Biotic stress inside the plants molecular level
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Plants face both abiotic stresses like drought, heat and salinity as well as biotic stresses from other living organisms like herbivores, fungi and bacteria. In response to biotic stress, plants have developed defense strategies including producing secondary metabolites and activating immune responses. One response is hypersensitive response (HR) where cells near the infection site undergo programmed cell death (PCD) to limit the spread of pathogens. HR involves producing pathogenesis-related proteins, phytoalexins, and changing cell wall composition. It is triggered by oxidative bursts of reactive oxygen species and nitric oxide that induce PCD through signaling pathways.
Biotic stress inside the plants molecular level
- 1. Biotic stress in plants Vimal priya subramanian 1st M.sc Botany 18MBO027
- 2. Biotic stress in plants Plants have various stress like drought , cold heat, salinity, etc which are called abiotic stress Similarly plants are affected by some other living organism such as herbivores, fungal and bacteria etc This stresses caused by these organisms are known as biotic stresses.
- 3. Immune system in plants • Plants developed defense strategies including production of secondary metabolites to wards off insects and disease. # Hyper Sensitive Response(HR) # Secondary Acquired Resistance (SAR)
- 5. HR
- 6. HYPER SENSITIVE RESPONCE • On being attacked by insects or a pathogenic micro organism, tpically a plant reponds with 1 • Pathogenesis- related proteins. 2 • Bio synthesis of phytoalexins 3 & 4 • Changes in composition and physical properties of host cell wall • Programed cell death (PCD)
- 7. PATHOGENESIS-RELATED (PR)PROTEIN • These are products of defence related genes that are activated by microbial infection and include hydrolytic enzymes such as • *proteinase inhibitors –which inhibit activities of proteolytic enzymes secrete by the pathogen,and • * lytic enzyme -such as glucanases, chitinases, and other hydrolases that attack and degrade the cell walls of the pathogen.
- 8. Bio synthesis of phytoalexins • The microbial infection also activaes genes hat encode enzymes for the synthesis of phytolexins. Phytolexins are a chemical group of secondary metabolites (chiefly isoflavonoids ) with strong antimicrobial activity. • The isoflavonoids medicarpin from alfalfa and glyceolin from soybean and sesquiterpenes such as rishitin from tomato and potato and capsidiol from tobacco and pepper are well known examples of phytolexins.
- 9. PHYTOLEXIN
- 10. Changes in composition and physical properties of host cell walls. • In response to pathogen invasion, lignin,callose, suberin and some hudroxy- proline rich glycoproteins are synthesized and accumulted in host cell walls to strengthen the latter and physically blocking he spread of the invading pathogen
- 11. CHANGES IN CELL WALL &CHEMICAL COPOSITION
- 12. Programmed cell death (PCD) • The hypersensitive response culminates in rapid death of cells around the infection site depriving pathogen of the nutrient supply and limiting its spread in host plant and leaving necrotic lesions (small regions of dead tissues) at the site of invasion. The rest of the plant howevr, reains unaffected.
- 13. PCD
- 14. PCD • Recent researches have shown that the hyper sensitive response is preceded by accumulation of nitric oxide (NO)and active oxygen species (including the superoxide anion O2 – hydregen peroxide H2O2 and hydroxyl radical OH)
- 15. PCD • The production of active oxygen specie(known as oxidative burst) and nitric oxide (secondary mesanger in many signelling pathways in animals and plants ) appears to be prerequisite for activation of hypersensitive response. Induction of PCD is prevented in absence of any of these two signals.
- 16. PCD
- 17. PCD • It is belived that a plasma membrane located NADPH dependent oxidase reduces the O2 to produce superoxide anions. The latter in turn are converted into hydrogen peroxide and hydroxyl radicals. The active oxygen species especially the hydroxyl radicals ,ay contribute to PCD as part of the hypersensitive response or these may act to kill the pathogen directly.
- 18. pcd • a transient increase in cytosolic ca2+ concentration is required for the activity of the activity of the ensyme NO synthase which converts the amino acid arginine into nitric oxide. • Consequent to pathogen infection, both oxidative burst and NO production are ativated by a transient change in plasmamemnrane pereanlility resulting in infux of H+ and ca2+ ions into the cell and efflux of k+ and Cl- ions
- 19. PCD
- 20. THANKING YOU Refference-JAIN;1974;Plant physioloy;584 to 585 One book is equal to 100 good friends But one good friend is equal to a library. -APJ. Abdulkalam