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

Abstract

Control of energy homeostasis is crucial for plant survival, particularly under biotic or abiotic stress conditions. Energy deprivation induces dramatic reprogramming of transcription, facilitating metabolic adjustment. An in-depth knowledge of the corresponding regulatory networks would provide opportunities for the development of biotechnological strategies. Low energy stress activates the Arabidopsis thaliana group S1 basic leucine zipper transcription factors bZIP1 and bZIP53 by transcriptional and posttranscriptional mechanisms. Gain-of-function approaches define these bZIPs as crucial transcriptional regulators in Pro, Asn, and branched-chain amino acid metabolism. Whereas chromatin immunoprecipitation analyses confirm the direct binding of bZIP1 and bZIP53 to promoters of key metabolic genes, such as ASPARAGINE SYNTHETASE1 and PROLINE DEHYDROGENASE, the G-box, C-box, or ACT motifs (ACTCAT) have been defined as regulatory cis-elements in the starvation response. bZIP1 and bZIP53 were shown to specifically heterodimerize with group C bZIPs. Although single loss-of-function mutants did not affect starvation-induced transcription, quadruple mutants of group S1 and C bZIPs displayed a significant impairment. We therefore propose that bZIP1 and bZIP53 transduce low energy signals by heterodimerization with members of the partially redundant C/S1 bZIP factor network to reprogram primary metabolism in the starvation response.

Regulatory Functions of SnRK1 in Stress-Responsive Gene Expression and in Plant Growth and Development

“…3, F and H) containing the ATB2/AtbZIP53/ AtbZIP44/GBF5-binding motif. Since AtGBF5 is known to mediate hypoxia-inducible gene regulation (BaenaGonzález et al, 2007), GBF5 and/or this class of bZIP transcription factors (Dietrich et al, 2011) is expected to play a key role in PDC1 activation through SnRK1 in conditions of submergence. The identification of target gene chromatins and protein substrates of the chromatin-associated SnRK1 complex will help to clarify the gene-regulatory mechanisms of SnRK1.…”

The Arabidopsis transcription factor bZIP11 activates auxin-mediated transcription by recruiting the histone acetylation machinery

“…The bZIP factors studied here belong to the C/S1 network of bZIP TFs that have been demonstrated to form specific heterodimers and to be involved in reprogramming of metabolism in response to low energy stress 45,[54][55][56] . Hence, it is tempting to speculate, that the described regulatory mechanism is used to adjust auxin-mediated responses to the energy status of the cell.…”

“…Where portions of blots have been presented in the manuscript, the full blots are shown in the Supplementary Information (Supplementary Fig. 7) QRT-PCR has been performed with SYBR green as described previously 55 . Data were obtained from three replicates of at least two individual plant pools and are normalized to UBQ5 (At3g62250) transcript abundance.…”

“…Hence, these data suggest that bZIPs are not only involved in recruiting the acetylation machinery during auxin-induced transcription. As GREs frequently act as quantitative cis-elements in a wide array of stimulus-induced gene expressions 36,44,54,55 , it is tempting to speculate that GREmediated recruitment of SAGA complexes has a broader impact on gene regulation. Interestingly, the recruitment properties of the bZIPs for specific adapter proteins differ.…”

The Sucrose Starvation Signal Mediates Induction of Autophagy- and Amino Acid Catabolism-Related Genes in Cowpea Seedling

“…Among cowpea homlog genes amino acid catabolic-related enzymes, VuASN1 (TC7410), VuProDH (TC15194) and VuBCAT2 (TC3413) were identified to have the highest similarites of 82%, 62% and 62% in deduced amino acid sequences to AtASN1 (At3g47340), AtProDH (At3g30775) and AtBCAT2 (At1g10070), respectively. Heterodimers of bZIP1 and bZIP53 have been identified to be crucial transcriptional regulators in Asn, Pro and BCAA under sucrose starvation [20]. Among bZIP homolog genes in cowpea ESTs, VubZIP53 (TC-2820) was identified to have the highest similarites of 51% and 26% in amino acid sequences to bZIP53 (At3g-62420) and bZIP1 (At5g49450), respectively.…”