Fig. 4.

Southern analysis shows cpDNA from the transgenic dcm methylase plant is resistant to ScrFI cleavage at CCWGG sites. a In the absence of methylation, the rbcL probe (LSC) detects a fragment of 797 bp following digestion with ScrFI (WT lane). Protection of CCWGG sites gives a fragment of 1,810 bp (DCM). b Probe chlA was used to assay eight more CCWGG sites within the LSC. In the wild type, ScrFI digestion gives fragments of 505, 461, 360 and 27 bp (not visible). In the Dcm line, two fragments of 874 and 2,738 bp are generated as a result of protection of all eight CCWGG sites. The presence of additional intermediate bands may indicate partial methylation. c Probe chlB (SSC) hybridizes to a single 1,082 bp ScrFI fragment when the two internal CCWGG sites are methylated in the Dcm plant. In the wild type plants, the absence of CCWGG methylation results in fragments of 731, 290 and 61 bp. d Probe chlRD (IR) detects ScrFI fragments of 424, 364, 317, 311 and 161 bp in wild type cpDNA. In the Dcm plant, methylation of all six CCWGG sites results in two hybridizing bands of 583and 2,151 bp. The presence of additional intermediate bands may indicate partial methylation in some DNA molecules