Response to an UV-B pulse of Arabidopsis seedling containing synthetic promoters fused to a luciferase reporter is shown. An native ELIP2 promoter which is the source of the synthetic elements is also analyzed. In vivo luciferase activity was measured every 30 minutes for 24 h following a pulse of UV-B irradiation (52.6 µmol m–2). For each constructs, average of four to five independent transgenic lines is shown, with SD values provided once for every 3-h interval. The absolute level of luciferase activity at 0 h is designated as 1.0 for each construct.
When plants are exposed to some stress, a cascade of gene activation by transcription factors (TFs, red circle) occurs. The cascade, or transcriptional network, has a role in generation of the transcriptional response of a variety of genes (red and blue circles). One of our goals is identification of direct regulation among involved transcription factors.

Higher plants are exposed to various environmental stresses which affect their survival and growth. Organellar perturbation which is caused by environmental stresses results in modulation of nuclear gene expression as a feedback regulation to relieve these stresses. To understand mechanisms of environmental adaptation that is achieved in part through the chloroplast signaling, or retrograde signaling, the authors Natsuki Hayami and Yoshiharu Y. Yamamoto are analyzing the transcriptional network that orchestrates stress responses in higher plants. Determination of cis-regulatory elements in the promoter region is an old subject in plant science but still provides essential information on the transcriptional network, and, it is now much more easily and more comprehensively conducted with the aid of our recently developed methodologies of bioinformatics. Functional analysis of synthetic promoters that contain only one or two cis-regulatory elements provides precise information on the upstream signals driving the cis-elements, which is also necessary to understand the network. In addition, biochemical analysis of DNA-protein interaction that is scalable with the aid of oligo DNA and a cDNA resource of Arabidopsis transcription factors (TFs) enables empirical determination of a middle-scale transcriptional network.