A feedback regulation of FgHtf1-FgCon7 loop in conidiogenesis and development of Fusarium graminearum.

The transcription factor FgHtf1 is important for conidiogenesis in Fusarium graminearum and it positively regulates the expression of the sporulation-related gene FgCON7. However, the regulatory mechanism underlying its functions is still unclear. The present study intends to uncover the functional mechanism of FgHtf1 in relation to FgCon7 in F. graminearum. We demonstrated that FgCON7 serves as a target gene for FgHtf1. Interestingly, FgCon7 also binds the promoter region of FgHTF1 to negatively regulate its expression, thus forming a negative-feedback loop. We demonstrated that FgHtf1 and FgCon7 have functional redundancy in fungal development. FgCon7 localizes in the nucleus and has transcriptional activation activity. Deletion of FgCON7 significantly reduces conidia production. 4444 genes were regulated by FgCon7 in ChIP-Seq, and RNA-Seq revealed 4430 differentially expressed genes in FgCON7 deletion mutant, with CCAAT serving as a consensus binding motif of FgCon7 to the target genes. FgCon7 directly binds the promoter regions of FgMSN2, FgABAA, FgVEA and FgSMT3 genes and regulates their expression. These genes were found to be important for conidiogenesis. To our knowledge, this is the first study that unveiled the mutual regulatory functions of FgCON7 and FgHTF1 to form a negative-feedback loop, and how the loop mediates sporulation in F. graminearum.