MOLECULAR BIOLOGY FOR THE IMPROVEMENT OF MEDICINAL AND AROMATIC PLANTS

Molecular biology offers promising tools for the creation of novel crop varieties with improved nutritional value, resistance to herbicides, pests, diseases, pollutants and adverse climatic conditions. Using recombinant DNA technology, it is now possible to manipulate the levels and composition of active pharmaceuticals and essential oils in medicinal and aromatic plants. However, in order to accomplish this task, it is first crucial to understand the biochemical pathways and the pattern of expression of the genes responsible for the synthesis of specific natural products. Novel pathways can be introduced into target plants to confer them with novel traits, and in parallel, endogenous genes can be 'turned off' using the proper DNA constructs. Thus, it is possible to manipulate biosynthetic pathways to cause either the accumulation of valuable metabolites or to prevent their degradation. In addition, the organ specificity or temporal restrictions for the production of natural products can be overcome using genetic engineering. The way transgenic plants are obtained, and how the implementation of molecular biology methodologies has improved crops and plant products is described. Exciting possibilities to use transgenic plants for the production of industrial enzymes and other materials, and different examples illustrating methods to either boost the levels of pharmacologically active compounds and change essential oil composition in medicinal and aromatic plants, using recombinant DNA technology, are discussed. The emerging opportunities for the incorporation of genetic engineering into existing breeding programs for the full exploitation of the biosynthetic potential of aromatic and medicinal plants, is reviewed.