Structural analysis of mature and dicistronic transcripts from the 18 S and 5 S ribosomal RNA genes of maize mitochondria

Abstract

Analysis of the 18 S and 5 S ribosomal RNA transcripts of maize mitochondria is described. The 5' and 3' ends of both mature rRNAs were defined by S1 nuclease protection analysis, which also showed that a small fraction of the total 18 S and 5 S rRNA population resides on common transcripts. The 5' termini of many of these RNAs are upstream from the mature 18 S 5' endpoint. Northern hybridization detected several high molecular weight RNAs that were homologous to the 5 S and 18 S genes and their flanking sequences. Because the two rRNAs share a number of transcripts, we propose that these genes are transcribed as one or more large dicistronic RNAs that are subsequently processed to mature ribosomal RNA molecules. A model for the processing of the large putative precursors is presented.