Discovery and characterization of genes regulating plant volatile content

植物合成大量的挥发性有机化合物。它们来自初级和次级代谢产物，有助于多种功能，如防御食草动物和病原体，植物与植物的相互作用，以及吸引传粉者和种子传播者。从人类的角度来看，它们负责味道的复杂性以及我们喜欢的花和香料的香气。尽管植物挥发物的重要性，其合成的调控仍然知之甚少。我的研究计划的长期目标是以番茄（Solanum lycopersicum）为模式植物，为发现与植物挥发性物质合成和调控有关的基因做出贡献。为了达到这个目的，我将首先把注意力集中在一组来自支链氨基酸的挥发物上。这组挥发物是番茄风味最重要的成分之一，广泛存在于植物界。候选基因的鉴定将采用多方面的方法进行。首先，从野生物种的渐渗系群体将被用来揭示挥发物的数量性状基因座（QTL）。将进行QTL的精细定位以发现负责的基因。第二，通过生物信息学分析确定候选基因。第三种方法将集中在基因表达和挥发性成分之间的相关性，使用一组不同的传家宝品种。一旦候选基因被确定，它们的功能将在植物中进行评估。最后，将进行酶测定，以表征已鉴定酶的体外活性。对这一途径的研究将进一步加深我们对植物如何调节次生代谢的理解。植物次生代谢中代谢通量的调控越来越被认为是一个直接影响植物适合度和产量的重要课题。此外，该研究项目的结果可能会对选择具有更好香气和风味的品种产生直接影响。商业品种通常被消费者视为具有较差的风味，并且鉴定挥发性途径基因对于将传家宝风味重新引入现代品种中是必不可少的。

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.