Light regulated modulation of Z‐box containing promoters by photoreceptors and downstream regulatory components, COP1 and HY5, in Arabidopsis

Abstract

SummaryThe Z-box is one of the light-responsive elements (LREs) found in the promoters of light inducible genes. We have studied the light responsive characteristics of Z-box containing synthetic as well as native promoters. We show that promoters with Z-box as a single LRE or paired with another LRE can respond to a broad spectrum of light. The response is primarily mediated by phyA, phyB and CRY1 photoreceptors at their respective wavelengths of light. We have demonstrated that CAB1 and Z-GATA containing promoters are down-regulated in hy5 mutants in the light. On the other hand, a promoter with Z-box alone is down-regulated in hy5 mutants both in dark and in light conditions, suggesting involvement of a similar regulatory system in the regulation of the promoter in two distinct developmental pathways: skotomorphogenesis and photomorphogenesis. Furthermore, similar to the CAB1 promoter, a Z-GATA containing promoter is derepressed in cop1 mutants in the dark. DNA±protein interaction studies reveal the presence of a DNA-binding activity that is speci®c to Z-box. These results provide insights into the regulation of the Z-box LRE mediated by various light signaling components.

Integration of low temperature and light signaling during cold acclimation response in Arabidopsis

“…Although several LTREs have been described so far (28)(29)(30), to our knowledge the Z-box is the first cis-regulatory sequence reported that integrates light and cold signaling. Light-induced gene expression mediated by the Z-box, including that of CAB1, depends on HY5 (14). Interestingly, our findings reveal that the cold-induced expression of CAB1 also depends on HY5, suggesting a role for this factor in regulating gene expression in response to low temperature.…”

“…Our data show that the Z-box, in addition to mediating light-induced gene expression (14), also mediates CAB1 expression in response to low temperature and constitutes an LTRE. Although several LTREs have been described so far (28)(29)(30), to our knowledge the Z-box is the first cis-regulatory sequence reported that integrates light and cold signaling.…”

“…1A). These results suggested that the Z-box, a motif involved in light-regulated gene expression (14), could be responsible for the cold induction of CAB1. To confirm this assumption, 4-d-old Arabidopsis etiolated seedlings containing a dimer of the Z-box fused to the NOS basal promoter and to the GUS gene (Z:NOS:GUS) (15) were examined for their GUS expression and activity in response to low temperature.…”

Light Induces Peroxisome Proliferation in Arabidopsis Seedlings through the Photoreceptor Phytochrome A, the Transcription Factor HY5 HOMOLOG, and the Peroxisomal Protein PEROXIN11b

“…The DNA-binding assays were performed as described by Yadav et al (2002) at room temperature in a final volume of 25 mL of binding buffer [15 mM HEPES, pH 7.5, 35 mM KCl, 1 mM EDTA, 6% glycerol (v/v), 1 mM dithiothreitol, 1 mM MgCl 2 , and 0.5 mg poly(dI-dC)]. The samples were incubated at room temperature for 15 min and later run on a 5% polyacrylamide gel at 12 to 15 mAmp.…”

DNA-Binding Study Identifies C-Box and Hybrid C/G-Box or C/A-Box Motifs as High-Affinity Binding Sites for STF1 and LONG HYPOCOTYL5 Proteins

“…binding site (Cheong et al, 1998). The HY5 protein interacts with both the G-(CACGTG) and Z-(ATACGTGT) boxes of the light-regulated promoter of RbcS1A (ribulose bisphosphate carboxylase small subunit) and the CHS (chalcone synthase) genes Chattopadhyay et al, 1998;Yadav et al, 2002). To test whether STF1 and HY5 have similar DNA-binding properties, the binding properties of each were compared with eight different DNA sequences that represent G-, C-, and C/G-box motifs (Fig.…”