Cotranscription of the rpl5-rps14-cob gene cluster in pea mitochondria

In pea mitochondria the rpl5, rpsl4 and cob ORFs are clustered in a unique genomic environment and are cotranscribed into a 4.7-kb primary transcript and several other polycistronic RNAs with sizes between 4.0 and 2.3 kb. All of the larger RNAs terminate at a common 3' end, 52 nucleotides downstream of the cob gene. Transcription is initiated at a promoter about 1.3 kb ups tream of the rpl5 start codon. The promoter sequence 5'-AATAAGAGA-3' corres ponds to the highly conserved 5'-CRTAAGAGA-3' motif often found in promoter s in dicot plants. Functional analysis in a homologous in vitro transcripti on system showed the pea rpl5 promoter to be active, despite the presence o f an altered base in first position of the promoter motif. In Oenothera, in contrast to pea, transcription of the rpl5 gene is driven by a promoter mo tif that conforms perfectly to the consensus sequence. Double inverted repe ats located in the 3' flanking regions of the rpsl4 and cob ORFs in pea wer e investigated with respect to their possible role in defining transcript t ermini and their potential function in controlling exo- and endonucleolytic processing or transcript stabilization.