November
2007
, Volume
20
, Number
11
Pages
1,353
-
1,363
Authors
Gabriella
Pessi
,
1
Christian H.
Ahrens
,
2
Hubert
Rehrauer
,
2
Andrea
Lindemann
,
1
Felix
Hauser
,
1
Hans-Martin
Fischer
,
1
and
Hauke
Hennecke
1
Affiliations
1Institute of Microbiology, Eidgenössische Technische Hochschule (ETH), CH-8093 Zürich, Switzerland; 2Functional Genomics Center Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
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RelatedArticle
Accepted 29 June 2007.
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 σ54. This led to a collection of hitherto unrecognized B. japonicum genes potentially transcribed in planta in a σ54-dependent manner.
JnArticleKeywords
Additional keywords:GeneChip, nitrogen fixation, RpoN.
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ArticleCopyright
© 2007 The American Phytopathological Society