Expression of exo-polygalacturonases in Botrytis cinerea

The pathogenic fungus. Botrytis cinerea, causing gray mold disease in a var iety of plant species. secretes at least four polygalacturonases (PGs), cel l wall degrading enzymes. Among them, we prepared polyclonal antibody again st purified 66-kDa exo-PG in rabbit. Immunoblot analysis revealed that the antibody recognized two exo-PGs, 66 kDa and 70 kDa in molecular mass. secre ted from B. cinerea cultured in the medium containing citrus pectin as a ca rbon source. By immunohistochemical analysis. the expression of exo-PGs was identified in cucumber leaves inoculated with spores of B. cinerea. The ex o-PGs were observed 9 h after inoculation, and the amount of exo-PGs increa sed with time in the leaves. The exo-PGs were induced by polygalacturonic a cid as well as its monomer, galacturonic acid, in vitro. The expression of 66-kDa exo-PG (exo-PG I) increased with time of culture, while 70-kDa exo-P G (exo-PG II) was transiently expressed soon after the start of culture. Th erefore. exo-PGs might play an important role in pathogenesis at an early s tage of infection as well as in tissue maceration of host plant. (C) 2001 F ederation of European Microbiological Societies. Published by Elsevier Scie nce B.V. All rights reserved.