ABSTRACT
The survival of cellular organisms depends on the faithful replication and transmission of DNA. Regulatory factor X (RFX) transcription factors are well conserved in animals and fungi, but their functions are diverse, ranging from the DNA damage response to ciliary gene regulation. We investigated the role of the sole RFX transcription factor, RFX1, in the plant-pathogenic fungus
Fusarium graminearum
. Deletion of
rfx1
resulted in multiple defects in hyphal growth, conidiation, virulence, and sexual development. Deletion mutants of
rfx1
were more sensitive to various types of DNA damage than the wild-type strain. Septum formation was inhibited and micronuclei were produced in the
rfx1
deletion mutants. The results of the neutral comet assay demonstrated that disruption of
rfx1
function caused spontaneous DNA double-strand breaks (DSBs). The transcript levels of genes involved in DNA DSB repair were upregulated in the
rfx1
deletion mutants. DNA DSBs produced micronuclei and delayed septum formation in
F. graminearum
. Green fluorescent protein (GFP)-tagged RFX1 localized in nuclei and exhibited high expression levels in growing hyphae and conidiophores, where nuclear division was actively occurring. RNA-sequencing-based transcriptomic analysis revealed that RFX1 suppressed the expression of many genes, including those required for the repair of DNA damage. Taken together, these findings indicate that the transcriptional repressor
rfx1
performs crucial roles during normal cell growth by maintaining genome integrity.
Characterization of the CCAAT-binding transcription factor complex in the plant pathogenic fungus Fusarium graminearum
