Regulation of Monoterpene Emission in Snapdragon Flowers

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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.