title: Genome-wide transcript analysis of Bradyrhizobium japonicum bacteroids in soybean root nodules.
abstract: The transcriptome of endosymbiotic Bradyrhizobium japonicum bacteroids was assessed, using RNA extracted from determinate soybean root nodules. Results were compared with the transcript profiles of B. japonicum cells grown in either aerobic or microaerobic culture. Microoxia is a known trigger for the induction of symbiotically relevant genes. In fact, one third of the genes induced in bacteroids at day 21 after inoculation are congruent with those up-regulated in culture by a decreased oxygen concentration. The other induced genes, however, may be regulated by cues other than oxygen limitation. Both groups of genes provide a rich source for the possible discovery of novel functions related to symbiosis. Samples taken at different timepoints in nodule development have led to the distinction of genes expressed early and late in bacteroids. The experimental approach applied here is also useful for B. japonicum mutant analyses. As an example, we compared the transcriptome of wild-type bacteroids with that of bacteroids formed by a mutant defective in the RNA polymerase transcription factor sigma54. This led to a collection of hitherto unrecognized B. japonicum genes potentially transcribed in planta in a sigma54-dependent manner.
authors.affiliation: Institute of Microbiology, Eidgenössische Technische Hochschule, CH-8093 Zürich, Switzerland. pessi@micro.biol.ethz.ch
authors.forename: Gabriella
authors.initials: G
authors.lastname: Pessi
authors.forename: Christian H
authors.initials: CH
authors.lastname: Ahrens
authors.forename: Hubert
authors.initials: H
authors.lastname: Rehrauer
authors.forename: Andrea
authors.initials: A
authors.lastname: Lindemann
authors.forename: Felix
authors.initials: F
authors.lastname: Hauser
authors.forename: Hans-Martin
authors.initials: HM
authors.lastname: Fischer
authors.forename: Hauke
authors.initials: H
authors.lastname: Hennecke
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D020369:Bradyrhizobium / Q000235:genetics*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D016680:Genome, Bacterial; D040081:Protein Array Analysis; D012329:RNA, Bacterial / Q000032:analysis / Q000235:genetics; D053204:Root Nodules, Plant / Q000382:microbiology*; D013025:Glycine max / Q000382:microbiology*; D014158:Transcription, Genetic / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D012329:RNA, Bacterial