Functional Characterization Of The Hdacs Genes In Fusarium Graminearum

Fusarium head blight (FHB), caused by Fusarium graminearum, is one of the most devastating fungal diseases in wheat. Functional genomics of F. graminearum has been significantly important since the wide-type PH-1 genome was sequenced in 2003. Shortage of effective resistance gene and sources for the prevention or immune of the fungus, no wheat cultivars resistant to WHB are commercialized. Gene knock out based on homologous recombination, along with the corresponding transformation system, has been widely used in functional genomic study of F. graminearum. In this study, we constructed the mutants of two histone deacetylase (HDAC) families class I (HDF4), class II (HDF1, HDF2, HDF3), and the double mutants hdf1hdf2 and hdf1hdf3 in F. graminearum. The molecular mechanism of HDACs genes in development and pathogenicity of F. graminearum was then studied, which will serve theoretical basis for control of the disease.The F. graminearum genome has one predicted class I HDAC gene that is homologous to yeast RPD3. It also contains three class II HDAC genes that are homologous to HOS2, HDA1, and HOS3 in S. cerevisiae. Mutants deleted for these four HDAC genes were generated with the split-marker approach. Infection assays with flowering wheat heads indicated that the HDF4 and HDF1 (FGSG₀1353) genes are important for plant infection. While the hdf4 mutant was severely reduced in vegetative growth, the hdf1 mutant had relatively normal growth rate. The latter produced fewer conidia and shorter aerial hyphae. On mating plates, the hdf1 mutant was sterile. Instead of forming protoperithecia or perithecia, it produced abundant sporodochia with massive amount of macroconidia. In 16 h germlings, the mutant accumulated numerous lipid droplets. The hdf1 mutant was normal in the initial penetration but failed to spread to the rachis of flowering wheat heads. The hdf4 did not caused disease in wheat head. These data suggested that deletion of HDF1 likely affected proper regulation of subsets of genes involved in sexual reproduction, conidiation, lipid metabolism, and plant infection.