The Forkhead Gene is Necessary for Proper Development in .

The forkhead domain genes are important for development and morphogenesis in fungi. Six forkhead genes - have been found in the genome of the model filamentous Ascomycete . To identify the gene(s) associated with fungal development, we examined mRNA levels of these six genes and found that the level of and mRNA was significantly elevated during asexual development and in conidia. To investigate the roles of FkhB and FkhD, we generated and deletion mutants and complemented strains and investigated their phenotypes. The deletion of , but not , affected fungal growth and both sexual and asexual development. The deletion mutant exhibited decreased colony size with distinctly pigmented (reddish) asexual spores and a significantly lower number of conidia compared with these features in the wild type (WT), although the level of sterigmatocystin was unaffected by the absence of . Furthermore, the deletion mutant produced sexual fruiting bodies (cleistothecia) smaller than those of WT, implying that the gene is involved in both asexual and sexual development. In addition, deletion reduced fungal tolerance to heat stress and decreased trehalose accumulation in conidia. Overall, these results suggest that plays a key role in proper fungal growth, development, and conidial stress tolerance in .