Development of a markerless gene replacement system in Corynebacterium glutamicum using upp as a counter-selection marker.

Corynebacterium glutamicum is well-established for industrial and biotechnological applications. However, its genetic manipulation has generally lagged behind traditional genetic models. In this study, a counter-selectable marker gene upp was firstly confirmed to be more efficient than traditional sacB. Furthermore, a markerless gene replacement system was developed by combining upp with double-strand break repair caused by the exogenous endonuclease I-SceI. Finally, genetic modification using a dsDNA PCR fragment was carried out with the expression of recombinase/exonuclease RecE/RecT. Our results show that the genetic modification system allows precise and markerless gene replacement without altering the chromosome, with a simplified screening procedure to generate its modification.