Transactivation of a target gene through feedforward loop activation in plants

The expression of many genes encoding transcriptional activators in prokaryotes and eukaryotes is upregulated through positive feedback activation. During positive feedback activation, a transcriptional activator binds to its own promoter and thus increases its own expression as well as the expression of its target genes. In the simplest case, increased levels of the transcriptional activator can be directly correlated with increased expression of its target genes. In this study, we present a gene expression system, designated feedforward loop (FFL) system, which makes use of this kind of positive feedback regulation for the expression of plant transgenes. We show in transient and stable transformation experiments that such a system is functional and that it can be used to obtain high level gene expression in plants. We also provide evidence that the transgene is ubiquitously expressed when using the FFL system. Finally, we discuss the possibilities of using FFL gene expression systems for applications in plant molecular genetics and biotechnology.