Download Water stress

Plant Response
to Stress
II
Water Stress,
Drought stress
Development of water stress
Adaptation to drought
Signals and signalling pathways
Basic processes affected by water stress
Water stress
•
Water stress is induced when transpiration rate is higher than absorption
rate
•
High transpiration rate
•
Low absorption rate
•
Gradient of water potential between substrate and shoot is prerequisite for
water transport
Importance for water deficiency: Ψw = Ψs + Ψp
•
- low air humidity,
- high temperature,
- high irradiance,
- strong wind
- low soil moisture
- high concentration of salts,
- low soil temperature
•
Plants can only absorb water if their water potential is more negative than that
of the source (soil, etc.); Transport of water only from higher to lower water
potential
•
When water potential in cells higher: osmotic adjustment.
This is the net increase in accumulation of solutes within cells in response to
stress; in cytoplasm or vacuole.
•
Transport of water for storage equilibrates small differences between
transpiration rate and absorption rate
Drought Stress/Water Stress/Osmotic Stress...
Main effects of water stress
1. Reduction in cell and leaf expansion
2. Reduction in photosynthesis, due first to
decreased stomatal conductance, then to
inhibition of chloroplast metabolism.
3. Altered allocation - greater investment in nonphotosynthetic tissues such as roots &
mycorrhizae
Drought Stress/Water Stress/Osmotic Stress...
Main effect of water stress : growth reduction
Leaf expansion is very sensitive to water deficit
Second effect: Reduction in photosynthesis, due first to decreased stomatal
conductance, then to inhibition of chloroplast metabolism
Drought Stress/Water Stress/Osmotic Stress...
Effects of water deficiency on photosynthesis and
transport of assimilates in millet.
Phloem translocation seems to be less
sensitive to water stress than photosynthesis.
Drought Stress/Water Stress/Osmotic Stress...
Physiological consequences of low water stress
Responses
to deal
with stress
The edt1 Mutant with Greatly Improved. Drought Tolerance
.
©2008 by American Society of Plant Biologists
Yu H et al. Plant Cell 2008;20:1134-1151
(A) and (B) Under short-day conditions, 4week-old wild type (A) and mutant (B) plants
were similar, except that the mutant had more
rosette leaves with shorter leaf petiole. Bars =
1 cm. (C) and (D) Under long-day conditions,
the 4-week-old mutant showed more vigorous
vegetative growth (D) and had more rosette
leaves than the wild type (C). Bars = 1 cm.
(E) to (G) Drought tolerance assay. The
mutant and wild-type seeds were germinated
in soil side by side at high density under the
same greenhouse conditions.
(E) Two-week-old seedlings immediately
before drought stress.
(F) Seedlings deprived of water for 7 d.
(G) Seedlings deprived of water for 14 d.
(H) Drought stress of the mutant and wild-type
plant grown in the same pot. One mutant and
one wild-type plant were grown in the same
pot for 4 weeks under short-day conditions
before drought stress was imposed. The
photos were taken 2 weeks after watering was
withheld.
(I) Comparison of water loss rate of detached
leaves from the mutant and wild type. Fourweek-old plants were derooted and allowed to
dry in the air. Fresh weight was measured at
the indicated times. Water loss was expressed
as the percentage of the initial fresh weight.
Values are mean ± SE (n = 20 plants
The edt1 Mutant with Greatly Improved Drought Tolerance
3days
10 days
5
20 days
(F) Number of lateral roots of the wild-type and the mutant (edt1) seedlings grown on medium
as in (A). The number of lateral roots was counted at the indicated time points. Values are
mean ± SE (n = 30 seedlings).
(G) Root dry weight of wild-type and mutant (edt1) seedlings grown on medium as shown in
(B). Values are mean ± SE (n = 30 seedlings, ** P < 0.01).
(H) Root biomass of soil-grown wild-type and edt1 mutant plants as shown in (D). Fresh
weight of roots was compared between the mutant and the wild-type plants. Values are mean
± SE (n = 10 seedlings, ** P < 0.01).
©2008 by American Society of Plant Biologists
Improved Root Architecture of
the edt1 Mutant.
(A) The primary root of 3-d-old
mutant seedlings (edt1) was
longer than that of the wild type of
the same age on Murashige and
Skoog (MS) medium. Bar = 0.5
cm.
(B) The primary root of 10-d-old
mutant seedlings (edt1) was
longer than that of the wild type of
the same age on MS medium.
Bar = 1 cm.
(C) Twenty-day-old mutant
weeks
seedlings (edt1) have more lateral
roots than wild-type seedlings of
the same age.
(D) Five-week-old mutant (edt1)
and wild-type plants were grown
in soil under short-day conditions.
The plants were removed from
the soil and carefully washed
without damaging the taproots.
Bar = 2 cm.
(E) Primary root elongation of the
wild-type and mutant seedlings
(edt1) grown on medium as in
(A). The length of the primary root
was measured at the indicated
time points. Values are mean ±
SE (n = 30 seedlings).
Yu H et al. Plant Cell 2008;20:1134-1151
The edt1 Mutant with Greatly Improved Drought Tolerance
Reduced Stomatal Density and Increased
Water Use Efficiency of the Mutant.
WUE (mg photosynthate
produced/g water transpired)
Reduced Stomatal Density and Increased Water Use Efficiency of the Mutant.
(A) Comparisons of adaxial epidermal imprint images of the wild type and the mutant (edt1) at the same x200 and x400 magnifications.
(B) and (C) Comparisons of stomatal and cell density (B) and stomatal dimension (C) in the wild type and the edt1 mutant. Values are
mean ± SE (n = 30 plants, * P < 0.05, **P < 0.01).
(D) to (F) Comparisons of photosynthesis rate (D), transpiration rate (E), and WUE (F) in the wild type and the edt1 mutant. WUE (mg
photosynthate produced/g water transpired) was measured as described in Methods. Three measurements were made for each plant,
and five plants were used for each line. Values are mean ± SE (n = 30 plants, * P < 0.05, **P < 0.01).
The edt1 Mutant with Greatly Improved Drought Tolerance
The edt1 Mutant with Greatly Improved Drought Tolerance
Quantification of ABA, Pro, and SOD Activity in the edt1 Mutant, 35S-HDG11, and Wild-Type Seedlings.
(A) ABA contents. Ten-day-old seedlings of the wild type, edt1 mutant, and 35S-HDG11 transgenic lines
were used for ABA quantification. ABA was determined by ELISA. Values are mean ± SE (n = 3
experiments, * P < 0.05, **P < 0.01). FW, fresh weight. (B) Pro contents. Ten-day-old seedlings of the wild
type, edt1 mutant, and 35S-HDG11 transgenic lines were used for Pro quantification. Pro content was
measured spectrophotometrically. Values are mean ± SE (n = 3 experiments, * P < 0.05, **P < 0.01). (C)
Comparison of oxidative stress tolerance between the wild-type and edt1 mutant seedlings. The wild-type
and mutant seeds were first germinated on MS medium and then transferred to MS medium containing 0
(Control) or 0.2 µM paraquat (Paraquat) and incubated under continuous light at 22°C for 1 week before the
photographs were taken. (D) Survival rate of the wild type and mutant on medium containing 0 (Control) or
0.2 µM paraquat (Paraquat) over a period of 1 week. Survival rate (y axis) was defined as the percentage of
the wild-type control. Values are mean ± SE (n = 50 plants, **P < 0.001). (E) Comparison of SOD activity
between the edt1 mutant and the wild type. Ten-day-old mutant and wild-type seedlings were treated with 0
or 10% PEG 6000 in liquid MS medium for 6 h, and then SOD activity was assayed and presented as folds
of the wild-type control. Values are mean ± SE (n = 3 exp., * P < 0.05, **P < 0.01). (F) Estimation of SOD
mRNA level in the edt1 mutant and the wild type by RT-PCR. Total RNA was isolated from 1- and 2-weekold seedlings (1W and 2W) and leaves (L) and roots (R) of 4-week-old plants grown in soil. SOD transcript
levels were estimated by RT-PCR for 30 cycles with specific primers for SOD. Tubulin (Tub) transcript
levels serve as an equal loading standard. The experiment was repeated three times, and the typical result
of an ethidium bromide–stained agarose gel is presented. (G) Estimation of SOD mRNA level by real-time
RT-PCR. Using the same sample and primers as in (F), real-time RT-PCR was performed for 30 cycles.
The relative transcript level was obtained as folds of the tubulin transcript level, which was used as the
internal control. Values are mean ± SE (n = 3 experiments).
The edt1 Mutant with Greatly Improved Drought Tolerance
Identification of the T-DNA Tagged Locus and Activated Expression of the Tagged HDG11 Gene.
(A) DNA gel blot analysis to estimate the copy number of T-DNA insertion. Total DNA was isolated from the edt1
mutant seedlings and digested with restriction endonuclease HindIII (H3) and EcoRI (R1), respectively. The wild
type Columbia was used as control. Lane M is the 1-kb ladder molecular size marker. The DNA gel blot was
probed with bar and washed at high stringency. The autoradiograph indicates that the mutant edt1 genome
contains only one T-DNA insert.
(B) Illustration of the chromosomal location of the T-DNA insertion and locus At1g73360 (not drawn to scale). The
single T-DNA insertion site was identified through plasmid rescue. The relative location (inverted solid triangle) and
orientation (small arrow) of the T-DNA are shown (top panel). The T-DNA right border with the four copies of 35S
enhancers was inserted in the 5' UTR, at 50 bp upstream of the ATG codon of HDG11 (middle panel). The HDG11
gene encodes a predicted protein of 722 amino acids with two known functional domains: a homeodomain for
DNA binding and a START domain presumably for ligand binding (bottom panel).
(C) RT-PCR analysis of transcript levels of the neighboring genes. Transcript levels for At1g73350, At1g73360
(HDG11), and At1g73370 were compared in both roots (R) and leaves (L) in the wild type and the edt1 mutant.
The experiment was repeated three times, and a typical result is presented.
(D) Real-time RT-PCR analysis of transcript levels of the neighboring genes. Using the same samples and primers
as in (C), real-time RT-PCR was performed for 30 cycles. The relative transcript level was obtained as folds of the
tubulin transcript level, which was used as the internal control. Values are mean ± SE (n = 3 experiments).
(E) RT-PCR analysis of the expression patterns of HDG11 in the mutant and the wild type. RNA was isolated from
roots (R), rosette leaves (RL), cauline leaves (CL), inflorescence stem (ST), flower buds (FB), flowers (FL), young
siliques (YSi), and mature siliques (MSi) of the wild type and the edt1 mutant plants, respectively. Tubulin was
used as a loading control. The experiment was repeated three times, and a typical result is presented.
(F) Real-time RT-PCR analysis of the expression patterns of HDG11 in the mutant and the wild type. Using the
same samples and primers as in (E), real-time RT-PCR was performed for 30 cycles as described in Methods.
The relative transcript level was obtained as folds of the tubulin transcript level as the internal control. Values are
mean ± SE (n = 3 experiments).
The edt1 Mutant with Greatly Improved Drought
Tolerance
Drought Stress/Water Stress/Osmotic Stress...
Summary of Drought Stress Symptoms
M acroscopic physiological dam age caused by dehydration.
In general: can lead to many developmental changes including
• Inhibition of elongation growth, cell division, changes in cell
wall synthesis
• delays in flowering
• leaf abscission
• stomatal closure,
• Acceleration of ageing
• Reduced tillering and root development.
• curling and rolling of leaves during midday
• Reduction of spikelets and florets during the development of
the spike
• grain shriveling (main stress).
• during the development of the spike and during seed set:
complete or partial sterility.
Drought Stress/Water Stress/Osmotic Stress...
Summary of Drought Stress Symptoms
Biochem ical dam age caused by dehydration.
• Production of stress proteins
• Accumulation of osmotically active compounds (proline,
glycinebetaine, sugars, sugar alcohols)
• ROS production and development of antioxidative systems
• Inhibition of photosynthesis,
• Changes in enzyme activities (decrease in activity of Rubisco,
PEPC, nitratereductase)
• higher root carbon allocation, transport of assimilates,
respiration
• Changes in biosynthesis and catabolism of phytohormones,
especially ABA
• Changes in absorption and transport of ions
• cuticular wax increase: reduces cuticular transpiration,
increases reflection
Water stress affects almost all processes in plants
Drought Stress/Water Stress/Osmotic Stress...
Tentative scheme of
photosynthetic control under drought
Under drought, stomatal closure (2) in
proportion to the degree of the stress
progressively limitating ΔpH in the
chloroplasts. (3) CO2 assimilation is
reduced and CO2:O2 ratio drops
thereby increasing photorespiration
Less ATP and/or Mehler reaction (4). Since these
consumption processes consume relatively less
ATP than does photosynthesis, they
should lead to a certain increase of
trans-thylakoid ΔpH (5). Impaired ATPase and/or ETR may also interfere with
Photorespiration
the build up of of trans-thylakoid ΔpH.
(6) The xanthophyll deepoxidation that
follows increased ΔpH should lead to
increased NPQ (7). Thermal
dissipation in the antenna becomes
progressively more important and Fs
is consecutively lowered (7). The
relationship between Fs and stomata
conductivity provides a method for
remote sensing stress.
Adaptations of plants to water stress
1) drought avoidance – whole growth cycle in a wet season, leaf
fall under drought: plants complete their life cycles during the
“wet season, before the onset of drought;
2) drought tolerance (resistance) ability to function while
dehydrated
• drought tolerance at low cell water potential – survive with
minimum metabolism: seeds, pollen grains, resurrection plants
• drought tolerance at higher cell water potential.
 adaptation reactions against drought stress
- regulation of water loss (stomata, cuticle, trichomes, leaf
movements, leaf shape, leaf area, C3→CAM), 
Drought Stress/Water Stress/Osmotic Stress...
Adaptation reactions against water stress
Leaf structure: water deficit increase wax deposition on the leaf surface
a)
The production of a thicker cuticle that reduces water loss from the
epidermis (cuticle transpiration)
b)
A thicker cuticle also decreases CO2 permeability, but leaf photosynthesis
remains unaffected because the epidermal cells underneath the cuticle are
nonphotosynthetic
Drought Stress/Water Stress/Osmotic Stress...
Adaptation reactions against water stress
Rooting characteristics:
water deficit enhances root extension into deeper, moist soil
a)
Inhibition of leaf expansion by water deficit reduces the
consumption of carbon and energy, and a greater proportion
of the plant’s assimilates can be distributed to the root
system, where they can support further root growth
b)
The enhanced water uptake resulting from root growth is
less pronounced in reproductive plants than in vegetative
plants
Adaptations of plants to water stress
1) drought avoidance – whole growth cycle in a wet season, leaf fall under
drought: plants complete their life cycles during the “wet season, before
the onset of drought;
2) drought tolerance (resistance) ability to function while dehydrated
• drought tolerance at low cell water potential – survive with minimum
metabolism: seeds, pollen grains, resurrection plants
•
drought tolerance at high cell water potential.
 adaptation reactions against drought stress
- regulation of water loss (stomata, cuticle, trichomes, leaf movements,
leaf shape, leaf area, C3→CAM), 
- regulation of absorption (amount and morphology of roots, osmotic
adjustment), 
- efficient water transport with low water potential,
- water storages (stems, trunks, fruits),
- production of protection compounds (e.g. carotenoids,
osmolytes, stress proteins, antioxidants) 
Osmotic adjustment helps plants to cope with water stress
Water uptake from the soil happens when soil A decrease in Ψ S helps to
potential is higher than plant water potential maintain turgor, Ψ P, and
contributes also to a lower water
potential decreases.
Osmotic adjustment is a net
increase in solute content per
cell.
Many solutes contribute to
osmotic adjustment. K+, sugars,
organic acids, amino acids
Osmotic adjustment may occur
over a period of days.
Costs of osmotic adjustment:
synthesis of organic solutes,
maintenance of solute gradients,
and energy, which can not be
used for other functions
Ψw = Ψs + Ψp
Osmotic and elastic adjustment
Osmotic adjustment
• Will be induced by decrease in soil water potential, air humidity, etc.
By 1. ion uptake
2. production and accumulation of osmoprotectants: osmotically active
substances
2.1 sugars (glucose, trehalose, saccharose), sugar alcohols (mannitol,
sorbitol, glycerol),
Accumulation of mono- and di-saccharides by inhibition of starch
synthesis from new photosynthates, degradation of starch, inhibiton of
respiration
3. polyamines, amino acids (proline), betaines (glycinebetaine)
Synthesis in chloroplasts by oxidation of choline in two steps
 Sugars serve not only as osmotica but also in signalling pathways, or
gene expression regulation
• Membrane protection, source of C or N, defence against ROS
• Dehydrines – ripening of seeds or pollen grains, in plant vegetative parts
during stresses, induced also by abscisic acid (ABA)
Elastic adjustment
• expansin, endoglucanase, transglycosylase, peroxidase
• At different plant species are different adaptations, amount of osmoticum
is not always in correlation with water stress tolerance
Drought Stress/Water Stress/Osmotic Stress...
Adaptation
against
the stress stress
Adaptation
reactionsreactions
against water
stress/osmotic
Adaptation of cytosolic water potential
Accumulation of compatible solutes: solutes
must accumulate in the cytoplasm to maintain water potential equilibrium within the cell
Function of the stress-induced cytosolic
osmolytes for lowering the Ψcyt of the roots:
1. Maintain the turgor
2. Driving force for water up-take
3. Stabilisation of membrane and proteins
4. Scavenger of ROS and organic radicals
Drought Stress/Water Stress/Osmotic Stress...
Gesamtmenge an gelösten Stoffen und einzelnen Substanzen In Wurzel (A/C) und Blatt
(B/D) unter verschiedenen Stressbedingungen (Wasserpotential) nach 30 min und 24 Std.
Ogawa and Yamauchi 2006
Drought Stress/Water Stress/Osmotic Stress...
Adaptation reactions against water stress
Stomatal control: stomatal close during water deficit in response to ABA
Changes in water potential, stomatal
resistance , and ABA content in maize
in response to water stress. As the
soil dried out, the water potential of
the leaf decreased, and the ABA
content and stomatal resistance
increased
a)
During water deficit, some of the
ABA stored in the chloroplasts is
released to the apoplast of the
mesophyll cells
b)
ABA is synthesized at a higher rate,
and more ABA accumulate in the
leaf apoplast
Function of abscisic acid
Drought response: Stomata closure
Acidic xylem sap
favors uptake of the
undissociated form
of ABA (ABAH) by
the mesophyll cells
During water stress,
the slightly alkaline
xylem sap favors
the dissociation of
ABAH to ABA-
Because ABA- does not easily
pass through membranes, under
conditions of water stress, more
ABA reaches guard cells
… stomatal closure mediated by ABA
cADPR – cyclic ADP-ribose
ROS – reactive
oxygen species
R – Receptor
IP3 – inositol triphosphate
NO – Nitric oxide
PA – Phosphopatidic
acid
PLC – phospholipase D
S1P – Spingosine-1Phosphate
PLC – phospholipase C
29
Drought Stress/Water Stress/Osmotic Stress...
Generation and scavenging of ROS and lipid peroxides
Drought Stress/Water Stress/Osmotic Stress...
Generation and scavenging of ROS and lipid peroxides
Generation and scavenging of superoxide radical and hydrogen peroxide, and hydroxyl radicalinduced lipid peroxidation and glutathione peroxidase-mediated lipid (fatty acid) stabilization.
APX, Ascorbate peroxidase; ASC, Ascorbate; DHA, Dehydroascorbate; DHAR, Dehydroascorbate
reductase; Fd, Ferredoxin; GR, Glutathione reductase; GSH, Red glutathione; GSSG, Oxiglutathione; HO, Hydroxyl radical; LH, Lipid; L LOO-1; LOOH, Unstable lipid radicals and
hydroperoxides; LOH, Stable lipid (fatty acid); MDHA, Monodehydro-ascorbate; MDHAR, Mono
dehydro-ascorbate reductase; NE, Non-enzymatic reaction; PHGPX, Phospholipid-hydroperoxide
glutathione peroxidase; SOD, Superoxide dismutase.
Water stress signalling
• Signal of water stress - decreased cell water content,
- decreased water potential and its components osmotic and
pressure potentials,
- increased concentration of solutes,
- decreased cell volume,
- change in membrane tension,
- changes in structure of macromolecules due to changes in
their hydration,
- changes in interaction between cell wall and plasmalemma
• Water stress receptors are not sufficiently known, probably
different for different signals
• For root-shoot communication hydraulic and chemical signals
are used
• Direct and indirect effects of water stress
Drought Stress/Salt Stress/Osmotic Stress...
Stress signalling
Signalling pathway leading to stress induced changes in gene
expression (Xiong et al. 2002)
A common framework model for the signal transduction of abiotic stress in higher plants.
Drought Stress/Salt Stress/Osmotic Stress...
The simple signalling model
Transcriptional network of abiotic stress responses
Saibo, N. J. M. et al. Ann Bot 2009 103:609-623; doi:10.1093/aob/mcn227
Copyright restrictions may apply.
DREB1A gene regulates a lot of target genes
to enhance tolerance to environmental stresses
Environmental Stress
Drought and High salinity
Signal Perception
Signal Perception
DREB1A
Tolerance
gene
expression
Tolerance
gene
expression
Overexpression of
DREB1A
Tolerance
gene
expression
Tolerance
gene
expression
DREB1A
Tolerance
gene
expression
Tolerance
gene
expression
Expression of more than 40 genes Enhanced expression of more than 40 genes
Environmental stress tolerance
Enhanced stress tolerance
Strategies towards increased stress tolerance
Combinations of promoters and transcription factors
①
Constitutive promoter (35S) ＋ DREB1A
Constitutive promoter
DREB1A gene
The constitutive promoter leads
to generate DREB1A products all the time
②
Stress-inducible promoter (RD29A) ＋ DREB1A
Stress-inducible promoter
DREB1A gene
The stress-inducible promoter leads
to generate DREB1A products only under stress conditions
Drought Stress
Dehydration tolerance of transgenic plants
Liu et al., 1998,
Plant Cell, 10, 1391-1406
Drought Tolerance of the 35S:DREB1Ab and 35S:DREB1Ac Transgenic Plants.
Control, 3-week-old plants growing under normal conditions; drought stress,
water withheld from plants for 2 weeks. Percentages of surviving plants and
numbers of surviving plants per total number of tested plants are indicated
under the photographs. wt, wild type.
Drought Stress/Cold Stress/Osmotic Stress...
stress tolerance of transgenic plants
Arabidopsis
::DREB1
2 Tage
-6 °C
2 Wochen
ohne Wasser
2 Stunden
600 mM NaCl
Drought Stress/Water Stress/Osmotic Stress...
stress tolerance of transgenic plants
Tolerance and growth properties in dependence of the promoter
Drought Stress/Water Stress/Osmotic Stress...
dehydration tolerance of transgenic plants
Drought Stress/Water Stress/Osmotic Stress...
stress tolerance of transgenic plants
Drought Stress/Water Stress/Osmotic Stress...
stress tolerance of transgenic plants
Drought-stress tolerance of transgenic Arabidopsis plants expressing constitutively active DREB2A
(DREB2A CA). Wild-type plants could not survive without watering for two weeks. In contrast, three
lines of DREB2A CA transgenic plants could survive despite severe desiccation. Plants marked with
* and ** had significantly higher survival rates than the wild type (x2 test, P < 0.05 and P < 0.01,
respectively).
Drought Stress/Water Stress/Osmotic Stress...
Expression of ABFs (bZIP proteins; ABRE binding factors) is induced by
ABA and various stress treatments
ABA-responsive cis-elements
1.
(C/T)ACGTGGC
2.
GGACACGTGGC
3.
ACGCGTGTCCTC
4.
GCCGCGTGGC
5.
GGACGCGTGGC
Analysis of ABF expression. ABA and stress inducibility of ABF expression were examined by RNA gel
blot analysis or RT- PCR. A, inducibility of ABF expression. 25 µg of total RNAs isolated from untreated
plants or plants treated with ABA, high salt, cold, or drought were transferred to a membrane and probed
with specific probes. B, time course of ABA induction. RT- PCR reactions were performed using 0.5 mg of
total RNAs from plants treated with 100 mM ABA for 0 min, 30 min, 1 h, 2 h, 4 h, 8 h 12 h, 16 h, and 24 h.
actin, a control reaction performed with an actin gene of A. thaliana.
Choi et al., 2000, JBC, 275, 1723-1730
Drought Stress/Water Stress/Osmotic Stress...
Both ABF3- and ABF4 (bZIP proteins; ABRE binding factors) -transgenic
plants survived the drought conditions better than did the wild-type
plants
16%
33%
Kang et al., 2002, Plant Cell, 14, 343-357
Drought Tolerance of 35S-ABF3 and 35S-ABF4 Plants. (A) Transgenic and wildtype plants were grown on soil in the same container for 2 weeks, withheld from
water for 11 days, and then rewatered. The photographs were taken 3 days after
the rewatering. (B) Plants at similar developmental stages (2-week-old wild-type
plants and 3-week old ABF4 plants) were withheld from water for 12 days and
then rewatered. The photographs were taken 3 days after the rewatering.
Drought Stress/Water Stress/Osmotic Stress...
Both ABF3- and ABF4-transgenic plants survived the drought conditions better
than did the wild-type plants
20%
85%
Drought Tolerance of 35S-ABF3 and 35S-ABF4 Plants. Stomatal aperture of ABF
transgenic plants. Stomatal guard cells were observed in the middle of the
watering period.
Kang et al., 2002, Plant Cell, 14, 343-357
Drought Stress/Water Stress/Osmotic Stress...
Both ABF3- and ABF4-transgenic plants survived the drought conditions
better than did the wild-type plants
Drought Tolerance of 35S-ABF3 and 35S-ABF4 Plants. (C) and (D) Leaves of
similar developmental stages were excised and weighed at various times
after the detachment.
Kang et al., 2002, Plant Cell, 14, 343-357
Changes in gene expression induced by drought, salinity or cold
(Seki et al. 2002)
Classification of the drought, cold or
high-salinity stress inducible
genes identified on the basis of
microarray analyses.
In total, 277 drought-inducible, 53 cold-inducible and
194 high-salinity stress-inducible genes were
identified by cDNA microarray analysis. The drought,
cold or high-salinity stress-inducible genes
identified were grouped into the following seven
groups: (1) highly cold-stress-inducible; (2) highly
drought-stress-inducible; (3) highly high-salinitystress inducible; (4) drought, cold and high-salinity
stress-inducible; (5) genes that were highly induced
by drought and high-salinity stress; (6) genes that
were highly induced by drought and cold stress; (7)
genes that were highly induced by cold and highsalinity stress. The number of genes whose
expression ratio is more than fivefold for each stress
treatment and less than fivefold for the other stress
treatments is indicated. Numbers in parentheses
represent the number of genes whose expression
ratio is more than fivefold for each stress treatment
and less than threefold for the other stress
treatments.
Water stress and protein synthesis
1) Inhibition of synthesis of some proteins
2) Stimulation of synthesis of other proteins
3) Synthesis of specific stress proteins
• A) proteins taking part in signal transduction and gene
expression, e.g. transcription factors (MYC, MYB), protein
kinases (MAPK), enzymes of phospholipid metabolism
(phospholipase C, D)
• B) proteins participating in stress tolerance, e.g. membrane
proteins, proteins of water and ion channels, protection factors
(chaperones, LEA proteins), syntases of osmoprotectants,
stress proteins localized in chloroplasts, specific inhibitors of
proteolytic activity, antioxidants, antioxidative enzymes, proteins
taking part in recovery after stress
Functions of water-stress-inducible gene products
Regulatory proteins
Functional proteins
Water channel
protein
Transcription factors
(MYB, MYC, DREB, AREB)
Detoxification enzymes
Protection factors of
Macromolecules
(LEA protein)
Key enzymes for
Osmolyte biosynthesis
(proline, sugar)
Protein kinases
(CDPK, MAPK)
Water stress
Phospholipid metabolism
(PLC, PIP5K)
ABA biosynthetic
enzyme
Detoxication
enzyme