Transcriptional Networks Reveal Different Mechanisms to Achieve Tissue-Specific Expression Patterns in the Arabidopsis Root

Tissue-specific expression of transcription factors is central to the regulation of cell fate and function. To begin uncovering the mechanisms controlling transcription factor expression in the Arabidopsis thaliana (Arabidopsis) root, we used enhanced Yeast-1-Hybrid (eY1H) assays to screen the promoters of 115 transcription factors (TFs) against a library of 555 TFs. The resulting gene regulatory network provides a platform for the dissection of TF transcriptional regulation, and we focused our attention on two TFs required for endodermal development. SHORTROOT (SHR) is expressed in the vascular tissue and moves into the endodermis to interact with SCARECROW (SCR). Together these TFs up-regulate the expression of SCR to promote endodermal cell fate. However the mechanism through which the tissue-specific expression patterns of SHR and SCR are established remains to be determined.  We used sub-networks from the broader gene regulatory network to ask how the expression patterns of SHR and SCR are generated. Our results suggest the tissue-specific expression patterns of SHR and SCR are mediated by two different regulatory mechanisms.