The rps4 gene in sugar beet mitochondria: insertion/deletion mutations occur within the gene but do not disrupt the reading frame

We have characterized a sugar beet mitochondrial gene, rps4, which is co-transcribed with the downstream gene nad6. The sugar beet RPS4 polypeptide has two deletions of 8 and 49 amino acid residues and a duplication of 14 residues in the middle of the reading frame, relative to the rapeseed and rice homologues. Nevertheless, transcripts of the rps4 were observed to be edited at 10 nucleotides, suggesting that the sugar beet rps4 is functional. Western blot analysis identified the translation product of 33 kDa. The extensive rearrangements in rps4 were also found in spinach but not in pea, green pepper and rose.