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Recently, protective proteins of higher plants have drawn much attention from plant breeders . Because defense-related proteins usually provide a plant with resistance to stresses, varieties that are apt to intensively induce such proteins can be agriculturally valuable. Less toxic substances that cause crops to express defensive proteins are also being investigated as a new type of agrochemical. Moreover, some defense-related proteins will be constantly expressed in genetically modified plants [4-7]. However, several of these proteins have been proven to be latex allergens and cross-reactive allergens in fruits, vegetables, and pollen [8-10]. As such, it is probable that the crop content of allergenic proteins responsible for "oral allergy syndrome" (OAS) or similar syndromes has increased in response to traditional plant-breeding or the creation of stress-resistant varieties through the use of gene recombination techniques (Fig. 2). When a genetically modified new crop is brought to market as a food, its safety, including its possible allergenicity, must be strictly examined and reviewed in advance .
Table. Recommended Classification of Pathogenesis-Related Proteins (PRs)
|PR-1||tobacco PR-1a||antifungal?, 14-17kD|
|PR-2||tobacco PR-2||class I, II, and III endo-beta-1,3-glucanases, 25-35kD|
|PR-3||tobacco P, Q||class I, II, IV, V, VI, and VII endochitinases, about 30kD|
|PR-4||tobacco R||antifungal, win-like proteins, endochitinase activity,
similar to prohevein C-terminal domain, 13-19kD
|PR-5||tobacco S||antifungal, thaumatin-like proteins,
osmotins, zeamatins, permeatins,
similar to alpha-amylase/trypsin inhibitors
|PR-6||tomato inhibitor I||protease inhibitors, 6-13kD|
|PR-8||cucumber chitinase||class III chitinases, chitinase/lysozyme|
|PR-9||lignin-forming peroxidase||peroxidases, peroxidase-like proteins|
|PR-10||parsley PR-1||ribonucleases, Bet v 1-related proteins|
|PR-11||tobacco class V chitinase||endochitinase activity|
|PR-12||radish Ps-AFP3||plant defensins|
|PR-14||barley LTP4||nonspecific lipid transfer proteins (ns-LTPs)|
|PR-15||barley OxOa (germin)||oxalate oxidase|
|PR-16||barley OxOLP||oxalate-oxidase-like proteins|
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