title: Volatile ester formation in roses. Identification of an acetyl-coenzyme A. Geraniol/Citronellol acetyltransferase in developing rose petals.
abstract: The aroma of roses (Rosa hybrida) is due to more than 400 volatile compounds including terpenes, esters, and phenolic derivatives. 2-Phenylethyl acetate, cis-3-hexenyl acetate, geranyl acetate, and citronellyl acetate were identified as the main volatile esters emitted by the flowers of the scented rose var. "Fragrant Cloud." Cell-free extracts of petals acetylated several alcohols, utilizing acetyl-coenzyme A, to produce the corresponding acetate esters. Screening for genes similar to known plant alcohol acetyltransferases in a rose expressed sequence tag database yielded a cDNA (RhAAT1) encoding a protein with high similarity to several members of the BAHD family of acyltransferases. This cDNA was functionally expressed in Escherichia coli, and its gene product displayed acetyl-coenzyme A:geraniol acetyltransferase enzymatic activity in vitro. The RhAAT1 protein accepted other alcohols such as citronellol and 1-octanol as substrates, but 2-phenylethyl alcohol and cis-3-hexen-1-ol were poor substrates, suggesting that additional acetyltransferases are present in rose petals. The RhAAT1 protein is a polypeptide of 458 amino acids, with a calculated molecular mass of 51.8 kD, pI of 5.45, and is active as a monomer. The RhAAT1 gene was expressed exclusively in floral tissue with maximum transcript levels occurring at stage 4 of flower development, where scent emission is at its peak.
authors.affiliation: Department of Vegetable Crops, Newe Ya'ar Research Center, Agricultural Research Organization, P.O. Box 1021, Ramat Yishay 30095, Israel.
authors.forename: Moshe
authors.initials: M
authors.lastname: Shalit
authors.forename: Inna
authors.initials: I
authors.lastname: Guterman
authors.forename: Hanne
authors.initials: H
authors.lastname: Volpin
authors.forename: Einat
authors.initials: E
authors.lastname: Bar
authors.forename: Tal
authors.initials: T
authors.lastname: Tamari
authors.forename: Naama
authors.initials: N
authors.lastname: Menda
authors.forename: Zach
authors.initials: Z
authors.lastname: Adam
authors.forename: Dani
authors.initials: D
authors.lastname: Zamir
authors.forename: Alexander
authors.initials: A
authors.lastname: Vainstein
authors.forename: David
authors.initials: D
authors.lastname: Weiss
authors.forename: Eran
authors.initials: E
authors.lastname: Pichersky
authors.forename: Efraim
authors.initials: E
authors.lastname: Lewinsohn
mesh_terms: D000123:Acetyltransferases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D000080462:Acyclic Monoterpenes; D000595:Amino Acid Sequence; D004952:Esters / Q000378:metabolism*; D035264:Flowers / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D007700:Kinetics; D008969:Molecular Sequence Data; D015394:Molecular Structure; D039821:Monoterpenes / Q000378:metabolism*; D009812:Odorants; D009822:Oils, Volatile / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D027826:Rosa / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D017385:Sequence Homology; D013379:Substrate Specificity; D013729:Terpenes / Q000378:metabolism*
chemical_list: D000080462:Acyclic Monoterpenes; D004952:Esters; D039821:Monoterpenes; D009822:Oils, Volatile; D012333:RNA, Messenger; D013729:Terpenes; D000123:Acetyltransferases; C007836:geraniol; C007078:citronellol