Poster: Late and Moved Abstracts

Abs # 954: Regulation of monoterpene formation after pollination in snapdragon flowers.

Presenter:	Orlova, Irina
Authors	Orlova, Irina  (A)   Negre, Florence  (A)   Tholl, Dorothea  (B)   Kish, Christine M (A)   Bohlmann, Jorg  (C)   Gershenzon, Jonathan  (B)   Dudareva, Natalia  (A)
Affiliations:	(A): Purdue University, West Lafayette, IN (B): Max Plank Institute for Chemical Ecology, D-007745 Jena, Germany (C): University of British Columbia, Vancouver, B.C. Canada V6T 1Z3

The scent of snapdragon flowers is rich in the monoterpene compounds myrcene and (E)-β-ocimene, which are derived from geranyl diphosphate (GPP, C₁₀), a product of condensation of dimethylallyl diphosphate and isopentenyl diphosphate in a reaction catalyzed by GPP synthase (GPPS). Using a functional genomic approach we have isolated and characterized cDNAs from a snapdragon petal-specific library which encode myrcene synthase, an (E)-β-ocimene synthase, and a small (GPPS.SSU) and large (GPPS.LSU) subunits of GPP synthase. Analyses of tissue-specific, developmental, and rhythmic changes in the mRNA and protein levels of GPPS.SSU in snapdragon flowers revealed that GPPS.SSU might play a key role in regulating the formation of GPPS, and thus monoterpene biosynthesis. A 70-75% pollination-induced decrease in emission of myrcene and (E)-β-ocimene begins only after pollen tubes reach the ovary, a process which takes between 35 and 40 h. To determine the molecular mechanisms responsible for post-pollination changes in monoterpene emission, we analyzed monoterpene synthase gene expression and activity and found that while their expression did not decrease after pollination, their activities dropped significantly indicating that posttranslation modification is involved in the regulation of scent production after pollination. The expression of small and large subunits of GPPS, as well as the expression of 1-deoxy-D-xylulose-5-phosphate synthase (DXS) which is responsible for the condensation of pyruvate and glyceraldehydes 3-phosphate, the first step in the methyl-erythritol-phosphate (MEP) pathway, were also analyzed and their involvement in the regulation of postpollination changes are discussed. This work is supported by NSF grant MCB-0212802.