Plant Responses to the Environment Test 2

What is the typical organization of PRRs?

-An extracellular domain that interacts with the MAMP, within the domain there are leucine-rich repeats (LRRs) which provide an environment that favors the interaction of the extracellular domain with a MAMP -A transmembrane domain -An intracellular domain

Interactions between plants and biotic stressors--Species/population:

-Biotic stressors evolve strategies to bypass plant defense mechanisms (evolutionary adaptations) -Plants (& stressors) respond genetically to new challenges (ongoing 'evolutionary battle')

What triggers the opening of stomata?

-Blue light (prevalent at onset of dawn) -Low CO2 levels in leaf cavity -High humidity

Process of stomata closing:

-Ca2+ levels increase in cytosol -K+ and Cl- exit cytosol along electrochemical gradient -Water potential decreases in apoplast and adjacent cells -Water exits guard cells -Turgor decreases -Stomata close

What are the components of plant cell wall and cuticle that must be broken down?

-Cellulose -Hemicellulose -Proteins -Pectin (polygalacturonic acid) -Waxes (cutin) of cuticle

Fungal lytic enzymes

-Cutinases -Cellulases -Proteases -Polygalacturonase

Signals for closing of stomata:

-Darkness -High CO2 -Low humidity or water shortage -ABA signal (abscisic acid, a plant hormone)

Interactions between plants and biotic stressors--Individual plant:

-Diverse range of biotic stressors -Different stressors employ different mechanisms to exploit plant as a food source -Multiple plant defense strategies to resist or tolerate biotic stress

Carbon sequestration in oceans

-Fertilizing the ocean with iron leads to intense growth of phytoplankton--some of which sinks to bottom of ocean to form sediments --> long term carbon sequestration -Fertilizing ocean waters is highly controversial though --> algae in the phytoplankton release DMS which can prevent cloud formation

How can forestation be beneficial?

-Forests can sequester CO2. Through transpiration they increase water in atmosphere which can lead to cloud formation (which reflect sunlight and thus heat) -The use of wood products for construction and other durable goods has CO2 sink effect, if cut trees are replanted -Use of wood for non-durable products like paper or fuel does not produce additional CO2 like burning of fossil fuels, unless forests are destroyed and no reforestation takes place

What are the negative effects of forestation?

-Forests have low ability to reflect sunlight which counterbalances the reduced warming through sequestration

How do plants and fungi adhere to the saying "an eye for an eye"?

-Fungi produce lytic enzymes to destroy the cell wall of the plant -Plants produce lytic enzymes to destroy the cell wall of the fungus

Effects of increases in local temperatures on plants

-Heat --> heat stress (affects water balance) -Drought -Humidity of soil and air due to e.g. changes in rainfall, soil erosion, and flooding -Effects on transpiration rate and evaporative cooling (also due to CO2-induced closing of stomata)

Non-molecular defense strategies

-Ignore and outgrow -Acquire symbiotic partner that wards off attackers

Consequences of global climate change (besides higher surface temperatures in many regions of the world):

-Increased or decreased rain falls leading to more severe droughts, floods, and water availability -Sea levels are predicted to rise with consequences for coastal areas -In some regions, conditions will improve (for agriculture at least) -The most severe consequences are expected for countries that are already poor and unable to cope with climate-related events

Ways in which pathogens cause disease

-Necrotrophy -Biotrophy -Hemibiotrophy

Elaborate on membrane damage caused by UV-B/ROS

-Peroxidation of unsaturated fatty acids --> polyunsaturated fatty acids cause membrane perturbation --> membrane integrity destroyed -Damage to guard cell membranes --> stomata closure --> perturbation of gas exchange, less CO2 --> less carbon fixation --> reduced photosynthetic rate

Elaborate on damage affecting photosynthesis caused by UV-B/ROS

-Photosystem II: contains proteins very sensitive to ROS --> protein dysfunctional --> photosynthetic electron transport chain interrupted -Thylakoid membrane --> lipid peroxidation -Reduced expression of genes for chlorophyll binding proteins and other proteins that function in photosynthesis

Fundamental difference of plants to animals

-Plants are immobile, no change of place possible -Stress or no stress, there is no avoidance -The plant must be able to deal with the stress or die -Disease is often the exception (not terribly common)

Glycoprotein of Phytophthora sojae

-Protein functions as MAMP and induces defense response -Pep13 sequence is essential for enzyme activity -A functional trans-glutaminase appears to be essential for fungal survival

Ergosterol initiation of defense response:

-Steroidal lipid, similar to cholesterol, present in fungal spores and membranes of higher fungi -Elicitor that is characteristic for fungal pathogens and not present in the plant

Farmland: tilling v. no-till

-Tilling leads to exposure of plant debris and rapid decomposition into CO2 and H2O -No-tilling approaches to farming could prevents release of large amounts of CO2 from soils.

Lipopolysaccharides (LPS)

-bacterial MAMP -constitute major component of outer membrane of gram-negative bacteria -have a highly variable and highly conserved part -Conserved lipid A is as active in inducing plant defenses as the entire LPS

Characteristic features of bacteria

-bacterial flagella -bacterial cell wall components (e.g. lipopolysaccharides)

Characteristic features of fungi

-chitin and beta-glucan in cell wall -ergosterol in plasma membrane

Examples of alkaloids

-cocaine: nervous system stimulant -nicotine: induced response -caffeines: kills insects and slugs, inhibits phosphodiesterase -solanine: cholinesterase inhibitor which breaks down nerve signal acetylcholine -lupanine: toxic to grazing animals, live stock poisoning

Chitin oligomers

-linear polymer, major polysaccharide constituent of mycelial walls of fungi. -Not present in plants -Active fragments are released from fungal cell walls by the action of plant chitinases

Flagellin

-major structural protein in bacterial flagellum -conserved sequence of the protein is recognized by plant cells --> initiates defense response

Structural classes of MAMPs and DAMPs

-proteins -glycoproteins -lipids -oligosaccharides

Mechanical Defenses:

-thorns, spikes, spines -modified trichomes -primary resin system of conifers such as pines (toxic to insects) -epicuticular waxes on leaf surface/bark

Flavonoid examples

1) Anthocyanins: pigments (and antioxidants) 2) Condensed tannins: feeding deterrents, antifeedants 3) Hydrolysable tannins: 'plant defense' 4) Isoflavonoids: 'plant defense' e.g. rotenoids--used as insecticides, rat poison=rotenone 5) Coumarin: internal bleeding of live stock 6) Stiilbenes: Reveratrol has antitumor properties, present in red grapes and wine; likely role in plant defense

ROS are necessary for what important cellular functions?

1) Biosynthesis of cell wall (lignin) 2) Defense against pathogens 3) Signal transduction

Two effects of CO2

1) CO2 absorbed infrared radiation --> global warming 2) CO2 is substrate for photosynthesis which has effects on plant growth

Opening of stomata allows for what three things to occur?

1) CO2 enters the leaf 2) Water and oxygen leave the leaf 3) Water evaporation through stomata (transpiration) which drives stream that pulls water from roots to leaves--essential to bring water and nutrients to entire plant

Two different enzymatic activities of Rubisco:

1) Carboxylation: ribulose bisphosphate + CO2 --> 2 PGA 2) Oxygenation: reaction results in incorporation of oxygen rather than CO2 into ribulose bisphosphate. This is called photorespiration

Enzymatic antioxidant defense systems:

1) Catalase 2) Glutathione reductase 3) Ascorbate peroxidase 4) Superoxide dimutase

Antioxidant or scavenger enzymes

1) Catalase 2) Superoxide dismutase (SOD) 3) Ascorbate peroxidase (APX)

ROS are byproducts of what common cellular processes?

1) Certain redox reactions 2) Incomplete reduction of oxygen by the mitochondrial electron transfer chain 3) Oxidation of water by the chloroplast electron transfer chain 4) Beta oxidation pathway in peroxisomes

Why is UV-B/ROS harmful to plants?

1) DNA damage (RNA not relevant b/c not oxidative) 2) Membrane damage 3) Damage to proteins 4) Damage affecting photosynthesis 5) #1-4 result in an overall effect seen (e.g. morphogenetic effects: reduced growth and flowering, competitive balance, and reduced yield)

Different challenges inflicted by stressors:

1) Damage inflicted by wounding to all parts of plant (by herbivores) 2) Some parasitize the vascular system 3) Gall formation 4) Range from small wound sites to defoliation 5) Herbivore as Trojan horse for pathogens 6) Opportunistic pathogens infect through wound site

Consequences of heat stress:

1) Damage to proteins (denaturation, aggregation) 2) Damage to cellular structure (organelles, cytoskeleton) 3) Impairs membrane function 4) Decrease in non-stress-related proteins (e.g. in photosystems) 5) Increase in heat shock proteins (HSPs)

The production of chitinase and beta-glucanase has what three important consequences?

1) Degradation of fungal cell wall to stop growth of fungus 2) Release of oligomer MAMPs --> sensed by plant cells and induce same defense response as the oligogalcturonide DAMPs 3) Amplification of the defense response (positive feedback loop for the production of chitinase and beta-glucanase)

Two main antioxidant systems

1) Enzymatic 2) Non-enzymatic

Steps in the infection process of a fungal pathogen

1) Germination of the fungal spore 2) Hyphae have to penetrate the cuticle and then the cell wall of the plant cell

Non-enzymatic antioxidant systems

1) Glutathione 2) Ascorbate (vitamin C) 3) Beta-carotene (vitamin A) 4) Alpha-tocopherol (vitamin E) 5) Others (lycopene, resveratrol)

Damage and Disease--biotic stressors:

1) Herbivores (vertebrates, insects, mollusks) 2) Nematodes (worms) 3) Fungi 4) Oomycetes 5) Bacteria 6) Viruses

Acquired immunity:

1) Immunological recognition 2) Self/non-self discrimination ("training") 3) Immunological specificity (antibodies) 4) Immunological memory (certain T-cells)

How are ROS generated by UV-B?

1) Interaction of UV-radiation with biomolecules (absorption) which results in inappropriate electron transfer reactions, e.g. to O2 2) Consequence of perturbation of photosynthetic and respiratory electron flow; electrons transferred to O2 rather than a component of the ETC 3) Activity of an enzyme (plasma membrane NADPH oxidase; apoplastic peroxidase and others)

Constitutive Defenses:

1) Mechanical defense 2) Chemical defense 3) Others

Criteria for pathogen features that would be optimal to induce general plant resistance

1) Non-self 2) Not present in beneficial microorganisms such as Rhizobia and mycorrhizal fungi 3) Present in large taxonomic group 4) Small variation with a taxonomic group

Examples of DAMPs

1) Nucleotides -extracellular ATP -DNA 2) Sugars -sucrose -oligogalacturonic acid 3) Peptides -systemins -Peps

When does heat stress occur?

1) Overall hot temperatures 2) More severe if transpiration is limited when stomata are closed (why? --> evaporative cooling, like sweating in humans) 3) Germination in hot soil 4) Fruits (can not dissipate heat due to reduced transpiration)

Nature of UV-B stress

1) Oxidative 2) Production of reactive oxygen species (ROS)

Why is photorespiration reduced in C4-plants?

1) PEP carboxylase does not have an oxygenase activity 2) Release of CO2 from malate results in high CO2 concentrations --> favors carboxylation

Process of stomata opening:

1) PM H+ ATPase in guard cell activated --> pumps protons out of the cytosol into apoplast 2) Cytosol increasingly negative 3) K+ enters cytosol along electrochemical gradient and Cl- enters cell to balance K+ influx; this keeps cytosol negative which keeps K+ influx going 4) Solute potential in cytosol decrease, water potential decreases 5) Water potential in cytosol more negative than in apoplast 6) Water enters guard cells, turgor increases (pressure potential goes up) 7) Opening of stoma

Induced biosynthetic pathways for UV-absorbing sun screens

1) Phenylpropanoids, flavonoids 2) Naringenin represents basic flavonoid structure 3) Accumulate in epidermal cell laters 4) Arabidopsis tt mutants do not make CHS and CH1 --> increased sensitivity to UV-B 5) fah1 mutant, defective in sinapate ester synthesis, more sensitive than tt mutants

What are the strategies that plants employ to defend themselves against a broad spectrum of pathogens?

1) Present of numerous specific receptors that recognize specific features characteristic of particular pathogen species (roughly comparable to vertebrate acquired immunity) 2) Presence of receptors that recognize general features common to large taxonomic groups of pathogens (at the species level or above)--very efficient strategy

The advantage of CAM plants

1) Prevention of water loss 2) Concentration of CO2 in the chloroplast can increase to very high levels which favors carboxylation over oxygenation activity of Rubisco (reduces photorespiration)

Result of the interaction of different proteins in HSPs:

1) Proper protein folding (de novo protein synthesis) 2) Protein unfolding 3) Transport into organelles 4) Assembly of protein complexes

How do plants protect themselves against UV-B effects?

1) Repair DNA damage 2) Detoxify damaging ROS before they do harm 3) Preclude UV-B from reaching intracellular targets (DNA, proteins, lipids, etc.)

Two examples of bacteria that have altered the flagellin sequence:

1) Rhizobium meliloti --> plant does not kill because bacteria fixes nitrogen for the plant 2) Agrobacterium tumefaciens --> altered flagellin sequence can not be recognized by the plant

Consequences of stratospheric ozone depletion and concomitant UV-B increase at ground level?

1) Skin cancer is humans 2) Negative effects on terrestrial and aquatic plant life

UV-B can lead to the formation of:

1) Superoxide anion (O2-*) 2) Hydrogen peroxide (H2O2) 3) Hydroxyl radical (OH*) 4) Singlet oxygen (1O2) --> singlet oxygen: spins of electrons in molecular orbits altered; lowest excited state of the dioxygen molecule; very reactive)

Chemical Defense, classified according to structure and biosynthesis

1) Terpenoid compounds 2) Phenolics; phenyl propanoids 3) Alkaloids 4) Proteins 5) Glucosinolates

What two organizations established the IPCC?

1) United Nations Environmental Program (UNEP) 2) World Meteorological Organization (WMO)

Why are toxic compounds not harmful to the plants?

1) compounds may not have plant targets 2) strategies to avoid toxicity -inactive precursors and activating enzymes are stored in separate compartments or cell types -deposition in vacuole -deposition in extracellular sites

Why do plants stay alive when infected with biotrophic pathogens?

1) e.g. pathogenic fungi: haustorium formation, invagination of plant plasma membrane, facilitates nutrient transport form plant membrane to haustroial membrane 2) Growth outside the plant cell wall in the apoplast; subsists on nutrients leaked out of the cytoplasm

Short answers. What are the three general strategies that plants employ to protect themselves against the harmful effects of UV-B? (Give simple answer, one or a few words, don't use extra space!)

1. Flavonoids --> UV-B sunscreen 2. Antioxidants for ROS 3. DNA repair

IPCC states: Globally, the potential for food production is projected to increase with increases in local average temperature over a range of ___ to ___ degree C, but above this it is projected to _________

1; 3; decrease

Fill in the blank. A 1% decrease in the ozone layer will cause an estimated ___% increase in UV-B irradiation at ground level.

2

UV-B is defined as electromagnetic radiation with a wavelength range of:

280-320 nm

Ultraviolet B (UV-B) light wavelengths

280-320 nm

Catalase reaction

2H2O2 --> O2 + 2H2O

The net energy requirement per fixed CO2 is:

3 ATP and 2 NADPH

Energy requirement per fixed CO2 in C3-plants:

3 ATP and 2 NADPH, but high losses due to photorespiration at high temperatures

Ultraviolet A (UV-A) light wavelengths

320-390 nm

Visible light wavelengths

390-700 nm

Light relevant for photosynthesis is photosynthetically active radiation (PAR) which is what wavelength range?

400-700 nm

Energy requirement per fixed CO2 in C4-plants:

5 ATP and 2 NADPH, more costly, but strongly reduced photorespiration

In some cases, up to ____% of CO2 fixation is lost due to photorespiration

50

Planck's constant

6.6 x 10^-34 J s

Elicitors that induce 'general' defense responses are called...

A general elicitors or microbe-associated molecular pattern (MAMP) or pathogen-associated molecular pattern (PAMP)

MAMPs convey the presence of what to a plant cell?

A potential pathogen

The intracellular domain is often what?

A protein kinase, an enzyme that transfers phosphate groups onto substrate proteins

What is tomatine?

A saponin in tomato that functions as a defense compound against a fungal pathogen. A particular fungal pathogen species carries an enzyme that inactivated tomatine--breakdown makes tomatine inactivce against pathogen, but also suppresses other plant defense responses

The recognition process of the 'damaged-self' does what two things?

A) Signaling that an infection is occurring B) Inducing a counter attack, a defense response, by the plant

The oxygenase function of Rubisco does not only result in no net carbon fixation, but also in a waste of _____ and _____

ATP and NADPH

Why is the acacia/ant example important?

Acacia completely depends on the ant defense and the ants depend on acacia for food supply

Cocaine, nicotine, and caffeine belong to the

Alkaloids

For an accurate global temperature prediction, we must include _____________ causes

Anthropogenic

Check the molecule that is NOT an antioxidant: -Ascorbate (vitamin C) -Glutathione (GSH) -Alpha-tocopherol (vitamin E) -Carotenoids (provitamin A) -Avenacin

Avenacin

Ultraviolet C (UV-C) light wavelengths

Below 280

Penetration of plant cell wall requires what?

Breakdown of the components of plant cell wall and cuticle

Molecular defense strategies

Broadly effective strategies against pathogens = general resistance Almost all genotypes of a plant species are resistant against most strains of a microbial species or larger taxonomic microbe group

Terpenoids

Build up from isoprene subunits C5 = isoprene C10 = monoterpene C15 = sesquiterpene C20 = diterpene C30 = triterpene Saponins: glycosylated triterpenoid from oat that defends against specific pathogen

There is almost unanimous scientific consensus that increasing anthropogenic _____ and other greenhouse gas concentrations lead to increased global temperatures

CO2

The first CO2 fixing step for C4-plants

CO2 (in the form of bicarbonate) is fixed by phosphoenolpyruvate (PEP) carboxylase to produce a 4-carbon organic acid called oxaloacetate

Short answer. What are the two most important anthropogenic green house gases causing global climate change? (water vapor excluded)

CO2 and Methane

Short answer. What are the two different substrates of Ribulose bisphosphate carboxylase/oxygenase (Rubisco)?

CO2 and O2

Thawing of the tundra's permafrost releases _______ and ________

CO2; methane

How can a global temperature increase affect light availability?

Changes in cloud coverage

MAMP-PRR interaction results in what?

Changes in the conformation of the transmembrane domain, a process through which the extracellular MAMP signal is 'transduced' to the intracellular domain inside the cell

A MAMP from fungal cell walls is:

Chitin

Plants use the following enzyme to break down the cell wall of fungal attackers

Chitinase

One of the responses to oligogalacturonide DAMPs is the production of ________________ and _______________

Chitinase; Beta-glucanase

Anthropogenic depletion of stratospheric ozone layer occurs when _____ move to the atmosphere and absorb UV radiation

Chlorofluorocarbons (CFCs), a chlorine atom is released which destroys ozone

There are enormous amounts of fixed carbon in the form of _____, ______, and _____ which are all carbon ______

Coal, oil, and natural gas; sinks

Definition. Tolerance

Compensate for damage -Plants can survive disease or herbivory without putting up defenses, e.g. via increased photosynthetic rate, regrowth, resource allocation --> fitness penalty, but completion of life cycle

Essential oils

Complex mixture of terpenoid defense compounds. Many are acutely toxic to insects and pathogens

Plant defenses can be __________ or ___________

Constitutive (preformed, present all the time); Induced (only present in response to stress)

HSPs help plants do what?

Cope with adjusting to heat stress (acclimation)

What does the Kyoto protocol of 1997 state?

Countries that engage in reforestation or plant large numbers of trees are allowed to burn more fossil fuels

The growth reduction is actually due harmful UV-B effects, this would not be desirable for _________________

Crop plants

The oligogalacturonides are not present in unattacked plants, there they function as ______

DAMPs

UV-B radiation leads to formation of ROS via damage to...

DNA, lipids, proteins, and via enzymes such as NADPH oxidase

A different type of general elicitor is a:

Damage-associated molecular pattern (DAMP)

Short answer. Oligogalacturonides are breakdown products of pectin (polygalacturonic acid) which is a major compound of plant cell walls. Therefore, oligogalacturonides do not qualify as MAMPs. What is the proper term for them (full term and acronym)?

Damage-associated molecule pattern (daMP)

________ genes are present inside the nucleus, making signal transduction from the outside to the inside of the cell very important

Defense

Phenolics

Derived from tyrosine or phenylalanine

PRRs feature different functional __________

Domains (sequence of amino acids that functions in a specific way, e.g. in binding to MAMPs)

Characteristic features of viruses

Double stranded RNA

Which anthropogenic chemicals contribute strongly to the depletion of the stratospheric ozone layer (ozone hole)? A) Methane B) Carbon dioxide C) ROS D) Sinapate esters E) Chlorofluorocarbons

E) Chlorofluorocarbons

A plant can recognize the oligogalcturonides as _______ that signal the presence of an attacker, even though they are technically "self"

Elicitor

Short answer. Compounds that induce defense responses (immunity/resistance) in plants are called:

Elicitors

What are the inducing agents of general resistance?

Elicitors

Definition. Infection

Entrance and subsequent multiplication of a microorganism in a plant

True or False. An infection of a plant by a pathogen always leads to disease

False

True or False. Plants and vertebrates both have acquired and innate immunity

False

True or False. The same molecular weapons cannot be employed during general and host-specific defenses

False

True or False. Tobacco plants sequester nicotine in special cells in order to avoid that nicotine harming the plants

False

True or False. A function of alkaloids is UV-B absorption, making alkaloids effective sunscreen compounds that prevent UV-B radiation from reaching cellular targets in plant cells.

False, A function of flavonoids is UV-B absorption, making flavonoids effect sunscreen compounds.

True or False. Ozone can readily enter the cell by passing the cuticle

False, CO2 can readily enter the cell by passing the cuticle

True or False. Ozone helps plants to cope with UV-B radiation by absorbing the radiation in plant cells and turning it to harmless oxygen

False, antioxidants help plants to cope with UV-B radiation

True or False. The Calvin Cycle is a metabolic pathway that generates ATP

False, it generates G3P

True or False. Extracellular ATP functions as an inducer of plant defenses. Therefore it is a MAMP

False, it is a DAMP

True or False. Under general resistance, all plants are resistant to all pathogens

False, some pathogens are able to overcome plant defense mechanisms and cause disease

True or False. All UV-B radiation is absorbed by ozone and none reaches the Earth's surface

False, some reaches the surface --> plants must develop protective mechanisms against harmful UV-B

True or False. The greenhouse effect is caused by greenhouse gases in the Earth's atmosphere that reflect UV-B radiation back to Earth.

False, the greenhouse gas effect is caused by greenhouse gases in the Earth's atmosphere that reflect INFRARED radiation back to Earth

True or False. When glutathione reacts with an ROS, the thiol group of glutathione becomes reduced

False, the thiol group becomes oxidized

True or False. HSPs form a large gene family with 4 subfamilies and are only present in plants.

False, there are 5 subfamilies and HSPs are present in all organisms (eukaryotes and prokaryotes)

True or False. The most important greenhouse gas is CO2

False. The most important GHG is water vapor (but not expected to contribute much to global warming)

An example for a peptide MAMP is:

Flaggellin

Short answer. Give an example for a MAMP common to all motile bacteria?

Flaggellin

Plants and crop plants will be largely effected by global warming and this could lead to a ______________

Food shortage (the extent depends on the degree of warming)

Definition. Pathogen

Fungus, oomycete, bacterium, nematode, or virus that causes disease

Glutathione reductase reaction

GSSG + NADPH --> 2GSH + NADP+

Ascorbate peroxidase reaction

H2O2 + ascorbate --> H2O + monodehydro-ascorbate radial

Acclimation is associated with the upregulation of ________ genes

HSP

Among the genes upregulated in heat shock, the _______ are the dominant group of genes

HSPs

Generally UV-B effects are considered to be ______ in humans

Harmfull (erythema, skin cancer, damage to eyes)

Why is it called the "greenhouse effect"?

Heat is absorbed by CO2 thereby contributing to atmospheric warming which in turn leads to warming of the surface of the Earth including the oceans

Short answer. The most important group of proteins that are strongly induced by heat stress are called:

Heat shock proteins (HSP)

Bonus question. The world just came together and ratified an agreement that curtailed the use of coolants that are very powerful greenhouse gases (although they don't destroy the ozone layer in the stratosphere). Those coolants are:

Hydrofluorocarbons

What is the common name for this ROS: H-O-O-H

Hydrogen Peroxide (H2O2)

Symbiosis (bull's horn acacia and Pseudomyrmex example)

In Central America. Acacia: -thorn at base of leaf provides home for ants -sugar from nectaries and fat/proteins from B.bodies provide ants with nutrients Ants: -bite and sting animals of all sizes -girdle branches of neighboring trees that compete for light with acacia -travel down trunk to destroy seedlings in surroundings of acacia

In an unstressed state, ATP exists only _________ of cells

Inside

When ATP is in the extracellular space, how is it perceived by the plant?

Intact neighboring cells can perceive ATP via a membrane-bound receptor

What does IPCC stand for?

Intergovernmental Panel of Climate Change

A toxic breakdown product of glucosinolates is called

Isothiocyanate

What happens to the oxaloacetate formed by C4-plants?

It is converted to malate which is then transported into the bundle sheath cells. Next step: release of CO2 from malate and a second fixation of CO2 by Rubisco in the Calvin Cycle

How does ozone enter plant cells?

It is polar and hydrophilic so it can not penetrate cell membranes or the cuticle. It enters through the stomata

UV-B effects on plants

It was found that exposing plants such as impatiens, tomatoes, and cucumbers to UV-B treatments for a few house slows their foliar growth and stem length without reducing color or other favorable characteristics

What happens when fossil fuels are burned?

Large amounts of carbons re-enter the carbon cycle

What is the function of stomata in leaves?

Let CO2 in and water & oxygen out

A MAMP from bacterial cell walls is:

Lipopolysaccharide

Definition. Parasite

Live in, with, or another organism and causes harm; generally eukaryotes

The signaling steps following the activation of the kinase substrate further relay and amplify the _____ signal

MAMP

Plants have a sophisticated surveillance system with a range of different ________________ proteins on the cell surface

MAMP receptor

Short answer. MTI is a defense response induced by MAMPs. MTI stands for:

MAMP-triggered immunity

Chitin, ergosterol, and pep13 are all 'non-self' from a plants perspective. Therefore they are examples of...

MAMPs

The chitin and beta-glucan oligomers are _____ and are recognized by plant PRRs

MAMPs

Examples of C4-plants:

Maize, sugarcane, many tropical grasses, and some dicots

Short answer. MAMP stands for:

Microbe-associated molecular pattern

NADPH oxidase reaction:

NADPH + O2 --> O2- (superoxide anion) + NADP+ + H+

Can we alter/substitute elicitors?

No, we can hypothesize that they are very important for the pathogens

Antioxidants

Non-enzymatic: 1) Ascorbate (vitamin C) 2) Glutathione (GSH) 3) Polyamines 4) Alpha-tocopherol (vitamin E) 5) Carotenoids (provitamin A) 6) Anthocyanins

Structure of Glutathione

Note: the thiol group of cysteine can be reversibly oxidized

Chemical reaction that produces ozone (caused by humans)

O2 + fossil fuels/CO/NO/NO2/SOx + light --> O3

Superoxide dismutase reaction

O2-* --> O2 + H2O2

A plant senses a fungus infection by the presence of ______________

Oligogalacturonides (DAMP)

What are the breakdown products of PGA?

Oligomers called oligogalacturonides Help: Polygalacturonic acid --> oligogalacturonides

Definition. Disease

Outcome of successful infection, if infection resulted in serious damage/death of plant

Two GSH can be oxidized to generate...

Oxidized glutathione (GSSG) by forming a disulfide bond between the thiol groups of two glutathiones GSH + GSH + ROS --> GSSG + e.g. O2 or H2O

Which enzyme is favored at higher temperatures? Carboxylase or oxygenase.

Oxygenase --> overall poor carbon fixation at high temperatures

Host-specific resistance

Particular plant genotype of a species is resistant against particular strain of pathogen species because of a specific resistance gene

Elaborate on damage to proteins caused by UV-B/ROS

Particularly in photosystem II --> proteins cross-linked or oxidized --> dysfunctional

What other stresses can result in the release of ATP from cells?

Pathogen elicitor (MAMPs) and abiotic forms of stress

The Bull's Horn Acacia protects itself against its enemies by recruiting a symbiont ant. Among the following plant enemies, the ants do NOT protect against:

Pathogens

What is another name for a MAMP receptor?

Pattern recognition receptor (PRR)

With just one receptor for ____, a plant can recognize all oomycete pathogens

Pep13

Alkaloids

Pharmacologically active, N-containing basic (some neutral) compounds of plant origin, structurally very diverse Most have antibiotic properties and are toxic to animals or act as feeding deterrents

CAM and C4-plants pursue a different strategy for fixing of carbon dioxide as compared to C3-plants. What enzyme do they (CAM and C4 plants) employ for the first CO2 fixation step?

Phosphoenolpyruvate carboxylase

The products of the Rubisco oxygenase reaction, _____________ and ______________ can be recycled back into the Calvin Cycle with the investment of ATP

Phosphoglycolate and PGA

UV-B-induced Cyclobutan pyrimidine dimers can be repaired by an enzyme called:

Photolyase

The process through which C3-plants lose energy by fixing O2 instead of CO2 is called

Photorespiration

3 billion years ago, the evolution of _____________________ resulted in increasing oxygen concentrations in the oceans

Photosynthetic marine cyanobacteria

Where are glucosinolates and myrosinase kept before herbivore attack?

Physically separated in different, but adjacent cells or subcellular compartments--mixed upon tissue damage

Necrotrophy

Plant cells are killed by toxins or cell wall degrading enzymes

Hemibiotrophy

Plant cells initially alive but killed later on

Biotrophy

Plant cells remain alive

Fungal pathogens use the following enzyme to break down the pectin in the plant cell wall

Polygalacturonase

What do plants possess to further the breakdown of their cell wall?

Polygalacturonase inhibiting proteins (PGIPs) in their cell walls which inhibit the polygalacturonase enzyme --> stops cell wall degradation. Also, leads to production of highly active oligogalacturonide elicitors with an optimal degree of polymerization

What does fungal polygalacturonase degrade?

Polygalacturonic acid (PGA)--a long cell wall polysaccharide

Glucosinolates

Preformed glucosinolates (not toxic) + myrosinase (released by herbivore attack) --> unstable aglycon + glucose The unstable aglycon disintegrates into biotoxic break-down products

Hallmarks of the fungal cell wall are what?

Presence of chitin and beta-glucan (neither are present in the cell wall of plants)

Definition. Resistance

Prevent damage --> reduction of herbivore/pathogen survival --> reduction of reproduction of stressor --> reduction of preference for a plant

In a study it was found that normal amounts of UV-B exposure had modest effects on growth rates, but...

Profound effects on nutrient cycling, soil processes, and decomposition

Defense proteins

Proteinase inhibitors interfere with proteolytic enzymes in guts of insects

When a membrane loses its integrity, ozone is able to pass through and cause damage to what?

Proteins, DNA, thylakoid and mitochondrial membrane (solutes and ions can leak in and out of the cell as well --> destroys the electrochemical gradient)

Generalized reaction for the detoxification of ROS:

ROS (oxidized) + antioxidant --> neutral reduced compound (e.g. H2O or O2) + oxidized antioxidant

Climate models that predict future climate are based on:

Recorded climate data

The cost of C4-plant strategy?

Recycling of PEP requires ATP

Glutathione reductase recycles what?

Reduced GSH

What does GSH stand for?

Reduced glutathione

These particular anthropogenic chemicals (CFCs) contribute to the ozone hole because they:

Release chlorine (Cl) that reacts with ozone to produce oxygen in the stratosphere

In humans, ozone can cause _________________

Respiratory diseases

Enzyme that reacts with CO2 and ribulose 1,5-bisphosphate (5 carbons) to produce two 3-phosphoglycerates (PGA)

Ribulose bisphosphate carboxylase/oxygenase (Rubisco)

ROSs function as...

Signal transducers that relay the UV-B signal by activating other signal transducers such as kinases

Which make better sunscreens: sinapate esters or flavonoids?

Sinapate esters

Problem for stomata when it is hot or dry:

Stomata close to prevent water loss, but then they can not photosynthesize efficiently because there is no CO2 being brought into the plant for fixation. Leads to reduced growth and yield.

The compound shown to the right (Myrcene) belongs to

Terpenoids

The IPCC Reports are generated by:

The Intergovernmental Panel on Climate Change

Phenolics/phenylpropanoids

The basic structure of phenolics is the phenyl ring plus three carbons in a row Examples: lignins, lignans, suberin, flavonoids

What is the main source of increasing CO2 concentrations?

The burning of fossil fuels

The NADPH oxidase reaction is followed by:

The dismutation of superoxide anion to hydrogen peroxide: O2- + 2H2O --> 2H2O2

Wavelength

The distance between successive wave crests (m)

Because MAMPs are very general, most plants are resistant against what?

The majority of potential pathogens

Frequency

The number of wave crests per time (cycles/second)

What is the positive effect that ROSs have on plants?

They are indicative of stress including UV-B stress so a plant sensing them causes them to upregulate defensive and protective measures

When are ROS produced and what do they damage?

They are produced during many forms of stress and they damage macromolecules such as proteins, nucleic acids, and lipids

Why are antioxidants important to almost all organisms??

They detoxify and neutralize reactive oxygen species (ROS)

How do HSPs function?

They function as "chaperones"--the interaction of many different proteins

What is the function of heat shock proteins?

They play an important role in thermoregulation

How do oligogalacturonides initiate a defense response when they're technically "self"?

They signal that the plant has been attacked--they are a signal of damage

What is synergism?

Toxicity of compounds potentiated in mixtures. Activity of mixture is higher than would be expected by adding up the activities of its individual constituents

True or False. Certain flavonoids protect plants from UV-B radiation

True

True or False. O2 and CO2 compete for the same binding site in Rubisco

True

True or False. The group of chemicals that is derived from phenylalanine and tyrosine is called phenylpropanoids

True

True or False. UV-B radiation leads to oxidative stress

True

True or False. Not all HSPs are induced by heat

True. Some are induced by cold, other stresses, or are constitutively present in a cell

The bonds between oxygen in ozone are broken when high energy ______ is absorbed

UV-B

Early atmosphere on Earth, before the release of O2, had high levels of ______ and _____, making terrestrial life impossible

UV-B and UV-C

Strategy adapted by C3 plants:

Using the Rubisco reaction to produce 2 PGA that are fed into the Calvin Cycle

Specialized anatomical structure of C4-plants

Vascular tissue is surrounded by 'bundle sheath cells'--connected to the mesophyll cells

Fundamental differences between vertebrate and plant immunity:

Vertebrates: -Acquired and innate immunity -"training" of immune cells to distinguish "self" from "alien" -Specialized immune cells for acquired and most innate immunity Plants: -Innate immunity only -no "training", surveillance system to distinguish self from alien (R genes and receptors) -all cells capable of defense

Strategy adapted by CAM plants

Very similar to the one employed by C4-plants, but the two CO2-fixing steps are not separated anatomically, but in time. 1) During the night, stomata open and PEP carboxylase fixes CO2 to produce malate which is stored in the vacuole during the night. 2) During the day, stomata are closed and no CO2 enters the leaves. Malate is transported back to the chloroplast and shunted into the Calvin Cycle, which requires ATP and NADPH produced during the light reactions of photosynthesis

The UV-B portion of the electromagnetic spectrum at ground level is __________ as compared to the energy contributed by the visible light

Very small

Short answer. When water enters guard cells, turgor increases and stomata open up. When it exits guard cells, turgor decreases and the stomata close. Water flow in and out of the guard cells can be explained by what principle or equation?

Water potential

Is ozone a reactive oxygen species?

Yes

Is the capability of a plant to defend itself against biotic stressors influenced by UV-B?

Yes! One of the most striking effects found was that UV-B affects plant-microbe and plant-insect interactions

Can plant cells be 'vaccinated'?

Yes, but this is not based on memory cells for immunity, but genetically determined induced defense

The recognition process triggers the ___________ response which is the activation of 'weapons' that restrict or kill the pathogens

actual defense

Nitrous oxide is released from _____________ through _____________

agriculture; fertilizers

Methane is also released from _____________ and _________________

agriculture; waste management

In CAM-plants, the two CO2 fixation steps are separated...

by day and night (stomata open at night and closed during the day)

How do plants recognize MAMPs and DAMPs in order to activate a defense response?

by membrane-bound receptor proteins

In C4-plants, the two CO2 fixation steps are separated...

by specialized leaf anatomy

What do plants possess to break down chitin and beta-glucan?

chitinases and beta-glucanases

The plants ability to recognize oligogalacturonides is an example of what?

damage-associated molecular patterns

Two different receptors can recognize different MAMPs, but activate a similar set of _____________

defense genes

Since the lytic enzymes produced by the plant are designed to break down the fungal cell wall, they are ________________

defensive enzymes

What does fungal endopolygalacturonase (PGase) do?

degrades polygalacturonic acid (pectin) to destroy cell wall. The breakdown products are oligogalacturonide fragments which act as elicitors (MAMPs)

When cells are wounded, ATP and other cellular content can get into the ________________

extracellular space

The term 'general defense' or MAMP-triggered immunity refers to...

features by which pathogens can be recognized by a plant

To avoid ozone exposure, plants can close their stomata, but there is a tradeoff because stomata are essential for....

gas exchange

The resistance strategy that most plants employ to respond to almost all pathogens is called __________________

general resistance

Short wavelength = _____ energy Long wavelength = _____ energy

high/low Example: UV-B = 280-320 nm --> high energy red light = 700 nm --> low energy

The phosphotransfer often results in activation of the _______ substrate

kinase

If stomata are open, ozone can damage the plasma membrane through ______________ which leads to altered _____________ structures in the membrane lipids. This reduces membrane integrity

lipid peroxidation, fatty acid

Each extracellular domain is highly specific and recognizes only _____ MAMP

one particular

Roughly 2 billion years ago, the accumulation of _____ in the atmosphere led to accumulation of _______ in the stratosphere

oxygen, ozone

The difference between general and host-specific plant defenses is at the level of...

pathogen recognition

By closing stomata, ________________ production is compromised resulting in reduced growth rates

photosynthetic

When GSH becomes oxidized, a ROS becomes...

reduced and thereby detoxified

Since heat stress leads to aggregation of proteins or misfolding, HSPs can take care of this by:

refolding the proteins or preventing protein aggregation. They can also facilitate the degradation of damaged proteins that can not be rescued anymore by the other HSP functions.

Perception of flagellin in both plants and animals triggers a ____________ which involves the same signaling components and leads to disease resistance

signaling pathway

Trees have been considered carbon _______ due to their ability to sequester carbon in wood where it will stay for a relatively long time

sink

The stomata tradeoff problem is not very pronounced in plants growing in ____________ climates

temperate --> the cooler temperatures do not favor the oxygenase reaction

Kinases can activate NADPH oxidase which leads to...

the generation of additional ROSs in a positive feedback loop

The amplification of the MAMP signal leads to the activation of _________ factors that bind to regulatory elements of defensive genes

transcription (this leads to the expression of the defense genes)

Kinases and other signal transducers may also activate...

transcription factors which bind to promoters of genes that code for enzymes involved in the synthesis of protective UV-B-absorbing sunscreen compounds

The Greenhouse effect traps heat in the ________ which results in a cooling effect of the ___________

troposphere; stratosphere

The change in absolute temperatures is more pronounced in the ______ than regions closer to the equator. This leads to thawing of the ________

tundra; permafrost

Plant cells can defend themselves against ozone by...

upregulating genes for antioxidant enzymes and enzymes that increase the synthesis of non-enzymatic antioxidants