Plant Molecular Biology 34: 89–97, 1997.
1997 Kluwer Academic Publishers. Printed in Belgium.
Ethylene biosynthetic genes are differentially expressed during carnation
(Dianthus caryophyllus L.) ﬂower senescence
Arjen ten Have
and Ernst J. Woltering
AgrotechnologicalResearch Institute (ATO-DLO), P.O. Box 17, 6700 AA Wageningen, Netherlands (
Present address: Department of Phytopathology, Wageningen Agricultural University,
P.O. Box 8025, 6700 EE Wageningen, Netherlands
Received 9 August 1996; accepted 4 February 1997
Key words: 1-aminocyclopropane-1-carboxylicacid (ACC) oxidase, ACC synthase, Dianthus caryophyllus, ethyl-
ene, ﬂower senescence, organ-speciﬁc gene expression
Ethylene production and expression patterns of an 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase
(CARAO1) and of two ACC synthase (EC 22.214.171.124) genes (CARACC3 and CARAS1) were studied in ﬂoral
organs of cut carnation ﬂowers (Dianthus caryophyllus L.) cv. White Sim. During the vase life and after treatment
of fresh ﬂowers with ethylene, production of ethylene and expression of ethylene biosynthetic genes ﬁrst started in
the ovary followed by the styles and the petals. ACC oxidase was expressed in all the ﬂoral organs whereas, during
the vase life, tissue-speciﬁc expression of the two ACC synthase genes was observed. After treatment with a high
ethyleneconcentration, tissue speciﬁcity of the two ACC synthase genes was lost and only a temporal difference in
expression remained. In styles, poor correlation between ethylene production and ACC synthase (CARAS1) gene
expression was observed suggesting that either activity is regulated at the translational level or that the CARAS1
gene product requires an additional factor for activity.
Isolated petals showed no increase in ethylene production and expression of ethylene biosynthetic genes when
excised from the ﬂower before the increase in petal ethylene production (before day 7); showed rapid cessation of
ethylene production and gene expression when excised during the early phase of petal ethylene production (day 7)
and showed a pattern of ethylene production and gene expression similar to the pattern observed in the attached
petals when isolated at day 8. The interorgan regulation of gene expression and ethylene as a signal molecule in
ﬂower senescence are discussed.
The gaseous plant hormone ethylene (C
involved in fruit ripening and ﬂower senescence. Fol-
lowingthe elucidationof thebiosynthetic pathway, the
enzymes involved have been isolated and character-
ized [6, 31]. The ﬁrst step in ethylene biosynthesis,
the conversion ofmethionineto S-adenosylmethionine
(SAM),iscatalyzedby SAM synthethase(EC126.96.36.199.)
step leading to the formation of ACC and is generally
regardedas being rate-limiting in ethylene biosynthes-
is . Oxidation of ACC by ACC oxidase, formerly
known as the ethylene forming enzyme, results in the
formation of ethylene, HCN and CO
. In the
past few years ACC synthase and ACC oxidase genes
have been cloned from a variety of plant species and
it has been shown that both enzymes are encoded by a
small gene family whose members are, in many cases,
expressed in a stimulus and organ-speciﬁc way [1, 9,
12, 16, 22].
In carnation ﬂowers, senescence is accompanied
by an increase in ethylene production and of ACC
synthase and ACC oxidase activities in petals [e.g.
26, 30]. The produced ethylene is thought to initiate
the biochemical changes leading to petal senescence.
In these ﬂowers two cDNAs encoding ACC synthase
have been identiﬁed to date. Initially CARACC3 was
GR: 201001903, Pips nr. 134273 BIO2KAP
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