Volatile ester formation in roses. Identification of an acetyl-coenzyme A. Geraniol/Citronellol acetyltransferase in developing rose petals.
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.
Shalit
Moshe
M
Department of Vegetable Crops, Newe Ya'ar Research Center, Agricultural Research Organization, P.O. Box 1021, Ramat Yishay 30095, Israel.
Guterman
Inna
I
Volpin
Hanne
H
Bar
Einat
E
Tamari
Tal
T
Menda
Naama
N
Adam
Zach
Z
Zamir
Dani
D
Vainstein
Alexander
A
Weiss
David
D
Pichersky
Eran
E
Lewinsohn
Efraim
E
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*
D000080462:Acyclic Monoterpenes; D004952:Esters; D039821:Monoterpenes; D009822:Oils, Volatile; D012333:RNA, Messenger; D013729:Terpenes; D000123:Acetyltransferases; C007836:geraniol; C007078:citronellol