Phytohormone Abscisic Acid Research Articles

Biocompatible Abscisic Acid-Sensing Supramolecular Hybridization Probe for Spatiotemporal Fluorescence Imaging in Plant Tissues.

Achieving detection of the phytohormone abscisic acid (ABA) is of critical importance for understanding plant growth and development. We report a hybrid supramolecular fluorescent probe that uses bovine serum albumin (BSA) as a host. Aggregation-induced emission of fluorescent chromophores (AIEgens) enables luminescence in the presence of BSA. ABA and its aptamer act as a switch to trigger this fluorescent system, the strategy that exhibits high sensitivity to abscisic acid with a detection limit of 0.098 nM. The probe test strip also enables visualization of ABA content from plants by colorimetric observation with the naked eye. In particular, the high biocompatibility and small molecular size of the prepared fluorescent probe allow for effective monitoring of ABA in plant tissues by fluorescence imaging. This strategy provides a new perspective to achieve the detection of endogenous and exogenous ABA in plants and has important implications for plant biology research.

Structure-Based Modulation of the Ligand Sensitivity of a Tomato Dimeric Abscisic Acid Receptor Through a Glu to Asp Mutation in the Latch Loop.

The binding of the plant phytohormone Abscisic acid (ABA) to the family of ABA receptors (PYR/PYL/RCAR) triggers plant responses to abiotic stress. Thus, the implementation of genetic or chemical strategies to modulate PYR/PYL activity might be biotechnologically relevant. We have employed the available structural information on the PYR/PYL receptors to design SlPYL1, a tomato receptor, harboring a single point mutation that displays enhanced ABA dependent and independent activity. Interestingly, crystallographic studies show that this mutation is not directly involved in ABA recognition or in the downstream phosphatase (PP2C) inhibitory interaction, rather, molecular dynamic based ensemble refinement restrained by crystallographic data indicates that it enhances the conformational variability required for receptor activation and it is involved in the stabilization of an active form of the receptor. Moreover, structural studies on this receptor have led to the identification of niacin as an ABA antagonist molecule in vivo. We have found that niacin blocks the ABA binding site by mimicking ABA receptor interactions, and the niacin interaction inhibits the biochemical activity of the receptor.

Phytohormone abscisic acid ameliorates neuropathic pain via regulating LANCL2 protein abundance and glial activation at the spinal cord.

Spinal neuroinflammation plays a critical role in the genesis of neuropathic pain. Accumulating data suggest that abscisic acid (ABA), a phytohormone, regulates inflammatory processes in mammals. In this study, we found that reduction of the LANCL2 receptor protein but not the agonist ABA in the spinal cord is associated with the genesis of neuropathic pain. Systemic or intrathecal administration of ABA ameliorates the development and pre-existence of mechanical allodynia and heat hyperalgesia in animals with partial sciatic nerve ligation (pSNL). LANCL2 is expressed only in microglia in the spinal dorsal horn. Pre-emptive treatment with ABA attenuates activation of microglia and astrocytes, ERK activity, and TNFα protein abundance in the dorsal horn in rats with pSNL. These are accompanied by restoration of spinal LANCL2 protein abundance. Spinal knockdown of LANCL2 gene with siRNA recapitulates the behavioral and spinal molecular changes induced by pSNL. Activation of spinal toll-like receptor 4 (TLR4) with lipopolysaccharide leads to activation of microglia, and over production of TNFα, which are concurrently accompanied by suppression of protein levels of LANCL2 and peroxisome proliferator activated-receptor γ. These changes are ameliorated when ABA is added with LPS. The anti-inflammatory effects induced by ABA do not requires Gi protein activity. Our study reveals that the ABA/LANCL2 system is a powerful endogenous system regulating spinal neuroinflammation and nociceptive processing, suggesting the potential utility of ABA as the management of neuropathic pain.

Disentangling the Potato Tuber Moth-Induced Early-Defense Response by Simulated Herbivory in Potato Plants.

Plants rely on the perception of a multitude of herbivory-associated cues (HACs) to activate their defense response to insect herbivores. These stimuli are mainly derived from three functional components, namely, mechanical damage, insect-associated microbe, and insect’s chemical cues. While simulated herbivory integrating these stimuli is widely exploited for complementing actual herbivory in clarifying the details of plant–herbivore interaction, breaking down these stimuli and identifying the mechanisms of plant responses associated with them have been less explored. In this study, the components of potato tuber moth (Phthorimaea operculella, PTM) herbivory were reorganized in a cumulative way and their impacts on the early defense responses of potato leaf were characterized. We found that simulated and actual herbivory of PTM triggered similar patterns of phytohormonal and transcriptomic responses in potato leaf. Moreover, the microbe in the PTM herbivory stimuli is associated with the regulation of the phytohormones jasmonic acid (JA) and abscisic acid (ABA) since reducing the microbe in HAC could reduce JA while increasing ABA. In addition, seven robust gene modules were identified to illustrate how potato plants respond to different PTM herbivory stimuli when herbivory components increased. Significantly, we found that mechanical damage mainly activated JA-mediated signaling; PTM-derived HACs contributed much more to potato early-defense response and induced signaling molecules such as multiple protein kinases; orally secreted bacteria stimuli could antagonize PTM-derived HACs and modulate plant defense, including repressing phenylpropanoid biosynthesis. Our study broadened the understanding of how potato plants integrate the responses to a multitude of stimuli upon PTM herbivory and evidenced that insect-associated microbes greatly modulated the plants response to insect herbivory.

Abscisic acid facilitates phosphate acquisition through the transcription factor ABA INSENSITIVE5 in Arabidopsis

Low phosphate (LP) in soil is a common nutrient stress that severely restricts agricultural production, but the role, if any, of the major stress phytohormone abscisic acid (ABA) in plant phosphate (Pi) starvation responses remains elusive. Here, we report that LP-induced ABA accumulation promotes Pi uptake in an ABA INSENSITIVE5 (ABI5)-dependent manner in Arabidopsis thaliana. LP significantly activated plant ABA biosynthesis, metabolism, and stress responses, suggesting a role of ABA in the plant response to Pi availability. LP-induced ABA accumulation and expression of two major high-affinity phosphate transporter genes PHOSPHATE TRANSPORTER1;1/1;4 (PHT1;1/1;4) were severely impaired in a mutant lacking BETA-GLUCOSIDASE1 (BG1), which converts conjugated ABA to active ABA, and the mutant had shorter roots and less Pi content than wild-type plants under LP conditions. Moreover, a mutant of ABI5, which encodes a central transcription factor in ABA signaling, also exhibited suppressed root elongation and had reduced Pi content under LP conditions. ABI5 facilitated Pi acquisition by activating the expression of PHT1;1 by directly binding to its promoter, while overexpression of PHT1;1 completely rescued its Pi content under LP conditions. Together, our findings illustrate a molecular mechanism by which ABA positively modulates phosphate acquisition through ABI5 in the Arabidopsis response to phosphate deficiency.

Heat stress during grain filling regulates seed germination through alterations of DNA methylation in barley (Hordeum vulgare L.).

Alterations in DNA methylation levels of ROS, GA and ABA related gene promoters cause transcriptional changes upon imbibition to induce seed germination in barley seeds exposed to heat stress during grain filling. Environmental changes, especially changes in temperature, during seed development affect germination in several plant species. We have previously shown that heat stress during rice grain filling alters DNA methylation, an epigenetic mark important for gene silencing, regulates transcript levels of phytohormone metabolism genes, and delays seed germination. However, whether this phenomenon is present in other plant species remained to be elucidated. In this study, we compared seeds germination of barley (Hordeum vulgare L.) plants grown at 15°C (control) or 25°C (heat stress) during grain filling. Heat stress during grain filling significantly promoted seed germination in comparison with the control. The phytohormone gibberellic acid (GA) and reactive oxygen species produced by NADPH oxidases promote seed germination, whereas phytohormone abscisic acid (ABA) suppresses seed germination. We found that in heat-stressed seeds, genes related to ABA biosynthesis (HvNCED1 and 2) were significantly suppressed, whereas genes related to ABA catabolism (HvABA8'OH) and GA biosynthesis (HvHA20ox, HvGA3ox), and NADPH oxidase (HvRboh) genes were significantly upregulated after imbibition. Using MeDIP-qPCR, we showed that the promoters of HvNCED were hyper-methylated, and those of HvABA8'OH1, HvABA8'OH3, HvGA3ox2, and HvRbohF2 were hypo-methylated in heat treated seeds. Taken together, our data suggest that heat stress during grain filling affects DNA methylation of germination-related genes and promotes seed germination in barley.

Comprehensive Biochemical, Physiological, and Transcriptomic Analyses Provide Insights Into Floral Bud Dormancy in Rhododendron delavayi Franch.

Due to a scarcity of relevant data, the ornamental woody flower Rhododendron delavayi Franch. is examined in the current study for its low temperature-induced floral bud dormancy (late October–end December) aspect. This study used transcriptome data profiling and co-expression network analyses to identify the interplay between endogenous hormones and bud dormancy phases such as pre-dormancy, para-dormancy, endo-dormancy, eco-dormancy, and dormancy release. The biochemical and physiological assays revealed the significance of the abundance of phytohormones (abscisic acid, auxin, zeatin, and gibberellins), carbohydrate metabolism, oxidative species, and proteins (soluble proteins, proline, and malondialdehyde) in the regulatory mechanism of floral bud dormancy. The transcriptome sequencing generated 65,531 transcripts, out of which 504, 514, 307, and 240 expressed transcripts were mapped uniquely to pre-, para-, endo-, and eco-phases of dormancy, showing their roles in the stimulation of dormancy. The transcripts related to LEA29, PGM, SAUR family, RPL9e, ATRX, FLOWERING LOCUS T, SERK1, ABFs, ASR2, and GID1 were identified as potential structural genes involved in floral bud dormancy. The transcription factors, including Zinc fingers, CAD, MADS-box family, MYB, and MYC2, revealed their potential regulatory roles concerning floral bud dormancy. The gene co-expression analysis highlighted essential hub genes involved in cold stress adaptations encoding proteins, viz, SERPIN, HMA, PMEI, LEA_2, TRX, PSBT, and AMAT. We exposed the connection among low temperature-induced dormancy in floral buds, differentially expressed genes, and hub genes via strict screening steps to escalate the confidence in selected genes as being truly putative in the pathways regulating bud dormancy mechanism. The identified candidate genes may prove worthy of further in-depth studies on molecular mechanisms involved in floral bud dormancy of Rhododendron species.

Complete Genome Sequence Resource for Xanthomonas translucens pv. undulosa MAI5034, a Wheat Pathogen from Uruguay.

Complete Genome Sequence Resource for Xanthomonas translucens pv. undulosa MAI5034, a Wheat Pathogen from Uruguay.

BrABF3 promotes flowering through the direct activation of CONSTANS transcription in pak choi.

Drought stress triggers the accumulation of the phytohormone abscisic acid (ABA), which in turn activates the expression of the floral integrator gene CONSTANS (CO), accelerating flowering. However, the molecular mechanism of ABA-induced CO activation remains elusive. Here, we conducted a yeast one-hybrid assay using the CO promoter from Brassica campestris (syn. Brassica rapa) ssp. chinensis (pak choi) to screen the ABA-induced pak choi library and identified the transcription activator ABF3 (BrABF3). BrABF3, the expression of which was induced by ABA in pak choi, directly bound to the CO promoter from both pak choi and Arabidopsis. The BrABF3 promoter is specifically active in the Arabidopsis leaf vascular tissue, where CO is mainly expressed. Impaired BrABF3 expression in pak choi decreased BrCO expression levels and delayed flowering, whereas ectopic expression of BrABF3 in Arabidopsis increased CO expression and induced earlier flowering under the long-day conditions. Electrophoretic mobility shift assay analysis showed that BrABF3 was enriched at the canonical ABA-responsive element-ABRE binding factor (ABRE-ABF) binding motifs of the BrCO promoter. The direct binding of BrABF3 to the ABRE elements of CO was further confirmed by chromatin immunoprecipitation quantitative PCR. In addition, the induction of BrCO transcription by BrABF3 could be repressed by BrCDF1 in the morning. Thus, our results suggest that ABA could accelerate the floral transition by directly activating BrCO transcription through BrABF3 in pak choi.

Phytocytokine signalling reopens stomata in plant immunity and water loss.

Stomata exert considerable effects on global carbon and water cycles by mediating gas exchange and water vapour1,2. Stomatal closure prevents water loss in response to dehydration and limits pathogen entry3,4. However, prolonged stomatal closure reduces photosynthesis and transpiration and creates aqueous apoplasts that promote colonization by pathogens. How plants dynamically regulate stomatal reopening in a changing climate is unclear. Here we show that the secreted peptides SMALL PHYTOCYTOKINES REGULATING DEFENSE AND WATER LOSS (SCREWs) and the cognate receptor kinase PLANT SCREW UNRESPONSIVE RECEPTOR (NUT) counter-regulate phytohormone abscisic acid (ABA)- and microbe-associated molecular pattern (MAMP)-induced stomatal closure. SCREWs sensed by NUT function as immunomodulatory phytocytokines and recruit SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE (SERK) co-receptors to relay immune signalling. SCREWs trigger the NUT-dependent phosphorylation of ABA INSENSITIVE 1 (ABI1) and ABI2, which leads to an increase in the activity of ABI phosphatases towards OPEN STOMATA 1 (OST1)-a key kinase that mediates ABA- and MAMP-induced stomatal closure5,6-and a reduction in the activity of S-type anion channels. After induction by dehydration and pathogen infection, SCREW-NUT signalling promotes apoplastic water loss and disrupts microorganism-rich aqueous habitats to limit pathogen colonization. The SCREW-NUT system is widely distributed across land plants, which suggests that it has an important role in preventing uncontrolled stomatal closure caused by abiotic and biotic stresses to optimize plant fitness.

SORTING NEXIN2 proteins mediate stomatal movement and the response to drought stress by modulating trafficking and protein levels of the ABA exporter ABCG25.

The phytohormone abscisic acid (ABA) regulates ion channel activity and stomatal movement in response to drought stress. Cellular ABA levels change depending on cellular and environmental conditions via modulation of its biosynthesis, catabolism and transport. Although factors involved in ABA biosynthesis and degradation have been studied extensively, how ABA transporters are modulated to fine-tune ABA levels, especially under drought stress, remains elusive. Here, we show that Arabidopsis thaliana SORTING NEXIN 2 (SNX2) proteins play a critical role in endosomal trafficking of the ABA exporter ATP BINDING CASETTE G25 (ABCG25) via direct interaction at endosomes, leading to its degradation in the vacuole. In agreement, snx2a and snx2b mutant plants showed enhanced recycling of GFP-ABCG25 from early endosomes to the plasma membrane and higher accumulation of GFP-ABCG25. Phenotypically, snx2a and snx2b plants were highly sensitive to exogenous ABA and displayed enhanced ABA-mediated inhibition of inward K+ currents and ABA-mediated activation of slow anion currents in guard cells, resulting in an increased tolerance to drought stress. Based on these results, we propose that SNX2 proteins play a crucial role in stomatal movement and tolerance to drought stress by modulating the endosomal trafficking of ABCG25 and thus cellular ABA levels.

Divergence in the ABA gene regulatory network underlies differential growth control.

The phytohormone abscisic acid (ABA) is a central regulator of acclimation to environmental stress; however, its contribution to differences in stress tolerance between species is unclear. To establish a comparative framework for understanding how stress hormone signalling pathways diverge across species, we studied the growth response of four Brassicaceae species to ABA treatment and generated transcriptomic and DNA affinity purification and sequencing datasets to construct a cross-species gene regulatory network (GRN) for ABA. Comparison of genes bound directly by ABA-responsive element binding factors suggests that cis-factors are most important for determining the target loci represented in the ABA GRN of a particular species. Using this GRN, we reveal how rewiring of growth hormone subnetworks contributes to stark differences in the response to ABA in the extremophyte Schrenkiella parvula. Our study provides a model for understanding how divergence in gene regulation can lead to species-specific physiological outcomes in response to hormonal cues.

Plant Water Stress Reduces Aphid Performance: Exploring Mechanisms Driven by Water Stress Intensity

Drought alters plant traits in ways that affect herbivore performance. However, we lack a comprehensive understanding of the plant-derived mechanisms that mediate insect responses to drought. Water stress occurs along gradients of intensity, and the impacts of drought intensity on plant-insect interactions is understudied. Here, we assessed aphid performance on wheat plants exposed to a gradient of water stress and measured plant nutrients and phytohormones that may mediate aphid response to drought. We show that water stress reduced aphid performance, and the negative effect grew stronger as the magnitude of water stress increased. The plant response to water limitation was not consistent across the stress gradient and was reliant on the trait measured. Water limitation did not affect whole-plant nitrogen; however, water limitation did reduce amino acid concentration and increase sugars, but only under high stress intensity. The phytohormones abscisic acid (ABA), jasmonic acid (JA), and salicylic acid (SA), and the expression of their associated gene transcripts, were also differentially affected by water stress intensity. In well-watered conditions, aphid feeding increased concentrations of the defense-related hormones SA and JA over time; however, any amount of water limitation prevented aphid induction of JA. Although aphids may experience a reprieve from JA-related defenses in stressed conditions, SA levels remain high in response to aphid feeding, indicating aphids are still vulnerable to SA-related defenses. Any level of water stress also increased the expression of a callose-associated gene transcript, a physical defense that impairs feeding. Thus, poor aphid performance on mildly-stressed plants was correlated with increased plant defenses, whereas poor performance on highly-stressed plants was correlated with stronger plant defense induction and reduced plant nutritional quality. Understanding the mechanisms driving aphid and plant performance under water stress conditions can improve our ability to predict how aphid populations will respond to climate change.

Comparative Proteomics Combined with Morphophysiological Analysis Revealed Chilling Response Patterns in Two Contrasting Maize Genotypes.

Maize yield is significantly influenced by low temperature, particularly chilling stress at the maize seedling stage. Various physiological approaches have been established to resist chilling stress; however, the detailed proteins change patterns underlying the maize chilling stress response at the seedling stage remain unknown, preventing the development of breeding-based methods to resist chilling stress in maize. Thus, we performed comprehensive physiological, comparative proteomics and specific phytohormone abscisic acid (ABA) assay on different maize inbred lines (tolerant-line KR701 and sensitive-line hei8834) at different seedling stages (the first leaf stage and third leaf stage) under chilling stress. The results revealed several signalling proteins and pathways in response to chilling stress at the maize seedling stage. Meanwhile, we found ABA pathway was important for chilling resistance of tolerant-line KR701 at the first leaf stage. Related chilling-responsive proteins were further catalogued and analysed, providing a resource for further investigation and maize breeding.

In Dormant Red Rice Seeds, the Inhibition of Early Seedling Growth, but Not of Germination, Requires Extracellular ABA.

The phytohormone abscisic acid (ABA) inhibits seed germination and seedling growth and is required for the inception of dormancy. Xanthoxal (also known as xanthoxin) is the first specific biosynthetic precursor of ABA. In this study, a modified method to produce xanthoxal is described. I tested the ability of either xanthoxal or ABA to reinstate dormancy in dormant red rice seeds whose dormancy was broken by fluridone (an inhibitor of the synthesis of carotenoids and, subsequently, ABA). Xanthoxal was shown to have a stronger inhibitory effect on germination than ABA when exogenously provided. Although this could indicate an additional effect of xanthoxal above that expected if xanthoxal were simply converted to ABA in the seed, alternative hypotheses cannot be excluded. One alternative is that exogenous xanthoxal may be trapped inside the cells to a greater extent than exogenous ABA, resulting in an intracellular level of ABA higher than that reached with a direct application of ABA. As a further alternative, exogenous xanthoxal may interfere with ABA action in the apoplast. In this study, following germination, early seedling growth was delayed only if ABA was applied. This suggests that inhibition of early seedling growth, but not of germination, requires extracellular ABA.

Phytohormone abscisic acid elicits positive effects on harmaline-induced cognitive and motor disturbances in a rat model of essential tremor.

ObjectiveEssential tremor (ET) as a neurological disorder is accompanied by cognitive and motor disturbances. Despite the high incidence of ET, the drug treatment of ET remains unsatisfactory. Recently, abscisic acid (ABA) has been reported to have positive neurophysiological effects in mammals. Here, the effects of ABA on harmaline‐induced motor and cognitive impairments were investigated in rats.MethodsMale Wistar rats weighing 120–140 g were divided into control, harmaline (30 mg/kg, ip), ABA vehicle (DMSO+normal saline), and ABA (10 μg/rat, icv, 30 min before harmaline injection) groups. Exploratory, balance and motor performance, anxiety, and cognitive function were assessed using footprint, open field, wire grip, rotarod, and shuttle box tests.ResultsThe results indicated that ABA (10 μg/rat) can improve harmaline‐induced tremor in rats. The administration of ABA significantly increased time spent on wire grip and rotarod. In addition, ABA had a promising effect against the cognitive impairments induced by harmaline.ConclusionTaken together, ABA has positive effects on locomotor and cognitive impairments induced by tremor. However, further studies are required to determine the exact mechanisms of ABA on the ET.

The phytochrome interacting proteins ERF55 and ERF58 repress light-induced seed germination in Arabidopsis thaliana

Seed germination is a critical step in the life cycle of plants controlled by the phytohormones abscisic acid (ABA) and gibberellin (GA), and by phytochromes, an important class of photoreceptors in plants. Here we show that light-dependent germination is enhanced in mutants deficient in the AP2/ERF transcription factors ERF55 and ERF58. Light-activated phytochromes repress ERF55/ERF58 expression and directly bind ERF55/ERF58 to displace them from the promoter of PIF1 and SOM, genes encoding transcriptional regulators that prevent the completion of germination. The same mechanism controls the expression of genes that encode ABA or GA metabolic enzymes to decrease levels of ABA and possibly increase levels of GA. Interestingly, ERF55 and ERF58 are themselves under transcriptional control of ABA and GA, suggesting that they are part of a self-reinforcing signalling loop which controls the completion of germination. Overall, we identified a role of ERF55/ERF58 in phytochrome-mediated regulation of germination completion.

Cold stress tolerance of the intertidal red alga Neoporphyra haitanensis

BackgroundRed algae Porphyra sensu lato grow naturally in the unfavorable intertidal environment, in which they are exposed to substantial temperature fluctuations. The strategies of Porphyra to tolerate cold stress are poorly understood.ResultsHerein, investigations revealed that chilling and freezing induced alterations in the physiological properties, gene transcriptional profiles and metabolite levels in the economically important red algae species, Neoporphyra haitanensis. Control samples (kept at 20 °C) were compared to chilled thalli (10 and 4 °C) and to thalli under − 4 °C conditions. Chilling stress did not affect the health or photosynthetic efficiency of gametophytes, but freezing conditions resulted in the arrest of growth, death of some cells and a decrease in photosynthetic activity as calculated by Fv/Fm. Transcriptome sequencing analysis revealed that the photosynthetic system was down-regulated along with genes associated with carbon fixation and primary metabolic biosynthesis. Adaptive mechanisms included an increase in unsaturated fatty acids levels to improve membrane fluidity, an increase in floridoside and isofloridoside content to enhance osmotic resistance, and an elevation in levels of some resistance-associated phytohormones (abscisic acid, salicylic acid, and methyl jasmonic acid). These physiochemical alterations occurred together with the upregulation of ribosome biogenesis.ConclusionsN. haitanensis adopts multiple protective mechanisms to maintain homeostasis of cellular physiology in tolerance to cold stress.

The phytohormone abscisic acid modulates protein carbonylation in Arabidopsis thaliana.

Protein carbonylation is a post-translational modification associated with the reactive oxygen species. It results from the direct oxidation of the side chains of Lys, Arg, Pro, and Thr residues by hydroxyl radical HO• or the addition of reactive carbonyl species including α,β-unsaturated aldehydes and oxylipins to the side chain of Cys, His, and Lys. Recent findings indicated that the phytohormone abscisic acid (ABA) induces the production of α,β-unsaturated aldehydes that modulate the effect of ABA on stomatal closure. This indicated that α,β-unsaturated aldehydes might mediate ABA signaling. In this study, we investigated the ABA-induced protein carbonylation events by profiling the carbonylated proteome extracted from Arabidopsis thaliana leaves after ABA treatment. The carbonylated proteins were enriched by affinity chromatography and subjected to liquid chromatography-tandem mass spectrometry. We identified 180 carbonylated proteins. Of these, 26 proteins became carbonylated upon ABA treatment, whereas 163 proteins that were carbonylated in untreated samples were no longer detected in the ABA-treated samples, which points to dynamic control of protein carbonylation by ABA in A. thaliana. A few regulatory stress-related proteins and enzymes involved in the biosynthesis of the aspartate family of amino acids were overrepresented in the list of proteins, which the carbonylation status changed between untreated and ABA-treated samples. These results indicated that ABA triggers a change in the pattern of protein carbonylation in A. thaliana. This change is independent of the commonly seen increased levels of carbonylated proteins in the plants subjected to deadly stress conditions.

Exogenous abscisic acid regulates primary metabolism in postharvest cherry tomato fruit during ripening

Primary metabolites play crucial roles during fruit development and ripening. Phytohormone abscisic acid (ABA) has been reported to regulate postharvest tomato fruit ripening. However, knowledge about ABA in regulating primary metabolism in tomato fruit is obscure. In the present research, cherry tomato fruit were infiltrated with 1.0 mM ABA or deionized water under vacuum, and kept in darkness for 15 d. The changes of the relative contents of sugars, organic acids, and amino acids, as well as the expression levels of key genes involved in sugar and organic acid metabolisms, were analyzed. Results showed exogenous ABA accelerated tomato fruit ripening, accompanying with the enhanced changes of fruit color and firmness, the higher levels of respiration rate and ethylene production. Meanwhile, exogenous ABA enhanced the relative levels of some primary metabolites, such as glucose, lyxose and fructose; citric acid, citramalic acid, ascorbic acid and gluconic acid; also serine, pyroglutamic acid, GABA, glutamic acid, aspartic acid, asparagine and glutamine (1.69-3.25 folds). Furthermore, exogenous ABA stimulated the expression levels of most key genes (such as SPSs, SPP2, TIV1, Lins, SUSs, PPCs, MDH and CS) (log2 fold change ranged from 1.06 to 3.64). Results indicate ABA is systematically involved in the regulation of primary metabolism, which may provide valuable information for exploring technical means to improve tomato taste and flavor.