heat shock drought stress in plants abiotic stress ate embryogenesis abundant

1. University Of Agricultural Sciences, Dharwad
College Of Agriculture, Vijayapur
LEA Proteins & Heat Shock
Under drought Stress
Submitted by:
Brahmesh Reddy B R
8073
B 1 batch

2. Abiotic Stress & LEA Proteins
• In nature, abiotic stresses, such as drought, high temperature, salinity, cold, and
heavy metal pollution, have a serious effect on plant growth and development, with
drought, high temperature, and salinity being associated with water limitation.
• High temperature damages cell membrane integrity, inhibits photosynthesis, and
leads to cellular aging and death. Salt stress decreases total biomass, limits
photosynthesis and affects the metabolic system.
• Higher plants have evolved a wide variety of defense mechanisms in response to
adverse conditions, often manifesting in the synthesis of a series of functional
proteins to reduce damage and protect cells.
• For example, accumulation of late embryogenesis abundant (LEA) proteins is an
important response to abiotic stress.

3. Late Embryogenesis Abundant (LEA)
Proteins
• As the name suggests, Late Embryogenesis Abundant proteins
were originally discovered in the late stages of embryo
development in cotton seeds .
• In plants, most of LEA proteins and their mRNAs accumulate
to high concentrations in embryo tissues during the last stages
of seed development when desiccation occurs

4. LEA Protein Functions
• There is an extensive bibliography showing the correlation between the
expression of LEA proteins or their genes with stress resistance.
• Many studies show the protection conferred by LEA proteins during
salt and osmotic stress.
• Introduction of heterologous LEA proteins into plants and
microorganisms results in an enhanced stress tolerance.

5. • Transgenic approaches have shown that over-expression of LEA
proteins from different species in tobacco, rice, wheat, maize, lettuce or
cabbage produces improve abiotic stress resistant phenotypes.
• LEA proteins have been suggested to act as stabilizers, hydration
buffers, membrane protectants, antioxidants, organic glass formers
and/or ion chelators

6. Protein Protection function
• LEA proteins have the capacity to protect target proteins from
inactivation and aggregation during water stress.
• A role in protein stabilization is supported by some LEA
proteins which preserve enzyme activity in vitro after partial
dehydration, desiccation or freezing.
• One mechanism of protection is the prevention of water
stress induced aggregation of proteins

7. Membrane Protection Function
•During desiccation membrane protection is essential to
preserve the cellular and organellar integrity.
•Some LEA proteins could contribute with sugars to H-bonding
networking and protect membranes in the dry state

8. Ion Binding and Antioxidant Function
• One consequence of dehydration is the increase in
concentration of intracellular components, including ions.
• Increased ionic concentration can affect macromolecular
structure and function.
• It has been proposed that LEA proteins, because of their many
charged amino acid residues might act to sequester ions

9. Other Functions
1. LEA proteins might act as hydration buffers, slowing down the
rate of water loss during dehydration.
2. During partial drought, osmotic or freezing stress, hydration
buffers allow sufficient water activity for proteins to retain
function
3. In a desiccating cell, when the water content falls below 10% on
a dry weight basis, the cytoplasm vitrifies and enters in the
“glassy state”. In plants the formation of intracellular glasses is
indispensable for survival in the dry state (seeds and pollens).

10. 4. LEA proteins accumulate to high levels in seeds (2% - 4% of the water
soluble proteome) and they increase the density of the sugar glasses by
strengthening the hydrogen-bonding of the sucrose/LEA mixture.
5. Thus a potential role of LEA proteins is their contribution to the formation
of biological glasses.

11. Heat Shock Proteins
In plants, one of the major problems caused by
abiotic stress is protein dysfunction. Heat-shock proteins are a group of
proteins that are expressed at high levels when exposed to stress.

12. Functions
• During stress condition, heat-shock proteins (Hsps) are
responsible for protein folding, translocation and assembly,
degradation, stabilize proteins and membrane
• They can play a crucial role in protecting plants against stress
by reestablishing normal protein conformation and thus
cellular homeostasis.
• Hsps are able to protect the cells from injury and can also
facilitate recovery and survival after return to normal growth
conditions

13. • Hsps have a role in maintaining the membrane integrity
during stress.
• The correlation between synthesis and accumulation of Hsps
and heat tolerance suggests but does not prove that these are
related.

14. Thank You…