Fusarium graminearum ATP-Binding Cassette Transporter Gene FgABCC9 Is Required for Its Transportation of Salicylic Acid, Fungicide Resistance, Mycelial Growth and Pathogenicity towards Wheat

Abstract

ATP-binding cassette (ABC) transporters hydrolyze ATP to transport a wide range of substrates. <i>Fusarium graminearum</i> is a major causal agent of Fusarium head blight, which is a severe disease in wheat worldwide. <i>FgABCC9</i> (<i>FG05_07325</i>) encodes an ABC-C (ABC transporter family C) transporter in <i>F. graminearum</i>, which was highly expressed during the infection in wheat and was up-regulated by the plant defense hormone salicylic acid (SA) and the fungicide tebuconazole. The predicted tertiary structure of the FgABCC9 protein was consistent with the schematic of the ABC exporter. Deletion of <i>FgABCC9</i> resulted in decreased mycelial growth, increased sensitivity to SA and tebuconazole, reduced accumulation of deoxynivalenol (DON), and less pathogenicity towards wheat. Re-introduction of a functional <i>FgABCC9</i> gene into Δ<i>FgABCC9</i> recovered the phenotypes of the wild type strain. Transgenic expression of <i>FgABCC9</i> in <i>Arabidopsis thaliana</i> increased the accumulation of SA in its leaves without activating SA signaling, which suggests that <i>FgABCC9</i> functions as an SA exporter. Taken together, <i>FgABCC9</i> encodes an ABC exporter, which is critical for fungal exportation of SA, response to tebuconazole, mycelial growth, and pathogenicity towards wheat.