cutin suberin waxes
provide protection against pathogens already on the plant surface and help to reduce water loss.
composed of five carbon isoprene units, are toxins and feeding deterrents to many herbivores
pigment function as shields against harmful UV radiation and as attractants for pollinators and fruit dispersers.
plant defenses against insect herbivores involve the induction of various secondary metabolites and proteinaceous inhibitors of digestion through signaling pathways involving _____acid.
macromolecule, polymer consisting of many long chain fatty acids that are attached to each other by ester linkages
A multilayered secreted structure that coats the outer cell walls of the epidermis on the aerial parts of all herbaceous plants.
wax cutin cuticular
cuticle is composed of a top coating of ___, a thick middle layer containing ___ embedded in wax, and a lower layer formed of cutin, and wax blended with the cell wall substances pectin, cellulose and other carbohydrates (the ____ layer)
not macromolecules, complex mixtures of long-chain acyl lipids that are extremely hydrophobic.
many fungi penetrate directly through the plant surface by mechanical means - others produce ___, an enzyme that hydrolyzes cutin and thus facilitates entry into the plant
all ______ are derived from the union of five-carbon elements (aka C5 units) that have the branched carbon skeleton of isopentane
mevalonic acid is phosphorlyated, decarboxylated and dehydrated to yield IPP
IPP can also be formed from intermediates of glycolysis or the photosynthetic carbon reduction cycle via a seperate set of reactions called the MEP
certain terpenoids have well characterized function in plant growth/development - can be considered primary rather than secondary metabolites. This important plant hormone are diterpenes
monoterpene ester that occur in leaves and flowers of chrysanthemum species, show insectidicial activity
terpene derived side chains such as phytol side chain of _____ help anchor certain molecules in membranes.
group of plant steroids that have the same basic structure as insect molting hormones
glycosides (compounds containing an attached sugar) that taste bitter and are extremely toxic to higher animals. Have dramatic effect on heart muscle through their influence on Na+/K+ activated ATPases. Extracts from foxglove prescribed as heart medication.
-Have no generally recognized direct roles in primary metabolism
-May be restricted to distinct groups of plants
-May protect against enemies
-May serve as attractants
-May function in plant-plant or plant-microbe interactions
What are the possible roles of secondary metabolites?
-Can function as plant growth regulators
(gibberellins, abscisic acid)
-May serve to transport or anchor
macromolecules w/in cells
-Can be toxic or otherwise defend
(pyrethroids, resins, essential oils,
Can serve as signals of stress
Can become toxic in light (photoxicity)
Can inhibit metabolism of other plants
Are precursors to lignin synthesis
Can function as pigments (flavonoids)
Can defend against pathogens
(isoflavonoids) or herbivores (tannins)
Straight-chain alkanes: CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3
cutin, waxes, and suberin are composed of:
All plant parts exposed to the atmosphere are coated with layers of lipid material that reduce water loss and help block the entry of pathogenic fungi and bacteria. The principal types of coatings are _____, _____, and _____.
All plant parts exposed to the atmosphere are coated with layers of _____ material that reduce water loss and help block the entry of pathogenic fungi and bacteria. The principal types of coatings are cutin, suberin, and waxes
All plant parts exposed to the atmosphere are coated with layers of lipid material that reduce _____ loss and help block the entry of _____ and _____. The principal types of coatings are cutin, suberin, and waxes
_____ is found on most above ground parts; _____ is present on underground parts, woody stems, and healed wounds. _____ are associated with both cutin and suberin.
-above ground parts
-underground parts, woody stems, and healed wounds
-both cutin and suberin
Cutin is found on most _____; suberin is present on _____. Waxes are associated with _____.
-long-chain fatty acids
-end opposite the carboxylic acid function
Cutin is a macromolecule, a polymer consisting of many _____that are attached to one another by ester linkages, creating a rigid three-dimensional network. Cutin is formed from _____ and 18:1 fatty acids with hydroxyl or epoxide groups situated either in the _____ of the chain or at the _____.
Cutin is a macromolecule, a polymer consisting of many long-chain fatty acids that are attached to one another by _____ linkages, creating a rigid three-dimensional network. Cutin is formed from 16:0 and _____ fatty acids with _____ or _____ groups situated either in the middle of the chain or at the end opposite the carboxylic acid function
-cutin embedded in wax
-cutin and wax blended with the cell wall substances pectin, cellulose, and other carbohydrates
Cutin is a principal constituent of the cuticle, a multilayered _____ structure that coats the outer cell walls of the epidermis on the _____ parts of all herbaceous plants. The cuticle is composed of a top coating of _____, a thick middle layer containing _____ (the cuticle proper), and a lower layer formed of (the cuticular layer). It has been suggested that in addition to cutin, the cuticle may contain a second lipid polymer made up of _____, which has been named cutan.
Cutin is a principal constituent of the cuticle, a multilayered secreted structure that coats the outer cell walls of the _____ on the aerial parts of all herbaceous plants. The cuticle is composed of a top coating of wax, a thick middle layer containing cutin embedded in wax (the _____), and a lower layer formed of cutin and wax blended with the cell wall substances pectin, cellulose, and other carbohydrates (the _____). It has been suggested that in addition to cutin, the cuticle may contain a second lipid polymer made up of long-chain hydrocarbons, which has been named _____.
complex mixtures of long-chain acyl lipids that are extremely hydrophobic.
Waxes are not macromolecules, but rather.....
straight-chain alkanes and alcohols of 25 to 35 carbon atoms.
The most common components of waxes are.....
The wax that forms the outer coating of the cuticle often _____ in an intricate pattern of rods, tubes, or plates
The wax that forms the outer coating of the cuticle often crystallizes in an intricate pattern of rods, tubes, or plates. Certain patterns of these microstructures enhance _____ by increasing the roughness of the wax surface. This roughness prevents _____ from forming large contact areas with, and thus from adhering to, the already hydrophobic surface. Thus _____ form instantly on contact and carry away contaminating particles, cleansing the plant's surface. This phenomenon was first described for the leaves of the leguminous lotus Lotus japonicus and, for that reason, it is sometimes referred to as the "_____."
-roughness of the wax surface
-carry away contaminating particles, cleansing the plant's surface
The wax that forms the outer coating of the cuticle often crystallizes in an intricate pattern of rods, tubes, or plates Certain patterns of these microstructures enhance water repellency by increasing the _____. This _____ prevents water from forming large contact areas with and, thus from adhering to, the already hydrophobic surface. Thus water droplets form instantly on contact and _____.
dicarboxylic acids, more long-chain components, and a significant proportion of phenolic compounds as part of its structure.
Like cutin, suberin is formed from hydroxy or epoxy fatty acids joined by ester linkages. However, suberin differs from cutin in that it has.....
Like cutin, _____ is formed from hydroxy or epoxy fatty acids joined by ester linkages. However, _____ differs from cutin in that it has dicarboxylic acids, more long-chain components, and a significant proportion of phenolic compounds as part of its structure.
-epoxy fatty acids
Like cutin, suberin is formed from _____ or _____ joined by _____ linkages. However, suberin differs from cutin in that it has _____, more _____ components, and a significant proportion of _____ compounds as part of its structure.
-cork cells of the periderm
-damaged by disease or wounding
Suberin is a principal component of the outer cell walls of all underground organs and is associated with the _____, the tissue that forms the outer bark of stems and roots during secondary growth of woody plants. Suberin also forms at sites of leaf _____ and in areas _____.
-the outer bark of stems and roots during secondary growth of woody plants
Suberin is a principal component of the outer cell walls of all _____ organs and is associated with the cork cells of the periderm, the tissue that forms _____. Suberin also forms at sites of leaf abscission and in areas damaged by disease or wounding
Cutin, suberin, and their associated waxes form barriers between the plant and its environment that function to keep _____ in and _____ out.
The cuticle is very effective at limiting water loss from aerial parts of the plant, but it does not block _____ completely: Even with the _____ closed, some water is lost. The thickness of the cuticle varies with _____ conditions.
Plant species native to arid regions typically have ____ cuticles than do plants from moist habitats, but plants from moist habitats often develop _____ cuticles when grown under dry conditions. Similarly, sun leaves and shade leaves of the same canopy often show different cuticle _____.
Plant species native to _____ regions typically have thicker cuticles than do plants from moist habitats, but plants from _____ habitats often develop thick cuticles when grown under _____ conditions. Similarly, sun leaves and shade leaves of the same _____ often show different cuticle thicknesses.
The cuticle and suberized tissues are both important in excluding _____ and bacteria, although they do not appear to be as important in pathogen resistance as some other defenses, such as _____ production and the _____ response. Many _____ penetrate the plant surface directly by mechanical means. Others produce _____, an enzyme that hydrolyzes cutin and thus facilitates entry into the plant.
The _____ and _____ tissues are both important in excluding fungi and _____, although they do not appear to be as important in pathogen resistance as some other defenses, such as phytoalexin production and the hypersensitive response. Many fungi penetrate the plant surface directly by _____ means. Others produce cutinase, an enzyme that _____ and thus facilitates entry into the plant.
_____ is the aglycone (sugarless) triterpene portion of the naturally occurring _____, which contain one molecule of the rare sugar _____ and one molecule of _____. The yam Dioscorea contains _____—e.g., yamogenin—that are widely used as starting materials in the synthesis of progesterone-like compounds for birth control pills.
Digitoxigenin is the _____ (sugarless) _____ portion of the naturally occurring digitanides, which contain one molecule of the rare sugar D-digitoxose and one molecule of acetyldigitoxose. The yam Dioscorea contains saponins—e.g., yamogenin—that are widely used as starting materials in the synthesis of _____ compounds for birth control pills.
Plant _____ are biosynthesized by several different routes and, thus, constitute a heterogeneous group from a metabolic point of view. Two basic pathways are involved: the shikimic acid pathway and the malonic acid pathway.
the shikimic acid pathway and the malonic acid pathway.
Plant phenolics are biosynthesized by several different routes and thus constitute a heterogeneous group from a metabolic point of view. Two basic pathways are involved:
The _____ pathway, although an important source of phenolic secondary products in fungi and bacteria, is of less significance in higher plants.
carbohydrate precursors derived from the pentose phosphate pathway (D-erythrose-4-phosphate) and glycolysis (phosphoenolpyruvic acid).
In the shikimic acid pathway, the aromatic amino acids are synthesized from:
aromatic amino acids
The shikimic acid pathway converts simple carbohydrate precursors derived from glycolysis and the pentose phosphate pathway to the _____.
shikimic acid pathway
The _____ converts simple carbohydrate precursors derived from glycolysis and the pentose phosphate pathway to the aromatic amino acids.
The well-known, broad-spectrum herbicide _____ (available commercially as _____) kills plants by blocking a step in the shikimic acid pathway.
The shikimic acid pathway is present in _____, _____, and _____ but is not found in _____.
The _____ pathway is present in plants, fungi, and bacteria but is not found in animals.
phenylalanine, tyrosine, tryptophan
Animals have no way to synthesize the three aromatic amino acids—_____, _____, and _____—which are therefore essential nutrients in animal diets.
The _____ units that make up lignin are not linked in a simple, repeating way. The lignin of beech contains units derived from coniferyl alcohol, sinapyl alcohol, and para-coumaryl alcohol in the approximate ratio _____ and is typical of angiosperm lignin. _____ lignin contains relatively fewer sinapyl alcohol units.
The phenylpropanoid units that make up lignin are not linked in a simple, repeating way. The lignin of beech contains units derived from _____, _____, and _____ in the approximate ratio 100:70:7 and is typical of _____ lignin. Gymnosperm lignin contains relatively fewer sinapyl alcohol units.
The phenylpropanoid units that make up _____ are not linked in a simple, repeating way. The _____ of beech contains units derived from coniferyl alcohol, sinapyl alcohol, and para-coumaryl alcohol in the approximate ratio 100:70:7 and is typical of angiosperm lignin. Gymnosperm _____ contains relatively fewer sinapyl alcohol units.
Mechanical damage, recognition of insect elicitors, induction of direct defenses, "the cry for help"
_____, _____, _____, _____, and _____ are some of the major events associated with induced defense responses.
Mechanical damage, recognition of insect elicitors, induction of direct defenses, and "the cry for help"—the recruitment of parasites and predators of the attacking herbivore through the release of so-called volatile organic compounds (VOC)—are some of the major events associated with _____ responses. A central role in these processes is played by jasmonic acid (JA), a _____-acid-derived signaling compound common to most, if not all, plants.
-the recruitment of parasites and
predators of the attacking herbivore through the release of so-called volatile organic compounds (VOC)
-jasmonic acid (JA)
Mechanical damage, recognition of insect elicitors, induction of direct defenses, and "the cry for help"(____________) are some of the major events associated with induced defense responses. A central role in these processes is played by _____, a fatty-acid-derived signaling compound common to most, if not all, plants.
Plants make a variety of less widely distributed compounds such as morphine, caffeine, nicotine, menthol, and rubber. These compounds are the products of _____, which is the metabolism of chemicals that occurs irregularly or rarely among plants, and that have no known general metabolic role in plants.
Secondary metabolites or secondary compounds are compounds that are not _____ for normal growth and development, and are not made through _____ pathways common to all plants.
alkaloids, terpenoids, and phenolics.
Secondary compounds are grouped into classes based on similar structures, biosynthetic pathways, or the kinds of plants that make them. The largest such classes are:
Secondary compounds often occur in combination with one or more sugars. These combination molecules are known as _____. Usually the sugar is a glucose, galactose or rhamnose. But some plants have unique sugars.
ecological roles that govern interactions between plants and other organisms.
The most common roles for secondary compounds in plants are:
Many secondary compounds are brightly colored pigments like anthocyanin that color flowers _____ and _____. These attract _____ and fruit and seed _____.
Alkaloids generally include alkaline substances that have _____ as part of a ring structure.
More than 6500 _____ are known and are the largest class of secondary compounds. They are very common in certain plant families.
_____ often evaporate from plants and contribute to the haze we see on hot sunny days. They are _____ to make; they often take 2% of the carbon fixed in photosynthesis; carbon that could otherwise be used for sugars.
Compounds that contain a fully unsaturated six carbon ring linked to an oxygen are called _____.
Flavonoids are complex phenolics. They are often sold in health food stores as supplements to ____. The most commonly available flavonoid is _____ from buckwheat.
Mustard oil glycosides
_____ are nitrogen-sulfur containing compounds that occur in cabbage, broccoli, horseradish, watercress and other members of the mustard family (Brassicaceae). They give the group its characteristic taste and odor.
_____ occur in several families of plants, but are especially common in roses (Rosaceae) and peas (Fabaceae). They are sugar containing compounds that release cyanide gas when hydrolyzed.
Plants continuously defend themselves against attack from pathogens via:
macromolecule, a polymer consisting of
many long-chain fatty acids (16:0 and
18:1 fatty acids with OH)
Cutin is a Component of _____ and
increase _____; however, its thickness is not always correlated with _____.
Particular secondary metabolites are often found in only one
plant species or related groups, whereas primary
metabolites are found throughout the plant kingdom.
secondary metabolites Differ from primary metabolites in distributions in that:
-Protect from against herbivores or pathogens
-Attractants for pollinators and seed-dispersing animals
-Agents of plant-plant competition and plant-microbe symbiosis secondary
secondary metabolites have three ecological functions:
-Nitrogen-containing secondary products.
Three major groups of secondary metabolites:
-Largest class, diverse, generally
-derived from the union of fivecarbon
elements (C5 units)
-Hydroxyl functional group on an aromatic ring
-Heterogeneous group of nearly 10,000 individual compounds:
some soluble, some insoluble, some polymer
-Defense compounds against herbivores and pathogens
-Absorbing UV radiation
-Reducing the growth of nearby competing plants
Phenolic compounds have diverse functions:
Plant _____ are biosynthesized in
several different ways. The Shikimic acid pathway the _____ pathway. The Malonic acid pathway is the _____ pathway.
Phenolic biosynthesis from _____ is the most abundant sources of plant phenolic compounds.
(A) Caffeic acid and ferulic acid may be released into the soil and inhibit the growth of neighboring plants----allelopathy.
(B) Psoralen exhibits phototoxicity to insect herbivores after activation by UV-A.
(C) Salicylic acid is a plant growth regulation involved in systemic resistance to plant
Simple phenolic compounds play a great
diversity of roles in plants. Give three examples.
_____ acid and _____ acid may be released into the soil and inhibit the growth of neighboring plants, known as _____.
_____ acid is a plant growth regulation involved in systemic resistance to plant pathogens.
The second most abundant organic substance in plant, highly branched polymer of phenylpropanoid group.
Components of cell walls of various types of supporting and
conducting tissues: tracheids and vessel elements of the xylem.
-Physical toughness deters feeding by animals
-Chemical durability makes it indigestible to herbivores
-Lignification blocks the growth of pathogens and is a common response to infection or wounding
Protective functions of Lignin:
-Carotenoids: yellow, orange, and red terpenoids
-Flavonoids: wide range of color
There are two principle types of colored pigments of plants. Name them and the colors are they associated with
-An increase in the number of hydroxyl groups shifts absorption to a longer wavelength and gives a blue color.
-Replacement of a hydroxyl group with a methoxyl group shifts absorption to a slightly shorter
wavelength, resulting in a redder color.
The colors of anthocyanidins depend in part on the substituents attached to ring B. Explain and give an example.
Flavones and flavonols generally absorb light at shorter wavelengths than do anthocyanins.
Flavonoids may protect against damage by UV light. This is because:
insects such as bees
Flavones and flavonols generally absorb light at shorter wavelengths than do anthocyanins, so not visible by the human eyes, but by _____.
-Arabidopsis thaliana chalcone synthase mutant produces no flavonoids, become more sensitive
to UV-B radiation
-Mutant grows poorly under normal conditions but grow normally when shielding from UV light.
-These experiments indicate that Flavonoids protect cells from excessive UV-B radiation.
What is the evidence that Flavonoids may protect against damage by UV light?
Flavones and flavonols generally absorb light at shorter wavelengths than do
anthocyanins, so not visible by the human eyes, but by insects such as bees, which may use them as _____.
- Anti-estrogenic effect
*Sheep grazing on clover rich in isolfavonoids often suffer from infertility
*soflavnonoid ring system has 3D structure similar to that of steroid, allowing these substances to bind to estrogen receptor
-Phytoalexins, antimicrobial compounds synthesized in response to bacterial or fungal infection.
Isoflavonoids have several different biological activities, including:
block the formation of endothelin-1, a signaling molecule that makes
blood vessels constrict, thus reducing the risk of heart disease.
Tannins, the Polyphenols in red wine, have been shown to:
Tannins, the Polyphenols in red wine, have been shown to block the formation of _____, a signaling molecule that makes blood vessels constrict, thus reducing the risk of heart disease.
Hydrolyzable tannins are formed from _____ and _____. They are _____ than condensed tanins and hydrolyze easily.
-Nonprotein amino acids
Most nitrogen-containing secondary metabolites are biosynthesized from common amino acids:
Alkaloids are defenses against predators, especially mammals. So, alkaloids at lower doses are useful _____, but _____agents at high doses.
N-oxide is _____ in the digestive tracts of most herbivores to the toxic form, tertiary alkaloid. Tertiary alkaloid is _____ to the nontoxic form, N-oxide, by certain adapted herbivores.
Cyanogenic glycosides are not normally broken down in the intact plant. Glycoside and degradative enzymes are spatially separated in different cellular
compartments or in different tissues
deter feeding by insects or other herbivores; but some herbivores have adapted to feed on these plants and tolerate large doses of HCN.
Cyanogenic glycosides have protective functions:
HCN (hydrogen cyanide)
Cyanogenic glycosides deter feeding by insects or other herbivores, but some
herbivores have adapted to feed on these plants and tolerate large doses of _____.
Similar to cyanogenic glycosides, glucosinolates are not normally broken down in the intact plant. Efforts to develop varieties with low glucosinolate levels in _____ but high glucosinolate levels in _____ are under way in order to retain resistance to pests, but still provide a protein-rich seed residue for animal feedings.
Nonprotein amino acids are not incorporated into proteins. Instead, they are present in the _____ and act as protective substances.
-Canavanine: mistakenly incorporated in to proteins and result in a nonfunctional protein
after ingestion by herbivores.
-Plants that synthesize nonprotein amino acids are not susceptible to the toxicity of these compounds.
Nonprotein amino acids exert their toxicity in various ways:
-Often species-specific and may exist as stored or conjugated compounds
-Most secondary metabolites as defense are constitutive but some are also induced
Discuss constitutive defense responses in plants.
-Initiated only after actual damage occurs
-Require smaller investment of plant resources then constitutive mechanisms, but they must be activated quickly to be effective.
Discuss nduced defense responses.
*Such as aphids and whiteflies
*Little damage to the epidermis and mesophyll cells
-Cell content feeders
*Such as mites and thrips
*Piercing/sucking insects that cause an intermediate amount of
physical damage to plant cells
*Such as caterpillars, grasshoppers, and beetles
*Cause the most significant damage of the plants
There are three categories of insect herbivores. Name them and describe.
-After the insect ingests plant tissue containing these fatty acids, an enzyme in its gut conjugates the plantderived fatty acids to an insect-derived amino acid, resulting the fatty acid-amino acid conjugate.
-When plants recognize elicitors from insect saliva, a signal transduction network is activated to against
Discuss the concerted biosynthesis of elicitors from plant and insect precursors.
Insect-derived compounds that trigger signaling pathways systematically, in the wound response.
-Jasmonic acid (JA) is a plant hormone that activates many defense responses
*JA levels rise steeply in response to
insect herbivore damage.
*Trigger production of many proteins
involved in defense.
+Key enzymes in major pathways for secondary metabolites
*Arabidopsis mutants producing low
levels of JA are:
+easily killed by insect pests
+Application of exogenous JA restores
-Ethylene (ET), salicylic acid (SA),
Methyl-SA are also induced by insect
*For full activation of induced defense
Discuss the steps in the pathway for conversion of linolenic acid (18:3) to jasmonic acid -octadecanoid signaling pathway. Where do these reactions take place?
Ethylene (ET), salicylic acid (SA),
Jasmonic acid (JA) is a plant hormone that activates many defense responses. Levels rise steeply in response to _____ damage. _____, ____, and _____ are also induced for full activation.
*Block the action of starch-digesting enzyme
*Bind to carbohydrates or carbohydrate-containing proteins.
*Bind to the epithelial cells lining the digestive tract and interfere with nutrient absorption
*Block herbivore proteolytic enzymes
*Hinder protein digestion by binding tightly and specifically to the active site of proteinases of herbivores.
*Defensive roles demonstrated by transgenic tobacco expressing high levels of proteinase inhibitors—suffer less damage by insect herbivores.
Some Jasmonic acid (JA)-induced plant proteins inhibit herbivore digestion. Name the compounds involved with this and describe how each works.
Block the action of starch-digesting enzyme
Some JA-induced plant proteins inhibit herbivore digestion. What is the role of Alpha-amylase inhibitors?
-Bind to carbohydrates or carbohydrate-containing proteins.
-Bind to the epithelial cells lining the digestive tract and interfere with nutrient
Some JA-induced plant proteins inhibit herbivore digestion. What is the role of Lectins?
-Block herbivore proteolytic enzymes
-Hinder protein digestion by binding tightly and specifically to the active site of proteinases of herbivores.
-Defensive roles demonstrated by transgenic tobacco expressing high levels of proteinase inhibitors—suffer less damage by insect herbivores.
Some JA-induced plant proteins inhibit herbivore digestion. What is the role of Proteinase inhibitors?
-Wounded tomato leaves synthesize prosystemin, a large precursor protein.
-Prosystemin is proteolytically processed to produce the short polypeptide called systemin.
-Systemin is released from damaged cells into the apoplast.
-Systemin binds to its receptor on the plasma membrane.
-The activated receptor becomes phosphorylated and activates a phospholipase A2 (PLA2)
-PLA2 generate the signal that initiates JA biosynthesis.
-JA is transported through the phloem to systemic parts of the plants (?) by unknown mechanisms
-JA activates the expression of genes encoding proteinase inhibitors
Outline the steps in he proposed systemin signaling pathway in wounded tomato plants.
Reactive oxygen species (ROS): -H2O2 could be directly toxic to
pathogens, contribute to structural
reinforcement of plant cell wall,
either by crosslinking various
hydroxyproline and proline-rich
glycoproteins to the polysaccharide
matrix or by increasing the rate of
lignin polymer formation through
peroxidase, or acting as a signal.
protein secreted in response to PG: polygalacturonase, secreted
Describe the activation of plant defense response against pathogens.
-The rapid activation of defense reactions in association with host cell death
Hypersensitive response (HR)
the rapid accumulation of reactive oxygen species
(ROS) and nitric oxide (NO), both are required for the activation of HR.
Hypersensitive response (HR) is often preceded by:
-Strengthen the cell walls to increase resistance to microbial digestion
-Glucanase, chitinase are induced by fungal invasion
Many types of antipathogen defense are induced by infection:
Chemically diverse group of secondary metabolites with strong
antimicrobial activity that accumulate around the site of infection.
-Isoflavonoids in legumes such as alfalfa and soybean
-Sesquiterpenes in solanaceous plants such as potato, tomato, and tobacco
Common mechanisms, but different plant families employ different types of secondary metabolites as phytoalexins:
_____ is generally not detectable in the plants before infection, but rapidly
synthesized after microbial attack, usually regulated at transcriptional activation of genes in the biosynthesis pathways.
-Basal resistance or innate immunity
-Specific resistance (gene-for-gene theory)
Some plants recognize specific substances
released from pathogens. Two types:
Plant resistance proteins recognize effector activity and restore resistance through effector-triggered immune responses.
Specific resistance (gene-for-gene theory)
recognition of pathogen-associated molecular patterns (PAMP, such as bacterial flagellin) by extracellular receptor-like kinases (RLKs) promptly triggers basal immunity
Basal resistance or innate immunity
When a plant survives a challenge from a pathogen eliciting the formation of necrotic lesions, SAR can become established throughout the plant.
Systemic acquired resistance (SAR)
_____ is the primary pathway of translocation of the Systemic acquired resistance (SAR) signal.
-Infection of one leaf.
-Accumulation of salicylic acid induces transmission of signal to other parts of plant via vascular system, resulting in increased systemic resistance to pathogens.
-Synthesis and release of volatile methyl salicylate --> airborne transmission of signal to other parts of plant (and neighboring plants).
Describe how an initial pathogen infection may increase resistance to future pathogen attack.
-Toxicity and repellency to herbivores and microbes
-Mutants and genetic engineered plants have been employed to demonstrate their roles in defense.
Secondary metabolites with no apparent roles in growth and developments play roles to protect plants from predators and
-Constitutive defense: secondary metabolites such as terpenes, phenolics, nitrogen-containing compounds
*Production of signals: ROS, NO, SA, JA, ET
*Induction of signal transduction networks: kinase cascade, transcription factors, ect.
*Biosynthesis of phytoalexin, lignin, hydrolytic enzymes via signal transduction
-Basal resistance: recognition of PAMP
-Susceptibility: pathogen delivers effector proteins to suppress basal resistance
-Specific resistance: plant evolves R protein to recognize effector (Avr)
protein to trigger defense response
-Commercially as insecticides, fungicides, and pharmaceuticals
-Some are used as fragrances, flavorings, medicinal drugs, and industrial materials.
-Breeding or genetic engineering the plants producing higher or lower
Practical applications by studying secondary metabolites:
*Gibberellins, GA: diterpene
*Brassinoseteroids, BR: triterpene
*Abscisic acid, ABA: C15 terpene
-Sterols: triterpene derivatives
Some terpenes have roles in growth and development. Name the types of compounds involved in this and give examples.
The two well-known monoterpenes serve as defenses against insects and other organisms that feed on these plants:
Two triterpenes, _____ and ______ are powerful feeding deterrents to insects.
The first three enzymatic steps occurs in the chloroplast, resulting in 12-oxo-phytodienoic acid. This intermediate is then transported to the peroxisome.
Where do the reactions in the pathway for conversion of linolenic acid (18:3) to jasmonic acid take place?
Structure of the plant cuticle.
1. Surface wax
2. Cuticle proper
3. Cuticle layer
4. Cell wall
5. Middle lamella
6. Plasma membrane
8. Epidermal cell
What does this image represent?
Cuticle of a glandular cell.
2. Cuticular layer
3. Primary cell wall
4. Plasma membrane
What is this an image of?
Many types of antipathogen defense are induced by infection.
1. Elicitor (product of an avr gene)
2. Reactive oxygen species
3. Cell wall cross-linking
4. Receptor (R gene product)
5. Nitric Oxide (NO)
7. Hypersensitive response, phytoalexin biosynthesis, lignin biosynthesis, salicylic acid biosynthesis, biosynthesis of hydrolytic enzymes.
8. Systemic acquired resistance
What does this image represent?
Proposed systemin signaling pathway.
1. Local - signal generation: Wounded leaves synthesize prosystemin in phloem parenchyma cells, and the prosystemin is proteolytically processed to systemin. Systemin is released from the phloem parenchyma cells and binds to receptors on the plasma membrane of adjacent companion cells, activating a signaling cascade which results in the biosynthesis of jasmonic acid (JA).
2. Signal transport: JA is then transported via sieve elements, possibly in a conjugated form (JA-X), to unwounded leaves.
3. Systemic - signal recognition and response: In unwounded leaves, JA initiates a signaling pathway in target mesophyll cells, resulting in the activation of proteinase inhibitor genes. Plasmodesmata facilitate the spread of the signal at various steps in the pathway.
What does this image represent?
Label by describing what is going on in each step.