Third, they avoid problems that associate with replicating plasmid systems which can disrupt regulation of expression due to copy number effects. Second, the fusions do not need antibiotics for maintaining their stability in the genome. The chromosomal uidA transcriptional fusions are frequently used for monitoring in vivo expression of bacterial genes for at least three reasons: First, the fusions allow the transcriptional activities of bacterial genes to be monitored at their nature levels. It is also applicable for other rhizobial strains. ConclusionsĪ simple, pVMG-based method for construction of chromosomal uidA transcriptional fusions has been successfully used in the model rhizobium S. This indicates the presence of AHL signals at the late stages of symbiosis. meliloti in the senescence zone of the nodule on the host plant, M. As a demonstration of its usefulness, the N-acyl homoserine lactone (AHL) signal synthase gene promoter was fused to uidA and shown to be expressed by S. All these helps reduce the sample processing time and efforts. Genomic locations of uidA fusions were verified in a simple PCR experiment. pVMG replicated to high copy number in Escherichia coli, offering advantages for the isolation of fusion-containing plasmids and the restriction analysis. Translation termination codons were added in all three reading frames upstream of the promoterless uidA in this vector to ensure transcriptional fusions. The narrow-host-range, fusion selective plasmid pVMG was constructed and used as a vector for the construction of chromosomal uidA transcriptional fusions in the S. However, the construction of the fusions is laborious.
Chromosomal ß-glucuronidase gene ( uidA) transcriptional fusions are frequently used to monitor the expression of bacterial genes during the symbiosis. The soil bacterium Sinorhizobium meliloti and its allies are important nitrogen-fixing bacterial symbionts that cause N 2-fixing nodules on the roots of legumes.
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