title: Cytosolic monoterpene biosynthesis is supported by plastid-generated geranyl diphosphate substrate in transgenic tomato fruits.
abstract: Geranyl diphosphate (GPP), the precursor of most monoterpenes, is synthesized in plastids from dimethylallyl diphosphate and isopentenyl diphosphate by GPP synthases (GPPSs). In heterodimeric GPPSs, a non-catalytic small subunit (GPPS-SSU) interacts with a catalytic large subunit, such as geranylgeranyl diphosphate synthase, and determines its product specificity. Here, snapdragon (Antirrhinum majus) GPPS-SSU was over-expressed in tomato fruits under the control of the fruit ripening-specific polygalacturonase promoter to divert the metabolic flux from carotenoid formation towards GPP and monoterpene biosynthesis. Transgenic tomato fruits produced monoterpenes, including geraniol, geranial, neral, citronellol and citronellal, while exhibiting reduced carotenoid content. Co-expression of the Ocimum basilicum geraniol synthase (GES) gene with snapdragon GPPS-SSU led to a more than threefold increase in monoterpene formation in tomato fruits relative to the parental GES line, indicating that the produced GPP can be used by plastidic monoterpene synthases. Co-expression of snapdragon GPPS-SSU with the O. basilicum α-zingiberene synthase (ZIS) gene encoding a cytosolic terpene synthase that has been shown to possess both sesqui- and monoterpene synthase activities resulted in increased levels of ZIS-derived monoterpene products compared to fruits expressing ZIS alone. These results suggest that re-direction of the metabolic flux towards GPP in plastids also increases the cytosolic pool of GPP available for monoterpene synthesis in this compartment via GPP export from plastids.
authors.affiliation: Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Gutensohn
authors.forename: Irina
authors.initials: I
authors.lastname: Orlova
authors.forename: Thuong T H
authors.initials: TT
authors.lastname: Nguyen
authors.forename: Rachel
authors.initials: R
authors.lastname: Davidovich-Rikanati
authors.forename: Mario G
authors.initials: MG
authors.lastname: Ferruzzi
authors.forename: Yaron
authors.initials: Y
authors.lastname: Sitrit
authors.forename: Efraim
authors.initials: E
authors.lastname: Lewinsohn
authors.forename: Eran
authors.initials: E
authors.lastname: Pichersky
authors.forename: Natalia
authors.initials: N
authors.lastname: Dudareva
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics* / Q000378:metabolism; D032161:Antirrhinum / Q000235:genetics*; D003600:Cytosol / Q000378:metabolism; D011756:Diphosphates / Q000378:metabolism*; D004224:Diterpenes / Q000378:metabolism*; D005638:Fruit / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D051228:Geranyltranstransferase / Q000235:genetics / Q000378:metabolism; D018551:Solanum lycopersicum / Q000235:genetics* / Q000378:metabolism*; D000081222:Monocyclic Sesquiterpenes; D039821:Monoterpenes / Q000378:metabolism*; D018649:Ocimum basilicum / Q000235:genetics; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D018087:Plastids / Q000235:genetics / Q000378:metabolism; D011096:Polygalacturonase / Q000235:genetics; D011401:Promoter Regions, Genetic; D012717:Sesquiterpenes / Q000378:metabolism
chemical_list: D011756:Diphosphates; D004224:Diterpenes; D000081222:Monocyclic Sesquiterpenes; D039821:Monoterpenes; D012717:Sesquiterpenes; C511282:geranyl diphosphate; C477983:zingiberene; D019883:Alkyl and Aryl Transferases; C108877:terpene synthase; D051228:Geranyltranstransferase; D010744:Phosphoric Monoester Hydrolases; D011096:Polygalacturonase
keywords: Solanum lycopersicum; compartmentalization; geranyl diphosphate synthase; metabolic engineering; monoterpenes