Transposition of a Fungal Miniature Inverted-Repeat Transposable Element Through the Action of a Tc1-Like Transposase

Abstract

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. M INIATURE inverted-repeat transposable elements (MITEs) are a particular group of transposable elements (TEs), first described in plants (Bureau and

A Helitron-Like Transposon Superfamily from Lepidoptera Disrupts (GAAA)n Microsatellites and is Responsible for Flanking Sequence Similarity within a Microsatellite Family

“…T nucleotide content, and secondary structures that include terminal inverted repeats (TIRs; Wessler et al 1995) or subterminal inverted repeats (SIRs; Tu 2000). MITEs lack an internal protein coding region, and mobility is mediated by trans-acting factors encoded by related autonomous TEs (Dufresne et al 2006). MITEs are found ubiquitously within eukaryotic genomes, including mosquito (Tu 2000;Quesneville et al 2006), Drosophila (Locke et al 1999;Vivas et al 1999;Miller et al 2000;Wilder and Hollocher 2001;Yang and Barbash 2008), and Lepidoptera (Chen and Li 2007;Coates et al 2009) and have a role in altering genome structure including insertion at microsatellite loci (Akagi et al 2001).…”

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

“…pNm2Hr carries a mimp2 element into the first intron of the niaD gene and was constructed following the same steps as for the pNm1H18 construct (Dufresne et al 2007). The mimp2 copy corresponds to the reamplification of the mimp2 element (AF076625) previously described (Hua- Van et al 2000) using the HindImp primer (5 0 -GCCC TAAGCTTACAGTGGGGTGCAATAAGTTTG-3 0 ).…”

“…Protoplast transformation was performed as previously described (Dufresne et al 2007). Plugs of each cotransformant were picked on plates of nitrate minimal agar medium.…”

“…Similarity searches based on TIR sequences have allowed the identification of autonomous class II elements, potentially responsible for the mobilization of MITEs (Feschotte and Mouches 2000;Feschotte et al 2003;Jiang et al 2003;Kikuchi et al 2003;Macas et al 2005;Saito et al 2005;Quesneville et al 2006). However, only a few recent studies have demonstrated, either by in vitro biochemical approaches (Loot et al 2006;Feschotte et al 2005) or in vivo (Yang et al 2007;Dufresne et al 2007), that class II transposases do have the potential to mobilize MITEs.…”

“…These elements, called mimp1 and mimp2, exhibit features of MITEs. Recently, we demonstrated that mimp1 is mobilized through the action of the impalaE transposase (Dufresne et al 2007).…”