Figure 3.

Site-specific inactivation of the ndhB gene in the plastid transformants. Gel electrophoresis of SmaI-digested plastid DNA of wild-type tobacco (a) and several plastid transformants (b–d) distinguishes a noninactivated transformant (b) from those possessing the inactivated ndhB gene (c–d). The smaller of the new, inactivation-specific fragments (5.68 and 5.45 kb) comigrates with the unchanged fragment number 9. On the left a HindIII digest of λ DNA is also shown (fragment sizes: 23.13, 9.42, 6.56, 4.36, 2.32, and 2.03 kb). Southern hybridization with a plastid DNA probe spanning the region containing the diagnostic restriction site in the 11.13-kb SmaI fragment number 4 reveals both the site-specificity and homoplasmy of the introduced mutation.