The chloroplast genomes of conifers lack one of the rRNA-encoding inverted repeats

Chloroplast DNA from species of five different conifer genera was extracted and studied by Southern blot analysis. For all these species, hybridization with heterologous probes specific for 16 S and 23 S rDNA detected only one chloroplast DNA fragment per enzyme digest. This observation suggests that the 16 S and 23 S rRNA genes are not duplicated in these genomes. The unique 16 S rDNA-containing BamHI fragment from Pinus contorta Dougl. was cloned and restriction mapped. Apart from the 16 S rRNA gene, this fragment also contained the psbC and psbD genes. It is concluded that the chloroplast genomes of a wide taxonomic range of conifers lack one of the inverted repeat elements and that a dislocation of the psbDC gene cluster has occurred in P. contorta.