Improvement of salt tolerance of Arabidopsis thaliana seedlings inoculated with endophytic Bacillus cereus KP120

In our previous reports, an endophytic bacterium, Bacillus cereus KP120 was isolated from the halophyte species Kosteletzkya virginica. In this study, the effect of KP120 colonization on Arabidopsis thaliana seedlings was investigated. Our results showed that inoculation with KP120 could promote the growth of A. thaliana seedlings plants under salt-stress conditions, compared with uninoculated controls. After salt treatment, chlorophyll, proline, the activity of antioxidant enzymes, Indole-3-acetic acid and 1-aminocyclopropane-1-carboxylate-deaminase in plants inoculated were increased significantly but malondialdehyde content was decreased compared with the plants under salt stress lonely. Similarly, under non-salt stress, physiological indices above except for MDA in plants inoculated with KP120 were increased compared with control. B. cereus also induced the up-regulation of key genes involved in IAA biosynthesis, responses, transport, down-regulated expression of genes related with ethylene synthesis and response. Our work principally demonstrates that Bacillus cereus KP120 significantly enhances plant growth and increases plant tolerance to salt stress.