Pathogenesis-related (PR) proteins are proteins produced in plants in the event of a pathogen 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, responses that set up a local barricade that slows spread of the pathogen to other parts of the plant.
Salicylic acid 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 chitinases.