Fig. 3

Mobility efficiency of Ef.PcfG and Ll.LtrB in L. lactis. a Schematic of the two-plasmid intron mobility assay. The assay consists of co-transforming both an intron donor and an intron recipient plasmid in L. lactis cells (NZ9800ΔltrB) and monitoring for the appearance of intron mobility products. The intron donor plasmid harbors the pcfG or ltrB genes interrupted by their cognate or exchanged introns under the control of the nisin-inducible promoter (Pnis). The recipient plasmid contains either the ltrB-HS or the pcfG-HS (E1/E2). Upon nisin induction the intron can move from the donor to the recipient plasmid generating mobility products. Plasmid mixes (donor, recipient, mobility product) from independent mobility assays are recovered and the intron mobility efficiency is calculated as the percentage of recipient plasmids invaded by the intron (mobility product / (recipient + mobility product)). b Mobility efficiency of Ef.PcfG and Ll.LtrB at their own and each other’s homing sites. Two independent series of mobility assays were performed by expressing both introns flanked by either their wild-type (Wild-type flanking exons) or swapped exons (Exchanged flanking exons). Regardless of their flanking exons (Wild-type or exchanged), the mobility efficiency of both introns to the pcfG-HS is significantly higher (p < 0.05) than their efficiency towards the ltrB-HS while the mobility efficiency of Ll.LtrB to the ltrB-HS is significantly higher (p < 0.05) than Ef.PcfG. Each mobility efficiency value corresponds to the average of six independent mobility assays