BI431 Plant Phys Ch. 18

Northern Michigan University Dr. Maki

Allelopathy

Release of substances by plants into the environment that have harmful effects on other plants

Commensalism

Relationship between 2 organisms where one benefits and the other one is being harmed

Innate defenses

Plant defenses that are always available/ cutin, wax, lignin, spines, thorns, and resin

Inducible defenses

Defense responses that don’t exist until triggered by environmental stress

Trichomes

Hairlike structures that hold chemical signals such as essential oils

Secondary metabolites

Plant compounds that function as defenses against biotic stresses

Phytoalexins

Group of secondary metabolites that are antimicrobial and accumulate when the plant has an infection

Elicitors

Pathogen molecules or cell wall fragments that bind to plant proteins and act as a signal for defense mechanism activation

Salicylic acid

Acid used as a signal in systemic acquired resistance

Alpha-amylase inhibitors

Substances synthesized by plants that interfere with herbivore digestion by binding to a starch digesting enzyme

Lectins

Substances synthesized by plants that inhibit with herbivore digestion by binding to carbohydrates

Damage associated molecular patterns (DAMPs)

Molecules from nonpathogenic sources that initiate an immune response by binding to cellular pattern recognition receptors

Green-leaf volatiles

Organic molecules released through a plant’s stomata in response to damage

Effector

Molecules from pathogens that allow the pathogen to successfully colonize the plant

Pattern recognition receptors (PRRs)

Innate immune responses associated with DAMPs and MAMPS

Microbe-associated molecular patterns (MAMPs)

Microbe-produced molecules that are recognized by a cell’s pattern recognition receptors (PRRs)

Resistance (R) proteins

Proteins in cells that bind to elicitors from fungi, microbes, and nematodes

Effector-triggered immunity

Immune responses mediated by R proteins

Pathogenesis-related (PR) genes

Genes that encode for proteins that are antimicrobial or act in systemic defense mechanisms

Systemic acquires resistance (SAR)

Increased plant resistance against pathogens from the plant’s direct response/ salicylic acid is the hormone signal and methyl salicylate is the volatile

Hemiparasitic plants

Photosynthetic plants that can be parasitic

Holoparasitic plants

Non photosynthetic parasitic plants

Haustorium

Hyphal tissue of parasitic plant that penetrates another plant’s tissues

Phenolic compounds

Secondary metabolites with allelopathic effects/flavonoids and tannins

Flavonoids

Antimicrobial (phytoalexins), insecticidal, anti-estrogenic/ protect against UV damage and may be UV fluorescent

Tannins

General toxins that can bind to gut proteins and enzymes/ inhibit microbes

Terpenes

Largest class of secondary metabolites/ insecticidal but non-toxic to mammals/ includes volatile essential oils from trichomes

Limonoids

Non-volatile terpenes found in citrus fruit/ insecticidal but not harmful to mammals or pollinators

Cardenolides

Bitter terpenes that affect the heart muscle cells/ not harmful at low levels but deadly in high concentration

Nitrogen-containing compounds

Alkaloids and other groups synthesized from amino acids/ produced when a plant is attacked by an herbivore/ some herbivores can adapt to them

Cynanogenic glycosides

Non-toxic nitrogen-containing compound when intact but breaks down to cyanide when a plant is injured/ chemical and enzyme are physically separated but mixed during injury

Glucosinolates

Nitrogen-containing compound that breaks down to release volatiles/ creates a mustard smell

Non-protein amino acids

Nitrogen-containing compounds which can act as a mimic for other amino acids and target proteins in the gut

Endophytes

Fungi and bacteria that live in plant tissue and can help inhibit plant pathogens and herbivory/often produce products the host does not

Insect herbivores

Phloem feeders (aphids), cell content feeders (mites), and chewing insects (caterpillars)

Herbivore-associated molecular patterns (HAMPs)

Group of chemicals from herbivores that trigger defense responses

Mitogen-activated protein kinases (MAPK)

Phosphorylates a protein that Ca2+ binds to after an elicitor is recognized by the plant cell

Systemin

Only known polypeptide hormone/ binds to a receptor that synthesizes jasmonic acid that activates protease inhibitors

Jasmonic acid

Produced at site of plant damage and acts as a systemic signal after being sent through the phloem/xylem

Reactive oxygen species (ROS)

Can stunt the growth and development of plants but also serve as an antimicrobial stress response for signal transduction

Hypersensitive response

Cell apoptosis and nutrient sequestering around the encroachment of harmful bacteria

Induced systemic resistance (ISR)

Beneficial bacteria induce the systemic resistance of the plant/ involves jasmonic acid and ethylene