Reconstruction of the evolutionary history of the LexA-binding sequence
Mazón, Gerard (Universitat Autònoma de Barcelona. Departament de Genètica i de Microbiologia)
Erill, Ivan (Centro Nacional de Microelectrónica (Espanya))
Campoy Sánchez, Susana (Institut de Recerca i Tecnologia Agroalimentàries. Centre de Recerca en Sanitat Animal)
Cortés Garmendia, M. Pilar (Universitat Autònoma de Barcelona. Departament de Genètica i de Microbiologia)
Forano, Evelyne (Institut National de Recherche pour l'Agriculture l'Alimentation et l'Environnement. Centre de Recherches de Clermont-Ferrand-Theix. Unité de Microbiologie)
Barbé García, Jordi (Universitat Autònoma de Barcelona. Departament de Genètica i de Microbiologia)

Date:	2004
Abstract:	In recent years, the recognition sequence of the SOS repressor LexA protein has been identified for several bacterial clades, such as the Gram-positive, green non-sulfur bacteria and Cyanobacteria phyla, or the 'Alphaproteobacteria', 'Deltaproteobacteria' and 'Gammaproteobacteria' classes. Nevertheless, the evolutionary relationship among these sequences and the proteins that recognize them has not been analysed. Fibrobacter succinogenes is an anaerobic Gram-negative bacterium that branched from a common bacterial ancestor immediately before the Proteobacteria phylum. Taking advantage of its intermediate position in the phylogenetic tree, and in an effort to reconstruct the evolutionary history of LexA-binding sequences, the F. succinogenes lexA gene has been isolated and its product purified to identify its DNA recognition motif through electrophoretic mobility assays and footprinting experiments. After comparing the available LexA DNA-binding sequences with the F. succinogenes one, reported here, directed mutagenesis of the F. succinogenes LexA-binding sequence and phylogenetic analyses of LexA proteins have revealed the existence of two independent evolutionary lanes for the LexA recognition motif that emerged from the Gram-positive box: one generating the Cyanobacteria and 'Alphaproteobacteria' LexA-binding sequences, and the other giving rise to the F. succinogenes and Myxococcus xanthus ones, in a transitional step towards the current 'Gammaproteobacteria' LexA box. The contrast between the results reported here and the phylogenetic data available in the literature suggests that, some time after its emergence as a distinct bacterial class, the 'Alphaproteobacteria' lost its vertically received lexA gene, but received later through lateral gene transfer a new lexA gene belonging to either a cyanobacterium or a bacterial species closely related to this phylum. This constitutes the first report based on experimental evidence of lateral gene transfer in the evolution of a gene governing such a complex regulatory network as the bacterial SOS system.
Grants:	Ministerio de Ciencia y Tecnología BMC2001-2065 Agència de Gestió d'Ajuts Universitaris i de Recerca 2001/SGR-206
Rights:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Language:	Anglès
Document:	Article ; recerca ; Versió acceptada per publicar
Subject:	EMSA ; Electrophoresis mobility-shift assay ; GST ; Glutathione S-transferase ; LGT ; Lateral gene transfer
Published in:	Microbiology, Vol. 150, issue 11 (2004) , p. 3783-3795, ISSN 1350-0872

DOI: 10.1099/mic.0.27315-0

Postprint 39 p, 942.5 KB

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