Pathogenesis-related (PR) proteins are
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
s produced in
plant
Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...
s in the event of a
pathogen
In biology, a pathogen (, "suffering", "passion" and , "producer of"), in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a Germ theory of d ...
attack.
They are
induced as part of
systemic acquired resistance. Infections activate genes that produce PR proteins. Some of these proteins are antimicrobial, attacking molecules in the cell wall of a bacterium or fungus. Others may function as signals that spread “news” of the infection to nearby cells. Infections also stimulate the cross-linking of molecules in the cell wall and the deposition of
lignin
Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidit ...
, responses that set up a local barricade that slows spread of the pathogen to other parts of the plant.
Salicylic acid
Salicylic acid is an organic compound with the formula HOC6H4COOH. A colorless (or white), bitter-tasting solid, it is a precursor to and a active metabolite, metabolite of acetylsalicylic acid (aspirin). It is a plant hormone, and has been lis ...
plays a role in the
resistance to pathogens by inducing the production of pathogenesis-related proteins.
Many
proteins found in wine are grape pathogen-related proteins.
Those include
thaumatin-like proteins and
chitinase
Chitinases (, chitodextrinase, 1,4-β-poly-N-acetylglucosaminidase, poly-β-glucosaminidase, β-1,4-poly-N-acetyl glucosamidinase, poly ,4-(N-acetyl-β-D-glucosaminide)glycanohydrolase, (1→4)-2-acetamido-2-deoxy-β-D-glucan glycanohydrola ...
s.
Many pathogenesis-related protein families also coincide with groups of human allergens, even though the allergy may have nothing to do with the defense function of the proteins.
[ Grouping these proteins by their sequence features allows for finding potential allergenic proteins from sequenced plant genomes, a field of study dubbed " allergenomics".
]
Classification
, 17 families of PR proteins have been named:[ This article contains quotations from this source, which is available under th]
Creative Commons Attribution 3.0 (CC BY 3.0)
license.
Identification
As PR proteins are produced when plant tissue is stressed, various ways of stress signaling is used to "bait" the plant into expressing PR genes for identification. Useful stressors include an actual infection or simply defense signals such as salicylate and methyl jasmonate. The proteins can be identified by isolation, peptide digestion, and matching against the genomic sequences ( protein sequencing). The sequences obtained can then be checked against known PR protein families for categorization.
See also
* Acibenzolar-S-methyl
* Glossary of phytopathology
* R gene, unrelated resistance proteins
References
Further reading
*
*
External links
WHO Allergen Nomenclature
for conversion of allergens to specific sequences.
* UniProt keyword
KW-0568
* Gene ontology mapping
GO:0009607GO:0006952
Plant proteins
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