In vitro analysis of the role of glucose oxidase from Talaromyces flavus in biocontrol of the plant pathogen Verticillium dahliae.

Culture filtrates from Talaromyces flavus grown on glucose contained high levels of glucose oxidase activity, while culture filtrates from T. flavus grown on xylan contained negligible glucose oxidase activity. Culture filtrates from T-flavus grown on both media contained complex protein profiles. However, only culture filtrates from T. flavus grown on glucose inhibited germination of microsclerotia of Verticillium dahliae in in vitro inhibition assays. A polyclonal antiserum preparation, pABGO-1, raised against purified glucose oxidase from T. flavus was highly specific for glucose oxidase. Only one protein band in culture filtrates (from glucose medium), migrating at 71 kDa, was detected in Western blots (immunoblots) with this antiserum. This band comigrated with purified glucose oxidase. No bands were detected in culture filtrates from the xylan medium. Glucose oxidase was removed via immunoprecipitation from culture filtrates of T. flavus grown in glucose medium, resulting in filtrates which no longer inhibited in vitro microsclerotial germination. When glucose oxidase-depleted filtrates were amended with purified glucose oxidase from T. flavus, the ability to kill microsclerotia in vitro was restored to original levels. We conclude that glucose oxidase is the only protein in culture filtrates of T. flavus responsible for inhibition of germination of microsclerotia of V. dahliae.