LEA(late embryogenesis abundant) protiens and heat shock

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: B r a h mesh Reddy B R 8 7 3 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 protein s

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 LEA proteins might act as hydration buffers, slowing down the rate of water loss during dehydration. During partial drought, osmotic or freezing stress, hydration buffers allow sufficient water activity for proteins to retain function 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…