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
Light and heat stress induces
membrane damage and photo
inhibition that leads to ROS
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
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
Fig:The complexity of the Plant response to Abiotic Stress
INTERACTIONS BETWEEN ABIOTIC AND BIOTIC STRESSES:
Fig: Convergence points in abiotic and biotic stress signalling networks
POST-TRANSCRIPTIONAL REGULATION OF ABIOTIC
RNA helicases are implicated in abiotic stress responses in various organisms including
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
HORMONE RESPONSE IN ABIOTIC STRESSES:
(NCEDs) of ABA biosynthesis
P450 CYP707As of ABA catabolism
ABA glucosyl ester
Soluble receptors eg. PYR1, RCAR1, STAT type
Membrane anchored receptors eg. GTG1, GTG2
The downstream signaling pathway has not been fully
Fig.ABA signaling pathway including ABA soluble receptors
METABOLIC PROFILE CHANGES UNDER ABIOTIC STRESS
Under stress conditions, plants appear to re-organize their metabolic network in
order to adapt to such conditions.
Increased production of
specific desired compounds
Reduction in the level
of toxic compounds
In Plants Pyrroline 5 carboxylate synthetase
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.
Tobacco Resistant to salt
Resistant to salt
Arginine decarboxylase, ornithine
decarboxylase and S-adenosyl
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
Mannitol (ROS scavanger) is another sugar alcohol that accumulate upon salt and water stress.
Heat stress : reduces the toxicity of proline
Combination of stress – Sucrose (major osmoprotectant) replaces Proline
Salt stress increases various
secondary metabolites in plants
Influence of drought stress on
various plant secondary metabolites
Model Plants for study of Abiotic stress responses:
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.
Identification of sensors and signaling pathways for abiotic stresses.
Understanding the molecular basis of interplay among stresses (including
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
Establishment of experimental conditions that mimic field conditions.
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