The Arabidopsis bZIP1 Transcription Factor Is Involved in Sugar Signaling, Protein Networking, and DNA Binding

Abstract

Sugar signaling is a mechanism that plants use to integrate various internal and external cues to achieve nutrient homeostasis, mediate developmental programs, and articulate stress responses. Many bZIP transcription factors are known to be involved in nutrient and/or stress signaling. An Arabidopsis S1-group bZIP gene, AtbZIP1, was identified as a sugar-sensitive gene in a previous gene expression profiling study (Plant Cell. 16, 2128-2150). In this report, we show that the expression of AtbZIP1 is repressed by sugars in a fast, sensitive, and reversible way. The sugar repression of AtbZIP1 is affected by a conserved sugar signaling component, hexokinase. Besides being a sugar-regulated gene, AtbZIP1 can mediate sugar signaling and affect gene expression, plant growth, and development. When carbon nutrients are limited, gain or loss of function of AtbZIP1 causes changes in the rates of early seedling establishment. Results of phenotypic analyses indicate that AtbZIP1 acts as a negative regulator of early seedling growth. Using gain- and loss-of-function plants in a microarray analysis, two sets of putative AtbZIP1-regulated genes have been identified. Among them, sugar-responsive genes are highly over-represented, implicating a role of AtbZIP1 in sugar-mediated gene expression. Using yeast two-hybrid (Y-2-H) screens and bimolecular fluorescence complementation (BiFC) analyses, we are able to recapitulate extensive C/S1 AtbZIP protein interacting network in living cells. Finally, we show that AtbZIP1 can bind ACGT-based motifs in vitro and that the binding characteristics appear to be affected by the heterodimerization between AtbZIP1 and the C-group AtbZIPs, including AtbZIP10 and AtbZIP63.

Heterodimers of the Arabidopsis Transcription Factors bZIP1 and bZIP53 Reprogram Amino Acid Metabolism during Low Energy Stress

“…3-oMG is taken up by the cells but is not metabolized and appears not to signal via the hexokinase-dependent sugar signaling pathway (Cortè s et al, 2003). These data indicate that sugar signaling regulates the transcription of bZIP1 and bZIP53, supporting recent findings by Kang et al (2010). Since long-time dark treatments, which have frequently been applied for darkinduced senescence studies (Gan, 2003;Lin and Wu, 2004;Buchanan-Wollaston et al, 2005), do not reflect natural environmental conditions, we performed short-term experiments that described the detailed expression changes after extended night treatments and defined bZIP1 and bZIP53 as putative transcriptional regulators in the starvation response ( Figure 1A).…”

The role of sugar signaling in plant defense responses against fungal pathogens

“…For example, their transcriptional responses to sugars are variable: while AtbZIP11 is sugar inducible, AtbZIP1, AtbZIP2, and AtbZIP53 are sugar repressible (Price et al 2004). Translation of bZIP11 mRNA in A. thaliana is repressed in response to sucrose (other sugars tested were found to be less effective -Hummel et al 2009), whereas in the carbohydrate-consuming sink tissue it is up-regulated at the mRNA level (Rook et al 1998;Kang et al 2010). Proteins of S1 bZIP transcription factors bind with proteins belonging to the C-class of bZIPp and only such heterodimers are activated by KIN10/11 (Ehlert et al 2006;Hanson and Smeekens 2009).…”

“…They are small proteins, generally involved in sugar and stress signaling. In Arabidopsis they are S1, bZIP1, bZIP2, bZIP11, bZIP44 and bZIP53 subgroups whose synthesis is repressed by sucrose at the translation level (Baena-Gonzalez et al 2007;Hanson et al 2008;Kang et al 2010). In the case of certain bZIP members of the S1 subgroup, additional sugar-induced regulations were detected.…”

Discover and Connect Cellular Signaling

“…It is likely that SnRK1 plays critical roles throughout the embryogenesis process from proliferation to seed maturation and desiccation. Extensive bZIP heterodimerizations (bZIP1,11,44,53,and bZIP10,25,63) have also been revealed in maize and Arabidopsis mesophyll protoplasts (Kang et al, 2010). Arabidopsis plant studies uncover the critical functions of bZIP1 and bZIP11 in controlling seedling development and amino acid metabolism, respectively (Hanson et al, 2008;Kang et al, 2010).…”

“…Extensive bZIP heterodimerizations (bZIP1,11,44,53,and bZIP10,25,63) have also been revealed in maize and Arabidopsis mesophyll protoplasts (Kang et al, 2010). Arabidopsis plant studies uncover the critical functions of bZIP1 and bZIP11 in controlling seedling development and amino acid metabolism, respectively (Hanson et al, 2008;Kang et al, 2010). A creative systems approach has identified bZIP1 in an organic nitrogen-responsive gene network that is also regulated by the master clock control TF CCA1 (Gutiérrez et al, 2008).…”