RNA Editing of the Mitochondrial atpA/atp9 Co-Transcript of Triticale, Carrying the timopheevi Cytoplasmic Male Sterility Cytoplasm from Wheat

Subunits alpha and nine are components from two different portions of the mt H super(+)-ATP synthase enzyme, namely the soluble catalytic (F sub(1)) and the membranous proton-conduction (F sub(o)-ATPase) complexes. In wheat and triticale the genes for both subunits are located adjacently in the mt genome, irrespective of whether these lines are carrying the aestivum, durum, or timopheevi cytoplasmic male sterility cytoplasm. However, in the timopheevi mt genome the atpA/atp9 cistron is part of a large DNA repeat and thus present in two different genomic environments. The repeat comprises at least 9 kb that are delimited 941 bp downstream of the atp9 gene. The 2.7-kb triticale atpA/atp9 sequence shows 100% homology with a Triticum aestivum sequence, containing both reading frames, the intergenic region, and at least the first 400 bp upstream and the first 46 bp downstream of the atpA/atp9 gene region. Transcription of the atpA/atp9 cistron in triticale gives rise to a co-transcript of 2.6 kb, which is posttranscriptionally modified by 5' processing. To investigate whether further RNA modifications occur, we have analyzed this triticale transcript for RNA editing. To date, editing of an atpA transcript has been described in only two dicotyledonous species.