Size and physical organization of chloroplast DNA from mustard (Sinapis alba L.)

Summary Intact chloroplast (cp)DNA from mustard cotyledons (Sinapis alba L.) was found by electron microscopy to be a uniform population of circular molecules with a contour length corresponding to 158 kilobase pairs. This size was confirmed by restriction endonuclease analysis. Nucleases SalI and XhoI each generate a small number of cpDNA fragments. The sizes of all fragments generated by each enzyme sum up to more than 150 kilobase pairs. Overlaps of SalI and XhoI fragments were determined by double digestion and triple digestion including SmaI. A physical map of mustard cpDNA with reference to all recognition sites for SalI and most sites for XhoI is presented. This map indicates that an inverted repeated sequence covers approximately 30% of the molecule and is interrupted by two unique sequence regions of different sizes.