Laboratory of Molecular Plant Physiology
Fructan metabolism in plants
Fructans are water-soluble fructose-based polysaccharides that are becoming increasingly popular as health-improving compounds (prebiotics). They are found in a diverse range of higher plant species, where they are derived from sucrose. Their metabolism and function are being intensively investigated. The goal is to unravel the physiological functions of fructans in plants, and to understand their benefits over starch and sucrose. A multidisciplinary approach is needed in the study of fructans, including chemical characterization, purification, localization and characterization of enzymes of fructan metabolism, and analysis of gene expression and regulation.
It is believed that fructans can contribute to drought and frost tolerance. Engineering fructan metabolism in edible parts of world crops (e.g., rice) would not only increase the stress tolerance of these crops but also allow these healthy compounds to be cheaply disseminated world-wide.
Structure - function analysis on family 32 of glycoside hydrolases
In plants, close relationships at the biochemical, molecular and structural levels are found between fructan biosynthesizing and degrading enzymes on the one hand, and acid invertases on the other hand. All these enzymes belong to family 32 of the glycoside hydrolases (GH 32; http://afmb.cnrs-mrs.fr/CAZY). Plant invertases fullfil crucial roles during growth and development. These enzymes interfere with sugar transport and sugar signalling, as such they influence carbohydrate partitioning and determine crop quality and crop yield (biomass production).
Nevertheless, a tremendous variation in donor and acceptor substrate specificities is observed among the plant GH32 enzymes. To explain these substrate specificities at the molecular level, it is necessary to resolve the crystal structures of complexes formed between the enzymes and their different substrates and to study enzymes mutated in specific amino acid residues. These fundamental insights could contribute to the development of new and better enzymes for specific agronomical and industrial applications.
Metabolism of alternative sucrosyl oligosaccharides
Besides fructans, other sucrose-derived oligosaccharides (SOS) occur in plants. Among them, the Raffinose Family Oligosaccharides (RFO) are the most common and the best studied. We became interested in the metabolism of lychnose and lychnose- related oligosaccharides in the Caryophyllaceae. We use Stellaria media as a model plant.
Other higher plants, algae and mosses are intensively screened to detect new SOS/fructan types and new hexosyl transferases. Introduction of these new transferases into crop plants could improve yield or make them stress-tolerant.
