A FUSION PROMOTER CREATED BY A NEW INSERTION-SEQUENCE, IS1490, ACTIVATES TRANSCRIPTION OF 2,4,5-TRICHLOROPHENOXYACETIC ACID CATABOLIC GENESIN BURKHOLDERIA-CEPACIA AC1100

Transposition and transcriptional activation by insertion sequences in Burkholderia cepacia AC1100 were investigated, Two closely related ne w elements, IS1413 and IS1490, were identified and characterized, Thes e elements are not highly related to other insertion sequences identif ied in AC1100 or other B. cepacia isolates, Based on their structures and the sequences of the inverted terminal repeats and the putative tr ansposase protein, the insertion elements (IS elements) are similar to IST2 of Thiobacillus ferrooxidans and several related elements, All t he IS elements that have been identified in this strain are found in m ultiple copies (10 to 40), and they have high-level promoter activity capable of stimulating transcription from a distance up to 500 bp from a target gene, Strain AC1100 was originally isolated after prolonged selection for the ability to utilize the herbicide 2,4,5-trichlorophen oxyacetic acid (2,4,5-T) as a sole carbon source, Three IS elements ar e located near the first gene of the 2,4,5-T catabolic pathway, tftA. IS1490 inserted 110 bp upstream of tfrA and created a fusion promoter responsible for constitutive transcription of the gene, Our results co nfirm the hypothesis that IS elements play a central role in transcrip tion of 2,4,5-T genes and likely have stimulated rapid evolution of th e metabolic pathway.