Molecular Genetics of Flower Scents

花的气味对植物的繁殖成功有很强的影响，因此是需要气味寻找传粉者的水果作物产量的关键决定因素。然而，对花香的生物合成途径在生物化学、遗传和分子水平上的研究却很少。皮切尔斯基博士建议研究加州原生一年生植物克拉基亚（Clarkia）的气味产生。Clarkia breweri是该属中唯一具有花香的物种；它的花主要是由蛾子访问的。C. concinna是啤酒酵母的近亲，其无臭的花主要由蝴蝶来拜访，而所有其他异交的克氏菌都是由蜜蜂授粉的。研究人员已经确定了两种主要的途径，有助于啤酒厂啤酒的花香。这些途径之一，本提案的主题，导致生产单萜烯芳樟醇和芳樟醇氧化物。研究表明，这一途径在啤酒花中也起作用，尽管水平大大降低，因此啤酒花中单萜释放的进化似乎是通过上调这一途径发生的。为了验证这一假设，皮切斯基博士和他的同事们已经开发了一种酶分析法来检测芳樟醇合成酶（LIS），这种酶催化芳樟醇的形成，并纯化了这种蛋白质。他们现在将开发一种分光光度法测定环氧芳樟醇（LIE），这种酶催化6,7-芳樟醇氧化的形成，是芳樟醇氧化物形成的中间体。他们将利用重组启动子- GUS报告基因融合、植物转化和dna -蛋白相互作用等方法，从两个克氏菌中分离和鉴定Lis和Lie基因，并研究其表达和种间差异的遗传和分子控制机制。酶的细胞和亚细胞定位将使用免疫学技术的组合来确定。所获得的数据将增加我们对花香味产生的生化和遗传控制的理解，并可能导致未来在农艺上重要的植物中操纵这些性状的能力。

9417582 Pichersky Flower scents exert strong influence on plant reproductive success, and thus are crucial determinants of yield in fruit crops that require scent-seeking pollinators. However, the biosynthetic pathways of floral scents have scarcely been investigated on the biochemical, genetic and molecular levels. Dr. Pichersky proposes to study scent production in Clarkia, a genus of annual plants native to California. Clarkia breweri is the only species in the genus with floral scent; its flowers are visited mostly by hawkmoths. The odorless flowers of C. concinna, a closely related species from which C. breweri arose, are visited mostly by butterflies, whereas all other outcrossing Clarkia species are pollinated by bees. The investigator has identified two major pathways that contribute to the floral scent of C. breweri. One of these pathways, the subject of this propoal, results in the production of the monoterpenes linalool and linalool oxides. It has been shown that this pathway also operates in C. Concinna flowers as well, albeit at a greatly reduced level, and it therefore appears that the evolution of monoterpene emission in C. breweri has occurrred by up- regulating this pathway. To test this hypothesis, Dr. Pichersky and his colleagues have already developed an enzymatic assay for linalool synthase (LIS), the enzyme that catalyzes the formation of linalool, and have purified the protein. They will now develop a spectrophotometric assay for linalool epoxidae (LIE), the enzyme that catalyzes the formation of 6,7-linalool expoxide, an intermediate in the formation of linalool oxides. They will isolate and characterize the Lis and Lie genes from both Clarkia species and investigate the genetic and molecular control mechanisms that govern their expression and are responsible for the interspecific differences, using recombinant promoter - GUS reporter gene fusion and plant transforation and DNA-protein interaction assays. The cellular and subce llular localization of the enzymes will be determined using a combination of immunological techniques. The data obtained will increase our understanding of the biochemical and genetic control of flower scent production, and may lead to future ability to manipulate these traits in agronomically important plants.