GERMIN-LIKE OXALATE OXIDASE, A H2O2-PRODUCING ENZYME, ACCUMULATES IN BARLEY ATTACKED BY THE POWDERY MILDEW FUNGUS

Germin-like oxalate oxidase is an oligomeric enzyme which generates H2 O2. This paper reports increased activity of this enzyme in associatio n with the response of barley to the powdery mildew fungus, Erysiphe g raminis f.sp. hordei. The increase is detected in a colorimetric assay as well as on activity blots using extracts of both resistant and sus ceptible leaves. The increase is generally apparent from 24 h after in oculation. From 48 h after inoculation, there is an approximately 10-f old higher oxalate oxidase activity in the samples from inoculated pla nts compared with the controls. The oxalate oxidase activity increase appears 1-3 days earlier than PR-1 protein accumulation. SDS-PAGE anal ysis suggests that this pathogen-response oxalate oxidase is different from a commercially available barley oxalate oxidase.