Abstract
Fusarium head blight caused by Fusarium graminearum is an important disease of wheat and barley worldwide. In a previous study on functional characterization of the F. graminearum kinome, one protein kinase gene important for virulence is orthologous to SCH9 that is functionally related to the cAMP-PKA and TOR pathways in the budding yeast. In this study, we further characterized the functions of FgSCH9 in F. graminearum and its ortholog in Magnaporthe oryzae. The ΔFgsch9 mutant was slightly reduced in growth rate but significantly reduced in conidiation, DON production, and virulence on wheat heads and corn silks. It had increased tolerance to elevated temperatures but became hypersensitive to oxidative, hyperosmotic, cell wall, and membrane stresses. The ΔFgsch9 deletion also had conidium morphology defects and produced smaller conidia. These results suggest that FgSCH9 is important for stress responses, DON production, conidiogenesis, and pathogenesis in F. graminearum. In the rice blast fungus Magnaporthe oryzae, the ΔMosch9 mutant also was defective in conidiogenesis and pathogenesis. Interestingly, it also produced smaller conidia and appressoria. Taken together, our data indicate that the SCH9 kinase gene may have a conserved role in regulating conidium size and plant infection in phytopathogenic ascomycetes.
Highlights
IntroductionFusarium graminearum (teleomorph Gibberella zeae) is one of the major causal agents of wheat and barley head blight or scab in North America and other parts of the world [1,2]
Fusarium graminearum is one of the major causal agents of wheat and barley head blight or scab in North America and other parts of the world [1,2]
Genes of various biochemical or biological functions have been identified as important virulence or pathogenicity factors in F. graminearum, including other genes involved in DON biosynthesis [9,10], components of key signal transduction pathways [11,12,13,14], transcription factors of different DNA-binding domains [15,16,17], and several enzymes required for primary metabolism [18,19,20]
Summary
Fusarium graminearum (teleomorph Gibberella zeae) is one of the major causal agents of wheat and barley head blight or scab in North America and other parts of the world [1,2] It infects corn and other small grains. Like many other filamentous ascomycetes, F. graminearum has three mitogenactivated protein (MAP) kinase pathways, and all of them play critical roles in pathogenesis and DON production [21,22]. It has the well-conserved cAMP signaling pathway that is involved in the switching from saprophytic growth to infectious growth [23]. Two genes encoding the catalytic subunits of PKA have distinct and overlapping functions in regulating developmental and plant infection processes in F. graminearum [24]
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