Loss of glucosylceramide synthase impairs the growth and virulence of Fusarium oxysporum f. sp. cubense

Abstract Glucosylceramides are a class of membrane lipids that serve as vital structural and signaling molecules in eukaryotes. In this study, we explored the function of FocGCS, a glucosylceramide synthase (GCS) in Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4) that causes Fusarium wilt in banana plants. FocGCS is highly expressed in germinating conidia and during early infection stage of Foc TR4. Disruption of FocGCS resulted in severely retarded vegetative growth, reduced conidiation, and production of morphologically abnormal conidia. Sphingolipid profiling revealed that the FocGCS null mutant lacks glucosylceramide. Pathogenicity assays on banana plants revealed substantial loss of virulence in the FocGCS null mutant. Moreover, biochemical analyses indicated that FocGCS is involved in cell wall integrity but is not required for oxidative and osmotic stress tolerance in Foc TR4. Transcriptome analysis suggested that disruption of FocGCS strongly affects transmembrane transport in Foc TR4. Our findings show that GCS is essential for normal fungal growth and pathogenesis in Foc TR4.