Sequence and transcription analysis of the Petunia mitochondrial gene for the ATP synthase proteolipid subunit.

We have sequenced the Petunia hybrida gene that specifies the proteolipid subunit of the mitochondrial Fo ATP synthase and have used this gene to investigate plant mitochondrial gene transcription. The Petunia atp 9 gene contains a single open-reading frame capable of specifying a 77 amino acid-polypeptide that is homologous to bovine, fungal and maize proteolipid subunits. S1 protection identified 3 transcripts in a ratio of 1:5:100 in the Petunia tissues tested. The transcripts share a common 3' terminus but have 5' termini that map 528, 266, and 121 nucleotides upstream of the translation start site. The 5' terminus of the longest transcript maps to the sequence ATATAGTA, which is nearly identical to the yeast mitochondrial transcription initiation site ATATAAGTA. Primer extension analysis indicates that these two shorter transcripts are not due to splicing. The two shorter transcripts originate at sequences homologous to sites at 5' termini of two pea and maize genes. These consensus sequences may signal processing events other than splicing.