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Title: A Comparative Transcriptome Analysis of Rhizobium etli Bacteroids: Specific Gene Expression During Symbiotic Nongrowth
Authors: Vercruysse, Maarten
Fauvart, Maarten
Beullens, Serge
Braeken, Kristien
Cloots, Lore
Engelen, Kristof
Marchal, Kathleen
Michiels, Jan # ×
Issue Date: Dec-2011
Publisher: APS Press
Series Title: Molecular Plant - Microbe Interactions vol:24 issue:12 pages:1553-1561
Abstract: Rhizobium etli occurs either in a nitrogen-fixing symbiosis with its host plant, Phaseolus vulgaris, or free-living in the soil. During both conditions, the bacterium has been suggested to reside primarily in a non-growing state. Using genome-wide transcriptome profiles, we here examine the molecular basis of the physiological adaptations of rhizobia to non-growth inside and outside of the host. Compared to exponentially growing cells, we found an extensive overlap of downregulated growth-associated genes during both symbiosis and stationary phase, confirming the essentially non-growing state of nitrogen-fixing bacteroids in determinate nodules that are not terminally differentiated. In contrast, the overlap of upregulated genes was limited. Generally, actively growing cells have hitherto been used as reference to analyse symbiosis-specific expression. However, this prevents the distinction between differential expression arising specifically from adaptation to a symbiotic lifestyle and features associated with non-growth in general. Using stationary phase as reference condition, we report a distinct transcriptome profile for bacteroids, containing 203 induced and 354 repressed genes. Certain previously described symbiosis-specific characteristics, such as the downregulation of amino acid metabolism genes, were no longer observed, indicating that these features are more likely due to the non-growing state of bacteroids, rather than representing bacteroid-specific physiological adaptations.
URI: 
ISSN: 0894-0282
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Microbial and Molecular Systems - miscellaneous
Centre of Microbial and Plant Genetics
× corresponding author
# (joint) last author

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