Metabolic Engineering of Plant Volatiles

The fact that fruits of many modern commercial cultivars have lost flavors, flowers have lost scent and plants have lost defense volatiles, have made these specialized metabolites attractive targets for metabolic engineering. Remarkable progress achieved in the past couple of decades in discovering the biochemical pathways, genes and enzymes responsible for biosynthesis of plant volatiles have made this metabolic engineering feasible. Different approaches have been already successfully used to improve the scent and aroma quality of flowers and fruits and enhance plant defenses. They include the modification of existing pathways, changing substrate or precursor availability, the introduction of new enzymes catalyzing the formation of new volatiles, expression of transcription factors or transporters or the introduction of multiple genes. This chapter reviews the results of these experiments highlighting crucial factors, unpredictable outcomes, challenges and limitations of successful metabolic engineering of plant volatiles. Finally, the potential applications of the new CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) gene editing techniques for engineering volatile production are discussed.