressing a green-fluorescent protein (GFP) fusion. Red, Chlorophyll-fluorescence; green, YFP signal.

The decoding of calcium signals by calcium-dependent protein kinases (CDPKs) serves as example for stress acclimation. We identified a CDPK, which is required for acclimation to salt-stress (Mehlmer et al. 2010; Latz et al. 2013). This CDPK seems to regulate different cellular targets at the vacuole, the plasma membrane, in the cytosol, and also in the nucleus. Mechanisms of metabolic reprogramming in response to different growth conditions were further addressed in the Marie-Curie Training Network (ITN) MERIT. Here we analysed the regulation of the bZIP transcription factor bZIP63 by phosphorylation in collaboration with eight European partner groups. A major outcome of this project was the discovery of a novel mechanism regulating the combinatorial control of gene expression by bZIP transcription factors. We found that bZIP63, a transcription factor of the C-class of bZIPs, is phosphorylated by CPK3 in a Ca2+ -dependent manner, and by SnRK1 in response to the energy status of the cell (Mair et al. 2015). The phosphorylation of bZIP63 at three highly conserved sites in the very N- and C-terminal ends is indeed required for its biological function for metabolic reprograming in response to starvation. The phosphorylation triggers a switch of hetero-dimerization and thereby alters downstream gene expression.

Phosphorylation of the bZIP transcription bZIP63 by the energy sensing kinase SnRK1 mediates dimerization of the bZIP transcription factors for acclimation to low-energy stress as described in the paper by Maier et al., 2015 in eLife.

Future directions of our work will be to untangle how phosphorylation of these transcription factors regulates the activity and thereby the expression of downstream genes, and to study newly discovered factors in chloroplast signalling. A particular focus in this aspect will be the decoding of calcium signals in the chloroplast.

Links to international projects

FWF P28491 Cross-talk of Calcium- and Energy Signalling in Plants (CESP) (2016-2018)

One current project, funded by the FWF since 2016, addresses two major aspects of plant energy and stress signalling: (i) The cross-talk between calcium- and energy-dependent signalling pathways in plants’ responses to stress, and (ii) The importance of the subcellular localization of these signalling events. These are fundamental research questions to understand signalling in general in all eukaryotic cells as the involved principal signalling mechanisms are evolutionary highly conserved in animal, yeast, and plant cells. How do CDPKs and SnRKs mediate appropriate responses in the cellular or organismal context, are they active under different conditions, for example in response to different stimuli, and how do they influence each other and how do they regulate organellar events such as photosynthesis? And finally, do they function at the same subcellular localization or could a spatial/temporal separation of the signalling pathways be an explanation for the apparent redundancy?

Low-energy stress leads to changes in SnRK1. Abiotic/biotic stress leads to changes in CDPK. Ca2+ facilitates the finding of a common target (e.g. bZIP63, NR ...) which then triggers a specific response that facilitates growth of the plant.

FWF P25359 Protein phosphorylation and calcium signals in chloroplasts (2012-2015)

Chloroplast metabolism is ultimately linked to plant productivity and needs to be quickly regulated in response to changing environmental conditions. A deeper understanding of the involved regulatory mechanisms is essential to be able to improve future yields and performance of crops. Chloroplasts are integrated into the signalling network of the entire cell. In addition to the predominant redox regulation in chloroplasts, reversible protein phosphorylation is a key mechanism for the regulation of cellular processes and for signal transduction in response to environmental changes.

This project aimed at the functional characterization of newly identified regulatory proteins in chloroplasts including a novel protein kinase, and calcium-binding proteins. Furthermore we investigated the impact of calcium-dependent phosphorylation on chloroplast metabolism using different targets of phosphorylation.