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BACKGROUND

Nsa cytoplasmic male sterility (CMS) is a novel alloplasmic male sterility system derived from somatic hybridization between Brassica napus and Sinapis arvensis. Identification of the CMS-associated gene is a prerequisite for a better understanding of the origin and molecular mechanism of this CMS. With the development of genome sequencing technology, organelle genomes of Nsa CMS line and its maintainer line were sequenced by pyro-sequencing technology, and comparative analysis of the organelle genomes was carried out to characterize the organelle genome composition of Nsa CMS as well as to identify the candidate Nsa CMS-associated genes.

RESULTS

Nsa CMS mitochondrial genome showed a higher collinearity with that of S. arvensis than B. napus, indicating that Nsa CMS mitochondrial genome was mainly derived from S. arvensis. However, mitochondrial genome recombination of parental lines was clearly detected. In contrast, the chloroplast genome of Nsa CMS was highly collinear with its B. napus parent, without any evidence of recombination of the two parental chloroplast genomes or integration from S. arvensis. There were 16 open reading frames (ORFs) specifically existed in Nsa CMS mitochondrial genome, which could not be identified in the maintainer line. Among them, three ORFs (orf224, orf309, orf346) possessing chimeric and transmembrane structure are most likely to be the candidate CMS genes. Sequences of all three candidate CMS genes in Nsa CMS line were found to be 100% identical with those from S. arvensis mitochondrial genome. Phylogenetic and homologous analysis showed that all the mitochondrial genes were highly conserved during evolution.

CONCLUSIONS

Nsa CMS contains a recombined mitochondrial genome of its two parental species with the majority form S. arvensis. Three candidate Nsa CMS genes were identified and proven to be derived from S. arvensis other than recombination of its two parental species. Further functional study of the candidate genes will help to identify the gene responsible for the CMS and the underlying molecular mechanism.

BACKGROUND

RESULTS

CONCLUSIONS

背景

Nsa细胞质雄性不育（CMS）是一种新型的异质细胞质雄性不育系统，源于甘蓝型油菜和野芥菜的体细胞杂交。鉴定与CMS相关的基因是更好地理解该CMS起源和分子机制的前提。随着基因组测序技术的发展，利用焦磷酸测序技术对Nsa CMS系及其保持系的细胞器基因组进行了测序，并对细胞器基因组进行了比较分析，以表征Nsa CMS的细胞器基因组组成，并鉴定候选的Nsa CMS相关基因。

结果

Nsa CMS线粒体基因组与野芥菜的线粒体基因组的共线性高于与甘蓝型油菜的共线性，表明Nsa CMS线粒体基因组主要来源于野芥菜。然而，明显检测到亲本系的线粒体基因组重组。相比之下，Nsa CMS的叶绿体基因组与其甘蓝型油菜亲本高度共线，没有任何两个亲本叶绿体基因组重组或来自野芥菜整合的证据。Nsa CMS线粒体基因组中存在16个开放阅读框（ORF），在保持系中未鉴定到。其中，三个具有嵌合和跨膜结构的ORF（orf224、orf309、orf346）最有可能是候选CMS基因。发现Nsa CMS系中所有三个候选CMS基因的序列与野芥菜线粒体基因组的序列100%相同。系统发育和同源分析表明，所有线粒体基因在进化过程中高度保守。