Fig. 2.

Selection and screening for plasmid retrotransposition events. (A) The pLERIG intron donor. The RIG donor contains the kan^R (Kan) gene interrupted by an inverted group I intron (I). Retrotransposition can take place into either the host chromosome (Lower Left) or the donor plasmid itself (Lower Right). (B) Hybridization probe. Kan^R colonies were hybridized against a 24-nt kan^R probe having 12 nt each of upstream and downstream sequences flanking the group I td intron (gpI) (4). Probe binding favors the joined kan^R sequences in retrotransposition products over donor sequences with split of homology. (C) Representative result of hybridization. (D) Interpretation of hybridization signals in C. 0, no retrotransposition; 1, chromosomal retrotransposition; 2, plasmid retrotransposition.