**6. Pathogenesis-related proteins (PR-proteins) with their transgenic expression**

With the development of modern DNA technology, it is possible to engineer transgenic plants transformed with genes to provide resistance against specific diseases. Recently the transgenic expression of various groups of PR proteins has enhanced the resistance of the transformed plant against several plant pathogens (**Table 2**). PR proteins are found in all organisms and are part of their innate immune systems. They have a wide range of activities, including disrupting fungal cell walls, permeabilizing membranes, inhibiting transcription, and inactivating ribosomes [117]. Genes coding for various PR proteins have been identified, cloned, and expressed in plants, preventing the development of specific diseases and conferring resistance to affected plants. Using modern biotechnology tools, various crops have been engineered to express, or over-express the PR proteins from different sources, such as (i) that are produced during the plant's defense response, (ii) derived from microorganisms or animal cells, (iii) synthetic peptides designed based on sequences of existing antimicrobial compounds [32, 118].

