TRANSCRIPTION OF POTATO MITOCHONDRIAL 26S-RIBOSOMAL RNA IS INITIATED AT ITS MATURE 5' END

Transcription initiation sites in plant mitochondria can be located by in vitro capping of primary 5' transcript termini. Direct sequencing of a cap-labelled mitochondrial RNA from potato shows its sequence to be identical to the 5' terminal part of the 26S rRNA. Primer extension analysis indicates the mature 5' end to be the sole detectable 5' tra nscript terminus. In potato mitochondria the mature 5' end of the 26S rRNA is thus created by transcription initiation without any further 5 ' processing. The nucleotide sequence surrounding this transcription i nitiation site shows only limited similarity to other putative promote r sequences from dicot plant mitochondria suggesting the possibility t hat divergent RNA polymerases, and/or transcription initiation factors , are present in plant mitochondria.