Opportunities and challenges for metabolic engineering of secondary metabolite pathways for improved human health characters in fruit and vegetable crops

Metabolic engineering of plant secondary metabolite pathways for improved human health is a focus of many current plant biotechnology programmes. These aim to enhance the concentrations of essential vitamins and minerals or to develop foods with increased phytochemicals that have long-term benefits in reducing the occurrence of cancers and degenerative diseases. This article reviews some of the general approaches and highlights current successes in this field of research. The focus is on fruits and vegetables, the compounds characteristic of those crops, and the efforts towards the generation of new cultivars using marker assisted breeding or genetic modification approaches. The difficulties in identifying target dietary amounts of secondary metabolites and the role of human gut microbiota in mediating resulting health effects are also discussed. Specific consideration is given to the phenylpropanoid and carotenoid groups of compounds.