Transposition of a Fungal Miniature Inverted-Repeat Transposable Element 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 Tc1-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 dinucleotides, 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

Transposition of the miniature inverted-repeat transposable element <i>mimp1</i> in the wheat pathogen <i>Fusarium culmorum</i>

High-throughput methods are needed for functional genomics analysis in Fusarium culmorum, the cause of crown and foot rot on wheat and a type B trichothecene producer. Our aim was to develop and test the efficacy of a double-component system based on the ability of the impala transposase to transactivate the miniature inverted-repeat transposable element mimp1 of Fusarium oxysporum. We report, for the first time, the application of a tagging system based on a heterologous transposon and of splinkerette-polymerase chain reaction to identify mimp1 flanking regions in the filamentous fungus F. culmorum. Similar to previous observations in Fusarium graminearum, mimp1 transposes in F. culmorum by a cut-and-paste mechanism into TA dinucleotides, which are duplicated on insertion. mimp1 was reinserted in open reading frames in 16.4% (i.e. 10 of 61) of the strains analysed, probably spanning throughout the entire genome of F. culmorum. The effectiveness of the mimp1/impala double-component system for gene tagging in F. culmorum was confirmed phenotypically for a putative aurofusarin gene. This system also allowed the identification of two genes putatively involved in oxidative stress-coping capabilities in F. culmorum, as well as a sequence specific to this fungus, thus suggesting the valuable exploratory role of this tool

Tagging pathogenicity genes in Fusarium graminearum using the transposon system mimp/impala

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 genome

Human papillomavirus (HPV) DNA triage of women with atypical squamous cells of undetermined significance with cobas 4800 HPV and Hybrid Capture 2 tests for detection of high-grade lesions of the uterine cervix

The triage of women with high-risk (HR) human papillomavirus (HPV)-positive smears for atypical squamous cells of undetermined significance (ASC-US) to colposcopy is now an integrated option in clinical guidelines. The performance of cobas 4800 HPV and that of Hybrid Capture 2 (HC2) for HR HPV DNA detection in cervical samples in PreservCyt were compared in 396 women referred to colposcopy for ASC-US. Of these, 316 did not have cervical intraepithelial neoplasia (CIN), 47 had CIN1, 29 had CIN2 or CIN3 (CIN2+), and 4 had CIN of unknown grade. HR HPV was detected in 129 (32.6%) and 149 (37.6%) samples with HC2 and cobas 4800 HPV, respectively (P = 0.15). The clinical sensitivities and specificities for detecting CIN2+ were 89.7% (95% confidence interval [CI], 72.8 to 97.2%) and 66.7% (95% CI, 61.7 to 71.3%) with cobas 4800 HPV and 93.1% (95% CI, 77.0 to 99.2%) and 72.2% (95% CI 67.4 to 76.5%) with HC2. The performance of cobas 4800 HPV was similar to that of HC2 for identifying women with ASC-US who would benefit the most from colposcopy

Usages et mésusages de l’informatique dans l’enseignement et la recherche en sciences sociales

Depuis plusieurs années, l’informatique a fait une entrée massive dans l’Université, suscitant beaucoup d’espoirs, quelques illusions et déceptions, mais aussi des utilisations fécondes aux conséquences encore mal mesurées. Le temps n’est plus aujourd’hui aux promesses, mais aux bilans réfléchis, et pour les différentes disciplines qui en font usage (ou mésusage). Le Groupe de recherche, fondé en 1977 par des chercheurs et enseignants français et québécois, a organisé un Colloque pour ce qui concerne l’enseignement et la recherche en sciences sociales et humaines, du 4 au 7 mai 1987. Chercheurs français et québécois ont confronté leurs pratiques et leurs expériences, montré les différentes utilisations de l’informatique à l’Université, réfléchi sur les illusions éventuelles et les mises en garde nécessaires, souligné les retombées de ces usages pour les enseignements et les recherches, pour le traitement des données comme pour les publications, dans l’Université et à ses portes. Une parfaite unanimité ne s’est pas faite sur les conséquences actuelles ou à prévoir, sur les limites et les dangers de certaines utilisations. On trouvera ici la reproduction de ces débats qui permettent d’apercevoir les nouveaux enjeux introduits par la diffusion de l’informatique et l’ampleur des problèmes qu’elle soulève

Comparative genomics reveals mobile pathogenicity chromosomes in Fusarium

Fusarium species are among the most important phytopathogenic and toxigenic fungi. To understand the molecular underpinnings of pathogenicity in the genus Fusarium, we compared the genomes of three phenotypically diverse species: Fusarium graminearum, Fusarium verticillioides and Fusarium oxysporum f. sp. lycopersici. Our analysis revealed lineage-specific (LS) genomic regions in F. oxysporum that include four entire chromosomes and account for more than one-quarter of the genome. LS regions are rich in transposons and genes with distinct evolutionary profiles but related to pathogenicity, indicative of horizontal acquisition. Experimentally, we demonstrate the transfer of two LS chromosomes between strains of F. oxysporum, converting a non-pathogenic strain into a pathogen. Transfer of LS chromosomes between otherwise genetically isolated strains explains the polyphyletic origin of host specificity and the emergence of new pathogenic lineages in F. oxysporum. These findings put the evolution of fungal pathogenicity into a new perspective

Comparative genomics reveals mobile pathogenicity chromosomes in Fusarium

International audienceFusarium species are among the most important phytopathogenic and toxigenic fungi. To understand the molecular underpinnings of pathogenicity in the genus Fusarium, we compared the genomes of three phenotypically diverse species: Fusarium graminearum, Fusarium verticillioides and Fusarium oxysporum f. sp. lycopersici. Our analysis revealed lineage-specific (LS) genomic regions in F. oxysporum that include four entire chromosomes and account for more than one-quarter of the genome. LS regions are rich in transposons and genes with distinct evolutionary profiles but related to pathogenicity, indicative of horizontal acquisition. Experimentally, we demonstrate the transfer of two LS chromosomes between strains of F. oxysporum, converting a non-pathogenic strain into a pathogen. Transfer of LS chromosomes between otherwise genetically isolated strains explains the polyphyletic origin of host specificity and the emergence of new pathogenic lineages in F. oxysporum. These findings put the evolution of fungal pathogenicity into a new perspective