Explore the vast range of titles available.

• Adjustment to energy starvation is crucial to ensure growth and survival. In Arabidopsis thaliana (Arabidopsis), this process relies in part on the phosphorylation of the circadian clock regulator bZIP63 by SUCROSE non-fermenting RELATED KINASE1 (SnRK1), a key mediator of responses to low energy. • We investigated the effects of mutations in bZIP63 on plant carbon (C) metabolism and growth. Results from phenotypic, transcriptomic and metabolomic analysis of bZIP63 mutants prompted us to investigate the starch accumulation pattern and the expression of genes involved in starch degradation and in the circadian oscillator. • bZIP63 mutation impairs growth under light-dark cycles, but not under constant light. The reduced growth likely results from the accentuated C depletion towards the end of the night, which is caused by the accelerated starch degradation of bZIP63 mutants. The diel expression pattern of bZIP63 is dictated by both the circadian clock and energy levels, which could determine the changes in the circadian expression of clock and starch metabolic genes observed in bZIP63 mutants. • We conclude that bZIP63 composes a regulatory interface between the metabolic and circadian control of starch breakdown to optimize C usage and plant growth.

The yield and protein content of soybean seeds are challenging traits for breeding since they have a negative correlation. To solve this issue, it is essential to understand the protein transport in soybean seeds. Here we performed an analysis of 3 datasets containing transcriptional data from soybean seeds and pods, without any treatment, aiming to select genes related to the transport of organic nitrogen compounds. We identified 69 transporters, and among them, seven were chosen to be validated by qRT-PCR. Seeds and pods of soybean cultivars BRS 232 and BRS 284, respectively, presenting higher and lower protein content, were assayed under normal growth condition. Results showed in BRS 232 soybean cultivar, a positive correlation between seed protein content and gene expression for five out of the seven genes analyzed. These nitrogen compounds transporters can play an essential role in the storage of proteins, thus increases the protein content of soybean seeds and contributes to the decrease the negative correlation between yield and protein content of soybean seeds.

Hormone signaling fine-tuning involves feedback regulatory loops. Abscisic acid (ABA) plays key functions in development and tolerance to abiotic stress. ABA is sensed by the PYR/PYL/RCAR receptors and it also represses their gene expression. Conversely, ABA induces PP2C phosphatases expression, which are negative regulators of the ABA signaling pathway. This feedback regulatory scheme is likely important for the modulation of ABA signal transduction. Here, we provide a new insight into the mechanisms underlying the ABA-induced negative control of PYR/PYL/RCAR expression in Arabidopsis thaliana. The strong and sustained repression of PYR/PYL/RCARs revealed by ABA time course treatment defines the regulation of receptors genes as an important step in resetting the ABA signaling pathway. Transcription inhibition by cordycepin showed that destabilization of PYL1/4/5/6 mRNA is involved in ABA-induced repression of these genes. Furthermore, genetic evidence indicated that decapping may play a role in PYL4/5/6 mRNAs decay. In addition, we provide evidence that the Arabidopsis-specific microRNA5628 (miR5628), which is transiently induced by the ABA core signaling pathway, guides the cleavage of PYL6 transcript in response to ABA. After cleavage, the resulting RISC 5'- and 3'-cleaved fragments of PYL6 mRNA may be degraded by exoribonuclease XRN4. MiR5628 is an evolutionary novelty that may contribute, with decapping and XRN4 activities, to enhance PYL6 mRNA degradation. Thus, control of stability of PYR/PYL/RCAR transcripts is an important step in maintaining homeostasis of ABA signaling.

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::beta-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 fine-tuning of ABA-mediated abiotic stress responses according to sugar availability (i.e., energy status) are discussed.