Identification of eight effector candidate genes involved in early aggressiveness of the barley powdery mildew fungus

The barley powdery mildew fungus, Blumeria graminis f. sp. hordei (Bgh), expresses 491 candidate for secreted effector proteins (CSEPs), identified based on presence of a predicted signal peptide and relative sequence uniqueness. Virtually nothing is known about the mechanism of action of CSEPs. The present study used host-induced gene silencing (HIGS) to identify genes involved in early fungal aggressiveness. Screening of 22 selected CSEP-encoding genes suggested that CSEP0007, CSEP0025, CSEP0128, CSEP0211, CSEP0247, CSEP0345, CSEP0420 and CSEP0422 are individually required for normal levels of aggressiveness of Bgh. Expression data showed that these genes were up-regulated at initial stages of infection, suggesting their involvement in early fungal aggressiveness. Altogether, the findings expand the current knowledge of genes contributing to Bgh pathogenesis and provide the basis for future functional characterization.