Although Sch9 orthologs are well conserved in filamentous ascomycetes, none of them have been functionally characterized. In this study, we found that the DFgsch9 mutant had a reduced growth rate and produced smaller conidia, which is similar to the sch9 deletion mutant of S. cerevisiae that exhibits slow growth and small cell size. In M. oryzae, conidia of the DMosch9 mutant also were smaller than those of the wild type. Even the appressoria produced by the DMosch9 mutant were smaller. In C. albicans, the cell size of the CaSCH9 deletion mutant was significantly reduced in comparison with that of the wild type WDR5-0103 strain. Therefore, SCH9 orthologs may have a conserved function in regulating conidium size in filamentous ascomycetes. In S. cerevisiae, SCH9 and SFP1 are required for BRD7552 carbon-source modulation of cell size. The TOR complex is well-conserved from yeast to human and it is involved in regulating growth-related signaling. It controls growth in response to nutrients by regulating translation, transcription, ribosome biogenesis, nutrient transport, and autophagy. In S. cerevisiae, SCH9 functions downstream from the TOR pathways for properly regulating ribosome biogenesis, translation initiation, and entry into G0 phase. In F. graminearum, the TOR pathway plays critical roles in regulating vegetative differentiation and virulence. It is likely that FgSCH9 is also functionally related to the TOR pathway in F. graminearum. Unlike S. cerevisiae that has TOR1 and TOR2, two TOR kinase genes, F. graminearum has a single essential TOR kinase gene. It will be interesting to determine the functional relationship between FgTor1 and FgSch9 by assaying the phosphorylation level or activity of FgSch9 in rapamycintreated samples. In the budding yeast, the Sch9 kinase is functionally related to the Ras-cAMP signaling pathway and it shares a large number of phosphorylation targets with PKA, such as Hog1 and Pfk2. Sch9 inhibits PKA activity and disruption of SCH9 increases PKA activities. In the fission yeast Schizosaccharomyces pombe, Sck1 and Sck2 are homologous to Sch9.