Hit-and-run transcriptional control by bZIP1 mediates rapid nutrient signaling in Arabidopsis. Arabidopsis thaliana

To identify potential transient interactions between a TF and its targets, we developed an approach that can identify primary targets based either on TF-induced regulation or TF-binding, assayed in the same samples. Our studies focused on the TF bZIP1 (BASIC LEUCINE ZIPPER 1), a central integrator of cellular and metabolic signaling. To discern the mechanisms by which bZIP1 regulates a gene netowork in response to a nitrogen (N)-signal perceived in vivo, we perturbed both bZIP1 and the N-signal that it transduces in a cell-based transient expression system called TARGET (Transient Assay Reporting Genome-wide Effects of Transcription factors). Overall design: To identify the genome-wide targets of bZIP1 in response to a N-signal, we transiently perturbed both the TF and the signal in the TARGET cell-based system. Specifically, bZIP1 was transiently overexpressed in root protoplasts following transfection with a 35S::GR::bZIP1 construct containing an RFP (red fluorescent protein) selectable marker gene. bZIP1 transfected cells were sequentially treated with: i) an inorganic nitrogen signal (+/-N), ii) cycloheximide (CHX) to block the synthesis of proteins, and iii) dexamethasone (DEX) to induce nuclear import of the GR::bZIP1 protein. To identify both the TF-regulated and the TF-bound genes, transcriptome analysis of transfected cells and micro-ChIP data (using anti-GR antibodies), were carried out in parallel . This submission represents transcriptome component of study.