Physical map of chloroplast DNA of Spirodela oligorrhiza; analysis by the restriction endonucleases PstI, xhoI, SacI.

Using the restriction endonucleases XhoI, SacI and PstI, physical maps of Spirodela oligorrhiza (duck weed) chloroplast DNA [with a relatively large m. wt. of 120 Md; see van Ee et al. (1980)] were constructed. The overall structural organization of S. oligorrhiza chloroplast DNA appears to be rather similar to that of chloroplast DNAs of other higher plants. It is composed of two invertedly repeated DNA segments of 17 Md, separated by a small single-copy region of 19 Md and a large single-copy region of 69 Md. Apparently the extra DNA (as compared with chloroplast DNAs of other higher plants) is present within the large single-copy region.