VIB general meeting location:Blankenberge, België date:12 March 2009
The moss Physcomitrella patens is the only known plant in which homologous recombination occurs in a frequency that allows its application as an engineering tool for targeted knock out and gene replacement. In addition, the genome of P. patens has been completely sequenced and several molecular tools were developed, making of P. patens a plant model system that is easily manageable. We have started to use this novel system to understand the role of trehalose metabolism in plants. Trehalose is a non-reducing disaccharide consisting of two glucose molecules linked by 1α–1α bond. It is present in very different organisms such as bacteria, fungi, nematodes, insects and plants. Several functions have been described for trehalose in nature, being a compatible solute, storage compound and structural part of cell walls. The best-characterized trehalose biosynthesis pathway consists of two steps mediated by the trehalose 6-phosphate synthase (TPS) and trehalose 6-phosphate phosphatase (TPP) enzymes, where the first is catalyzing the synthesis of trehalose 6-phosphate (T6P) while TPP dephosphorylates T6P to form trehalose and Pi. Recent findings show the importance of trehalose and its intermediate T6P in plant sugar metabolism, gene regulation and development, suggesting T6P as a new plant hormone. The plant TPS and TPP genes form multigene families where members are divided in classes I, II and III. We found that members of the three gene classes are present in Physcomitrella and are being differentially regulated by drought and ABA. We are also generating knock out and overexpressing lines for each TPS, TPP and trehalase genes. By using this member of a primitive plant group as a model for trehalose studies, we intend to generate new tools to understand the complex gene regulation in crop plants.