The dynamics of O-GlcNAcylation in plants

The transfer of information within a cell is of vital importance for all cellular processes. This holds true for all basic processes such as cell growth or division, but also for the reaction to environmental stimuli and adaptation mechansims.Such signal transduction is often perfomed by small modifications of proteins. The attachment of a small glucosamine (GlcNAc) residue to proteins is one of many possibilites to modify proteins within a cell. This process is called O-GlcNAcylation, and is performed by a single enzyme in animal cells, an O-GlcNAc transferase (OGT). A second enzyme, the O- GlcNAc hydrolase (OGA), is responsible for specific cleavage of this GlcNAc residue, making this a highly dynamic process. Especially important in this context is the fact that O-GlcNAcylation responds to certain stress stimuli as well as the availability of sugar within a cell. Thus, O- GlcNAcylation is one possibility for cells to react to changes in their environment and nutrition, and pass this information on to further basic cellular processes. While O-GlcNAcylation is well studied in animals, still very little is known about it in plants, leaving many questions in this context unanswered. For instance, a specific OGA-like enzyme has not been found as yet in plants, and very few target proteins carrying this modification have been identified so far. On the other hand, it is known that O- GlcNAcylation is essential for embryo development and therefore for the production of viable seeds. In the current proposal I am therefore suggesting experiments with the aim of closing some of the gaps in our knowledge on O-GlcNAcylation in plants. In particular the question of dynamics of this modification will be addressed, along with the question if it responds to growth temperature and the availability of sucrose. These are important questions especially in plants, as they have to adapt constantly changing environments in a highy flexibel manner. The experiments suggested here will therefore clarify how dynamic O-GlcNAcylation is in plants, and if it contributes to adaptation processes.

The transfer of information within a cell is of vital importance for all cellular processes. This holds true for all basic processes such as cell growth or -division, but also for the reaction to environmental stimuli and adaptation mechansims. Such signal transduction is often perfomed by small modifications of proteins. The attachment of small sugar molecules (N-acetylglucosamine or fucose) to proteins is one of many possibilites to modify proteins within a cell. This process is a specific type of O-glycosylation, and is performed by a single enzyme in animal cells, an O-GlcNAc transferase (OGT). A second enzyme, the O-GlcNAc hydrolase (OGA), is responsible for specific cleavage of this GlcNAc residue, making this a highly dynamic process. Especially important in this context is the fact that O-GlcNAcylation responds to certain stress stimuli as well as the availability of sugar within a cell. Thus, O-GlcNAcylation is one possibility for cells to react to changes in their environment and nutrition, and pass this information on to further basic cellular processes. While O-GlcNAcylation is well studied in animals, still very little is known about it in plants, leaving many questions in this context unanswered. One important difference is, that plants carry a protein O-fucose transferase as well as an OGT, and a specific OGA-like enzyme has not been found as yet. On the other hand, it is known that O-GlcNAcylation is essential for embryo development and therefore for the production of viable seeds. In this research project, we performed experiments with the aim of closing some of the gaps in our knowledge on this type of O-glycosylation in plants. In particular the question of dynamics of this modification was addressed, along with the question if it responds to growth temperature and the availability of sucrose. Our results suggest, that while the two modifications do not globally respond to differences in growth temperature, they are generally tightly regulated and balanced with each other.