Abstract
BackgroundNsa 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.ResultsNsa 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.ConclusionsNsa 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.
Highlights
Nsa cytoplasmic male sterility (CMS) is a novel alloplasmic male sterility system derived from somatic hybridization between Brassica napus and Sinapis arvensis
Interspecific or intergeneric hybridization has been proven efficient for the establishment of alloplasmic CMS in crops via either sexual or somatic hybridization, such as Ogu CMS derived from intergeneric hybridization of Raphanus sativus and Brassica napus [10], and Tour CMS from sexual hybridization of Brassica juncea and Brassica tournefortii [11]
PCR amplification of contig ends showed that there was no missing base between the contigs, and the break between contigs was caused by inverted repeat (IR) sequence
Summary
Nsa cytoplasmic male sterility (CMS) is a novel alloplasmic male sterility system derived from somatic hybridization between Brassica napus and Sinapis arvensis. 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. The composition of organelle genomes at whole genome level of a cybrid-derived alloplasmic CMS and the origin of its sterility gene have not been completely elucidated. The most common method to identify the CMS-associated gene is to compare the differences of mitochondrial genes between the male sterile line and its maintainer lines at genomic, transcriptional and proteomic levels. Orf288 as a specific novel chimeric ORF was identified to be Hau CMS candidate gene in B. juncea by comparison of genomic sequence and gene expression between the CMS line and its maintainer line using genome walking and Northern-blot analysis [19]. Other CMS genes, such as orf138 of Ogu CMS in B. napus [21], orf522 in sunflower CMS [22], urf of CMS-T in maize [23] were detected by comparing the translated proteins in the CMS and fertile lines
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
