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.

Kun Du,Youping Wang,Yujie Fang,Jian Wu,Aimin Li,Xinyue Wu,Qier Liu,Jinjin Jiang

doi:10.3389/fpls.2016.01313

Kun Du, Youping Wang + Show 6 more

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https://doi.org/10.3389/fpls.2016.01313

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Abstract

SaNa-1A is a novel cytoplasmic male sterility (CMS) line in Brassica napus derived from progenies of somatic hybrids between B.napus and Sinapis alba, and SaNa-1B is the corresponding maintainer line. In this study, phenotypic differences of floral organs between CMS and the maintainer lines were observed. By microscope observation in different anther developmental stages of two lines, we found the anther development in SaNa-1A was abnormal since the tetrad stage, and microspore development was ceased during the uninucleate stage. Transcriptomic sequencing for floral buds of sterile and fertile plants were conducted to elucidate gene expression and regulation caused by the alien chromosome and cytoplasm from S. alba. Clean tags obtained were assembled into 195,568 unigenes, and 7811 unigenes distributed in the metabolic and protein synthesis pathways were identified with significant expression differences between two libraries. We also observed that genes participating in carbon metabolism, tricarboxylic acid cycle, oxidative phosphorylation, oxidation–reduction system, pentatricopeptide repeat, and anther development were downregulated in the sterile line. Some of them are candidates for researches on the sterility mechanism in the CMS material, fertility restoration, and improvement of economic traits in the maintainer line. Further research on the tags with expressional specificity in the fertile line would be helpful to explore desirable agronomic traits from wild species of rapeseed.

Highlights

Heterosis is important to improve rapeseed yield, and cytoplasmic male sterility (CMS), as one of the ideal systems for pollination control, has significantly contributed to increase rapeseed production
We identified 11 differentially expressed genes (DEGs) related to the electron transport chain and oxidative phosphorylation, which were downregulated in the sterile line compared with the fertile line
We compared the transcriptome data between floral buds of the sterile and fertile lines in rapeseed using high-throughput transcriptomic sequencing

Summary

Introduction

Heterosis is important to improve rapeseed yield, and cytoplasmic male sterility (CMS), as one of the ideal systems for pollination control, has significantly contributed to increase rapeseed production. According to the origin of the cytoplasm, CMS in rapeseed was classified into two types (Yamagishi and Bhat, 2014). 70% of the rapeseed hybrids in China were bred using CMS lines as a pollination control system, of which pol CMS and Shan2A CMS were extensively used (Shen et al, 2008). The second type was obtained by nucleus substitution or mitochondrial gene recombination during wide hybridization or protoplast fusion between different species, including Ogura/kos CMS and tour CMS (Leino et al, 2003). The mitochondrial genome of pol CMS contains a causal gene named orf224, a chimeric gene located at upstream of and co-transcribed with the atp gene. In the presence of Rf gene, processing of orf224/atp is affected and the transcripts are altered (L’Homme and Brown, 1993)

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