Discovery and characterization of genes regulating plant volatile content

植物会合成大量的挥发性有机化合物。它们来源于初级和次级代谢物，具有防御食草动物和病原体、植物与植物之间的相互作用以及吸引传粉者和种子传播者等多种功能。从人类的角度来看，它们造成了我们喜欢的复杂的味道以及花香和香料的气味。尽管植物挥发物很重要，但对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 Lycopsicum)为模式植物，为发现与植物挥发性物质合成和调节有关的基因做出贡献。为了实现这一目标，我将首先将注意力集中在一组来自支链氨基酸的挥发物上。这类挥发物是影响番茄风味的最重要的物质之一，广泛存在于植物界。候选基因的鉴定将使用多方面的方法。首先，来自野生物种的导入系群体将被用来发现挥发性物质的数量性状基因座(QTL)。将对QTL进行精细定位，以发现相关基因。其次，将使用生物信息学分析来识别候选基因。第三种方法将使用一组不同的传家宝品种，重点研究基因表达和挥发性成分之间的相关性。一旦候选基因被确定，它们的功能将在PLANTA中进行评估。最后，将进行酶分析，以表征已鉴定的酶的体外活性。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。次生代谢中代谢流的调节越来越被认为是一个直接影响植物适合性和产量的重要课题。此外，这一研究计划的结果可能会对选择香气和风味更好的品种产生直接影响。商业品种通常被消费者认为风味差，而挥发性途径基因的鉴定是将传家宝风味重新引入现代品种的关键。

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.