Molecular Genetics of Flower Scents

9417582皮切斯基花香对植物繁殖成功有很大影响，因此是果树产量的关键决定因素，需要寻找气味传粉者。然而，鲜有人在生化、遗传和分子水平上对花香的生物合成途径进行研究。皮切斯基博士建议研究原产于加利福尼亚州的一年生植物克拉其香气的产生。短冠天蛾(Clarkia Breweri)是该属中唯一有花香的物种；其花朵主要由鹰蛾访问。Concinna是一种近缘关系很近的物种，它的无味花朵主要是由蝴蝶访问的，而所有其他异交的clarkia物种都是由蜜蜂授粉。这位研究人员已经确定了促成酿酒酵母花香的两条主要途径。其中一个途径，也就是本正文的主题，导致了单萜芳樟醇和芳樟醇氧化物的产生。已有研究表明，这一途径也适用于Concinna花，尽管水平大大降低，因此似乎是通过上调这一途径发生了酿酒花中单萜释放的进化。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芳樟醇合成酶(Lis)的酶分析方法，并提纯了这种蛋白质。芳樟醇合成酶是一种催化形成芳樟醇的酶。他们现在将开发一种芳樟醇环氧化物(LIE)的分光光度分析方法，这种酶催化形成6，7-芳樟醇环氧化物，芳樟醇氧化物是形成芳樟醇氧化物的中间体。他们将利用重组启动子-GUS报告基因融合、植物转化和DNA-蛋白质相互作用分析，分离和鉴定这两个克氏杆菌物种的LIS和LIE基因，并研究控制它们表达的遗传和分子控制机制以及导致种间差异的原因。这些酶的细胞和亚细胞定位将使用免疫学技术的组合来确定。获得的数据将增加我们对花香产生的生化和遗传控制的理解，并可能导致未来在重要的农艺植物中操纵这些特征的能力。

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.