Some of these proteins are antimicrobial, attacking molecules in the cell wall of a bacterium or fungus.
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.
[2] Salicylic acid plays a role in the resistance to pathogens by inducing the production of pathogenesis-related proteins.
Useful stressors include an actual infection or simply defense signals such as salicylate and methyl jasmonate.
The sequences obtained can then be checked against known PR protein families for categorization.