Transposon-tagging identifies novel pathogenicity genes in Fusarium graminearum

With the increase of sequenced fungal genomes, high-throughput methods for functional analyses of genes are needed. We assessed the potential of a new transposon mutagenesis tool deploying a Fusarium oxysporum miniature inverted-repeat transposable element mimp1, mobilized by the transposase of impala, a Tc1-like transposon, to obtain knock-out mutants in Fusarium graminearum. We localized 91 mimp1 insertions which showed good distribution over the entire genome. The main exception was a major hotspot on chromosome 2 where independent insertions occurred at exactly the same nucleotide position. Furthermore insertions in promoter regions were over-represented. Screening 331 mutants for sexual development, radial growth and pathogenicity on wheat resulted in 19 mutants (5.7%) with altered phenotypes. Complementation with the original gene restored the wild-type phenotype in two selected mutants demonstrating the high tagging efficiency. This is the first report of a MITE transposon tagging system as an efficient mutagenesis tool in F. graminearum.