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PRESENTED BY
Fatima Zannath Mete
Reg.no.:01669
M.S in Agronomy
Patuakhali Science & Technology University,
Dumki,Patuakhali-8602.

Molecular and Physiological Analysis of
Drought Stress in Arabidopsis Reveals
Early Responses Leading to Acclimation in
Plant Growth

INTRODUCTION
Drought is a major environmental stress factor that
affects the growth and development of plants.
Drought or soil water deficit can be chronic in
climatic regions with low water availability or
random and unpredictable due to changes in weather
conditions during the period of plant growth.So Plant
drought stress response and resistance are complex
biological processes that need to be analyzed at a
systems level using genomics and physiological
approaches to dissect experimental models that
address drought stresses encountered by crops in the
field.

INTRODUCTION CONTD
Toward this goal, a controlled, and moderate drought
(mDr) treatment system was developed in
Arabidopsis (Arabidopsis thaliana) as a reproducible
for the dissection of plant responses to drought. The
drought was validated using Arabidopsis mutants in
abscisic acid (ABA) biosynthesis and signaling
displaying drought sensitivity shown by drought
resistance, indicating the necessary role of ABA in
drought response and acclimation.

INTRODUCTION CONTD
A comparative transcription analysis of mDr stress
responses using a time-course analysis of
biochemical, physiological, and molecular processes
revealed early accumulation of ABA and induction of
associated signaling genes, coinciding with a decrease
in stomatal conductance as an early avoidance
response to drought stress.

MATERIALS AND METHODS
 Arabidopsis (Arabidopsis thaliana ecotype
Columbia) seeds were sown in moistened peat
pellets (Jiffy Products), stratified at 4C for 2 d,
and then transferred to a growth room kept at 10
h of light (100 mmol m22 s21) and 22C.For
drought treatment, pellets were weighed before
sowing to determine the amount of water in
pellets at the beginning of the experiment.
Controlled mDr was maintained by giving plants
water to keep the soil moisture level at 30% of
field capacity, which is 200% or 2 g water g21 dry
soil.

RESULTS
Plant Temporary Responses to mDr:
To study the response of Arabidopsis to controlled
soil water deficit drought, the effect of mDr was
tested at different vegetative developmental
stages. Plants were grown under well-watered
conditions, and drought stress was applied by
withholding water at different growth stages to
three batches of plants: at 25 d after sowing
(DAS), 30 DAS, and 35 DAS.

Schematic illustration of the drought treatments and sampling in this study.

RESULTS
CONTD
 Gas-Exchange Parameter Changes in Response to
mDr.
 Plant Transcriptional Response to Soil Water
Deficit.
 cis-Regulation of Drought Response Genes
 Cellular Metabolism under Drought Stress
 Expression of Stress Signaling Pathway Genes
under Drought Stress
 Stomatal Responses in a Time-Course Analysis of
mDr
 Drought Responses of Hormonal Pathway
Mutants

DISCUSSION
Growth Reduction under Drought Stress:
The application of controlled mDr stress on
Arabidopsis plants enabled us to evaluate many
parameters in relation to the drought stress
treatment as well as the response of plants at the
physiological and molecular levels simultaneously.
so the causes of the reduction of growth due to
drought stress, the time when the responses start,
and the physiological, biochemical, and molecular
changes responsible for the reduction of growth
under drought.

DISCUTION CONTD
Acclimation to mDr by Cell Wall Adjustment:
One of the first acclimation responses to drought is
the decrease in leaf growth, which results in the
maintenance of cell turgor and reduces the
transpiration area.For this reason Arabidopsis
leaves show low expansion rate.
The plant cell wall is required not only for
mechanical support but for growth and adaptation
to its environments.

DISCUTION
CONTD
Model of Plant Responses to Drought:
The response to mDr, extended over a period
of time, can be distinguished into multiple stages,
from early to intermediate to late.During the early
priming or preconditioning stage, stress
perception,signaling, and reprogramming of gene
expression take place. Many of these immediate
responses, such as ABA response genes and ROS
scavengers, probably involved in signaling
responses, are also observed in pDr. The drought
response pathways can be traced by the expression
pattern of individual genes of known function.

Physiological, biochemical, and molecular plant responses to mDr.

CONCLUSION
From a comparative analysis the mDr stress
responses using a time-course analysis of
biochemical, physiological, and molecular
processes tell that early accumulation of ABA
and induction of associated signaling genes,
coinciding with a decrease in stomatal
conductance as an early avoidance response to
drought stress.

CONCLUSION CONTD
This is accompanied by a peak in the expression of
genes involved in cell wall expansion, as a
preparatory step toward drought acclimation by
the adjustment of the cell wall. The time-course
analysis of mDr provides a model with three
stages of plant responses: an early priming and
preconditioning stage, followed by an
intermediate stage preparatory for acclimation,
and a late stage of new homeostasis with reduced
growth.

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Molecular and Physiological Analysis of Drought Stress in Arabidopsis Reveals Early Responses Leading to Acclimation in Plant Growth

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Molecular and Physiological Analysis of Drought Stress in Arabidopsis Reveals Early Responses Leading to Acclimation in Plant Growth

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