Expression of Protein Elicitor-Encoding Gene pemG1 in Tobacco (Nicotiana tobacum cv. Samsun NN) Plants and Enhancement of Resistance to TMV

The pemG1 gene from Magnaporthe grisea was transferred into tobacco (Nicotiana tobacum cv. Samsun NN) to test its functions. Plant expression vector pCAMBIA2300-Ubi-pemG1-Oc harboring elicitor-encoding gene pemG1 was constructed. The maize ubiquitin promoter/octopine synthase terminator system and kanamycin-resistant gene npt II were used for constitutive expression systems. The vector was then introduced into Agrobacterium tumefaciens strain AGL-1 with freeze-thaw method. Tobacco primary transformants were produced by leaf disc transformation. The kanamycin-resistant regenerated plants were confirmed to be electropositive by PCR. Integration and expression of the pemG1 gene were further confirmed by Southern blotting and Western blotting analyses. Transgenic tobacco plants of T2 generation were successively inoculated with Tobacco Mosaic Virus (TMV) at virus concentrations of 0.2 and 0.5 mg per leaf. In comparison with TMV-infected wild-type plants, PemG1-expressed plants displayed reduced hypersensitive-response lesions in both inoculation treatments. Furthermore, accumulation level of pemG1 steady-state transcripts was examined at 24 h after inoculation. The results indicated that the reduction of lesions corresponded to the accumulation of pemG1 steady-state transcripts as monitored by Northern blotting analysis. All these indicated that the expression of pemG1 in tobacco plants improved the resistance to TMV.