Characterization of soybean chloroplast ribosomal RNA genes.

Soybean chloroplast (cp) ribosomal RNA genes were located by hybridizing labeled homologous probes to filter bound cpDNA fragments. The soybean chloroplast chromosome, like those of most other plants, contains duplicate sets of ribosomal genes arranged in an inverted orientation. The inverted repeated regions are separated by two single copy regions of 21 and 116 kilobasepairs (kb). Cloned rDNA was mapped with numerous restriction endonucleases. This detailed study shows that the ribosomal genes are arranged in the sequence 5' -16S - Spacer - 23S - 3', and that both 16S and 23S rRNAs are transcribed from the same strand of DNA. Quantitative comparison of rDNA sequence divergence between soybean and tobacco indicates that the highest degree of divergence is in the spacer region, possibly due to an insertion/deletion.