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Open Access Research article

Conservation of the links between gene transcription and chromosomal organization in the highly reduced genome of Buchnera aphidicola

José Viñuelas1*, Federica Calevro1, Didier Remond2, Jacques Bernillon3, Yvan Rahbé1, Gérard Febvay1, Jean-Michel Fayard1 and Hubert Charles1

Author Affiliations

1 UMR 203 Biologie Fonctionnelle Insectes et Interactions, IFR41, INRA, INSA-Lyon, F-69621 Villeurbanne, France

2 Laboratoire de Dynamique des Machines et des Structures, INSA-Lyon, F-69621 Villeurbanne, France

3 DTAMB, Université Claude Bernard Lyon-1, F-69622 Villeurbanne, France

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BMC Genomics 2007, 8:143  doi:10.1186/1471-2164-8-143

Published: 4 June 2007

Abstract

Background

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.

Results

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.

Conclusion

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.