A new rearrangement of angiosperm chloroplast DNA in rye (Secale cereale) involving translocation and duplication of the ribosomal rpS15 gene.

The mapping and nucleotide sequencing of the rpS15 gene in the rye chloroplast DNA has shown that it is located in the inverted repeat (IR) and thus has two copies/genome. This is in contrast to tobacco and liverwort chloroplasts where rpS15 occurs as single-copy gene localized in the small single copy region (SSC). The direction of transcription of both gene copies in rye is toward SSC; that in tobacco and liverwort is toward IR-II. Further sequence data have revealed that the 3' end of each rye rpS15 gene copy is only 352 base pairs away from the corresponding IR.SSC junction and that this rearrangement event in rye involves also a 3' downstream-encoded and highly conserved chloroplast gene designated ORF393 in tobacco and ORF392 in liverwort. The latter in rye starts in both the IRs, but continues to full length into the SSC only from the IR-II. The direction of transcription of the nontruncated gene is fixed toward IR-I, being thus the inverse of ORF393/392 in tobacco and liverwort. Northern blot analysis has shown that the rearranged rpS15 gene is actively transcribed in rye chloroplasts and etioplasts and that its transcription pattern is different from that recently reported for tobacco rpS15.