Inheritance of resistance to fenpropimorph and terbinafine, two sterol biosynthesis inhibitors, in Nectria haematococca

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Genome-Wide Analysis of the Fusarium oxysporum mimp Family of MITES and Mobilization of Both Native and De Novo Created mimps

We have performed a genome-wide analysis of the mimp family of miniature inverted-repeat transposable elements, taking advantage of the recent release of the F. oxysporum genome sequence. Using different approaches, we detected 103 mimp elements, corresponding to 75 nonredundant copies, half of which are located on a single small chromosome. Phylogenetic analysis identified at least six subfamilies, all remarkably homogeneous in size and sequence. Based on high sequence identity in the terminal inverted repeats (TIRs), mimp elements were connected to different impala members. To gain insights into the mechanisms at the origin and amplification of mimps, we studied the potential of impala to cross-mobilize different mimps, native but also created de novo by inserting a short DNA segment between two TIRs. Our results show that TIR sequences are the main requirement for mobilization but that additional parameters in the internal region are likely to influence transposition efficiency. Finally, we show that integration site preference of native versus newly transposed mimps greatly varies in the host genomes used in this study

Inheritance and mechanisms of resistance to tebuconazole, a sterol C14-demethylation inhibitor, in Nectria haematococca

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Transposition of a fungal mite through the action of a Tc1-like transposase

The mimp1 element previously identified in the ascomycete fungus Fusarium oxysporum has hallmarks of miniature inverted-repeat transposable elements (MITEs): short size, terminal inverted repeats (TIRs), structural homogeneity, and a stable secondary structure. Since mimp1 has no coding capacity, its mobilization requires a transposase-encoding element. On the basis of the similarity of TIRs and target-site preference with the autonomous Tcl-like element impala, together with a correlated distribution of both elements among the Fusarium genus, we investigated the ability of mimp1 to jump upon expression of the impala transposase provided in trans. Under these conditions, we present evidence that mimp1 transposes by a cut-and-paste mechanism into TA dinucleoticles, which are duplicated upon insertion. Our results also show that mimp1 reinserts very frequently in genic regions for at least one-third of the cases. We also show that the mimp1/impala, double-component system is fully functional in the heterologous species F. graminearum, allowing the development of a highly efficient tool for gene tagging in filamentous fungi

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

Tagging Pathogenicity genes in Fusarium graminearum using the transposon system mimp/impala (Session 4: Pathogenesis and Plant Pathology)

Transposon mutagenesis was applied to generate mutants in Fusarium graminearum. The mimp1/impala system originally identified in F. oxysporum proved very promising for mutagenesis as the transposon and reinserted at high frequency in (the vicinity) of genes. A collection of mutants was screened for growth, for pathogenicity and for perithecia production.Several mutants blocked in one or more functions were obtained. The wild-type phenotype of one such mutant could be restored by complementation with a non-disrupted copy of the gene. In addition reinsertions occurred on each of the four chromosomes of F. graminearum, making this system a powerful tool in the functional analyses of the > 10,000 genes predicted in the F. graminearum genom