Abscisic Acid Metabolites Research Articles

Exogenous melatonin delays yellowing in postharvest broccoli by regulation of ABA and carotenoid metabolite

Yellowing is the first visible sign of floret senescence and quality deterioration in broccoli, mainly caused by chlorophyll degradation and carotenoid accumulation. In this study, the impacts of melatonin (MLT) treatment on anabolism, catabolism and storage of carotenoid in postharvest broccoli associated with ABA regulation were investigated at transcript and metabolic levels. Results showed that MLT treatment effectively repressed yellowing and senescence along with a decrease in respiration rate and ethylene emission, enhancing endogenous MLT and abscisic acid (ABA) levels. A total of 925 metabolites were differentially expressed between the control and MLT treatment, which were mainly classified into amino acids, sugars, lipids, flavonoids and others. Specific analysis revealed that MLT treatment decreased sugars, lipids, flavonoids, and aromatic amino acids, but increased aliphatic amino acids. Meanwhile, MLT treatment suppressed the expression levels of genes related to carotenoid anabolism (BoPSY, BoPDS, BoZDS, BoCRTISO, BoLCYB, BoVDE, and BoZEP) and storage (BoOR), but the genes involved in carotenoid catabolism (BoNCED2, BoNCED6, BoCCD1 and BoCCD7) were up-regulated, which could collectively result in a decrease in the levels of β-carotene and lutein and an increase in ABA level. Moreover, correlation analysis indicated that lutein content was positively correlated with BoVDE, BoPDS and BoZDS, and negatively correlated with ABA level. Thus, MLT treatment slowed down the yellowing of broccoli during storage, which might be ascribed to inhibiting the anabolism and storage of carotenoid and promoting carotenoid catabolism and ABA biosynthesis.

Expression pattern of candidate genes and their correlation with various metabolites of abscisic acid biosynthetic pathway under drought stress in rice

AbstractDrought hampers global rice production. Abscisic acid (ABA) plays versatile roles under different environmental stresses. While the link between drought and ABA is known, its effect on ABA biosynthesis genes and metabolites is unclear. This study explored the impact of drought on various metabolites, namely beta‐carotene, zeaxanthin, antheraxanthin, violaxanthin, neoxanthin, and candidate genes viz. zeaxanthin epoxidase (ZEP) and 9‐cis epoxycarotenoid dioxygenase (NCED) of ABA biosynthesis pathway in rice cultivars (N22 and IR64) at anthesis {65 DAT (Days after transplanting)} with different stress levels. In stressed plants, zeaxanthin significantly increased (92%), while the concentration of beta‐carotene, antheraxanthin, violaxanthin and neoxanthin decreased as drought stress progressed. The concentration of metabolites in roots was notably lower than in leaves in both genotypes. The ZEP expression was upregulated in roots (8.24‐fold) under drought stress. Among five NCED isoforms, NCED3 showed significant upregulation (7.29‐fold) in leaf and root tissue. NCED1 was significantly downregulated as stress progressed and was negatively correlated with ABA accumulation. NCED2, NCED4 and NCED5 showed no significant change in their expression. Drying and rolling of rice leaves was observed after imparting drought stress. The findings revealed that drought stress significantly influenced the expression of candidate genes and the concentration of metabolites of the ABA biosynthesis pathway. There was a significantly higher accumulation of ABA in N22 leaves (47%) and roots (30%) compared to IR64. The N22, a drought‐tolerant genotype, exhibited significantly higher concentrations of intermediates and demonstrated increased expression of ZEP and NCED3, potentially contributing to its resilience against drought.

Abscisic acid metabolism pathways differ between grapevine species, leaves, and roots during water deficit

Abscisic acid (ABA) metabolism is complex involving biosynthesis, conjugation, and catabolism. Differences in ABA metabolism (ABA, ABA-related metabolites, and transcripts) in response to water deficit (WD) were detected in leaves and roots of four Vitis species differing in drought tolerance: Vitis vinifera (Cabernet Sauvignon), Vitis champinii (Ramsey), Vitis riparia (Riparia Gloire), and Vitis vinifera x girdiana (SC2). Concentrations of ABA and ABA-related metabolites increased after moderate or severe WD depending on species, organ, and time. Differences in ABA, glycosylated-ABA, and ABA catabolite concentrations, as well as previously investigated related transcript abundances, revealed differences in ABA metabolism pathways among the species and organs. NCED3 was a key gene in the WD response of leaves and roots of all species. NCED3 transcript abundance and ABA concentration in drought-tolerant Ramsey increased earlier and to a greater extent than other species. These species provide informative genetic resources to study ABA metabolism and drought tolerance further.

Isolation and Characterization of 1-Hydroxy-2,6,6-trimethyl-4-oxo-2-cyclohexene-1-acetic Acid, a Metabolite in Bacterial Transformation of Abscisic Acid.

We report the discovery of a new abscisic acid (ABA) metabolite, found in the course of a mass spectrometric study of ABA metabolism by the rhizosphere bacterium Rhodococcus sp. P1Y. Analogue of (+)-ABA, enriched in tritium in the cyclohexene moiety, was fed in bacterial cells, and extracts containing radioactive metabolites were purified and analyzed to determine their structure. We obtained mass spectral fragmentation patterns and nuclear magnetic resonance spectra of a new metabolite of ABA identified as 1-hydroxy-2,6,6-trimethyl-4-oxo-2-cyclohexene-1-acetic acid, which we named rhodococcal acid (RA) and characterized using several other techniques. This metabolite is the second bacterial ABA degradation product in addition to dehydrovomifoliol that we described earlier. Taken together, these data reveal an unknown ABA catabolic pathway that begins with side chain disassembly, as opposed to the conversion of the cyclohexene moiety in plants. The role of ABA-utilizing bacteria in interactions with other microorganisms and plants is also discussed.

Changes in Abscisic Acid, Carbohydrate, and Glucosinolate Metabolites in Kimchi Cabbage Treated with Glutamic Acid Foliar Application under Extremely Low Temperature Conditions

Changes in Abscisic Acid, Carbohydrate, and Glucosinolate Metabolites in Kimchi Cabbage Treated with Glutamic Acid Foliar Application under Extremely Low Temperature Conditions

Arabidopsis NPF5.1 regulates ABA homeostasis and seed germination by mediating ABA uptake into the seed coat

ABSTRACT Abscisic acid (ABA) is a plant hormone that induces seed dormancy during seed development and inhibits seed germination after imbibition. Although ABA is synthesized in the seed coat (testa), endosperm, and embryo, the physiological roles of the hormone derived from each tissue are not fully understood. We found that the gene encoding an Arabidopsis ABA importer, NPF5.1, was expressed in the seed coat during seed development. Dry seeds of loss-of-function npf5.1 mutants contained significantly higher levels of dihydrophaseic acid (DPA), an inactive ABA metabolite, than the wild type. The npf5.1 mutant also had a slight increase in ABA content. An increase in DPA was prominent in the fraction containing the seed coat and endosperm. Seed germination of the npf5.1 mutant was similar to the wild type in the presence of ABA or the gibberellin biosynthesis inhibitor paclobutrazol. However, a mutation in NPF5.1 suppressed the paclobutrazol-resistant germination of npf4.6, a mutant impaired in an ABA importer expressed in the embryo. These results suggest that ABA uptake into the seed coat mediated by NPF5.1 is important for ABA homeostasis during seed development and for regulating seed germination.

Abscisic acid, carbohydrate, and Glucosinolate metabolite profiles in Kimchi cabbage treated with extremely high temperatures and chitosan foliar application

Chitosan can help enhance disease resistance in plants by thickening leaves and alleviating environmental stresses, such as excess light intensity and extremely high temperature by promoting physiological activity. This study evaluated the effects of chitosan foliar application on Kimchi cabbage under high temperature stress. Six treatments were conducted, combining three photo-/dark periods temperature levels (20/16 °C optimal; 28/24 °C moderately high; and 36/32 °C extremely high) with and without chitosan foliar application (0 and 200 mg∙L − 1). Chitosan foliar application treatment sprayed once at 42 days after transplanting, and then temperature treatment immediately after chitosan foliar application conducted for up to eight days. At eight days after treatment (DAT), the leaf contents of abscisic acid (ABA) metabolites, i.e., phaseic acid (PA), dihydrophaseic acid (DPA), and ABA glucose ester (ABA-GE), were higher with chitosan foliar application than without chitosan treatments under moderately high and extremely high temperature conditions. PA and DPA were present at higher levels than the other metabolites. At eight DAT, the glucose and fructose contents in Kimchi cabbage treated with chitosan foliar application were higher than in those without chitosan foliar application when plants were under the moderately high and extremely high temperature conditions. Glucosinolate metabolite (gluconapin, glucobrassicanapin, glucobrassicin, and 4-methoxyglucobrassicin) content was higher with chitosan foliar application than without chitosan foliar application under the extremely high temperature treatment. When exposed to extremely high temperature, chitosan foliar application mitigated the damage caused to Kimchi cabbage by high temperature stress. Overall, chitosan foliar application can alleviate the high temperature stress that can occur during the spring cultivation season in Kimchi cabbage, and the application of chitosan is therefore a feasible strategy for stabilizing production of Kimchi cabbage.

Abscisic acid implicated in differential plant responses of Phaseolus vulgaris during endophytic colonization by Metarhizium and pathogenic colonization by Fusarium

Metarhizium robertsii is an insect pathogen as well as an endophyte, and can antagonize the phytopathogen, Fusarium solani during bean colonization. However, plant immune responses to endophytic colonization by Metarhizium are largely unknown. We applied comprehensive plant hormone analysis, transcriptional expression and stomatal size analysis in order to examine plant immune responses to colonization by Metarhizium and/or Fusarium. The total amount of abscisic acid (ABA) and ABA metabolites decreased significantly in bean leaves by plant roots colonized by M. robertsii and increased significantly with F. solani compared to the un-inoculated control bean plant. Concomitantly, in comparison to the un-inoculated bean, root colonization by Metarhizium resulted in increased stomatal size in leaves and reduced stomatal size with Fusarium. Meanwhile, expression of plant immunity genes was repressed by Metarhizium and, alternately, triggered by Fusarium compared to the un-inoculated plant. Furthermore, exogenous application of ABA resulted in reduction of bean root colonization by Metarhizium but increased colonization by Fusarium compared to the control without ABA application. Our study suggested that ABA plays a central role in differential responses to endophytic colonization by Metarhizium and pathogenic colonization by Fusarium and, we also observed concomitant differences in stomatal size and expression of plant immunity genes.

Regulation mechanism of plant hormones on secondary metabolites

Plant hormones participate in the regulation of plant growth, and have significant physiological activities. Secondary metabolites are important raw materials of pharmaceutical and chemical industry, which have attracted extensive attention due to their economic and medicinal value. With the development of biotechnology, plant hormones have played an important role in regulating the synthesis of secondary metabolites. This paper mainly introduces the synthesis pathway, signal transduction mechanism and regulation of secondary metabolites of auxin, cytokinin, gibberellin, abscisic acid, ethylene, brassinosteroids and methyl jasmonate in plants. Researching the accumulation of secondary metabolites from a micro aspect is helpful to better understand the formation of plant hormones and their development in the process of secondary metabolism. In additionally, it provides a reference for the rational utilization of plant hormones and the scientific and efficient improvement of the production of secondary metabolites in plants.

Inhibition of Abscisic Acid 8′-Hydroxylase Affects Dehydration Tolerance and Root Formation in Cuttings of Grapes (Vitis labrusca L. × Vitis vinifera L. cv. Kyoho) Under Drought Stress Conditions

The effects of an inhibitor (Abz-E3M) of abscisic acid (ABA) 8′-hydroxylase, which is a primary enzyme of ABA catabolism, on dehydration tolerance and root formation in grape cuttings under drought conditions were investigated. Cuttings of ‘Kyoho’ grape (Vitis labrusca L. × Vitis vinifera L.) were sprayed with 100 μM of Abz-E3M and subjected to water deficit conditions at the stage when their first leaves fully expanded. The physiological and morphological changes in the leaves and basal portions of the cuttings were determined. In Abz-E3M-treated leaves, lower ABA metabolite and higher ABA and indole-3-acetic acid (IAA) concentrations were observed. Compared to the untreated control leaves, higher water potential was significantly maintained in Abz-E3M-treated leaves. Abz-E3M applications resulted in lower proline accumulation and 2,2-diphenyl-2-picrylhydrazyl radical scavenging activity in the leaves and led to enhanced dehydration tolerance. In addition, the percentage of rooted cuttings was significantly increased by Abz-E3M application. In the basal portion of Abz-E3M-treated cuttings, endogenous IAA concentrations and the gene expressions of VvARF6 and VvARF8, which are positive regulators of adventitious root formation, were significantly increased. Moreover, the expression levels of the negative regulator, VvARF17, were significantly lower. These results suggested that the inhibition of ABA 8′-hydroxylase enhanced dehydration tolerance and adventitious rooting and may be an effective strategy for achieving drought stress tolerance in grape cuttings.

Endogenous gibberellins and abscisic acid-metabolites: their role for during flower bud abscission and embryo development in pistachio

This study was carried out to determine the effect of different growth periods and possible role of gibberellins GAs and abscisic acid ABA metabolites the alternate bearing of the pistachio Pistacia vera L. . For this purpose, the levels of GAs and ABA in the panicles and nuts of the trees during flower bud abscission and embryo development were analyzed in the crop on year. The results showed significant differences and changes in ABA and GAs among the tissues and periods investigated. Dihydrophaseic acid DPA and GA19 were the dominant ABA and GAs in the pistachio concentrates analyzed in this work, respectively. The nut samples had higher values for almost all ABA metabolites and GAs than panicles. The ABA content of the panicles and nuts increased rapidly during flower development 35 DAFB prior to flower bud abscission while the initial decrease in the ABA content remained constant at a relatively low level at the end of June intense flower bud abscission , with the minimum levels being obtained during embryo development stage 65 DAFB . However, day 65 after full flowering, GA19 and GA44 were found to have increased. The plant growth regulator profiles of the pistachio showed delayed spikes in GA and ABA groups indicating that there is a hormone requirement during flower bud abscission and embryo development in pistachio. As a results, GA and ABA metabolites produced in different organs play an important role in the control of pistachios during embryo development and

PGPR Modulation of Secondary Metabolites in Tomato Infested with Spodoptera litura

The preceding climate change demonstrates overwintering of pathogens that lead to increased incidence of insects and pest attack. Integration of ecological and physiological/molecular approaches are imperative to encounter pathogen attack in order to enhance crop yield. The present study aimed to evaluate the effects of two plant growth promoting rhizobacteria (Bacillus endophyticus and Pseudomonas aeruginosa) on the plant physiology and production of the secondary metabolites in tomato plants infested with Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae). The surface sterilized seeds of tomato were inoculated with plant growth promoting rhizobacteria (PGPR) for 3–4 h prior to sowing. Tomato leaves at 6 to 7 branching stage were infested with S. litura at the larval stage of 2nd instar. Identification of secondary metabolites and phytohormones were made from tomato leaves using thin-layer chromatography (TLC) and high performance liquid chromatography (HPLC) and fourier-transform infrared spectroscopy (FTIR). Infestation with S. litura significantly decreased plant growth and yield. The PGPR inoculations alleviated the adverse effects of insect infestation on plant growth and fruit yield. An increased level of protein, proline and sugar contents and enhanced activity of superoxide dismutase (SOD) was noticed in infected tomato plants associated with PGPR. Moreover, p-kaempferol, rutin, caffeic acid, p-coumaric acid and flavonoid glycoside were also detected in PGPR inoculated infested plants. The FTIR spectra of the infected leaf samples pre-treated with PGPR revealed the presence of aldehyde. Additionally, significant amounts of indole-3-acetic acid (IAA), salicylic acid (SA) and abscisic acid (ABA) were detected in the leaf samples. From the present results, we conclude that PGPR can promote growth and yield of tomatoes under attack and help the host plant to combat infestation via modulation in IAA, SA, ABA and other secondary metabolites.

Transcriptome and Phytochemical Analysis Reveals the Alteration of Plant Hormones, Characteristic Metabolites, and Related Gene Expression in Tea (Camellia sinensis L.) Leaves During Withering.

Plant hormones play an important role in the chemical metabolism of postharvest plants. However, alterations in plant hormones of postharvest tea and their potential modulation of quality-related metabolites are unknown. In this study, the dynamic alterations of abscisic acid (ABA), salicylic acid (SA), jasmonic acid (JA), and critical metabolites, such as catechins, theanine, and caffeine, in tea leaves were analyzed during withering from 0 to 24 h. It was found that the ABA content increased from 0 to 9 h but decreased thereafter, JA continuously increased, and the SA content showed no significant change. With the exception of gallocatechin (GC) and epicatechin (EC), the amounts of other critical components were significantly reduced at 24 h. Transcriptome analysis showed that compared with 0 h, 2256, 3654, and 1275 differentially expressed genes (DEGs) were identified at 9, 15, and 24 h, respectively. For all comparisons, DEGs corresponding to the pathways of “phenylalanine, tyrosine, and tryptophan biosynthesis” and “phenylalanine metabolism”, involved in the biosynthesis of catechins, were significantly enriched. Weighted correlation network analysis (WGCNA) of co-expression genes indicated that many of the modules were only correlated with a specific trait during the withering process; the dark olive-green module, however, was correlated with two traits, ABA and theanine. Our study indicates that withering induced dramatic alterations in gene transcription as well as levels of hormones (ABA, JA, and SA) and important components, and that ABA regulated theanine metabolism during this process.

Plant growth promoting rhizobacteria (PGPR) confer drought resistance and stimulate biosynthesis of secondary metabolites in pennyroyal (Mentha pulegium L.) under water shortage condition

Water deficit is one of the main devastating environmental factors limiting crops productivity. Plant growth promoting rhizobacteria (PGPR) can improve plant growth in stress conditions and enhance plant tolerance to drought stress. The aim of this study was to investigate the role of PGPR to protect pennyroyal (Mentha pulegium L.) as an important industrial and functional plant against drought damages. The greenhouse study was conducted as a factorial experiment in a completely randomized design. The first factor was PGPR inoculation (Azotobacter chroococcum (Ac), Azospirillum brasilense (Ab), Ac + Ab and control (without PGPR)). The second factor was irrigation regime that applied at three levels: field capacity (FC), 0.7 FC and 0.4 FC. Drought stress significantly decreased chlorophyll fluorescence (Fv/Fm) and relative water content (RWC) of pennyroyal. Conversely, antioxidant enzymes activity, osmoprotectants accumulation, membrane lipid peroxidation, abscisic acid (ABA) and secondary metabolites including phenolic, flavonoid and essential oil contents and DPPH radical scavenging activity of the plant extract increased due to water deficit. PGPR inoculation significantly reduced adverse effects of water stress on physio- biochemical characteristics and secondary metabolites production in pennyroyal. The results indicated that the bacteria were different in their ability to enhance plant investigated characteristics, and co-inoculation of the bacteria was more effective on improving of pennyroyal physiological and phytochemical parameters. The highest ABA, proteins and soluble sugars, phenolic, flavonoid and oxygenated monoterpenes contents as well as DPPH radical scavenging activity were observed in the plants treated with Ac + Ab under severe drought stress.

Dormancy breaking in Fagus sylvatica seeds is linked to formation of abscisic acid-glucosyl ester

Seed dormancy is an adaptive mechanism that allows seed germination under suitable environmental conditions. Germination of stored dormant seeds proceeds after dormancy breaking induced by stratification. To improve understanding of dormancy breaking in beechnuts, we: investigated effects of moisture content and temperature during storage; analysed contents of abscisic acid, abscisic acid metabolites and indole-3-acetic acid in embryonic axes during storage and stratification; and histochemically localized storage proteins in embryogenic axes and cotyledons of beechnut embryos. The results show that storage conditions can affect the nuts’ abscisic acid contents, but not the stratification process. In addition, dormancy breaking is linked to a reduction in abscisic acid contents and depth of dormancy is not influenced by either of these storage factors. Detected changes that correlated most strongly with dormancy breaking were a big increase in abscisic acid-glucosyl ester levels and accompanying reduction in the abscisic acid-glucosyl ester to abscisic acid ratio. We detected extremely low concentrations of other abscisic acid metabolites-neophaseic, phaseic and dihydrophaseic acids—in non-dormant stored beechnuts, but somewhat higher concentrations during dormancy. No relationships between changes in indole-3-acetic acid levels with either storage conditions or dormancy breaking were detected. Changes in distributions of storage proteins were related to the seeds’ moisture content during storage and stratification rather than seed dormancy. We conclude that increases in endogenous abscisic acid-glucosyl ester levels and abscisic acid-glucosyl ester to abscisic acid ratios are good markers of depth of dormancy and/or effectiveness of stratification in beechnuts.

The biochemistry underpinning industrial seed technology and mechanical processing of sugar beet

Main conclusionSeed-processing technologies such as polishing and washing enhance crop seed quality by limited removal of the outer layers and by leaching. Combined, this removes chemical compounds that inhibit germination.Industrial processing to deliver high-quality commercial seed includes removing chemical inhibitors of germination, and is essential to produce fresh sprouts, achieve vigorous crop establishment, and high yield potential in the field. Sugar beet (Beta vulgaris subsp. vulgaris var. altissima Doell.), the main sugar source of the temperate agricultural zone, routinely undergoes several processing steps during seed production to improve germination performance and seedling growth. Germination assays and seedling phenotyping was carried out on unprocessed, and processed (polished and washed) sugar beet fruits. Pericarp-derived solutes, known to inhibit germination, were tested in germination assays and their osmolality and conductivity assessed (ions). Abscisic acid (ABA) and ABA metabolites were quantified in both the true seed and pericarp tissue using UPLC-ESI(+)-MS/MS. Physical changes in the pericarp structures were assessed using scanning electron microscopy (SEM). We found that polishing and washing of the sugar beet fruits both had a positive effect on germination performance and seedling phenotype, and when combined, this positive effect was stronger. The mechanical action of polishing removed the outer pericarp (fruit coat) tissue (parenchyma), leaving the inner tissue (sclerenchyma) unaltered, as revealed by SEM. Polishing as well as washing removed germination inhibitors from the pericarp, specifically, ABA, ABA metabolites, and ions. Understanding the biochemistry underpinning the effectiveness of these processing treatments is key to driving further innovations in commercial seed quality.

Transcriptome profiling analysis revealed co-regulation of multiple pathways in jujube during infection by ‘Candidatus Phytoplasma ziziphi’

BackgroundJujube witches' broom (JWB), caused by a phytoplasma, devastates jujube tree (Ziziphus jujuba) growth and production in Asia. Although host responses to phytoplasmas are studied at the phenotypic, physiological, biochemical and molecular levels, it remains unclear how a host plant responds at the molecular level during the primary stage of infection. MethodsTo understand the response of the jujube tree to JWB infection, leaves were sampled at different times during the phytoplasma infection. Transcriptomic analyses at six stages were performed to reveal how phytoplasma infection affects Chinese jujube gene expression through the determination of the key differentially expressed genes (DEGs), and their related pathways. Quantitative real-time PCR was applied to validate 10 differentially expressed genes at different JWB phytoplasma infection stages. ResultsA total of 25,067 unigenes were mapped to jujube genome reference sequences. In the first infection stage (0–2 weeks after grafting (WAG), a total of 582 jujube genes were differentially regulated but no visible symptoms appeared. Quite a few DEGs related to abscisic acid (ABA) and cytokinin (CTK) were down-regulated, while some related to jasmonic acid (JA) and salicylic acid (SA) were up-regulated, Genes related to plant-pathogen interaction were also differentially expressed. In the second infection stage (37–39WAG), witches' broom symptoms were visible, and a total of 4373 DEGs were identified. Genes involved in biosynthesis and signal transduction of ABA, brassinosteroid (BR), CTK, ethylene (ET), and auxin (IAA), GA, JA and SA, plant-pathogen interaction, flavonoid biosynthesis genes were significantly regulated, suggesting that jujube trees activated defense factors related to SA, JA, ABA and secondary metabolites to defend against phytoplasma infection. By the third infection stage (48–52WAG), serious symptoms occurred and 3386 DEGs were identified. Most DEGs involved in biosynthesis and signal transduction of JA, SA and GA were up-regulated, while those relating to ABA were down-regulated. Genes involved in plant-pathogen interaction were up- or down-regulated, while phenylpropanoid and flavonoid biosynthesis genes were significantly up-regulated. Meanwhile, DEGs involved in photosynthesis, chlorophyll and peroxisome biosynthesis, and carbohydrate metabolism were down-regulated. These results suggested that phytoplasma infection had completely destroyed jujube trees' defense system and had disturbed chlorophyll synthesis and photosynthetic activity in the infected leaves at the late stage, resulting in yellow leaves and other JWB symptoms. DiscussionThe results in this report suggested that phytohormone biosynthesis and signal transduction, photosynthesis, and secondary metabolism all played important roles in the battle between colonization and defense in the interaction between Ca. Phytoplasma ziziphi and jujube.

An UHPLC-MS/MS Method for Target Profiling of Stress-Related Phytohormones.

The methodology described here represents an improved strategy for analysis of a broad range of stress-related plant hormones including jasmonates, salicylic acid, abscisic acid, and auxin metabolites. The method conditions are optimized in order to reduce the background effect of complicated plant matrix, allow effective preconcentration and thus perform highly sensitive profiling of multiple plant hormones by ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS).

Abscisic Acid Related Metabolites in Sweet Cherry Buds (Prunus avium L.)

As our climate changes, plant mechanisms involved for dormancy release become increasingly important for commercial orchards. It is generally believed that abscisic acid (ABA) is a key hormone that responds to various environmental stresses which affects bud dormancy. For this reason, a multi-year study was initiated to obtain data on plant metabolites during winter rest and ontogenetic development in sweet cherry buds (Prunus avium L.). In this paper, we report on metabolites involved in ABA synthesis and catabolism and its effect on bud dormancy in the years 2014/15-2016/17. In previous work, the timings of the different phases of para-, endo-, ecodormancy and ontogenetic development for cherry flower buds of the cultivar ‘Summit’ were determined, based on classical climate chamber experiments and changes in the bud’s water content. Based on these time phases, we focused now on the different aspects of the ABA-metabolism. The results show that there is a continual synthesis of ABA about 5 weeks before leaf fall, and a degradation of ABA during ecodormancy and bud development until the phenological stage ‘open cluster’. This is confirmed by relating the ABA content to that of the total precursor carotenoids, neoxanthin and violaxanthin. The tentative monitoring of individual intermediate metabolites revealed that dihydroxyphaseic acid is the most abundant catabolite of ABA and ABA glucosyl ester is in terms of mass intensity, the most abundant ABA metabolite observed in this study. The results suggest that the direct route for ABA biosynthesis from farnesyl pyrophosphate may also be relevant in cherry flower buds.

Grape Ripening Is Regulated by Deficit Irrigation/Elevated Temperatures According to Cluster Position in the Canopy.

The impact of water deficit on berry quality has been extensively investigated during the last decades. Nonetheless, there is a scarcity of knowledge on the performance of varieties exposed to a combination of high temperatures/water stress during the growing season and under vineyard conditions. The objective of this research was to investigate the effects of two irrigation regimes, sustained deficit irrigation (SDI, 30% ETc) and regulated deficit irrigation (RDI, 15% ETc) and of two cluster positions within the canopy (east- and west-exposed sides) on berry ripening in red Aragonez (Tempranillo) grapevines. The study was undertaken for two successive years in a commercial vineyard in South Portugal, monitoring the following parameters: pre-dawn leaf water potential, berry temperature, sugars, polyphenols, abscisic acid (ABA) and related metabolites. Additionally, expression patterns for different transcripts encoding for enzymes responsible for anthocyanin and ABA biosynthesis (VviUFGT, VvNCED1, VvβG1, VviHyd1, VviHyd2) were analyzed. In both years anthocyanin concentration was lower in RDI at the west side (RDIW- the hottest one) from véraison onwards, suggesting that the most severe water stress conditions exacerbated the negative impact of high temperature on anthocyanin. The down-regulation of VviUFGT expression revealed a repression of the anthocyanin synthesis in berries of RDIW, at early stages of berry ripening. At full-maturation, anthocyanin degradation products were detected, being highest at RDIW. This suggests that the negative impact of water stress and high temperature on anthocyanins results from the repression of biosynthesis at the onset of ripening and from degradation at later stages. On the other hand, berries grown under SDI displayed a higher content in phenolics than those under RDI, pointing out for the attenuation of the negative temperature effects under SDI. Irrigation regime and berry position had small effect on free-ABA concentration. However, ABA catabolism/conjugation process and ABA biosynthetic pathway were affected by water and heat stresses. This indicates the role of ABA-GE and catabolites in berry ABA homeostasis under abiotic stresses. Principal component analysis (PCA) showed that the strongest influence in berry ripening is the deficit irrigation regime, while temperature is an important variable determining the improvement or impairment of berry quality by the deficit irrigation regime. In summary, this work shows the interaction between irrigation regime and high temperature on the control of berry ripening.