Localization and expression of the closely linked cyanelle genes for RNase P RNA and two transfer RNAs.

The genomic region encoding the RNA subunit of the cyanelle RNase P has been characterized. rnpB, which has no homologue in chloroplasts, is flanked by two tRNA genes on the complementary DNA strand. Transcriptional control elements of all three genes have been experimentally determined. Comparison of the sequenced region with the corresponding loci of chloroplast genomes from vascular plants suggests that major inversions may have led to a possible loss or severe truncation of the RNase P RNA coding region during the course of plastid evolution.