Dataset Information

Cohabitation of two different lexA regulons in Pseudomonas putida.

ABSTRACT: In contrast to the vast majority of the members of the domain Bacteria, several Pseudomonas and Xanthomonas species have two lexA genes, whose products have been shown to recognize different LexA binding motifs, making them an interesting target for studying the interplay between cohabiting LexA regulons in a single species. Here we report an analysis of the genetic composition of the two LexA regulons of Pseudomonas putida KT2440 performed with a genomic microarray. The data obtained indicate that one of the two LexA proteins (LexA1) seems to be in control of the conventional Escherichia coli-like SOS response, while the other LexA protein (LexA2) regulates only its own transcriptional unit, which includes the imuA, imuB, and dnaE2 genes, and a gene (PP_3901) from a resident P. putida prophage. Furthermore, PP_3901 is also regulated by LexA1 and is required for DNA damage-mediated induction of several P. putida resident prophage genes. In silico searches suggested that this marked asymmetry in regulon contents also occurs in other Pseudomonas species with two lexA genes, and the implications of this asymmetry in the evolution of the SOS network are discussed.

SUBMITTER: Abella M

PROVIDER: S-EPMC2168638 | biostudies-literature | 2007 Dec

REPOSITORIES: biostudies-literature

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Publications

Cohabitation of two different lexA regulons in Pseudomonas putida.

Abella Marc M Campoy Susana S Erill Ivan I Rojo Fernando F Barbé Jordi J

Journal of bacteriology 20071012 24

In contrast to the vast majority of the members of the domain Bacteria, several Pseudomonas and Xanthomonas species have two lexA genes, whose products have been shown to recognize different LexA binding motifs, making them an interesting target for studying the interplay between cohabiting LexA regulons in a single species. Here we report an analysis of the genetic composition of the two LexA regulons of Pseudomonas putida KT2440 performed with a genomic microarray. The data obtained indicate t ...[more]

PMID: 17933893

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Project description:The transcription factor LexA plays an important role in the SOS response in Escherichia coli and many other bacterial species studied. Although the lexA gene is encoded in almost every bacterial group with a wide range of evolutionary distances, its precise functions in each group/species are largely unknown. More recently, it has been shown that lexA genes in two cyanobacterial genomes Nostoc sp. PCC 7120 and Synechocystis sp. PCC 6803 might have distinct functions other than the regulation of the SOS response. To gain a general understanding of the functions of LexA and its evolution in cyanobacteria, we conducted the current study.Our analysis indicates that six of 33 sequenced cyanobacterial genomes do not harbor a lexA gene although they all encode the key SOS response genes, suggesting that LexA is not an indispensable transcription factor in these cyanobacteria, and that their SOS responses might be regulated by different mechanisms. Our phylogenetic analysis suggests that lexA was lost during the course of evolution in these six cyanobacterial genomes. For the 26 cyanobacterial genomes that encode a lexA gene, we have predicted their LexA-binding sites and regulons using an efficient binding site/regulon prediction algorithm that we developed previously. Our results show that LexA in most of these 26 genomes might still function as the transcriptional regulator of the SOS response genes as seen in E. coli and other organisms. Interestingly, putative LexA-binding sites were also found in some genomes for some key genes involved in a variety of other biological processes including photosynthesis, drug resistance, etc., suggesting that there is crosstalk between the SOS response and these biological processes. In particular, LexA in both Synechocystis sp. PCC6803 and Gloeobacter violaceus PCC7421 has largely diverged from those in other cyanobacteria in the sequence level. It is likely that LexA is no longer a regulator of the SOS response in Synechocystis sp. PCC6803.In most cyanobacterial genomes that we analyzed, LexA appears to function as the transcriptional regulator of the key SOS response genes. There are possible couplings between the SOS response and other biological processes. In some cyanobacteria, LexA has adapted distinct functions, and might no longer be a regulator of the SOS response system. In some other cyanobacteria, lexA appears to have been lost during the course of evolution. The loss of lexA in these genomes might lead to the degradation of its binding sites.

Dataset Information

Cohabitation of two different lexA regulons in Pseudomonas putida.

Publications

Cohabitation of two different lexA regulons in Pseudomonas putida.

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