Mitochondrial RNA editing is sequence specific and independent of transcript abundance in Sorghum bicolor

The DNA sequence which encodes the amino-terminal extension to the conserved core of the atp6-1 gene found in line IS1112C is absent from Tx398. Sequences further upstream are present in Tx398, but at a different genomic location. The atp6-2 genes are present in similar copy numbers in IS1112C and A3Tx398, a near-isogenic line carrying the IS1112C cytoplasm in a Tx398 background. However, transcript abundance of atp6-2 in these lines is about ten-times higher than that of atp6-1. RNA editing of atp6-1 transcripts is identical to that of atp6-2 and therefore sequence specific. A single non-silent editing site in the unique atp6-1 pre-piece sequence may indicate mitochondrial-guided RNA editing. While in Petunia the abundance and RNA editing of a transcript are correlated, we show here that RNA editing is independent of transcript abundance and is sequence specific in Sorghum.