Cytoplasmic male sterility (CMS) has been widely used for commercial F1 hybrid seeds production. CMS is primarily caused by chimeric genes in mitochondrial genomes. However, which specific stages of anther development in cabbage are affected by the chimeric genes remain unclear. In the present study, the complete mitochondrial genomes were sequenced and assembled for the maintainer and Ogura CMS cabbage lines. The genome size of the maintainer and Ogura CMS cabbage are 219,962 bp and 236,648 bp, respectively. There are 67 and 69 unknown function ORFs identified in the maintainer and Ogura CMS cabbage mitochondrial genomes, respectively. Four orfs, orf102a, orf122b, orf138a and orf154a were specifically identified in the Ogura CMS mitochondrial genome, which were likely generated by recombination with Ogura type radish during breeding process. Among them, ORF138a and ORF154a possessed a transmembrane structure, and orf138a was co-transcribed with the atp8 and trnfM genes. orf154a is partially homologous to the ATP synthase subunit 1 (atpA) gene. Both these genes were likely responsible for the CMS phenotype. In addition, cytological sections showed that the abnormal proliferation of tapetal cells might be the immediate cause of cytoplasmic male-sterility in Ogura CMS cabbage lines. RNA-seq results showed that orf138a and orf154a in Ogura CMS might influence transcript levels of genes in energy metabolic pathways. The presence of orf138a and orf154a lead to increased of ATPase activity and ATP content by affecting the transcript levels of genes in energy metabolic pathways, which could provide more energy for the abnormal proliferation of tapetal cells. Our data provides new insights into cytoplasmic male-sterility from whole mitochondrial genomes, cytology of anther development and transcriptome data.

中文翻译：

---

保持系与小仓型细胞质雄性不育甘蓝（B. oleracea Var. capitalata）线粒体全基因组序列及花药发育细胞学比较分析

细胞质雄性不育 (CMS) 已广泛用于商业 F1 杂交种子生产。CMS 主要由线粒体基因组中的嵌合基因引起。然而，甘蓝花药发育的哪些特定阶段受嵌合基因影响尚不清楚。在本研究中，对保持系和 Ogura CMS 甘蓝系的完整线粒体基因组进行了测序和组装。保持系和 Ogura CMS 甘蓝的基因组大小分别为 219,962 bp 和 236,648 bp。在保持者和 Ogura CMS 甘蓝线粒体基因组中分别鉴定了 67 和 69 个未知功能的 ORF。在 Ogura CMS 线粒体基因组中特异性鉴定了四个 orf，orf102a、orf122b、orf138a 和 orf154a，它们可能是在育种过程中与 Ogura 型萝卜重组产生的。其中，ORF138a和ORF154a具有跨膜结构，orf138a与atp8和trnfM基因共转录。orf154a 与 ATP 合酶亚基 1 (atpA) 基因部分同源。这两个基因都可能导致 CMS 表型。此外，细胞学切片显示，绒毡层细胞的异常增殖可能是小仓CMS甘蓝品系细胞质雄性不育的直接原因。RNA-seq 结果表明 Ogura CMS 中的 orf138a 和 orf154a 可能影响能量代谢途径中基因的转录水平。orf138a和orf154a的存在通过影响能量代谢途径中基因的转录水平导致ATP酶活性和ATP含量增加，从而为绒毡层细胞的异常增殖提供更多能量。