title: The multiple phenylpropene synthases in both Clarkia breweri and Petunia hybrida represent two distinct protein lineages.
abstract: Many plants synthesize the volatile phenylpropene compounds eugenol and isoeugenol to serve in defense against herbivores and pathogens and to attract pollinators. Clarkia breweri flowers emit a mixture of eugenol and isoeugenol, while Petunia hybrida flowers emit mostly isoeugenol with small amounts of eugenol. We recently reported the identification of a petunia enzyme, isoeugenol synthase 1 (PhIGS1) that catalyzes the formation of isoeugenol, and an Ocimum basilicum (basil) enzyme, eugenol synthase 1 (ObEGS1), that produces eugenol. ObEGS1 and PhIGS1 both utilize coniferyl acetate, are 52% sequence identical, and belong to a family of NADPH-dependent reductases involved in secondary metabolism. Here we show that C. breweri flowers have two closely related proteins (96% identity), CbIGS1 and CbEGS1, that are similar to ObEGS1 (58% and 59% identity, respectively) and catalyze the formation of isoeugenol and eugenol, respectively. In vitro mutagenesis experiments demonstrate that substitution of only a single residue can substantially affect the product specificity of these enzymes. A third C. breweri enzyme identified, CbEGS2, also catalyzes the formation of eugenol from coniferyl acetate and is only 46% identical to CbIGS1 and CbEGS1 but more similar (>70%) to other types of reductases. We also found that petunia flowers contain an enzyme, PhEGS1, that is highly similar to CbEGS2 (82% identity) and that converts coniferyl acetate to eugenol. Our results indicate that plant enzymes with EGS and IGS activities have arisen multiple times and in different protein lineages.
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, University of Michigan, 830 North University Street, Ann Arbor, MI 48109-1048, USA.
authors.forename: Takao
authors.initials: T
authors.lastname: Koeduka
authors.forename: Gordon V
authors.initials: GV
authors.lastname: Louie
authors.forename: Irina
authors.initials: I
authors.lastname: Orlova
authors.forename: Christine M
authors.initials: CM
authors.lastname: Kish
authors.forename: Mwafaq
authors.initials: M
authors.lastname: Ibdah
authors.forename: Curtis G
authors.initials: CG
authors.lastname: Wilkerson
authors.forename: Marianne E
authors.initials: ME
authors.lastname: Bowman
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Baiga
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Noel
authors.forename: Natalia
authors.initials: N
authors.lastname: Dudareva
authors.forename: Eran
authors.initials: E
authors.lastname: Pichersky
mesh_terms: D000595:Amino Acid Sequence; D031663:Clarkia / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004798:Enzymes / Q000235:genetics / Q000378:metabolism*; D005054:Eugenol / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D035264:Flowers / Q000201:enzymology / Q000378:metabolism; D008969:Molecular Sequence Data; D015394:Molecular Structure; D032306:Petunia / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D010940:Plant Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D004798:Enzymes; D010940:Plant Proteins; D005054:Eugenol; C036643:isoeugenol