Phytoalexins
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Phytoalexins are toxin-like substances produced by plants in response to infection by parasites and physiological stresses. They help confer protection against infecting parasites. Hundreds of phytoalexins have been characterized, mostly in legume and nightshade plant families. Phytoalexins are activated only after infection and develop in response to contact between the host cell and pathogen. They are chemically diverse but many are products of the shikimic acid pathway. Phytoalexins act as fungistatic compounds rather than fungicidal compounds.
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Phytoalexins
Phytoalexins are toxic chemical compounds produced by plants in response to infection by parasites or pathogens. They act as a defense mechanism against invading fungi or bacteria. Hundreds of phytoalexins have been characterized, mostly in the families Fabaceae and Solanaceae. They are produced through the shikimic acid pathway and are often fungistatic rather than fungicidal. Important phytoalexins include pisatin, phaseollin, glyceollin and gossypol. In addition to their role in plant defense, many phytoalexins have potential health benefits for humans such as antioxidant, anti-inflammatory and anticancer properties.
Phytoalexins
- Phytoalexins are antimicrobial compounds produced by plants after exposure to microorganisms or abiotic stress. They are chemically diverse and fall into classes like terpenoids and alkaloids.
- The concept of phytoalexins was formalized in 1941 after observing that bean tissue produced inhibitory compounds when exposed to a fungal pathogen. Phytoalexins restrict pathogen growth at infection sites.
- Induction of phytoalexins involves MAP kinase signaling cascades and transcription factors like WRKY33 regulating genes in biosynthesis pathways. Camalexin production in Arabidopsis in response to pathogens depends on WRKY33 phosphorylation by MPK3/MPK6.
Role of enzyme in plant disease
This document summarizes the roles of enzymes, toxins, exopolysaccharides, and polypeptide signals in plant disease development. It discusses how enzymes secreted by pathogens break down plant cell walls and nutrients, allowing pathogens to utilize these resources. Different types of enzymes like hydrolases, hemicellulases, and proteolytic enzymes are described. Toxins directly act on and kill plant cells, causing disease symptoms. Exopolysaccharides protect bacterial biofilms and provide nutrients. Finally, the polypeptide signal systemin is discussed, which activates plant defense genes and functions long-distance within the plant in response to wounding or predator attacks.
Phytoalexins
Phytoalexins are broad-spectrum antimicrobial compounds produced by plants in response to pathogen infection. They are chemically diverse and fall into classes like terpenoids, steroids, and alkaloids. Phytoalexins are synthesized de novo from primary metabolites through pathways like the shikimic acid and mevalonic acid pathways after plants detect elicitors from pathogens. They function as toxins to disrupt the metabolism and reproduction of pathogens. Their production is part of plants' general short-term response to infection and their long-term systemic acquired resistance which protects the entire plant.
PR protein by kk sahu sir
This document discusses pathogenesis-related (PR) proteins found in plants. It begins with definitions, noting that PR proteins are produced when plants are infected by pathogens and act to decrease susceptibility. It then describes 17 types of PR proteins classified into families based on their properties, with examples like chitinase and glucanase. Mechanisms of action are discussed, such as degrading fungal cell walls. The document concludes by outlining applications for transferring PR protein genes to transgenic plants to engineer resistance against pathogens like fungi and bacteria.
Biosynthesis of auxin[1]
This document summarizes information about the plant growth hormone auxin. It defines auxin as chemical substances that promote stem or root growth. The first known auxin is indole-3-acetic acid. There are two types of auxin: natural auxins produced by plants like IAA, and synthetic auxins created in labs. The document then describes the three step biosynthesis process of IAA from the amino acid tryptophan. Finally, it lists several physiological effects of auxins, including cell elongation, promotion of cell division, root growth, apical dominance, prevention of abscission, formation of seedless fruits, and regulation of plant growth movements.
Credit seminar
Plants have array of defense response against biotic stresses which could be either structural reinforcement, release of chemicals, and defense gene expression against invading organisms. The physical barriers are trichoms, waxy cuticle, thick cell wall. Once the pathogen overcomes the first line of defense, basal or innate defense response comes into play. Pathogens secrete some conserved molecules known as Pathogen Associated Molecular Pattern (PAMP/MAMP), which are recognized by transmembrane receptors present in the plasma membrane and initiate a series of signal cascade reaction which ultimately leads to activation of various defense related genes. Apart from inducing the expression of defense related genes, it also triggers a hypersensitive reaction (HR) which cause deliberate cell death at the site of infection and limit the pathogen access to water and nutrient by sacrificing a few cells in order to save the rest of the plant. Once HR is triggered, plant tissue may become highly resistant to a broad range of pathogens for an extended period of time. This phenomenon is called Systemic Acquired Resistance (SAR).
Plants respond to herbivory is a similar manner as described above. The biochemical mechanisms of defense against the herbivores are wide-ranging, highly dynamic, and are mediated both by direct and indirect defenses. The defensive compounds are either produced constitutively or in response to plant damage, and affect feeding, growth, and survival of herbivores. In addition, plants also release volatile organic compounds that attract the natural enemies of the herbivores. These strategies either act independently or in conjunction with each other. However, our understanding of these defensive mechanisms is still limited. Induced resistance could be exploited as an important tool for the pest management to minimize the amounts of insecticides used for pest control. Host plant resistance to insects, particularly, induced resistance, can also be manipulated with the use of chemical elicitors of secondary metabolites, which confer resistance to insects. By understanding the mechanisms of induced resistance, we can predict the herbivores that are likely to be affected by inducing responses. The elicitors of induced responses can be sprayed on crop plants to build up the natural defense system against damage caused by herbivores. The induced responses can also be genetically engineered, so that the defensive compounds are constitutively produced in plants challenged by the herbivory. Induced resistance can be exploited for developing crop cultivars, which readily produce the inducible response upon mild infestation, and can act as one of components of integrated pest management for sustainable crop production.
Pr protein
Pathogenesis-related (PR) proteins are a diverse group of plant proteins that are produced in greater amounts when plants are infected by pathogens or exposed to stress. There are at least 14 families of PR proteins that differ in their functions, properties, and modes of action. Some key PR proteins include PR1, PR2, and PR3. PR1 proteins have antifungal properties and may disrupt fungal membranes. PR2 are β-1,3-glucanases that degrade fungal cell walls. PR3 are chitinases that break down chitin in fungal cell walls, weakening the walls and killing fungi.
Recommended
Phytoalexins
Phytoalexins are toxic chemical compounds produced by plants in response to infection by parasites or pathogens. They act as a defense mechanism against invading fungi or bacteria. Hundreds of phytoalexins have been characterized, mostly in the families Fabaceae and Solanaceae. They are produced through the shikimic acid pathway and are often fungistatic rather than fungicidal. Important phytoalexins include pisatin, phaseollin, glyceollin and gossypol. In addition to their role in plant defense, many phytoalexins have potential health benefits for humans such as antioxidant, anti-inflammatory and anticancer properties.
Phytoalexins
- Phytoalexins are antimicrobial compounds produced by plants after exposure to microorganisms or abiotic stress. They are chemically diverse and fall into classes like terpenoids and alkaloids.
- The concept of phytoalexins was formalized in 1941 after observing that bean tissue produced inhibitory compounds when exposed to a fungal pathogen. Phytoalexins restrict pathogen growth at infection sites.
- Induction of phytoalexins involves MAP kinase signaling cascades and transcription factors like WRKY33 regulating genes in biosynthesis pathways. Camalexin production in Arabidopsis in response to pathogens depends on WRKY33 phosphorylation by MPK3/MPK6.
Role of enzyme in plant disease
This document summarizes the roles of enzymes, toxins, exopolysaccharides, and polypeptide signals in plant disease development. It discusses how enzymes secreted by pathogens break down plant cell walls and nutrients, allowing pathogens to utilize these resources. Different types of enzymes like hydrolases, hemicellulases, and proteolytic enzymes are described. Toxins directly act on and kill plant cells, causing disease symptoms. Exopolysaccharides protect bacterial biofilms and provide nutrients. Finally, the polypeptide signal systemin is discussed, which activates plant defense genes and functions long-distance within the plant in response to wounding or predator attacks.
Phytoalexins
Phytoalexins are broad-spectrum antimicrobial compounds produced by plants in response to pathogen infection. They are chemically diverse and fall into classes like terpenoids, steroids, and alkaloids. Phytoalexins are synthesized de novo from primary metabolites through pathways like the shikimic acid and mevalonic acid pathways after plants detect elicitors from pathogens. They function as toxins to disrupt the metabolism and reproduction of pathogens. Their production is part of plants' general short-term response to infection and their long-term systemic acquired resistance which protects the entire plant.
PR protein by kk sahu sir
This document discusses pathogenesis-related (PR) proteins found in plants. It begins with definitions, noting that PR proteins are produced when plants are infected by pathogens and act to decrease susceptibility. It then describes 17 types of PR proteins classified into families based on their properties, with examples like chitinase and glucanase. Mechanisms of action are discussed, such as degrading fungal cell walls. The document concludes by outlining applications for transferring PR protein genes to transgenic plants to engineer resistance against pathogens like fungi and bacteria.
Biosynthesis of auxin[1]
This document summarizes information about the plant growth hormone auxin. It defines auxin as chemical substances that promote stem or root growth. The first known auxin is indole-3-acetic acid. There are two types of auxin: natural auxins produced by plants like IAA, and synthetic auxins created in labs. The document then describes the three step biosynthesis process of IAA from the amino acid tryptophan. Finally, it lists several physiological effects of auxins, including cell elongation, promotion of cell division, root growth, apical dominance, prevention of abscission, formation of seedless fruits, and regulation of plant growth movements.
Credit seminar
Plants have array of defense response against biotic stresses which could be either structural reinforcement, release of chemicals, and defense gene expression against invading organisms. The physical barriers are trichoms, waxy cuticle, thick cell wall. Once the pathogen overcomes the first line of defense, basal or innate defense response comes into play. Pathogens secrete some conserved molecules known as Pathogen Associated Molecular Pattern (PAMP/MAMP), which are recognized by transmembrane receptors present in the plasma membrane and initiate a series of signal cascade reaction which ultimately leads to activation of various defense related genes. Apart from inducing the expression of defense related genes, it also triggers a hypersensitive reaction (HR) which cause deliberate cell death at the site of infection and limit the pathogen access to water and nutrient by sacrificing a few cells in order to save the rest of the plant. Once HR is triggered, plant tissue may become highly resistant to a broad range of pathogens for an extended period of time. This phenomenon is called Systemic Acquired Resistance (SAR).
Plants respond to herbivory is a similar manner as described above. The biochemical mechanisms of defense against the herbivores are wide-ranging, highly dynamic, and are mediated both by direct and indirect defenses. The defensive compounds are either produced constitutively or in response to plant damage, and affect feeding, growth, and survival of herbivores. In addition, plants also release volatile organic compounds that attract the natural enemies of the herbivores. These strategies either act independently or in conjunction with each other. However, our understanding of these defensive mechanisms is still limited. Induced resistance could be exploited as an important tool for the pest management to minimize the amounts of insecticides used for pest control. Host plant resistance to insects, particularly, induced resistance, can also be manipulated with the use of chemical elicitors of secondary metabolites, which confer resistance to insects. By understanding the mechanisms of induced resistance, we can predict the herbivores that are likely to be affected by inducing responses. The elicitors of induced responses can be sprayed on crop plants to build up the natural defense system against damage caused by herbivores. The induced responses can also be genetically engineered, so that the defensive compounds are constitutively produced in plants challenged by the herbivory. Induced resistance can be exploited for developing crop cultivars, which readily produce the inducible response upon mild infestation, and can act as one of components of integrated pest management for sustainable crop production.
Pr protein
Pathogenesis-related (PR) proteins are a diverse group of plant proteins that are produced in greater amounts when plants are infected by pathogens or exposed to stress. There are at least 14 families of PR proteins that differ in their functions, properties, and modes of action. Some key PR proteins include PR1, PR2, and PR3. PR1 proteins have antifungal properties and may disrupt fungal membranes. PR2 are β-1,3-glucanases that degrade fungal cell walls. PR3 are chitinases that break down chitin in fungal cell walls, weakening the walls and killing fungi.
Plant - Pathogen Interaction and Disease Development
Plant diseases are the result of infection by any living organisms that adversely affect the growth, development, physiological functioning and productivity of a plant, manifesting outwardly as visible symptoms.
Host pathogen interaction plants
plant pathogen interaction
different types of pathogens
gene for gene hypothesis
direct receptor model
Elicitor receptor model
suppersor repressor model
gaurd hypothesis
Phytoalexins
a detailed description of structural and biochemical mechanisms and importance of phytoalexins in plants and different types of phytoalexins produced the plants and its functions and importance in plant defense mechanism
Molecular basis of plant resistance and defense responses to pathogens
This document summarizes a study on the molecular mechanisms of plant defense responses to the tomato powdery mildew fungus Oidium neolycopersici. The study investigated three monogenic genes (Ol-1, ol-2, and Ol-4) that confer resistance to the fungus via different mechanisms. It found that reactive oxygen species and callose accumulation were associated with resistances from both dominant and recessive Ol genes. cDNA-AFLP profiling identified different expression classes of genes, with Class III genes specifically upregulated only during incompatible interactions. The study provides insights into the molecular interactions and defense signaling pathways involved in the plant-pathogen system.
Systemic acquired Resistance
The document discusses systemic acquired resistance (SAR), which confers long-lasting protection against a broad spectrum of pathogens. SAR is induced by initial infection and involves the signaling molecule salicylic acid, leading to accumulation of pathogenesis-related proteins throughout the plant. Key regulators of SAR include NPR1, which is required for SAR, and salicylic acid, which is involved in transmitting the defense signal systemically.
Role of Toxins in Plant Pathogenesis
This document discusses toxins produced by plant pathogens. It begins by classifying toxins into three categories: pathotoxins, phytotoxins, and vivotoxins. It then discusses specific toxins in more detail, distinguishing between host-specific toxins and non-host specific toxins. Examples of both types of toxins are provided, along with descriptions of their modes of action and effects on host tissues. Overall, the document reviews the role of toxins in plant disease development and pathogenesis.
Role of Plant toxin
Toxins produced by plant pathogens play an important role in disease development. There are three classes of toxins: pathotoxins which cause disease symptoms, phytotoxins which may contribute to disease, and vivotoxins which function in disease production but are not the initial cause. Toxins can be host-specific, affecting only the pathogen's host, or non-host specific. Host-specific toxins like T-toxin and victorin are primary determinants of disease in susceptible hosts by disrupting mitochondrial function or stimulating cell death. Non-host specific toxins like tabtoxin and tentoxin do not have host specificity and can affect plant physiology. Toxins cause effects like
Role of enzymes in pathogenesis
1. The document discusses plant pathogens and the enzymes they secrete to degrade plant cell walls and tissues. It describes the primary components of cuticles, cell walls, and middle lamella that pathogens target, including cutin, cellulose, pectin, hemicellulose, and lignin.
2. The key cell wall-degrading enzymes produced by pathogens are discussed, such as cutinases, pectinases, cellulases, hemicellulases, lignin-degrading enzymes, and proteases. Examples are given of pathogens and the roles of specific enzymes in disease development.
3. Effects of pathogens on physiological processes like photosynthesis, translocation of water and nutrients, respiration,
Biotechnological approches in disease management
This document discusses various biotechnological approaches for plant disease management, including tissue culture, recombinant DNA technology, and transgenic approaches. Tissue culture techniques like meristem culture can produce disease-free planting materials. Recombinant DNA technology allows generation of resistant plants by expressing genes conferring resistance to bacterial, fungal or viral diseases. Transgenic approaches discussed include pathogen-derived resistance utilizing viral coat protein or movement genes, as well as expressing plant disease resistance genes, ribosome-inactivating proteins, and genes involved in systemic acquired resistance.
PR Pathogenesis related proteins
Pathogenesis-related proteins (initially named “b” proteins) were discovered in tobacco leaves
hypersensitively reacting to TMV by two independently working groups (Van Loon and Van Kammen,
1970; Gianinazzi et al., 1970)
Hypersensitive Reaction in plant and their mechanism
Hypersensitivity and its Mechanism summarizes the hypersensitive response (HR) in plants. The HR is a localized cell death response at the site of infection that limits pathogen growth and provides resistance. It involves the recognition of pathogen elicitors by plant receptors, which activates a biochemical reaction cascade and the production of reactive oxygen species and defense compounds. This leads to cell death in infected areas and the acquisition of systemic resistance in other plant tissues through signaling molecules like salicylic acid, jasmonic acid, and ethylene. The HR occurs through specific host-pathogen combinations and results in the depolarization of membranes and disintegration of cellular components at the infection site.
Disease resistance in plants
Plant disease resistance occurs through both pre-formed structures and infection-induced immune responses. There are two tiers of the plant immune system - pattern-triggered immunity (PTI) triggered by pathogen-associated molecular patterns (PAMPs), and effector-triggered immunity (ETI) triggered by recognition of pathogen effectors through resistance (R) proteins. Quantitative resistance involving multiple genes provides more durable resistance than major gene resistance. Genetic engineering and breeding can enhance crop disease resistance through introduction of R genes or resistance mechanisms.
Transgenic plants with biotic stress resistance
This document discusses transgenic plants with resistance to biotic stress. It begins by defining biotic stress as damage caused by living organisms like bacteria, viruses, fungi and insects. Developing transgenic plants is presented as a way to improve crop yields by making plants resistant to these stresses. Specific examples of transgenic plants containing genes from Bacillus thuringiensis (Bt) that code for insecticidal proteins are described. Bt genes have been introduced into crops like corn, cotton and potatoes to resist pests like rootworms and Colorado potato beetles. While Bt crops have increased yields, there is a risk of pests developing resistance over time if not managed properly.
Systemic Acquired resistance
This document summarizes systemic acquired resistance (SAR) in plants. It discusses that SAR is a defense response activated by pathogens that results in long-lasting, broad-spectrum resistance in distant parts of the plant. The key points are:
- SAR involves accumulation of salicylic acid and pathogenesis-related proteins in distant, uninfected tissues which provides resistance against a wide range of pathogens.
- It is activated after an initial infection causes cell death and necrosis, and involves mobile signaling molecules like methyl salicylate that transmit the defense signal systemically.
- SAR protects against future infections by viruses, fungi, bacteria and activates genes that encode antimicrobial pathogenesis-related proteins.
Disease development: Role of enzymes, toxins and growth regulators.
Disease development: Role of enzymes, toxins and growth regulators.Assam University, Silchar, Assam, India
The document discusses the role of enzymes, toxins, and growth regulators in plant pathology and disease development. It defines plant pathology and describes how diseases develop through a complex process influenced by environmental factors and stress. The summary is:
1) Plant pathology studies plant diseases and their causes and controls. Disease develops through interactions between pathogens, hosts, and the environment.
2) Key stages of disease development include inoculation, penetration, infection, pathogen growth and reproduction, and dissemination. Disease occurs when conditions are suitable for the pathogen but not the host.
3) Factors like temperature, moisture, light, soil properties, and wind influence disease development by affecting the pathogen, host, or their interaction. UnderstandingPr protein(rakesh 2014 a42d)
This document discusses pathogenesis-related (PR) proteins in plants. It describes 17 families of PR proteins that are toxic to invading pathogens. While present at low levels in healthy plants, PR proteins are produced in much higher amounts when the plant is under pathogen attack or stress. The document outlines the different activities, targets, and functions of several PR protein families, including their roles in inhibiting pathogens through enzymatic activities, strengthening cell walls, or permeabilizing pathogen cell membranes. It concludes that PR proteins play an important role in plant disease resistance and stress response.
Epidemiology of plant diseases
The document discusses plant disease epidemics and epidemiology. It defines an epidemic as a disease that spreads rapidly to many individuals within an area over a short time period. Epidemiology is the study of epidemics and the factors that influence them, including the interaction between hosts, pathogens, environments, and human activities. For an epidemic to occur, there needs to be a susceptible host, a virulent pathogen, and favorable environmental conditions over an extended period of time. The interaction of these components can be visualized using a disease triangle or tetrahedron model. Examples of historical epidemics that caused famines are discussed.
Genetic engineering for nitrogen fixation and nutrient uptake
This document discusses genetic engineering strategies for improving nitrogen fixation and nutrient uptake in plants. It describes engineering symbiotic nitrogen fixation by optimizing colonization and carbon/nitrogen exchange between microsymbionts and plant cells. It also discusses improving phosphorus and nitrate uptake through modifying transporter genes and developing phosphite-based fertilization systems. Genome-wide association studies identified genes related to phosphorus efficiency in soybean, including one gene GmACP1 that explained 41% of phenotypic variation. Overall, the document outlines various genetic engineering approaches for enhancing nutrient acquisition in crops.
Organogenesis, in plant tissue culture
Introduction
Definition
Types of organogenesis
Organogenesis through callus formation (indirect organogenesis)
Growth regulators for indirect organogenesis
Organogenesis through adventitious organ (direct organogenesis)
Growth regulators for direct organogenesis
Factor affecting the soot bud differentiation
Organogenic differentiation
Application of organogenesis
Conclusion
References
Genetic engineering for flower colour modification
Genetic engineering provides a means to modify flower colour by manipulating genes in the flavonoid biosynthetic pathway. This document discusses how over-expressing or silencing genes related to flower pigment production can change colour. It also presents case studies of colour modification in plants like carnation and rose through genetic engineering techniques like Agrobacterium mediated transformation and particle bombardment. The goal is to generate novel colours and expand the options available to the floriculture industry.
Phytoalexins by sajad nabi
Phytoalexins are toxic compounds produced by plants in response to infection by pathogens or exposure to stresses. They help confer resistance against infecting parasites. The document discusses that phytoalexins are induced after infection and inhibit fungal growth. It provides examples of specific phytoalexins produced by different plants like pisatin in peas and gossypol in cotton in response to various fungi. The document also explains the role of phytoalexins in plant defense and resistance.
Phytoalexins ptt by AARIF
This document discusses phytoalexins, which are antimicrobial compounds produced by plants after exposure to microorganisms or other stresses. It defines phytoalexins, describes their mechanism of action in defending against pathogens, and outlines the major types that have been identified, including pisatin, phaseollin, and gossypol. The functions of phytoalexins are also summarized, noting that they act as toxins to attackers and help delay or disrupt pathogen growth and reproduction.
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Plant - Pathogen Interaction and Disease Development
Plant diseases are the result of infection by any living organisms that adversely affect the growth, development, physiological functioning and productivity of a plant, manifesting outwardly as visible symptoms.
Host pathogen interaction plants
plant pathogen interaction
different types of pathogens
gene for gene hypothesis
direct receptor model
Elicitor receptor model
suppersor repressor model
gaurd hypothesis
Phytoalexins
a detailed description of structural and biochemical mechanisms and importance of phytoalexins in plants and different types of phytoalexins produced the plants and its functions and importance in plant defense mechanism
Molecular basis of plant resistance and defense responses to pathogens
This document summarizes a study on the molecular mechanisms of plant defense responses to the tomato powdery mildew fungus Oidium neolycopersici. The study investigated three monogenic genes (Ol-1, ol-2, and Ol-4) that confer resistance to the fungus via different mechanisms. It found that reactive oxygen species and callose accumulation were associated with resistances from both dominant and recessive Ol genes. cDNA-AFLP profiling identified different expression classes of genes, with Class III genes specifically upregulated only during incompatible interactions. The study provides insights into the molecular interactions and defense signaling pathways involved in the plant-pathogen system.
Systemic acquired Resistance
The document discusses systemic acquired resistance (SAR), which confers long-lasting protection against a broad spectrum of pathogens. SAR is induced by initial infection and involves the signaling molecule salicylic acid, leading to accumulation of pathogenesis-related proteins throughout the plant. Key regulators of SAR include NPR1, which is required for SAR, and salicylic acid, which is involved in transmitting the defense signal systemically.
Role of Toxins in Plant Pathogenesis
This document discusses toxins produced by plant pathogens. It begins by classifying toxins into three categories: pathotoxins, phytotoxins, and vivotoxins. It then discusses specific toxins in more detail, distinguishing between host-specific toxins and non-host specific toxins. Examples of both types of toxins are provided, along with descriptions of their modes of action and effects on host tissues. Overall, the document reviews the role of toxins in plant disease development and pathogenesis.
Role of Plant toxin
Toxins produced by plant pathogens play an important role in disease development. There are three classes of toxins: pathotoxins which cause disease symptoms, phytotoxins which may contribute to disease, and vivotoxins which function in disease production but are not the initial cause. Toxins can be host-specific, affecting only the pathogen's host, or non-host specific. Host-specific toxins like T-toxin and victorin are primary determinants of disease in susceptible hosts by disrupting mitochondrial function or stimulating cell death. Non-host specific toxins like tabtoxin and tentoxin do not have host specificity and can affect plant physiology. Toxins cause effects like
Role of enzymes in pathogenesis
1. The document discusses plant pathogens and the enzymes they secrete to degrade plant cell walls and tissues. It describes the primary components of cuticles, cell walls, and middle lamella that pathogens target, including cutin, cellulose, pectin, hemicellulose, and lignin.
2. The key cell wall-degrading enzymes produced by pathogens are discussed, such as cutinases, pectinases, cellulases, hemicellulases, lignin-degrading enzymes, and proteases. Examples are given of pathogens and the roles of specific enzymes in disease development.
3. Effects of pathogens on physiological processes like photosynthesis, translocation of water and nutrients, respiration,
Biotechnological approches in disease management
This document discusses various biotechnological approaches for plant disease management, including tissue culture, recombinant DNA technology, and transgenic approaches. Tissue culture techniques like meristem culture can produce disease-free planting materials. Recombinant DNA technology allows generation of resistant plants by expressing genes conferring resistance to bacterial, fungal or viral diseases. Transgenic approaches discussed include pathogen-derived resistance utilizing viral coat protein or movement genes, as well as expressing plant disease resistance genes, ribosome-inactivating proteins, and genes involved in systemic acquired resistance.
PR Pathogenesis related proteins
Pathogenesis-related proteins (initially named “b” proteins) were discovered in tobacco leaves
hypersensitively reacting to TMV by two independently working groups (Van Loon and Van Kammen,
1970; Gianinazzi et al., 1970)
Hypersensitive Reaction in plant and their mechanism
Hypersensitivity and its Mechanism summarizes the hypersensitive response (HR) in plants. The HR is a localized cell death response at the site of infection that limits pathogen growth and provides resistance. It involves the recognition of pathogen elicitors by plant receptors, which activates a biochemical reaction cascade and the production of reactive oxygen species and defense compounds. This leads to cell death in infected areas and the acquisition of systemic resistance in other plant tissues through signaling molecules like salicylic acid, jasmonic acid, and ethylene. The HR occurs through specific host-pathogen combinations and results in the depolarization of membranes and disintegration of cellular components at the infection site.
Disease resistance in plants
Plant disease resistance occurs through both pre-formed structures and infection-induced immune responses. There are two tiers of the plant immune system - pattern-triggered immunity (PTI) triggered by pathogen-associated molecular patterns (PAMPs), and effector-triggered immunity (ETI) triggered by recognition of pathogen effectors through resistance (R) proteins. Quantitative resistance involving multiple genes provides more durable resistance than major gene resistance. Genetic engineering and breeding can enhance crop disease resistance through introduction of R genes or resistance mechanisms.
Transgenic plants with biotic stress resistance
This document discusses transgenic plants with resistance to biotic stress. It begins by defining biotic stress as damage caused by living organisms like bacteria, viruses, fungi and insects. Developing transgenic plants is presented as a way to improve crop yields by making plants resistant to these stresses. Specific examples of transgenic plants containing genes from Bacillus thuringiensis (Bt) that code for insecticidal proteins are described. Bt genes have been introduced into crops like corn, cotton and potatoes to resist pests like rootworms and Colorado potato beetles. While Bt crops have increased yields, there is a risk of pests developing resistance over time if not managed properly.
Systemic Acquired resistance
This document summarizes systemic acquired resistance (SAR) in plants. It discusses that SAR is a defense response activated by pathogens that results in long-lasting, broad-spectrum resistance in distant parts of the plant. The key points are:
- SAR involves accumulation of salicylic acid and pathogenesis-related proteins in distant, uninfected tissues which provides resistance against a wide range of pathogens.
- It is activated after an initial infection causes cell death and necrosis, and involves mobile signaling molecules like methyl salicylate that transmit the defense signal systemically.
- SAR protects against future infections by viruses, fungi, bacteria and activates genes that encode antimicrobial pathogenesis-related proteins.
Disease development: Role of enzymes, toxins and growth regulators.
Disease development: Role of enzymes, toxins and growth regulators.Assam University, Silchar, Assam, India
The document discusses the role of enzymes, toxins, and growth regulators in plant pathology and disease development. It defines plant pathology and describes how diseases develop through a complex process influenced by environmental factors and stress. The summary is:
1) Plant pathology studies plant diseases and their causes and controls. Disease develops through interactions between pathogens, hosts, and the environment.
2) Key stages of disease development include inoculation, penetration, infection, pathogen growth and reproduction, and dissemination. Disease occurs when conditions are suitable for the pathogen but not the host.
3) Factors like temperature, moisture, light, soil properties, and wind influence disease development by affecting the pathogen, host, or their interaction. UnderstandingPr protein(rakesh 2014 a42d)
This document discusses pathogenesis-related (PR) proteins in plants. It describes 17 families of PR proteins that are toxic to invading pathogens. While present at low levels in healthy plants, PR proteins are produced in much higher amounts when the plant is under pathogen attack or stress. The document outlines the different activities, targets, and functions of several PR protein families, including their roles in inhibiting pathogens through enzymatic activities, strengthening cell walls, or permeabilizing pathogen cell membranes. It concludes that PR proteins play an important role in plant disease resistance and stress response.
Epidemiology of plant diseases
The document discusses plant disease epidemics and epidemiology. It defines an epidemic as a disease that spreads rapidly to many individuals within an area over a short time period. Epidemiology is the study of epidemics and the factors that influence them, including the interaction between hosts, pathogens, environments, and human activities. For an epidemic to occur, there needs to be a susceptible host, a virulent pathogen, and favorable environmental conditions over an extended period of time. The interaction of these components can be visualized using a disease triangle or tetrahedron model. Examples of historical epidemics that caused famines are discussed.
Genetic engineering for nitrogen fixation and nutrient uptake
This document discusses genetic engineering strategies for improving nitrogen fixation and nutrient uptake in plants. It describes engineering symbiotic nitrogen fixation by optimizing colonization and carbon/nitrogen exchange between microsymbionts and plant cells. It also discusses improving phosphorus and nitrate uptake through modifying transporter genes and developing phosphite-based fertilization systems. Genome-wide association studies identified genes related to phosphorus efficiency in soybean, including one gene GmACP1 that explained 41% of phenotypic variation. Overall, the document outlines various genetic engineering approaches for enhancing nutrient acquisition in crops.
Organogenesis, in plant tissue culture
Introduction
Definition
Types of organogenesis
Organogenesis through callus formation (indirect organogenesis)
Growth regulators for indirect organogenesis
Organogenesis through adventitious organ (direct organogenesis)
Growth regulators for direct organogenesis
Factor affecting the soot bud differentiation
Organogenic differentiation
Application of organogenesis
Conclusion
References
Genetic engineering for flower colour modification
Genetic engineering provides a means to modify flower colour by manipulating genes in the flavonoid biosynthetic pathway. This document discusses how over-expressing or silencing genes related to flower pigment production can change colour. It also presents case studies of colour modification in plants like carnation and rose through genetic engineering techniques like Agrobacterium mediated transformation and particle bombardment. The goal is to generate novel colours and expand the options available to the floriculture industry.
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Disease development: Role of enzymes, toxins and growth regulators.
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Similar to Phytoalexins
Phytoalexins by sajad nabi
Phytoalexins are toxic compounds produced by plants in response to infection by pathogens or exposure to stresses. They help confer resistance against infecting parasites. The document discusses that phytoalexins are induced after infection and inhibit fungal growth. It provides examples of specific phytoalexins produced by different plants like pisatin in peas and gossypol in cotton in response to various fungi. The document also explains the role of phytoalexins in plant defense and resistance.
Phytoalexins ptt by AARIF
This document discusses phytoalexins, which are antimicrobial compounds produced by plants after exposure to microorganisms or other stresses. It defines phytoalexins, describes their mechanism of action in defending against pathogens, and outlines the major types that have been identified, including pisatin, phaseollin, and gossypol. The functions of phytoalexins are also summarized, noting that they act as toxins to attackers and help delay or disrupt pathogen growth and reproduction.
Phytoalexin
Phytoalexins are antimicrobial compounds produced by plants in response to pathogens like fungi and bacteria. Some key phytoalexins include ipomeamarone from sweet potato, pisatin from pea pods, phaseollin from bean pods, and glyceollin I from soybeans. Phytoalexins are synthesized after the plant recognizes molecules from the pathogen. They function to inhibit pathogen growth through mechanisms like disrupting cell membranes or inhibiting energy production. Their production is part of the plant's defense response and helps contribute to resistance against diseases.
phytoalexins.ppt
This document discusses phytoalexins, which are antimicrobial compounds produced by plants in response to pathogens like fungi, bacteria, or viruses. It defines two classes: phytoanticipins, which are constitutively present, and phytoalexins, which accumulate only after pathogen perception. Various classes of phytoalexins are described, including furans, phenanthrenes, phenolcarboxylic acids, sesquiterpenes, phenols, coumarins, and isocoumarins. Modes of action include disrupting membranes and inhibiting electron transport. Finally, it notes that phytoalexins may help control human diseases by ameliorating diabetes, ischemia, cancer, and pathogens through
Phytoalexin
Phytoalexin is a some of chemicals and it's derived from natrually in plants and it has antimicrobial property nature
Defence mechanism in plants
The document discusses the defence mechanisms in plants against pathogens. It describes both structural and biochemical defences. Structural defences provide physical barriers like cuticles, cell walls and induced structures. Biochemical defences include pre-existing compounds like phenols, enzymes and toxins. Post-infection, plants produce phytoalexins, hypersensitivity response and new proteins to inhibit pathogens. The defences have evolved through co-evolution with pathogens and help plants survive attacks.
ideal characters of antagonist.pptx
The document discusses biological control of plant diseases. It describes ideal characteristics of biocontrol agents including being non-pathogenic and having a broad spectrum of activity. Common biocontrol agents used are fungi, bacteria, and actinomycetes from the genera Trichoderma, Gliocladium, Pseudomonas, and Bacillus. Mechanisms of biocontrol include direct mechanisms like hyperparasitism and antibiosis, as well as indirect mechanisms like competition and inducing systemic resistance in plants.
Use of Pseudomonas fluoroscens as biocontrol agent
This document discusses the use of Pseudomonas fluorescens as a biocontrol agent. P. fluorescens is a common soil bacterium that acts as a biological control agent against various plant pathogens through multiple modes of action, including antibiotic production, siderophore production, induced systemic resistance, competition, and hydrogen cyanide production. It can also promote plant growth. The document provides details on the isolation, multiplication, and use of P. fluorescens as a biocontrol agent.
C006_ISHAN_SHAH_Biotic_stress.pptx
Biotic stress refers to stress caused by living organisms that damage plants, such as fungi, bacteria, insects, and weeds. Fungi cause more plant diseases than any other factor, with over 8,000 fungal species known to cause plant diseases. Plants have various defense mechanisms against biotic stress, including physical defenses like cell walls and waxy cuticles, and chemical defenses like terpenoids, phenolics, and nitrogen compounds that are toxic to pathogens and herbivores. Biotic stress can significantly impact plants and cause pre- and post-harvest losses if not properly managed.
Santhakumar phyllosphere
1) The phyllosphere refers to the above-ground parts of plants that serve as a habitat for microorganisms. This includes the leaf surface (phylloplane) and surrounding area.
2) Common microbes found in the phyllosphere include bacteria like Pseudomonas and fungi such as Aspergillus. They play important roles in nutrient cycling and plant health.
3) Understanding the microbial communities of leaves is significant for controlling plant diseases and foodborne illnesses transmitted by plants. Microbes in the phyllosphere can help ward off pathogens through mechanisms like inducing phytoalexins in plants.
final-171210063453.pptx
This document summarizes toxins produced by plant pathogens and their role in plant pathogenesis. It discusses various classifications of toxins, including pathotoxins, phytotoxins, and vivotoxins. Key points include:
- Pathotoxins play a major role in disease production and cause characteristic disease symptoms. Examples include victorin and T-toxin.
- Phytotoxins' role in disease is suspected but not established, and they cause few disease symptoms. Examples include alternaric acid and piricularin.
- Vivotoxins function in disease production but are not the initial cause; examples include fusaric acid.
The document also covers host-
Biochemical defence mechanism of plants
This document discusses biochemical defense mechanisms in plants. It describes pre-existing defenses like inhibitors released before pathogen penetration, lack of nutrients needed for pathogen growth, and absence of antigens shared by pathogen and host. Post-infection defenses are also summarized, including induced production of phenolic compounds and phytoalexins toxic to pathogens. The document explains how plants can produce substances to resist pathogen enzymes, detoxify pathogen toxins, and alter biochemistry to negatively impact pathogens through toxicity or hypersensitive responses.
Microbial control of plant pathogens
Trichoderma is a fungus used for microbial control of plant pathogens. It can control pathogens through several mechanisms including mycoparasitism, antibiotic production, competition for space and nutrients in the rhizosphere, and induction of resistance in plants. The exact mechanisms involved are complex and can vary depending on the microbial control agent, pathogen, plant, and environmental conditions. Microbial control likely results from multiple mechanisms acting together synergistically.
secondarymetabolitesoffungi-161110115626.pptx
Antibiotics are produced by fermentation. Any large-scale microbial process occurring with or without air is called Fermentation.
Role of microbial toxins in plant pathogenesis
This document discusses the role of microbial toxins in plant pathogenesis. It defines toxins as metabolites excreted or released by pathogens that damage host cells. Toxins are classified based on their source and specificity. Host-specific toxins only affect a pathogen's host, while non-host specific toxins can damage unrelated plants. Toxins disrupt cell permeability, metabolic processes, and growth regulation, injuring and killing host cells. They play an important role in disease development and symptom expression.
defencemechanism 1-converted.pptx
Plants have developed structural, chemical, and protein-based defenses against pathogens. Structural defenses include waxy coatings, thick cell walls, and pores designed to limit pathogen entry. Chemical defenses include pre-existing compounds like phenolics and induced responses like phytoalexins and hypersensitive response that are activated post-infection. Together, a plant's layered defenses work to detect, stop, and limit damage from invading pathogens.
Plant growth-promoting
This document discusses plant-growth promoting rhizobacteria (PGPR), which are bacteria that indirectly promote plant growth through mechanisms like biological control or by directly enhancing plant growth without the presence of pathogens. PGPR colonize the rhizosphere, the soil area around plant roots, and can increase plant growth through various processes like biofertilization by fixing atmospheric nitrogen or solubilizing phosphorus, stimulating root development, degrading pollutants in the rhizosphere (rhizoremediation), or controlling plant stress by regulating the plant hormone ethylene. PGPR can also indirectly promote plant growth through biological control of pathogens using mechanisms like antibiosis, inducing systemic resistance in plants, or competing with pathogens for nutrients and space
B.sc. agri sem ii agricultural microbiology unit 4 biopesticides
The document discusses plant growth promoting rhizobacteria (PGPR) and their mechanisms for promoting plant growth and providing disease resistance. Some key points:
1) PGPR colonize the rhizosphere and rhizoplane of plant roots in higher numbers than other soil regions. They can fix nitrogen, produce plant hormones, and positively influence plant growth and health.
2) Mechanisms of PGPR include producing compounds like phytohormones, organic acids, siderophores, fixing nitrogen, solubilizing phosphate, and antibiotics. They also compete with deleterious microbes and induce systemic resistance in plants.
3) PGPR provide disease resistance to plants through mechanisms like competition with pathogens, antibiotic production
Plant phenolic compounds
plant phenolic compounds are secondary metabolites. these secondary metabolites play a very important role in plants.
Role of toxins in pathogenesis
This document provides information on plant pathogen toxins. It discusses different types of toxins like exotoxins, endotoxins, pathotoxins, vivotoxins, and phytotoxins. It also describes host-specific toxins produced by fungi like victorin, T-toxin, and HC-toxin and their role in pathogenesis. Non-host specific toxins like tabtoxin and phseolotoxin are also discussed. The effects of toxins on host tissues and some examples of other fungal toxins are summarized.
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Phytoalexins
- 1. PHYTOALEXINS Greek word“phyto-plant”, “alexin-warding off compound” Toxin like substances whichare formedonly post infectionally (Muller & Boerger) Phytoalexins are lowmolecular weight toxic substancesproducedby plants in response toinfectionby parasites, physiochemical stresses and confer protectionagainst the infecting parasite. Term coinedby: Muller &Boerger (1940) Hundreds of Phytoalexins have beencharacterized, mostly widespreadin Fabaceae and Solanaceae families andless reportedinfamilies like poaceae and cucurbitaceae. Two hypotheses were put forwardtoexplainthe mechanismof the inductionof Phytoalexins: De novo synthesisof enzyme. Activationor activity control of enzymes already formed. Phytoalexins are fungistatic rather thanfungicidal They are chemically diverse , but large number of themare products of the shikimic acid pathway. Synthesis: Host plant surface+ water ↓ Diffusion of host nutrients Host lechates +Fungal spores ↓ Germination & growth of fungus Mycoantigen +viable host cells ↓ Stimulation of host metabolism Production of phytoalexin Luqman adilMscbotany 4th semester
- 2. PHYTOALEXINS Activatedonly whenhost cell come in contact withthe pathogen Developedonly after fungal infection. Basis of differentiationbetweenresistant &susceptible hostsis basedon speedof formation. Resistant state of the host is not inherited. The sensitivity of host cell which determinesthe speedof host reactiontoproduce phytoalexin, is specific andgenetically determined. (Cruickshank-1966 Silent features: Broad based anti-fungal compounds Not translocated&rarely persistent Stimulant has no role in determining the chemical nature of phytoalexin, characteristic of host plants. Microbial agent serves as maininducer innatural conditions Quantity producedmay be influencedby age of host, inoculum concentration, temperature etc. the inhibitory material is achemical substance & may be regardedas a product of necrobiosis of the host cell. Non specific inits toxicity. Types of Phytoalexinsin plants: Ipomoeamarone: Sesquiterpinoidinducedinsweet potatotissueinfectedwithblack rot fungus Ceratocystis fimbriata. Inhibitory effect onthe fungus evenat 0.1% concentrations. Luqman adilMsc botany 4thsemester
- 3. Pisatin: It is a phenolic ether having chromocoumarinring. Producedby the exposedendocarpof the detachedpeain response toinoculationwith many fungi or injury. Productionof pisatinby pea pods inoculatedwith Moniliafructicola. It is a weak antibiotic withbroad spectrumactivity Phaseollin: It is similar topisatinin chemistry andfunctionprducedby beans. It is fungicidal at highconcentrations andfungistatic at low concentrations against S.fructigena. A no. of compounds suchas phaseollidin, phaseollinisoflavanand kievitone whichare structurally similar to phaseollinhave beenidentified. Trifolirhizin: It is a glucoside whichhas beenisolatedfromthe roots of redcloves. Its structure indicates that it is chemically closely relatedtopisatin. It has the formula C16H12O5 Rishitin: Muller andBoerger (1940) werethe first toshowthat the potatotubers carying the gene R1 for late blight resistance respondedwheninoculated withavirulent race of P.infestans by producing a phytoalexinthat inhibitedthe development of avirulent race. It is a bicyclic non- sesquiterpine alcohol. Luqman adil Mscbotany 4th semester
- 4. Gossypol: It is an ether soluble phenol producedby cotton. It is alsoproducedin diseases like black spot of rose (Diplocarponrosa), leaf spot of wheat (Septoriatritici). Xanthotoxin: Isolatedfromparsniproot discs inoculatedwithC.fimbriataInoculation withother non pathogens resultedinproductionof xanthotoxin. Capsidiol: it is a sesquiterpene phytoalexinproducedinpepper fruits inoculated withfungi. Producedconcentrations are sufficient toinhibit thesefungi in vitro. Medicarpin: Alfalfa(Medicagosativa) inoculatedwithaseries of pathogens and non pathogens have beenstudied. The antifungal compound was isolatedand identifiedas Medicarpin Glyceollin: producedin soybeanplants infectedwiththe fungus Phytophthora megaspermaf.sp.glycinea. Inoculationof fungal races resultedinhigher concentrations inincompatible host cultivarsthanininoculations of fungal races on compatible cultivars. Luqman adil Mscbotany 4th semester