Functional Analysis Of FgCHS8 Gene In Fusarium Graminearum

Fusarium graminearum is the major causal agent of Fusarium head blight ?FHB? of wheat, one of the most devastating plant diseases worldwide. To control FHB, it is becoming very improtant to study the pathogenesis of F. graminearum. Chitin is an important structural component of cell wall, and plays a critical role in growth and reproduction in most filamentous fungi. Chitin synthases ?CHS? is an rate-limiting enzyme for chitin synthesis and involved in maintaining the physical strength of cell wall. Salicylic acid ?SA? is an important resistant hormone of plant. Here we analyzed the function of a CHS gene ?FGSG₀6550?, which was down-regulated by SA. The results were listed as follows:1. The sequence of FGSG₀6550 gene was downloaded from Ensembl Fungi database. Phylogenic analysis indicated that fungal CHS genes could be divided into three divisions and eight classes. FGSG 06550 belongs to division II and class VIII, and it was named as FgCHS8. FGSG₀6550 protein has three transmembrane domains, a chitin_synth₂ ?pfam03142? domain and a cytochrome b5-binding type domain.2. No significant difference was observed for the length, width and number of septam of conidia of WT, AFgCHS8 and C-FgCHS8. Compared to WT and C-FgCHS8, mycelial growth of AFgCHS8 was reduced on plates supplemented with with HCl, NaCl, SDS, H2O2 and SA, indicating enhanced sensitivity of A.FgCHS8 to stresses.3. The gene sequence of FgCHS8 was ligated with green fluorescent protein gene ?GFP? to make a FgCHS8::GFP fusion, and then transformed into ?FgCHS8. C-FgCHS8 with a GFP tag was used to clarify the subcellular location of FgCHS8 protein. In the early stage of growth, FgCHS8 was only observed in the septa zone. However, FgCHS8 was distributed across the entire cellular membrane after growing for 4 d on plates, suggesting an important role for FgCHS8 in cell wall development.4. The growth of WT, AFgCHS8 and C-FgCHS8 was compared on plates with 1 mM congo red. The AFgCHS8 mutant had lighter color than WT and C-FgCHS8 mutant. Furthermore, the chitin synthase activity and chitin content, of ?FgCHS8 mutant were reduced compared to WT and C-FgCHS8, indicating that FgCHS8 gene contributes to biosynthesis of chitin.5. Pathogenicity of ?FgCHS8 was evaluated by point inoculation of conidial suspensions in flowering wheat heads. ?FgCHS8 caused much less disease. The content of deoxynivalenol ?DON? in liquid media and in wheat head was reduced. The results shown that FgCHS8 is important for pathogenicity and DON production in F. graminearum.