Plant Science 154 2000 61 – 69
Differential expression of plastidic aldolase genes in Nicotiana plants under salt stress
Shigehiro Yamada , Toshiyuki Komori, Akiko Hashimoto, Shigeru Kuwata, Hidemasa Imaseki, Tomoaki Kubo
Plant Breeding and Genetics Research Laboratory, Japan Tobacco Inc.,
700
Higashibara, Toyoda-cho, Iwata-gun, Shizuoka
438
-
0802
, Japan Received 18 May 1999; received in revised form 14 December 1999; accepted 20 December 1999
Abstract
Two homologous genes of plastidic fructose-1,6-bisphosphate aldolase AldP isozymes were isolated from green leaves of a salt stress-tolerant Nicotiana species, Nicotiana paniculata, by differential screening. The products of the corresponding genes,
NpAldP
1
and NpAldP
2
, were 91 identical to each other and 70 – 85 identical to the other known plant plastidic aldolases. Although these two genes showed similar organ-specific expression and daily cycles, their responses to salt stress differed: mRNA
accumulation of NpAldP
2
increased, but that of NpAldP
1
slightly decreased. The mRNA accumulations of their counterparts of two other Nicotiana species, NeAldP
1
and NeAldP
2
Nicotiana excelsior, and NaAldP
1
and NaAldP
2
Nicotiana arentsii were studied under the same stress condition. N. arentsii conserved accumulation profiles similar to N. paniculata, but N. excelsior did
not. In N. excelsior, accumulation of NeAldP
1
decreased to 50 of the control after stress and gradually recovered thereafter, whereas accumulation of NeAldP
2
temporarily decreased and reached 250 of the control by the third day of stress. Southern blot analysis indicated that NpAldP
1
, NpAldP
2
, NaAldP
1
, and NaAldP
2
include one or two closely related genes and NeAldP
1
and NeAldP
2
several. © 2000 Elsevier Science Ireland Ltd. All rights reserved.
Keywords
:
Nicotiana; Salt stress; Aldolase www.elsevier.comlocateplantsci
1. Introduction
Environmental stresses often strongly affect crop production, and improvement in plant ability
to tolerate such stresses is one of the most impor- tant objectives in plant science. Water-deficit
stress, which is mainly due to high salinity andor drought, is one of the most common stresses.
Several groups have achieved this mainly by intro- ducing foreign genes into host plants to enhance
osmoprotectant productions; however, the effects were limited [1 – 4]. Therefore, introduction of mul-
tiple mechanisms is assumed essential to confer extensive stress tolerance. To find novel stress-tol-
erance mechanisms, the authors have been investi- gating the response of Nicotiana species to
water-deficit stress. Plants in this genus are not classified as halophytic plants, but some of their
native habitats are harsh, either dry or salty. A total of 57 Nicotiana species were screened for
water-deficiency tolerance, and Nicotiana panicu- lata and Nicotiana excelsior were found to be
water-deficit stress-tolerant. These species can grow as well as unstressed plants even under the
salt stress imposed by 250 mM NaCl Komori, submitted. The Nicotiana species also contain
stress-sensitive species, such as Nicotiana arentsii. This species shows slow growth under the same
conditions Komori, submitted. To elucidate stress-tolerance mechanisms of these species using
the molecular approach, differential screening was
Corresponding author. Tel.: + 81-538-327111; fax: + 81-538- 336046.
E-mail address
:
shigehiro.yamadaorynova.co.jp S. Yamada 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 1 8 8 - 6
attempted and it succeeded in isolating stress-in- ducible genes from those species. Among the cD-
NAs obtained from the green leaves of N. paniculata, two clones were found with a homol-
ogy to plastidic fructose-1,6-bisphospate aldolase AldP genes.
AldP catalyzes the cleavage of fructose-1,6-bis- phosphate FBP into
D
-glyceraldehyde-3-phos- phate GAP and dihydroxyacetone phosphate
DHAP. Two forms of aldolase are present in higher plants: cytoplasmic and plastidic. The cy-
toplasmic aldolase AldC gene is inducible un- der anaerobic conditions and is considered to
have an important role in producing ATP by stimulating glycolysis under such conditions [5 –
9]. AldP is involved in the photosynthetic carbon reduction cycle and catalyzes the synthesis of
FBP from GAP and DHAP. AldP gene expres- sion is regulated by light [10], but the effect of
other environmental factors on AldP is nu- known. Here, the isolation of two AldP genes
from a salt-tolerant Nicotiana species, N. panicu- lata is reported and their expression regulation
among three Nicotiana species are compared with different salt-tolerance abilities under salt
stress.
2. Materials and methods
