title: A role for Bradyrhizobium japonicum ECF16 sigma factor EcfS in the formation of a functional symbiosis with soybean.
abstract: Alternative sigma (σ) factors, proteins that recruit RNA polymerase core enzyme to target promoters, are one mechanism by which bacteria transcriptionally regulate groups of genes in response to environmental stimuli. A class of σ(70) proteins, termed extracytoplasmic function (ECF) σ factors, are involved in cellular processes such as bacterial stress responses and virulence. Here, we describe an ECF16 σ factor, EcfS (Blr4928) from the gram-negative soil bacterium Bradyrhizobium japonicum USDA110, that plays a critical role in the establishment of a functional symbiosis with soybean. Nonpolar insertional mutants of ecfS form immature nodules that do not fix nitrogen, a defect that can be successfully complemented by expression of ecfS. Overexpression of the cocistronic gene, tmrS (blr4929), phenocopies the ecfS mutant in planta and, therefore, we propose that TmrS is a negative regulator of EcfS, a determination consistent with the prediction that it encodes an anti-σ factor. Microarray analysis of the ecfS mutant and tmrS overexpressor was used to identify 40 transcripts misregulated in both strains. These transcripts primarily encode proteins of unknown and transport-related functions and may provide insights into the symbiotic defect in these strains.
authors: Biological Sciences Department, Dartmouth College, Hanover, NH, USA. stockwsb@jmu.edu
authors: S B
authors: SB
authors: Stockwell
authors: L
authors: L
authors: Reutimann
authors: M L
authors: ML
authors: Guerinot
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D020369:Bradyrhizobium / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D018076:DNA, Complementary / Q000235:genetics; D015870:Gene Expression / Q000235:genetics; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D005798:Genes, Bacterial / Q000235:genetics; D005816:Genetic Complementation Test; D016254:Mutagenesis, Insertional; D009586:Nitrogen Fixation; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D018515:Plant Leaves / Q000382:microbiology; D012329:RNA, Bacterial / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D053204:Root Nodules, Plant / Q000382:microbiology / Q000648:ultrastructure; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D013025:Glycine max / Q000382:microbiology* / Q000648:ultrastructure; D013312:Stress, Physiological; D013559:Symbiosis; D014158:Transcription, Genetic; D059467:Transcriptome
chemical_list: D001426:Bacterial Proteins; D018076:DNA, Complementary; D012329:RNA, Bacterial; D012333:RNA, Messenger; D012808:Sigma Factor