Ethylene-regulated floral volatile synthesis in petunia corollas.
In many flowering plants, such as petunia (Petunia x hybrida), ethylene produced in floral organs after pollination elicits a series of physiological and biochemical events, ultimately leading to senescence of petals and successful fertilization. Here, we demonstrate, using transgenic ethylene insensitive (44568) and Mitchell Diploid petunias, that multiple components of emission of volatile organic compounds (VOCs) are regulated by ethylene. Expression of benzoic acid/salicylic acid carboxyl methyltransferase (PhBSMT1 and 2) mRNA is temporally and spatially down-regulated in floral organs in a manner consistent with current models for post-pollination ethylene synthesis in petunia corollas. Emission of methylbenzoate and other VOCs after pollination and exogenous ethylene treatment parallels a reduction in PhBSMT1 and 2 mRNA levels. Under cyclic light conditions (day/night), PhBSMT mRNA levels are rhythmic and precede emission of methylbenzoate by approximately 6 h. When shifted into constant dark or light conditions, PhBSMT mRNA levels and subsequent methylbenzoate emission correspondingly decrease or increase to minimum or maximum levels observed during normal conditions, thus suggesting that light may be a more critical influence on cyclic emission of methylbenzoate than a circadian clock. Transgenic PhBSMT RNAi flowers with reduced PhBSMT mRNA levels show a 75% to 99% decrease in methylbenzoate emission, with minimal changes in other petunia VOCs. These results implicate PhBSMT1 and 2 as genes responsible for synthesis of methylbenzoate in petunia.
Underwood
Beverly A
BA
Department of Environmental Horticulture, University of Florida, Gainesville, Florida 32611, USA.
Tieman
Denise M
DM
Shibuya
Kenichi
K
Dexter
Richard J
RJ
Loucas
Holly M
HM
Simkin
Andrew J
AJ
Sims
Charles A
CA
Schmelz
Eric A
EA
Klee
Harry J
HJ
Clark
David G
DG
D005030:Ethylenes / Q000494:pharmacology*; D035264:Flowers / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D007700:Kinetics; D008969:Molecular Sequence Data; D032306:Petunia / Q000502:physiology*; D010937:Plant Growth Regulators / Q000494:pharmacology; D011058:Pollen / Q000502:physiology
D005030:Ethylenes; D010937:Plant Growth Regulators; C036216:ethylene