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2nd International e-Conference on Agricultural Biosciences 2009
Conference website: http://www.e-conference.elewa.org/agriculture
Drought is one of the major ecological factors limiting crop
production and food quality globally, especially in the arid and
semi-arid areas of the world.
Among crop plants, wheat (Triticum aestivum), which often
experiences water-limited conditions, is an attractive study
system because of the natural genetic variation in traits
related to drought tolerance (Loggini et al., 1999).
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2nd International e-Conference on Agricultural Biosciences 2009
Conference website: http://www.e-conference.elewa.org/agriculture
Extreme environmental conditions that induce oxidative stress
have been associated to an increased carbonyl groups content
and to an induction in protease activity.
Objective:
The objective of the present study was to investigate mechanisms
responsible for acclimatization to drought in two wheat cultivars, Veery
(drought tolerant) and Sids-1 (drought susceptible) subjected to two
drought
phases
interrupted
by
2d
re-watering
period.
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2nd International e-Conference on Agricultural Biosciences 2009
Conference website: http://www.e-conference.elewa.org/agriculture
7/31/2017
For these purposes the glutathione system of the tissue and its
relation to protein synthesis was investigated in both cultivars
upon dehydration and rehydration. Also to understand the role
of
proteolysis
in
the
response
stress.
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2nd International e-Conference on Agricultural Biosciences 2009
Conference website: http://www.e-conference.elewa.org/agriculture
to
drought
2nd International e-Conference on Agricultural Biosciences 2009
Conference website: http://www.e-conference.elewa.org/agriculture
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7/31/2017
Two wheat (T. aestivum L.) cultivars, namely
Veery (drought tolerant) and Sids-1 (drought
susceptible) were used in this study for:
Estimation of Relative Water Content (RWC)
Determination of Oxidative stress indices
(protein oxidation)
Glutathione determination
Glutathione reductase (GR) assay
Measurement of azocaseinolytic activity
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2nd International e-Conference on Agricultural Biosciences 2009
Conference website: http://www.e-conference.elewa.org/agriculture
7/31/2017
Cont. Sids
AA
Cv Sids 1 Cont. Veery
* *
*
*
60
(%)
Cv Veery
*
*
80
*
*
*
*
*
*
*
40
*
20
0
Carbonyl group content (%)
Relative water content
100
200
B
150
* *
*
* *
*
*
*
*
* *
* *
100
*
*
50
0
0
4
8
2 Rew
First drought phase
4
8
12
Fig. (1): relative water content (%) (A)
and Carbonyl group content (B) of well
watered and drought stressed wheat
cultivars CV Sids-1 (sensitive) and CV
Veery (Tolerant) subjected to two
drought phases interrupted by 2d rewatering. Each value represents the
mean ±SE of five replicates. Cont. Sids-1
= Control of sensitive cultivar; cv Sids-1=
drought stressed sensitive cultivar, Cont.
Veery; Control of tolerant cultivar, Cv
Veery; drought stressed tolerant cultivar,
2 Rew; 2 days rewatring. Significant
differences (P<0.05) between treatments
according to LSD test are shown by an
asterisk.
Second drought phase
Treatments (d)
Fig. (1 ):
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2nd International e-Conference on Agricultural Biosciences 2009
Conference website: http://www.e-conference.elewa.org/agriculture
7/31/2017
Fig. (2) Changes in glutathione status, GSH,
GSSG and GSG/GSSG ratio in wheat cultivars
cv sids-1 and cv Veery exposed to two
drought cycles interrupted by 2d re-watering
(2Rew). Each value represents the mean ±SE
of five replicates. Cont. Sids-1; Control of
sensitive cultivar, cv Sids-1; drought stressed
sensitive cultivar, Cont. Veery; Control of
tolerant cultivar,
Cv
Veery; drought stressed
tolerant cultivar, 2 Rew; 2 days re-watering.
Significant
differences
(P<0.05)
between
treatments according to LSD test are shown
by an asterisk.
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2nd International e-Conference on Agricultural Biosciences 2009
Conference website: http://www.e-conference.elewa.org/agriculture
25
*
*
GR
(U/mg protein)
20
*
*
15
*
*
*
*
*
* *
10
5
0
2
4
8
2 Rew
First drought phase
4
8
12
*
Fig. 3 : Glutathione reductase (GR)
activity of well watered and drought
stressed wheat cultivars CvSids-1 and
Cv Veery subjected to two drought
phases interrupted by 2d re-watering.
Each value represents the mean ±SE
of five replicates. Cont. Sids-1;
Control of sensitive cultivar, cv Sids-1;
drought stressed sensitive cultivar,
Cont. Veery; Control of tolerant
cultivar, Cv Veery; drought stressed
tolerant cultivar, 2 Rew; 2 days
rewatring.
Significant differences
(P<0.05)
between
treatments
according to LSD test are shown by an
asterisk.
Second drought phase
Treatments (d)
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2nd International e-Conference on Agricultural Biosciences 2009
Conference website: http://www.e-conference.elewa.org/agriculture
Cont. Sids
100
Cv Sids 1
Cont. Veery
A
80
* *
Total soluble protein
mg g-1 DW
A
Azocasinolytic activity
unitsmg -1protein h-1
Cv Veery
60
*
*
*
*
*
*
*
40
*
20
0
10
8
6
4
B
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
* *
*
*
*
*
2
0
2
4
8
First drought phase
2 Rew
Fig. (4): Total protein content (A) and
Azocaseinolytic activity (B) of well
watered and drought stressed wheat
cultivars CV Sids-1 (sensitive) and CV
Veery (tolerant) subjected to two
drought phases interrupted by 2d
re-watering. Each value represents
the mean ±SE of five replicates.
Cont. Sids-1; Control of sensitive
cultivar, cv Sids-1; drought stressed
sensitive cultivar, Cont. Veery;
Control of tolerant cultivar, Cv Veery;
drought stressed tolerant cultivar, 2
Rew; 2 days rewatring. Significant
differences
(P<0.05)
between
treatments according to LSD test are
shown by an asterisk.
4
8
12
Second drought phase
Treatments (d)
2nd International e-Conference on Agricultural Biosciences 2009
website: http://www.e-conference.elewa.org/agriculture
14 protein content (A)Conference
and Azocasinolytic activity (B) of well watered and
Fig. (3): Total
drought stressed wheat cltivars CV sids (sensitive) and CV veery ( Tolerant) subjected to
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A significant increase of carbonyl concentration in response to drought
stress in both cultivars tested and after prolonged drought stress,
indicating the presence of oxidized protein which are selectively
recognized and degraded by proteolytic enzymes (Fig.1B)
The ratio of GSH to GSSG was directly related to the level of drought
stress, however, after 2d re-watering, the acclimatized wheat leaves
for both cultivars showed higher values at the end of the second
drought phase when compared to the results obtained after the
completion of the first drought phase (Fig. 2C).
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2nd International e-Conference on Agricultural Biosciences 2009
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7/31/2017
The high activity of GR, especially during the first drought phase,
maintained glutathione pool in its reduced status. This is
confirmed by the different behavior of cultivars, in which a relative
low GR activity, also at high degree of drought, was associated
with low GSH and high GSSG levels (Fig. 2 A, B and Fig. 3).
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2nd International e-Conference on Agricultural Biosciences 2009
Conference website: http://www.e-conference.elewa.org/agriculture
Lower azocaseinolytic activity was referred to cultivar type in
order of increasing drought stress and associated with a distinct
reduction of soluble protein content in the wheat leaves.
Drought
has been associated with decreased protein levels,
increased proteolytic activity, and the up-regulation of cysteine
protease genes (reviewed in Beers et al., 2004).
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2nd International e-Conference on Agricultural Biosciences 2009
Conference website: http://www.e-conference.elewa.org/agriculture
The recent literature confirms a central role of glutathione metabolism in
plant responses to environmental stress.
The results showed that antioxidant protection in both cultivars are
mainly due to the enzymes and molecules involved in glutathione
metabolism and re-watering regulates the timing of drought effect in
part by delaying the increased proteolytic activity and subsequent
protein
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degradation.
2nd International e-Conference on Agricultural Biosciences 2009
Conference website: http://www.e-conference.elewa.org/agriculture
Genetic, Physiological and Biochemical responses
of some plants to interactive biotic and abiotic
stress.
Effect of some cumulative stress on the ultrastructure
and
antioxidant
isozymes
of
some
economically important plants.
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2nd International e-Conference on Agricultural Biosciences 2009
Conference website: http://www.e-conference.elewa.org/agriculture
7/31/2017
This research was supported through the research center of Teachers
College at King Saud University, project no. 12/1427. The author would
also like to thank Dr. Salah Barakat, Professor of Plant Physiology,
Botany Dept., Faculty of Science, Alexandria University for his
comments and revision on the manuscript.
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2nd International e-Conference on Agricultural Biosciences 2009
Conference website: http://www.e-conference.elewa.org/agriculture
7/31/2017