Transcript No Slide Title

Molecular Stress
Response
Categories within Protective and
Protected Processes
Gene
Expression
Signal
Transduction
Protease-associated
ROS and Stress
Environmental
Change
Protective
Processes
Nucleus
Cell Wall Related
Trafficking
Phenylpropanoid
Pathway
Development
Protected
Processes
Secretion
Cells
Cytoskeleton
Tissues
Plant Growth Regulation
Chloroplast Associated
Metabolism
Carbon Metabolism
Respiration and Nucleic Acids
Mitochondrion
Scenarios for Effect of Abiotic
Stress on Plant Gene Expression
Regulatory network of gene expression in
response to cold stress and osmotic stress
Physiologia Plantarum 126: 62–71. 2006
A combinatorial network of post-transcriptional
and post-translational regulations
Plant Science 174 (2008): 420–431
Plants respond to stress on a cellular
and on the whole plant levels
Responses to Biotic and Abiotic stresses are connected genetically:
link between biotic
and abiotic stress signal transduction and
plant development
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Signal transduction
(Simplified model)
STIMULUS
Ca2+
Plasma
membrane
R
Ca2+
Phos
Kin
Nuclear
membrane
R
TF
DNA
Molecular scheme of abiotic stress
signal tansduction pathway in plants
Signal
Perception
Signal
Transduction
Signal
Response
CURRENT SCIENCE, VOL. 88, NO. 11, 10 JUNE
2005
The complexity of the plant responses
to different abiotic stresses
Wangxia Wang et al.,
(2003)
General Plant Response
 Expression of stress inducible gene involved in direct plant
protection against stress
a. Large number or proteins for enzymatic and structural protein
-. Membrane protein
-. Enzyme for osmolite biosynthesis and detoxification enzyme
b. Other protein for macromolecules protection
-. LEA protein
-. Chaperone
-. m-RNA binding protein
 A variety of regulatory protein
a. transcription factors
b. protein kinase
c. receptor protein kinase
d. ribosomal protein kinase
e. Signal transduction kinase
Unique Response
1. Heat schock proteins
2. Osmoprotectant
3. Proline
4. Glycine betaine
5. Trehalose
6. Manitol
Heat shock proteins
1. The synthesis and accumulation of HSP are assumed to
play a central role in the heat stress response and in
tolerance to high temperature
2. The heat stress response is a highly conserved reaction
caused by exposure of an organism tissue or cells to
sudden high temperature stress
3. HSPs are located in both cytoplasm and organelles such as
nucleus, mitochondria, chloroplast, and endoplasmic
reticulum
4. The transcription of HSP genes is controlled by regulatory
protein called heat stress transcription factors (HSF) which
exist as inactive proteins mostly found in the cytoplasm
Osmoprotectant
1. High soil salinity is one of the important factors that limits
distribution and productivity of major crops causing yield losses
2. It reduces the ability to take up water leading to reduction in
growth rate
3. Salt stress result in a wide variety of physiological and
biochemical change in plants, such as the activation of salt
inducing genes such as transcription factors, BZIP, LEA, RING
Zinc-finger and large scale production and accumulation of
osmolytes
4. Plant accumulates the derivation of those molecular weight
solutes to mitigate the detrimental effect of salt stress by
lowering the water potential of cell or by protecting various
cellular structure and protein during stress
Proline
1. Proline as an amino acid known to occur
widely in higher plant in response to
abiotic stress (salt/osmolite stress) and
normally accumulated in large quantities
2. It contribute to the stabilization of protein,
membrane, and sub-cellular structure in
cytosol and protecting cellular function
Glycine Betaine
1. Glycine betaine is a fully N-methyl-substituted
quaternary ammonium derivative of glycine
2. Glycine betaine is accumulated at high level in
response to abiotic stress mainly to osmotic
stress
3. Glycine betaine is abundant mainly in chloroplast
where it plays a vital in the adjusment and
protection of thylakoid membrane to maintain
photosynthesis efficiency
Trehalose
1. It is non reducing disaccharide sugar
and a compatible solute composed of
two molecules of glucose
2. It is well-known as an abiotic stress
protectant
Manitol
1. It is widely distributed sugar alcohol
2. It is synthesized in mature leaves
3. It is transported to sink tissue where it
can be either stored or oxidized to
mannose
Physiological Stress Responses
Stress resistance:
The ability of the organism to survive at the unfavourable factor
Types of Resistance
• Stress avoidance
Plant reduce the metabolic activity resulting in dormant state upon
exposure to extreme stress
In the whole growth process does not meet with the face of
adversity
• Stress tolerance
Plants have mechanism that maintain high metabolic activity similar
to the absence of stress under mild stress and reduced activity
under severe stress
Plant has a capacity of environmental stress defense, and a variety
❤
of physiological processes remain normal
Important concepts of stress
physiology
Acclimation (Hardening off)
Cross Resistance
Adaptation
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Acclimation
• Inducible responses that enable an organism to tolerate an
unfavorable or lethal change in their environment
• Increased stress tolerance as a result of prior exposure to
a stress condition
• Plant have an incredible ability to adjust physiological and
structural attributed on the scale of seconds or seasons
within a single genotypes
Example:
heat shock response
Cross Resistance
• Tolerance to a usually toxic substance as a result
of exposure to a similarly acting substance
• Tolerance to a stress based on exposure to a
previous stress event of a different nature
Example:
1. Pesticide
2. Antibiotics
Adaptation
• Genetically determined level of resistance acquired
by a process of selection over many generations
• Favorable gene combination in plant that inhabit
stress full environment
• Evolutionary changes that enable an organism to
exploit a certain niche. These include modification
of existing genes, as well as gain/loss of genes.
For example:
thermo-stable enzymes in organisms that tolerate
high temperature
Physiological approach to
breeding
 It has an advantage over empirical for yield per se because
it increases the probability of crosses resulting in additive
gene action for stress adaptation
 Individual traits must be conceptualized and defined in term
of:
a. the stage of development
b. specific attribute to the target environment
a. Their potential contribution to yield
 Physiological approach has merit over genetic approach for
the very simple reason that there is a lack of in-depth
understanding of the genetic basis stress adaptation
Physiological traits associated with
grain yield under stress
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


Remobilization of carbohydrates
Canopy temperature
Ground cover
Chlorophyll protection or stay green
The relative yield performance of the genotype in stress
and favorable conditions seems to be a common
starting point in identifying desirable genotypes
Two general approaches to determine
physiological traits associated with crop
performance under stress conditions
1. Proceed from observed yield different
to investigate of possible physiological
cause
2. Define an ideotype for a particular
stress environment
based
on
understanding of physiological process
Limited success of tranditional breeding
approaches for stress tolerance
1. The focus has been on yield rather than on specific traits
2. Difficulties in breeding for tolerance traits, which is included
complexities introduced by GEI and the relatively infrequent
use of simple physiological traits as measure of tolerance
3. Desired traits can only be introduced from closely related
species
4. Physiological traits have been seldom used as true criteria
selection, due to the difficulty of their measure on practical
breeding programs
Physiological approach of Plant
Breeding
Ideotype Breeding:
Plan of the phenotype of the cultivars that will
perform optimally in a specific set of climate,
soil, biotic and socio cultural condition
Integrated Stress Breeding Approaches
1. Indentifying stress problem
2. Developing screening technology
3. Indentifying stress tolerance traits and
their association yield
4. Screening germplasm for suitable
sources of variability of traits
5. Utilization of associated traits in the
breeding program
Ideotype Breeding
Ideotype breeding aimed at modifying the plant architecture is a timetested strategy to achieve increases in yield potential. Thus, selection for
short statured cereals such as wheat, rice, and sorghum resulted in
doubling of yield potential. Yield potential is determined by the total dry
matter or biomass and the harvest index (HI). Tall and traditional rices
had HI of around 0.3 and total biomass of about 12 tons per hectare.
Thus, their maximum yield was 4 tons per hectare. Their biomass could
not be increased by application of nitrogenous fertilizers as the plants
grew excessively tall, lodged badly and the yield decreased instead of
increasing. To increase the yield potential of topical rice it was necessary
to improve the harvest index and nitrogen responsiveness by increasing
the lodging resistance. This was accomplished by reducing the plant
height through incorporation of a recessive gene sd1 for short stature
Ideotype Breeding
To increase the yield potential of rice further, a new plant type was
conceptualized in 1988 at IRRI. Modern semi-dwarf rices produce a
large number of unproductive tillers and excessive leaf area that cause
mutual shading, and reduce canopy photosynthesis and sink size,
especially when they are grown under direct sowing conditions. To
increase the yield potential of these semi-dwarf rices,
IRRI scientists proposed further modifications of plant architecture with
following characteristics:
1. Low tillering,( 9-10 tillers for transplanted conditions)
2. No unproductive tillers
3. 200-250 grains per panicle
4. Dark green, thick and erect leaves
5. Vigorous and deep root system
Response
1. Species
2. Genotype
3. Developmental stage