The Sch9 Kinase Regulates Conidium Size, Stress Responses, and Pathogenesis in Fusarium graminearum

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.

The Aspergillus fumigatus SchASCH9 kinase modulates SakAHOG1 MAP kinase activity and it is essential for virulence

“…Recently, a novel role for C. albicans Sch9 in genetic stability was reported since deletion of CaSch9 leads to a 150‐fold to 750‐fold increase in chromosome loss (Varshney et al ., .). In the rice blast fungus Magnaporthe oryzae , the ΔMosch9 mutant has defects in conidiation and pathogenesis, producing smaller conidia and appressoria (Chen et al ., ; Gu et al ., ). The F. graminearum ΔFgSch9 mutant has reduced production of the mycotoxin deoxynivalenol and was avirulent (Chen et al ., ; Gu et al ., ).…”

“…In the rice blast fungus Magnaporthe oryzae , the ΔMosch9 mutant has defects in conidiation and pathogenesis, producing smaller conidia and appressoria (Chen et al ., ; Gu et al ., ). The F. graminearum ΔFgSch9 mutant has reduced production of the mycotoxin deoxynivalenol and was avirulent (Chen et al ., ; Gu et al ., ). Taken together, these studies indicate that Sch9 homologues play an important role in virulence and pathogenicity in different fungal pathogens of plants and animals.…”

“…This raised the interesting hypothesis that Sch9p might act as an intermediary for the crosstalk between TOR and HOG pathways. Accordingly, in the filamentous phytopathogen F. graminearum , the Δ FgSch9 mutant exhibited increased sensitivity to osmotic and oxidative stress, cell wall‐damaging agents and rapamycin, while showing increased thermal tolerance (Chen et al ., ; Gu et al ., ). In addition, co‐immunoprecipitation and affinity capture‐mass spectrometry showed that FgSch9 interacted with FgTOR and FgHog1.…”

The FgSRP1 SR‐protein gene is important for plant infection and pre‐mRNA processing in Fusarium graminearum

“…For plant infection assays, conidia from 5‐day‐old CMC cultures (re‐suspended to 10 5 spores/ml in sterile water) or culture blocks from three‐day‐old PDA plates were used to inoculate flowering wheat heads of cultivar Xiaoyan22 or corn silks as described (Gale et al ., ; Hou et al ., ). Wheat spikelets with typical head blight disease symptoms were examined 14 days post‐inoculation (dpi) and disease indexes were estimated as described (Chen et al ., ). Infected corn stalks were examined 6‐dpi (Seong et al ., ).…”

Lipid Signaling via Pkh1/2 Regulates Fungal CO 2 Sensing through the Kinase Sch9

“…It is conserved in S. cerevisiae , C. glabrata , and C. albicans but is also found in less-related fungal species like Fusarium graminearum (39). In mammalian cells, it has been hypothesized that PKB/Akt is the Sch9 homologue (40), although later studies suggest that Sch9 is more closely related to S6K1 (31), which acts downstream of TORC1.…”