Expression patterns within the Arabidopsis C/S1 bZIP transcription factor network: availability of heterodimerization partners controls gene expression during stress response and development

Abstract

Members of the Arabidopsis group C/S1 basic leucine zipper (bZIP) transcription factor (TF) network are proposed to implement transcriptional reprogramming of plant growth in response to energy deprivation and environmental stresses. The four group C and five group S1 members form specific heterodimers and are, therefore, considered to cooperate functionally. For example, the interplay of C/S1 bZIP TFs in regulating seed maturation genes was analyzed by expression studies and target gene regulation in both protoplasts and transgenic plants. The abundance of the heterodimerization partners significantly affects target gene transcription. Therefore, a detailed analysis of the developmental and stress related expression patterns was performed by comparing promoter: GUS and transcription data. The idea that the C/S1 network plays a role in the allocation of nutrients is supported by the defined and partially overlapping expression patterns in sink leaves, seeds and anthers. Accordingly, metabolic signals strongly affect bZIP expression on the transcriptional and/or post-transcriptional level. Sucrose induced repression of translation (SIRT) was demonstrated for all group S1 bZIPs. In particular, transcription of group S1 genes strongly responds to various abiotic stresses, such as salt (AtbZIP1) or cold (AtbZIP44). In summary, heterodimerization and expression data provide a basic framework to further determine the functional impact of the C/S1 network in regulating the plant energy balance and nutrient allocation.

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

“…As demonstrated in previous studies (Wiese et al, 2004;Weltmeier et al, 2009), a posttranscriptional regulatory mechanism applies for all group S1 bZIPs, including bZIP1 and bZIP53, which leads to a sucrose-induced repression of translation mediated by a conserved system of upstream open reading frames (uORFs). With respect to bZIP1 and bZIP53, transcriptional and posttranscriptional mechanisms interact to enhance expression in response to dark treatment.…”

“…(B) Histochemical GUS staining of transgenic plants expressing ProbZIP1:GUS (top panel) and ProbZIP53:GUS (bottom panel). The upstream regions of the constructs expressed in these plants (diagram above) contain the conserved system of uORFs (depicted by rectangles) that mediates sucrose-dependent posttranslational repression (Wiese et al, 2005;Weltmeier et al, 2009). GUS staining of plants grown under a 16/8-h day/night cycle (0 h) or darkness for 48 and 120 h is shown.…”

A Pivotal Role of the Basic Leucine Zipper Transcription Factor bZIP53 in the Regulation ofArabidopsisSeed Maturation Gene Expression Based on Heterodimerization and Protein Complex Formation

“…However, ectopic overexpression of At bZIP1 does not lead to activation of MAT genes, indicating a lack of functional redundancy of these genes in MAT gene regulation (Weltmeier et al, 2009).…”

“…Interestingly, salt treatment dramatically induces bZIP53 transcription in roots (Weltmeier et al, 2009). In the context of the seed, it is worth mentioning that besides storage compound accumulation, dehydration occurs during late stages of the maturation phase.…”

“…Recently, we demonstrated that group C bZIPs, such as bZIP10 and bZIP25, preferentially interact with group S1 bZIPs, resulting in a set of specific heterodimers designated the C/S1 network of bZIP TFs . In particular, members of the C/S1 network have been implicated in energy homeostasis (Baena-Gonzalez et al, 2007;Usadel et al, 2008), amino acid metabolism Hanson et al, 2008), stress response (Kaminaka et al, 2006), and sinkspecific gene expression (Rook et al, 1998;Weltmeier et al, 2009). Importantly, these heterodimers were shown to convey synergistic activation properties to target genes, suggesting that heterodimerization serves as an efficient mechanism of signal integration .…”