Background. Cytoplasmic male sterility (CMS) is a common phenotype in higher plants, which often is associated with rearrangements in mitochondrial DNA (mtDNA), and is widely used to produce hybrid seeds in a variety of valuable crop species. The CMS phenomenon investigations are also promote understanding of a fundamental issue of nuclear-cytoplasmic interactions in the ontogeny of higher plants. In the present study, we analyzed the structural changes in mitochondrial genomes of three alloplasmic lines of sunflower (Helianthus annuus). The investigation was focused on CMS line PET2, as there are very few reports about its mtDNA organization.
Methods. The NGS sequencing, de novo assembly, and annotation of sunflower mitochondrial genomes were performed. The comparative analysis of mtDNA of HA89 fertile line and two HA89 CMS lines (PET1, PET2) occurred.
Results. The mtDNA of the HA89 fertile line was almost identical to the HA412 line (NC_023337). The comparative analysis of HA89 fertile and CMS (PET1) analog mitochondrial genomes revealed 11852 bp inversion, 4732 bp insertion, and 18 variant sites. In mtDNA of HA89 (PET2) CMS line 5050 bp and 5.9 kb insertions, as well as 0.95 kb and 3.8 kb deletions, were determined. There are also revealed 83 polymorphic sites in the PET2 mitochondrial genome, as compared with the fertile line.
Discussion. Among the revealed rearrangements the 5.9 kb insertion results in putative orf1053 – coxI-atp6 chimeric protein, which could be the main reason for CMS phenotype development, whereas the role of other mtDNA reorganizations in CMS formation is negligible.