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物，具有多种功能，如防御食草动物和病原体，植物间相互作用，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，以及我们所享受的花朵和香料的香气。尽管植物挥发物的重要性，调控其合成仍然知之甚少。我研究计划的长期目标是以番茄（Solanum lycopersicum）为模式植物，为发现与植物挥发物合成和调节有关的基因做出贡献。为了达到这个目标，我将首先把注意力集中在一组从支链氨基酸中衍生出来的挥发物上。这组挥发物是番茄风味最重要的挥发物之一，在植物界广泛存在。候选基因的鉴定将采用多方面的方法进行。首先，利用来自野生物种的渗入系群体揭示挥发物的数量性状位点（QTL）。将对QTL进行精细定位，以发现相关基因。其次，候选基因将通过生物信息学分析确定。第三种方法将关注基因表达与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，它们在植物中的功能将被评估。最后，将进行酶分析，以表征鉴定酶的体外活性。对这一途径的研究将促进我们对植物如何调节次生代谢的理解。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应性和产量的重要课题。此外，本研究项目的结果可能会对选择香气和风味较好的品种产生直接影响。商业品种往往被消费者视为风味差，挥发性途径基因的鉴定对于将传家宝风味重新引入现代品种至关重要。

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.