Biosynthesis of Nucleotide Sugars for Cell Wall Polymers
Plant cell walls contain many different polymers, in particular cellulose, hemicellulose, pectic compounds and (structural) proteins. In the model plant Arabidopsis thaliana, approx. 50 % of the cell wall biomass is derived from the precursor UDP-glucuronic acid (UDP-GlcA). We are interested in the biosynthesis of UDP-GlcA, which occurs via two different pathways in plants. The pool of nucleotide sugars that is used to synthesize cell walls is well separated from nucleotide sugars which are used to synthesize sucrose, the major sugar in Arabidopsis transported into sink tissues. The quantitatively most important route for the biosynthesis of UDP-GlcA is catalyzed by the enzyme UDP-glucose dehydrogenase (UGD) which is represented by a small gene family with four members in Arabidopsis (and other plant species). A second pathway is catalyzed by the the enzyme myo-inositol oxygenase (MIOX), a unique enzyme involved in the oxygenative ring cleavage of inositol into glucuronic acid. Both enzymes are located at an entry point into the pathway, catalyzing energetically irreversible reactions. This fact makes both enzymes ideal points of regulation for partitioning of assimilates from photosynthesis between plant growth and the biosynthesis of new cell wall material on one hand and the formation of storage compounds (e.g. starch) on the other hand.
Biosynthesis of Nucleotide sugars
Biotechnology of MIOX mutans
Recycling of nucleotide sugars
Programmed Cell Death in Plants
Pathogenic microorganisms usally do not cause disease on plants. Often they are unable to colonize a host plant or they are specifically recognized at an early stage of infection. This recognition process often leads to the so-called hypersensitive reaction (HR), a form of programmed cell death in plants. In many cases this cell death program is controlled by salicylic acid. The molecular mode of action of salicylic acid in the hypersensitive reaction is largely unknown. Our aim is to shed more light on the cell death control by salicylic acid and to investigate novel proteins involved in this important process.