Effect of Surfactin on inducing tobacco resistance against Agrobacterium

Crown gall is one of the most destructive bacterial diseases of plants. Nowadays, special attention has been focused on the biological control of plant diseases as an alternative to chemical control. This study was conducted to better understanding the molecular mechanism of Surfactin on Agrobacterium tumefaciens as a prerequisite for the use of Bacillus as a biocontrol agent of this pathogen. In this study, Tobacco plants (Nicotiana tabacum), IBRC-M10701 strains of A. tumefaciens, and pure commercial Surfactin (25 µm) were used. miRNAs and lox genes have an important effect in the auxin signalling pathway. Using Real-time PCR, the expression level of miR167 and lox gene measured 1, 3, and 6 days after inoculations in the interaction of A. tumifaciens IBRC-M10701 and Surfactin. The expression level of lox gene in Agrobacterium treatment showed 0.47, 22.9, and 61.8 increased. In Surfactin treatment it was 4.6, 3.6 and, 11.6 fold and in Surfactin-Agrobacterium treatment this amount was 4.2, 38.8, and 20.3 fold. In addition, the expression level of nta-miRNA167 in Agrobacterium treatment indicated an increase of 3.4 and 214.4 fold (in the first and third day after inoculation), then decreased to 2.5 fold (in the sixth day), in treatment with Surfactin the amount of expression level was detected as 3.2, 13.2 and 4.5 fold and in Surfactin-Agrobacterium treatment this amount was 1.6, 2.2 and 9.6 fold compared with the control. All of the results indicated the positive effect of Surfactin in suppression the strain IBRC-M10701 of Agrobacterium. The results indicated the key role of Surfactin in biocontrol which reflected the possible use of Bacillus strains producing Surfactin in biological control.