The Wor1-like Protein Fgp1 Regulates Pathogenicity, Toxin Synthesis and Reproduction in the Phytopathogenic Fungus <em>Fusarium</em> g<em>raminearum</em>

<div><p><em>WOR1</em> is a gene for a conserved fungal regulatory protein controlling the dimorphic switch and pathogenicity determents in <em>Candida albicans</em> and its ortholog in the plant pathogen <em>Fusarium oxysporum</em>, called <em>SGE1</em>, is required for pathogenicity and expression of key plant effector proteins. <em>F. graminearum</em>, an important pathogen of cereals, is not known to employ switching and no effector proteins from <em>F. graminearum</em> have been found to date that are required for infection. In this study, the potential role of the <em>WOR1</em>-like gene in pathogenesis was tested in this toxigenic fungus. Deletion of the <em>WOR1</em> ortholog (called <em>FGP1</em>) in <em>F. graminearum</em> results in greatly reduced pathogenicity and loss of trichothecene toxin accumulation in infected wheat plants and <em>in vitro</em>. The loss of toxin accumulation alone may be sufficient to explain the loss of pathogenicity to wheat. Under toxin-inducing conditions, expression of genes for trichothecene biosynthesis and many other genes are not detected or detected at lower levels in Δ<em>fgp1</em> strains. <em>FGP1</em> is also involved in the developmental processes of conidium formation and sexual reproduction and modulates a morphological change that accompanies mycotoxin production <em>in vitro</em>. The Wor1-like proteins in <em>Fusarium</em> species have highly conserved N-terminal regions and remarkably divergent C-termini. Interchanging the N- and C- terminal portions of proteins from <em>F. oxysporum</em> and <em>F. graminearum</em> resulted in partial to complete loss of function. Wor1-like proteins are conserved but have evolved to regulate pathogenicity in a range of fungi, likely by adaptations to the C-terminal portion of the protein.</p>