Figure 4.

Homoplasmy of the plastid DNA population in the ndhB-inactivated transformants. Gel electrophoresis of SmaI-digested PCR product of wild-type tobacco (a), two ndhB-inactivated transformants (b and c), and a noninactivated transformant (d). The priming sites were located to cover the 5′ end of ndhB and flank the diagnostic SmaI site. The primer located inside the ndhB gene is outside the targeted plastid DNA region. The primers amplify a product of 966 bp, which is cut into 814- and 152-bp fragments by SmaI if the mutation introduced into ndhB is present. On the left a 100-bp DNA ladder is also shown (fragment sizes: 1,500 and 1,000–100 bp). The complete and correct cleavage of the PCR product in the ndhB-inactivated transformants reveals both the homoplasmy and site-specificity of the introduced mutation.