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Research project (§ 26 & § 27)
Duration : 2019-05-01 - 2020-10-31

Targets of project In Phase I of project a biosensor for androgens on the basis of Aspergillus nidulans should be established and validated –using the reaction of the test system with different androgen concentrations. In Phase II of project different samples from animals at different reproduction stages will be analyzed. The microbiom of the animals will be considered and compared to samples only stored at frozen stages.
Research project (§ 26 & § 27)
Duration : 2019-06-01 - 2023-05-31

The plant-specific family of arabinogalactan proteins (AGPs) is implicated with a multitude of biological functions and their O-glycan might be crucial for either ligand interactions or for crude biophysical or structural protein properties. In this research proposal, however, I propose a role of O-glycosylation of the AGP type for protein fate by introducing the concept of an O-glycosylation checkpoint. I discuss evidence for the importance of O-glycosylation for protein fate in all eukaryotes and specifically describe the case of the moderately O-glycosylated FASCICLIN-LIKE ARABINOGALACTAN PROTEIN 4 (FLA4) from Arabidopsis thaliana. FLA4 abundance and localization strongly depends on its O-glycosylation. With a set of hydroxyproline-specific galactosyl transferases FLA4 acts in a linear genetic pathway necessary for normal root growth, salt tolerance and seed coat structure. Using FLA4 as genetic paradigm for a functional O-glycoprotein, I suggest hypothetical models of where and how O-glycosylation might influence the fate of plant proteins. I propose experimental approaches to elucidate the genetic and molecular mechanisms that determine the fate of FLA4 in dependence of its O-glycosylation status. Precise definition of proline hydroxylation and -glycosylation as well as molecular identification of crucial modification sites on FLA4, the cell biological elucidation of the involved organelles and the investigation of the degradation mechanism will comprise the first example for an endogenous plant protein that is controlled by its O-glycosylation state. Forward genetic isolation and next generation sequencing-based identification of suppressors of O-glycan dependent control of FLA4 abundance will provide novel genetic components of this process. A remarkable set of signalling proteins that have not previously been considered to be O-glycosylated, potentially also contain this modification. Therefore, it is likely that the O-glycan checkpoint acts on various regulatory pathways. The outcomes of this project will provide an important contribution to our fundamental knowledge of protein glycosylation and proteostasis and might thus contribute to improved stress tolerance of crop plants and the use of plants as factories
Research project (§ 26 & § 27)
Duration : 2019-02-01 - 2022-01-31

In all eukaryotic cells, N-glycosylation is an essential and very common modification of proteins entering the secretory pathway. N-glycosylation affects many properties of proteins including their conformation and interaction with other proteins. This highly conserved process is characterized by the transfer of a preassembled oligosaccharide from a lipid carrier to selected asparagine residues present in a conserved amino acid sequence motif within newly synthesized proteins. A single membrane-bound multiprotein complex - called the oligosaccharyltransferase (OST) complex -catalyses the transfer of the oligosaccharide to newly synthesized protein. In yeast and metazoans, the OST complex is well studied and consists of one catalytically active subunit and several different non-catalytic subunits with accessory function. By contrast, little is known about the composition of the plant OST complex and the functional roles of many subunits remain elusive. Importantly, we have recently shown that human glycoproteins are incompletely N-glycosylated in plants. A comparison of structural features and amino acid sequence motifs from already known plant and mammalian OST subunits indicate clear differences that may explain the observed variation in N-glycosylation efficiency. Hence, it is hypothesized that the composition of the OST complex and the molecular function of individual subunits differ substantially between plants and mammals. In this project, we will investigate the N-glycosylation defect of OST mutants using a glycoproteomics approach and identify the plant OST complex composition by affinity purification coupled to mass spectrometry-based identification of proteins. Newly identified OST subunits will be explored for their involvement in N-glycosylation of proteins using biochemical methods, advanced bioimaging and phenotypic characterization of mutant plant lines.

Supervised Theses and Dissertations