Transcriptome profiling reveals the importance of plasmid pSymB for osmoadaptation of Sinorhizobium meliloti.
In this work, DNA microarrays were used to investigate genome-wide transcriptional responses of Sinorhizobium meliloti to a sudden increase in external osmolarity elicited by addition of either NaCl or sucrose to exponentially growing cultures. A time course of the response within the first 4 h after the osmotic shock was established. We found that there was a general redundancy in the differentially expressed genes after NaCl or sucrose addition. Both kinds of stress resulted in induction of a large number of genes having unknown functions and in repression of many genes coding for proteins with known functions. There was a strong replicon bias in the pattern of the osmotic stress response; whereas 64% of the upregulated genes had a plasmid localization, 85% of the downregulated genes were chromosomal. Among the pSymB osmoresponsive genes, 83% were upregulated, suggesting the importance of this plasmid for S. meliloti osmoadaptation. Indeed, we identified a 200-kb region in pSymB needed for adaptation to saline shock which has a high density of osmoregulated genes.
Domínguez-Ferreras
Ana
A
Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidin, CSIC, Prof. Albareda 1, E-18008 Granada, Spain.
Pérez-Arnedo
Rebeca
R
Becker
Anke
A
Olivares
José
J
Soto
María J
MJ
Sanjuán
Juan
J
D000222:Adaptation, Physiological; D002876:Chromosomes, Bacterial / Q000235:genetics; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006982:Hypertonic Solutions; D020411:Oligonucleotide Array Sequence Analysis; D009997:Osmotic Pressure; D010957:Plasmids / Q000235:genetics*; D012329:RNA, Bacterial / Q000032:analysis / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D016962:Sinorhizobium meliloti / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D012965:Sodium Chloride; D013395:Sucrose
D006982:Hypertonic Solutions; D012329:RNA, Bacterial; D012333:RNA, Messenger; D012965:Sodium Chloride; D013395:Sucrose