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Plant Pathogenesis-Related (PR)
Proteins
Groups of proteins with different chemical properties produced in a cell within minutes or hours following inoculation, but all being more or less toxic to pathogens. TERM 2
Toxic Phenolics
DEFINITION 2 Specific compounds present in pathogen resistant individuals. When the pathogen is recognized by the host, the toxic phenolics are sent to disrupt the function of the pathogen, protecting the host from further infestation. TERM 3
Lignin
DEFINITION 3 A chemical compound found in all plant species. This polymer is highly resistant to enzymatic degradation, perhaps more resistant than any other plant substance. It is used to enhance the strength of cell walls in woody species. TERM 4
Salicylic Acid (SA)
DEFINITION 4 A phenolic acid which signals the presence of specific plant pathogenic proteins by reacting with the proteins. When SA reacts with the pathogenic proteins it signals the host cell to begin production of PR proteins. SA is an activator for PR protein synthesis. TERM 5
Phytoalexins
DEFINITION 5 Antimicrobial substances that inhibit the development of a fungus on hypersensitive tissue formed when host plant cells come in contact with the parasite.
Activated Oxygen Radicals
Superoxide (O2-), hydrogen peroxide (H2O2) and hydroxyl radicals (OH) are all forms of Activated Oxygen Species. These compounds are toxic to the host's cell wall (and potentially the pathogen's cell wall) and are responsible for HR-induced cell death. Activated Oxygen Species can also react with the host's phenolic compounds, turning them into more toxic compounds to fight off the pathogen. TERM 7
Phenylalanine
DEFINITION 7 One of the essential amino acids. TERM 8
Systemic Acquired Resistance (SAR)
DEFINITION 8 Systemically activated resistance after primary infection with a necrotizing pathogen accompanied by increasing levels of SA and PR proteins. TERM 9
Programmed Cell Death
DEFINITION 9 Death of specific cells of an organism, the initiation and execution of which is controlled by the organism. TERM 10
Oxidative Burst
DEFINITION 10 Step in the plant defense response where the reactive oxygen species are created/released.
Plasmogamy
A form of sexual reproduction where the cytoplasm of two parent mycelia fuse together without the fusion of nuclei. The secondary mycelium consists of dikaryotic cells, one nucleus from each of the parent mycelia. TERM 17
Karyogamy
DEFINITION 17 A form of sexual reproduction where the cytoplasm and nuclei of two parent mycelia fuse together. The secondary mycelium consists of diploid cells with one complete haploid genome from each of the parent mycelia. TERM 18
Chitinase
DEFINITION 18 Digestive enzymes that break down glycosidic bonds in chitin. Chitin is a complex sugar/polymer that composes the cell wall of fungi. TERM 19
Glucanase
DEFINITION 19 Digestive enzymes that break down glucans. Glucans are specific polymers found in the cell walls of fungi. TERM 20
Hypersensitive Response (HR)
DEFINITION 20 The localized defense reaction of a resistant plant to a pathogen.
Phenylalanine Ammonia Lyase (PAL)
An enzyme which is involved in the production of phytoalexins. TERM 22
Mitisporic Fungi
DEFINITION 22 Fungus which produces spores only through mitosis (imperfect fungi or deuteromycetes) TERM 23
Type III Secretion System
DEFINITION 23 A protein appendage found in pathogenic bacteria. The needle-like structure is used to secrete proteins that help the bacteria infect eukaryotic organisms. The proteins are secreted directly from the bacterial cell into the host cell. TERM 24
Gene-for-Gene Theory
DEFINITION 24 The concept that for each gene for virulence in a pathogen there is a corresponding gene for resistance in the host towards the pathogen. TERM 25
Constitutive Enzymes
DEFINITION 25 An enzyme whose presence and , often, concentration in a cell remain constant, unaffected by the presence of its substrate.
