Membrane contact sites (MCS) represent physically tethered regions between membranes of cell compartments that allow communication and interaction. Within these MCS, various proteins mediate tethering, functioning and maintaining of the MCS. In contrast to the knowledge of MCS in mammalian cells or yeast, it is greatly unknown how plastids interact with the mitochondria, endoplasmic reticulum and other cellular compartments in the plant cell. This project aims to identify plant membrane contact sites and the involved proteins that mediate this type of interaction between organelles in the plants.
Photorespiration – transport and integration in the cellular network
Photorespiration, also called C2 photosynthesis or “breathing in the light”, is essential process in photosynthetic organisms. The unspecificity of the CO2-fixing enzyme Rubisco, to also accept oxygen as substrate results in the production of 2-phosphoglycolate. Accumulating 2-phosphoglycolate inhibits several enzymes of the Calvin-Benson-Bassham cycle and needs to be detoxified. Although the core enzymes of the photorespiratory cycle are known, A) several required transport proteins are unknown and B) the metabolic interaction of photorespiration with accessory metabolic pathways is less well understood. Within these projects we aim at A) characterizing novel photorespiratory transport protein and B) understand the integration of photorespiration in the cellular metabolic network.
Researchers: Nicole Linka
The role of transport proteins in cellular metabolism
Subcellular compartmentalization enabled pro- and eukaryotic organisms to target metabolic reaction into distinct organelles. To ensure metabolite flow within the metabolic network of the cell, organellar membranes contain pores, channels and transporters. This project aims to understand the roles of transport proteins in cellular metabolism by (A) biochemical characterization of recombinant proteins in vitro using liposome systems, (B) physiological characterization of loss-of-function mutants, and (C) in vivo analyses with isolated intact organelles.
The peroxisomal hub - Connecting metabolic pathways in plants
Peroxisomes are essential hubs for plant metabolism. They are involved in numerous metabolic processes, including photorespiration, fatty acid degradation, synthesis of signalling molecules and secondary products. Thus, a high number of substrates, intermediates and cofactors needs to be transported across the peroxisomal membrane. We study the flux of these metabolites by combining molecular biology, genetics and biochemistry. Our goal is to describe and fully understand how peroxisomes are connected to the metabolic network of plant cell.
Researchers: Katarzyna Krawczyk and Nicole Linka
Role of DUF 3411 proteins in the interaction of plastids with the cytoplasm
Plastids in plants and other plastid-harboring eukaryotes fulfil a broad range of metabolic functions, ranging from photosynthesis to fatty acid and amino acid biosynthetic pathways. It is still unknown how amino acids, which are mostly biosynthesized in the plastid stroma, are exported to the cytoplasm and how plastids during the early stages of plastid development are supplied with amino acids from, e.g., seed storage proteins. In yeast and animal cells, mitochondria are tethered to the endoplasmic reticulum by specific proteins. It is unknown how plastids (and mitochondria) in plant cells interact with the endoplasmic reticulum and which proteins mediate the interactions between these organelles and other cellular membrane systems. In the proposed work, we will test the hypothesis that plastidial membrane proteins containing a domain of unknown function (DUF3411) represent a novel class of amino acid transporters in plant cells. Further, we will develop novel methodology to identify proteins that mediate the interactions between plastids and mitochondria in plant cells with the endoplasmic reticulum. In this SFB-funded project we collaborate with the proteomics facility at the BMFZ at the HHU.
Researcher: Karolina Vogel