The roles of aspartic proteinase and endo-pectin lyase enzymes in the primary stages of infection and pathogenesis of various host tissues by different isolates of Botrytis cinerea Pers ex. Pers

Abstract

A single spore isolate of Botrytis cinerea, obtained from carrot tissue, produced an aspartic proteinase and an endo-pectin lyase both in vitro in a liquid medium containing 0.4% gelatin as protein source and in infected carrot tissue. Both enzymes caused cell death and induced resistance to B. cinerea in surface cell layers of carrot root slices when applied at relatively low concentrations. At higher concentrations, both caused extensive cell death in carrot tissue and of carrot suspension cells. Neither enzyme lysed osmotically balanced carrot protoplasts unless carrot cell wall preparations were also present. Plasmolysed carrot cells were protected from the phytotoxic activity of the endo-pectin lyase but not from proteinase-induced damage. It is suggested that the phytotoxic activity of both the endo-pectin lyase and aspartic proteinase is indirectly caused by the toxic effect of cell wall components released by each enzyme. Accumulation of 6-methoxymellein was induced in carrot root slices by soluble, non-phytotoxic, elicitors released as a result of the action of aspartic proteinase or endo-pectin lyase on carrot cell walls. Proteinase production was an early event in infection of carrot, strawberry, raspberry, cabbage, grape and broad bean by eight different isolates of the pathogen. The level of infection in these hosts was markedly reduced when spores were pre-treated with pepstatin, a specific inhibitor of the aspartic proteinase, implying a primary role for this enzyme in pathogenesis.