The diversity of plant specialized metabolites is based on a rather limited set of biosynthetic pathways, such as phenylpropanoid or terpenoid biosynthesis. Specialized cells and organs, like trichomes or tapetal cells, overcome a monotonous set of core structures by expression of cell or organ specific transcripts resulting in new combinations of enzymes and therefore, are largely responsible for the diversity of specialized metabolites and pathways providing fitness under changing environmental conditions. This diversification of metabolites is usually associated with only minor differences in enzyme sequence and structure, still resulting in alterations of position and substrate-specificity. These changes enhance the complexity of metabolites in model plants, such as Arabidopsis and even more so in non-model, rather exotic species like Piper nigrum, which are accessible for molecular investigation largely due to the rapid progress in sequencing and bioinformatics.
Our approach combines classical enzyme and substrate purification with molecular tools and cell-specific visualization techniques. Besides the functional properties of individual substrates and products we are also investigating the cell or organ specific distribution of enzymes, localization of metabolites, and identification of selected transporters, required for proper deposition of cell specific molecules. Our current focus is on two topics:
Identification and functional characterization of possible phenylpropanoid, specifically flavonoid glycoside transporters in anthers of the model plant Arabidopsis and investigation of the function of these specific flavonol 1,2-linked sophorosides deposited on the pollen surface.
We investigate the biosynthesis of hydroxycinnamic acid amides, specifically termed piperamides, in fruits of commercially available black pepper (Piper nigrum). The project also comprises the biotechnological use of this large set of metabolites, virtually unexplored at the enzymatic and molecular level in the biosynthesis of physiologically active molecules and their function in vivo.