title: Global transcriptional response to salt shock of the plant microsymbiont Mesorhizobium loti MAFF303099.
abstract: Soil salinity affects rhizobia both as free-living bacteria and in symbiosis with the host. The aim of this study was to examine the transcriptional response of the Lotus microsymbiont Mesorhizobium loti MAFF303099 to salt shock. Changes in the transcriptome of bacterial cells subjected to a salt shock of 10% NaCl for 30 min were analyzed. From a total of 7231 protein-coding genes, 385 were found to be differentially expressed upon salt shock, among which 272 were overexpressed. Although a large number of overexpressed genes encode hypothetical proteins, the two most frequently represented COG categories are "defense mechanisms" and "nucleotide transport and metabolism". A significant number of transcriptional regulators and ABC transporters genes were upregulated. Chemotaxis and motility genes were not differentially expressed. Moreover, most genes previously reported to be involved in salt tolerance were not differentially expressed. The transcriptional response to salt shock of a rhizobium with low ability to grow under salinity conditions, but enduring a salinity shock, may enlighten us concerning salinity stress response mechanisms.
authors.affiliation: Instituto de Ciências Agrárias e Ambientais Mediterrânicas (ICAAM), Instituto de Investigação e Formação Avançada (IIFA), Universidade de Évora, Ap. 94, 7002-554 Évora, Portugal.
authors.forename: Marta
authors.initials: M
authors.lastname: Laranjo
authors.affiliation: Instituto de Ciências Agrárias e Ambientais Mediterrânicas (ICAAM), Instituto de Investigação e Formação Avançada (IIFA), Universidade de Évora, Ap. 94, 7002-554 Évora, Portugal.
authors.forename: Ana
authors.initials: A
authors.lastname: Alexandre
authors.affiliation: Instituto de Ciências Agrárias e Ambientais Mediterrânicas (ICAAM), Instituto de Investigação e Formação Avançada (IIFA), Universidade de Évora, Ap. 94, 7002-554 Évora, Portugal; Departamento de Biologia, Escola de Ciências e Tecnologia, Universidade de Évora, Polo da Mitra, Ap. 94, 7002-554 Évora, Portugal. Electronic address: ismo@uevora.pt.
authors.forename: Solange
authors.initials: S
authors.lastname: Oliveira
mesh_terms: D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D000070116:Lotus / Q000382:microbiology; D059128:Mesorhizobium / Q000187:drug effects* / Q000235:genetics / Q000502:physiology*; D009997:Osmotic Pressure; D012965:Sodium Chloride / Q000378:metabolism*; D013312:Stress, Physiological
chemical_list: D012965:Sodium Chloride
keywords: Microarray; Osmotic stress; Rhizobia; Salt; Transcriptome