Functional studies on the role of reactive oxygen intermediates in the resistance of barley against powdery mildew

Abstract

The role of reactive oxygen intermediate (ROI) accumulation in resistance and susceptibility of plants to parasitic fungi is still little understood. We examined the spatial and temporal occurrence of different ROIs in barley after inoculation with the biotrophic fungus Blumeria graminis f.sp. hordei (Bgh, barley powdery mildew fungus). Using histochemical analyses, we collected correlative data indicating that H2O2 and O2*- play different roles in background penetration resistance to Bgh. To study the role of O2*- in detail, we isolated barley cDNAs encoding a NADPH oxidase GP91PHOX homologue and a RACB homologue, which may be involved in NADPH oxidase activation. Interestingly, transient silencing of RACB or GP91PHOX via sequence-specific RNA interference enhanced penetration resistance of barley to Bgh. Together, data reveal rather a negative than a positive role of superoxide generation in background resistance of barley to Bgh.

Keywords

• barley
• background resistance
• blumeria graminis f.sp. hordei
• hordeum vulgare
• papilla
• gene silencing
• rna interference