MAIZE PATHOGENESIS-RELATED PROTEINS - CHARACTERIZATION AND CELLULAR-DISTRIBUTION OF 1,3-BETA-GLUCANASES AND CHITINASES INDUCED BY BROME MOSAIC-VIRUS INFECTION OR MERCURIC-CHLORIDE TREATMENT

Ten pathogenesis-related (PR) proteins have been extracted at pH 5·2 and purified from maize leaves after bromegrass mosaic virus infection or mercuric chloride treatment. Among these PR proteins several have been found to be 1,3-β-glucanases and chitinases. Thus PRm6a and PRm6b proteins are two acidic glucanases and PRm Ba1 a basic glucanase; PRmBa2 is a basic chitinase found in addition to the four previously characterized acidic chitinases (PRm3, PRm4, PRm5 and PRm7 proteins). The basic 1,3-β-glucanase account for about 15% of the total 1,3-β-glucanase activity and the basic chitinase for about 20% of the total chitinase activity. The cellular distribution of several PR proteins have been investigated, by immunodetection, in the intercellular fluid and in the crude extracts from maize protoplasts. It has been found that the acidic 1,3-β-glucanases and acidic chitinases have an extracellular localization, whereas the corresponding basic enzymes are located inside the cell. PRm2 protein a tobacco PR1b-type protein, is also located in the intercellular spaces of maize leaves. © 1990.