logging in or signing up phytoalexins kavitej Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 2433 Category: Science & Tech.. License: All Rights Reserved Like it (13) Dislike it (0) Added: May 14, 2009 This Presentation is Public Favorites: 0 Presentation Description No description available. Comments Posting comment... By: fortika (5 month(s) ago) Thank you very much ! I`ll be grateful if you send me that Saving..... Post Reply Close Saving..... Edit Comment Close By: fortika (12 month(s) ago) thank you for presentation Saving..... Post Reply Close Saving..... Edit Comment Close By: matinok (12 month(s) ago) its a good presentation. would you send me this. thanks Saving..... Post Reply Close Saving..... Edit Comment Close By: rlazz (15 month(s) ago) Great job. Thank you very much ! I`ll be grateful if you send me that. Saving..... Post Reply Close Saving..... Edit Comment Close By: skalyani (16 month(s) ago) plz send phytoalexin powerpoint to my email its a very nice presentation help me in clearing my views Saving..... Post Reply Close Saving..... Edit Comment Close loading.... See all Premium member Presentation Transcript SEMINARONHOST – PARASITE INTERACTIONS : SEMINARONHOST – PARASITE INTERACTIONS PRESENTED BY P.LEELA LAVANYA IVth SEM M.Sc MICROBIOLOGY CONTENTS : CONTENTS INTRODUCTION DEFENCE MECHANISMS PRODUCTION OF PHYTOALEXINS INVOLVEMENT OF ELICITOR MOLECULES CONCLUSION INTRODUCTION : INTRODUCTION Parasites to obtain their food establish a close contact with their host plants. Host – parasite interactions can be inhibited or completely hindered if the host is able to protect the pathogen by active or passive processes. The defence mechanisms of plants against pathogens includes: a) Morphological or structural defence mechanism b) Biochemical defence mechanism Morphological or structural defece mechanism: : Morphological or structural defece mechanism: The first line of defence against pathogens is the surface barrier, which a pathogen must penetrate before it can cause infection. If pathogen gains entry into the host, its movement and further spread is checked through parenchymatous cells and in the vascular diseases through the lumen of the xylem vessels. such defence structures may be present before penetration or afterwards as a result of the infection of the host and the pathogen. Defence structures existing before infection: : Defence structures existing before infection: Waxes and cuticles Structure of epidermal cell wall Structure of natural openings Internal structures barriers to pathogen invasion Defence structures formed after infection: Formation of cork layers Formation of Tyloses Formation of Abscission layers Gum deposition Sheathing of Hyphae. Biochemical defence mechanism: : Biochemical defence mechanism: Inhibitors released by the plant in its environment Defence through absence of common antigens Productions of phytoalexins Phytoalexins are phenolic compounds, which are not present in healthy plants but are produced upon stimulation of a plant by a pathogen or by a mechanical or chemical injury . The term phytoalexin is derived from Greek- phyto meaning plant and alexin means warding off compound. They are antimicrobial low molecular weight compounds. More toxic to non pathogens than to the pathogens. Slide 7: The initial work of Mueller and Berger (1940) laid foundation of the concept of Phytoalexins.The conclusions are as follows: a) phytoalexin is formed only when the host cells come into contact with the parasite. b) the defence reaction occurs only in the living cells. c) the inhibitory material is a chemical substance & may be regarded as a product of necrobiosis of the host cell. d) phytoalexin is non-specific in its toxicity. e) the resistant state is not inherited. f) the defence reaction is confined to the tissue colonized by the fungus and its immediate neighbourhood. Cont…….. : Cont…….. Hundreds of Phytoalexins have been characterized , mostly widespread in Fabaceae and Solanaceae families. They have not been reported from families of poaceae and cucurbitaceae. Two hypotheses were put forward to explain the mechanism of the induction of Phytoalexins: A) De novo synthesis of enzymes B) Activation or activity control of enzymes already formed Phytoalexins are fungistatic rather than fungicidal They are chemically diverse , but large number of them are products of the shikimic acid pathway. Cont…… : Cont…… Gossypol from cotton, casbene from castor bean and rishitin from plants in the Solanaceae are Phytoalexins biosynthesized by the mevalonic acid pathway. Phytoalexins are typically synthesized in cells surrounding the site of infection and accumulate to high levels in dead and dying cells. Induction of phytoalexin genes and enzymes is frequently transient , reaching a peak some hours after attempted infection and then declining. Alteration of the expression of phytoalexin biosynthetic genes is now feasible , through over expression by introduction of multiple copies, constitutive expression using strong promoters or antisense technology. TYPES OF PHYTOALEXINS: : TYPES OF PHYTOALEXINS: Ipomoeamarone: It is an abnormal sesquiterpinoid induced in sweet potato tissue infected with black rot fungus Ceratocystis fimbriata. It has a striking inhibitory effect on the fungus even in 0.1% concentrations. More phytoalexin is produced in the resistant varieties than in susceptible ones. CH3 CH2-CO-CH2-CH O CH3 CH3 O O Slide 11: 2) Pisatin: It has the chromocoumarin ring system and is a phenolic ether. produced by the exposed endocarp of the detached pea in response to inoculation with many fungi or injury. Production of pisatin by peapods inoculated with Monilia fructicola , a non pathogen is reduced at high temperature &on anaerobic storage. It is a weak antibiotic with broad spectrum. Slide 13: 3) Phaseollin: It is similar to pisatin in chemistry and function. It is fungicidal at high concentrations and fungistatic at low concentrations against S.fructigena. A no. of compounds such as phaseollidin , phaseollinisoflavan and kievitone which are structurally similar to phaseollin have been identified. Slide 14: 4) Glyceollin: produced in soybean plants infected with the fungus Phytophthora megasperma f.sp.glycinea. Inoculation of fungal races resulted in higher concentrations in incompatible host cultivars than in inoculations of fungal races on compatible cultivars. Due to reduced biodegradation rather than increased biosynthesis. Slide 15: 5) Isocoumarin: isolated from carrot root tissues inoculated with a fungus non-pathogenic to carrot, Ceratocystis fimbriata. It can also be produced in response to a no.of non-pathogenic microorganisms such as C.ulmi, Helminthosporium carbonum, Fusarium oxysporum f.sp.lycopersici & Thielaviopsis basicola. chemically related to the pterocarpan phaseollin. Slide 16: 6)Trifolirhizin: It is a new glucoside which has been isolated from the roots of red cloves. Its structure indicates that it is chemically closely related to pisatin. It has the formula C16H12O5. Slide 17: 7) Rishitin: Muller and Boerger(1940) were the first to show that the potato tubers carying the gene R1 for late blight resistance responded when inoculated with avirulent race of P.infestans by producing a phytoalexin that inhibited the development of a virulent race. It is a bicyclic non-sesquiterpine alcohol. Slide 18: 8) Gossypol: It is an ether soluble phenol . It is produced in diseases like black spot of rose(Diplocarpon rosa),leaf spot of wheat (Septoria tritici). Slide 19: 9) Xanthotoxin: Isolated from parsnip root discs inoculated with C.fimbriata Inoculation with other non pathogens resulted in production of xanthotoxin. Slide 20: 10) Capsidiol: it is a sequisterpene phytoalexin produced in pepper fruits inoculated with a non – pathogenic fungi. Produced concentrations are sufficient to inhibit these fungi in vitro. Slide 21: 11) Medicarpin: Alfalfa (Medicago sativa) inoculated with a series of pathogens and non pathogens have been studied. The antifungal compound was isolated and identified as Medicarpin. INVOLVEMENT OF ELICITORS : INVOLVEMENT OF ELICITORS Defined as substances of biotic origin which induce a defence response. Biochemically, they were defined by Noel Keen as inducers of phytoalexin biosynthesis. They also inducers of 1) Hypersensitive response 2) Lignification 3) PR protein . A particular elicitor does not necessarily elicit all defence responses. Ethylene , triggers PR-protein synthesis but not phytoalexin accumulation. Slide 23: The elicitor interacts with a membrane receptor to initiate a variety of cell responses that culminate in the killing of the pathogen and limit its spread. The elicitor interacts with a membrane receptor to initiate a variety of cell responses that culminate in the killing of the pathogen and limit its spread. Slide 24: Examples of elicitors: a) proteins, peptides b) carbohydrates c) Beta glucans d) oligo galacturans e) chitosan f) fatty acids, glycosyl lipids Elicitors can be categorized into Non-specific and Specific elicitors. Non –specific – induce host defences in a broad range of host species. It includes: a) Abiotic b) biotic Slide 25: Abiotic elicitors: . It includes heavy metal ions or UV light. They induce stress response in exposed tissues or alternatively increase the plants susceptibility to infection. They also strongly inhibit glyceollin degradation (by Hgcl2) Biotic elicitors: It includes cell wall fragments released from fungi and bacteria, hydrolytic enzymes of plant or pathogen origin, some peptides,and glycoproteins. These induce defence responses in a range of host species. Slide 26: Specific elicitors: Enable defence against a very specific pathogen & are conditioned by avirulence genes in that pathogen. Avirulence genes determine the pathogens host range. Function only in the presence of another set of genes i.e., the hypersensitive response and pathogenecity (Hrp) gene clusters. Presence of non- specific elicitors may amplify the defence response. Fungi, including dead spores & extracts and to a lesser extent bacteria & viruses can act as elicitors of phytoalexin accumulation. Majority of elicitors are non – selective. Slide 27: Recently, two elicitors have been demonstrated to be host selective. One is the gene product of the avr9 gene of Cladosporium fulvum. it causes necrosis only on tomato varieties containig cf9. The second is controlled by the avr D gene of the bacterium ps.syringae pv. Tomato. In many cases distinction between an elicitor and a toxin is not clear cut. This is because cell death is a characteristic of both resistance and susceptability eventually. Slide 30: Phytoalexins in Recent Research: Allixin (3-hydroxy-5-methoxy-6-methyl-2-penthyl-4H-pyran-4-one), a non-sulfur containing compound having a g-pyrone skeleton structure, was the first compound isolated from garlic as a phytoalexin, a product induced in plants by continuous stress. shown to have unique biological properties, such as: a) anti-oxidative effects, b) anti-microbial effects, c) anti-tumor promoting effects, d) inhibition of aflatoxin B2 DNA binding, and e) neurotrophic effects. Slide 31: Allixin showed an anti-tumor promoting effect in vivo, inhibiting skin tumor formation by TPA in DMBA initiated mice. Analogs of this compound have exhibited anti tumor promoting effects in in vitro experimental conditions. Here in, allixin and/or its analogs may be expected useful compounds for cancer prevention or chemotherapy agents for other diseases. CONCLUSION : CONCLUSION Host parasite specific resistance is determined by the interaction between products of pathogen avirulence genes, specific elicitors and products of host resistance genes. Host gene expression begins within minutes , or even seconds of exposure to elicitor or pathogen. A diverse range of elicitors can induce a common set of responses in the host which suggests that second messengers are involved in the signaling pathway between pathogen attack and host response. REFERENCES : REFERENCES PLANT PATHOLOGY - R.S.Mehrotra, Ashok agarwal 2nd edition, Tata.Mc-Graw-Hill, Publishing company Ltd. New Delhi. PLANT BIOCHEMISTRY – Edited by Dey & Harborne Harcourt ASIA PVT.LTD,Academic Press,A Carcourt Publishers company. SOIL MICROBIOLOGY – N.S.Subba Rao , 4th edition of soil microorganisms & plant growth, OXFORD & IBH Publishing Co. Pvt,Ltd. New Delhi. http://bugs.bio.usyd.edu.au/PlantPathology/infection/plant_defenses/active_def.html#pathRecognition Slide 34: THANK U ONE AND ALL You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.
phytoalexins kavitej Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 2433 Category: Science & Tech.. License: All Rights Reserved Like it (13) Dislike it (0) Added: May 14, 2009 This Presentation is Public Favorites: 0 Presentation Description No description available. Comments Posting comment... By: fortika (5 month(s) ago) Thank you very much ! I`ll be grateful if you send me that Saving..... Post Reply Close Saving..... Edit Comment Close By: fortika (12 month(s) ago) thank you for presentation Saving..... Post Reply Close Saving..... Edit Comment Close By: matinok (12 month(s) ago) its a good presentation. would you send me this. thanks Saving..... Post Reply Close Saving..... Edit Comment Close By: rlazz (15 month(s) ago) Great job. Thank you very much ! I`ll be grateful if you send me that. Saving..... Post Reply Close Saving..... Edit Comment Close By: skalyani (16 month(s) ago) plz send phytoalexin powerpoint to my email its a very nice presentation help me in clearing my views Saving..... Post Reply Close Saving..... Edit Comment Close loading.... See all Premium member Presentation Transcript SEMINARONHOST – PARASITE INTERACTIONS : SEMINARONHOST – PARASITE INTERACTIONS PRESENTED BY P.LEELA LAVANYA IVth SEM M.Sc MICROBIOLOGY CONTENTS : CONTENTS INTRODUCTION DEFENCE MECHANISMS PRODUCTION OF PHYTOALEXINS INVOLVEMENT OF ELICITOR MOLECULES CONCLUSION INTRODUCTION : INTRODUCTION Parasites to obtain their food establish a close contact with their host plants. Host – parasite interactions can be inhibited or completely hindered if the host is able to protect the pathogen by active or passive processes. The defence mechanisms of plants against pathogens includes: a) Morphological or structural defence mechanism b) Biochemical defence mechanism Morphological or structural defece mechanism: : Morphological or structural defece mechanism: The first line of defence against pathogens is the surface barrier, which a pathogen must penetrate before it can cause infection. If pathogen gains entry into the host, its movement and further spread is checked through parenchymatous cells and in the vascular diseases through the lumen of the xylem vessels. such defence structures may be present before penetration or afterwards as a result of the infection of the host and the pathogen. Defence structures existing before infection: : Defence structures existing before infection: Waxes and cuticles Structure of epidermal cell wall Structure of natural openings Internal structures barriers to pathogen invasion Defence structures formed after infection: Formation of cork layers Formation of Tyloses Formation of Abscission layers Gum deposition Sheathing of Hyphae. Biochemical defence mechanism: : Biochemical defence mechanism: Inhibitors released by the plant in its environment Defence through absence of common antigens Productions of phytoalexins Phytoalexins are phenolic compounds, which are not present in healthy plants but are produced upon stimulation of a plant by a pathogen or by a mechanical or chemical injury . The term phytoalexin is derived from Greek- phyto meaning plant and alexin means warding off compound. They are antimicrobial low molecular weight compounds. More toxic to non pathogens than to the pathogens. Slide 7: The initial work of Mueller and Berger (1940) laid foundation of the concept of Phytoalexins.The conclusions are as follows: a) phytoalexin is formed only when the host cells come into contact with the parasite. b) the defence reaction occurs only in the living cells. c) the inhibitory material is a chemical substance & may be regarded as a product of necrobiosis of the host cell. d) phytoalexin is non-specific in its toxicity. e) the resistant state is not inherited. f) the defence reaction is confined to the tissue colonized by the fungus and its immediate neighbourhood. Cont…….. : Cont…….. Hundreds of Phytoalexins have been characterized , mostly widespread in Fabaceae and Solanaceae families. They have not been reported from families of poaceae and cucurbitaceae. Two hypotheses were put forward to explain the mechanism of the induction of Phytoalexins: A) De novo synthesis of enzymes B) Activation or activity control of enzymes already formed Phytoalexins are fungistatic rather than fungicidal They are chemically diverse , but large number of them are products of the shikimic acid pathway. Cont…… : Cont…… Gossypol from cotton, casbene from castor bean and rishitin from plants in the Solanaceae are Phytoalexins biosynthesized by the mevalonic acid pathway. Phytoalexins are typically synthesized in cells surrounding the site of infection and accumulate to high levels in dead and dying cells. Induction of phytoalexin genes and enzymes is frequently transient , reaching a peak some hours after attempted infection and then declining. Alteration of the expression of phytoalexin biosynthetic genes is now feasible , through over expression by introduction of multiple copies, constitutive expression using strong promoters or antisense technology. TYPES OF PHYTOALEXINS: : TYPES OF PHYTOALEXINS: Ipomoeamarone: It is an abnormal sesquiterpinoid induced in sweet potato tissue infected with black rot fungus Ceratocystis fimbriata. It has a striking inhibitory effect on the fungus even in 0.1% concentrations. More phytoalexin is produced in the resistant varieties than in susceptible ones. CH3 CH2-CO-CH2-CH O CH3 CH3 O O Slide 11: 2) Pisatin: It has the chromocoumarin ring system and is a phenolic ether. produced by the exposed endocarp of the detached pea in response to inoculation with many fungi or injury. Production of pisatin by peapods inoculated with Monilia fructicola , a non pathogen is reduced at high temperature &on anaerobic storage. It is a weak antibiotic with broad spectrum. Slide 13: 3) Phaseollin: It is similar to pisatin in chemistry and function. It is fungicidal at high concentrations and fungistatic at low concentrations against S.fructigena. A no. of compounds such as phaseollidin , phaseollinisoflavan and kievitone which are structurally similar to phaseollin have been identified. Slide 14: 4) Glyceollin: produced in soybean plants infected with the fungus Phytophthora megasperma f.sp.glycinea. Inoculation of fungal races resulted in higher concentrations in incompatible host cultivars than in inoculations of fungal races on compatible cultivars. Due to reduced biodegradation rather than increased biosynthesis. Slide 15: 5) Isocoumarin: isolated from carrot root tissues inoculated with a fungus non-pathogenic to carrot, Ceratocystis fimbriata. It can also be produced in response to a no.of non-pathogenic microorganisms such as C.ulmi, Helminthosporium carbonum, Fusarium oxysporum f.sp.lycopersici & Thielaviopsis basicola. chemically related to the pterocarpan phaseollin. Slide 16: 6)Trifolirhizin: It is a new glucoside which has been isolated from the roots of red cloves. Its structure indicates that it is chemically closely related to pisatin. It has the formula C16H12O5. Slide 17: 7) Rishitin: Muller and Boerger(1940) were the first to show that the potato tubers carying the gene R1 for late blight resistance responded when inoculated with avirulent race of P.infestans by producing a phytoalexin that inhibited the development of a virulent race. It is a bicyclic non-sesquiterpine alcohol. Slide 18: 8) Gossypol: It is an ether soluble phenol . It is produced in diseases like black spot of rose(Diplocarpon rosa),leaf spot of wheat (Septoria tritici). Slide 19: 9) Xanthotoxin: Isolated from parsnip root discs inoculated with C.fimbriata Inoculation with other non pathogens resulted in production of xanthotoxin. Slide 20: 10) Capsidiol: it is a sequisterpene phytoalexin produced in pepper fruits inoculated with a non – pathogenic fungi. Produced concentrations are sufficient to inhibit these fungi in vitro. Slide 21: 11) Medicarpin: Alfalfa (Medicago sativa) inoculated with a series of pathogens and non pathogens have been studied. The antifungal compound was isolated and identified as Medicarpin. INVOLVEMENT OF ELICITORS : INVOLVEMENT OF ELICITORS Defined as substances of biotic origin which induce a defence response. Biochemically, they were defined by Noel Keen as inducers of phytoalexin biosynthesis. They also inducers of 1) Hypersensitive response 2) Lignification 3) PR protein . A particular elicitor does not necessarily elicit all defence responses. Ethylene , triggers PR-protein synthesis but not phytoalexin accumulation. Slide 23: The elicitor interacts with a membrane receptor to initiate a variety of cell responses that culminate in the killing of the pathogen and limit its spread. The elicitor interacts with a membrane receptor to initiate a variety of cell responses that culminate in the killing of the pathogen and limit its spread. Slide 24: Examples of elicitors: a) proteins, peptides b) carbohydrates c) Beta glucans d) oligo galacturans e) chitosan f) fatty acids, glycosyl lipids Elicitors can be categorized into Non-specific and Specific elicitors. Non –specific – induce host defences in a broad range of host species. It includes: a) Abiotic b) biotic Slide 25: Abiotic elicitors: . It includes heavy metal ions or UV light. They induce stress response in exposed tissues or alternatively increase the plants susceptibility to infection. They also strongly inhibit glyceollin degradation (by Hgcl2) Biotic elicitors: It includes cell wall fragments released from fungi and bacteria, hydrolytic enzymes of plant or pathogen origin, some peptides,and glycoproteins. These induce defence responses in a range of host species. Slide 26: Specific elicitors: Enable defence against a very specific pathogen & are conditioned by avirulence genes in that pathogen. Avirulence genes determine the pathogens host range. Function only in the presence of another set of genes i.e., the hypersensitive response and pathogenecity (Hrp) gene clusters. Presence of non- specific elicitors may amplify the defence response. Fungi, including dead spores & extracts and to a lesser extent bacteria & viruses can act as elicitors of phytoalexin accumulation. Majority of elicitors are non – selective. Slide 27: Recently, two elicitors have been demonstrated to be host selective. One is the gene product of the avr9 gene of Cladosporium fulvum. it causes necrosis only on tomato varieties containig cf9. The second is controlled by the avr D gene of the bacterium ps.syringae pv. Tomato. In many cases distinction between an elicitor and a toxin is not clear cut. This is because cell death is a characteristic of both resistance and susceptability eventually. Slide 30: Phytoalexins in Recent Research: Allixin (3-hydroxy-5-methoxy-6-methyl-2-penthyl-4H-pyran-4-one), a non-sulfur containing compound having a g-pyrone skeleton structure, was the first compound isolated from garlic as a phytoalexin, a product induced in plants by continuous stress. shown to have unique biological properties, such as: a) anti-oxidative effects, b) anti-microbial effects, c) anti-tumor promoting effects, d) inhibition of aflatoxin B2 DNA binding, and e) neurotrophic effects. Slide 31: Allixin showed an anti-tumor promoting effect in vivo, inhibiting skin tumor formation by TPA in DMBA initiated mice. Analogs of this compound have exhibited anti tumor promoting effects in in vitro experimental conditions. Here in, allixin and/or its analogs may be expected useful compounds for cancer prevention or chemotherapy agents for other diseases. CONCLUSION : CONCLUSION Host parasite specific resistance is determined by the interaction between products of pathogen avirulence genes, specific elicitors and products of host resistance genes. Host gene expression begins within minutes , or even seconds of exposure to elicitor or pathogen. A diverse range of elicitors can induce a common set of responses in the host which suggests that second messengers are involved in the signaling pathway between pathogen attack and host response. REFERENCES : REFERENCES PLANT PATHOLOGY - R.S.Mehrotra, Ashok agarwal 2nd edition, Tata.Mc-Graw-Hill, Publishing company Ltd. New Delhi. PLANT BIOCHEMISTRY – Edited by Dey & Harborne Harcourt ASIA PVT.LTD,Academic Press,A Carcourt Publishers company. SOIL MICROBIOLOGY – N.S.Subba Rao , 4th edition of soil microorganisms & plant growth, OXFORD & IBH Publishing Co. Pvt,Ltd. New Delhi. http://bugs.bio.usyd.edu.au/PlantPathology/infection/plant_defenses/active_def.html#pathRecognition Slide 34: THANK U ONE AND ALL