Transposons are important tools to inactivate chromosomal genes followed by a correlation with a particular phenotype or genotype. Here we demonstrated the development of a special type of genetically engineered transposon carrying an outward-directed inducible promoter in order to allow transcription of nearby genes. We have modified the mariner transposon TnYLB able to transpose in B. subtilis. This modified TnYLB carries an expression unit consisting of the xylose repressor xylR and an outward-directed promoter negatively controlled by this repressor. This TnYLB-XylOut transposon is able to turn on gene expression if insertion occurs close to a promoter-less gene. It will be an important tool to identify the function of genes either by turning on their expression or by enhanced expression depending on the xylose concentration.