Submitted to: PLoS Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/16/2012
Publication Date: 5/31/2012
Citation: Jonkers, W., Dong, Y., Broz, K.L., Kistler, H.C. 2012. The Wor1-like protein Fgp1 regulates pathogenicity, toxin synthesis and reproduction in the phytopathogenic fungus Fusarium graminearum. PLoS Pathogens. 8(5):e1002724. Interpretive Summary: Plant pathogenic fungi can have devastating effects on agricultural production by reducing crop yield and quality. In addition, these fungi may generate mycotoxins that contaminate crops and thereby pose health risks when the contaminated products are consumed by humans or livestock. The cereal pathogen Fusarium graminearum infects wheat heads and spreads from spikelet to spikelet through the rachis by synthesizing trichothecene toxins, which are required for this spread. The mechanisms and environmental cues triggering the production of trichothecene toxins have been subject to investigation for many years. Here, we describe a conserved fungal gene that is required for pathogenicity and the synthesis of mycotoxins during infection and in culture. The gene is not required for normal vegetative growth of the fungus but is important for the developmental processes of asexual and sexual spore formation and for a putative switch to a pathogenic phase. Further knowledge of the genetic basis for toxin production may be used to develop alternative approaches to loss management and control. This information will be helpful to plant improvement specialists who are working to develop plants resistant to these pathogens or for developing novel strategies for disease control.
Technical Abstract: WOR1 is a gene for a conserved fungal regulatory protein controlling the dimorphic switch and pathogenicity in Candida albicans and its ortholog in the plant pathogen Fusarium oxysporum, called SGE1, is also required for pathogenicity and expression of plant effector proteins. F. graminearum, an important toxigenic pathogen of cereals, is not known to employ switching or effector proteins during infection and so its potential role in pathogenesis was tested in this fungus. Deletion of the WOR1 ortholog (called FGP1) in F. graminearum results in greatly reduced pathogenicity and loss of trichothecene toxin accumulation in infected wheat plants and in vitro. The loss of toxin accumulation alone is sufficient to explain the loss of pathogenicity to wheat. Under toxin-inducing conditions in vitro or in planta, expression of genes for trichothecene biosynthesis and many other genes are not detected or detected at lower levels in 'fgp1 strains. FGP1 is also involved in the developmental processes of conidium formation and sexual reproduction and modulates a morphological change that accompanies mycotoxin production in vitro. The Wor1-like proteins in Fusarium species have highly conserved N-terminal regions and remarkably divergent C-termini. Interchanging the N- and C- terminal portions of proteins from F. oxysporum and F. graminearum 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.