Comparative study of constitutive and inducible promoters in tobacco

The 42 kDa endochitinase gene of Trichoderma hamatum was expressed in tobacco, led by the constitutive 35S promoter of Cauliflower Mosaic Virus and the inducible Actin 7 promoter of Arabidopsis thaliana. Transgenic tobacco events containing the 35S promoter had increased chitinase levels in the leaves and enhanced tolerance to Botrytis cinerea, but their stems were still susceptible to infection. When the Actin 7 promoter was used, the resulting transgenic tobacco events exhibited tolerance to the pathogen even in the stem. The presence of the transgene was monitored by PCR analysis and the sequence of the PCR product confirmed the integration of the chitinase gene. Analysis of the transgenic plants showed that the lines were heterogeneous. Southern hybridization confirmed a single copy of the transgene in lines transformed with the 35S promoter, while the copy number was 1–4 in lines transformed with the Actin 7 promoter. Compared to the untransformed control, chitinase activity was higher in the leaves of the transgenic plants. This increase was not observed in the stems. In this comparative promoter analysis the stress-induced promoter proved to be more effective in obtaining mould-resistant plants.