This document discusses abiotic stress in plants. It defines abiotic stress and outlines several types of abiotic stressors plants face, such as drought, salinity, cold, heat, and pollution. These stressors can cause reactive oxygen species accumulation and damage membranes and photosynthesis. The document also examines plant responses to abiotic stress, including changes in hormone signaling, gene expression, alternative splicing, and metabolic profiles. Certain plants like C. plantagineum and Thellungiella halophila are presented as model organisms for studying drought and salt tolerance, respectively. Future challenges in the field are identified as well.

1. By:
Yashdeep Srivastava
(J.N.U Ph.D.)
Metabolic And Structural Biology Division
CSIR-CIMAP

2. Though the term “stress” has been defined exactly in mechanics, in the case of biology it
has been given widely different meanings.
Probably due to an extension of the physical meaning, many of these definitions converge
in attributing “stress” to any environmental factor “unfavorable” for the living organism
under consideration.
STRESS

3. Light and heat stress induces
membrane damage and photo
inhibition that leads to ROS
accumulation.
Drought stress causes stomata closure
and photosynthesis impairment which
leads to ROS accumulation .
Pollutants such as O3 and
suphuric acid, causes acid
Rain,and directly damage the
leaves and induce oxidative
stress on tissues
Soil salinity causes stress which
leads to ROS production .High
salinity decreases mineral nutrient
uptake further stressing the plant.
Cold Stress often alters
membrane properties and
affect enzymatic activity. Frost
damage can cause severe
damages to the plant and tissues
necrosis.
Mechanical damage ,caused
both by abiotic and biotic factors
,induces the expression of
defense related functions.
Heavy metals cause cytotoxic effects via
different mechanisms such as production
of ROS ,blocking of essential functional
groups and displacement of essential
metal ions from biomolecules.
Water excess causes hypoxia
,programmed cell death and
oxidative stress .
Fig. Effect of different types of
abiotic stresses

4. Fig:The complexity of the Plant response to Abiotic Stress

5. INTERACTIONS BETWEEN ABIOTIC AND BIOTIC STRESSES:
Abiotic stresses
Drought
High salinity
Heat
Biotic stresses
Pathogen Wounding
Mechanical
Insect
Herbivory
ROS Accumulation
Hormones :ABA
Hormones
SA,ET,JA,ABA
Kinases
Transcription Factors
MYC,MYB,NAC,ZF,HSF
STRESS RESPONSE
Fig: Convergence points in abiotic and biotic stress signalling networks

6. Transcriptional regulation in Abiotic stress
Cold Stress Drought(Osmotic)
Stress
ICE1 CAMTA
DREB1A/CBF3 DREB1C/CBF2
DREB1A/CBF3
DREB1C/CBF2
DREB1B/CBF1
DRE/CRT
ABA
DREB2
AREB/ABFMYB MYCNACZFHD

7. POST-TRANSCRIPTIONAL REGULATION OF ABIOTIC
STRESS-INDUCIBLE TRANSCRIPTS
RNA helicases are implicated in abiotic stress responses in various organisms including
plants .
Alternative splicing, which enables production of diverse polypeptides from one gene, is
regulated by various abiotic stresses.
Complex multi-step regulation controls the splicing profiles in abiotic stress responses.
Alternative splicing events are considerably conserved between Arabidopsis and rice,
indicating their importance

8. HORMONE RESPONSE IN ABIOTIC STRESSES:
Rate limiting
Enzymes
9-cis-epoxycarotenoid di-oxygenases
(NCEDs) of ABA biosynthesis
P450 CYP707As of ABA catabolism
Rehydration
Rehydration
VacuoleCytoplasm
ABA glucosyl-ester
Vacuole
Cytoplasm
ABA glucosyl ester
ABA
β-glucosidase

9. ABA
receptors
Soluble receptors eg. PYR1, RCAR1, STAT type
Membrane anchored receptors eg. GTG1, GTG2
The downstream signaling pathway has not been fully
elucidated.
Fig.ABA signaling pathway including ABA soluble receptors
ABA
AREB/ABF etc.
AREB/ABF etc.

10. METABOLIC PROFILE CHANGES UNDER ABIOTIC STRESS
Under stress conditions, plants appear to re-organize their metabolic network in
order to adapt to such conditions.
Abiotic Stress
Increased production of
specific desired compounds
Reduction in the level
of toxic compounds
Amino Acid
PROLINE
Salt stress
In Plants Pyrroline 5 carboxylate synthetase
(P5CS)
PROLINE

11. Proline confer a protective effect by inducing stress protective proteins.
Exogenously applied proline and salt stress in Pancratium maritimum were found to induce
the expression of ubiquitin, antioxidative enzymes and dehydrins.
Amines
Glycine-betaine
Salt stress
Suaeda
liaotungensis
(Halophyte)
Betaine aldehyde
decarboxylase
Tobacco Resistant to salt
conditions
Choline dehydrogenase
gene (codA)
Arthrobactor
globiformis
Rice
Choline Glycine-
betaine
Resistant to salt
conditions
Tomato
chloroplast
Tolerant to
chilling and
oxidative stress

12. Salt stress
Polyamines
Arginine decarboxylase, ornithine
decarboxylase and S-adenosyl
methionine decarboxylase
Putrescine,
spermidine,
spermine
Sugar and sugar alcohol
Trehalose (rare non reducing sugar) found in many bacteria and fungi and in some dessication
tolerant higher plants.
Increase in trehalose levels in transgenic plant resulted in higher photosynthetic rate and decrease in
photooxidative damage during stress.
Trehalose has water absorption capacity to protect biological molecule from dessication induced
damage.
Mannitol (ROS scavanger) is another sugar alcohol that accumulate upon salt and water stress.

13. Metabolite profiling
Arabidopsis
Drought and
heat stress
Maltose and
glucose
Proline
Drought stress
Proline
Heat stress : reduces the toxicity of proline
Combination of stress – Sucrose (major osmoprotectant) replaces Proline

14. Salt stress increases various
secondary metabolites in plants
Influence of drought stress on
various plant secondary metabolites

15. Model Plants for study of Abiotic stress responses:
Drought Tolerance:
Regular drought tolerant plants can withstand 30% water loss and desiccation tolerant Plant tolerate
90% water loss and have ability to rehydrate successfully so they can used as model plants for
dehydration studies. Ex. C. plantagineum.
Sainity Tolerance :
•Halophytes such as Mesembryanthemum crystallinum (ice plant) is a model C3/CAM plant.
•Salt stress mechanism in this plant were studied with respect to C3/CAM shift and oxidative stress by
characterizing Na +/K+ transporters and aquaporins.
•Thellungiella halophila(salt cress) is closely related to A. thaliana but in contrast to Arabidopsis this
plant tolerates extreme salinity, drought and cold.
•Transcript profiling experiment revealed that salinity induces fewer genes in Thellungiella than in
Arabidopsis and in sat free condition stress related genes in Thellungiella exhibits higher expression .
•Ion channnels in Thellungiella root cells have higher K+/Na + specificity than Arabidopsis.

16. C. plantagineum.
Mesembryanthemum crystallinum
Thellungiella halophila

17. Identification of sensors and signaling pathways for abiotic stresses.
Understanding the molecular basis of interplay among stresses (including
biotic stresses).
Identification of key factors in the connection between abiotic stress
responses and developmental processes.
Addressing how local abiotic stress signals are processed and transduced to
other parts of the plant body.
Examining long-term plant responses under multiple abiotic stress conditions
in nature.
 Establishment of experimental conditions that mimic field conditions.
Future challenges

18. References:
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3. Gaspar T.et.al.(2002); Concepts in plant stress physiology. Application to plant tissue
cultures. Plant Growth Regulation, 37, 263–285.
4. Matthew A.J. and Hasegawa P. M. (2005); Plant Abiotic Stress. Blackwell Publishing
Ltd.
5.Fujita M. et.al.(2006) ; Crosstalk between abiotic and biotic stress responses: a current
view from the points of convergence in the stress signaling networks. Current Opinion in
Plant Biology, 9,436–442.
6. Wang W et. al.(2003); Plant responses to drought, salinity and extreme temperatures:
towards genetic engineering for stress tolerance. Planta, 218,1-14.