ABSTRACT
The development of symptoms, especially that of necrosis, following invasion of many pathogens is accompanied by an increased synthesis and/or accumulation of a class of plant proteins termed pathogenesis-related proteins (PRs). Synthesis or accumulation of PRs is occasionally accompanied by the development of local or systemic resistance to infection by related or unrelated pathogens. Adoption of a uniform system of nomenclature for PR proteins is highly desirable and needed to alleviate confusion which exists in the literature. Several PRs have been identified as chitinases or glucanases, and antibodies against many have been prepared. Consequently, techniques incorporating affinity chromatography offer excellent opportunities for obtaining these proteins in a highly purified form. Intercellular fluid recovered from leaves has served as the starting source material in purifying some PRs. Several PR proteins accumulate in cucumber leaves infected with viruses, bacteria, or fungi.
