Passive repressors, in contrast, interfere with transcriptional activators and prevent their binding to the DNA to cause transcription repression (Kazan 2006 Krogan and Long 2009).Ĭhimeric repressors, which have been used to study gene function in animal and plant systems, have a DNA-binding domain or a transcription factor fused to a variety of repression domains (Beerli et al. Active repressors exhibit an intrinsic repression activity because they have defined repression domains that can interfere with the formation of the transcription pre-initiation complex and basal transcription (Krogan and Long 2009 Mahfouz 2010). Transcriptional repression effects occur at several levels and involve active and passive repressors. Researchers use factors that activate or repress gene expression to understand gene function and phenotypic effects (Krogan and Long 2009). Plants use many different transcription factors to modulate gene expression and achieve the correct spaciotemporal control of gene activation and repression. Consequently, the percentage of transcription factor genes relative to the whole gene content is higher in Arabidopsis (6–10%) than in organisms with genomes of similar size including Drosophila melanogaster (4.7%) and Caenorhabditis elegans (3.6%) (Riechmann et al. The Arabidopsis genome is predicted to contain 25,498 genes, and more than 2000 of these are transcription factors. The analysis of the completed plant genome sequences revealed that transcriptional regulation plays a very pronounced role in plants (Riechmann et al. Although such understanding has become increasingly possible with rapid advances in DNA sequencing technologies, the challenge is to turn information about gene sequence into knowledge about gene function. Understanding these responses requires that we understand the functioning of plant genes. Plants are sessile organisms and rely on a wide array of molecular mechanisms to control and adjust their adaptive responses to developmental and environmental cues.

This sequence-specific transcriptional repression by direct on promoter effector technology is a powerful tool for functional genomics studies and biotechnological applications.

Our data suggest that TALEs can be used to generate chimeric repressors to specifically repress the transcription of genes of interest in plants. Genome wide expression profiling showed that the chimeric repressor also inhibited the expression of several other genes that contain the designer TALE-target sequence in their promoters. The dHax3.SRDX protein efficiently repressed the transcription of the RD29A::LUC transgene and endogenous RD29A gene in Arabidopsis. The dHax3 TALE was used as a scaffold to provide a DNA-binding module fused to the EAR-repression domain (SRDX) to generate a chimeric repressor that targets the RD29A promoter. Here we report the use of TALEs to generate chimeric sequence-specific transcriptional repressors.

TALEs contain a modular DNA binding domain that can be easily engineered to bind any sequence of interest, and have been used to provide user-selected DNA-binding modules to generate chimeric nucleases and transcriptional activators in mammalian cells and plants. Transcriptional activator-like effectors (TALEs) are proteins secreted by Xanthomonas bacteria when they infect plants.

Srdx figurine leena