FgHtf1 Regulates Global Gene Expression towards Aerial Mycelium and Conidiophore Formation in the Cereal Fungal Pathogen Fusarium graminearum

Abstract

The homeobox gene family of transcription factors (HTF) controls many developmental pathways and physiological processes in eukaryotes. We previously showed that a conserved HTF in the plant-pathogenic fungus Fusarium graminearum, Htf1 (FgHtf1), regulates conidium morphology in that organism. This study investigated the mechanism of FgHtf1-mediated regulation and identified putative FgHtf1 target genes by a chromatin immunoprecipitation assay combined with parallel DNA sequencing (ChIP-seq) and RNA sequencing. A total of 186 potential binding peaks, including 142 genes directly regulated by FgHtf1, were identified. Subsequent motif prediction analysis identified two DNA-binding motifs, TAAT and CTTGT. Among the FgHtf1 target genes were FgHTF1 itself and several important conidiation-related genes (e.g., FgCON7), the chitin synthase pathway genes, and the aurofusarin biosynthetic pathway genes. In addition, FgHtf1 may regulate the cAMP-protein kinase A (PKA)-Msn2/4 and Ca2+-calcineurin-Crz1 pathways. Taken together, these results suggest that, in addition to autoregulation, FgHtf1 also controls global gene expression and promotes a shift to aerial growth and conidiation in F. graminearum by activation of FgCON7 or other conidiation-related genes. IMPORTANCE The homeobox gene family of transcription factors is known to be involved in the development and conidiation of filamentous fungi. However, the regulatory mechanisms and downstream targets of homeobox genes remain unclear. FgHtf1 is a homeobox transcription factor that is required for phialide development and conidiogenesis in the plant pathogen F. graminearum. In this study, we identified FgHtf1-controlled target genes and binding motifs. We found that, besides autoregulation, FgHtf1 also controls global gene expression and promotes conidiation in F. graminearum by activation of genes necessary for aerial growth, FgCON7, and other conidiation-related genes.

The transcription factor Roc1 is a regulator of cellulose degradation in the wood-decaying mushroom Schizophyllum commune

“…It is currently not known what the role of Roc1 is in the regulation of these binding sites. A similar number of peaks has previously been reported for the Zn2Cys6 transcription factor PRO1 in Sordaria macrospora 75 , while fewer peaks were reported for other Zn2Cys6 transcription factors, including AflR in Aspergillus flavus 76 , CrzA in Aspergillus fumigatus 77 and FgHtf1 in Fusarium graminearum 78 .…”

The Transcription Factor Roc1 Is a Key Regulator of Cellulose Degradation in the Wood-Decaying Mushroom Schizophyllum commune

“…However, binding of Roc1 to these sites may affect expression of genes that are located considerably more distant, due to the 3D architecture of the genome. A similar number of ChIP-Seq peaks has previously been reported for the Zn 2 Cys 6 transcription factor PRO1 in Sordaria macrospora (40), while fewer peaks were reported for other Zn 2 Cys 6 transcription factors, including AflR in Aspergillus flavus (41), CrzA in Aspergillus fumigatus (42) and FgHtf1 in Fusarium graminearum (43). Since the consensus sequence of the binding motif is rather short, it seems likely that spurious binding of Roc1 may occur and that not every occurrence of the motif results in a change of gene expression after binding by Roc1.…”

The GTPase-Activating Protein FgGyp1 Is Important for Vegetative Growth, Conidiation, and Virulence and Negatively Regulates DON Biosynthesis in Fusarium graminearum

“…The incubations were done at 28 °C for 3 days. Previous protocols ( Cappellini and Peterson, 1965 ; Zheng et al, 2015 ; Fan et al, 2020 ) were used to assay for conidiation and sexual reproduction.…”