Mutated TATA-box/TATA binding protein complementation system for regulated transgene expression in tobacco

A two-component expression system was developed to achieve tightly regulated expression of transgenes in plants. One component functioned as an expression module whereas the other functioned as a regulatory module. The expression module comprised a highly expressing TATA-dependent seed-specific promoter in which the TATA motif in the core promoter was mutated to TGTA. The regulatory module expressed a mutated general transcription factor TBPm ₃ that recognized TGTA and initiated transcription. Vectors were designed using component one alone or in combination with component two, and were transformed into tobacco. The TGTA mutation in the TATA-box completely inactivated the promoter, making component one non-functional. This non-functional module became transcriptionally active in the presence of the component two that expressed TBPm₃. The reporter gene gusA was expressed from the TGTA-containing chimeric legumin promoter, in a tightly seed-specific manner, in transgenic tobacco plants in the presence of TBPm ₃ that was expressed from a constitutive promoter. The results show that the TGTA and TBPm₃ combination can be used to achieve high-level tissue-specific expression of TATA-dependent promoters.