Nagegowda, Dinesh A. , Dudareva, Natalia .
Two nearly identical terpene synthases catalyze the formation of nerolidol and linalool in snapdragon flowers.
Terpenoids emitted from snapdragon flowers include three monoterpenes derived from geranyl diphosphate (GPP), myrcene, (E)-beta-ocimene, and linalool, and a sesquiterpene, nerolidol, derived from farnesyl diphosphate (FPP). Emission of these compounds is developmentally regulated and follows diurnal rhythms controlled by a circadian clock. Using a functional genomics approach, we have isolated and biochemically characterized two nearly identical nerolidol/linalool synthases, AmNES/LIS-1 and AmNES/LIS-2, the two remaining enzymes responsible for the terpenoid profile of snapdragon scent. AmNES/LIS-2 protein has an additional 30 amino acids in the N-terminus and shares 95% amino acid sequence identity with AmNES/LIS-1 with only 23 amino acid substitutions distributed across the homologous regions of the proteins. Although these two terpene synthases have very similar catalytic properties and synthesize linalool and nerolidol as sole products from GPP and FPP, respectively, they are compartmentally segregated. Green fluorescent protein localization studies and analysis of enzyme activities in purified leucoplasts together with our previous feeding experiments revealed that AmNES/LIS-1 is localized in cytosol and is responsible for nerolidol biosynthesis, while AmNES/LIS-2 has a plastid-targeting signal and accounts for the linalool formation. Thus, our results show that the subcellular localization of bifunctional enzymes and the availability of substrate determine the type and the level of product formed. By directing bifunctional enzymes to more than one cellular compartment plants extend the range of available substrates for enzyme utilization thus increasing the diversity of produced metabolites.
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1 - Purdue University, Department of Horticulture and Landscape Architecture
2 - Purdue University, Department of Horticulture and Landscape Architecture, West Lafayette, IN, 47907, USA
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM