Cloning and complementation analysis ofgreA gene involved in salt tolerance ofSinorhizobium meliloti

Abstract

Previously, we isolated the salt-sensitive mutant W2 by random Tn5 mutagenesis ofSinorhizobium meliloti 042BM strain, which contained single Tn5 insertion in the gene ofgreA, encoding transcription cleavage factor. To characterise the role of the novelgreA gene in salt tolerance ofS. meliloti 042BM strain, the full-length region ofgreA gene including putative promoter was cloned by PCR and thegreA region was introduced into salt-sensitive mutant W2 by triparental mating. The growth of the mutant W2 was restored by complementation ofgreA gene on 0.4 mol l−1 NaCl. It is demonstrated that thegreA gene acts as an important role for salt tolerance ofS. meliloti 042BM and the salt-sensitive phenotype of the mutant W2 is due to the inactivity ofgreA gene rather than polar effect on other genes resulting fromgreA mutation.