Regulation of transgene expression in plants with polydactyl zinc finger transcription factors

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Abstract
Designer zinc finger transcription factors (TFs(ZF)) have been developed to control the expression of transgenes and endogenous genes in mammalian cells. Application of TFs(ZF) technology in plants would enable a wide range of both basic and applied studies. In this paper, we report the use of TFs(ZF) to target a defined 18-bp DNA sequence to control gene expression in plant cells and in transgenic plants. A beta-glucuronidase reporter gene was activated by using the designed six-zinc finger protein 2C7 expressed as a fusion with the herpes simplex virus VP16 transcription factor activation domain. Reporter gene expression was activated 5- to 30-fold by using TFs(ZF) in BY-2 protoplasts, whereas expression was increased as much as 450 times in transgenic tobacco plants. Use of a phloem-specific promoter to drive expression of the TFs(ZF) resulted in activation of the reporter gene in vascular tissues. Transgenic tobacco plants that produce 2C7 transcription factors were phenotypically normal through two generations, suggesting that the factors exerted no adverse effects. This study demonstrates the utility of zinc finger technology in plants, setting the stage for its application in basic and applied agricultural biotechnology.