Regulation of Monoterpene Emission in Snapdragon Flowers

花香通过吸引传粉者到花上，在高等植物的生殖周期中起着至关重要的作用。这项研究的长期目标是填补我们在导致植物挥发物形成的生化途径以及控制其积累和释放的分子机制方面的重要空白。单萜烯是天然萜类化合物家族的C10成员，是非常常见的花香成分，但对花组织如何调节其发育和节律性释放知之甚少。本项目将重点研究单萜生物合成的关键前体香叶基焦磷酸（GPP）在调节反式-b-辛烯和月桂烯两种主要气味成分的发育和节律性释放中的作用。GPP是由二磷酸二甲基烯丙基和二磷酸异戊烯基（IPP）在GPP合成酶（GPPS）催化下缩合而成的产物，是许多单萜烯终产物合成的起点。植物细胞有两种不同的IPP生物合成途径，分别位于两个不同的区室中。将阐明导致金鱼龙花瓣组织中GPP生物合成的生化途径，并研究通过细胞质和塑性IPP池之间的交换，一种途径被另一种途径补偿的可能性。与其他同二聚体短链戊烯基转移酶相比，GPPS是一种功能性异二聚体，其酶活性绝对需要大小亚基。本项目将对骁龙GPPS基因家族的复杂性进行表征，分析GPPS的两个亚基在细胞中调控GPP量的作用，确定亚细胞定位在调控GPPS活性中的作用。花香在农作物经济中扮演着重要的角色，因为我们三分之一的饮食依赖于昆虫授粉的植物，包括大多数果树、浆果、坚果、油籽和蔬菜。授粉不仅影响作物产量，而且影响作物生产的质量和效益。本研究将对高等植物花香产生的调控有新的认识，也将为提高植物香气质量的工程植物提供知识。这可能会增加花对某些传粉媒介的吸引力，并导致为其种子、饲料或食物价值而种植的作物植物更有效地授粉。

Floral scent plays a vital role in the reproductive cycle of higher plants by attracting pollinators to flowers. The long-term goal of this research is to fill important gaps in our knowledge of biochemical pathways leading to the formation of floral volatiles and the molecular mechanisms controlling their accumulation and release in plants. Although monoterpenes, the C10 members of the terpenoid family of natural products, are very common constituents of floral scent, little is known about how floral tissues regulate their developmental and rhythmic emission. This project will focus on investigation of the role of geranyl pyrophosphate (GPP), the key precursor of monoterpene biosynthesis, in the regulation of developmental and rhythmic emission of trans-b-ocimene and myrcene, the two major scent components of snapdragon scent. GPP, the starting point leading to the synthesis of many monoterpene end products, is the result of condensation of dimethylallyl diphosphate and isopentenyl diphosphate (IPP) in a reaction catalyzed by GPP synthase (GPPS). Plant cells have two different IPP biosynthetic pathways located in two different compartments. Biochemical pathway(s) leading to GPP biosynthesis in snapdragon petal tissue will be elucidated and the possibility of compensation of one pathway by the other one through the exchange between cytosolic and plastidic IPP pools will be examined. In contrast to other homodimeric short-chain prenyltransferases, GPPS is a functional heterodimer in which small and large subunits are absolutely required for enzymatic activity. In this project, the complexity of the GPPS gene family in snapdragon will be characterized, the role of both subunits of GPPS in the regulation of the amount of GPP in cells will be analyzed and the involvement of subcellular localization in the regulation of GPPS activity will be determined. Floral scent plays an important role in the crop economy since one-third of our total diet depends upon insect-pollinated plants including most fruit trees, berries, nuts, oilseeds, and vegetables. Pollination not only affects crop yield but also quality and efficiency of crop production. This research will result in new insights into the regulation of floral scent production in higher plants and also provide the knowledge for engineering plants with improved scent quality. This could increase the attraction of flowers to certain pollinators and lead to the more efficient pollination of crop plants cultivated for their seed, forage, or food value.