The Arabidopsis bZIP Gene AtbZIP63 Is a Sensitive Integrator of Transient Abscisic Acid and Glucose Signals    

Abstract

Glucose modulates plant metabolism, growth, and development. In Arabidopsis (Arabidopsis thaliana), Hexokinase1 (HXK1) is a glucose sensor that may trigger abscisic acid (ABA) synthesis and sensitivity to mediate glucose-induced inhibition of seedling development. Here, we show that the intensity of short-term responses to glucose can vary with ABA activity. We report that the transient (2 h/4 h) repression by 2% glucose of AtbZIP63, a gene encoding a basic-leucine zipper (bZIP) transcription factor partially involved in the Snf1-related kinase KIN10-induced responses to energy limitation, is independent of HXK1 and is not mediated by changes in ABA levels. However, high-concentration (6%) glucose-mediated repression appears to be modulated by ABA, since full repression of AtbZIP63 requires a functional ABA biosynthetic pathway. Furthermore, the combination of glucose and ABA was able to trigger a synergistic repression of AtbZIP63 and its homologue AtbZIP3, revealing a shared regulatory feature consisting of the modulation of glucose sensitivity by ABA. The synergistic regulation of AtbZIP63 was not reproduced by an AtbZIP63 promoter-5#-untranslated region::b-glucuronidase fusion, thus suggesting possible posttranscriptional control. A transcriptional inhibition assay with cordycepin provided further evidence for the regulation of mRNA decay in response to glucose plus ABA. Overall, these results indicate that AtbZIP63 is an important node of the glucose-ABA interaction network. The mechanisms by which AtbZIP63 may participate in the finetuning of ABA-mediated abiotic stress responses according to sugar availability (i.e., energy status) are discussed.

Predictive Models of Spatial Transcriptional Response to High Salinity

“…First, we identified pCREs that are identical to TFBMs. Only two pCREs were identical (PCC = 1) to experimentally determined binding motifs: ATBZIP63, which is involved in abscisic acid (ABA) biosynthesis (Matiolli et al, 2011), and ABF3, which is involved in ABA signaling (Kang et al, 2002), consistent with their roles in the salt stress response. Second, given that PCC = 1 is highly stringent, we designated a pCRE-TFBM pair as having significant similarity if its PCC is significantly higher (at the 5% level) than PCCs of TF pairs from the same family (red circles in Fig.…”

“…Salt stress was chosen because it is well studied both physiologically (Munns, 2002;Munns and Tester, 2008) and molecularly (Zhu, 2002;Golldack et al, 2011) and because there are documented differences in the transcriptional response to salt in the root and shoot (Kreps et al, 2002;Kilian et al, 2007). Additionally, there are known TFs and CREs for salt stress (Golldack et al, 2011;Matiolli et al, 2011;Mizoi et al, 2012;Nakashima et al, 2012) that could be used to verify our results. To assess the transcriptional changes in response to salt stress across different organs in Arabidopsis, we first asked how the functional annotations of salt up-regulated genes in roots and shoots differed.…”

Effects of Drought on Gene Expression in Maize Reproductive and Leaf Meristem Tissue Revealed by RNA-Seq

“…A set range of Suc-tohexose ratios has been shown to be crucial for seed development (Wobus and Weber, 1999), and this ratio appears to be altered during drought stress during this early stage. Sugars function both as a nutrient source and signaling molecules in plant cells (for review, see Couée et al, 2006;Ruan et al, 2010), and ample evidence exists suggesting distinct cellular Glc and Suc signaling pathways (Bolouri-Moghaddam et al, 2010;Matiolli et al, 2011). In addition, cell wall invertase itself is likely part of a signaling pathway, since it is known to form a complex in the nucleus with PIP5K9, a component of the phosphoinositol signaling system (Lou et al, 2007).…”

The Energy-Signaling Hub SnRK1 Is Important for Sucrose-Induced Hypocotyl Elongation

“…SnRK1 controls metabolic enzymes directly by protein phosphorylation (Baena-González and Sheen, 2008). It also regulates greater than 1000 transcripts in response to carbohydrate availability, for example by adjusting bZIP transcription factor activity (Baena-González et al, 2007;Smeekens et al, 2010;Delatte et al, 2011;Matiolli et al, 2011;Mair et al, 2015). Both SnRK1-and hexokinasemediated sugar signaling involve specific sugars functioning as signaling molecules that provide cellular information concerning sugar availability.…”