Manipulation of Secondary Metabolism to Alter Floral Scent

To attract pollinators, many flowering species release diverse blends of volatile compounds from their flowers. One-third of our total diet depends, directly or indirectly, upon insect-pollinated plants including most fruit trees, berries, nuts, oilseeds, and vegetables. The yield of many insect-pollinated, agronomically important, crops could be enhanced by increasing pollination efficiency via the metabolic engineering of floral scent. Customization of floral scent for specialized pollinators will not only increase the attractiveness of flowers but also reduce the chance of pollen loss and unsuccessful inter-species pollination. The chemistry of plant volatiles is well understood, however, little is known about the biosynthesis of this diverse group of compounds. How do plants produce volatile compounds? What molecular mechanisms control their accumulation and release? We have integrated metabolic profiling, a functional genomic approach, and targeted metabolic engineering with metabolic flux analysis and modeling, to provide a comprehensive understanding of the regulation of flux through metabolic networks. We used different approaches for metabolic engineering of the spectrum of volatile metabolites, including the modification of existing pathways by shifting metabolic flux towards target compounds and the introduction of novel scent compounds normally not found in the host plant. We will discuss critical factors that limit volatile trait modification and present approaches for rational metabolic engineering of volatile emission based on computer-assisted metabolic flux analysis.