Cloning and complementation analysis of greA gene involved in salt tolerance of Sinorhizobium meliloti

Abstract

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