[Construction of transgenic tobacco expressing popW and analysis of its biological phenotype]

In a previous study, we cloned popW from Ralstonia solanacearum strain ZJ3721, coding PopW, a new harpin protein. The procaryotically expressed PopW can induce resistance to Tobacco mosaic virus (TMV), enhance growth and improve quality of tobacco, when sprayed onto tobacco leaves. Here, we constructed an expression vector pB- popW by cloning popW into the bionary vector pBI121 and transformed it into Agrobacterium tumefaciens strain EHA105 via freeze-thaw method. Tobacco (Nicotiana tobacum cv. Xanthi nc.) transformation was conducted by infection of tobacco leaf discs with recombinant A. tumefaciens. After screening on MS medium containing kanamycin, PCR and RT-PCR analysis, 21 T3 lines were identified as positive transgenic. Genomic intergration and expression of the transferred gene were determined by PCR and RT-PCR. And GUS staining analysis indicated that the protein expressed in transgenic tobacco was bioactive and exhibited different expression levels among lines. Disease bioassays showed that the transgenic tobacco had enhanced resistance to TMV with biocontrol efficiency up to 54.25%. Transgenic tobacco also exhibited enhanced plant growth, the root length of 15 d old seedlings was 1.7 times longer than that of wild type tobacco. 60 d after transplanting to pots, the height, fresh weight and dry weight of transgenic tobacco were 1.4, 1.7, 1.8 times larger than that of wild type tobacco, respectively.