摘要
【目的】通过分析玉米C型胞质雄性不育"三系"材料花药不同发育时期的转录组数据,以期阐明玉米C型胞质的不育和恢复机制,并解析不育基因与恢复基因之间相互作用的调控网络,为玉米C型细胞质雄性不育在不育化制种中的利用提供理论依据。【方法】以中国玉米生产上的骨干自交系豫自87-1为背景的C型胞质不育系、保持系、恢复系为材料,通过对3种材料减数分裂的前期Ⅰ、中期Ⅰ及末期Ⅱ(四分体)时期的花药进行转录组测序并利用hisat2、ballgown及DESeq2等工具进行生物信息学分析,寻找三系花药不同时期、相同时期不同材料间以及发育时序中差异表达的基因,预测C型胞质不育机制与育性恢复的调控网络;同时通过实时定量PCR对测序分析结果进行验证;通过酶活测定验证推测的C型胞质不育及恢复假说。【结果】所有材料的转录组测序共产生156.59 Gb的序列数据,比对并组装共得到53 035个基因;在恢复系与不育系、保持系与不育系以及"三系"花药不同时期之间共筛选出非重复差异基因5 676个,其中发育阶段差异基因4 705个,同时期材料间差异基因2 693个,发育时序差异基因135个。GO分子功能分析显示ATP和DNA结合相关的基因和锌离子结合基因得到高度富集;细胞组分中膜基本组分、核内及质膜内的基因得到富集;以DNA为模板的转录、转录调控、氧化还原及初级代谢等生物学过程中的基因得到富集。KEGG分析表明,差异基因主要富集于氧化磷酸化、碳代谢及糖酵解等能量代谢相关的途径中。不育系相对保持系而言,多个与氧化磷酸化相关的基因下调表达,而恢复系中不但相应基因的表达水平得到恢复,而且同时协调调节了同一能量代谢途径中的其他基因,定量分析显示差异基因的表达差异及趋势与转录组测序结果基本一致。ATP酶活结果表明不育系相比保持系,ATP酶活显著降低,恢复系中由于恢复基因的作用其活性得到大幅恢复。【结论】玉米C型胞质不育基因引起基因表达变化可能发生在减数分裂中期Ⅰ之后,末期Ⅱ之前;玉米C型胞质不育的形成可能是由于不育基因引起的能量亏损所致,而恢复基因则通过能量补偿促使育性得以恢复。
【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.
引文
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