Viñuelas José, Calevro Federica, Remond Didier, Bernillon Jacques, Rahbé Yvan, Febvay Gérard, Fayard Jean-Michel, Charles Hubert
UMR 203 Biologie Fonctionnelle Insectes et Interactions, IFR41, INRA, INSA-Lyon, Villeurbanne, France.
BMC Genomics. 2007 Jun 4;8:143. doi: 10.1186/1471-2164-8-143.
Genomic studies on bacteria have clearly shown the existence of chromosomal organization as regards, for example, to gene localization, order and orientation. Moreover, transcriptomic analyses have demonstrated that, in free-living bacteria, gene transcription levels and chromosomal organization are mutually influenced. We have explored the possible conservation of relationships between mRNA abundances and chromosomal organization in the highly reduced genome of Buchnera aphidicola, the primary endosymbiont of the aphids, and a close relative to Escherichia coli.
Using an oligonucleotide-based microarray, we normalized the transcriptomic data by genomic DNA signals in order to have access to inter-gene comparison data. Our analysis showed that mRNA abundances, gene organization (operon) and gene essentiality are correlated in Buchnera (i.e., the most expressed genes are essential genes organized in operons) whereas no link between mRNA abundances and gene strand bias was found. The effect of Buchnera genome evolution on gene expression levels has also been analysed in order to assess the constraints imposed by the obligate symbiosis with aphids, underlining the importance of some gene sets for the survival of the two partners. Finally, our results show the existence of spatial periodic transcriptional patterns in the genome of Buchnera.
Despite an important reduction in its genome size and an apparent decay of its capacity for regulating transcription, this work reveals a significant correlation between mRNA abundances and chromosomal organization of the aphid-symbiont Buchnera.
对细菌的基因组研究清楚地表明，在基因定位、顺序和方向等方面存在染色体组织。此外，转录组分析表明，在自由生活的细菌中，基因转录水平和染色体组织相互影响。我们探索了蚜虫的主要内共生体——蚜虫内共生菌（Buchnera aphidicola）高度简化的基因组中，mRNA丰度与染色体组织之间关系的可能保守性，蚜虫内共生菌与大肠杆菌亲缘关系较近。
我们使用基于寡核苷酸的微阵列，通过基因组DNA信号对转录组数据进行标准化，以便获得基因间比较数据。我们的分析表明，在蚜虫内共生菌中，mRNA丰度、基因组织（操纵子）和基因必需性是相关的（即表达量最高的基因是组织成操纵子的必需基因），而未发现mRNA丰度与基因链偏向之间存在联系。我们还分析了蚜虫内共生菌基因组进化对基因表达水平的影响，以评估与蚜虫专性共生所施加的限制，强调了某些基因集对这两个共生伙伴生存的重要性。最后，我们的结果表明蚜虫内共生菌的基因组中存在空间周期性转录模式。
尽管其基因组大小显著减小，转录调控能力明显衰退，但这项研究揭示了蚜虫共生菌蚜虫内共生菌的mRNA丰度与染色体组织之间存在显著相关性。
