Discovery and characterization of genes regulating plant volatile content

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Plants synthesize a vast array of volatile organic compounds. Derived from primary and secondary metabolites, they contribute to functions as diverse as defense against herbivores and pathogens, plant to plant interactions, as well as attraction of pollinators and seed dispersers. From a human perspective, they are responsible for the complexity of flavor as well as the aroma of flower and spices that we enjoy. Despite the importance of plant volatiles, regulation of their synthesis still remains poorly understood. The long term aim of my research program is to contribute to the discovery of genes implicated in synthesis and regulation of plant volatile production, using tomato (Solanum lycopersicum) as a model plant. Toward that objective, I will first focus my attention on a group of volatiles derived from branched chain amino acids. That group of volatiles is one of the most important for tomato flavor and is widespread in the plant kingdom. Identification of candidate genes will be done using a multifaceted approach. First, populations of introgression lines from wild species will be used to uncover quantitative trait loci (QTL) for volatiles. Fine mapping of the QTL will be done to discover the responsible genes. Second, candidate genes will be identified by using bioinformatics analyses. The third approach will focus on correlations between gene expression and volatile contents, using a set of diverse heirloom varieties. Once candidate genes are identified, their functions will be evaluated in planta. Finally, enzymatic assays will be performed to characterize the in vitro activity of identified enzymes. The study of this pathway will advance our understanding of how plants modulate secondary metabolism. Regulation of metabolic flux in secondary metabolism is increasingly recognized as a crucial topic with a direct impact on plant fitness and yield. Moreover, the results of this research program are likely to have a direct impact on selection of cultivars with better aroma and flavor. Commercial cultivars are often viewed by consumers as having poor flavor and the identification of volatile pathway genes is essential for reintroducing heirloom flavor into modern cultivars.