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• Chromatin modifications play important roles in plant adaptation to abiotic stresses, but the precise function of histone H3 lysine 36 (H3K36) methylation in drought tolerance remains poorly evaluated. • Here, we report that SDG708, a specific H3K36 methyltransferase, functions as a positive regulator of drought tolerance in rice. SDG708 promoted abscisic acid (ABA) biosynthesis by directly targeting and activating the crucial ABA biosynthesis genes NINE-CIS-EPOXYCAROTENOID DIOXYGENASE 3 (OsNCED3) and NINE-CIS-EPOXYCAROTENOID DIOXYGENASE 5 (OsNCED5). • Additionally, SDG708 induced hydrogen peroxide accumulation in the guard cells and promoted stomatal closure to reduce water loss. Overexpression of SDG708 concomitantly enhanced rice drought tolerance and increased grain yield under normal and drought stress conditions. • Thus, SDG708 is potentially useful as an epigenetic regulator in breeding for grain yield improvement.

Background Currently, mechanical maize kernel harvesting has not been fully utilized in developing countries including China, partly due to the absence of suitable cultivars capable of rapid desiccation during seed maturation. The initiation of rapid desiccation during seed maturation is regulated by abscisic acid (ABA). For further characterization of ABA-regulated key genes and cellular events, it is necessary to perform transcriptome analysis of maize developing embryos. The ABA synthesis-deficient mutant ( vp5 ) and normal maize ( Vp5 ) seeds are suitable materials for such purpose. Results In the present work, developing vp5 and Vp5 embryos were compared by ABA content and transcriptome analyses. Quantitative analysis revealed the significant difference in ABA synthesis between both genotypes. From 29 days after pollination (DAP), ABA content increased rapidly in Vp5 embryos, but decreased gradually in vp5 embryos. At 36 DAP, ABA level in vp5 decreased to 1/4 that of Vp5 , suggesting that the differential ABA levels would affect seed maturation. Comparative transcriptomic analysis has found 1019 differentially expressed genes (DEGs) between both genotypes, with the most DEGs (818) at 36 DAP. Further, weighted correlation network analysis (WGCNA) revealed eight DEGs co-expression modules. Particularly, a module was negatively correlated with ABA content in vp5 embryos. The module was mainly involved in metabolic and cellular processes, and its hub genes encoded thiamine, NPF proteins, calmodulin, metallothionein etc. Moreover, the expression of a set of key genes regulated by ABA was further verified by RT-qPCR. The results of the present work suggested that because of ABA deficiency, the vp5 seeds maintained strong metabolic activities and lacked dormancy initiation during seed maturation. Conclusion Transcriptome and WGCNA analyses revealed significant ABA-related changes in metabolic pathways and DEGs between vp5 and Vp5 during seed maturation. The results would provide insights for elucidating the molecular mechanism of ABA signaling and developing high dehydration tolerance maize suitable for mechanical harvesting.

Abscisic acid (ABA) is a “classical” plant hormone and is key to many plant responses, notably seed germination, transpiration and defence. It is becoming increasingly clear that ABA acts not just through the canonical PYL/PYR/RCAR receptors but also through other proteins that can interact specifically with ABA. Here we use genomic and transcriptomic resources to show that the human proteome also contains proteins with specific ABA-binding signatures and that some of these potential ABA-binding proteins may have roles in cancer and diabetes. In addition, there is evidence for the presence of ABA in humans; however, the source of it remains somewhat inconclusive. Here we propose an ABA synthesis pathway that, much like in fungi, does not include carotenoids but proceeds via farnesyl pyrophosphate. In summary, we review the current status of ABA research in Homo sapiens and propose avenues that might lead to novel insights into the synthesis and biological roles of this ancient hormone, e.g., in obesity and inflammation.

Nitric oxide (NO) has been reported to be involved in breaking seed dormancy but its mechanism of action is unclear. Here, we report that a rapid accumulation of NO induced an equally rapid decrease of abscisic acid (ABA) that is required for this action in Arabidopsis. Results of quantitative real-time polymerase chain reaction (QRT-PCR) and Western blotting indicate that the NO-induced ABA decrease correlates with the regulation of CYP707A2 transcription and (+)-abscisic acid 8'-hydroxylase (encoded by CYP707A2) protein expression. By analysing cyp707a1, cyp707a2 and cyp707a3 mutants, we found that CYP707A2 plays a major role in ABA catabolism during the first stage of imbibition. Fluorescent images demonstrate that NO is released rapidly in the early hours at the endosperm layer during imbibition. Evidently, such response precedes the enhancement of ABA catabolism which is required for subsequent seed germination.

Previous studies found that 5-aminolevulinic acid (ALA) and abscisic acid (ABA) can mitigate damage from adversity by enhancing photosynthesis. However, it is not clear whether they have positive effects on iron utilization and chlorophyll synthesis of tomato seedlings under low-temperature stress. To investigate the possible functional relationship between ABA and ALA and elucidate the possible mechanisms of action of ALA to alleviate low-temperature stress in tomato seedlings, this experiment analyzed the effects of ALA and ABA on chlorophyll synthesis in tomato seedling leaves sprayed with exogenous of ALA (25 mg·L−1) or ABA (100 µM) under low-temperature stress (8–18 °C/8–12 °C, day/night). The results show that exogenous ALA increased the Fv/Fm of tomato leaves by 5.31% and increased the accumulation of iron and chlorophyll by 101.15% and 15.18%, respectively, compared to the low-temperature treatment alone, and tomato resistance of low-temperature stress was enhanced. Meanwhile, exogenous application of ALA increased the ABA content by 39.43%, and subsequent application of exogenous ABA revealed that tomato seedlings showed similar effects to exogenous ALA under low-temperature stress, with increased accumulation of iron and chlorophyll in tomato seedlings, which eventually increased the maximum photochemical efficiency of PS II. Under low-temperature stress, application of exogenous ABA significantly reduced ALA content, but the expression of key enzyme genes (PPGD, HEMB1, HEME1, and HEMF1), precursors of chlorophyll synthesis by ALA, was significantly elevated, presumably because the increased activity of these enzymes after external application of ABA accelerated ALA consumption. In conclusion, ABA may crosstalk with ALA to improve the photochemical efficiency and low temperature resistance of tomatoes by regulating chlorophyll synthesis and iron accumulation.

Environmental extremes, such as drought and flooding, are becoming more common with global warming, resulting in significant crop losses. Understanding the mechanisms underlying the plant water stress response, regulated by the abscisic acid (ABA) pathway, is crucial to building resilience to climate change. Potted kiwifruit plants (two cultivars) were exposed to contrasting watering regimes (water logging and no water). Root and leaf tissues were sampled during the experiments to measure phytohormone levels and expression of ABA pathway genes. ABA increased significantly under drought conditions compared with the control and waterlogged plants. ABA-related gene responses were significantly greater in roots than leaves. ABA responsive genes, DREB2 and WRKY40, showed the greatest upregulation in roots with flooding, and the ABA biosynthesis gene, NCED3, with drought. Two ABA-catabolic genes, CYP707A i and ii were able to differentiate the water stress responses, with upregulation in flooding and downregulation in drought. This study has identified molecular markers and shown that water stress extremes induced strong phytohormone/ABA gene responses in the roots, which are the key site of water stress perception, supporting the theory kiwifruit plants regulate ABA to combat water stress.

BACKGROUND: It is becoming increasingly clear that stress and metabolic signalling networks interact and that this interaction is important in plant responses to herbivory, pathogen attack, drought, cold, heat and osmotic stresses including salinity. At the interface between these two major signalling systems are the hormone abscisic acid (ABA) and signalling factors including protein kinases and transcription factors. SCOPE: This briefing reviews links between ABA, stress and sugar signalling, focusing on the roles of sucrose non-fermenting-1-related protein kinases (SnRKs), SnRK1-activating protein kinases (SnAKs), calcium-dependent protein kinases (CDPKs) and ABA response element binding proteins (AREBPs, which are transcription factors). Links between stress and nitrogen / amino acid signalling are also described, including the roles of a protein kinase called general control non-derepressible (GCN)-2 in regulating protein synthesis through phosphorylation of the α-subunit of translation initiation factor-2 (eIF2α) in response not only to decreases in amino acid levels but also to a range of stresses. Evidence of a link between sugar and amino acid signalling is explored, with nitrate reductase being a target for regulation by both SnRK1 and GCN2 through different mechanisms; possible links between SnRK1 and GCN2 via a pathway including the protein kinase target of rapamycin (TOR)-1 are described. The significance of these interactions to the concept of signalling networks as opposed to simple cascades and pathways, and the importance of the subject in the context of the predicted increase in severity and range of stresses that plants will have to withstand as a result of global climate change are discussed.

NRT1/PTR FAMILY (NPF) proteins were originally identified as nitrate or di/tri-peptide transporters. Recent studies revealed that th is transporter family also transports the plant hormones auxin (indole-3-acetic acid), abscisic acid (ABA), and gibberellin (GA), as well as secondary metabolites ( glucosinolates). We developed modified yeast two-hybrid systems with receptor complexes for GA and jasmonoyl-isoleucine (JA-Ile), to detect GA and JA-Ile transport activities of proteins expressed in the yeast cells. Using these GA and JA-Ile systems as well as the ABA system that we had introduced previously, we determined the capacities of Arabidopsis NPFs to transport these hormones. Several NPFs induced the formation of receptor complexes under relatively low hormone concentrations. Hormone transport activities were confirmed for some NPFs by direct analysis of hormone uptake of yeast cells by liquid chromatography–tandem mass spectrometry. Our results suggest that at least some NPFs could function as hormone transporters.

2′,3′-iso-Benzoabscisic acid (iso-PhABA), an excellent selective abscisic acid (ABA) analog, was developed in our previous work. In order to find its more structure-activity information, some structural modifications were completed in this paper, including the substitution of phenyl ring and replacing the ring with heterocycles. Thus, 16 novel analogs of iso-PhABA were synthesized and screened with three bioassays, Arabidopsis and lettuce seed germination and rice seedling elongation. Some of them, i.e., 2′,3′-iso-pyridoabscisic acid (iso-PyABA) and 2′,3′-iso-franoabscisic acid (iso-FrABA), displayed good bioactivities that closed to iso-PhABA and natural (+)-ABA. Some others, for instance, substituted-iso-PhABA, exhibited certain selectivity to different physiological process when compared to iso-PhABA or (+)-ABA. These analogs not only provided new candidates of ABA-like synthetic plant growth regulators (PGRs) for practical application, but also new potential selective agonist/antagonist for probing the specific function of ABA receptors.

Most plants tolerate dehydration but not desiccation. Differences between dehydration and desiccation are defined based on physiological and molecular responses of desiccation-tolerant resurrection plants to dehydration. Abstract Due to the ability to tolerate extreme dehydration, desiccation-tolerant plants have been widely investigated to find potential approaches for improving water use efficiency or developing new crop varieties. The studies of desiccation-tolerant plants have identified sugar accumulation, specific protein synthesis, cell structure changes, and increased anti-oxidative reactions as part of the mechanisms of desiccation tolerance. However, plants respond differently according to the severity of water loss, and the process of water loss affects desiccation tolerance. A detailed analysis within the dehydration process is important for understanding the process of desiccation tolerance. This review defines dehydration and desiccation, finds the boundary for the relative water content between dehydration and desiccation, compares the molecular responses to dehydration and desiccation, compares signaling differences between dehydration and desiccation, and finally summarizes the strategies launched in desiccation-tolerant plants for dehydration and desiccation, respectively. The roles of abscisic acid (ABA) and reactive oxygen species (ROS) in sensing and signaling during dehydration are discussed. We outline how this knowledge can be exploited to generate drought-tolerant crop plants.