The combination of large-scale analysis of plant compounds (metabolomics) and the genetic modification of plants is highly suitable for investigating the biosynthesis of compounds. This is the conclusion of the thesis by Joost Lücker, with which he obtained his doctorate from Wageningen University on 8 October 2002. Lücker studied the synthesis of so-called monoterpenes, an important plant compound. The outcome of his research will contribute to a better understanding and control of the biosynthesis of monoterpenes.
Monoterpenes are partly responsible for smell and taste in plants. Small, volatile and soluble in fat, thousands of different structures have been identified. Monoterpenes are involved in the interaction between plants and insects, plants and micro-organisms and between different plants. Many are of commercial importance (for example menthol, limonene and linalool), as they are used in food and drinks, perfumes and cosmetics, as well as in many cleaning substances. They also make a significant contribution to the characteristic smell of flowers, which is important for pollination and the economic value of cut flowers.
Lücker used the metabolomics facilities at Plant Research International to analyse monoterpenes and other important components in extracts and aromatic substances from plants. He also worked with plants that themselves make no monoterpenes. Via genetic modification, Lücker succeeded in equipping these plants with the genes for certain enzymes, which then enabled them to produce monoterpenes. He also managed to introduce genes for extra enzymes into plants that already produced monoterpenes. As the plants began to make new monoterpenes, these experiments showed that the biosynthesis of monoterpenes can be effectively controlled.
Among the genes used by Lücker were those responsible for the synthesis of monoterpenes in lemon, a fruit that contains a great deal of monoterpenes. He isolated four genes which code for enzymes (monoterpene synthesis). These proved to be responsible for the biosyntheses of 90% of the compounds present in the essential oil of lemon peal.
Lücker demonstrated the working of these enzymes by expressing the genes in bacteria and then characterising the resulting enzymes and products via metabolomics techniques. He then went on to use the genes to control monoterpene synthesis in tobacco plants. Via genetic modification and targeted crossings, Lücker succeeded in developing plants capable of producing three new enzymes. As a consequence, the odor profile of the tobacco plants was dramatically altered: the leaves and flowers giving off exceptional amounts of new monoterpenes. These results have potential for the improvement of smell and taste of plants and a reduction in their susceptibility to fungi and insects.
List of press releases for 2002