(E)-beta-ocimene and myrcene synthase genes of floral scent biosynthesis in snapdragon: function and expression of three terpene synthase genes of a new terpene synthase subfamily.
Snapdragon flowers emit two monoterpene olefins, myrcene and (E)-beta-ocimene, derived from geranyl diphosphate, in addition to a major phenylpropanoid floral scent component, methylbenzoate. Emission of these monoterpenes is regulated developmentally and follows diurnal rhythms controlled by a circadian clock. Using a functional genomics approach, we have isolated and characterized three closely related cDNAs from a snapdragon petal-specific library that encode two myrcene synthases (ama1e20 and ama0c15) and an (E)-beta-ocimene synthase (ama0a23). Although the two myrcene synthases are almost identical (98%), except for the N-terminal 13 amino acids, and are catalytically active, yielding a single monoterpene product, myrcene, only ama0c15 is expressed at a high level in flowers and contributes to floral myrcene emission. (E)-beta-Ocimene synthase is highly similar to snapdragon myrcene synthases (92% amino acid identity) and produces predominantly (E)-beta-ocimene (97% of total monoterpene olefin product) with small amounts of (Z)-beta-ocimene and myrcene. These newly isolated snapdragon monoterpene synthases, together with Arabidopsis AtTPS14 (At1g61680), define a new subfamily of the terpene synthase (TPS) family designated the Tps-g group. Members of this new Tps-g group lack the RRx(8)W motif, which is a characteristic feature of the Tps-d and Tps-b monoterpene synthases, suggesting that the reaction mechanism of Tps-g monoterpene synthase product formation does not proceed via an RR-dependent isomerization of geranyl diphosphate to 3S-linalyl diphosphate, as shown previously for limonene cyclase. Analyses of tissue-specific, developmental, and rhythmic expression of these monoterpene synthase genes in snapdragon flowers revealed coordinated regulation of phenylpropanoid and isoprenoid scent production.
Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana 47907, USA. dudareva@hort.purdue.edu
Natalia
N
Dudareva
Diane
D
Martin
Christine M
CM
Kish
Natalia
N
Kolosova
Nina
N
Gorenstein
Jenny
J
Fäldt
Barbara
B
Miller
Jörg
J
Bohlmann
D000080462:Acyclic Monoterpenes; D000475:Alkenes / Q000378:metabolism*; D019883:Alkyl and Aryl Transferases / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D032161:Antirrhinum / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins; D002940:Circadian Rhythm / Q000502:physiology; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D035264:Flowers / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D019753:Intramolecular Lyases / Q000235:genetics* / Q000378:metabolism; D008027:Light; D008969:Molecular Sequence Data; D039821:Monoterpenes / Q000378:metabolism*; D005810:Multigene Family / Q000235:genetics; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
D000080462:Acyclic Monoterpenes; D000475:Alkenes; D029681:Arabidopsis Proteins; D018076:DNA, Complementary; D039821:Monoterpenes; D010940:Plant Proteins; C008574:beta-myrcene; C443996:beta-ocimene; D019883:Alkyl and Aryl Transferases; C108877:terpene synthase; D019753:Intramolecular Lyases; C108134:TPS10 protein, Arabidopsis