Figure 3.

Transcription of aadA and nptII in Gene Transfer Lines before and after Activation of the Spectionmycin/Streptomycin Resistance Gene aadA.

(A) Detection of aadA transcripts by hybridization with a probe spanning the aadA coding region. While no aadA transcripts are detectable in the two gene transfer lines Nt-GT21 and Nt-GT31, all lines selected for spectinomycin and streptomycin resistance show transcriptional activation of the nuclear aadA gene. Different transcript sizes suggest that different rearrangements have occurred in different lines.

(B) Detection of nptII transcripts by hybridization with a probe spanning the nptII coding region. Most lines selected for activation of the aadA gene lack the prominent 1.2-kb nptII transcript present in the two original gene transfer lines Nt-GT21 and Nt-GT31. Detection of weakly hybridizing bands of different sizes in most spectionmycin/streptomycin-resistant lines suggests the presence of rearranged nptII sequences that either are only weakly transcribed or have only limited homology to the probe.