Comparative analysis of the complete mitochondrial genome sequences and anther development cytology between maintainer and Ogura-type cytoplasm male-sterile cabbage (B. oleracea Var. capitata)

Xionghui Zhong,Denghui Chen,Hailong Li,Jian Cui,Yuxin Huang,Jungen Kang

doi:10.1186/s12864-021-07963-x

Xionghui Zhong, Denghui Chen + Show 4 more

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https://doi.org/10.1186/s12864-021-07963-x

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Abstract

BackgroundCytoplasmic 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.ResultsIn 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.ConclusionsThe 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.

Highlights

Cytoplasmic male sterility (CMS) has been widely used for commercial F1 hybrid seeds production
Four orfs from radish were identified in the Ogura CMS mitochondrial genome. orf138a was co-transcribed with atp8 and trnfM
Detection of ATP production in the Ogura CMS cabbage lines From our whole mitochondrial genome data, we found that the orf138a was co-transcribed with atp8, and orf154a has partial homology to the ATP synthase subunit 1 (atpA) gene; we wondered whether the functions of orf138a and orf154a are associated with the yield of ATP

Summary

Introduction

Cytoplasmic male sterility (CMS) has been widely used for commercial F1 hybrid seeds production. CMS is primarily caused by chimeric genes in mitochondrial genomes. CMS is caused by the interaction between the cytoplasm and nuclear genes [1]. The CMS of Brassica oleracea derives from sterile cytoplasm of other cruciferous species, including B. rapa, B. nigra, B. napus and Rahanus sativus. Ogura CMS was discovered from a wild variety of Japanese radish (R. sativus) [3] This radish CMS was first transferred into B. oleracea through distant hybridization and consecutive backcrossing in 1974 [4]. Polima (pol) CMS of B. napus is another well-studied male sterility type, which was transferred into B. oleracea by protoplast fusion [7]. Hau CMS was first identified in B. juncea, and the male sterility was transferred to B. napus by interspecific hybridization [8]. Some novel chimeric open reading frames (ORFs) generated by mitochondrial recombination have been reported as the determinants of CMS

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