Functional Characterization of the Regulator Gene VosA in the Fungal Cereal Pathogen Cochliobolus sativus

VosA is one of the major components in the velvet complex that has been shown to be involved in regulation of secondary metabolism and fungal development in Aspergillus nidulans and several other filamentous fungi. However, its function is not well understood in plant pathogenic pathogens. In this study, we identified and characterized the orthologue of VosA (CsVosA) in the cereal fungal pathogen Cochliobolus sativus, which causes several important diseases (spot blotch, common root rot and kernel blight) in barley and wheat. Under both dark and light conditions, the gene deletion mutants (ΔCsVosA) produced larger conidia with less germination rate on minimum medium (MM), were more sensitive to oxidative stress (H₂O₂), had less melanin production and reduced trehalose in both conidia and mycelia as compared to the wild type strain ND90Pr. However, no significant difference in virulence was observed between ΔCsVosA and the wild type on inoculated barley lines. Interestingly, ΔCsVosA was significantly reduced in lesion number and size on the Brachypodium distachyon line Bd21 as compared to the wild type.