Pathogenesis-related proteins: Role in plant defense

Plants have a well-developed defense response system to deal with different biotic and abiotic stresses. Inducible defense system is triggered by the effector molecules produced by pathogens resulting in the synthesis and accumulation of a special group of proteins known as pathogenesis-related proteins. The response is generally mediated by two signaling pathways, salicylic acid and jasmonic acid. Initially there were five families of PR proteins reported in the tobacco plant, but to date there are 17–19 classes reported to have a varied role and mechanism of action as antibacterial, antifungal, membrane permeabilizing, proteinase, peroxidase, ribonuclease, and lysozyme activities. PR genes have come up as suitable candidates for the production of stress-resistant transgenic plants.