Mitochondrial genomes organization in alloplasmic lines of sunflower (Helianthus annuus L.) with various types of cytoplasmic male sterility.

The observed mitochondrial reorganizations in PET1 resulted in only one new open reading frame formation (orfH522), and PET2 mtDNA rearrangements led to the elimination of orf777, duplication of atp6 gene and appearance of four new ORFs with transcription activity specific for the HA89 (PET2) CMS line-orf645, orf2565, orf228 and orf285. Orf228 and orf285 are the atp9 chimeric ORFs, containing transmembrane domains and possibly may impact on mitochondrial membrane potential. So orf228 and orf285 may be the cause for the appearance of the PET2 CMS phenotype, while the contribution of other mtDNA reorganizations in CMS formation is negligible.