关键词: 玉米, C型细胞质雄性不育, 转录组, 差异表达基因, 调控网络

Abstract:

【Objective】It is one of the most efficient ways to utilize cytoplasmic male sterile (CMS) lines in hybrid seed production, which could improve the purity of seeds, reduce the cost in creating hybrid seeds and enhance the competitiveness of Chinese seed companies. The comparative transcriptome analysis of the anthers at different development stages from the CMS line, the maintainer line and the restorer line (the three lines) were performed in order to understand the mechanism of sterility and restoration of CMS-C in maize, and also to elucidate the regulation network between the restorer gene and the sterile gene, which will provide the fundamental basis for the employment of maize CMS in hybrid seed production.【Method】The transcriptome sequencing was carried out on the anthers at the prophaseⅠ, the metaphaseⅠand the tetrad stage from the three lines based on the elite inbred line Yu87-1. Method of comparative analysis was used to deal with all the transcripts by the tools such as hisat2, ballgown and DESeq2, and to predict genes involved in the regulation network between the sterile gene and the restorer gene, between the different development stages and through the development time series. qRT-PCR was used to verify the differentially expressed genes. The activity of ATPase was quantified with by the spectrophotometric method for the verification of the putative hypothesis.【Result】Transcriptome sequencing totally produced 156.59 Gb sequence data. After mapping and assembling, 53035 Unigenes were obtained. A total of 5676 differentially expressed (DE) genes were identified from the pairwise comparisons (except for comparisons between the restorer lines and the maintainer lines) in the anthers at the different stages from the three lines. Of those, 4705 DE genes between the comparisons of the development stages, 2693 DE genes between the comparisons of the different lines and 135 DE genes related to the time series. The GO molecular functional analysis showed that the genes related to ATP binding, DNA binding and zinc ion binding were highly enriched, in cell component analysis, genes located in integral component of membrane, nucleus and plasma membrane were enriched, and in biological process, genes involved in DNA-templated transcription, regulation of transcription, oxidation-reduction process and primary metabolic process were enriched. KEGG pathway analysis indicated that the oxidative phosphorylation pathways, the carbon metabolism pathways and glycolysis pathways were mostly enriched. Compared to the maintainer lines, several genes involving in the oxidative phosphorylation pathways were significantly down-regulated in the sterile lines, while those down-regulated genes were recovered, besides other genes in the same pathways were also coordinately regulated. The expression trend determined by qRT-PCR on the selected DE genes was in accordance with that in the transcriptome data. The enzyme activity results show that the activity of ATPase in the sterile line was greatly reduced compared to the maintainer line, while in the restorer line, the activities the ATPase were restored due to the existence of the restorer gene.【Conclusion】 The onset of the changes in the gene expression caused by the sterile gene in the anthers of CMS-C maize may happen after metaphaseⅠ and before telophase Ⅱ in meiosis before visible phenotype occurred. The energy deficiency model may account for the mechanism of the sterility in maize CMS-C, and the energy requirements were compensated by the restorer gene through direct or indirect manner.

Key words: Zea mays, cytoplasmic male sterility, transcriptome, differentially expressed gene, regulation network