Circadian regulation of the PhCCD1 carotenoid cleavage dioxygenase controls emission of beta-ionone, a fragrance volatile of petunia flowers.
Carotenoids are thought to be the precursors of terpenoid volatile compounds that contribute to flavor and aroma. One such volatile, beta-ionone, is important to fragrance in many flowers, including petunia (Petunia hybrida). However, little is known about the factors regulating its synthesis in vivo. The petunia genome contains a gene encoding a 9,10(9',10') carotenoid cleavage dioxygenase, PhCCD1. The PhCCD1 is 94% identical to LeCCD1A, an enzyme responsible for formation of beta-ionone in tomato (Lycopersicon esculentum; Simkin AJ, Schwartz SH, Auldridge M, Taylor MG, Klee HJ [2004] Plant J [in press]). Reduction of PhCCD1 transcript levels in transgenic plants led to a 58% to 76% decrease in beta-ionone synthesis in the corollas of selected petunia lines, indicating a significant role for this enzyme in volatile synthesis. Quantitative reverse transcription-PCR analysis revealed that PhCCD1 is highly expressed in corollas and leaves, where it constitutes approximately 0.04% and 0.02% of total RNA, respectively. PhCCD1 is light-inducible and exhibits a circadian rhythm in both leaves and flowers. beta-Ionone emission by flowers occurred principally during daylight hours, paralleling PhCCD1 expression in corollas. The results indicate that PhCCD1 activity and beta-ionone emission are likely regulated at the level of transcript.
Simkin
Andrew J
AJ
Horticultural Sciences, Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, Florida 32611-0690, USA.
Underwood
Beverly A
BA
Auldridge
Michele
M
Loucas
Holly M
HM
Shibuya
Kenichi
K
Schmelz
Eric
E
Clark
David G
DG
Klee
Harry J
HJ
D000595:Amino Acid Sequence; D002940:Circadian Rhythm; D049308:Dioxygenases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D035264:Flowers / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D008027:Light; D008969:Molecular Sequence Data; D045792:Norisoprenoids / Q000096:biosynthesis*; D030781:Organisms, Genetically Modified; D032306:Petunia / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D045792:Norisoprenoids; C008157:beta-ionone; D049308:Dioxygenases; C431939:carotenoid cleavage dioxygenase 1