Plant Science 160 2160 129 – 137
Molecular and functional characterization of a rose lipoxygenase cDNA related to flower senescence
Masako Fukuchi-Mizutani
a,
, Kanako Ishiguro
b
, Toru Nakayama
b,c
, Yukiko Utsunomiya
b
, Yoshikazu Tanaka
a
, Takaaki Kusumi
a
, Takashi Ueda
b
a
Institute for Fundamental Research, Suntory Ltd.,
1
-
1
-
1
Wakayamadai, Shimamoto-cho, Mishima-gun, Osaka,
618
-
8503
Japan
b
Faculty of Nutrition, Kobe Gakuin Uni6ersity,
518
Arise, Ikawadani-cho, Nishi-ku, Kobe, Hyogo,
651
-
21
Japan
c
Department of Biochemistry and Engineering, Tohoku Uni6ersity,
07
Aoba Aza Aramaki, Aoba-ku, Sendai, Miyagi
980
-
8579
Japan Received 20 June 2000; received in revised form 28 August 2000; accepted 29 August 2000
Abstract
A cDNA encoding lipoxygenase, Rlox1, was isolated from a cDNA library of senescing rose petals using tomato lipoxygenase cDNA fragments as probes. Characterization of the Rlox1 protein expressed in Echerichia coli revealed that the Rlox1 protein was
a soluble lipoxygenase with an unusual optimal pH in the acidic region pH 4.5 – 5.0. Northern blot analysis showed that the transcript of the Rlox
1
gene was dramatically increased in response to senescence of rose petals. Treatment of rose flowers with ethylene also elevated the mRNA of the Rlox
1
gene. These results suggest that the Rlox1 lipoxygenase is involved in senescence of rose flowers. © 2000 Elsevier Science Ireland Ltd. All rights reserved.
Keywords
:
Rosa hybrida; Flower senescence; Lipoxygenase; Ethylene www.elsevier.comlocateplantsci
1. Introduction
Lipoxygenase EC 1. 13.11.12 occurs widely in higher plants and catalyzes the dioxygenation of
polyunsaturated fatty acids containing one or more cis, cis-1,4-pentadiene structures [1,2]. The
primary products of lipoxygenase-catalyzed reac- tions, fatty acid hydroxyperoxides, are further me-
tabolized into molecules functioning in many biological processes, such as plant growth regula-
tors, signal transduction molecules e.g., jas- monates, and compounds responsible for green
odor hexanals [3 – 5].
It has been reported that the expression of lipoxygenase genes is induced by stresses such as
insect feeding [6], pathogen infection [7 – 12], low water potential [13] and mechanical stress [6,14 –
18]. In addition, lipoxygenases are suggested to be involved in fruit ripening [19,20] and senescence of
vegetative or reproductive organs [21,22].
Many physiological and biochemical changes, including ethylene production and degradation of
cellular membranes, occur during flower senes- cence [23,24]. Rose is the most important cut
flower and it is critical to control senescence of rose flowers during postharvest. Although several
mechanistic studies on senescence of rose flowers have been reported [25 – 27], the molecular biology
of this process remains to be clarified. We started a program to study the molecular biology of de-
velopment and senescence of rose flowers, and found that a novel gene encoding a D9 fatty acid
desaturase homologue was induced specifically in rose petals after anthesis [28], indicating that fatty
acid metabolism plays an important role during rose flower development. It has been suggested
Corresponding author. Tel: + 81-75-9628807; fax: + 81-75- 9628262.
E-mail address
:
Masako –Mizutanisuntory.co.jp M. Fukuchi- Mizutani.
0168-945200 - see front matter © 2000 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0 1 6 8 - 9 4 5 2 0 0 0 0 3 7 3 - 3
that fatty
acid hydroxyperoxides
and their
metabolites play some role in flower senescence and the activity of lipoxygenase, the key enzyme
of hydroxyperoxidation of fatty acids, is elevated during senescence of carnation flowers [22].
Methyl jasmonate, a product of the octadecanoid pathway from the fatty acid hydroperoxide, has
been shown to promote senescence of petunia and dendrobium flowers [29]. Therefore, we decided to
investigate whether a lipoxygenase was involved in the senescence of rose flowers.
In this study, we have isolated a cDNA encod- ing a lipoxygenase isoform and found that this
cDNA is expressed in rose petals in response to senescence.
2. Materials and methods
