Cell Physiology Department

Currently funded projects

Currently funded projects

Role of a dual-targeted organellar RNA polymerase in controlling organelle function (DFG Research Training Group 2498 project P08)

The discovery that the nucleus-encoded RNA polymerase RPOTmp is dually targeted to both mitochondria and plastids raised the question whether this enzyme may serve to co-ordinate metabolic functions in the two organelles. Answering this question will require to i) comprehensively determine transcriptional tasks of RPOTmp in mitochondria and plastids and ii) investigate how this enzyme’s activity and subcellular targeting are controlled. We are employing next generation sequencing-based approaches to determine promoters used and genes transcribed by RPOTmp in mitochondria. This work is complemented with investigations of the partitioning of RPOTmp between mitochondria and plastids. In addition, we are scrutinising prior observations of stimulated mitochondrial transcription in plants that are impaired in mitochondrial energy conversion.

See RTG 2498 website for more information.

Functional characterization of mitochondrial supercomplexes

Respiratory supercomplexes are stoichiometric higher-order assemblies of two of more OXPHOS complexes. Despite their ubiquitous presence in all organisms investigated and the growing number of supercomplex structures obtained recently, their function is still unresolved. It has been suggested that they might play an important role in the structural organization of the cristae or that they are improving the efficiency of the electron transfer between OXPHOS complexes or that they play a protective role either by stabilising the individual complexes or by reducing ROS production. However, data in favour and in disfavour of all the different hypotheses exist in the literature and the physiological function of OXPHOS supercomplexes remains an enigma. We have isolated several mutants lacking OXPHOS supercomplexes during the project ‘Control of complex I proteostasis in plants’ and, therefore, a logical follow-up of this project is to use this unique genetic resource to investigate the function of OXPHOS supercomplexes.

Older projects:

Mechanisms controlling transcription of the plastid genome (FP7 Marie Curie Career Integration Grant POLSPEC)

Organellar phage-type RNA polymerases are indispensable for the transcription of the chloroplast genome. They have fundamental roles in the biogenesis of the photosynthetic compartment of plant cells. The project POLSPEC investigates distinct roles of two phage-type RNA polymerases, RPOTp and RPOTmp, which are present in plastids of dicotyledonous plants where they transcribe the plastid genome together with a third, eubacterial-type transcriptase named PEP. The project has two major objectives: 1. Defining the RPOTp- and RPOTmp-specific plastid transcriptomes and generating a plastid genome-wide map of transcription start sites (TSS) utilised by RPOTp or RPOTmp. 2. Identifying cis-regulatory elements on the plastid genome that direct the transcriptional activities of RPOTp and RPOTmp.

Chloroplast RNA polymerase activity during acclimation (DFG TRR 175 project A01)

This project aims to quantify transcriptional alterations that occur in chloroplasts during acclimation to changes in light or temperature. It will apply chloroplast nascent transcript sequencing strategies (GRO-seq and 5’-GRO-seq) in order to globally assess transcriptional contributions to changes in chloroplast gene expression during acclimation. By combining high-resolution quantitative transcriptional analyses with a reverse genetic approach we will determine distinct contributions of individual chloroplast RNA polymerases to transcriptional alterations.

See TRR 175 website    for more information.

Control of complex I proteostasis in plants

Complex I is a genuine hub of respiration regulation as its activity is important, not only for mitochondrial metabolism, but also for the correct functioning of the whole cellular metabolic network comprising primary metabolism and intracellular signalling. Therefore, a better understanding of complex I biology is required to design new strategies for the manipulation of respiratory fluxes with the objective of improving plant yields. The aim of this project is to elucidate the machinery and mechanisms that guarantee and regulate complex I proteostasis in plants. We have identified several mitochondrial proteins of currently unknown function that are important for maintaining normal levels of complex I. The molecular function of these proteins in complex I assembly, stability or regulation will be investigated in this project.