8. Genetic Engineering of Saponin Target Genes to Improve Yields

Plant is a main source of natural products with diverse chemical structures and biological activities. Among different plant-derived natural products, saponins secondary metabolites are widely distributed across diverse plant species and have great potentials for the pharmaceutical industry, detergents, pesticides and plant disease management. Triterpene glycosides characterized by a 30 carbon atoms, namely oxidosqualene, a major precursor for triterpene aglycone (sapogenin), to which sugar chains are attached to yield the corresponding saponin compounds. However, saponin applications are often limited due to the low yields or accumulation in planta, inadequate of natural resources and the continuous need of the new compounds with superior biological activities. In addition, the biosynthesis and regulatory pathways of the saponin compounds in different plant species are still very limited. Thus development of new methods to improve and diversify the production of saponin glycosides, with a foresight into metabolic engineering, can be an alternative solution to avoid the problem associated with saponin large scale production. In this chapter, we will summarized and discussed the available information regarding saponin engineering in plant and their potential applications for plant disease resistance.