The florfenicol-chloramphenicol exporter gene fexA is part of the novel transposon Tn558 from Staphylococcus lentus. Similarities between Tn558 and Tn554 from Staphylococcus aureus included the arrangement of the transposase genes tnpA to -C and an att554-like target sequence. Circular forms of Tn558 were detected and suggest the functional activity of this transposon.

OsES1, a rice homolog of the maize En/Spm transposon, is transcribed to produce TnpA-like and TnpD-like transcripts. However, an alternatively spliced form of the TnpA-like transcript, which was found to be suppressed in transgenic plants, was revealed to be due to atypical splicing of a Hipa-like CACTA transposon.

The florfenicol/chloramphenicol resistance gene floR was found to be part of the novel 4,284-bp transposon TnfloR from Escherichia coli. TnfloR consists of the gene floR, a putative regulatory gene, and the transposase gene tnpA. A circular form of TnfloR was detected and suggested the potential mobility of this transposon.

How heterocyst differentiation is regulated, once particular cells start to differentiate, remains largely unknown. Using near-saturation transposon mutagenesis and testing of transposon-tagged loci, we identified three presumptive regulatory genes not previously recognized as being required specifically for normal heterocyst maturation. One of these genes has a hitherto unreported mutant pheno...

The random transposon mutagenesis system P(junc)-TpaseIS(1223) is composed of plasmids pVI129, expressing IS1223 transposase, and pVI110, a suicide transposon plasmid carrying the P(junc) sequence, the substrate of the IS1223 transposase. This system is particularly efficient in Lactobacillus casei, as more than 10,000 stable, random mutants were routinely obtained via electroporation.

Mobile DNAs have had a central role in shaping our genome. More than half of our DNA is comprised of interspersed repeats resulting from replicative copy and paste events of retrotransposons. Although most are fixed, incapable of templating new copies, there are important exceptions to retrotransposon quiescence. De novo insertions cause genetic diseases and cancers, though reliably detecting t...

In animal cells, small RNA molecules, called piRNAs, defend the genome against selfish DNA elements such as transposons. In this issue, Klattenhoff et al. (2009) report that an HP1 family protein, Rhino, is required for piRNA generation and transposon silencing in Drosophila germline cells. The results provide a link between heterochromatin and piRNA-mediated genome defense.

Though transposable elements (TEs) have been considered as an efficient source of evolution, it has never been possible to test this hypothesis because most of TE insertions had occurred millions of years ago, or because currently active TEs have very few copies in a host genome. However, mPing, the first active DNA transposon in rice, was revealed to hold a key to answer this question. mPing h...