Abstract Abscisic Acid Research Articles

BdERF96 interacts with BdASR1 to specifically respond to drought and oxidative stress in Brachypodium distachyon

Abscisic acid-, stress-, ripening-induced (ASR) proteins are some of the most important small proteins involved in plant responses to abiotic stresses and hormone signals. Recently, BdASR1 was revealed to be upregulated in response to abiotic stresses and hormone treatments and regulate expression of stress-related genes and drought tolerance in tobacco plants. However, the biological and molecular functions of BdASR1 remain to be elucidated. Here, we isolated and characterized BdASR1-interacting protein using the yeast two-hybrid assay. The expression of the interaction protein, BdERF96, increased under drought and oxidative stress corresponding to the expression of BdASR1. Subcellular localization of BdERF96 was detected in the plasma membrane and nucleus. The interaction of BdASR1 and BdERF96 at the plasma membrane and nucleus was demonstrated using bimolecular fluorescence complementation analysis. The findings imply that BdERF96 in association with BdASR1 could play a role in the positive response to drought and oxidative stresses.

Abscisic acid enriched fig extract promotes insulin sensitivity by decreasing systemic inflammation and activating LANCL2 in skeletal muscle

Abscisic acid is a phytohormone found in fruits and vegetables and is endogenously produced in mammals. In humans and mice, lanthionine synthetase C-like 2 (LANCL2) has been characterized as the natural receptor for ABA. Herein, we characterize the efficacy of a fig fruit extract of ABA in promoting glycemic control. This ABA-enriched extract, at 0.125 µg ABA/kg body weight, improves glucose tolerance, insulin sensitivity and fasting blood glucose in diet-induced obesity (DIO) and db/db mouse models. In addition to decreasing systemic inflammation and providing glycemic control without increasing insulin, ABA extract modulates the metabolic activity of muscle. ABA increases expression of important glycogen synthase, glucose, fatty acid and mitochondrial metabolism genes and increases direct measures of fatty acid oxidation, glucose oxidation and metabolic flexibility in soleus muscle cells from ABA-treated mice with DIO. Glycolytic and mitochondrial ATP production were increased in ABA-treated human myotubes. Further, ABA synergized with insulin to dramatically increase the rate of glycogen synthesis. The loss of LANCL2 in skeletal muscle abrogated the effect of ABA extract in the DIO model and increased fasting blood glucose levels. This data further supports the clinical development of ABA in the treatment of pre-diabetes, type 2 diabetes and metabolic syndrome.

A Clathrin-Related Protein, SCD2/RRP1, Participates in Abscisic Acid Signaling in Arabidopsis.

Abscisic acid (ABA) plays important roles in many aspects of plant growth and development, and responses to diverse stresses. Although much progress has been made in understanding the molecular mechanisms of ABA homoeostasis and signaling, the mechanism by which plant cells integrate ABA trafficking and signaling to regulate plant developmental processes is poorly understood. In this study, we used Arabidopsis STOMATAL CYTOKINESIS DEFECTIVE 2/RIPENING-REGULATED PROTEIN 1 (SCD2/RRP1) mutants and overexpression plants, in combination with transcriptome and protein-interaction assays, to investigate SCD2/RRP1 involvement in the integration of ABA trafficking and signaling in seed germination and seedling growth. Manipulation of SCD2/RRP1 expression affected ABA sensitivity in seed germination and seedling growth, as well as transcription of several ABA transporter genes and ABA content. RNA-sequencing analysis of Arabidopsis transgenic mutants suggested that SCD2/RRP1 was associated with ABA signaling via a type 2C protein phosphatase (PP2C) protein. The N- and C-terminal regions of SCD2/RRP1 separately interacted with both PYRABACTIN RESISTANCE 1 (PYR1) and ABA INSENSITIVE 1 (ABI1) on the plasma membrane, and SCD2/RRP1 acted genetically upstream of ABI1. Interestingly, ABA inhibited the interaction of SCD2/RRP1 with ABI1, but did not affect the interaction of SCD2/RRP1 with PYR1. These results suggested that in Arabidopsis SCD2/RRP1participates in early seed development and growth potentially through clathrin-mediated endocytosis- and clathrin-coated vesicle-mediated ABA trafficking and signaling. These findings provide insight into the mechanism by which cells regulate plant developmental processes through ABA.

Functional analysis of SlNCED1 in pistil development and fruit set in tomato (Solanum lycopersicum L.)

Abscisic acid (ABA) is an important regulator of many plant developmental processes, although its regulation in the pistil during anthesis is unclear. We investigated the role of 9-cis-epoxycarotenoid dioxygenase (SlNCED1), a key ABA biosynthesis enzyme, through overexpression and transcriptome analysis in the tomato pistil. During pistil development, ABA accumulates and SlNCED1 expression increases continually, peaking one day before full bloom, when the maximum amount of ethylene is released in the pistil. ABA accumulation and SlNCED1 expression in the ovary remained high for three days before and after full bloom, but then both declined rapidly four days after full bloom following senescence and petal abscission and expansion of the young fruits. Overexpression of SlNCED1 significantly increased ABA levels and also up-regulated SlPP2C5 expression, which reduced ABA signaling activity. Overexpression of SlNCED1 caused up-regulation of pistil-specific Zinc finger transcription factor genes SlC3H29, SlC3H66, and SlC3HC4, which may have affected the expression of SlNCED1-mediated pistil development-related genes, causing major changes in ovary development. Increased ABA levels are due to SlNCED1 overexpresson which caused a hormonal imbalance resulting in the growth of parthenocarpic fruit. Our results indicate that SlNCED1 plays a crucial role in the regulation of ovary/pistil development and fruit set.

Effect of a Novel Ficus Carica (Fig) Fruit Extract Standardized in Abscisic Acid on the Glycemic and Insulinemic Responses in Healthy Human Subjects

Abscisic acid (ABA) is a phyto-hormone present in different fruits and has important implications for human health, such as glucose homeostasis, increase of glucose tolerance, insulinemia attenuation, immune and anti-inflammatory functions. Fig extracts represent an important source of ABA and have therefore the potential to provide a natural balance for sugar and insulin control. The objective of this study was to determine the acute postprandial metabolic response on glycemia and insulinemia of standardized fig extracts (ABAlifeTM). Healthy subjects (n=10) consumed a glucose solution and a fig extract at two different concentrations Reference food: Glucose solution (50 g) in 250 mL of water. Test food 1: Glucose solution + 200 mg ABAlife (80 µg ABA) in 250 mL of water. Test food 2: Glucose solution + 100 mg ABAlife (40 µg ABA) in 250 mL of water. The results showed that the addition of ABAlife extracts to a glucose solution was able to reduce considerably both the glycemic index (GI) and insulinemic index (II) values. Fig Extract (100-200 mg) produced lower peak and overall glycemic and insulinemic responses, between 30-120 minutes, compared with reference food of glucose. The supplementation of Fig Extract (200 mg) to a glucose solution was able to produce considerable reductions of the GI and II values (25%, p<0.001 and 24%, p<0.05, respectively). Moreover, a dose response reduction of II was observed with both ABAlife extracts. Therefore, small amounts of ABA from ABAlife extracts could be proposed as an interesting strategy to reduce postprandial glucose and insulin responses and ABA potential to manage glucose metabolism disorders should be investigated in further chronic clinical trials. Disclosure A. Zangara: Employee; Self; Euromed.

The Assay of Abscisic Acid-Induced Stomatal Movement in Leaf Senescence.

Abscisic acid (ABA) is a sesquiterpenoid (15-carbon) hormone that comprehensively regulates plant stress responses, development, and senescence. Stomata are epidermal pores on plant surface used for exchanging gases such as carbon dioxide, water vapor, and oxygen. One of the mechanisms that ABA regulates leaf senescence is to control stomatal movement and thus water loss during leaf senescence. Here we describe the procedure of measuring stomatal movement in response to ABA treatments, which will provide a useful protocol to investigate ABA signaling in leaf senescence.

VvWRKY13 enhances ABA biosynthesis in Vitis vinifera

Abscisic acid (ABA) plays critical roles in plant growth and development as well as in plants’ responses to abiotic stresses. We previously isolated VvWRKY13, a novel transcription factor, from <em>Vitis vinifera</em> (grapevine), and here we present evidence that VvWRKY13 may regulate ABA biosynthesis in plants. When <em>VvWRKY13</em> was ectopically expressed in <em>Arabidopsis</em>, the transgenic lines showed delayed seed germination, smaller stomatal aperture size, and several other phenotypic changes, indicating elevated ABA levels in these plants. Sequence analysis of several genes that are involved in grapevine ABA synthetic pathway identified WRKY-specific binding elements (W-box or W-like box) in the promoter regions. Indeed, transient overexpression of <em>VvWRKY13</em> in grapevine leaves significantly increased the transcript levels of ABA synthetic pathway genes. Taken together, we conclude that VvWRKY13 may promote ABA production by activating genes in the ABA synthetic pathway.

Identification and characterization of the abscisic acid (ABA) receptor gene family and its expression in response to hormones in the rubber tree

Abscisic acid (ABA) is an essential phytohormone involved in diverse physiological processes. Although genome-wide analyses of the ABA receptor PYR/PYL/RCAR (PYL) protein/gene family have been performed in certain plant species, little is known about the ABA receptor protein/gene family in the rubber tree (Hevea brasiliensis). In this study, we identified 14 ABA receptor PYL proteins/genes (designated HbPYL1 through HbPYL14) in the most recent rubber tree genome. A phylogenetic tree was constructed, which demonstrated that HbPYLs can be divided into three subfamilies that correlate well with the corresponding Arabidopsis subfamilies. Eight HbPYLs are highly expressed in laticifers. Five of the eight genes are simultaneously regulated by ABA, jasmonic acid (JA) and ethylene (ET). The identification and characterization of HbPYLs should enable us to further understand the role of ABA signal in the rubber tree.

ABA is required for the accumulation of APX1 and MBF1c during a combination of water deficit and heat stress.

Abscisic acid (ABA) plays a key role in plant acclimation to abiotic stress. Although recent studies suggested that ABA could also be important for plant acclimation to a combination of abiotic stresses, its role in this response is currently unknown. Here we studied the response of mutants impaired in ABA signalling (abi1-1) and biosynthesis (aba1-1) to a combination of water deficit and heat stress. Both mutants displayed reduced growth, biomass, and survival when subjected to stress combination. Focusing on abi1-1, we found that although its stomata had an impaired response to water deficit, remaining significantly more open than wild type, its stomatal aperture was surprisingly reduced when subjected to the stress combination. Stomatal closure during stress combination in abi1-1 was accompanied by higher levels of H2O2 in leaves, suggesting that H2O2 might play a role in this response. In contrast to the almost wild-type stomatal closure phenotype of abi1-1 during stress combination, the accumulation of ascorbate peroxidase 1 and multiprotein bridging factor 1c proteins, required for acclimation to a combination of water deficit and heat stress, was significantly reduced in abi1-1 Our findings reveal a key function for ABA in regulating the accumulation of essential proteins during a combination of water deficit and heat stress.

Cloning and characterization of a novel Gladiolus hybridus AFP family gene (GhAFP-like) related to corm dormancy

Abscisic acid (ABA) is an important phytohormone controlling seed dormancy. AFPs (ABA INSENSITIVE FIVE BINDING PROTEINS) are reported to be negative regulators of the ABA signaling pathway. The involvement of AFPs in dormant vegetative organs remains poorly understood. Here, we isolated and characterized a novel AFP family member from Gladiolus dormant cormels, GhAFP-like, containing three conserved domains of the AFP family. Quantitative PCR analysis revealed that GhAFP-like was expressed in dormant organs and its expression was down-regulated along with corm storage. GhAFP-like was verified to be a nuclear-localized protein. Overexpressing GhAFP-like in Arabidopsis thaliana not only showed weaker seed dormancy with insensitivity to ABA, but also changed the expression of some ABA related genes. In addition, a primary root elongation assay showed GhAFP-like may involve in auxin signaling response. The results in this study indicate that GhAFP-like acts as a negative regulator in ABA signaling and is related to dormancy.

Plant MAPK cascades: Just rapid signaling modules?

Abscisic acid (ABA) is a major phytohormone mediating important stress-related processes. We recently unveiled an ABA-activated MAPK signaling module constituted of MAP3K17/18-MKK3-MPK1/2/7/14. Unlike classical rapid MAPK activation, we showed that the activation of the new MAPK module is delayed and relies on the MAP3K protein synthesis. In this addendum, we discuss the role of this original and unexpected activation mechanism of MAPK cascades which suggests that MAPKs can regulate both early and long-term plant stress responses.

Abscisic acid inhibits germination and indirectly delays ethylene biosynthesis of Beta vulgaris

Ethylene and abscisic acid (ABA) are known to interact during the germination of several species. However, ethylene is not involved during the germination of Beta vulgaris, questioning a possible interaction with ABA. Our results have shown that ABA delays the germination of B. vulgaris in a concentration-dependent manner. By analysing the ethylene biosynthesis pathway, the ethylene release rate was shown to be delayed when ABA is supplemented, most probably due to the slower germination rate. The inverse interaction in which 1-aminocyclopropane-1-carboxylic acid (ACC) affects ABA levels does not seem to occur in B. vulgaris as no changes in ABA content were observed during germination in the presence of ACC at different concentrations. Levels of certain plant growth regulators (ABA, ACC and auxin) were also shown to be much higher in the fruit pericarp compared with the true seed. Presumably the pericarp plays an important role during the germination process of B. vulgaris because it is a physiochemical boundary with drastic differences in hormone levels. Our results clearly show demonstrate that ethylene is not involved during the actual germination of B. vulgaris, and that there is no effect of ethylene on ABA during germination of B. vulgaris.

ECOPHYSIOLOGICAL RESPONSE TO WATER STRESS AND REGULATION OF GENE EXPRESSION FOR A 9-CIS-EPOXYCAROTENOID DIOXYGENASE IN VITIS VINIFERA L. 'ITALIA'

Abscisic acid (ABA) is associated with regulating plant adaptive responses to various environmental stresses. In particular, drought stress signals are transmitted through at least two pathways: one is abscisic acid (ABA)-dependent, and the other is ABA-independent. In the first case, drought stress increases the cellular ABA levels, which induces the expression of drought stress-responsive genes, such as 9-cis-epoxycarotenoid dioxygenase (NCED) and zeaxanthin epoxidase (ZEP). These genes belong to the carotenoid biosynthesis scenario. To date, most research of grapevines has focused on the physiological mechanisms of ABA during fruit ripening. Our interest is on studying the role of NCED and ZEP genes as candidate genes exhibiting up-regulation upon drought-stressed conditions. At the same time, several plant physiological parameters, such as leaf water status (?l), net assimilation rate (A), stomatal conductance (gs), transpiration rate (E), and soil water potential (?s), were monitored. To explain the complex molecular pattern undergoing these physiological changes, we investigated the levels of expression of one candidate gene encoding for VvNCED1. The results provided evidence of a different transcriptional pattern of the gene between the control and stressed plants, leading to a major accumulation of NCED1 transcripts in the stressed plants.

Cautionary Notes on the Usage of abi1-2 and abi1-3 Mutants of Arabidopsis ABI1 for Functional Studies.

Abscisic acid (ABA) is a key hormone involved in plant growth and development, as well as stress adaptation. Recently, a core ABA signal pathway was proposed in which the ABA receptor proteins (PYR/PYL/RCAR) bind and inhibit type 2C protein phosphatases (PP2Cs) in the presence of ABA, which in turn releases the SnRK2s kinases, and the phosphorylated SnRK2s accumulate and subsequently phosphorylate the ABA-responsive element binding factors (Melcher et al., 2009; Cutler et al., 2010).

The ongoing story: the mitochondria pyruvate carrier 1 in plant stress response in Arabidopsis

Abscisic acid (ABA) is an important regulator of guard cell ion channels and stomatal movements in response to drought stress. Pyruvate is the final product of glycolysis in the cytosol, and could be transported by mitochondrial pyruvate carriers (MPCs) into mitochondrion for consequent cellular substance and energy metabolism. We recently characterized the first putative mitochondrial pyruvate carrier, NRGA1, in planta, and found that this small protein is involved in the negative regulation of drought and ABA induced guard cell signaling in Arabidopsis thaliana. The findings revealed a probable link between mitochondrial pyruvate transport and guard cell signaling. It has also been shown that NRGA1 protein product was directed to the mitochondria, and co-expression of MPC1 and NRGA1 functionally complement the absence of a native pyruvate transport protein in yeast. Here, we further demonstrated that MPC1 showed similar sub-cellular localization pattern to NRGA1. Quantitative RT-PCR analysis showed that the transcription of both NRGA1 and MPC1 were induced by pyruvate or ABA, and pyruvate strengthened the ABA induced transcription of these 2 genes. The similarity in subcellular localization and gene expression to ABA strongly suggests that MPC1 may associate with NRGA1 for mitochondrial pyruvate transport and is involved in ABA mediated stomatal movements in Arabidopsis.

Chemicals to induce plastid signals in Arabidopsis seedlings

Tetrapyrroles and abscisic acid (ABA) were considered as plastid signal molecules for plant cells. However, they attract hot controversies. High levels of sugars also trigger plastid signals to regulate nuclear gene expression. However, the effective concentrations of sugar are extremely high (100–10,000 times of tetrapyrroles). To resolve these controversies and inconsistencies, we investigated which chemicals at what concentrations may work as plastid signal molecules, and summarize their common chemical structures. We found that they can be classified into two categories: (1) tetrapyrroles or other carbon–nitrogen heterocyclic compounds with an adjacent three-membered ring (two of them may be incomplete), with a signaling impact order: Mg–protoporphyrin IX/ABA>Fe–protoporphyrin IX>Zn–protoporphyrin IX>protoporphyrin IX>tryptophan>histidine. The completeness of the rings with a chelated metal ion has a positive effect on the effectiveness of plastid signaling stimulation. (2) Sugar or other carbon–oxygen (sulfur) five- or six-membered ring compounds, such as cyclohexane and thiophene. The effective concentrations of the second category of signal molecules are very high (about 400 mM for the monosaccharide). The two types of signal molecules are possibly perceived by different receptors in the plastid.

Accumulation of class-III type of boiling stable Peroxidases in response to plant growth hormone ABA in Triticum aestivum cultivars

Abscisic acid (ABA) is a key plant growth and stress hormone involved in many biological processes. It has been shown to be involved in Reactive Oxygen Species (ROS) generation. Class-III Peroxidases (PODs) are known to maintain oxidative stress induced-ROS at sub-lethal levels in plants under abiotic stress conditions, but, studies documenting how ABA regulates boiling stable class-III PODs are still a matter of conjuncture. In this study, the ABA-induced changes on ROS and ROS scavenging class III boiling stable POD were studied in the embryos of different cultivars of wheat. Simultaneous analysis of ROS contents, activities of ROS-scavenging class- III boiling stable POD enzymes gave an integrative view of physiological state and detoxifying potential under conditions of sensitivity and tolerance. Indices of oxidative stress viz., superoxide radical and H 2 O 2 content increased under ABA treatment in a genotype dependent manner. It was observed that cultivars :PBW 550, HD 2967 and PBW 621 have more efficient mechanism to scavenge ROS species as shown by increase in BsPOD activity accompanied by enhanced expression of boiling stable POD isoenzymes. Based on results it can be inferred that embryos of cvs. PBW 550, HD 2967 and PBW 621 have more capacity to perform biological antioxidative reactions to combat ABA-induced oxidative stress.

INFLUENCE OF ABSCISIC ACID AND OXYGEN SUPPLY ON GERMINATION OF MORE OR LESS DORMANT APPLE EMBRYOS

ABSTRACT Abscisic acid (ABA) inhibits the germination of dormant and non-dormant apple embryos irrespective of the oxygen level in the atmosphere. In some cases, this inhibition is partially reversible, even with dormant embryos. ABA proved to be effective on germination sensu stricto as well as on the growth of the embryonic axis.

A novel abi5 allele reveals the importance of the conserved Ala in the C3 domain for regulation of downstream genes and salt tolerance during germination in Arabidopsis

Abscisic acid (ABA) signal transduction during Arabidopsis seed development and germination requires a Group A bZIP transcription factor encoded by ABA INSENSITIVE5 (ABI5). In addition to the basic leucine zipper DNA binding domain, Group A bZIPs are characterized by three N-terminal conserved regions (C1, C2 and C3) and one C-terminal conserved region (C4). These conserved regions are considered to play roles in ABI5 functions; however, except for the phosphorylation site, the importance of the highly conserved amino acids is unclear. Here, we report a novel abi5 recessive allele (abi5-9) that encodes an intact ABI5 protein with one amino acid substitution (A214G) in the C3 domain. The abi5-9 plants showed ABA insensitivity during germination and could germinate on medium containing 175 mM NaCl or 500 mM mannitol. Em1 and Em6—both encoding late embryogenesis abundant (LEA) proteins and directly targeted by ABI5 regulation—were expressed at very low levels in abi5-9 plants compared with the wild type. In yeast, the abi5-9 protein exhibited greatly reduced interaction with ABI3 compared with ABI5. These data suggest that Ala214 in ABI5 contributes to the function of ABI5 via its interaction with ABI3.

Tissue culture of medicinal plant and abscisic acid

Abscisic acid (ABA) plays a key role in many physiological processes of plants, and it was also applied to fields of medicinal plant biotechnology. The article presents a review of some recent application of ABA in enhancing the production of secondary metabolites of medicinal plants, improving the in vitro conservation in medicinal plant tissue culture system.