Origin of the CMS gene locus in rapeseed cybrid mitochondria: Active and inactive recombination produces the complex CMS gene region in the mitochondrial genomes of Brassicaceae

Abstract

CMS (cytoplasmic male sterile) rapeseed is produced by asymmetrical somatic cell fusion between the Brassica napus cv. Westar and the Raphanus sativus Kosena CMS line (Kosena radish). The CMS rapeseed contains a CMS gene, orf125, which is derived from Kosena radish. Our sequence analyses revealed that the orf125 region in CMS rapeseed originated from recombination between the orf125/orfB region and the nad1C/ccmFN1 region by way of a 63 bp repeat. A precise sequence comparison among the related sequences in CMS rapeseed, Kosena radish and normal rapeseed showed that the orf125 region in CMS rapeseed consisted of the Kosena orf125/orfB region and the rapeseed nad1C/ccmFN1 region, even though Kosena radish had both the orf125/orfB region and the nad1C/ccmFN1 region in its mitochondrial genome. We also identified three tandem repeat sequences in the regions surrounding orf125, including a 63 bp repeat, which were involved in several recombination events. Interestingly, differences in the recombination activity for each repeat sequence were observed, even though these sequences were located adjacent to each other in the mitochondrial genome. We report results indicating that recombination events within the mitochondrial genomes are regulated at the level of specific repeat sequences depending on the cellular environment.

Morphological Structure and Transcriptome Comparison of the Cytoplasmic Male Sterility Line in Brassica napus (SaNa-1A) Derived from Somatic Hybridization and Its Maintainer Line SaNa-1B

“…The recombination results in new open reading frames and forms chimeric genes, which affect the function of mitochondria and finally lead to the formation of CMS (Hanson and Bentolila, 2004; Carlsson et al, 2008). Previous studies reported that the mitochondrial structure of kos CMS and tour -Stiewe CMS bred from somatic hybrids differed from that of the CMS lines ( kos and tour CMS) derived from the natural mutation of radish and mustard (Dieterich et al, 2003; Oshima et al, 2010). A sterile line (SaNa-1A) containing 38 chromosomes was previously selected from the BC3 progenies of Brassica napus – Sinapis alba somatic hybrids, using B. napus cv.…”

A Novel Cytoplasmic Male Sterility in Brassica napus (inap CMS) with Carpelloid Stamens via Protoplast Fusion with Chinese Woad

“…In somatic hybrids from protoplast fusion, the chloroplasts are usually inherited from one of the parents, whereas the mitochondrial DNA (mtDNA) is rearranged and may include DNA from both parents (Prakash et al, 1999). Intergenomic mitochondrial recombination with high frequency was found to occur in various somatic hybrids from the combinations of different species within Brassicaceae (Landgren and Glimelius, 1994; Dieterich et al, 2003; Leino et al, 2003; Oshima et al, 2010; Liu et al, 2015), leading to novel CMS genes. In the B. napus CMS Tournefortii-Stiewe produced by protoplast fusion with B. tournefortii (Dieterich et al, 2003), the mitochondrial rearrangement at upstream of the gene atp9 generated a chimeric orf193 that was co-transcribed with atp9 .…”

Complete sequence of heterogenous-composition mitochondrial genome (Brassica napus) and its exogenous source

“…We identified 123 repeats (30–500 bp, similarity ≥ 90%), including both direct and inverted repeats, that were responsible for 6.54% of the genome. The short repeats contributed to genome reorganization and arrangements, although the frequency of these events was not as high [34,35]. We assayed reorganization relationship of some syntenic regions and found that two short repeats were closely related to the rearrangement of five syntenic domains, as elaborated on Figure 5.…”