EN
The Tc1 transposable element has been found in a wide variety of organisms including vertebrates, insects and fungi but has not been previously reported in Microsporidia. In this study we characterize an intact DNA transposon (NbTc1) from the microsporidian Nosema bombycis. This transposable element encodes a 337 amino acid transposase sequence, which contains the D,D34E functional motif required for transposition. A Southern blot of N. bombycis DNA separated by pulsedesis shows that copies of the NbTc1 transposon are present on 10 of the 14 chromosomes of N. bombycis. Amino acid sequence variation among copies of the NbTc1 is low, suggesting a conserved function for this transposon within N. bombycis. Phylogenetic analysis indicates that NbTc1 is a new member of the Tc1 family lineage, quite distinct from all previously described Tc1 elements, including those from fungi, indicating that NbTc1 forms a unique clade of the Tc1 superfamily. However, the Tc1 transposon is too divergent to resolve the major phylogenetic relationships among these superfamilies. Reverse transcriptase PCR and Solexa sequencing suggest that NbTc1 possesses transcriptional activity. Considering the interest in Microsporidia as biological control agents, the NbTc1 transposon may be a useful vector for the efficient transfection of these important parasites into host species.