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Sample records for abscissic acid aba

  1. Abscission: Role of Abscisic Acid

    PubMed Central

    Cracker, L. E.; Abeles, F. B.

    1969-01-01

    The effect of abscisic acid on cotton (Gossypium hirsutum L. cv. Acala 4-42) and bean (Phaseolus vulgaris L. cv. Red Kidney) explants was 2-fold. It increased ethylene production from the explants, which was found to account for some of its ability to accelerate abscission. Absci is acid also increased the activity of cellulase. Increased synthesis of cellulase was not du to an increase in aging of the explants but rather was an effect of abscisic acid on the processes that lead to cellulase synthesis or activity. PMID:16657181

  2. Leaf Abscission Induced by Ethylene in Water-Stressed Intact Seedlings of Cleopatra Mandarin Requires Previous Abscisic Acid Accumulation in Roots.

    PubMed

    Gomez-Cadenas, A.; Tadeo, F. R.; Talon, M.; Primo-Millo, E.

    1996-09-01

    The involvement of abscisic acid (ABA) in the process of leaf abscission induced by 1-aminocyclopropane-1-carboxylic acid (ACC) transported from roots to shoots in Cleopatra mandarin (Citrus reshni Hort. ex Tan.) seedlings grown under water stress was studied using norflurazon (NF). Water stress induced both ABA (24-fold) and ACC (16-fold) accumulation in roots and arrested xylem flow. Leaf bulk ABA also increased (8-fold), although leaf abscission did not occur. Shortly after rehydration, root ABA and ACC returned to their prestress levels, whereas sharp and transitory increases of ACC (17-fold) and ethylene (10-fold) in leaves and high percentages of abscission (up to 47%) were observed. NF suppressed the ABA and ACC accumulation induced by water stress in roots and the sharp increases of ACC and ethylene observed after rewatering in leaves. NF also reduced leaf abscission (7-10%). These results indicate that water stress induces root ABA accumulation and that this is required for the process of leaf abscission to occur. It was also shown that exogenous ABA increases ACC levels in roots but not in leaves. Collectively, the data suggest that ABA, the primary sensitive signal to water stress, modulates the levels of ethylene, which is the hormonal activator of leaf abscission. This assumption implies that root ACC levels are correlated with root ABA amounts in a dependent way, which eventually links water status to an adequate, protective response such as leaf abscission.

  3. Involvement of Abscisic Acid in Ethylene-Induced Cotyledon Abscission in Cotton Seedlings.

    PubMed Central

    Suttle, J. C.; Hultstrand, J. F.

    1993-01-01

    Cotton (Gossypium hirsutum L. cv LG102) seedlings raised from seeds exposed to 100 [mu]M norflurazon (NFZ) during imbibition contained reduced levels of free abscisic acid (ABA) and were visibly achlorophyllous. Exposure of untreated cotton seedlings to ethylene concentrations >1 [mu]L/L for 24 h resulted in cotyledon abscission. In contrast, exposure of NFZ-treated seedlings to concentrations of ethylene [less than or equal to]50 [mu]L/L elicited no cotyledon abscission. Application of ABA, an ABA analog, or jasmonic acid to NFZ-treated seedlings restored ethylene-induced abscission. Isolated cotyledonary node explants prepared from NFZ-treated seedlings exhibited an altered dose-response pattern of ethylene-induced petiole abscission. Endogenous levels of free IAA were unaltered in NFZ-treated seedlings. Ethylene treatment (50 [mu]L/L, 24 h) had no effect on free indoleacetic acid (IAA) levels in either control or NFZ-treated seedlings. Levels of conjugated (ester plus amide) IAA were substantially increased in NFZ-treated seedlings regardless of ethylene treatment. These results indicate that endogenous ABA plays an essential, but physiologically undefined, role in ethylene-induced cotyledon abscission in cotton. PMID:12231720

  4. Early Induction of Apple Fruitlet Abscission Is Characterized by an Increase of Both Isoprene Emission and Abscisic Acid Content12[W][OA

    PubMed Central

    Giulia, Eccher; Alessandro, Botton; Mariano, Dimauro; Andrea, Boschetti; Benedetto, Ruperti; Angelo, Ramina

    2013-01-01

    Apple (Malus domestica) fruitlet abscission represents an interesting model system to study the early phases of the shedding process, during which major transcriptomic changes and metabolic rearrangements occur within the fruit. In apple, the drop of fruits at different positions within the cluster can be selectively magnified through chemical thinners, such as benzyladenine and metamitron, acting as abscission enhancers. In this study, different abscission potentials were obtained within the apple fruitlet population by means of the above-cited thinners. A metabolomic study was conducted on the volatile organic compounds emitted by abscising fruitlets, allowing for identification of isoprene as an early marker of abscission induction. A strong correlation was also observed between isoprene production and abscisic acid (ABA) levels in the fruit cortex, which were shown to increase in abscising fruitlets with respect to nonabscising ones. Transcriptomic evidence indicated that abscission-related ABA is biologically active, and its increased biosynthesis is associated with the induction of a specific ABA-responsive 9-cis-epoxycarotenoid dioxygenase gene. According to a hypothetical model, ABA may transiently cooperate with other hormones and secondary messengers in the generation of an intrafruit signal leading to the downstream activation of the abscission zone. The shedding process therefore appears to be triggered by multiple interdependent pathways, whose fine regulation, exerted within a very short temporal window by both endogenous and exogenous factors, determines the final destiny of the fruitlets. PMID:23444344

  5. Abscissic acid localization by light microscopic immunohistochemistry in Chenopodium polyspermum L. Effect of water stress.

    PubMed

    Sotta, B; Sossountzov, L; Maldiney, R; Sabbagh, I; Tachon, P; Miginiac, E

    1985-03-01

    An indirect immunohistochemical technique was developed using a rabbit anti-abscissic acid (ABA) serum and the soluble peroxidase-antiperoxidase (PAP) complex for the localization of endogenous ABA in the aerial parts of Chenopodium. Terminal bud, axillary bud bearing nodes, and adult leaves were prefixed by a soluble carbodiimide to obtain the coupling of ABA on cellular proteins and postfixed by a conventional mixture of aldehydes. They were then embedded in paraffin or in plastic. Numerous controls were carried out on sections and on a model system to test the validity of the technique. Based on the staining patterns observed along the plant, an apico-basal gradient of ABA was revealed. In the older buds, ABA was mainly concentrated in the quiescent meristematic cells of the apex. Phloem cells of the main axis and chloroplasts of the leaves were specifically labeled. No reaction product was visualized in the parenchyma cells or in the cambial zone. Water stress, which is known to increase ABA content, induced an increase of immunoreactivity within the same compartments. This physiological test validates the stain.

  6. Effect of abscissic acid on tobacco mosaic virus.

    PubMed

    Mishra, M D; Ghosh, A; Verma, V S; Dattagupta, M

    1983-01-01

    Abscisic acid (ABA) did not affect the infectivity of tobacco mosaic virus (TMV) in vitro. The same dilutions of ABA when applied on the leaves of Chenopodium amaranticolor Coste and Reyn. at different intervals before inoculation affected development of local lesions variably at different dilutions. The inhibition of local lesion formation was reduced at other intervals leading to stimulation at thirty minutes and six hours intervals. Post-inoculation treatments with 2 mg/l of ABA gave stimulation of local lesion formation, though other dilutions gave inhibition. Viral concentration was stimulated in the tomato seedlings root dipped in 0.2 mg/l of ABA for 6 hours and inoculated 24 hours after transplantation. Incorporation of different concentrations of ABA into tissue culture medium reduced the growth of the TMV infected tobacco callus tissue and stimulated the infectivity of the tissue grown over it assayed after three weeks.

  7. Changes in Free and Conjugated Indole 3-Acetic Acid and Abscisic Acid in Young Cotton Fruits and Their Abscission Zones in Relation to Fruit Retention during and after Moisture Stress

    PubMed Central

    Guinn, Gene; Brummett, Donald L.

    1988-01-01

    Experiments were conducted with field-grown cotton (Gossypium hirsutum L.) in 1985 and 1986 to determine effects of water deficit on levels of conjugated indole 3-acetic acid (IAA) and abscisic acid (ABA) in young fruits (bolls) and their abscission zones in relation to boll retention. Tissues were harvested three times during an irrigation cycle in 1985. They were harvested twice during an irrigation cycle and once after irrigation in 1986 to determine extent of recoveries of measured parameters. As reported earlier, the free IAA content of abscission zones decreased with moisture stress. Irrigation caused a partial recovery in free IAA content of abscission zones and caused a partial recovery in rate of boll retention. In contrast to free IAA, conjugated IAA increased with water deficit, both in 3-day-old bolls and in their abscission zones. Bolls contained much more ester IAA than their abscission zones. Some, but not all, of the increase in ester IAA in bolls during moisture stress could have come from a conversion of amide-linked IAA. Amide IAA decreased slightly during stress and increased after irrigation, but the concentration was low relative to ester IAA. Free and conjugated ABA both increased during stress and decreased after irrigation. However, the concentration of conjugated ABA remained relatively high in abscission zones. Ester IAA, being more resistant than free IAA to enzymic destruction during stress, may hasten recovery of fruit retention after relief of stress by providing a source of free IAA in abscission zones to inhibit continued abscission. PMID:16665881

  8. Biological control of bacterial wilt in Arabidopsis thaliana involves abscissic acid signalling.

    PubMed

    Feng, Dong Xin; Tasset, Céline; Hanemian, Mathieu; Barlet, Xavier; Hu, Jian; Trémousaygue, Dominique; Deslandes, Laurent; Marco, Yves

    2012-06-01

    Means to control bacterial wilt caused by the phytopathogenic root bacteria Ralstonia solanacearum are limited. Mutants in a large cluster of genes (hrp) involved in the pathogenicity of R. solanacearum were successfully used in a previous study as endophytic biocontrol agents in challenge inoculation experiments on tomato. However, the molecular mechanisms controlling this resistance remained unknown. We developed a protection assay using Arabidopsis thaliana as a model plant and analyzed the events underlying the biological control by genetic, transcriptomic and molecular approaches. High protection rates associated with a significant decrease in the multiplication of R. solanacearum were observed in plants pre-inoculated with a ΔhrpB mutant strain. Neither salicylic acid, nor jasmonic acid/ethylene played a role in the establishment of this resistance. Microarray analysis showed that 26% of the up-regulated genes in protected plants are involved in the biosynthesis and signalling of abscissic acid (ABA). In addition 21% of these genes are constitutively expressed in the irregular xylem cellulose synthase mutants (irx), which present a high level of resistance to R. solanacearum. We propose that inoculation with the ΔhrpB mutant strain generates a hostile environment for subsequent plant colonization by a virulent strain of R. solanacearum.

  9. New Clothes for the Jasmonic Acid Receptor COI1: Delayed Abscission, Meristem Arrest and Apical Dominance

    PubMed Central

    Kim, Joonyup; Dotson, Bradley; Rey, Camila; Lindsey, Joshua; Bleecker, Anthony B.; Binder, Brad M.; Patterson, Sara E.

    2013-01-01

    In a screen for delayed floral organ abscission in Arabidopsis, we have identified a novel mutant of CORONATINE INSENSITIVE 1 (COI1), the F-box protein that has been shown to be the jasmonic acid (JA) co-receptor. While JA has been shown to have an important role in senescence, root development, pollen dehiscence and defense responses, there has been little focus on its critical role in floral organ abscission. Abscission, or the detachment of organs from the main body of a plant, is an essential process during plant development and a unique type of cell separation regulated by endogenous and exogenous signals. Previous studies have indicated that auxin and ethylene are major plant hormones regulating abscission; and here we show that regulation of floral organ abscission is also controlled by jasmonic acid in Arabidopsis thaliana. Our characterization of coi1-1 and a novel allele (coi1-37) has also revealed an essential role in apical dominance and floral meristem arrest. In this study we provide genetic evidence indicating that delayed abscission 4 (dab4-1) is allelic to coi1-1 and that meristem arrest and apical dominance appear to be evolutionarily divergent functions for COI1 that are governed in an ecotype-dependent manner. Further characterizations of ethylene and JA responses of dab4-1/coi1-37 also provide new information suggesting separate pathways for ethylene and JA that control both floral organ abscission and hypocotyl growth in young seedlings. Our study opens the door revealing new roles for JA and its interaction with other hormones during plant development. PMID:23573263

  10. Abscisic acid (ABA) regulates grape bud dormancy, and dormancy release stimuli may act through modification of ABA metabolism

    PubMed Central

    Zheng, Chuanlin; Halaly, Tamar; Acheampong, Atiako Kwame; Takebayashi, Yumiko; Jikumaru, Yusuke; Kamiya, Yuji; Or, Etti

    2015-01-01

    In warm-winter regions, induction of dormancy release by hydrogen cyanamide (HC) is mandatory for commercial table grape production. Induction of respiratory stress by HC leads to dormancy release via an uncharacterized biochemical cascade that could reveal the mechanism underlying this phenomenon. Previous studies proposed a central role for abscisic acid (ABA) in the repression of bud meristem activity, and suggested its removal as a critical step in the HC-induced cascade. In the current study, support for these assumptions was sought. The data show that ABA indeed inhibits dormancy release in grape (Vitis vinifera) buds and attenuates the advancing effect of HC. However, HC-dependent recovery was detected, and was affected by dormancy status. HC reduced VvXERICO and VvNCED transcript levels and induced levels of VvABA8’OH homologues. Regulation of these central players in ABA metabolism correlated with decreased ABA and increased ABA catabolite levels in HC-treated buds. Interestingly, an inhibitor of ethylene signalling attenuated these effects of HC on ABA metabolism. HC also modulated the expression of ABA signalling regulators, in a manner that supports a decreased ABA level and response. Taken together, the data support HC-induced removal of ABA-mediated repression via regulation of ABA metabolism and signalling. Expression profiling during the natural dormancy cycle revealed that at maximal dormancy, the HC-regulated VvNCED1 transcript level starts to drop. In parallel, levels of VvA8H-CYP707A4 transcript and ABA catabolites increase sharply. This may provide initial support for the involvement of ABA metabolism also in the execution of natural dormancy. PMID:25560179

  11. Flower abscission in Vitis vinifera L. triggered by gibberellic acid and shade discloses differences in the underlying metabolic pathways

    PubMed Central

    Domingos, Sara; Scafidi, Pietro; Cardoso, Vania; Leitao, Antonio E.; Di Lorenzo, Rosario; Oliveira, Cristina M.; Goulao, Luis F.

    2015-01-01

    Understanding abscission is both a biological and an agronomic challenge. Flower abscission induced independently by shade and gibberellic acid (GAc) sprays was monitored in grapevine (Vitis vinifera L.) growing under a soilless greenhouse system during two seasonal growing conditions, in an early and late production cycle. Physiological and metabolic changes triggered by each of the two distinct stimuli were determined. Environmental conditions exerted a significant effect on fruit set as showed by the higher natural drop rate recorded in the late production cycle with respect to the early cycle. Shade and GAc treatments increased the percentage of flower drop compared to the control, and at a similar degree, during the late production cycle. The reduction of leaf gas exchanges under shade conditions was not observed in GAc treated vines. The metabolic profile assessed in samples collected during the late cycle differently affected primary and secondary metabolisms and showed that most of the treatment-resulting variations occurred in opposite trends in inflorescences unbalanced in either hormonal or energy deficit abscission-inducing signals. Particularly concerning carbohydrates metabolism, sucrose, glucose, tricarboxylic acid metabolites and intermediates of the raffinose family oligosaccharides pathway were lower in shaded and higher in GAc samples. Altered oxidative stress remediation mechanisms and indolacetic acid (IAA) concentration were identified as abscission signatures common to both stimuli. According to the global analysis performed, we report that grape flower abscission mechanisms triggered by GAc application and C-starvation are not based on the same metabolic pathways. PMID:26157448

  12. Ethylene Evolution following Treatment with 1-Aminocyclopropane-1-carboxylic Acid and Ethephon in an in Vitro Olive Shoot System in Relation to Leaf Abscission

    PubMed Central

    Lavee, S.; Martin, George C.

    1981-01-01

    1-Aminocyclopropane-1-carboxylic acid (ACC) supplied via the cut base of detached olive shoots caused a burst of ethylene from leaves, but other cyclopropanes tested did not exhibit this effect. Ethephon (ET) and another ethylene-releasing compound caused a prolonged increase in ethylene evolution. ACC had only a very limited effect on leaf abscission regardless of concentration, whereas shoots placed with cut bases in ET for 60 to 80 minutes exhibited 100% leaf abscission within 90 hours. Shoots with inflorescences treated with ET just prior to anthesis began to wilt in vitro within 20 to 30 hours and failed to exhibit leaf abscission. At earlier stages of development, ET induced more leaf abscission on reproductive shoots than on vegetative shoots. It is suggested that the duration of ethylene evolution from the leaves governs their potential for abscission and that bursts of ethylene evolution even though large in amount may not induce abscission. Images PMID:16661837

  13. Abscisic acid metabolizing rhizobacteria decrease ABA concentrations in planta and alter plant growth.

    PubMed

    Belimov, Andrey A; Dodd, Ian C; Safronova, Vera I; Dumova, Valentina A; Shaposhnikov, Alexander I; Ladatko, Alexander G; Davies, William J

    2014-01-01

    Although endogenous phytohormones such as abscisic acid (ABA) regulate root growth, and many rhizobacteria can modulate root phytohormone status, hitherto there have been no reports of rhizobacteria mediating root ABA concentrations and growth by metabolising ABA. Using a selective ABA-supplemented medium, two bacterial strains were isolated from the rhizosphere of rice (Oryza sativa) seedlings grown in sod-podzolic soil and assigned to Rhodococcus sp. P1Y and Novosphingobium sp. P6W using partial 16S rRNA gene sequencing and phenotypic patterns by the GEN III MicroPlate test. Although strain P6W had more rapid growth in ABA-supplemented media than strain P1Y, both could utilize ABA as a sole carbon source in batch culture. When rice seeds were germinated on filter paper in association with bacteria, root ABA concentration was not affected, but shoot ABA concentration of inoculated plants decreased by 14% (strain P6W) and 22% (strain P1Y). When tomato (Solanum lycopersicum) genotypes differing in ABA biosynthesis (ABA deficient mutants flacca - flc, and notabilis - not and the wild-type cv. Ailsa Craig, WT) were grown in gnotobiotic cultures on nutrient solution agar, rhizobacterial inoculation decreased root and/or leaf ABA concentrations, depending on plant and bacteria genotypes. Strain P6W inhibited primary root elongation of all genotypes, but increased leaf biomass of WT plants. In WT plants treated with silver ions that inhibit ethylene perception, both ABA-metabolising strains significantly decreased root ABA concentration, and strain P6W decreased leaf ABA concentration. Since these changes in ABA status also occurred in plants that were not treated with silver, it suggests that ethylene was probably not involved in regulating bacteria-mediated changes in ABA concentration. Correlations between plant growth and ABA concentrations in planta suggest that ABA-metabolising rhizobacteria may stimulate growth via an ABA-dependent mechanism.

  14. Effects of high night temperature and abscisic acid (ABA) on rice (Oryza sativa L.) physiology

    Technology Transfer Automated Retrieval System (TEKTRAN)

    High night temperature (HNT) is known to decrease rice yields. The impact of abscisic acid (ABA) on plants has been the subject of many studies. However, little or no work has been carried out on rice response to ABA under HNT-stress conditions. This study determined the effects of ABA on rice leaf ...

  15. Local root abscisic acid (ABA) accumulation depends on the spatial distribution of soil moisture in potato: implications for ABA signalling under heterogeneous soil drying

    PubMed Central

    Puértolas, Jaime; Conesa, María R.; Ballester, Carlos; Dodd, Ian C.

    2015-01-01

    Patterns of root abscisic acid (ABA) accumulation ([ABA]root), root water potential (Ψroot), and root water uptake (RWU), and their impact on xylem sap ABA concentration ([X-ABA]) were measured under vertical partial root-zone drying (VPRD, upper compartment dry, lower compartment wet) and horizontal partial root-zone drying (HPRD, two lateral compartments: one dry, the other wet) of potato (Solanum tuberosum L.). When water was withheld from the dry compartment for 0–10 d, RWU and Ψroot were similarly lower in the dry compartment when soil volumetric water content dropped below 0.22cm3 cm–3 for both spatial distributions of soil moisture. However, [ABA]root increased in response to decreasing Ψroot in the dry compartment only for HPRD, resulting in much higher ABA accumulation than in VPRD. The position of the sampled roots (~4cm closer to the surface in the dry compartment of VPRD than in HPRD) might account for this difference, since older (upper) roots may accumulate less ABA in response to decreased Ψroot than younger (deeper) roots. This would explain differences in root ABA accumulation patterns under vertical and horizontal soil moisture gradients reported in the literature. In our experiment, these differences in root ABA accumulation did not influence [X-ABA], since the RWU fraction (and thus ABA export to shoots) from the dry compartment dramatically decreased simultaneously with any increase in [ABA]root. Thus, HPRD might better trigger a long-distance ABA signal than VPRD under conditions allowing simultaneous high [ABA]root and relatively high RWU fraction. PMID:25547916

  16. Local root abscisic acid (ABA) accumulation depends on the spatial distribution of soil moisture in potato: implications for ABA signalling under heterogeneous soil drying.

    PubMed

    Puértolas, Jaime; Conesa, María R; Ballester, Carlos; Dodd, Ian C

    2015-04-01

    Patterns of root abscisic acid (ABA) accumulation ([ABA]root), root water potential (Ψroot), and root water uptake (RWU), and their impact on xylem sap ABA concentration ([X-ABA]) were measured under vertical partial root-zone drying (VPRD, upper compartment dry, lower compartment wet) and horizontal partial root-zone drying (HPRD, two lateral compartments: one dry, the other wet) of potato (Solanum tuberosum L.). When water was withheld from the dry compartment for 0-10 d, RWU and Ψroot were similarly lower in the dry compartment when soil volumetric water content dropped below 0.22cm(3) cm(-3) for both spatial distributions of soil moisture. However, [ABA]root increased in response to decreasing Ψroot in the dry compartment only for HPRD, resulting in much higher ABA accumulation than in VPRD. The position of the sampled roots (~4cm closer to the surface in the dry compartment of VPRD than in HPRD) might account for this difference, since older (upper) roots may accumulate less ABA in response to decreased Ψroot than younger (deeper) roots. This would explain differences in root ABA accumulation patterns under vertical and horizontal soil moisture gradients reported in the literature. In our experiment, these differences in root ABA accumulation did not influence [X-ABA], since the RWU fraction (and thus ABA export to shoots) from the dry compartment dramatically decreased simultaneously with any increase in [ABA]root. Thus, HPRD might better trigger a long-distance ABA signal than VPRD under conditions allowing simultaneous high [ABA]root and relatively high RWU fraction.

  17. 1-Aminocyclopropane-1-Carboxylic Acid Transported from Roots to Shoots Promotes Leaf Abscission in Cleopatra Mandarin (Citrus reshni Hort. ex Tan.) Seedlings Rehydrated after Water Stress.

    PubMed

    Tudela, D; Primo-Millo, E

    1992-09-01

    The effect of water stress and subsequent rehydration on 1-aminocyclopropane-1-carboxylic acid (ACC) content, ACC synthase activity, ethylene production, and leaf abscission was studied in Cleopatra mandarin (Citrus reshni Hort. ex Tan.) seedlings. Leaf abscission occurred when drought-stressed plants were allowed to rehydrate, whereas no abscission was observed in plants under water stress conditions. In roots of water-stressed plants, a high ACC accumulation and an increase in ACC synthase activity were observed. Neither increase in ACC content nor significant ethylene production were detected in leaves of water-stressed plants. After rehydration, a sharp rise in ACC content and ethylene production was observed in leaves of water-stressed plants. Content of ACC in xylem fluid was 10-fold higher in plants rehydrated for 2 h after water stress than in nonstressed plants. Leaf abscission induced by rehydration after drought stress was inhibited when roots or shoots were treated before water stress with aminooxyacetic acid (AOA, inhibitor of ACC synthase) or cobalt ion (inhibitor of ethylene-forming enzyme), respectively. However, AOA treatments to shoots did not suppress leaf abscission. The data indicate that water stress promotes ACC synthesis in roots of Cleopatra mandarin seedlings. Rehydration of plants results in ACC transport to the shoots, where it is oxidized to ethylene. Subsequently, this ethylene induces leaf abscission.

  18. Abscisic acid (ABA) receptors: light at the end of the tunnel

    PubMed Central

    McCormick, Sheila

    2010-01-01

    The plant hormone abscisic acid (ABA) plays a role in several aspects of plant growth and development. Understanding how this hormonal stimulus is sensed and transduced turned out to be one of the major tasks in the field of plant signaling. A series of recent papers proposed several different proteins that could receive the ABA signal and initiate the signaling cascade. The winner appears to be PYR/PYL/RCAR (PYrabactin Resistance/PYrabactin Resistance-Like/Regulatory Component of Abscisic acid Receptor) proteins, as crystal structures were recently published. The crystal structures support the idea that upon ABA binding to a PYR/PYL/RCAR protein, the activity of a phosphatase 2C, with known repressive activity on ABA signaling, is inhibited. PMID:20948817

  19. The Dynamics of Embolism Refilling in Abscisic Acid (ABA)-Deficient Tomato Plants

    PubMed Central

    Secchi, Francesca; Perrone, Irene; Chitarra, Walter; Zwieniecka, Anna K.; Lovisolo, Claudio; Zwieniecki, Maciej A.

    2013-01-01

    Plants are in danger of embolism formation in xylem vessels when the balance between water transport capacity and transpirational demand is compromised. To maintain this delicate balance, plants must regulate the rate of transpiration and, if necessary, restore water transport in embolized vessels. Abscisic acid (ABA) is the dominant long-distance signal responsible for plant response to stress, and it is possible that it plays a role in the embolism/refilling cycle. To test this idea, a temporal analysis of embolism and refilling dynamics, transpiration rate and starch content was performed on ABA-deficient mutant tomato plants. ABA-deficient mutants were more vulnerable to embolism formation than wild-type plants, and application of exogenous ABA had no effect on vulnerability. However, mutant plants treated with exogenous ABA had lower stomatal conductance and reduced starch content in the xylem parenchyma cells. The lower starch content could have an indirect effect on the plant’s refilling activity. The results confirm that plants with high starch content (moderately stressed mutant plants) were more likely to recover from loss of water transport capacity than plants with low starch content (mutant plants with application of exogenous ABA) or plants experiencing severe water stress. This study demonstrates that ABA most likely does not play any direct role in embolism refilling, but through the modulation of carbohydrate content, it could influence the plant’s capacity for refilling. PMID:23263667

  20. The dynamics of embolism refilling in abscisic acid (ABA)-deficient tomato plants.

    PubMed

    Secchi, Francesca; Perrone, Irene; Chitarra, Walter; Zwieniecka, Anna K; Lovisolo, Claudio; Zwieniecki, Maciej A

    2012-12-24

    Plants are in danger of embolism formation in xylem vessels when the balance between water transport capacity and transpirational demand is compromised. To maintain this delicate balance, plants must regulate the rate of transpiration and, if necessary, restore water transport in embolized vessels. Abscisic acid (ABA) is the dominant long-distance signal responsible for plant response to stress, and it is possible that it plays a role in the embolism/refilling cycle. To test this idea, a temporal analysis of embolism and refilling dynamics, transpiration rate and starch content was performed on ABA-deficient mutant tomato plants. ABA-deficient mutants were more vulnerable to embolism formation than wild-type plants, and application of exogenous ABA had no effect on vulnerability. However, mutant plants treated with exogenous ABA had lower stomatal conductance and reduced starch content in the xylem parenchyma cells. The lower starch content could have an indirect effect on the plant's refilling activity. The results confirm that plants with high starch content (moderately stressed mutant plants) were more likely to recover from loss of water transport capacity than plants with low starch content (mutant plants with application of exogenous ABA) or plants experiencing severe water stress. This study demonstrates that ABA most likely does not play any direct role in embolism refilling, but through the modulation of carbohydrate content, it could influence the plant's capacity for refilling.

  1. Jasmonic acid accumulation and systemic photosynthetic and electrical changes in locally burned wild type tomato, ABA-deficient sitiens mutants and sitiens pre-treated by ABA.

    PubMed

    Hlavinka, Jan; Nožková-Hlaváčková, Vladimíra; Floková, Kristýna; Novák, Ondřej; Nauš, Jan

    2012-05-01

    Burning the terminal leaflet of younger tomato (Lycopersicon esculentum Mill.) leaf caused local and systemic changes in the surface electrical potential (SEP) and gas exchange (GE) parameters. The local and systemic accumulation of endogenous abscisic acid (ABA) and jasmonic acid (JA) was measured 85 min after burning. The experiments were conducted with wild type (WT) plants, ABA-deficient mutant sitiens (SIT) and ABA pre-treated SIT plants (SITA). First changes in SEP were detected within 1.5 min after burning and were followed by a decrease in GE parameters within 3-6 min in WT, SIT and SITA plants. GE and SEP time courses of SIT were different and wave amplitudes of SEP of SIT were lower compared to WT and SITA. ABA content in WT and SITA control plants was similar and substantially higher compared to SIT, JA content was similar among WT, SIT and SITA. While changes in the ABA content in systemic leaves have not been recorded after burning, the systemic JA content was substantially increased in WT and more in SIT and SITA. The results suggest that ABA content governs the systemic reaction of GE and the SEP shape upon local burning. ABA, JA and SEP participate in triggering the GE reaction. The ABA shortage in the SIT in the reaction to burning is partly compensated by an enhanced JA accumulation. This JA compensation is maintained even in SIT endogenously supplied with ABA. A correlation between the systemic JA content and changes in GE parameters or SEP was not found.

  2. A DTX/MATE-type transporter facilitates abscisic acid efflux and modulates ABA sensitivity and drought tolerance in Arabidopsis.

    PubMed

    Zhang, Haiwen; Zhu, Huifen; Pan, Yajun; Yu, Yuexuan; Luan, Sheng; Li, Legong

    2014-10-01

    Abscisic acid (ABA) regulates numerous physiological and developmental processes in plants. Recent studies identify intracellular ABA receptors, implicating the transport of ABA across cell membranes as crucial for ABA sensing and response. Here, we report that a DTX/Multidrug and Toxic Compound Extrusion (MATE) family member in Arabidopsis thaliana, AtDTX50, functions as an ABA efflux transporter. When expressed heterologously in both an Escherichia coli strain and Xenopus oocyte cells, AtDTX50 was found to facilitate ABA efflux. Furthermore, dtx50 mutant mesophyll cells preloaded with ABA released less ABA compared with the wild-type (WT). The AtDTX50 gene was expressed mainly in the vascular tissues and guard cells and its expression was strongly up-regulated by exogenous ABA. The AtDTX50::GFP fusion protein was localized predominantly to the plasma membrane. The dtx50 mutant plants were observed to be more sensitive to ABA in growth inhibition. In addition, compared with the WT, dtx50 mutant plants were more tolerant to drought with lower stomatal conductance, consistent with its function as an ABA efflux carrier in guard cells.

  3. Abscisic acid (ABA) receptors: light at the end of the tunnel

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The plant hormone abscisic acid (ABA) plays a role in several aspects of plant growth and development. Understanding how this hormonal stimulus is sensed and transduced turned out to be one of the major tasks in the field of plant signaling. A series of recent papers proposed several different prote...

  4. Functional dissection of an abscisic acid (ABA)-inducible gene reveals two independent ABA-responsive complexes each containing a G-box and a novel cis-acting element.

    PubMed Central

    Shen, Q; Ho, T H

    1995-01-01

    To elucidate the mechanism by which abscisic acid (ABA) regulates gene expression, the promoter of the barley ABA-responsive HVA22 gene has been analyzed by both loss- and gain-of-function studies. Previous reports indicate that G-box sequences, which are present in genes responding to a variety of environmental and physiological cues, are involved in ABA response. However, our data suggest that G-box sequences are necessary but not sufficient for ABA response. Instead, an ABA response complex consisting of a G-box, namely, ABRE3 (GCCACGTACA), and a novel coupling element, CE1 (TGCCACCGG), is sufficient for high-level ABA induction, and replacement of either of these sequences abolishes ABA responsiveness. We suggest that the interaction between G-box sequences, such as ABRE3 in the HVA22 gene, and CE-type sequences determines the specificity in ABA-regulated gene expression. Our results also demonstrate that the ABA response complex is the minimal promoter unit governing high-level ABA induction; four copies of this 49-bp-long complex linked to a minimal promoter can confer more than 100-fold ABA-induced gene expression. In addition to ABA response complex 1, composed of ABRE3 and CE1, the HVA22 promoter contains another ABA response complex. The ABA responsiveness of this ABA response complex 2 relies on the interaction of G-box (ABRE2; CGCACGTGTC) with another yet unidentified coupling element. These two complexes contribute incrementally to the expression level of HVA22 in response to ABA. PMID:7734964

  5. Abscisic acid-regulated responses of aba2-1 under osmotic stress: the abscisic acid-inducible antioxidant defence system and reactive oxygen species production.

    PubMed

    Ozfidan, C; Turkan, I; Sekmen, A H; Seckin, B

    2012-03-01

    We investigated the interaction among abscisic acid (ABA), reactive oxygen species (ROS) and antioxidant defence system in the transduction of osmotic stress signalling using Arabidopsis thaliana WT (Columbia ecotype, WT) and an ABA-deficient mutant (aba2-1). For this, 50 μm ABA and osmotic stress, induced with 40% (w/v) polyethylene glycol (PEG8000; -0.7 MPa), were applied to WT and aba2-1 for 6, 12 or 24 h. Time course analysis was undertaken for determination of total/isoenzyme activity of the antioxidant enzymes, superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6), ascorbate peroxidase (APX; EC 1.11.1.11), NADPH oxidase (NOX; EC 1.6.3.1) activity; scavenging activity of the hydroxyl radical (OH˙), hydrogen peroxide (H(2) O(2) ); endogenous ABA and malondialdehyde (MDA). The highest H(2) O(2) and MDA content was found in PEG-treated groups of both genotypes, but with more in aba2-1. ABA treatment under stress reduced the accumulation of H(2) O(2) and MDA, while it promoted activity of SOD, CAT and APX. APX activity was higher than CAT activity in ABA-treated WT and aba2-1, indicating a protective role of APX rather than CAT during osmotic stress-induced oxidative damage. Treatment with ABA also significantly induced increased NOX activity. Oxidative damage was lower in ABA-treated seedlings of both genotypes, which was associated with greater activity of SOD (Mn-SOD1 and 2 and Fe-SOD isoenzymes), CAT and APX in these seedlings after 24 h of stress. These results suggest that osmotic stress effects were overcome by ABA treatment because of increased SOD, CAT, APX and NOX.

  6. Molecular identification of zeaxanthin epoxidase of Nicotiana plumbaginifolia, a gene involved in abscisic acid biosynthesis and corresponding to the ABA locus of Arabidopsis thaliana.

    PubMed Central

    Marin, E; Nussaume, L; Quesada, A; Gonneau, M; Sotta, B; Hugueney, P; Frey, A; Marion-Poll, A

    1996-01-01

    Abscisic acid (ABA) is a plant hormone which plays an important role in seed development and dormancy and in plant response to environmental stresses. An ABA-deficient mutant of Nicotiana plumbaginifolia, aba2, was isolated by transposon tagging using the maize Activator transposon. The aba2 mutant exhibits precocious seed germination and a severe wilty phenotype. The mutant is impaired in the first step of the ABA biosynthesis pathway, the zeaxanthin epoxidation reaction. ABA2 cDNA is able to complement N.plumbaginifolia aba2 and Arabidopsis thaliana aba mutations indicating that these mutants are homologous. ABA2 cDNA encodes a chloroplast-imported protein of 72.5 kDa, sharing similarities with different mono-oxigenases and oxidases of bacterial origin and having an ADP-binding fold and an FAD-binding domain. ABA2 protein, produced in Escherichia coli, exhibits in vitro zeaxanthin epoxidase activity. This is the first report of the isolation of a gene of the ABA biosynthetic pathway. The molecular identification of ABA2 opens the possibility to study the regulation of ABA biosynthesis and its cellular location. Images PMID:8665840

  7. A Direct Link between Abscisic Acid Sensing and the Chromatin-Remodeling ATPase BRAHMA via Core ABA Signaling Pathway Components.

    PubMed

    Peirats-Llobet, Marta; Han, Soon-Ki; Gonzalez-Guzman, Miguel; Jeong, Cheol Woong; Rodriguez, Lesia; Belda-Palazon, Borja; Wagner, Doris; Rodriguez, Pedro L

    2016-01-04

    Optimal response to drought is critical for plant survival and will affect biodiversity and crop performance during climate change. Mitotically heritable epigenetic or dynamic chromatin state changes have been implicated in the plant response to the drought stress hormone abscisic acid (ABA). The Arabidopsis SWI/SNF chromatin-remodeling ATPase BRAHMA (BRM) modulates response to ABA by preventing premature activation of stress response pathways during germination. We show that core ABA signaling pathway components physically interact with BRM and post-translationally modify BRM by phosphorylation/dephosphorylation. Genetic evidence suggests that BRM acts downstream of SnRK2.2/2.3 kinases, and biochemical studies identified phosphorylation sites in the C-terminal region of BRM at SnRK2 target sites that are evolutionarily conserved. Finally, the phosphomimetic BRM(S1760D S1762D) mutant displays ABA hypersensitivity. Prior studies showed that BRM resides at target loci in the ABA pathway in the presence and absence of the stimulus, but is only active in the absence of ABA. Our data suggest that SnRK2-dependent phosphorylation of BRM leads to its inhibition, and PP2CA-mediated dephosphorylation of BRM restores the ability of BRM to repress ABA response. These findings point to the presence of a rapid phosphorylation-based switch to control BRM activity; this property could be potentially harnessed to improve drought tolerance in plants.

  8. A Jasmonate ZIM-Domain Protein NaJAZd Regulates Floral Jasmonic Acid Levels and Counteracts Flower Abscission in Nicotiana attenuata Plants

    PubMed Central

    Oh, Youngjoo; Baldwin, Ian T.; Galis, Ivan

    2013-01-01

    Jasmonic acid is an important regulator of plant growth, development and defense. The jasmonate-ZIM domain (JAZ) proteins are key regulators in jasmonate signaling ubiquitously present in flowering plants but their functional annotation remains largely incomplete. Recently, we identified 12 putative JAZ proteins in native tobacco, Nicotiana attenuata, and initiated systematic functional characterization of these proteins by reverse genetic approaches. In this report, Nicotiana attenuata plants silenced in the expression of NaJAZd (irJAZd) by RNA interference were used to characterize NaJAZd function. Although NaJAZd transcripts were strongly and transiently up-regulated in the rosette leaves by simulated herbivory treatment, we did not observe strong defense-related phenotypes, such as altered herbivore performance or the constitutive accumulation of defense-related secondary metabolites in irJAZd plants compared to wild type plants, both in the glasshouse and the native habitat of Nicotiana attenuata in the Great Basin Desert, Utah, USA. Interestingly, irJAZd plants produced fewer seed capsules than did wild type plants as a result of increased flower abscission in later stages of flower development. The early- and mid-developmental stages of irJAZd flowers had reduced levels of jasmonic acid and jasmonoyl-L-isoleucine, while fully open flowers had normal levels, but these were impaired in NaMYB305 transcript accumulations. Previously, NaMYB305-silenced plants were shown to have strong flower abscission phenotypes and contained lower NECTARIN 1 transcript levels, phenotypes which are copied in irJAZd plants. We propose that the NaJAZd protein is required to counteract flower abscission, possibly by regulating jasmonic acid and jasmonoyl-L-isoleucine levels and/or expression of NaMYB305 gene in Nicotiana attenuata flowers. This novel insight into the function of JAZ proteins in flower and seed development highlights the diversity of functions played by jasmonates

  9. Nitrogen metabolism responses to water deficit act through both abscisic acid (ABA)-dependent and independent pathways in Medicago truncatula during post-germination.

    PubMed

    Planchet, Elisabeth; Rannou, Olivier; Ricoult, Claudie; Boutet-Mercey, Stéphanie; Maia-Grondard, Alessandra; Limami, Anis M

    2011-01-01

    The modulation of primary nitrogen metabolism by water deficit through ABA-dependent and ABA-independent pathways was investigated in the model legume Medicago truncatula. Growth and glutamate metabolism were followed in young seedlings growing for short periods in darkness and submitted to a moderate water deficit (simulated by polyethylene glycol; PEG) or treated with ABA. Water deficit induced an ABA accumulation, a reduction of axis length in an ABA-dependent manner, and an inhibition of water uptake/retention in an ABA-independent manner. The PEG-induced accumulation of free amino acids (AA), principally asparagine and proline, was mimicked by exogenous ABA treatment. This suggests that AA accumulation under water deficit may be an ABA-induced osmolyte accumulation contributing to osmotic adjustment. Alternatively, this accumulation could be just a consequence of a decreased nitrogen demand caused by reduced extension, which was triggered by water deficit and exogenous ABA treatment. Several enzyme activities involved in glutamate metabolism and genes encoding cytosolic glutamine synthetase (GS1b; EC 6.3.1.2.), glutamate dehydrogenase (GDH3; EC 1.4.1.1.), and asparagine synthetase (AS; EC 6.3.1.1.) were up-regulated by water deficit but not by ABA, except for a gene encoding Δ(1)-pyrroline-5-carboxylate synthetase (P5CS; EC not assigned). Thus, ABA-dependent and ABA-independent regulatory systems would seem to exist, differentially controlling development, water content, and nitrogen metabolism under water deficit.

  10. Accumulation of the hormone abscisic acid (ABA) at the infection site of the fungus Cercospora beticola supports the role of ABA as a repressor of plant defence in sugar beet.

    PubMed

    Schmidt, Klaus; Pflugmacher, Maike; Klages, Simone; Mäser, Anja; Mock, Andrea; Stahl, Dietmar J

    2008-09-01

    Inducible plant defence responses in sugar beet (Beta vulgaris L.) leaves are repressed during the early phase of infection by the fungus Cercospora beticola. In this report, we show that the concentration of the plant hormone abscisic acid (ABA) increases in sugar beet leaves during C. beticola infection. After an initial burst of ABA induced by inoculation of the fungus, elevated ABA concentrations were detected during the fungal penetration and colonization phases 3-9 days after inoculation. Fifteen days after inoculation, with visible onset of the necrotic phase of infection, the strongly elevated ABA concentrations in infected leaves were at levels similar to drought-stressed plants. A synthetic promoter composed of four copies of the ABA-responsive element (ABRE) A2 and the coupling element CE3 of the ABA-inducible barley gene HVA1 was strongly induced by ABA and C. beticola infection in transgenic sugar beet leaves. Analysis of the spatial pattern of promoter activity revealed that the ABA-inducible promoter was locally activated at the fungal infection sites. Furthermore, expression of the basic leucine zipper transcription factor AREB1 was induced by drought stress and fungal infection in the sugar beet. Application of ABA reduced the promoter activity of the phenylalanine ammonia lyase (BvPAL) gene, and this effect was observed with the -34 to +248 BvPAL promoter region. This region is equivalent to the core promoter, which is necessary for the suppression of BvPAL expression by C. beticola, as recently shown. These data indicate that ABA accumulation and activation of the ABA-dependent signalling cascade are the primary cause of suppression of BvPAL expression during infection of sugar beet leaves.

  11. The manipulation of auxin in the abscission zone cells of Arabidopsis flowers reveals that indoleacetic acid signaling is a prerequisite for organ shedding.

    PubMed

    Basu, Manojit M; González-Carranza, Zinnia H; Azam-Ali, Sayed; Tang, Shouya; Shahid, Ahmad Ali; Roberts, Jeremy A

    2013-05-01

    A number of novel strategies were employed to examine the role of indoleacetic acid (IAA) in regulating floral organ abscission in Arabidopsis (Arabidopsis thaliana). Analysis of auxin influx facilitator expression in β-glucuronidase reporter plants revealed that AUXIN RESISTANT1, LIKE AUX1, and LAX3 were specifically up-regulated at the site of floral organ shedding. Flowers from mutants where individual family members were down-regulated exhibited a reduction in the force necessary to bring about petal separation; however, the effect was not additive in double or quadruple mutants. Using the promoter of a polygalacturonase (At2g41850), active primarily in cells undergoing separation, to drive expression of the bacterial genes iaaL and iaaM, we have shown that it is possible to manipulate auxin activity specifically within the floral organ abscission zone (AZ). Analysis of petal breakstrength reveals that if IAA AZ levels are reduced, shedding takes place prematurely, while if they are enhanced, organ loss is delayed. The At2g41850 promoter was also used to transactivate the gain-of-function AXR3-1 gene in order to disrupt auxin signaling specifically within the floral organ AZ cells. Flowers from transactivated lines failed to shed their sepals, petals, and anthers during pod expansion and maturity, and these organs frequently remained attached to the plant even after silique desiccation and dehiscence had taken place. These observations support a key role for IAA in the regulation of abscission in planta and reveal, to our knowledge for the first time, a requirement for a functional IAA signaling pathway in AZ cells for organ shedding to take place.

  12. The Manipulation of Auxin in the Abscission Zone Cells of Arabidopsis Flowers Reveals That Indoleacetic Acid Signaling Is a Prerequisite for Organ Shedding1[C][W][OA

    PubMed Central

    Basu, Manojit M.; González-Carranza, Zinnia H.; Azam-Ali, Sayed; Tang, Shouya; Shahid, Ahmad Ali; Roberts, Jeremy A.

    2013-01-01

    A number of novel strategies were employed to examine the role of indoleacetic acid (IAA) in regulating floral organ abscission in Arabidopsis (Arabidopsis thaliana). Analysis of auxin influx facilitator expression in β-glucuronidase reporter plants revealed that AUXIN RESISTANT1, LIKE AUX1, and LAX3 were specifically up-regulated at the site of floral organ shedding. Flowers from mutants where individual family members were down-regulated exhibited a reduction in the force necessary to bring about petal separation; however, the effect was not additive in double or quadruple mutants. Using the promoter of a polygalacturonase (At2g41850), active primarily in cells undergoing separation, to drive expression of the bacterial genes iaaL and iaaM, we have shown that it is possible to manipulate auxin activity specifically within the floral organ abscission zone (AZ). Analysis of petal breakstrength reveals that if IAA AZ levels are reduced, shedding takes place prematurely, while if they are enhanced, organ loss is delayed. The At2g41850 promoter was also used to transactivate the gain-of-function AXR3-1 gene in order to disrupt auxin signaling specifically within the floral organ AZ cells. Flowers from transactivated lines failed to shed their sepals, petals, and anthers during pod expansion and maturity, and these organs frequently remained attached to the plant even after silique desiccation and dehiscence had taken place. These observations support a key role for IAA in the regulation of abscission in planta and reveal, to our knowledge for the first time, a requirement for a functional IAA signaling pathway in AZ cells for organ shedding to take place. PMID:23509178

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

    PubMed Central

    Guo, Dong; Zhou, Ying; Li, Hui-Liang; Zhu, Jia-Hong; Wang, Ying; Chen, Xiong-Ting; Peng, Shi-Qing

    2017-01-01

    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. PMID:28332623

  14. Release of GTP Exchange Factor Mediated Down-Regulation of Abscisic Acid Signal Transduction through ABA-Induced Rapid Degradation of RopGEFs.

    PubMed

    Li, Zixing; Waadt, Rainer; Schroeder, Julian I

    2016-05-01

    The phytohormone abscisic acid (ABA) is critical to plant development and stress responses. Abiotic stress triggers an ABA signal transduction cascade, which is comprised of the core components PYL/RCAR ABA receptors, PP2C-type protein phosphatases, and protein kinases. Small GTPases of the ROP/RAC family act as negative regulators of ABA signal transduction. However, the mechanisms by which ABA controls the behavior of ROP/RACs have remained unclear. Here, we show that an Arabidopsis guanine nucleotide exchange factor protein RopGEF1 is rapidly sequestered to intracellular particles in response to ABA. GFP-RopGEF1 is sequestered via the endosome-prevacuolar compartment pathway and is degraded. RopGEF1 directly interacts with several clade A PP2C protein phosphatases, including ABI1. Interestingly, RopGEF1 undergoes constitutive degradation in pp2c quadruple abi1/abi2/hab1/pp2ca mutant plants, revealing that active PP2C protein phosphatases protect and stabilize RopGEF1 from ABA-mediated degradation. Interestingly, ABA-mediated degradation of RopGEF1 also plays an important role in ABA-mediated inhibition of lateral root growth. The presented findings point to a PP2C-RopGEF-ROP/RAC control loop model that is proposed to aid in shutting off ABA signal transduction, to counteract leaky ABA signal transduction caused by "monomeric" PYL/RCAR ABA receptors in the absence of stress, and facilitate signaling in response to ABA.

  15. Environmental Factors in the Physiology of Abscission

    PubMed Central

    Addicott, Fredrick T.

    1968-01-01

    This paper reviews the physiological effects of the principal environmental factors which can influence the process of leaf abscission. The factors include temperature, light, water, gases, mineral elements, soil conditions, and parasitic organisms. These factors influence a variety of internal physiological conditions and processes which in turn may either accelerate or retard the process of abscission. The most important internal factors include A) sugar, pectin, cellulose, and other carbohydrates; B) energy-yielding respiration; C) enzymic reactions; D) amino acids, purines, and other nitrogenous substances; E) levels of plant hormones; and F) the molecular biological pathway. The current information is consistent with the hypothesis that the environmental factors act in leaf abscission via direct or indirect influences on the synthesis or reaction rate of enzymes. PMID:16657013

  16. Cross-talk in abscisic acid signaling

    NASA Technical Reports Server (NTRS)

    Fedoroff, Nina V.

    2002-01-01

    "Cross-talk" in hormone signaling reflects an organism's ability to integrate different inputs and respond appropriately, a crucial function at the heart of signaling network operation. Abscisic acid (ABA) is a plant hormone involved in bud and seed dormancy, growth regulation, leaf senescence and abscission, stomatal opening, and a variety of plant stress responses. This review summarizes what is known about ABA signaling in the control of stomatal opening and seed dormancy and provides an overview of emerging knowledge about connections between ABA, ethylene, sugar, and auxin synthesis and signaling.

  17. Ethephon As a Potential Abscission Agent for Table Grapes: Effects on Pre-Harvest Abscission, Fruit Quality, and Residue

    PubMed Central

    Ferrara, Giuseppe; Mazzeo, Andrea; Matarrese, Angela M. S.; Pacucci, Carmela; Trani, Antonio; Fidelibus, Matthew W.; Gambacorta, Giuseppe

    2016-01-01

    Some plant growth regulators, including ethephon, can stimulate abscission of mature grape berries. The stimulation of grape berry abscission reduces fruit detachment force (FDF) and promotes the development of a dry stem scar, both of which could facilitate the production of high quality stemless fresh-cut table grapes. The objective of this research was to determine how two potential abscission treatments, 1445 and 2890 mg/L ethephon, affected FDF, pre-harvest abscission, fruit quality, and ethephon residue of Thompson Seedless and Crimson Seedless grapes. Both ethephon treatments strongly induced abscission of Thompson Seedless berries causing >90% pre-harvest abscission. Lower ethephon rates, a shorter post-harvest interval, or berry retention systems such as nets, would be needed to prevent excessive pre-harvest losses. The treatments also slightly affected Thompson Seedless berry skin color, with treated fruit being darker, less uniform in color, and with a more yellow hue than non-treated fruit. Ethephon residues on Thompson Seedless grapes treated with the lower concentration of ethephon were below legal limits at harvest. Ethephon treatments also promoted abscission of Crimson Seedless berries, but pre-harvest abscission was much lower (≅49%) in Crimson Seedless compared to Thompson Seedless. Treated fruits were slightly darker than non-treated fruits, but ethephon did not affect SSC, acidity, or firmness of Crimson Seedless, and ethephon residues were below legal limits. PMID:27303407

  18. Mutations in the Arabidopsis Lst8 and Raptor genes encoding partners of the TOR complex, or inhibition of TOR activity decrease abscisic acid (ABA) synthesis.

    PubMed

    Kravchenko, Alena; Citerne, Sylvie; Jéhanno, Isabelle; Bersimbaev, Rakhmetkazhi I; Veit, Bruce; Meyer, Christian; Leprince, Anne-Sophie

    2015-11-27

    The Target of Rapamycin (TOR) kinase regulates essential processes in plant growth and development by modulation of metabolism and translation in response to environmental signals. In this study, we show that abscisic acid (ABA) metabolism is also regulated by the TOR kinase. Indeed ABA hormone level strongly decreases in Lst8-1 and Raptor3g mutant lines as well as in wild-type (WT) Arabidopsis plants treated with AZD-8055, a TOR inhibitor. However the growth and germination of these lines are more sensitive to exogenous ABA. The diminished ABA hormone accumulation is correlated with lower transcript levels of ZEP, NCED3 and AAO3 biosynthetic enzymes, and higher transcript amount of the CYP707A2 gene encoding a key-enzyme in abscisic acid catabolism. These results suggest that the TOR signaling pathway is implicated in the regulation of ABA accumulation in Arabidopsis.

  19. Transcriptomics of shading-induced and NAA-induced abscission in apple (Malus domestica) reveals a shared pathway involving reduced photosynthesis, alterations in carbohydrate transport and signaling and hormone crosstalk

    PubMed Central

    2011-01-01

    Background Naphthaleneacetic acid (NAA), a synthetic auxin analogue, is widely used as an effective thinner in apple orchards. When applied shortly after fruit set, some fruit abscise leading to improved fruit size and quality. However, the thinning results of NAA are inconsistent and difficult to predict, sometimes leading to excess fruit drop or insufficient thinning which are costly to growers. This unpredictability reflects our incomplete understanding of the mode of action of NAA in promoting fruit abscission. Results Here we compared NAA-induced fruit drop with that caused by shading via gene expression profiling performed on the fruit abscission zone (FAZ), sampled 1, 3, and 5 d after treatment. More than 700 genes with significant changes in transcript abundance were identified from NAA-treated FAZ. Combining results from both treatments, we found that genes associated with photosynthesis, cell cycle and membrane/cellular trafficking were downregulated. On the other hand, there was up-regulation of genes related to ABA, ethylene biosynthesis and signaling, cell wall degradation and programmed cell death. While the differentially expressed gene sets for NAA and shading treatments shared only 25% identity, NAA and shading showed substantial similarity with respect to the classes of genes identified. Specifically, photosynthesis, carbon utilization, ABA and ethylene pathways were affected in both NAA- and shading-induced young fruit abscission. Moreover, we found that NAA, similar to shading, directly interfered with leaf photosynthesis by repressing photosystem II (PSII) efficiency within 10 minutes of treatment, suggesting that NAA and shading induced some of the same early responses due to reduced photosynthesis, which concurred with changes in hormone signaling pathways and triggered fruit abscission. Conclusions This study provides an extensive transcriptome study and a good platform for further investigation of possible regulatory genes involved in the

  20. Structural basis for basal activity and autoactivation of abscisic acid (ABA) signaling SnRK2 kinases

    SciTech Connect

    Ng, Ley-Moy; Soon, Fen-Fen; Zhou, X. Edward; West, Graham M.; Kovach, Amanda; Suino-Powell, Kelly M.; Chalmers, Michael J.; Li, Jun; Yong, Eu-Leong; Zhu, Jian-Kang; Griffin, Patrick R.; Melcher, Karsten; Xu, H. Eric

    2014-10-02

    Abscisic acid (ABA) is an essential hormone that controls plant growth, development, and responses to abiotic stresses. Central for ABA signaling is the ABA-mediated autoactivation of three monomeric Snf1-related kinases (SnRK2.2, -2.3, and -2.6). In the absence of ABA, SnRK2s are kept in an inactive state by forming physical complexes with type 2C protein phosphatases (PP2Cs). Upon relief of this inhibition, SnRK2 kinases can autoactivate through unknown mechanisms. Here, we report the crystal structures of full-length Arabidopsis thaliana SnRK2.3 and SnRK2.6 at 1.9- and 2.3-{angstrom} resolution, respectively. The structures, in combination with biochemical studies, reveal a two-step mechanism of intramolecular kinase activation that resembles the intermolecular activation of cyclin-dependent kinases. First, release of inhibition by PP2C allows the SnRK2s to become partially active because of an intramolecular stabilization of the catalytic domain by a conserved helix in the kinase regulatory domain. This stabilization enables SnRK2s to gain full activity by activation loop autophosphorylation. Autophosphorylation is more efficient in SnRK2.6, which has higher stability than SnRK2.3 and has well-structured activation loop phosphate acceptor sites that are positioned next to the catalytic site. Together, these data provide a structural framework that links ABA-mediated release of PP2C inhibition to activation of SnRK2 kinases.

  1. Structural basis for basal activity and autoactivation of abscisic acid (ABA) signaling SnRK2 kinases

    PubMed Central

    Ng, Ley-Moy; Soon, Fen-Fen; Zhou, X. Edward; West, Graham M.; Kovach, Amanda; Suino-Powell, Kelly M.; Chalmers, Michael J.; Li, Jun; Yong, Eu-Leong; Zhu, Jian-Kang; Griffin, Patrick R.; Melcher, Karsten; Xu, H. Eric

    2011-01-01

    Abscisic acid (ABA) is an essential hormone that controls plant growth, development, and responses to abiotic stresses. Central for ABA signaling is the ABA-mediated autoactivation of three monomeric Snf1-related kinases (SnRK2.2, -2.3, and -2.6). In the absence of ABA, SnRK2s are kept in an inactive state by forming physical complexes with type 2C protein phosphatases (PP2Cs). Upon relief of this inhibition, SnRK2 kinases can autoactivate through unknown mechanisms. Here, we report the crystal structures of full-length Arabidopsis thaliana SnRK2.3 and SnRK2.6 at 1.9- and 2.3-Å resolution, respectively. The structures, in combination with biochemical studies, reveal a two-step mechanism of intramolecular kinase activation that resembles the intermolecular activation of cyclin-dependent kinases. First, release of inhibition by PP2C allows the SnRK2s to become partially active because of an intramolecular stabilization of the catalytic domain by a conserved helix in the kinase regulatory domain. This stabilization enables SnRK2s to gain full activity by activation loop autophosphorylation. Autophosphorylation is more efficient in SnRK2.6, which has higher stability than SnRK2.3 and has well-structured activation loop phosphate acceptor sites that are positioned next to the catalytic site. Together, these data provide a structural framework that links ABA-mediated release of PP2C inhibition to activation of SnRK2 kinases. PMID:22160701

  2. Genetic Analysis of Physcomitrella patens Identifies ABSCISIC ACID NON-RESPONSIVE, a Regulator of ABA Responses Unique to Basal Land Plants and Required for Desiccation Tolerance.

    PubMed

    Stevenson, Sean R; Kamisugi, Yasuko; Trinh, Chi H; Schmutz, Jeremy; Jenkins, Jerry W; Grimwood, Jane; Muchero, Wellington; Tuskan, Gerald A; Rensing, Stefan A; Lang, Daniel; Reski, Ralf; Melkonian, Michael; Rothfels, Carl J; Li, Fay-Wei; Larsson, Anders; Wong, Gane K-S; Edwards, Thomas A; Cuming, Andrew C

    2016-06-01

    The anatomically simple plants that first colonized land must have acquired molecular and biochemical adaptations to drought stress. Abscisic acid (ABA) coordinates responses leading to desiccation tolerance in all land plants. We identified ABA nonresponsive mutants in the model bryophyte Physcomitrella patens and genotyped a segregating population to map and identify the ABA NON-RESPONSIVE (ANR) gene encoding a modular protein kinase comprising an N-terminal PAS domain, a central EDR domain, and a C-terminal MAPKKK-like domain. anr mutants fail to accumulate dehydration tolerance-associated gene products in response to drought, ABA, or osmotic stress and do not acquire ABA-dependent desiccation tolerance. The crystal structure of the PAS domain, determined to 1.7-Å resolution, shows a conserved PAS-fold that dimerizes through a weak dimerization interface. Targeted mutagenesis of a conserved tryptophan residue within the PAS domain generates plants with ABA nonresponsive growth and strongly attenuated ABA-responsive gene expression, whereas deleting this domain retains a fully ABA-responsive phenotype. ANR orthologs are found in early-diverging land plant lineages and aquatic algae but are absent from more recently diverged vascular plants. We propose that ANR genes represent an ancestral adaptation that enabled drought stress survival of the first terrestrial colonizers but were lost during land plant evolution.

  3. Genetic analysis of Physcomitrella patens identifies ABSCISIC ACID NON-RESPONSIVE, a regulator of ABA responses unique to basal land plants and required for desiccation tolerance

    DOE PAGES

    Stevenson, Sean Ross; Kamisugi, Yasuko; Trinh, Chi H.; ...

    2016-05-18

    The anatomically simple plants that first colonized land must have acquired molecular and biochemical adaptations to drought stress. Abscisic acid (ABA) coordinates responses leading to desiccation tolerance in all land plants. We identified ABA nonresponsive mutants in the model bryophyte Physcomitrella patens and genotyped a segregating population to map and identify the ABA NON-RESPONSIVE (ANR) gene encoding a modular protein kinase comprising an N-terminal PAS domain, a central EDR domain, and a C-terminal MAPKKK-like domain. anr mutants fail to accumulate dehydration tolerance-associated gene products in response to drought, ABA, or osmotic stress and do not acquire ABA-dependent desiccation tolerance. Themore » crystal structure of the PAS domain, determined to 1.7-Å resolution, shows a conserved PAS-fold that dimerizes through a weak dimerization interface. Targeted mutagenesis of a conserved tryptophan residue within the PAS domain generates plants with ABA nonresponsive growth and strongly attenuated ABA-responsive gene expression, whereas deleting this domain retains a fully ABA-responsive phenotype. ANR orthologs are found in early-diverging land plant lineages and aquatic algae but are absent from more recently diverged vascular plants. Lastly, we propose that ANR genes represent an ancestral adaptation that enabled drought stress survival of the first terrestrial colonizers but were lost during land plant evolution.« less

  4. Gladiolus hybridus ABSCISIC ACID INSENSITIVE 5 (GhABI5) is an important transcription factor in ABA signaling that can enhance Gladiolus corm dormancy and Arabidopsis seed dormancy

    PubMed Central

    Wu, Jian; Seng, Shanshan; Sui, Juanjuan; Vonapartis, Eliana; Luo, Xian; Gong, Benhe; Liu, Chen; Wu, Chenyu; Liu, Chao; Zhang, Fengqin; He, Junna; Yi, Mingfang

    2015-01-01

    The phytohormone abscisic acid (ABA) regulates plant development and is crucial for abiotic stress response. In this study, cold storage contributes to reducing endogenous ABA content, resulting in dormancy breaking of Gladiolus. The ABA inhibitor fluridone also promotes germination, suggesting that ABA is an important hormone that regulates corm dormancy. Here, we report the identification and functional characterization of the Gladiolus ABI5 homolog (GhABI5), which is a basic leucine zipper motif transcriptional factor (TF). GhABI5 is expressed in dormant vegetative organs (corm, cormel, and stolon) as well as in reproductive organs (stamen), and it is up-regulated by ABA or drought. Complementation analysis reveals that GhABI5 rescues the ABA insensitivity of abi5-3 during seed germination and induces the expression of downstream ABA response genes in Arabidopsis thaliana (EM1, EM6, and RD29B). Down-regulation of GhABI5 in dormant cormels via virus induced gene silence promotes sprouting and reduces the expression of downstream genes (GhLEA and GhRD29B). The results of this study reveal that GhABI5 regulates bud dormancy (vegetative organ) in Gladiolus in addition to its well-studied function in Arabidopsis seeds (reproductive organ). PMID:26579187

  5. Modulation Role of abscisic acid (ABA) on growth, water relations and glycinebetaine metabolism in two maize (Zea mays L.) cultivars under drought stress.

    PubMed

    Zhang, Lixin; Gao, Mei; Hu, Jingjiang; Zhang, Xifeng; Wang, Kai; Ashraf, Muhammad

    2012-01-01

    The role of plant hormone abscisic acid (ABA) in plants under drought stress (DS) is crucial in modulating physiological responses that eventually lead to adaptation to an unfavorable environment; however, the role of this hormone in modulation of glycinebetaine (GB) metabolism in maize particularly at the seedling stage is still poorly understood. Some hydroponic experiments were conducted to investigate the modulation role of ABA on plant growth, water relations and GB metabolism in the leaves of two maize cultivars, Zhengdan 958 (ZD958; drought tolerant), and Jundan 20 (JD20; drought sensitive), subjected to integrated root-zone drought stress (IR-DS) simulated by the addition of polyethylene glycol (PEG, 12% w/v, MW 6000). The IR-DS substantially resulted in increased betaine aldehyde dehydrogenase (BADH) activity and choline content which act as the key enzyme and initial substrate, respectively, in GB biosynthesis. Drought stress also induced accumulation of GB, whereas it caused reduction in leaf relative water content (RWC) and dry matter (DM) in both cultivars. The contents of ABA and GB increased in drought-stressed maize seedlings, but ABA accumulated prior to GB accumulation under the drought treatment. These responses were more predominant in ZD958 than those in JD20. Addition of exogenous ABA and fluridone (Flu) (ABA synthesis inhibitor) applied separately increased and decreased BADH activity, respectively. Abscisic acid application enhanced GB accumulation, leaf RWC and shoot DM production in both cultivars. However, of both maize cultivars, the drought sensitive maize cultivar (JD20) performed relatively better than the other maize cultivar ZD958 under both ABA and Flu application in view of all parameters appraised. It is, therefore, concluded that increase in both BADH activity and choline content possibly resulted in enhancement of GB accumulation under DS. The endogenous ABA was probably involved in the regulation of GB metabolism by regulating

  6. Expression Analysis of Four Peroxiredoxin Genes from Tamarix hispida in Response to Different Abiotic Stresses and Exogenous Abscisic Acid (ABA)

    PubMed Central

    Gao, Caiqiu; Zhang, Kaimin; Yang, Guiyan; Wang, Yucheng

    2012-01-01

    Peroxiredoxins (Prxs) are a recently discovered family of antioxidant enzymes that catalyze the reduction of peroxides and alkyl peroxides. In this study, four Prx genes (named as ThPrxII, ThPrxIIE, ThPrxIIF, and Th2CysPrx) were cloned from Tamarix hispida. Their expression profiles in response to stimulus of NaCl, NaHCO3, PEG, CdCl2 and abscisic acid (ABA) in roots, stems and leaves of T. hispida were investigated using real-time RT-PCR. The results showed that the four ThPrxs were all expressed in roots, stems and leaves. Furthermore, the transcript levels of ThPrxIIE and ThPrxII were the lowest and the highest, respectively, in all tissue types. All the ThPrx genes were induced by both NaCl and NaHCO3 and reached their highest expression levels at the onset of stress in roots. Under PEG and CdCl2 stress, the expression patterns of these ThPrxs showed temporal and spatial specificity. The expressions of the ThPrxs were all differentially regulated by ABA, indicating that they are all involved in the ABA signaling pathway. These findings reveal a complex regulation of Prxs that is dependent on the type of Prx, tissue, and the signaling molecule. The divergence of the stress-dependent transcriptional regulation of the ThPrx gene family in T. hispida may provide an essential basis for the elucidation of Prx function in future work. PMID:22489180

  7. Salicylic acid mediates antioxidant defense system and ABA pathway related gene expression in Oryza sativa against quinclorac toxicity.

    PubMed

    Wang, Jian; Lv, Mengting; Islam, Faisal; Gill, Rafaqat A; Yang, Chong; Ali, Basharat; Yan, Guijun; Zhou, Weijun

    2016-11-01

    The auxin herbicide quinclorac is widely used for controlling weeds in transplanted and direct-seeded rice fields. However, its phytotoxic responses on rice are still unknown. Therefore, in the present investigation we studied the effects of different concentrations (0, 0.1 and 0.5g/L) of quinclorac herbicide on the physiological and biochemical changes of two rice cultivars (XS 134 and ZJ 88) and further analyzed the ameliorating role of salicylic acid (SA) on quinclorac toxicity in rice plants. The results revealed that exogenous application of SA significantly increased plant biomass and total chlorophyll contents in herbicide stressed plants. The lipid peroxidation and ROS (H2O2, O2(-.), (-)OH) production were significantly increased in roots and leaves of both rice cultivars under quinclorac stress, demonstrating an oxidative burst in rice plants. Whereas, application of SA significantly lowered ROS contents under quinclorac stress. Further, exogenous SA treatment significantly modulated antioxidant enzymes and enhanced GSH concentration in stress plants. Anatomical observations of leaf and root revealed that herbicide affected internal structures, while SA played a vital role in protection from toxic effects. Expression analysis of stress hormone ABA genes (OsABA8oxs, OsNCEDs) revealed that quinclorac application enhanced stress condition in cultivar ZJ 88, while SA treatment downregulated ABA genes more in cultivar XS 134, which correlated with the enhanced tolerance to quinclorac induced oxidative stress in this cultivar. The present study delineated that SA played a critical role under quinclorac stress in both rice cultivars by regulating antioxidant defense system, reducing ROS formation and preventing the degradation of internal cell organelles.

  8. Expression analysis of four peroxiredoxin genes from Tamarix hispida in response to different abiotic stresses and Exogenous Abscisic Acid (ABA).

    PubMed

    Gao, Caiqiu; Zhang, Kaimin; Yang, Guiyan; Wang, Yucheng

    2012-01-01

    Peroxiredoxins (Prxs) are a recently discovered family of antioxidant enzymes that catalyze the reduction of peroxides and alkyl peroxides. In this study, four Prx genes (named as ThPrxII, ThPrxIIE, ThPrxIIF, and Th2CysPrx) were cloned from Tamarix hispida. Their expression profiles in response to stimulus of NaCl, NaHCO(3), PEG, CdCl(2) and abscisic acid (ABA) in roots, stems and leaves of T. hispida were investigated using real-time RT-PCR. The results showed that the four ThPrxs were all expressed in roots, stems and leaves. Furthermore, the transcript levels of ThPrxIIE and ThPrxII were the lowest and the highest, respectively, in all tissue types. All the ThPrx genes were induced by both NaCl and NaHCO(3) and reached their highest expression levels at the onset of stress in roots. Under PEG and CdCl(2) stress, the expression patterns of these ThPrxs showed temporal and spatial specificity. The expressions of the ThPrxs were all differentially regulated by ABA, indicating that they are all involved in the ABA signaling pathway. These findings reveal a complex regulation of Prxs that is dependent on the type of Prx, tissue, and the signaling molecule. The divergence of the stress-dependent transcriptional regulation of the ThPrx gene family in T. hispida may provide an essential basis for the elucidation of Prx function in future work.

  9. The ABA receptors -- we report you decide.

    PubMed

    McCourt, Peter; Creelman, Robert

    2008-10-01

    The plant hormone abscisic acid (ABA) has been implicated in a variety of physiological responses ranging from seed dormancy to stomatal conductance. Recently, three groups have reported the molecular identification of three disparate ABA receptors. Unlike the identification of other hormone receptors, in these three cases high affinity binding to ABA rather than the isolation of ABA insensitive mutants led to these receptor genes. Interestingly, two of the receptors encode genes involved in floral timing and chlorophyll biosynthesis, which are not considered traditional ABA responses. And the third receptor has been clouded in issues of its molecular identity. To clearly determine the roles of these genes in ABA perception it will require placing of these ABA-binding proteins into the rich ABA physiological context that has built up over the years.

  10. ABA Receptors: Past, Present and Future

    SciTech Connect

    Guo, Jianjun; Yang, Xiaohan; Weston, David; Chen, Jay

    2011-01-01

    Abscisic acid (ABA) is the key plant stress hormone. Consistent with the earlier studies in support of the presence of both membrane- and cytoplasm-localized ABA receptors, recent studies have identified multiple ABA receptors located in various subcellular locations. These include a chloroplast envelope-localized receptor (the H subunit of Chloroplast Mg2+-chelatase/ABA Receptor), two plasma membrane-localized receptors (G-protein Coupled Receptor 2 and GPCR-type G proteins), and one cytosol/nucleus-localized Pyrabactin Resistant (PYR)/PYR-Like (PYL)/Regulatory Component of ABA Receptor 1 (RCAR). Although the downstream molecular events for most of the identified ABA receptors are currently unknown, one of them, PYR/PYL/RACR was found to directly bind and regulate the activity of a long-known central regulator of ABA signaling, the A-group protein phosphatase 2C (PP2C). Together with the Sucrose Non-fermentation Kinase Subfamily 2 (SnRK2s) protein kinases, a central signaling complex (ABA-PYR-PP2Cs-SnRK2s) that is responsible for ABA signal perception and transduction is supported by abundant genetic, physiological, biochemical and structural evidence. The identification of multiple ABA receptors has advanced our understanding of ABA signal perception and transduction while adding an extra layer of complexity.

  11. Inhibition of ESCRT-II-CHMP6 interactions impedes cytokinetic abscission and leads to cell death.

    PubMed

    Goliand, Inna; Nachmias, Dikla; Gershony, Ofir; Elia, Natalie

    2014-11-15

    Recently the ESCRT-III filamentous complex was designated as the driving force for mammalian cell abscission, that is, fission of the intercellular membrane bridge connecting daughter cells at the end of cytokinesis. However, how ESCRT-III is activated to set on abscission has not been resolved. Here we revisit the role of the upstream canonical ESCRT players ESCRT-II and CHMP6 in abscission. Using high-resolution imaging, we show that these proteins form highly ordered structures at the intercellular bridge during abscission progression. Furthermore, we demonstrate that a truncated version of CHMP6, composed of its first 52 amino acids (CHMP6-N), arrives at the intercellular bridge, blocks abscission, and subsequently leads to cell death. This phenotype is abolished in a mutated version of CHMP6-N designed to prevent CHMP6-N binding to its ESCRT-II partner. Of interest, deleting the first 10 amino acids from CHMP6-N does not interfere with its arrival at the intercellular bridge but almost completely abolishes the abscission failure phenotype. Taken together, these data suggest an active role for ESCRT-II and CHMP6 in ESCRT-mediated abscission. Our work advances the mechanistic understanding of ESCRT-mediated membrane fission in cells and introduces an easily applicable tool for upstream inhibition of the ESCRT pathway in live mammalian cells.

  12. Fruit load induces changes in global gene expression and in abscisic acid (ABA) and indole acetic acid (IAA) homeostasis in citrus buds

    PubMed Central

    Shalom, Liron; Samuels, Sivan; Zur, Naftali; Shlizerman, Lyudmila; Doron-Faigenboim, Adi; Blumwald, Eduardo; Sadka, Avi

    2014-01-01

    Many fruit trees undergo cycles of heavy fruit load (ON-Crop) in one year, followed by low fruit load (OFF-Crop) the following year, a phenomenon known as alternate bearing (AB). The mechanism by which fruit load affects flowering induction during the following year (return bloom) is still unclear. Although not proven, it is commonly accepted that the fruit or an organ which senses fruit presence generates an inhibitory signal that moves into the bud and inhibits apical meristem transition. Indeed, fruit removal from ON-Crop trees (de-fruiting) induces return bloom. Identification of regulatory or metabolic processes modified in the bud in association with altered fruit load might shed light on the nature of the AB signalling process. The bud transcriptome of de-fruited citrus trees was compared with those of ON- and OFF-Crop trees. Fruit removal resulted in relatively rapid changes in global gene expression, including induction of photosynthetic genes and proteins. Altered regulatory mechanisms included abscisic acid (ABA) metabolism and auxin polar transport. Genes of ABA biosynthesis were induced; however, hormone analyses showed that the ABA level was reduced in OFF-Crop buds and in buds shortly following fruit removal. Additionally, genes associated with Ca2+-dependent auxin polar transport were remarkably induced in buds of OFF-Crop and de-fruited trees. Hormone analyses showed that auxin levels were reduced in these buds as compared with ON-Crop buds. In view of the auxin transport autoinhibition theory, the possibility that auxin distribution plays a role in determining bud fate is discussed. PMID:24706719

  13. Fruit load induces changes in global gene expression and in abscisic acid (ABA) and indole acetic acid (IAA) homeostasis in citrus buds.

    PubMed

    Shalom, Liron; Samuels, Sivan; Zur, Naftali; Shlizerman, Lyudmila; Doron-Faigenboim, Adi; Blumwald, Eduardo; Sadka, Avi

    2014-07-01

    Many fruit trees undergo cycles of heavy fruit load (ON-Crop) in one year, followed by low fruit load (OFF-Crop) the following year, a phenomenon known as alternate bearing (AB). The mechanism by which fruit load affects flowering induction during the following year (return bloom) is still unclear. Although not proven, it is commonly accepted that the fruit or an organ which senses fruit presence generates an inhibitory signal that moves into the bud and inhibits apical meristem transition. Indeed, fruit removal from ON-Crop trees (de-fruiting) induces return bloom. Identification of regulatory or metabolic processes modified in the bud in association with altered fruit load might shed light on the nature of the AB signalling process. The bud transcriptome of de-fruited citrus trees was compared with those of ON- and OFF-Crop trees. Fruit removal resulted in relatively rapid changes in global gene expression, including induction of photosynthetic genes and proteins. Altered regulatory mechanisms included abscisic acid (ABA) metabolism and auxin polar transport. Genes of ABA biosynthesis were induced; however, hormone analyses showed that the ABA level was reduced in OFF-Crop buds and in buds shortly following fruit removal. Additionally, genes associated with Ca(2+)-dependent auxin polar transport were remarkably induced in buds of OFF-Crop and de-fruited trees. Hormone analyses showed that auxin levels were reduced in these buds as compared with ON-Crop buds. In view of the auxin transport autoinhibition theory, the possibility that auxin distribution plays a role in determining bud fate is discussed.

  14. Abscisic acid (ABA) inhibits light-induced stomatal opening through calcium- and nitric oxide-mediated signaling pathways.

    PubMed

    Garcia-Mata, Carlos; Lamattina, Lorenzo

    2007-01-01

    Nitric oxide (NO) is an important signaling component of ABA-induced stomatal closure. However, only fragmentary data are available about NO effect on the inhibition of stomatal opening. Here, we present results supporting that, in Vicia faba guard cells, there is a critical Ca2+-dependent NO increase required for the ABA-mediated inhibition of stomatal opening. Light-induced stomatal opening was inhibited by exogenous NO in V. faba epidermal strips. Furthermore, ABA-mediated inhibition of stomatal opening was blocked by the specific NO scavenger cPTIO, supporting the involvement of endogenous NO in this process. Since the raise in Ca2+ concentration is a pre-requisite in ABA-mediated inhibition of stomatal opening, it was interesting to establish how does Ca2+, NO and ABA interact in the inhibition of light-induced stomatal opening. The permeable Ca2+ specific buffer BAPTA-AM blocked both ABA- and Ca2+- but not NO-mediated inhibition of stomatal opening. The NO synthase (NOS) specific inhibitor L-NAME prevented Ca2+-mediated inhibition of stomatal opening, indicating that a NOS-like activity was required for Ca2+ signaling. Furthermore, experiments using the NO specific fluorescent probe DAF-2DA indicated that Ca2+ induces an increase of endogenous NO. These results indicate that, in addition to the roles in ABA-triggered stomatal closure, both NO and Ca2+ are active components of signaling events acting in ABA inhibition of light-induced stomatal opening. Results also support that Ca2+ induces the NO production through the activation of a NOS-like activity.

  15. Beta-aminobutyric acid priming of plant defense: the role of ABA and other hormones.

    PubMed

    Baccelli, Ivan; Mauch-Mani, Brigitte

    2016-08-01

    Plants are exposed to recurring biotic and abiotic stresses that can, in extreme situations, lead to substantial yield losses. With the changing environment, the stress pressure is likely to increase and sustainable measures to alleviate the effect on our crops are sought. Priming plants for better stress resistance is one of the sustainable possibilities to reach this goal. Here, we report on the effects of beta-aminobutyric acid, a priming agent with an exceptionally wide range of action and describe its way of preparing plants to defend themselves against various attacks, among others through the modulation of their hormonal defense signaling, and highlight the special role of abscisic acid in this process.

  16. Chemical inhibition of potato ABA-8'-hydroxylase activity alters in vitro and in vivo ABA metabolism and endogenous ABA levels but does not affect potato microtuber dormancy duration.

    PubMed

    Suttle, Jeffrey C; Abrams, Suzanne R; De Stefano-Beltrán, Luis; Huckle, Linda L

    2012-09-01

    The effects of azole-type P450 inhibitors and two metabolism-resistant abscisic acid (ABA) analogues on in vitro ABA-8'-hydroxylase activity, in planta ABA metabolism, endogenous ABA content, and tuber meristem dormancy duration were examined in potato (Solanum tuberosum L. cv. Russet Burbank). When functionally expressed in yeast, three potato CYP707A genes were demonstrated to encode enzymatically active ABA-8'-hydroxylases with micromolar affinities for (+)-ABA. The in vitro activity of the three enzymes was inhibited by the P450 azole-type inhibitors ancymidol, paclobutrazol, diniconazole, and tetcyclasis, and by the 8'-acetylene- and 8'-methylene-ABA analogues, with diniconazole and tetcyclasis being the most potent inhibitors. The in planta metabolism of [(3)H](±)-ABA to phaseic acid and dihydrophaseic acid in tuber meristems was inhibited by diniconazole, tetcyclasis, and to a lesser extent by 8'-acetylene- and 8'-methylene-ABA. Continuous exposure of in vitro generated microtubers to diniconazole resulted in a 2-fold increase in endogenous ABA content and a decline in dihydrophaseic acid content after 9 weeks of development. Similar treatment with 8'-acetylene-ABA had no effects on the endogenous contents of ABA or phaseic acid but reduced the content of dihydrophaseic acid. Tuber meristem dormancy progression was determined ex vitro in control, diniconazole-, and 8'-acetylene-ABA-treated microtubers following harvest. Continuous exposure to diniconazole during microtuber development had no effects on subsequent sprouting at any time point. Continuous exposure to 8'-acetylene-ABA significantly increased the rate of microtuber sprouting. The results indicate that, although a decrease in ABA content is a hallmark of tuber dormancy progression, the decline in ABA levels is not a prerequisite for dormancy exit and the onset of tuber sprouting.

  17. Genetic analysis of Physcomitrella patens identifies ABSCISIC ACID NON-RESPONSIVE, a regulator of ABA responses unique to basal land plants and required for desiccation tolerance

    SciTech Connect

    Stevenson, Sean Ross; Kamisugi, Yasuko; Trinh, Chi H.; Schmutz, Jeremy; Jenkins, Jerry W.; Grimwood, Jane; Muchero, Wellington; Tuskan, Gerald A.; Rensing, Stefan A.; Lang, Daniel; Reski, Ralf; Melkonian, Michael; Rothfels, Carl J.; Li, Fay -Wei; Larsson, Anders; Wong, Gane Ka-Shu; Edwards, Thomas A.; Cuming, Andrew C.

    2016-05-18

    The anatomically simple plants that first colonized land must have acquired molecular and biochemical adaptations to drought stress. Abscisic acid (ABA) coordinates responses leading to desiccation tolerance in all land plants. We identified ABA nonresponsive mutants in the model bryophyte Physcomitrella patens and genotyped a segregating population to map and identify the ABA NON-RESPONSIVE (ANR) gene encoding a modular protein kinase comprising an N-terminal PAS domain, a central EDR domain, and a C-terminal MAPKKK-like domain. anr mutants fail to accumulate dehydration tolerance-associated gene products in response to drought, ABA, or osmotic stress and do not acquire ABA-dependent desiccation tolerance. The crystal structure of the PAS domain, determined to 1.7-Å resolution, shows a conserved PAS-fold that dimerizes through a weak dimerization interface. Targeted mutagenesis of a conserved tryptophan residue within the PAS domain generates plants with ABA nonresponsive growth and strongly attenuated ABA-responsive gene expression, whereas deleting this domain retains a fully ABA-responsive phenotype. ANR orthologs are found in early-diverging land plant lineages and aquatic algae but are absent from more recently diverged vascular plants. Lastly, we propose that ANR genes represent an ancestral adaptation that enabled drought stress survival of the first terrestrial colonizers but were lost during land plant evolution.

  18. ACTION OF AUXIN ON LEAF ABSCISSION

    DTIC Science & Technology

    Experiments have been conducted to investigate a two-stage effect of auxin on abscission. The two stages were demonstrated on greenhouse-grown Black...the second stage - the stage which is stimulated by auxin . Similar experiments were performed with petioles of various lengths and ages. The...implications of these results indicate possible sites of auxin action on leaf abscission. (Author)

  19. ROLE OF ETHYLENE IN LEAF ABSCISSION

    DTIC Science & Technology

    position of application. The positional effects of auxin are explained as being due to differences in transport in the explant. Thus, distally applied auxin ...inhibits abscission regardless of the accelerated rate of ethylene evolution by being rapidly transported to the abscission zone. Auxin applied

  20. Expression analysis of abscisic acid (ABA) and metabolic signalling factors in developing endosperm and embryo of barley☆

    PubMed Central

    Chen, Zhiwei; Huang, Jianhua; Muttucumaru, Nira; Powers, Stephen J.; Halford, Nigel G.

    2013-01-01

    The expression of genes encoding components of ABA and metabolic signalling pathways in developing barley endosperm and embryo was investigated. The genes included HvRCAR35_47387 and HvRCAR35_2538 (encoding ABA receptors), HvABI1d (protein phosphatase 2C), HvSnRK2.4, HvSnRK2.6 and HvPKABA1 (SnRK2-type protein kinases) and HvABI5 (ABA response element binding protein; AREBP), as well as two genes encoding SnRK1-type protein kinases. Both SnRK1 and SnRK2 phosphorylate AREBPs, but SnRK2 is activated by ABA whereas SnRK1 may be broken down. Multiple cereal AREBPs with two conserved SnRK1/2 target sites and another class of BZIP transcription factors with SnRK1/2 binding sites, including HvBLZ1, were identified. Barley grain (cv. Triumph) was sampled at 15, 20, 25 and 30 days post-anthesis (dpa). HvRCAR35_47387, HvABI1d, HvSnRK2.4 and HvABI5 were expressed highly in the endosperm but at much lower levels in the embryo. Conversely, HvPKABA1 and HvRCAR35_2538 were expressed at higher levels in the embryo than the endosperm, while HvSnRK2.6 was expressed at similar levels in both. HvRCAR35_47387, HvABI1d, HvSnRK2.4 and HvABI5 all peaked in expression in the endosperm at 20 dpa. A model is proposed in which ABA brings about a transition from a SnRK1-dominated state in the endosperm during grain filling to a SnRK2-dominated state during maturation. PMID:24748715

  1. Expression analysis of abscisic acid (ABA) and metabolic signalling factors in developing endosperm and embryo of barley.

    PubMed

    Chen, Zhiwei; Huang, Jianhua; Muttucumaru, Nira; Powers, Stephen J; Halford, Nigel G

    2013-09-01

    The expression of genes encoding components of ABA and metabolic signalling pathways in developing barley endosperm and embryo was investigated. The genes included HvRCAR35_47387 and HvRCAR35_2538 (encoding ABA receptors), HvABI1d (protein phosphatase 2C), HvSnRK2.4, HvSnRK2.6 and HvPKABA1 (SnRK2-type protein kinases) and HvABI5 (ABA response element binding protein; AREBP), as well as two genes encoding SnRK1-type protein kinases. Both SnRK1 and SnRK2 phosphorylate AREBPs, but SnRK2 is activated by ABA whereas SnRK1 may be broken down. Multiple cereal AREBPs with two conserved SnRK1/2 target sites and another class of BZIP transcription factors with SnRK1/2 binding sites, including HvBLZ1, were identified. Barley grain (cv. Triumph) was sampled at 15, 20, 25 and 30 days post-anthesis (dpa). HvRCAR35_47387, HvABI1d, HvSnRK2.4 and HvABI5 were expressed highly in the endosperm but at much lower levels in the embryo. Conversely, HvPKABA1 and HvRCAR35_2538 were expressed at higher levels in the embryo than the endosperm, while HvSnRK2.6 was expressed at similar levels in both. HvRCAR35_47387, HvABI1d, HvSnRK2.4 and HvABI5 all peaked in expression in the endosperm at 20 dpa. A model is proposed in which ABA brings about a transition from a SnRK1-dominated state in the endosperm during grain filling to a SnRK2-dominated state during maturation.

  2. Cell Wall Remodeling in Abscission Zone Cells during Ethylene-Promoted Fruit Abscission in Citrus.

    PubMed

    Merelo, Paz; Agustí, Javier; Arbona, Vicent; Costa, Mário L; Estornell, Leandro H; Gómez-Cadenas, Aurelio; Coimbra, Silvia; Gómez, María D; Pérez-Amador, Miguel A; Domingo, Concha; Talón, Manuel; Tadeo, Francisco R

    2017-01-01

    Abscission is a cell separation process by which plants can shed organs such as fruits, leaves, or flowers. The process takes place in specific locations termed abscission zones. In fruit crops like citrus, fruit abscission represents a high percentage of annual yield losses. Thus, understanding the molecular regulation of abscission is of capital relevance to control production. To identify genes preferentially expressed within the citrus fruit abscission zone (AZ-C), we performed a comparative transcriptomics assay at the cell type resolution level between the AZ-C and adjacent fruit rind cells (non-abscising tissue) during ethylene-promoted abscission. Our strategy combined laser microdissection with microarray analysis. Cell wall modification-related gene families displayed prominent representation in the AZ-C. Phylogenetic analyses of such gene families revealed a link between phylogenetic proximity and expression pattern during abscission suggesting highly conserved roles for specific members of these families in abscission. Our transcriptomic data was validated with (and strongly supported by) a parallel approach consisting on anatomical, histochemical and biochemical analyses on the AZ-C during fruit abscission. Our work identifies genes potentially involved in organ abscission and provides relevant data for future biotechnology approaches aimed at controlling such crucial process for citrus yield.

  3. Cell Wall Remodeling in Abscission Zone Cells during Ethylene-Promoted Fruit Abscission in Citrus

    PubMed Central

    Merelo, Paz; Agustí, Javier; Arbona, Vicent; Costa, Mário L.; Estornell, Leandro H.; Gómez-Cadenas, Aurelio; Coimbra, Silvia; Gómez, María D.; Pérez-Amador, Miguel A.; Domingo, Concha; Talón, Manuel; Tadeo, Francisco R.

    2017-01-01

    Abscission is a cell separation process by which plants can shed organs such as fruits, leaves, or flowers. The process takes place in specific locations termed abscission zones. In fruit crops like citrus, fruit abscission represents a high percentage of annual yield losses. Thus, understanding the molecular regulation of abscission is of capital relevance to control production. To identify genes preferentially expressed within the citrus fruit abscission zone (AZ-C), we performed a comparative transcriptomics assay at the cell type resolution level between the AZ-C and adjacent fruit rind cells (non-abscising tissue) during ethylene-promoted abscission. Our strategy combined laser microdissection with microarray analysis. Cell wall modification-related gene families displayed prominent representation in the AZ-C. Phylogenetic analyses of such gene families revealed a link between phylogenetic proximity and expression pattern during abscission suggesting highly conserved roles for specific members of these families in abscission. Our transcriptomic data was validated with (and strongly supported by) a parallel approach consisting on anatomical, histochemical and biochemical analyses on the AZ-C during fruit abscission. Our work identifies genes potentially involved in organ abscission and provides relevant data for future biotechnology approaches aimed at controlling such crucial process for citrus yield. PMID:28228766

  4. Overexpression of INFLORESCENCE DEFICIENT IN ABSCISSION activates cell separation in vestigial abscission zones in Arabidopsis.

    PubMed

    Stenvik, Grethe-Elisabeth; Butenko, Melinka A; Urbanowicz, Breeanna Rae; Rose, Jocelyn K C; Aalen, Reidunn B

    2006-06-01

    Plants may shed organs when they have been injured or served their purpose. The differential pattern of organ abscission in different species is most likely the result of evolutionary adaptation to a variety of life styles and environments. The final step of abscission-related cell separation in floral organs of wild-type Arabidopsis thaliana, which only abscises sepals, petals, and stamens, is controlled by INFLORESCENCE DEFICIENT IN ABSCISSION (IDA). Here, we demonstrate that Arabidopsis 35S:IDA lines constitutively overexpressing IDA exhibit earlier abscission of floral organs, showing that the abscission zones are responsive to IDA soon after the opening of the flowers. In addition, ectopic abscission was observed at the bases of the pedicel, branches of the inflorescence, and cauline leaves. The silique valves also dehisced prematurely. Scanning electron microscopy indicated a spread of middle lamella degradation from preformed abscission zone cells to neighboring cells. A transcript encoding an arabinogalactan protein (AGP) was upregulated in the 35S:IDA lines, and large amounts of AGP were secreted at the sites of abscission. AGP was shown to be a constituent of wild-type floral abscission zones during and soon after cell separation had been completed. We suggest that the restricted expression pattern of IDA precludes abscission of nonfloral organs in Arabidopsis.

  5. Variations in the mycorrhization characteristics in roots of wild-type and ABA-deficient tomato are accompanied by specific transcriptomic alterations.

    PubMed

    Garrido, José Manuel García; Morcillo, Rafael Jorge León; Rodríguez, José Angel Martín; Bote, Juan Antonio Ocampo

    2010-05-01

    Abscissic acid (ABA) determines mycorrhiza functionality and arbuscule development. In this study, we performed transcriptome analysis in response to different mycorrhization status according to the ABA content in the root to identify genes that may play a role in arbuscule functionality. Affymetrix Tomato GeneChip (approximately 10,000 probes) allowed us to detect and compare the transcriptional root profiling of tomato (Solanum lycopersicum) wild-type and ABA-deficient sitiens plants colonized by Glomus intraradices. A number of identified genes in tomato belong to a category of genes already described as "mycorrhizal core-set" in other host plants. The impairment in arbuscular mycorrhiza (AM) formation in ABA-deficient mutants was associated with upregulation of genes related to defense and cell wall modification, whereas functional mycorrhization in wild-type plants was associated with activation of genes related to isoprenoid metabolism. The oxylipin pathway was activated in tomato mycorrhizal roots at late stages of interaction, and was related to the control of fungal spread in roots, not with the establishment of the symbiosis. Induction of selected genes, representing a range of biological functions and representative of the three sets of genes specifically upregulated in the different plant phenotype, was confirmed by quantitative reverse-transcription polymerase chain reaction, and their response to phythohormone treatment was tested, showing that ethylene and jasmonic acid are key regulators of gene expression during AM development. Comparative analysis of mycorrhiza upregulated functional categories revealed significant changes in gene expression associated with the different mycorrhization status according to the ABA content in the roots.

  6. Identification and mechanism of ABA receptor antagonism

    SciTech Connect

    Melcher, Karsten; Xu, Yong; Ng, Ley-Moy; Zhou, X. Edward; Soon, Fen-Fen; Chinnusamy, Viswanathan; Suino-Powell, Kelly M; Kovach, Amanda; Tham, Fook S.; Cutler, Sean R.; Li, Jun; Yong, Eu-Leong; Zhu, Jian-Kang; Xu, H. Eric

    2010-11-11

    The phytohormone abscisic acid (ABA) functions through a family of fourteen PYR/PYL receptors, which were identified by resistance to pyrabactin, a synthetic inhibitor of seed germination. ABA activates these receptors to inhibit type 2C protein phosphatases, such as ABI1, yet it remains unclear whether these receptors can be antagonized. Here we demonstrate that pyrabactin is an agonist of PYR1 and PYL1 but is unexpectedly an antagonist of PYL2. Crystal structures of the PYL2-pyrabactin and PYL1-pyrabactin-ABI1 complexes reveal the mechanism responsible for receptor-selective activation and inhibition, which enables us to design mutations that convert PYL1 to a pyrabactin-inhibited receptor and PYL2 to a pyrabactin-activated receptor and to identify new pyrabactin-based ABA receptor agonists. Together, our results establish a new concept of ABA receptor antagonism, illustrate its underlying mechanisms and provide a rational framework for discovering novel ABA receptor ligands.

  7. Brassinosteroids modulate ABA-induced stomatal closure in Arabidopsis

    PubMed Central

    Ha, Yunmi; Shang, Yun; Nam, Kyoung Hee

    2016-01-01

    Stomatal movement in response to water availability is an important physiological process in the survival of land plants. The plant hormone abscisic acid (ABA) and brassinosteroids (BRs) regulate stomatal closure. The physiological functions of ABA and BRs, including germination, cell elongation and stomatal movement, are generally known to be antagonistic. Here, we investigated how BRs affect stomatal movement alone and in combination with ABA. We demonstrate that brassinoslide (BL), the most active BR, promotes stomatal closure in an ABA-independent manner. Interestingly, BL also inhibited ABA-induced stomatal closure when a high concentration of BL was added to ABA. Furthermore, we found that the induction of some genes for reactive oxygen species (ROS) generation by ABA (AtrbohD, NIA1 and NIA2) and subsequent ROS production were repressed by BL treatment. The BR signaling mutant bri1-301 failed to inhibit ABA-induced stomatal closure upon BL treatment. However, BRI1-overexpressing transgenic plants were hypersensitive to ABA during stomatal closure, and BL reversed ABA-induced stomatal closure more completely than in wild type plants. Taken together, these results suggest that BRs can positively and negatively modulate ABA-induced stomatal closure. Therefore, interactions between ABA and BR signaling are important for the regulation of stomatal closure. PMID:27856707

  8. Identification and Kinetics of Accumulation of Proteins Induced by Ethylene in Bean Abscission Zones 1

    PubMed Central

    del Campillo, Elena; Lewis, Lowell N.

    1992-01-01

    A two-dimensional gel electrophoresis system that combines a cationic polyacrylamide gel electrophoresis at pH near neutrality with sodium dodecyl sulfate-polyacrylamide gel electrophoresis was used to analyze the spectrum of basic polypeptides that accumulate in bean (Phaseolus vulgaris) abscission zones after treatment with ethylene. Results showed that, as abscission progressed, at least seven basic proteins accumulated in the abscission zone prior to the accumulation of 9.5 cellulase. Six of the seven proteins correspond to pathogenesis-related (PR) proteins. Among them, two isoforms of β-1,3-glucanase and multiple isoforms of chitinase were identified. A 22 kilodalton polypeptide that accumulated to high levels was identified as a thaumatin-like protein by analysis of its N-terminal sequence (up to 20 amino acids) and its serological relationship with heterologous thaumatin antibodies. A 15 kilodalton polypeptide serologically related to PR P1 (p14) from tomato was identified as bean PR P1 (p14)-like protein. The kinetics of accumulation of glucanases, chitinases, thaumatin-like and PR P1 (p14)-like proteins during ethylene treatment were similar and they showed that PR proteins accumulated in abscission zones prior to the increase in 9.5 cellulase. Addition of indoleacetic acid, a potent inhibitor of abscission, reduced the accumulation of these proteins to a similar extent (60%). The synchronized accumulation of this set of PR proteins, early in the abscission process, may play a role in induced resistance to possible fungal attack after a plant part is shed. The seventh protein does not correspond to any previously characterized PR protein. This new 45 kilodalton polypeptide accumulated in abscission zones on exposure to ethylene concomitantly with the increase in 9.5 cellulase. Its N-terminal sequence (up to 15 amino acids) showed some homology with the amino terminal sequence of chitinase. Polyclonal antibodies against chitinase recognized the 45

  9. Control of Abscission in Agricultural Crops and Its Physiological Basis 1

    PubMed Central

    Cooper, W. C.; Rasmussen, G. K.; Rogers, B. J.; Reece, P. C.; Henry, W. H.

    1968-01-01

    Some naphthalene and phenoxy compounds prevent preharvest drop of apples, pears, and citrus fruits. These studies have been complicated by an unrecognized high level of ethylene produced by leaves and fruit on trees sprayed with these growth regulators. An apparent contradiction is the effectiveness of both 2,4-dichlorophenoxyacetic acid and n-dimethylaminosuccinamic acid (a growth retardant which retards biosynthesis of auxin) in preventing abscission of apples. Thus, in the presence of low auxin concentrations in the tissue, this growth retardant prevents fruit abscission even more effectively than 2,4-dichlorophenoxyacetic acid at high auxin concentrations in the tissue. This anomaly is clarified on the basis that n-dimethylaminosuccinamic acid, in the presence of a known low ethylene biosynthesis, delays maturity of the fruit and thus prevents fruit abscission. On the other hand, 2,4-dichlorophenoxyacetic acid prevents abscission by direct growth hormone action, in spite of the side effects of ethylene production which speeds ripening of the fruit. With the promotion of abscission of leaves and fruit of agricultural crops, attention is given to the use of chemicals which induce ethylene production when applied to the plant, but which have no growth promotion effect to retard abscission. We can distinguish 5 kinds of such chemicals. One group includes gibberellic and abscisic acids that induce treated leaves to produce ethylene and abscise (under certain circumstances). However, they do not induce ethylene production by fruit and do not promote fruit abscission. A second group includes ascorbic acid, which, when used at relatively high levels, induces fruit to produce enough ethylene to promote abscission. Ascorbic acid-treated leaves also produce ethylene but not enough to cause much defoliation. A third group includes protein-synthesis inhibitors, such as cycloheximide. When low concentrations (about 30 μmoles/l) are sprayed on the fruit, the rapid effect of

  10. PLASTID MOVEMENT IMPAIRED1 mediates ABA sensitivity during germination and implicates ABA in light-mediated Chloroplast movements.

    PubMed

    Rojas-Pierce, Marcela; Whippo, Craig W; Davis, Phillip A; Hangarter, Roger P; Springer, Patricia S

    2014-10-01

    The plant hormone abscisic acid (ABA) controls many aspects of plant growth and development, including seed development, germination and responses to water-deficit stress. A complex ABA signaling network integrates environmental signals including water availability and light intensity and quality to fine-tune the response to a changing environment. To further define the regulatory pathways that control water-deficit and ABA responses, we carried out a gene-trap tagging screen for water-deficit-regulated genes in Arabidopsis thaliana. This screen identified PLASTID MOVEMENT IMPAIRED1 (PMI1), a gene involved in blue-light-induced chloroplast movement, as functioning in ABA-response pathways. We provide evidence that PMI1 is involved in the regulation of seed germination by ABA, acting upstream of the intersection between ABA and low-glucose signaling pathways. Furthermore, PMI1 participates in the regulation of ABA accumulation during periods of water deficit at the seedling stage. The combined phenotypes of pmi1 mutants in chloroplast movement and ABA responses indicate that ABA signaling may modulate chloroplast motility. This result was further supported by the detection of altered chloroplast movements in the ABA mutants aba1-6, aba2-1 and abi1-1.

  11. Wounding of potato tubers induces increases in ABA biosynthesis and catabolism and alters expression of ABA metabolic genes.

    PubMed

    Suttle, Jeffrey C; Lulai, Edward C; Huckle, Linda L; Neubauer, Jonathan D

    2013-04-15

    The effects of physical wounding on ABA biosynthesis and catabolism and expression of genes encoding key ABA metabolic enzymes were determined in potato tubers. An increase in ABA and ABA metabolite content was observed 48h after wounding and remained elevated through 96h. Wounding induced dramatic increases in the expression of the ABA metabolic genes encoding zeaxanthin epoxidase (ZEP), 9-cis-epoxycarotenoid dioxygenase (NCED), and ABA-8'-hydroxylase. Although the patterns of wound-induced expression of individual genes varied, increased gene expression was observed within 3h of wounding and remained elevated through 96h. An apparent correlation between expression of the gene encoding ZEP and the increase in ABA content suggested that the wound-induced increase in ABA biosynthesis was regulated by both substrate availability and increased NCED activity. Suppression of wound-induced jasmonic acid accumulation by rinsing the wounded tissue with water did not inhibit the subsequent increase in ABA content. Exogenous ethylene completely suppressed the wound-induced increase in ABA content and dramatically reduced wound-induced up-regulation of ABA metabolic genes. This study is the first to identify the molecular bases for increased ABA accumulation following physical trauma in potato tubers and highlights the complex physiological interactions between various wound-induced hormones.

  12. Polyamine-induced modulation of genes involved in ethylene biosynthesis and signalling pathways and nitric oxide production during olive mature fruit abscission

    PubMed Central

    Parra-Lobato, Maria C.; Gomez-Jimenez, Maria C.

    2011-01-01

    After fruit ripening, many fruit-tree species undergo massive natural fruit abscission. Olive (Olea europaea L.) is a stone-fruit with cultivars such as Picual (PIC) and Arbequina (ARB) which differ in mature fruit abscission potential. Ethylene (ET) is associated with abscission, but its role during mature fruit abscission remains largely uncharacterized. The present study investigates the possible roles of ET and polyamine (PA) during mature fruit abscission by modulating genes involved in the ET signalling and biosynthesis pathways in the abscission zone (AZ) of both cultivars. Five ET-related genes (OeACS2, OeACO2, OeCTR1, OeERS1, and OeEIL2) were isolated in the AZ and adjacent cells (AZ–AC), and their expression in various olive organs and during mature fruit abscission, in relation to interactions between ET and PA and the expression induction of these genes, was determined. OeACS2, OeACO2, and OeEIL2 were found to be the only genes that were up-regulated in association with mature fruit abscission. Using the inhibition of ET and PA biosynthesis, it is demonstrated that OeACS2 and OeEIL2 expression are under the negative control of PA while ET induces their expression in AZ–AC. Furthermore, mature fruit abscission depressed nitric oxide (NO) production present mainly in the epidermal cells and xylem of the AZ. Also, NO production was differentially responsive to ET, PA, and different inhibitors. Taken together, the results indicate that PA-dependent ET signalling and biosynthesis pathways participate, at least partially, during mature fruit abscission, and that endogenous NO and 1-aminocyclopropane-1-carboxylic acid maintain an inverse correlation, suggesting an antagonistic action of NO and ET in abscission signalling. PMID:21633085

  13. Understanding the Physiology of Postharvest Needle Abscission in Balsam Fir.

    PubMed

    Lada, Rajasekaran R; MacDonald, Mason T

    2015-01-01

    Balsam fir (Abies balsamea) trees are commonly used as a specialty horticultural species for Christmas trees and associated greenery in eastern Canada and United States. Postharvest needle abscission has always been a problem, but is becoming an even bigger challenge in recent years presumably due to increased autumn temperatures and earlier harvesting practices. An increased understanding of postharvest abscission physiology in balsam fir may benefit the Christmas tree industry while simultaneously advancing our knowledge in senescence and abscission of conifers in general. Our paper describes the dynamics of needle abscission in balsam fir while identifying key factors that modify abscission patterns. Concepts such as genotypic abscission resistance, nutrition, environmental factors, and postharvest changes in water conductance and hormone evolution are discussed as they relate to our understanding of the balsam fir abscission physiology. Our paper ultimately proposes a pathway for needle abscission via ethylene and also suggests other potential alternative pathways based on our current understanding.

  14. Understanding the Physiology of Postharvest Needle Abscission in Balsam Fir

    PubMed Central

    Lada, Rajasekaran R.; MacDonald, Mason T.

    2015-01-01

    Balsam fir (Abies balsamea) trees are commonly used as a specialty horticultural species for Christmas trees and associated greenery in eastern Canada and United States. Postharvest needle abscission has always been a problem, but is becoming an even bigger challenge in recent years presumably due to increased autumn temperatures and earlier harvesting practices. An increased understanding of postharvest abscission physiology in balsam fir may benefit the Christmas tree industry while simultaneously advancing our knowledge in senescence and abscission of conifers in general. Our paper describes the dynamics of needle abscission in balsam fir while identifying key factors that modify abscission patterns. Concepts such as genotypic abscission resistance, nutrition, environmental factors, and postharvest changes in water conductance and hormone evolution are discussed as they relate to our understanding of the balsam fir abscission physiology. Our paper ultimately proposes a pathway for needle abscission via ethylene and also suggests other potential alternative pathways based on our current understanding. PMID:26635863

  15. Abscission, organ separation, is more complex than you might think

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Abscission, organ separation, is an integral part of the life of a plant. Natural and artificial regulation of abscission can have substantive effects on crop yield and fruit quality. It’s been nearly 100 years since the discovery that ethylene played a role in abscission and more than 50 years si...

  16. Activation of dimeric ABA receptors elicits guard cell closure, ABA-regulated gene expression, and drought tolerance

    PubMed Central

    Okamoto, Masanori; Peterson, Francis C.; Defries, Andrew; Park, Sang-Youl; Endo, Akira; Nambara, Eiji; Volkman, Brian F.; Cutler, Sean R.

    2013-01-01

    Abscisic acid (ABA) is an essential molecule in plant abiotic stress responses. It binds to soluble pyrabactin resistance1/PYR1-like/regulatory component of ABA receptor receptors and stabilizes them in a conformation that inhibits clade A type II C protein phosphatases; this leads to downstream SnRK2 kinase activation and numerous cellular outputs. We previously described the synthetic naphthalene sulfonamide ABA agonist pyrabactin, which activates seed ABA responses but fails to trigger substantial responses in vegetative tissues in Arabidopsis thaliana. Here we describe quinabactin, a sulfonamide ABA agonist that preferentially activates dimeric ABA receptors and possesses ABA-like potency in vivo. In Arabidopsis, the transcriptional responses induced by quinabactin are highly correlated with those induced by ABA treatments. Quinabactin treatments elicit guard cell closure, suppress water loss, and promote drought tolerance in adult Arabidopsis and soybean plants. The effects of quinabactin are sufficiently similar to those of ABA that it is able to rescue multiple phenotypes observed in the ABA-deficient mutant aba2. Genetic analyses show that quinabactin’s effects in vegetative tissues are primarily mediated by dimeric ABA receptors. A PYL2-quinabactin-HAB1 X-ray crystal structure solved at 1.98-Å resolution shows that quinabactin forms a hydrogen bond with the receptor/PP2C “lock” hydrogen bond network, a structural feature absent in pyrabactin-receptor/PP2C complexes. Our results demonstrate that ABA receptors can be chemically controlled to enable plant protection against water stress and define the dimeric receptors as key targets for chemical modulation of vegetative ABA responses. PMID:23818638

  17. Activation of dimeric ABA receptors elicits guard cell closure, ABA-regulated gene expression, and drought tolerance.

    PubMed

    Okamoto, Masanori; Peterson, Francis C; Defries, Andrew; Park, Sang-Youl; Endo, Akira; Nambara, Eiji; Volkman, Brian F; Cutler, Sean R

    2013-07-16

    Abscisic acid (ABA) is an essential molecule in plant abiotic stress responses. It binds to soluble pyrabactin resistance1/PYR1-like/regulatory component of ABA receptor receptors and stabilizes them in a conformation that inhibits clade A type II C protein phosphatases; this leads to downstream SnRK2 kinase activation and numerous cellular outputs. We previously described the synthetic naphthalene sulfonamide ABA agonist pyrabactin, which activates seed ABA responses but fails to trigger substantial responses in vegetative tissues in Arabidopsis thaliana. Here we describe quinabactin, a sulfonamide ABA agonist that preferentially activates dimeric ABA receptors and possesses ABA-like potency in vivo. In Arabidopsis, the transcriptional responses induced by quinabactin are highly correlated with those induced by ABA treatments. Quinabactin treatments elicit guard cell closure, suppress water loss, and promote drought tolerance in adult Arabidopsis and soybean plants. The effects of quinabactin are sufficiently similar to those of ABA that it is able to rescue multiple phenotypes observed in the ABA-deficient mutant aba2. Genetic analyses show that quinabactin's effects in vegetative tissues are primarily mediated by dimeric ABA receptors. A PYL2-quinabactin-HAB1 X-ray crystal structure solved at 1.98-Å resolution shows that quinabactin forms a hydrogen bond with the receptor/PP2C "lock" hydrogen bond network, a structural feature absent in pyrabactin-receptor/PP2C complexes. Our results demonstrate that ABA receptors can be chemically controlled to enable plant protection against water stress and define the dimeric receptors as key targets for chemical modulation of vegetative ABA responses.

  18. A petal breakstrength meter for Arabidopsis abscission studies

    PubMed Central

    Lease, Kevin A; Cho, Sung Ki; Walker, John C

    2006-01-01

    Background Abscission is the regulated dropping of plant organs, such as leaves or flower petals. This process involves a break down of the cell wall between layers of cells in the abscission zone, causing the organ to become detached. The model plant Arabidopsis thaliana undergoes floral organ abscission. Various experimental methods have been used to study Arabidopsis floral organ abscission, including measuring the petal breakstrength, or the amount of force required to pull a petal from the receptacle. Petal breakstrength provides a quantitative insight into the physical integrity of the petal abscission zone. Results We developed a petal breakstrength meter that allows rapid data acquisition on a personal computer. We present the design of the device and show its utility in measuring Arabidopsis petal breakstrength for abscission studies. Conclusion This petal breakstrength meter should enable researchers to perform the petal breakstrength assay as a routine part of the characterization of environmental and genetic factors affecting abscission. PMID:16483376

  19. Characterization of potential ABA receptors in Vitis vinifera.

    PubMed

    Boneh, Uri; Biton, Iris; Zheng, Chuanlin; Schwartz, Amnon; Ben-Ari, Giora

    2012-02-01

    Molecular control mechanisms for abiotic stress tolerance are based on the activation and regulation of specific stress-related genes. The phytohormone abscisic acid (ABA) is a key endogenous messenger in a plant's response to such stresses. A novel ABA binding mechanism which plays a key role in plant cell signaling cascades has recently been uncovered. In the absence of ABA, a type 2C protein phosphatase (PP2C) interacts and inhibits the kinase SnRK2. Binding of ABA to the PYR/PYLs receptors enables interaction between the ABA receptor and the PP2C protein, and abrogates the SnRK2 inactivation. The active SnRK2 is then free to activate the ABA-responsive element Binding Factors which target ABA-dependent gene expression. We used the grape as a model to study the ABA perception mechanism in fruit trees. The grape ABA signaling cascade consists of at least seven ABA receptors and six PP2Cs. We used a yeast two-hybrid system to examine physical interaction in vitro between the grape ABA receptors and their interacting partners, and found that twenty-two receptor-PP2C interactions can occur. Moreover, quantifying these affinities by the use of the LacZ reporter enables us to show that VvPP2C4 and VvPP2C9 are the major binding partners of the ABA receptor. We also tested in vivo the root and leaf gene expression of the various ABA receptors and PP2Cs in the presence of exogenic ABA and under different abiotic stresses such as high salt concentration, cold and drought, and found that many of these genes are regulated by such abiotic environmental factors. Our results indicate organ specificity in the ABA receptor genes and stress specificity in the VvPP2Cs. We suggest that VvPP2C4 is the major PP2C involved in ABA perception in leaves and roots, and VvRCAR6 and VvRCAR5 respectively, are the major receptors involved in ABA perception in these organs. Identification, characterization and manipulation of the central players in the ABA signaling cascades in fruit trees is

  20. Molecular cloning and characterization of the ABA-specific glucosyltransferase gene from bean (Phaseolus vulgaris L.).

    PubMed

    Palaniyandi, Sasikumar Arunachalam; Chung, Gyuhwa; Kim, Sang Hyon; Yang, Seung Hwan

    2015-04-15

    Levels of the plant hormone abscisic acid (ABA) are maintained in homeostasis by a balance of its biosynthesis, catabolism and conjugation. The detailed molecular and signaling events leading to strict homeostasis are not completely understood in crop plants. In this study, we obtained cDNA of an ABA-inducible, ABA-specific UDP-glucosyltransferase (ABAGT) from the bean plant (Phaseolus vulgaris L.) involved in conjugation of a glucose residue to ABA to form inactive ABA-glucose ester (ABA-GE) to examine its role during development and abiotic stress in bean. The bacterially expressed PvABAGTase enzyme showed ABA-specific glucosylation activity in vitro. A higher level of the PvABAGT transcript was observed in mature leaves, mature flowers, roots, seed coats and embryos as well as upon rehydration following a period of dehydration. Overexpression of 35S::PvABAGT in Arabidopsis showed reduced sensitivity to ABA compared with WT. The transgenic plants showed a high level of ABA-GE without significant decrease in the level of ABA compared with the wild type (WT) during dehydration stress. Upon rehydration, the levels of ABA and phaseic acid (PA) decreased in the WT and the PvABAGT-overexpressing lines with high levels of ABA-GE only in the transgenic plants. Our findings suggest that the PvABAGT gene could play a role in ABA homeostasis during development and stress responses in bean and its overexpression in Arabidopsis did not alter ABA homeostasis during dehydration stress.

  1. The Heat Stress Factor HSFA6b Connects ABA Signaling and ABA-Mediated Heat Responses1[OPEN

    PubMed Central

    Yang, Chen-Ru

    2016-01-01

    Heat stress response (HSR) is a conserved mechanism developed to increase the expression of heat shock proteins (HSPs) via a heat shock factor (HSF)-dependent mechanism. Signaling by the stress phytohormone abscisic acid (ABA) is involved in acquired thermotolerance as well. Analysis of Arabidopsis (Arabidopsis thaliana) microarray databases revealed that the expression of HSFA6b, a class A HSF, extensively increased with salinity, osmotic, and cold stresses, but not heat. Here, we show that HSFA6b plays a pivotal role in the response to ABA and in thermotolerance. Salt-inducible HSFA6b expression was down-regulated in ABA-insensitive and -deficient mutants; however, exogenous ABA application restored expression in ABA-deficient, but not -insensitive plants. Thus, ABA signaling is required for proper HSFA6b expression. A transcriptional activation assay of protoplasts revealed that ABA treatment and coexpression of an ABA signaling master effector, ABA-RESPONSIVE ELEMENT-BINDING PROTEIN1, could activate the HSFA6b promoter. In addition, HSFA6b directly bound to the promoter of DEHYDRATION-RESPONSIVE ELEMENT-BINDING PROTEIN2A and enhanced its expression. Analysis of ABA responses in seed germination, cotyledon greening, and root growth as well as salt and drought tolerance in HSFA6b-null, overexpression, and dominant negative mutants revealed that HSFA6b is a positive regulator participating in ABA-mediated salt and drought resistance. Thermoprotection tests showed that HSFA6b was required for thermotolerance acquisition. Our study reveals a network in which HSFA6b operates as a downstream regulator of the ABA-mediated stress response and is required for heat stress resistance. This new ABA-signaling pathway is integrated into the complex HSR network in planta. PMID:27493213

  2. Wheat ABA-insensitive mutants result in reduced grain dormancy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This paper describes the isolation of wheat mutants in the hard red spring Scarlet resulting in reduced sensitivity to the plant hormone abscisic acid (ABA) during seed germination. ABA induces seed dormancy during embryo maturation and inhibits the germination of mature seeds. Wheat sensitivity t...

  3. ABA and cytokinins: challenge and opportunity for plant stress research.

    PubMed

    Verslues, Paul E

    2016-08-01

    Accumulation of the stress hormone abscisic acid (ABA) induces many cellular mechanisms associated with drought resistance. Recent years have seen a rapid advance in our knowledge of how increased ABA levels are perceived by ABA receptors, particularly the PYL/RCAR receptors, but there has been relatively less new information about how ABA accumulation is controlled and matched to stress severity. ABA synthesis and catabolism, conjugation and deconjugation to glucose, and ABA transport all are involved in controlling ABA levels. This highly buffered system of ABA metabolism represents both a challenge and opportunity in developing a mechanistic understanding of how plants detect and respond to drought. Recent data have also shown that direct manipulation of cytokinin levels in transgenic plants has dramatic effect on drought phenotypes and prompted new interest in the role of cytokinins and cytokinin signaling in drought. Both ABA and cytokinins will continue to be major foci of drought research but likely with different trajectories both in terms of basic research and in translational research aimed at increasing plant performance during drought.

  4. ABA flow modelling in Ricinus communis exposed to salt stress and variable nutrition

    PubMed Central

    Peuke, Andreas D.

    2016-01-01

    In a series of experiments with Ricinus communis, abscisic acid (ABA) concentrations in tissues and transport saps, its de novo biosynthesis, long-distance transport, and metabolism (degradation) were affected by nutritional conditions, nitrogen (N) source, and nutrient limitation, or salt stress. In the present study these data were statistically re-evaluated, and new correlations presented that underpin the importance of this universal phytohormone. The biggest differences in ABA concentration were observed in xylem sap. N source had the strongest effect; however, nutrient limitation (particularly phosphorus limitation) and salt also had significant effects. ABA was found in greater concentration in phloem sap compared with xylem sap; however, the effect of treatment on ABA concentration in phloem was lower. In the leaves, ABA concentration was most variable compared with the other tissues. This variation was only affected by the N source. In roots, ABA was significantly decreased by nutrient limitation. Of the compartments in which ABA was quantified, xylem sap ABA concentration was most significantly correlated with leaf stomatal conductance and leaf growth. Additionally, ABA concentration in xylem was significantly correlated to that in phloem, indicating a 6-fold concentration increase from xylem to phloem. The ABA flow model showed that biosynthesis of ABA in roots affected the xylem flow of ABA. Moreover, ABA concentration in xylem affected the degradation of the phytohormone in shoots and also its export from shoots via phloem. The role of phloem transport is discussed since it stimulates ABA metabolism in roots. PMID:27440939

  5. An ABA-mimicking ligand that reduces water loss and promotes drought resistance in plants

    PubMed Central

    Cao, Minjie; Liu, Xue; Zhang, Yan; Xue, Xiaoqian; Zhou, X Edward; Melcher, Karsten; Gao, Pan; Wang, Fuxing; Zeng, Liang; Zhao, Yang; Zhao, Yang; Deng, Pan; Zhong, Dafang; Zhu, Jian-Kang; Xu, H Eric; Xu, Yong

    2013-01-01

    Abscisic acid (ABA) is the most important hormone for plants to resist drought and other abiotic stresses. ABA binds directly to the PYR/PYL family of ABA receptors, resulting in inhibition of type 2C phosphatases (PP2C) and activation of downstream ABA signaling. It is envisioned that intervention of ABA signaling by small molecules could help plants to overcome abiotic stresses such as drought, cold and soil salinity. However, chemical instability and rapid catabolism by plant enzymes limit the practical application of ABA itself. Here we report the identification of a small molecule ABA mimic (AM1) that acts as a potent activator of multiple members of the family of ABA receptors. In Arabidopsis, AM1 activates a gene network that is highly similar to that induced by ABA. Treatments with AM1 inhibit seed germination, prevent leaf water loss, and promote drought resistance. We solved the crystal structure of AM1 in complex with the PYL2 ABA receptor and the HAB1 PP2C, which revealed that AM1 mediates a gate-latch-lock interacting network, a structural feature that is conserved in the ABA-bound receptor/PP2C complex. Together, these results demonstrate that a single small molecule ABA mimic can activate multiple ABA receptors and protect plants from water loss and drought stress. Moreover, the AM1 complex crystal structure provides a structural basis for designing the next generation of ABA-mimicking small molecules. PMID:23835477

  6. Analysis of Gene Promoters for Two Tomato Polygalacturonases Expressed in Abscission Zones and the Stigma

    PubMed Central

    Hong, Seung-Beom; Sexton, Roy; Tucker, Mark L.

    2000-01-01

    The tomato (Lycopersicon esculentum cv Ailsa Craig) polygalacturonase genes TAPG1 (LYCes;Pga1;2) and TAPG4 (LYCes;Pga1;5) are abundantly expressed in both abscission zones and the pistils of mature flowers. To further investigate the spatial and temporal expression patterns for these genes, the TAPG gene promoters were ligated to β-glucuronidase (GUS) reporter genes and transformed into tomato. GUS expression with both constructs was similar and entirely consistent with the expression patterns of the native gene transcripts. GUS activity was observed in the weakening abscission zones of the leaf petiole, flower and fruit pedicel, flower corolla, and fruit calyx. In leaf petiole and flower pedicel zones this activity was enhanced by ethylene and inhibited by indole-3-acetic acid. On induction of abscission with ethylene, GUS accumulation was much earlier in TAPG4:GUS than in TAPG1:GUS transformants. Moreover, TAPG4:GUS staining appeared to predominate in the vascular bundles relative to surrounding cortex cells whereas TAPG1:GUS was more evenly distributed across the separation layer. Like the native genes, GUS was also expressed in the stigma. Activity was not apparent in pistils until the flowers had opened and was confined to the stigma and style immediately proximal to it. A minimal promoter construct consisting of a 247-bp 5′-upstream element from TAPG1 was found to be sufficient to direct GUS expression in both abscission zones and the stigma. PMID:10889236

  7. The Abscission Checkpoint: Making It to the Final Cut.

    PubMed

    Nähse, Viola; Christ, Liliane; Stenmark, Harald; Campsteijn, Coen

    2017-01-01

    Cytokinesis is the final stage of cell division and is concluded by abscission of the intercellular bridge to physically separate the daughter cells. Timing of cytokinetic abscission is monitored by a molecular machinery termed the abscission checkpoint. This machinery delays abscission in cells with persistent chromatin in the intercellular bridge. Recent work has also uncovered its response to high membrane tension, nuclear pore defects, and DNA replication stress. Although it is known that the abscission checkpoint depends on persistent activity of the Aurora B protein kinase, we have only recently begun to understand its molecular basis. We propose here a molecular framework for abscission checkpoint signaling and we discuss outstanding questions relating to its function and physiological relevance.

  8. Abscission of mango fruitlets as influenced by enhanced ethylene biosynthesis.

    PubMed

    Nunez-Elisea, R; Davenport, T L

    1986-12-01

    Experiments were conducted on developing fruitlet explants of two mango (Mangifera indica L.) cultivars to establish the source and dynamics of ethylene production prior to and during fruitlet abscission. Abscission of all fruits in the samples occurred at approximately 86 and 74 hours postharvest in ;Keitt' and ;Tommy Atkins,' respectively. Increased abscission began 26 hours from harvest and was preceded by enhanced ethylene synthesis. Enhanced ethylene production initiated approximately 48 hours prior to abscission and increased to a maximum near the time of fruitlet abscission. The seed produced the highest amount of ethylene on a per gram fresh weight basis. The pericarp, however, was the main source of ethylene on an absolute basis, since it represented more than 85% of total fruitlet weight. Pedicels containing the abscission zone produced no detectable ethylene prior to or at the moment of abscission. Fumigation of ;Tommy Atkins' fruitlets with 1, 15, or 100 microliters per liter ethylene accelerated abscission by 24 to 36 hours in comparison with unfumigated controls. Diffusion of ethylene from distal fruitlet tissues to the abscission zone triggers the events leading to separation of the fruit from the tree.

  9. Role of RNA and Protein Synthesis in Abscission

    PubMed Central

    Abeles, F. B.

    1968-01-01

    The cell separation aspect of abscission is thought to involve the action of specific cell wall degrading enzymes. Enzymes represent synthesis which in turn is preceded by the synthesis of specific RNA molecules, and it follows that inhibition of either of these processes would also block abscission. Since abscission is a localized phenomenon usually involving 2 or 3 cell layers, RNA and protein synthesis should also be localized. Manipulations of plant material which either accelerate or retard abscission may be due to the regulation of RNA and protein synthesis. This paper is a review of literature concerned with these and related questions. Images PMID:16657020

  10. Ethylene and flower longevity in Alstroemeria: relationship between tepal senescence, abscission and ethylene biosynthesis.

    PubMed

    Wagstaff, Carol; Chanasut, Usawadee; Harren, Frans J M; Laarhoven, Luc-Jan; Thomas, Brian; Rogers, Hilary J; Stead, Anthony D

    2005-03-01

    Senescence of floral organs is broadly divided into two groups: those that exhibit sensitivity to exogenous ethylene and those that do not. Endogenous ethylene production from the former group is via a well-characterized biochemical pathway and is either due to developmental or pollination-induced senescence. Many flowers from the order Liliales are characterized as ethylene-insensitive since they do not appear to produce endogenous ethylene, or respond to exogenous ethylene treatments, however, the majority of cases studied are wilting flowers, rather than those where life is terminated by perianth abscission. The role of ethylene in the senescence and abscission of Alstroemeria peruviana cv. Rebecca and cv. Samora tepals was previously unclear, with silver treatments recommended for delaying leaf rather than flower senescence. In the present paper the effects of exogenous ethylene, 2-chloroethylphosphonic acid (CEPA) and silver thiosulphate (STS) treatments on tepal senescence and abscission have been investigated. Results indicate that sensitivity to ethylene develops several days after flower opening such that STS only has a limited ability to delay tepal abscission. Detachment force measurements indicate that cell separation events are initiated after anthesis. Endogenous ethylene production was measured using laser photoacoustics and showed that Alstroemeria senesce independently of ethylene production, but that an extremely small amount of ethylene (0.15 nl flower(-1) h(-1)) is produced immediately prior to abscission. Investigation of the expression of genes involved in ethylene biosysnthesis by semi-quantitative RT-PCR indicated that transcriptional regulation is likely to be at the level of ACC oxidase, and that the timing of ACC oxidase gene expression is coincident with development of sensitivity to exogenous ethylene.

  11. Involvement of hydrogen peroxide in leaf abscission signaling, revealed by analysis with an in vitro abscission system in Capsicum plants.

    PubMed

    Sakamoto, Masaru; Munemura, Ikuko; Tomita, Reiko; Kobayashi, Kappei

    2008-10-01

    Although auxin and ethylene play pivotal roles in leaf abscission, the subsequent signaling molecules are poorly understood. This is mainly because it is difficult to effectively treat the intact abscission zone (AZ) with pharmacological reagents. We developed an in vitro experimental system that reproduces stress-induced leaf abscission in planta. In this system, 1-mm-thick petiole strips, encompassing the AZ, were separated within 4 days of abscission at the AZ through cell wall degradation in an auxin depletion- and ethylene-dependent manner. The system allowed us to show that hydrogen peroxide (H(2)O(2)) is involved in abscission signaling. Microscopic analyses revealed continuous H(2)O(2) production by AZ cells. H(2)O(2) scavengers and diphenylene iodonium, an inhibitor of NADPH oxidase, suppressed in vitro abscission and cellulase expression. Conversely, the application of H(2)O(2) promoted in vitro abscission and expression of cellulase. Ethephon-induced abscission was suppressed by inhibitors of H(2)O(2) production, whereas the expression of ethylene-responsive genes was unaffected by both H(2)O(2) and an H(2)O(2) inhibitor. These results indicated that H(2)O(2) acts downstream from ethylene in in vitro abscission signaling. In planta, salinity stress induced the expression of genes that respond to ethylene and reactive oxygen species, and also induced H(2)O(2) production at the AZ, which preceded leaf abscission. These results indicate that H(2)O(2) has roles in leaf abscission associated with ethylene both in vitro and in planta.

  12. Fruit abscission by Physalis species as defense against frugivory

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fruit abscission as a response to herbivory is well-documented in many plant species, but its effect on further damage by mobile herbivores that survive fruit abscission is relatively unstudied. Physalis plants abscise fruit containing feeding larvae of their main frugivore, Heliothis subflexa Guen...

  13. Development and regulation of pedicel abscission in tomato

    PubMed Central

    Ito, Yasuhiro; Nakano, Toshitsugu

    2015-01-01

    To shed unfertilized flowers or ripe fruits, many plant species develop a pedicel abscission zone (AZ), a specialized tissue that develops between the organ and the main body of the plant. Regulation of pedicel abscission is an important agricultural concern because pre-harvest abscission can reduce yields of fruit or grain crops, such as apples, rice, wheat, etc. Tomato has been studied as a model system for abscission, as tomato plants develop a distinct AZ at the midpoint of the pedicel and several tomato mutants, such as jointless, have pedicels that lack an AZ. This mini-review focuses on recent advances in research on the mechanisms regulating tomato pedicel abscission. Molecular genetic studies revealed that three MADS-box transcription factors interactively play a central role in pedicel AZ development. Transcriptome analyses identified activities involved in abscission and also found novel transcription factors that may regulate AZ activities. Another study identified transcription factors mediating abscission pathways from induction signals to activation of cell wall hydrolysis. These recent findings in tomato will enable significant advances in understanding the regulation of abscission in other key agronomic species. PMID:26124769

  14. Reduced ABA Accumulation in the Root System is Caused by ABA Exudation in Upland Rice (Oryza sativa L. var. Gaoshan1) and this Enhanced Drought Adaptation.

    PubMed

    Shi, Lu; Guo, Miaomiao; Ye, Nenghui; Liu, Yinggao; Liu, Rui; Xia, Yiji; Cui, Suxia; Zhang, Jianhua

    2015-05-01

    Lowland rice (Nipponbare) and upland rice (Gaoshan 1) that are comparable under normal and moderate drought conditions showed dramatic differences in severe drought conditions, both naturally occurring long-term drought and simulated rapid water deficits. We focused on their root response and found that enhanced tolerance of upland rice to severe drought conditions was mainly due to the lower level of ABA in its roots than in those of the lowland rice. We first excluded the effect of ABA biosynthesis and catabolism on root-accumulated ABA levels in both types of rice by monitoring the expression of four OsNCED genes and two OsABA8ox genes. Next, we excluded the impact of the aerial parts on roots by suppressing leaf-biosynthesized ABA with fluridone and NDGA (nordihydroguaiaretic acid), and measuring the ABA level in detached roots. Instead, we proved that upland rice had the ability to export considerably more root-sourced ABA than lowland rice under severe drought, which improved ABA-dependent drought adaptation. The investigation of apoplastic pH in root cells and root anatomy showed that ABA leakage in the root system of upland rice was related to high apoplastic pH and the absence of Casparian bands in the sclerenchyma layer. Finally, taking some genes as examples, we predicted that different ABA levels in rice roots stimulated distinct ABA perception and signaling cascades, which influenced its response to water stress.

  15. Inhibition of FUSCA3 degradation at high temperature is dependent on ABA signaling and is regulated by the ABA/GA ratio.

    PubMed

    Chiu, Rex Shun; Saleh, Yazan; Gazzarrini, Sonia

    2016-11-01

    During seed imbibition at supra-optimal temperature, an increase in the abscisic acid (ABA)/gibberellin (GA) ratio imposes secondary dormancy to prevent germination (thermoinhibition). FUSCA3 (FUS3), a positive regulator of seed dormancy, accumulates in seeds imbibed at high temperature and increases ABA levels to inhibit germination. Recently, we showed that ABA inhibits FUS3 degradation at high temperature, and that ABA and high temperature also inhibit the ubiquitin-proteasome system, by dampening both proteasome activity and protein polyubiquitination. Here, we investigated the role of ABA signaling components and the ABA antagonizing hormone, GA, in the regulation of FUS3 levels. We show that the ABA receptor mutant, pyl1-1, is less sensitive to ABA and thermoinhibition. In this mutant background, FUS3 degradation in vitro is faster. Similarly, GA alleviates thermoinhibition and also increases FUS3 degradation. These results indicate that inhibition of FUS3 degradation at high temperature is dependent on a high ABA/GA ratio and a functional ABA signaling pathway. Thus, FUS3 constitutes an important node in ABA-GA crosstalk during germination at supra-optimal temperature.

  16. A new aspect of flower abscission: involvement of a specific alkalization of the cytosol in the abscission zone cells

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The correlation between organ abscission and pH changes in the abscission zone (AZ) cells, visualized by the pH-sensitive and intracellularly trapped dye, 2',7'-bis-(2-carboxyethyl)-5(and-6)-carboxyfluorescein-acetoxymethyl (BCECF-AM) ester derivative, combined with confocal microscopy was studied. ...

  17. Microarray analysis of the abscission-related transcriptome in tomato flower abscission zone in response to auxin depletion

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Abscission, the separation of organs from the parent plant, results in postharvest quality loss in many fresh produce. The process is initiated by changes in the auxin gradient across the abscission zone (AZ), is triggered by ethylene and may be accelerated by postharvest stresses. Although changes ...

  18. Abscission of flowers and floral organs is closely associated with alkalization of the cytosol in abscission zone cells

    PubMed Central

    Sundaresan, Srivignesh; Philosoph-Hadas, Sonia; Riov, Joseph; Belausov, Eduard; Kochanek, Betina; Tucker, Mark L.; Meir, Shimon

    2015-01-01

    In vivo changes in the cytosolic pH of abscission zone (AZ) cells were visualized using confocal microscopic detection of the fluorescent pH-sensitive and intracellularly trapped dye, 2’,7’-bis-(2-carboxyethyl)-5(and-6)-carboxyfluorescein (BCECF), driven by its acetoxymethyl ester. A specific and gradual increase in the cytosolic pH of AZ cells was observed during natural abscission of flower organs in Arabidopsis thaliana and wild rocket (Diplotaxis tenuifolia), and during flower pedicel abscission induced by flower removal in tomato (Solanum lycopersicum Mill). The alkalization pattern in the first two species paralleled the acceleration or inhibition of flower organ abscission induced by ethylene or its inhibitor 1-methylcyclopropene (1-MCP), respectively. Similarly, 1-MCP pre-treatment of tomato inflorescence explants abolished the pH increase in AZ cells and pedicel abscission induced by flower removal. Examination of the pH changes in the AZ cells of Arabidopsis mutants defective in both ethylene-induced (ctr1, ein2, eto4) and ethylene-independent (ida, nev7, dab5) abscission pathways confirmed these results. The data indicate that the pH changes in the AZ cells are part of both the ethylene-sensitive and -insensitive abscission pathways, and occur concomitantly with the execution of organ abscission. pH can affect enzymatic activities and/or act as a signal for gene expression. Changes in pH during abscission could occur via regulation of transporters in AZ cells, which might affect cytosolic pH. Indeed, four genes associated with pH regulation, vacuolar H+-ATPase, putative high-affinity nitrate transporter, and two GTP-binding proteins, were specifically up-regulated in tomato flower AZ following abscission induction, and 1-MCP reduced or abolished the increased expression. PMID:25504336

  19. Abscission of flowers and floral organs is closely associated with alkalization of the cytosol in abscission zone cells.

    PubMed

    Sundaresan, Srivignesh; Philosoph-Hadas, Sonia; Riov, Joseph; Belausov, Eduard; Kochanek, Betina; Tucker, Mark L; Meir, Shimon

    2015-03-01

    In vivo changes in the cytosolic pH of abscission zone (AZ) cells were visualized using confocal microscopic detection of the fluorescent pH-sensitive and intracellularly trapped dye, 2',7'-bis-(2-carboxyethyl)-5(and-6)-carboxyfluorescein (BCECF), driven by its acetoxymethyl ester. A specific and gradual increase in the cytosolic pH of AZ cells was observed during natural abscission of flower organs in Arabidopsis thaliana and wild rocket (Diplotaxis tenuifolia), and during flower pedicel abscission induced by flower removal in tomato (Solanum lycopersicum Mill). The alkalization pattern in the first two species paralleled the acceleration or inhibition of flower organ abscission induced by ethylene or its inhibitor 1-methylcyclopropene (1-MCP), respectively. Similarly, 1-MCP pre-treatment of tomato inflorescence explants abolished the pH increase in AZ cells and pedicel abscission induced by flower removal. Examination of the pH changes in the AZ cells of Arabidopsis mutants defective in both ethylene-induced (ctr1, ein2, eto4) and ethylene-independent (ida, nev7, dab5) abscission pathways confirmed these results. The data indicate that the pH changes in the AZ cells are part of both the ethylene-sensitive and -insensitive abscission pathways, and occur concomitantly with the execution of organ abscission. pH can affect enzymatic activities and/or act as a signal for gene expression. Changes in pH during abscission could occur via regulation of transporters in AZ cells, which might affect cytosolic pH. Indeed, four genes associated with pH regulation, vacuolar H(+)-ATPase, putative high-affinity nitrate transporter, and two GTP-binding proteins, were specifically up-regulated in tomato flower AZ following abscission induction, and 1-MCP reduced or abolished the increased expression.

  20. The aba mutant of Arabidopsis thaliana is impaired in epoxy-carotenoid biosynthesis

    SciTech Connect

    Rock, C.D.; Zeevaart, J.A.D. )

    1991-09-01

    The three mutant alleles of the ABA locus of Arabidopsis thaliana result in plants that are deficient in the plant growth regulator abscisic acid (ABA). The authors have used {sup 18}O{sub 2} to label ABA in water-stressed leaves of mutant and wild-type Arabidopsis. Analysis by selected ion monitoring and tandem mass spectrometry of ({sup 18}O)ABA and its catabolites, phaseic acid and ABA-glucose ester ({beta}-D-glucopyranosyl abscisate), indicates that the aba genotypes are impaired in ABA biosynthesis and have a small ABA precursor pool of compounds that contain oxygens on the rings, presumably oxygenated carotenoids (xanthophylls). Quantitation of the carotenoids form mutant and wild-type leaves establishes that the aba alleles cause a deficiency of the epoxy-carotenoids violaxanthin and neoxanthin and an accumulation of their biosynthetic precursor, zeaxanthin. These results provide evidence that ABA is synthesized by oxidative cleavage of epoxy-carotenoids (the indirect pathway). Furthermore the carotenoid mutant they describe undergoes normal greening. Thus the aba alleles provide an opportunity to study the physiological roles of epoxy-carotenoids in photosynthesis in a higher plants.

  1. Nitric oxide and ABA in the control of plant function.

    PubMed

    Hancock, J T; Neill, S J; Wilson, I D

    2011-11-01

    Abscisic acid (ABA) and nitric oxide (NO) are both extremely important signalling molecules employed by plants to control many aspects of physiology. ABA has been extensively studied in the mechanisms which control stomatal movement as well as in seed dormancy and germination and plant development. The addition of either ABA or NO to plant cells is known to instigate the actions of many signal transduction components. Both may have an influence on the phosphorylation of proteins in cells mediated by effects on protein kinases and phosphatases, as well as recruiting a wide range of other signal transduction molecules to mediate the final effects. Both ABA and NO may also lead to the regulation of gene expression. However, it is becoming more apparent that NO may be acting downstream of ABA, with such action being mediated by reactive oxygen species such as hydrogen peroxide in some cases. However not all ABA responses require the action of NO. Here, examples of where ABA and NO have been put together into the same signal transduction pathways are discussed.

  2. PKCɛ switches Aurora B specificity to exit the abscission checkpoint

    PubMed Central

    Pike, Tanya; Brownlow, Nicola; Kjaer, Svend; Carlton, Jeremy; Parker, Peter J.

    2016-01-01

    The ‘NoCut', or Aurora B abscission checkpoint can be activated if DNA is retained in the cleavage furrow after completion of anaphase. Checkpoint failure leads to incomplete abscission and a binucleate outcome. These phenotypes are also observed after loss of PKCɛ in transformed cell models. Here we show that PKCɛ directly modulates the Aurora B-dependent abscission checkpoint by phosphorylating Aurora B at S227. This phosphorylation invokes a switch in Aurora B specificity, with increased phosphorylation of a subset of target substrates, including the CPC subunit Borealin. This switch is essential for abscission checkpoint exit. Preventing the phosphorylation of Borealin leads to abscission failure, as does expression of a non-phosphorylatable Aurora B S227A mutant. Further, depletion of the ESCRT-III component and Aurora B substrate CHMP4C enables abscission, bypassing the PKCɛ–Aurora B exit pathway. Thus, we demonstrate that PKCɛ signals through Aurora B to exit the abscission checkpoint and complete cell division. PMID:28004745

  3. PKCɛ switches Aurora B specificity to exit the abscission checkpoint.

    PubMed

    Pike, Tanya; Brownlow, Nicola; Kjaer, Svend; Carlton, Jeremy; Parker, Peter J

    2016-12-22

    The 'NoCut', or Aurora B abscission checkpoint can be activated if DNA is retained in the cleavage furrow after completion of anaphase. Checkpoint failure leads to incomplete abscission and a binucleate outcome. These phenotypes are also observed after loss of PKCɛ in transformed cell models. Here we show that PKCɛ directly modulates the Aurora B-dependent abscission checkpoint by phosphorylating Aurora B at S227. This phosphorylation invokes a switch in Aurora B specificity, with increased phosphorylation of a subset of target substrates, including the CPC subunit Borealin. This switch is essential for abscission checkpoint exit. Preventing the phosphorylation of Borealin leads to abscission failure, as does expression of a non-phosphorylatable Aurora B S227A mutant. Further, depletion of the ESCRT-III component and Aurora B substrate CHMP4C enables abscission, bypassing the PKCɛ-Aurora B exit pathway. Thus, we demonstrate that PKCɛ signals through Aurora B to exit the abscission checkpoint and complete cell division.

  4. Reduced Accumulation of ABA during Water Stress in a Molybdenum Cofactor Mutant of Barley 1

    PubMed Central

    Walker-Simmons, Mary; Kudrna, David A.; Warner, Robert L.

    1989-01-01

    A barley (Hordeum vulgare L.) mutant (Az34) has been identified with low basal levels of abscisic acid (ABA) and with reduced capacity for producing ABA in response to water stress. The mutation is in a gene controlling the molybdenum cofactor resulting in a pleiotropic deficiency in at least three molybdoenzymes, nitrate reductase, xanthine dehydrogenase, and aldehyde oxidase. The mutant was found to lack aldehyde oxidase activity with several substrates including: (a) ABA aldehyde, a putative precursor of ABA; (b) an acetylenic analog of ABA aldehyde; and (c) heptaldehyde. Elevating the growth temperature from 18 to 26°C caused mutant leaves to wilt and brown. Desiccation of mutant leaves was prevented by applying ABA. These results indicate that ABA biosynthesis at some developmental stages is dependent upon a molybdoenzyme which may be an aldehyde oxidase. Images Figure 5 PMID:16666835

  5. Transcriptome Profiling of Petal Abscission Zone and Functional Analysis of an Aux/IAA Family Gene RhIAA16 Involved in Petal Shedding in Rose

    PubMed Central

    Gao, Yuerong; Liu, Chun; Li, Xiaodong; Xu, Haiqian; Liang, Yue; Ma, Nan; Fei, Zhangjun; Gao, Junping; Jiang, Cai-Zhong; Ma, Chao

    2016-01-01

    Roses are one of the most important cut flowers among ornamental plants. Rose flower longevity is largely dependent on the timing of petal shedding occurrence. To understand the molecular mechanism underlying petal abscission in rose, we performed transcriptome profiling of the petal abscission zone during petal shedding using Illumina technology. We identified a total of 2592 differentially transcribed genes (DTGs) during rose petal shedding. Gene ontology term enrichment and pathway analysis revealed that major biochemical pathways the DTGs were involved in included ethylene biosynthesis, starch degradation, superpathway of cytosolic glycolysis, pyruvate dehydrogenase and TCA cycle, photorespiration and the lactose degradation III pathway. This suggests that alterations in carbon metabolism are an important part of rose petal abscission. Among these DTGs, approximately 150 genes putatively encoding transcription factors were identified in rose abscission zone. These included zinc finger, WRKY, ERF, and Aux/IAA gene families, suggesting that petal abscission involves complex transcriptional reprogramming. Approximately 108 DTGs were related to hormone pathways, of which auxin and ethylene related DTGs were the largest groups including 52 and 41 genes, respectively. These also included 12 DTGs related to gibberellin and 6 DTGs in jasmonic acid pathway. Surprisingly, no DTGs involved in the biosynthesis/signaling of abscisic acid, cytokinin, brassinosteroid, and salicylic acid pathways were detected. Moreover, among DTGs related to auxin, we identified an Aux/IAA gene RhIAA16 that was up-regulated in response to petal shedding. Down-regulation of RhIAA16 by virus-induced gene silencing in rose promoted petal abscission, suggesting that RhIAA16 plays an important role in rose petal abscission. PMID:27695465

  6. Transcriptome Profiling of Petal Abscission Zone and Functional Analysis of an Aux/IAA Family Gene RhIAA16 Involved in Petal Shedding in Rose.

    PubMed

    Gao, Yuerong; Liu, Chun; Li, Xiaodong; Xu, Haiqian; Liang, Yue; Ma, Nan; Fei, Zhangjun; Gao, Junping; Jiang, Cai-Zhong; Ma, Chao

    2016-01-01

    Roses are one of the most important cut flowers among ornamental plants. Rose flower longevity is largely dependent on the timing of petal shedding occurrence. To understand the molecular mechanism underlying petal abscission in rose, we performed transcriptome profiling of the petal abscission zone during petal shedding using Illumina technology. We identified a total of 2592 differentially transcribed genes (DTGs) during rose petal shedding. Gene ontology term enrichment and pathway analysis revealed that major biochemical pathways the DTGs were involved in included ethylene biosynthesis, starch degradation, superpathway of cytosolic glycolysis, pyruvate dehydrogenase and TCA cycle, photorespiration and the lactose degradation III pathway. This suggests that alterations in carbon metabolism are an important part of rose petal abscission. Among these DTGs, approximately 150 genes putatively encoding transcription factors were identified in rose abscission zone. These included zinc finger, WRKY, ERF, and Aux/IAA gene families, suggesting that petal abscission involves complex transcriptional reprogramming. Approximately 108 DTGs were related to hormone pathways, of which auxin and ethylene related DTGs were the largest groups including 52 and 41 genes, respectively. These also included 12 DTGs related to gibberellin and 6 DTGs in jasmonic acid pathway. Surprisingly, no DTGs involved in the biosynthesis/signaling of abscisic acid, cytokinin, brassinosteroid, and salicylic acid pathways were detected. Moreover, among DTGs related to auxin, we identified an Aux/IAA gene RhIAA16 that was up-regulated in response to petal shedding. Down-regulation of RhIAA16 by virus-induced gene silencing in rose promoted petal abscission, suggesting that RhIAA16 plays an important role in rose petal abscission.

  7. Protein kinase C epsilon in cell division: control of abscission.

    PubMed

    Saurin, Adrian T; Brownlow, Nicola; Parker, Peter J

    2009-02-15

    Cell division requires the separation and partitioning of sister chromatids to opposite ends of the cell before an actomyosin ring contracts the membrane in between during cytokinesis. The final irreversible step occurs during abscission when the ring breaks down and the membrane is sealed in its place. The physical mechanics of contraction depend on RhoA, which is stimulated by a centralspindlin complex around the cell equator. However exactly how these events are reversed to allow actomyosin breakdown and abscission were not well understood. Here we will discuss new findings that implicate Protein Kinase C epsilon (PKCepsilon) as a regulator of RhoA signalling required for abscission.

  8. Improved cold tolerance in Elymus nutans by exogenous application of melatonin may involve ABA-dependent and ABA-independent pathways

    PubMed Central

    Fu, Juanjuan; Wu, Ye; Miao, Yanjun; Xu, Yamei; Zhao, Enhua; Wang, Jin; Sun, Huaien; Liu, Qian; Xue, Yongwei; Xu, Yuefei; Hu, Tianming

    2017-01-01

    Melatonin is an important secondary messenger that plays a central role in plant growth, as well as abiotic and biotic stress tolerance. However, the underlying physiological and molecular mechanisms of melatonin-mediated cold tolerance, especially interactions between melatonin and other key molecules in the plant stress response, remain unknown. Here, the interrelation between melatonin and abscisic acid (ABA) was investigated in two genotypes of Elymus nutans Griseb., the cold-tolerant Damxung (DX) and the cold-sensitive Gannan (GN) under cold stress. Pre-treatment with exogenous melatonin or ABA alleviated oxidative injury via scavenging ROS, while enhancing both antioxidant enzyme activities and non-enzymatic antioxidant contents. Treatment of fluridone, an ABA biosynthesis inhibitor caused membrane lipid peroxidation and lowered melatonin-induced antioxidant defense responses. It is worth noting that cold stress significantly induced both endogenous melatonin and ABA levels in both genotypes. Application of melatonin increased ABA production, while fluridone significantly suppressed melatonin-induced ABA accumulation. ABA and fluridone pre-treatments failed to affect the endogenous melatonin concentration. Moreover, exogenous melatonin up-regulated the expression of cold-responsive genes in an ABA-independent manner. These results indicate that both ABA-dependent and ABA-independent pathways may contribute to melatonin-induced cold tolerance in E. nutans. PMID:28045095

  9. ABA receptor PYL9 promotes drought resistance and leaf senescence.

    PubMed

    Zhao, Yang; Chan, Zhulong; Gao, Jinghui; Xing, Lu; Cao, Minjie; Yu, Chunmei; Hu, Yuanlei; You, Jun; Shi, Haitao; Zhu, Yingfang; Gong, Yuehua; Mu, Zixin; Wang, Haiqing; Deng, Xin; Wang, Pengcheng; Bressan, Ray A; Zhu, Jian-Kang

    2016-02-16

    Drought stress is an important environmental factor limiting plant productivity. In this study, we screened drought-resistant transgenic plants from 65 promoter-pyrabactin resistance 1-like (PYL) abscisic acid (ABA) receptor gene combinations and discovered that pRD29A::PYL9 transgenic lines showed dramatically increased drought resistance and drought-induced leaf senescence in both Arabidopsis and rice. Previous studies suggested that ABA promotes senescence by causing ethylene production. However, we found that ABA promotes leaf senescence in an ethylene-independent manner by activating sucrose nonfermenting 1-related protein kinase 2s (SnRK2s), which subsequently phosphorylate ABA-responsive element-binding factors (ABFs) and Related to ABA-Insensitive 3/VP1 (RAV1) transcription factors. The phosphorylated ABFs and RAV1 up-regulate the expression of senescence-associated genes, partly by up-regulating the expression of Oresara 1. The pyl9 and ABA-insensitive 1-1 single mutants, pyl8-1pyl9 double mutant, and snrk2.2/3/6 triple mutant showed reduced ABA-induced leaf senescence relative to the WT, whereas pRD29A::PYL9 transgenic plants showed enhanced ABA-induced leaf senescence. We found that leaf senescence may benefit drought resistance by helping to generate an osmotic potential gradient, which is increased in pRD29A::PYL9 transgenic plants and causes water to preferentially flow to developing tissues. Our results uncover the molecular mechanism of ABA-induced leaf senescence and suggest an important role of PYL9 and leaf senescence in promoting resistance to extreme drought stress.

  10. Characterization of the ABA signal transduction pathway in Vitis vinifera.

    PubMed

    Boneh, Uri; Biton, Iris; Schwartz, Amnon; Ben-Ari, Giora

    2012-05-01

    The plant hormone abscisic acid (ABA) regulates many key processes in plants including the response to abiotic stress. ABA signal transduction consists of a double-negative regulatory mechanism, whereby ABA-bound PYR/RCARs inhibit PP2C activity, and PP2Cs inactivate SnRK2s. We studied and analyzed the various genes participating in the ABA signaling cascade of the grape (Vitis vinifera). The grape ABA signal transduction consists of at least six SnRK2s. Yeast two-hybrid system was used to test direct interactions between core components of grape ABA signal transduction. We found that a total of forty eight interactions can occur between the various components. Exogenous abscisic acid (ABA) and abiotic stresses such as drought, high salt concentration and cold, were applied to vines growing in a hydroponic system. These stresses regulated the expression of various grape SnRK2s as well as ABFs in leaves and roots. Based on the interactions between SnRK2s and its targets and the expression pattern, we suggest that VvSnRK2.1 and VvSnRK2.6, can be considered the major VvSnRK2 candidates involved in the stomata response to abiotic stress. Furthermore, we found that the expression pattern of the two grape ABF genes indicates organ specificity of these genes. The key role of ABA signaling in response to abiotic stresses makes the genes involve in this signaling potential candidates for manipulation in programs designed to improve fruit tree performance in extreme environments.

  11. Abscission checkpoint control: stuck in the middle with Aurora B.

    PubMed

    Carmena, Mar

    2012-07-01

    At the end of cell division, the cytoplasmic bridge joining the daughter cells is severed through a process that involves scission of the plasma membrane. The presence of chromatin bridges 'stuck' in the division plane is sensed by the chromosomal passenger complex (CPC) component Aurora B kinase, triggering a checkpoint that delays abscission until the chromatin bridges have been resolved. Recent work has started to shed some light on the molecular mechanism by which the CPC controls the timing of abscission.

  12. Carbohydrate Stress Affecting Fruitlet Abscission and Expression of Genes Related to Auxin Signal Transduction Pathway in Litchi

    PubMed Central

    Kuang, Jian-Fei; Wu, Jian-Yang; Zhong, Hai-Ying; Li, Cai-Qin; Chen, Jian-Ye; Lu, Wang-Jin; Li, Jian-Guo

    2012-01-01

    Auxin, a vital plant hormone, regulates a variety of physiological and developmental processes. It is involved in fruit abscission through transcriptional regulation of many auxin-related genes, including early auxin responsive genes (i.e., auxin/indole-3-acetic acid (AUX/IAA), Gretchen Hagen3 (GH3) and small auxin upregulated (SAUR)) and auxin response factors (ARF), which have been well characterized in many plants. In this study, totally five auxin-related genes, including one AUX/IAA (LcAUX/IAA1), one GH3 (LcGH3.1), one SAUR (LcSAUR1) and two ARFs (LcARF1 and LcARF2), were isolated and characterized from litchi fruit. LcAUX/IAA1, LcGH3.1, LcSAUR1, LcARF1 and LcARF2 contain open reading frames (ORFs) encoding polypeptides of 203, 613, 142, 792 and 832 amino acids, respectively, with their corresponding molecular weights of 22.67, 69.20, 11.40, 88.20 and 93.16 kDa. Expression of these genes was investigated under the treatment of girdling plus defoliation which aggravated litchi fruitlet abscission due to the blockage of carbohydrates transport and the reduction of endogenous IAA content. Results showed that transcript levels of LcAUX/IAA1, LcGH3.1 and LcSAUR1 mRNAs were increased after the treatment in abscission zone (AZ) and other tissues, in contrast to the decreasing accumulation of LcARF1 mRNA, suggesting that LcAUX/IAA1, LcSAUR1 and LcARF1 may play more important roles in abscission. Our results provide new insight into the process of fruitlet abscission induced by carbohydrate stress and broaden our understanding of the auxin signal transduction pathway in this process at the molecular level. PMID:23443112

  13. Inactivation of PYR/PYL/RCAR ABA receptors by tyrosine nitration may enable rapid inhibition of ABA signaling by nitric oxide in plants.

    PubMed

    Castillo, Mari-Cruz; Lozano-Juste, Jorge; González-Guzmán, Miguel; Rodriguez, Lesia; Rodriguez, Pedro L; León, José

    2015-09-01

    Abscisic acid (ABA) is a phytohormone that inhibits growth and enhances adaptation to stress in plants. ABA perception and signaling rely on its binding to receptors of the pyrabactin resistance1/PYR1-like/regulatory components of ABA receptors (PYR/PYL/RCAR) family, the subsequent inhibition of clade A type 2C protein phosphatases (PP2Cs), and the phosphorylation of ion channels and transcription factors by protein kinases of the SnRK2 family. Nitric oxide (NO) may inhibit ABA signaling because NO-deficient plants are hypersensitive to ABA. Regulation by NO often involves posttranslational modification of proteins. Mass spectrometry analysis of ABA receptors expressed in plants and recombinant receptors modified in vitro revealed that the receptors were nitrated at tyrosine residues and S-nitrosylated at cysteine residues. In an in vitro ABA-induced, PP2C inhibition assay, tyrosine nitration reduced receptor activity, whereas S-nitrosylated receptors were fully capable of ABA-induced inhibition of the phosphatase. PYR/PYL/RCAR proteins with nitrated tyrosine, which is an irreversible covalent modification, were polyubiquitylated and underwent proteasome-mediated degradation. We propose that tyrosine nitration, which requires NO and superoxide anions, is a rapid mechanism by which NO limits ABA signaling under conditions in which NO and reactive oxygen species are both produced.

  14. ABA inhibits entry into stomatal-lineage development in Arabidopsis leaves.

    PubMed

    Tanaka, Yoko; Nose, Tomoe; Jikumaru, Yusuke; Kamiya, Yuji

    2013-05-01

    The number and density of stomata are controlled by endogenous and environmental factors. Despite recent advances in our understanding of stomatal development, mechanisms which prevent stomatal-lineage entry remain unclear. Here, we propose that abscisic acid (ABA), a phytohormone known to induce stomatal closure, limits initiation of stomatal development and induces enlargement of pavement cells in Arabidopsis cotyledons. An ABA-deficient aba2-2 mutant had an increased number/proportion of stomata within a smaller cotyledon, as well as reduced expansion of pavement cells. This tendency was reversed after ABA application or in an ABA over-accumulating cyp707a1cyp707a3 doublemutant. Our time course analysis revealed that aba2-2 shows prolonged formation of meristemoids and guard mother cells, both precursors of stoma. This finding is in accordance with prolonged gene expression of SPCH and MUTE, master regulators for stomatal formation, indicating that ABA acts upstream of these genes. Only aba2-2 mute, but not aba2-2 spch double mutant showed additive phenotypes and displayed inhibition of pavement cell enlargement with increased meristemoid number, indicating that ABA action on pavement cell expansion requires the presence of stomatal-lineage cells.

  15. The ABA signal transduction mechanism in commercial crops: learning from Arabidopsis.

    PubMed

    Ben-Ari, Giora

    2012-08-01

    The phytohormone abscisic acid (ABA) affects a wide range of stages of plant development as well as the plant's response to biotic and abiotic stresses. Manipulation of ABA signaling in commercial crops holds promising potential for improving crop yields. Several decades of research have been invested in attempts to identify the first components of the ABA signaling cascade. It was only in 2009, that two independent groups identified the PYR/PYL/RCAR protein family as the plant ABA receptor. This finding was followed by a surge of studies on ABA signal transduction, many of them using Arabidopsis as their model. The ABA signaling cascade was found to consist of a double-negative regulatory mechanism assembled from three protein families. These include the ABA receptors, the PP2C family of inhibitors, and the kinase family, SnRK2. It was found that ABA-bound PYR/RCARs inhibit PP2C activity, and that PP2Cs inactivate SnRK2s. Researchers today are examining how the elucidation of the ABA signaling cascade in Arabidopsis can be applied to improvements in commercial agriculture. In this article, we have attempted to review recent studies which address this issue. In it, we discuss various approaches useful in identifying the genetic and protein components involved. Finally, we suggest possible commercial applications of genetic manipulation of ABA signaling to improve crop yields.

  16. Comprehensive Analysis of ABA Effects on Ethylene Biosynthesis and Signaling during Tomato Fruit Ripening

    PubMed Central

    Bu, Jianwen; Jiang, Yuanyuan; Khan, Zia Ullah; Luo, Zisheng; Mao, Linchun; Ying, Tiejin

    2016-01-01

    ABA has been widely acknowledged to regulate ethylene biosynthesis and signaling during fruit ripening, but the molecular mechanism underlying the interaction between these two hormones are largely unexplored. In the present study, exogenous ABA treatment obviously promoted fruit ripening as well as ethylene emission, whereas NDGA (Nordihydroguaiaretic acid, an inhibitor of ABA biosynthesis) application showed the opposite biological effects. Combined RNA-seq with time-course RT-PCR analysis, our study not only helped to illustrate how ABA regulated itself at the transcription level, but also revealed that ABA can facilitate ethylene production and response probably by regulating some crucial genes such as LeACS4, LeACO1, GR and LeETR6. In addition, investigation on the fruits treated with 1-MCP immediately after ABA exposure revealed that ethylene might be essential for the induction of ABA biosynthesis and signaling at the onset of fruit ripening. Furthermore, some specific transcription factors (TFs) known as regulators of ethylene synthesis and sensibility (e.g. MADS-RIN, TAGL1, CNR and NOR) were also observed to be ABA responsive, which implied that ABA influenced ethylene action possibly through the regulation of these TFs expression. Our comprehensive physiological and molecular-level analysis shed light on the mechanism of cross-talk between ABA and ethylene during the process of tomato fruit ripening. PMID:27100326

  17. Comprehensive Analysis of ABA Effects on Ethylene Biosynthesis and Signaling during Tomato Fruit Ripening.

    PubMed

    Mou, Wangshu; Li, Dongdong; Bu, Jianwen; Jiang, Yuanyuan; Khan, Zia Ullah; Luo, Zisheng; Mao, Linchun; Ying, Tiejin

    2016-01-01

    ABA has been widely acknowledged to regulate ethylene biosynthesis and signaling during fruit ripening, but the molecular mechanism underlying the interaction between these two hormones are largely unexplored. In the present study, exogenous ABA treatment obviously promoted fruit ripening as well as ethylene emission, whereas NDGA (Nordihydroguaiaretic acid, an inhibitor of ABA biosynthesis) application showed the opposite biological effects. Combined RNA-seq with time-course RT-PCR analysis, our study not only helped to illustrate how ABA regulated itself at the transcription level, but also revealed that ABA can facilitate ethylene production and response probably by regulating some crucial genes such as LeACS4, LeACO1, GR and LeETR6. In addition, investigation on the fruits treated with 1-MCP immediately after ABA exposure revealed that ethylene might be essential for the induction of ABA biosynthesis and signaling at the onset of fruit ripening. Furthermore, some specific transcription factors (TFs) known as regulators of ethylene synthesis and sensibility (e.g. MADS-RIN, TAGL1, CNR and NOR) were also observed to be ABA responsive, which implied that ABA influenced ethylene action possibly through the regulation of these TFs expression. Our comprehensive physiological and molecular-level analysis shed light on the mechanism of cross-talk between ABA and ethylene during the process of tomato fruit ripening.

  18. ESCRT-I Component VPS23A Affects ABA Signaling by Recognizing ABA Receptors for Endosomal Degradation.

    PubMed

    Yu, Feifei; Lou, Lijuan; Tian, Miaomiao; Li, Qingliang; Ding, Yanglin; Cao, Xiaoqiang; Wu, Yaorong; Belda-Palazon, Borja; Rodriguez, Pedro L; Yang, Shuhua; Xie, Qi

    2016-12-05

    Recent discovery of PYR/PYL/RCAR-type abscisic acid (ABA) receptors has become one of most significant advances in plant science in the past decade. In mammals, endosomal sorting acts as an important pathway to downregulate different types of receptors, but its role in plant hormone signaling is poorly understood. Here, we report that an ubiquitin E2-like protein, VPS23A, which is a key component of ESCRT-I, negatively regulates ABA signaling. VPS23A has epistatic relationship with PYR/PYL/RCAR-type ABA receptors and disruption of VPS23A enhanced the activity of key kinase OST1 in the ABA signaling pathway under ABA treatment. Moreover, VPS23A interacts with PYR1/PYLs and K63-linked diubiquitin, and PYL4 possesses K63-linked ubiquitinated modification in vivo. Further analysis revealed that VPS23A affects the subcellular localization of PYR1 and the stability of PYL4. Taken together, our results suggest that VPS23A affects PYR1/PYL4 via vacuole-mediated degradation, providing an advanced understanding of both the turnover of ABA receptors and ESCRTs in plant hormone signaling.

  19. ABA crosstalk with ethylene and nitric oxide in seed dormancy and germination

    PubMed Central

    Arc, Erwann; Sechet, Julien; Corbineau, Françoise; Rajjou, Loïc; Marion-Poll, Annie

    2013-01-01

    Dormancy is an adaptive trait that enables seed germination to coincide with favorable environmental conditions. It has been clearly demonstrated that dormancy is induced by abscisic acid (ABA) during seed development on the mother plant. After seed dispersal, germination is preceded by a decline in ABA in imbibed seeds, which results from ABA catabolism through 8′-hydroxylation. The hormonal balance between ABA and gibberellins (GAs) has been shown to act as an integrator of environmental cues to maintain dormancy or activate germination. The interplay of ABA with other endogenous signals is however less documented. In numerous species, ethylene counteracts ABA signaling pathways and induces germination. In Brassicaceae seeds, ethylene prevents the inhibitory effects of ABA on endosperm cap weakening, thereby facilitating endosperm rupture and radicle emergence. Moreover, enhanced seed dormancy in Arabidopsis ethylene-insensitive mutants results from greater ABA sensitivity. Conversely, ABA limits ethylene action by down-regulating its biosynthesis. Nitric oxide (NO) has been proposed as a common actor in the ABA and ethylene crosstalk in seed. Indeed, convergent evidence indicates that NO is produced rapidly after seed imbibition and promotes germination by inducing the expression of the ABA 8′-hydroxylase gene, CYP707A2, and stimulating ethylene production. The role of NO and other nitrogen-containing compounds, such as nitrate, in seed dormancy breakage and germination stimulation has been reported in several species. This review will describe our current knowledge of ABA crosstalk with ethylene and NO, both volatile compounds that have been shown to counteract ABA action in seeds and to improve dormancy release and germination. PMID:23531630

  20. ABA crosstalk with ethylene and nitric oxide in seed dormancy and germination.

    PubMed

    Arc, Erwann; Sechet, Julien; Corbineau, Françoise; Rajjou, Loïc; Marion-Poll, Annie

    2013-01-01

    Dormancy is an adaptive trait that enables seed germination to coincide with favorable environmental conditions. It has been clearly demonstrated that dormancy is induced by abscisic acid (ABA) during seed development on the mother plant. After seed dispersal, germination is preceded by a decline in ABA in imbibed seeds, which results from ABA catabolism through 8'-hydroxylation. The hormonal balance between ABA and gibberellins (GAs) has been shown to act as an integrator of environmental cues to maintain dormancy or activate germination. The interplay of ABA with other endogenous signals is however less documented. In numerous species, ethylene counteracts ABA signaling pathways and induces germination. In Brassicaceae seeds, ethylene prevents the inhibitory effects of ABA on endosperm cap weakening, thereby facilitating endosperm rupture and radicle emergence. Moreover, enhanced seed dormancy in Arabidopsis ethylene-insensitive mutants results from greater ABA sensitivity. Conversely, ABA limits ethylene action by down-regulating its biosynthesis. Nitric oxide (NO) has been proposed as a common actor in the ABA and ethylene crosstalk in seed. Indeed, convergent evidence indicates that NO is produced rapidly after seed imbibition and promotes germination by inducing the expression of the ABA 8'-hydroxylase gene, CYP707A2, and stimulating ethylene production. The role of NO and other nitrogen-containing compounds, such as nitrate, in seed dormancy breakage and germination stimulation has been reported in several species. This review will describe our current knowledge of ABA crosstalk with ethylene and NO, both volatile compounds that have been shown to counteract ABA action in seeds and to improve dormancy release and germination.

  1. Resolving new ultrastructural features of cytokinetic abscission with soft-X-ray cryo-tomography

    PubMed Central

    Sherman, Shachar; Kirchenbuechler, David; Nachmias, Dikla; Tamir, Adi; Werner, Stephan; Elbaum, Michael; Elia, Natalie

    2016-01-01

    Mammalian cytokinetic abscission is mediated by the ESCRT membrane fission machinery. While much has been clarified on the topology and kinetics of abscission through high-resolution microscopy, key questions regarding the mechanism of abscission remain open. Here we apply cryogenic soft-X-ray tomography to elucidate new ultrastructural details in the intercellular membrane bridge connecting cells undergoing abscission. In particular, we resolve defined ring-like structures inside the midbody dark zone that have been inaccessible to EM, and identify membrane extrusions at the abscission sites. In cells at late stages of abscission we resolve a complex array of helical spirals, extending the structural information obtained by EM. Our results highlight the advantages of soft-X-ray tomography and emphasize the importance of using complementary approaches for characterizing cellular structures. Notably, by providing new structural data from intact cells we present a realistic view on the topology of abscission and suggest new mechanistic models for ESCRT mediated abscission. PMID:27282220

  2. Molecular Mimicry Regulates ABA Signaling by SnRK2 Kinases and PP2C Phosphatases

    SciTech Connect

    Soon, Fen-Fen; Ng, Ley-Moy; Zhou, X. Edward; West, Graham M.; Kovach, Amanda; Tan, M.H. Eileen; Suino-Powell, Kelly M.; He, Yuanzheng; Xu, Yong; Chalmers, Michael J.; Brunzelle, Joseph S.; Zhang, Huiming; Yang, Huaiyu; Jiang, Hualiang; Li, Jun; Yong, Eu-Leong; Cutler, Sean; Zhu, Jian-Kang; Griffin, Patrick R.; Melcher, Karsten; Xu, H. Eric

    2014-10-02

    Abscisic acid (ABA) is an essential hormone for plants to survive environmental stresses. At the center of the ABA signaling network is a subfamily of type 2C protein phosphatases (PP2Cs), which form exclusive interactions with ABA receptors and subfamily 2 Snfl-related kinase (SnRK2s). Here, we report a SnRK2-PP2C complex structure, which reveals marked similarity in PP2C recognition by SnRK2 and ABA receptors. In the complex, the kinase activation loop docks into the active site of PP2C, while the conserved ABA-sensing tryptophan of PP2C inserts into the kinase catalytic cleft, thus mimicking receptor-PP2C interactions. These structural results provide a simple mechanism that directly couples ABA binding to SnRK2 kinase activation and highlight a new paradigm of kinase-phosphatase regulation through mutual packing of their catalytic sites.

  3. Molecular Mimicry Regulates ABA Signaling by SnRK2 Kinases and PP2C Phosphatases

    PubMed Central

    Soon, Fen-Fen; Ng, Ley-Moy; Zhou, X. Edward; West, Graham M.; Kovach, Amanda; Tan, M. H. Eileen; Suino-Powell, Kelly M.; He, Yuanzheng; Xu, Yong; Chalmers, Michael J.; Brunzelle, Joseph S.; Zhang, Huiming; Yang, Huaiyu; Jiang, Hualiang; Li, Jun; Yong, Eu-Leong; Cutler, Sean; Zhu, Jian-Kang; Griffin, Patrick R.; Melcher, Karsten; Xu, H. Eric

    2013-01-01

    Abscisic acid (ABA) is an essential hormone for plants to survive environmental stresses. At the center of the ABA signaling network is a subfamily of type 2C protein phosphatases (PP2Cs), which form exclusive interactions with ABA receptors and subfamily 2 Snfl-related kinase (SnRK2s). Here, we report a SnRK2-PP2C complex structure, which reveals marked similarity in PP2C recognition by SnRK2 and ABA receptors. In the complex, the kinase activation loop docks into the active site of PP2C, while the conserved ABA-sensing tryptophan of PP2C inserts into the kinase catalytic cleft, thus mimicking receptor-PP2C interactions. These structural results provide a simple mechanism that directly couples ABA binding to SnRK2 kinase activation and highlight a new paradigm of kinase-phosphatase regulation through mutual packing of their catalytic sites. PMID:22116026

  4. Molecular mimicry regulates ABA signaling by SnRK2 kinases and PP2C phosphatases.

    PubMed

    Soon, Fen-Fen; Ng, Ley-Moy; Zhou, X Edward; West, Graham M; Kovach, Amanda; Tan, M H Eileen; Suino-Powell, Kelly M; He, Yuanzheng; Xu, Yong; Chalmers, Michael J; Brunzelle, Joseph S; Zhang, Huiming; Yang, Huaiyu; Jiang, Hualiang; Li, Jun; Yong, Eu-Leong; Cutler, Sean; Zhu, Jian-Kang; Griffin, Patrick R; Melcher, Karsten; Xu, H Eric

    2012-01-06

    Abscisic acid (ABA) is an essential hormone for plants to survive environmental stresses. At the center of the ABA signaling network is a subfamily of type 2C protein phosphatases (PP2Cs), which form exclusive interactions with ABA receptors and subfamily 2 Snfl-related kinase (SnRK2s). Here, we report a SnRK2-PP2C complex structure, which reveals marked similarity in PP2C recognition by SnRK2 and ABA receptors. In the complex, the kinase activation loop docks into the active site of PP2C, while the conserved ABA-sensing tryptophan of PP2C inserts into the kinase catalytic cleft, thus mimicking receptor-PP2C interactions. These structural results provide a simple mechanism that directly couples ABA binding to SnRK2 kinase activation and highlight a new paradigm of kinase-phosphatase regulation through mutual packing of their catalytic sites.

  5. Core Mechanisms Regulating Developmentally Timed and Environmentally Triggered Abscission[OPEN

    PubMed Central

    2016-01-01

    Drought-triggered abscission is a strategy used by plants to avoid the full consequences of drought; however, it is poorly understood at the molecular genetic level. Here, we show that Arabidopsis (Arabidopsis thaliana) can be used to elucidate the pathway controlling drought-triggered leaf shedding. We further show that much of the pathway regulating developmentally timed floral organ abscission is conserved in regulating drought-triggered leaf abscission. Gene expression of HAESA (HAE) and INFLORESCENCE DEFICIENT IN ABSCISSION (IDA) is induced in cauline leaf abscission zones when the leaves become wilted in response to limited water and HAE continues to accumulate in the leaf abscission zones through the abscission process. The genes that encode HAE/HAESA-LIKE2, IDA, NEVERSHED, and MAPK KINASE4 and 5 are all necessary for drought-induced leaf abscission. Our findings offer a molecular mechanism explaining drought-triggered leaf abscission. Furthermore, the ability to study leaf abscission in Arabidopsis opens up a new avenue to tease apart mechanisms involved in abscission that have been difficult to separate from flower development as well as for understanding the mechanistic role of water and turgor pressure in abscission. PMID:27468996

  6. Transcriptome analysis of soybean leaf abscission identifies transcriptional regulators of organ polarity and cell fate

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Abscission, organ detachment, is a developmental process that is modulated by environmental factors. To understand the molecular events underlying the progression of abscission in soybean, we induced abscission in 21 day-old soybean by treating leaf explants with ethylene. RNA-seq was completed for ...

  7. Overexpression of an ABA biosynthesis gene using a stress inducible promoter enhances drought resistance in petunia

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Plants respond to drought stress by closing their stomata and reducing transpirational water loss. The plant hormone abscisic acid (ABA) regulates growth and stomatal closure particularly when the plant is under environmental stresses. One of the key enzymes in the ABA biosynthesis of higher plants ...

  8. Deer predation on leaf miners via leaf abscission

    NASA Astrophysics Data System (ADS)

    Yamazaki, Kazuo; Sugiura, Shinji

    2008-03-01

    The evergreen oak Quercus gilva Blume sheds leaves containing mines of the leaf miner Stigmella sp. (Lepidoptera: Nepticulidae) earlier than leaves with no mines in early spring in Nara, central Japan. The eclosion rates of the leaf miner in abscised and retained leaves were compared in the laboratory to clarify the effects of leaf abscission on leaf miner survival in the absence of deer. The leaf miner eclosed successfully from both fallen leaves and leaves retained on trees. However, sika deer ( Cervus nippon centralis Kishida) feed on the fallen mined leaves. Field observations showed that deer consume many fallen leaves under Q. gilva trees, suggesting considerable mortality of leaf miners due to deer predation via leaf abscission. This is a previously unreported relationship between a leaf miner and a mammalian herbivore via leaf abscission.

  9. Deer predation on leaf miners via leaf abscission.

    PubMed

    Yamazaki, Kazuo; Sugiura, Shinji

    2008-03-01

    The evergreen oak Quercus gilva Blume sheds leaves containing mines of the leaf miner Stigmella sp. (Lepidoptera: Nepticulidae) earlier than leaves with no mines in early spring in Nara, central Japan. The eclosion rates of the leaf miner in abscised and retained leaves were compared in the laboratory to clarify the effects of leaf abscission on leaf miner survival in the absence of deer. The leaf miner eclosed successfully from both fallen leaves and leaves retained on trees. However, sika deer (Cervus nippon centralis Kishida) feed on the fallen mined leaves. Field observations showed that deer consume many fallen leaves under Q. gilva trees, suggesting considerable mortality of leaf miners due to deer predation via leaf abscission. This is a previously unreported relationship between a leaf miner and a mammalian herbivore via leaf abscission.

  10. Ethephon induced abscission in mango: physiological fruitlet responses

    PubMed Central

    Hagemann, Michael H.; Winterhagen, Patrick; Hegele, Martin; Wünsche, Jens N.

    2015-01-01

    Fruitlet abscission of mango is typically very severe, causing considerable production losses worldwide. Consequently, a detailed physiological and molecular characterization of fruitlet abscission in mango is required to describe the onset and time-dependent course of this process. To identify the underlying key mechanisms of abscission, ethephon, an ethylene releasing substance, was applied at two concentrations (600 and 7200 ppm) during the midseason drop stage of mango. The abscission process is triggered by ethylene diffusing to the abscission zone where it binds to specific receptors and thereby activating several key physiological responses at the cellular level. The treatments reduced significantly the capacity of polar auxin transport through the pedicel at 1 day after treatment and thereafter when compared to untreated pedicels. The transcript levels of the ethylene receptor genes MiETR1 and MiERS1 were significantly upregulated in the pedicel and pericarp at 1, 2, and 3 days after the ethephon application with 7200 ppm, except for MiETR1 in the pedicel, when compared to untreated fruitlet. In contrast, ethephon applications with 600 ppm did not affect expression levels of MiETR1 in the pedicel and of MiERS1 in the pericarp; however, MiETR1 in the pericarp at day 2 and MiERS1 in the pedicel at days 2 and 3 were significantly upregulated over the controls. Moreover, two novel short versions of the MiERS1 were identified and detected more often in the pedicel of treated than untreated fruitlets at all sampling times. Sucrose concentration in the fruitlet pericarp was significantly reduced to the control at 2 days after both ethephon treatments. In conclusion, it is postulated that the ethephon-induced abscission process commences with a reduction of the polar auxin transport capacity in the pedicel, followed by an upregulation of ethylene receptors and finally a decrease of the sucrose concentration in the fruitlets. PMID:26442021

  11. The site of water stress governs the pattern of ABA synthesis and transport in peanut

    PubMed Central

    Hu, Bo; Cao, Jiajia; Ge, Kui; Li, Ling

    2016-01-01

    Abscisic acid (ABA) is one of the most important phytohormones involved in stress responses in plants. However, knowledge of the effect on ABA distribution and transport of water stress at different sites on the plant is limited. In this study, water stress imposed on peanut leaves or roots by treatment with PEG 6000 is termed “leaf stress” or “root stress”, respectively. Immunoenzyme localization technolony was first used to detect ABA distribution in peanut. Under root stress, ABA biosynthesis and distribution level were all more pronounced in root than in leaf. However, ABA transport and the ability to induce stomatal closure were still better in leaf than in root during root stress; However, ABA biosynthesis initially increased in leaf, then rapidly accumulated in the vascular cambium of leaves and induced stomatal closure under leaf stress; ABA produced in root tissues was also transported to leaf tissues to maintain stomatal closure. The vascular system was involved in the coordination and integration of this complex regulatory mechanism for ABA signal accumulation. Water stress subject to root or leaf results in different of ABA biosynthesis and transport ability that trigger stoma close in peanut. PMID:27694957

  12. Arabidopsis CPR5 Independently Regulates Seed Germination and Postgermination Arrest of Development through LOX Pathway and ABA Signaling

    PubMed Central

    Yang, Xiang; Wang, Yaqin; Su, Xiaojun; Du, Jinju; Yang, Chengwei

    2011-01-01

    The phytohormone abscisic acid (ABA) and the lipoxygenases (LOXs) pathway play important roles in seed germination and seedling growth and development. Here, we reported on the functional characterization of Arabidopsis CPR5 in the ABA signaling and LOX pathways. The cpr5 mutant was hypersensitive to ABA in the seed germination, cotyledon greening and root growth, whereas transgenic plants overexpressing CPR5 were insensitive. Genetic analysis demonstrated that CPR5 gene may be located downstream of the ABI1 in the ABA signaling pathway. However, the cpr5 mutant showed an ABA independent drought-resistant phenotype. It was also found that the cpr5 mutant was hypersensitive to NDGA and NDGA treatment aggravated the ABA-induced delay in the seed germination and cotyledon greening. Taken together, these results suggest that the CPR5 plays a regulatory role in the regulation of seed germination and early seedling growth through ABA and LOX pathways independently. PMID:21556325

  13. Structural basis for selective activation of ABA receptors

    SciTech Connect

    Peterson, Francis C.; Burgie, E. Sethe; Park, Sang-Youl; Jensen, Davin R.; Weiner, Joshua J.; Bingman, Craig A.; Chang, Chia-En A.; Cutler, Sean R.; Phillips, Jr., George N.; Volkman, Brian F.

    2010-11-01

    Changing environmental conditions and lessening fresh water supplies have sparked intense interest in understanding and manipulating abscisic acid (ABA) signaling, which controls adaptive responses to drought and other abiotic stressors. We recently discovered a selective ABA agonist, pyrabactin, and used it to discover its primary target PYR1, the founding member of the PYR/PYL family of soluble ABA receptors. To understand pyrabactin's selectivity, we have taken a combined structural, chemical and genetic approach. We show that subtle differences between receptor binding pockets control ligand orientation between productive and nonproductive modes. Nonproductive binding occurs without gate closure and prevents receptor activation. Observations in solution show that these orientations are in rapid equilibrium that can be shifted by mutations to control maximal agonist activity. Our results provide a robust framework for the design of new agonists and reveal a new mechanism for agonist selectivity.

  14. ULK3 regulates cytokinetic abscission by phosphorylating ESCRT-III proteins.

    PubMed

    Caballe, Anna; Wenzel, Dawn M; Agromayor, Monica; Alam, Steven L; Skalicky, Jack J; Kloc, Magdalena; Carlton, Jeremy G; Labrador, Leticia; Sundquist, Wesley I; Martin-Serrano, Juan

    2015-05-26

    The endosomal sorting complexes required for transport (ESCRT) machinery mediates the physical separation between daughter cells during cytokinetic abscission. This process is regulated by the abscission checkpoint, a genome protection mechanism that relies on Aurora B and the ESCRT-III subunit CHMP4C to delay abscission in response to chromosome missegregation. In this study, we show that Unc-51-like kinase 3 (ULK3) phosphorylates and binds ESCRT-III subunits via tandem MIT domains, and thereby, delays abscission in response to lagging chromosomes, nuclear pore defects, and tension forces at the midbody. Our structural and biochemical studies reveal an unusually tight interaction between ULK3 and IST1, an ESCRT-III subunit required for abscission. We also demonstrate that IST1 phosphorylation by ULK3 is an essential signal required to sustain the abscission checkpoint and that ULK3 and CHMP4C are functionally linked components of the timer that controls abscission in multiple physiological situations.

  15. REGULATION OF ETHYLENE EVOLUTION AND LEAF ABSCISSION BY AUXIN

    DTIC Science & Technology

    It is shown that auxin enhanced ethylene evolution occurs in a variety of plant material, and that ethylene evolution can be constrolled by...endogenous as well as exogenous levels of auxin . The importance of auxin regulated ethylene evolution on a physiological process is demonstrated by investigating the abscission of bean petiole explants.

  16. The Citrus ABA signalosome: identification and transcriptional regulation during sweet orange fruit ripening and leaf dehydration

    PubMed Central

    Rodrigo, María J.

    2012-01-01

    The abscisic acid (ABA) signalling core in plants include the cytosolic ABA receptors (PYR/PYL/RCARs), the clade-A type 2C protein phosphatases (PP2CAs), and the subclass III SNF1-related protein kinases 2 (SnRK2s). The aim of this work was to identify these ABA perception system components in sweet orange and to determine the influence of endogenous ABA on their transcriptional regulation during fruit development and ripening, taking advantage of the comparative analysis between a wild-type and a fruit-specific ABA-deficient mutant. Transcriptional changes in the ABA signalosome during leaf dehydration were also studied. Six PYR/PYL/RCAR, five PP2CA, and two subclass III SnRK2 genes, homologous to those of Arabidopsis, were identified in the Citrus genome. The high degree of homology and conserved motifs for protein folding and for functional activity suggested that these Citrus proteins are bona fide core elements of ABA perception in orange. Opposite expression patterns of CsPYL4 and CsPYL5 and ABA accumulation were found during ripening, although there were few differences between varieties. In contrast, changes in expression of CsPP2CA genes during ripening paralleled those of ABA content and agreeed with the relevant differences between wild-type and mutant fruit transcript accumulation. CsSnRK2 gene expression continuously decreased with ripening and no remarkable differences were found between cultivars. Overall, dehydration had a minor effect on CsPYR/PYL/RCAR and CsSnRK2 expression in vegetative tissue, whereas CsABI1, CsAHG1, and CsAHG3 were highly induced by water stress. The global results suggest that responsiveness to ABA changes during citrus fruit ripening, and leaf dehydration was higher in the CsPP2CA gene negative regulators than in the other ABA signalosome components. PMID:22888124

  17. Catalytic mechanism and kinase interactions of ABA-signaling PP2C phosphatases.

    PubMed

    Zhou, X Edward; Soon, Fen-Fen; Ng, Ley-Moy; Kovach, Amanda; Suino-Powell, Kelly M; Li, Jun; Yong, Eu-Leong; Zhu, Jian-Kang; Xu, H Eric; Melcher, Karsten

    2012-05-01

    Abscisic acid (ABA) is an essential hormone that controls plant growth, development and responses to abiotic stresses. ABA signaling is mediated by type 2C protein phosphatases (PP2Cs), including HAB1 and ABI2, which inhibit stress-activated SnRK2 kinases and whose activity is regulated by ABA and ABA receptors. Based on biochemical data and our previously determined crystal structures of ABI2 and the SnRK2.6-HAB1 complex, we present the catalytic mechanism of PP2C and provide new insight into PP2C-SnRK2 interactions and possible roles of other SnRK2 kinases in ABA signaling.

  18. Electrical signaling, stomatal conductance, ABA and ethylene content in avocado trees in response to root hypoxia.

    PubMed

    Gil, Pilar M; Gurovich, Luis; Schaffer, Bruce; García, Nicolás; Iturriaga, Rodrigo

    2009-02-01

    Avocado (Persea americana Mill.) trees are among the most sensitive of fruit tree species to root hypoxia as a result of flooded or poorly drained soil. Similar to drought stress, an early physiological response to root hypoxia in avocado is a reduction of stomatal conductance. It has been previously determined in avocado trees that an extracellular electrical signal between the base of stem and leaves is produced and related to reductions in stomatal conductance in response to drought stress. The current study was designed to determine if changes in the extracellular electrical potential between the base of the stem and leaves in avocado trees could also be detected in response to short-term (min) or long-term (days) root hypoxia, and if these signals could be related to stomatal conductance (gs), root and leaf ABA and ACC concentrations, ethylene emission from leaves and leaf abscission. In contrast to previous observations for drought-stressed trees, short-term or long-term root hypoxia did not stimulate an electrical potential difference between the base of the stem and leaves. Short-term hypoxia did not result in a significant decrease in gs compared with plants in the control treatment, and no differences in ABA concentration were found between plants subjected to hypoxia and control plants. Long-term hypoxia in the root zone resulted in a significant decrease in gs, increased leaf ethylene and increased leaf abscission. The results indicate that for avocado trees exposed to root hypoxia, electrical signals do not appear to be the primary root-to-shoot communication mechanism involved in signaling for stomatal closure as a result of hypoxia in the root zone.

  19. Electrical signaling, stomatal conductance, ABA and Ethylene content in avocado trees in response to root hypoxia

    PubMed Central

    Gurovich, Luis; Schaffer, Bruce; García, Nicolás; Iturriaga, Rodrigo

    2009-01-01

    Avocado (Persea americana Mill.) trees are among the most sensitive of fruit tree species to root hypoxia as a result of flooded or poorly drained soil. Similar to drought stress, an early physiological response to root hypoxia in avocado is a reduction of stomatal conductance. It has been previously determined in avocado trees that an extracellular electrical signal between the base of stem and leaves is produced and related to reductions in stomatal conductance in response to drought stress. The current study was designed to determine if changes in the extracellular electrical potential between the base of the stem and leaves in avocado trees could also be detected in response to short-term (min) or long-term (days) root hypoxia, and if these signals could be related to stomatal conductance (gs), root and leaf ABA and ACC concentrations, ethylene emission from leaves and leaf abscission. In contrast to previous observations for drought-stressed trees, short-term or long-term root hypoxia did not stimulate an electrical potential difference between the base of the stem and leaves. Short-term hypoxia did not result in a significant decrease in gs compared with plants in the control treatment, and no differences in ABA concentration were found between plants subjected to hypoxia and control plants. Long-term hypoxia in the root zone resulted in a significant decrease in gs, increased leaf ethylene and increased leaf abscission. The results indicate that for avocado trees exposed to root hypoxia, electrical signals do not appear to be the primary root-to-shoot communication mechanism involved in signaling for stomatal closure as a result of hypoxia in the root zone. PMID:19649181

  20. Comprehensive analysis of SAUR gene family in citrus and its transcriptional correlation with fruitlet drop from abscission zone A.

    PubMed

    Xie, Rangjin; Dong, Cuicui; Ma, Yanyan; Deng, Lie; He, Shaolan; Yi, Shilai; Lv, Qiang; Zheng, Yongqiang

    2015-11-01

    Small auxin-up RNA (SAUR) gene family is large, and the members of which can be rapidly induced by auxin and encode highly unstable mRNAs. SAUR genes are involved in various developmental and physiological processes, such as leaf senescence, fruitlet abscission, and hypocotyl development. However, their modes of action in citrus remain unknown. Hereby, a systematic analysis of SAUR gene family in citrus was conducted through a genome-wide search. In this study, a total of 70 SAUR genes, referred to as CitSAURs, have been identified in citrus. The evolutionary relationship and the intro-exon organization were analyzed, revealing strong gene conservation and the expansion of particular functional genes during plant evolution. Expression analysis showed that the major of CitSAUR genes were expressed in at least one tissue and showed distinctive expression levels, indicating the SAUR gene family play important roles in the development and growth of citrus organs. However, there were more than 20 CitSAUR genes such as CitSARU36, CitSAUR37, and CitSAUR54 exhibiting very low expression level in all tissue tested. Twenty-three out of 70 CitSAUR genes were responded to indole-3-acetic acid (IAA) treatment, of which just CitSAUR19 was down-regulated. Additionally, 14 CitSAUR genes exhibited distinct changes during fruitlet abscission, however just 5 of them including CitSAUR06, CitSAUR08, CitSAUR44, CitSAUR61, and CitSAUR64 were associated with fruitlet abscission. The current study provides basic information for the citrus SAUR gene family and will pave the way for deciphering the precise role of SAURs in citrus development and growth as well as fruitlet abscission.

  1. The HAB1 PP2C is inhibited by ABA-dependent PYL10 interaction.

    PubMed

    Li, Juan; Shi, Chaowei; Sun, Demeng; He, Yao; Lai, Chaohua; Lv, Pei; Xiong, Ying; Zhang, Longhua; Wu, Fangming; Tian, Changlin

    2015-06-05

    PYL10 is a monomeric abscisic acid (ABA) receptor that inhibits protein phosphatase 2C (PP2C) activity in Arabidopsis thaliana. Previous studies reported that the PP2C phosphatase inhibition by PYL10 was ABA-independent. Here, systematic PYL10 biochemical studies demonstrated that PYL10 activity was ABA-dependent, and the previously reported studies was interfered by the presence of BSA in the commercial kit. To investigate dynamic mechanism of how ABA binding to PYL10 induces PP2C phosphatase inhibiting activity, solution NMR relaxation analysis of apo-PYL10 and PYL10/ABA were conducted following backbone resonance assignments. Reduced spectrum density mapping of the backbone relaxation data revealed that PYL10 was more flexible in ABA bound form than apo-PYL10, indicating an increased conformational entropy upon ligand binding. Moreover, to illustrate conformation exchanges of PYL10 upon ABA binding, NMR line shape analysis was performed with increasing concentrations of ABA, and the results indicated that PYL10 backbone conformational changes occur at different time scales.

  2. ABA in bryophytes: how a universal growth regulator in life became a plant hormone?

    PubMed

    Takezawa, Daisuke; Komatsu, Kenji; Sakata, Yoichi

    2011-07-01

    Abscisic acid (ABA) is not a plant-specific compound but one found in organisms across kingdoms from bacteria to animals, suggesting that it is a ubiquitous and versatile substance that can modulate physiological functions of various organisms. Recent studies have shown that plants developed an elegant system for ABA sensing and early signal transduction mechanisms to modulate responses to environmental stresses for survival in terrestrial conditions. ABA-induced increase in stress tolerance has been reported not only in vascular plants but also in non-vascular bryophytes. Since bryophytes are the key group of organisms in the context of plant evolution, clarification of their ABA-dependent processes is important for understanding evolutionary adaptation of land plants. Molecular approaches using Physcomitrella patens have revealed that ABA plays a role in dehydration stress tolerance in mosses, which comprise a major group of bryophytes. Furthermore, we recently reported that signaling machinery for ABA responses is also conserved in liverworts, representing the most basal members of extant land plant lineage. Conservation of the mechanism for ABA sensing and responses in angiosperms and basal land plants suggests that acquisition of this mechanism for stress tolerance in vegetative tissues was one of the critical evolutionary events for adaptation to the land. This review describes the role of ABA in basal land plants as well as non-land plant organisms and further elaborates on recent progress in molecular studies of model bryophytes by comparative and functional genomic approaches.

  3. ABA-mediated transcriptional regulation in response to osmotic stress in plants.

    PubMed

    Fujita, Yasunari; Fujita, Miki; Shinozaki, Kazuo; Yamaguchi-Shinozaki, Kazuko

    2011-07-01

    The plant hormone abscisic acid (ABA) plays a pivotal role in a variety of developmental processes and adaptive stress responses to environmental stimuli in plants. Cellular dehydration during the seed maturation and vegetative growth stages induces an increase in endogenous ABA levels, which control many dehydration-responsive genes. In Arabidopsis plants, ABA regulates nearly 10% of the protein-coding genes, a much higher percentage than other plant hormones. Expression of the genes is mainly regulated by two different families of bZIP transcription factors (TFs), ABI5 in the seeds and AREB/ABFs in the vegetative stage, in an ABA-responsive-element (ABRE) dependent manner. The SnRK2-AREB/ABF pathway governs the majority of ABA-mediated ABRE-dependent gene expression in response to osmotic stress during the vegetative stage. In addition to osmotic stress, the circadian clock and light conditions also appear to participate in the regulation of ABA-mediated gene expression, likely conferring versatile tolerance and repressing growth under stress conditions. Moreover, various other TFs belonging to several classes, including AP2/ERF, MYB, NAC, and HD-ZF, have been reported to engage in ABA-mediated gene expression. This review mainly focuses on the transcriptional regulation of ABA-mediated gene expression in response to osmotic stress during the vegetative growth stage in Arabidopsis.

  4. Antagonistic effect of polyamines on ABA-induced suppression of mitosis in Allium cepa L.

    PubMed

    Mahajan, Arpana; Sharma, Shashi

    2009-02-01

    Effect of abscisic acid (ABA) and polyamines (PAs) [putrescine (Put), spermidine (Spd) and spermine (Spm)] on mitosis in root tips of A. cepa was studied. Treatment with ABA (0.1 to 100 microM) for 24 hr suppressed the mitosis, measured as mitotic index (MI), in a concentration-dependent manner with approx. 50% suppression at 10 microM of ABA. Treatment with different PAs (1 to 100 microM) had differential mitosis suppression effect. Spm was most inhibitory followed by Spd and Put, respectively. The higher concentrations of PAs (1 mM Put; 0.1 and 1 mM Spd or Spm) caused cell distortion. Remarkably, a 24 hr pretreatment of root tips with PAs prior to ABA (100 microM) treatment resulted in a general concentration-dependent reversal of ABA-induced suppression of MI. Catalase (CAT) activity in the root tips, an indicator of redox metabolism, increased due to ABA treatment in a concentration-dependent manner, remained unaltered in response to Put and declined due to Spd and Spm (> or = 0.1 mM). However, all PAs, irrespective of their individual effects, generally antagonized the ABA-dependent increase in CAT activity. Data indicate the possibility of ABA-PA interaction in the regulation of mitosis.

  5. De novo transcriptome sequencing and customized abscission zone-specific microarray as a new molecular tool for analysis of tomato organ abscission

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Abscission, which is the process of organ separation, is a highly regulated process occurring as a final stage of organ development. In the tomato (Solanum lycopersicum) system, flower and leaf abscission was induced by flower removal or leaf deblading, leading to auxin depletion which results in in...

  6. ABA accumulation in water-stressed Citrus roots does not rely on carotenoid content in this organ.

    PubMed

    Manzi, Matías; Lado, Joanna; Rodrigo, María Jesús; Arbona, Vicent; Gómez-Cadenas, Aurelio

    2016-11-01

    Sustained abscisic acid (ABA) accumulation in dehydrated citrus roots depends on the transport from aerial organs. Under this condition, the role of the β,β-carotenoids (ABA precursors) to the de novo synthesis of ABA in roots needs to be clarified since their low availability in this organ restricts its accumulation. To accomplish that, detached citrus roots were exposed to light (to increase their carotenoid content) and subsequently dehydrated (to trigger ABA accumulation). Stress imposition sharply decreased the pool of β,β-carotenoids but, unexpectedly, no concomitant rise in ABA content was observed. Contrastingly, roots of intact plants (with low levels of carotenoids) showed a similar decrease of ABA precursor together with a significant ABA accumulation. Furthermore, upon dehydration both types of roots showed similar upregulation of the key genes involved in biosynthesis of carotenoids and ABA (CsPSY3a; CsβCHX1; CsβCHX2; CsNCED1; CsNCED2), demonstrating a conserved transcriptional response triggered by water stress. Thus, the sharp decrease in root carotenoid levels in response to dehydration should be related to other stress-related signals instead of contributing to ABA biosynthesis. In summary, ABA accumulation in dehydrated-citrus roots largely relies on the presence of the aerial organs and it is independent of the amount of available root β,β-carotenoids.

  7. Plant responses to drought stress and exogenous ABA application are modulated differently by mycorrhization in tomato and an ABA-deficient mutant (sitiens).

    PubMed

    Aroca, Ricardo; Del Mar Alguacil, Maria; Vernieri, Paolo; Ruiz-Lozano, Juan Manuel

    2008-11-01

    The aims of the present study are to find out whether the effects of arbuscular mycorrhizal (AM) symbiosis on plant resistance to water deficit are mediated by the endogenous abscisic acid (ABA) content of the host plant and whether the exogenous ABA application modifies such effects. The ABA-deficient tomato mutant sitiens and its near-isogenic wild-type parental line were used. Plant development, physiology, and expression of plant genes expected to be modulated by AM symbiosis, drought, and ABA were studied. Results showed that only wild-type tomato plants responded positively to mycorrhizal inoculation, while AM symbiosis was not observed to have any effect on plant development in sitiens plants grown under well-watered conditions. The application of ABA to sitiens plants enhanced plant growth both under well-watered and drought stress conditions. In respect to sitiens plants subjected to drought stress, the addition of ABA had a cumulative effect in relation to that of inoculation with G. intraradices. Most of the genes analyzed in this study showed different regulation patterns in wild-type and sitiens plants, suggesting that their gene expression is modulated by the plant ABA phenotype. In the same way, the colonization of roots with the AM fungus G. intraradices differently regulated the expression of these genes in wild-type and in sitiens plants, which could explain the distinctive effect of the symbiosis on each plant ABA phenotype. This also suggests that the effects of the AM symbiosis on plant responses and resistance to water deficit are mediated by the plant ABA phenotype.

  8. The wheat ABA hypersensitive ERA8 mutant is associated with increased preharvest sprouting tolerance and altered hormone accumulation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wheat preharvest sprouting (PHS) is the germination of mature grain on the mother plant when rain occurs before harvest. Higher abscisic acid (ABA) hormone levels and sensitivity are associated with higher seed dormancy and PHS tolerance. Consistent with this, the ABA hypersensitive ERA8 (Enhanced...

  9. ABA inhibits germination but not dormancy release in mature imbibed seeds of Lolium rigidum Gaud.

    PubMed Central

    Goggin, Danica E.; Steadman, Kathryn J.; Emery, R. J. Neil; Farrow, Scott C.; Benech-Arnold, Roberto L.; Powles, Stephen B.

    2009-01-01

    Dormancy release in imbibed annual ryegrass (Lolium rigidum Gaud.) seeds is promoted in the dark but inhibited in the light. The role of abscisic acid (ABA) in inhibition of dormancy release was found to be negligible, compared with its subsequent effect on germination of dormant and non-dormant seeds. Inhibitors of ABA metabolism had the expected effects on seed germination but did not influence ABA concentration, suggesting that they act upon other (unknown) factors regulating dormancy. Although gibberellin (GA) synthesis was required for germination, the influence of exogenous GA on both germination and dormancy release was minor or non-existent. Embryo ABA concentration was the same following treatments to promote (dark stratification) and inhibit (light stratification) dormancy release; exogenous ABA had no effect on this process. However, the sensitivity of dark-stratified seeds to ABA supplied during germination was lower than that of light-stratified seeds. Therefore, although ABA definitely plays a role in the germination of annual ryegrass seeds, it is not the major factor mediating inhibition of dormancy release in imbibed seeds. PMID:19487389

  10. Production of ABA responses requires both the nuclear and cytoplasmic functional involvement of PYR1.

    PubMed

    Park, EunJoo; Kim, Tae-Houn

    2017-02-26

    Abscisic acid (ABA) enhances stress tolerant responses in plants against unfavorable environmental conditions. In Arabidopsis, ABA promotes interactions between PYR/PYL/RCARs and PP2C, thereby allowing SnRK2s to phosphorylate downstream components required for the regulation of gene expression or for gating ion channels. Because PYR1 is known to localize to nucleus and cytoplasm it is a question whether nuclear or cytoplasmic PYR1 confer different functions to the ABA signaling pathway, as has been previously shown for regulatory proteins. In order to answer this question, transgenic lines expressing nuclear PYR1 were generated in an ABA insensitive mutant background. Enforced nuclear expression of PYR1 was examined by confocal microscopy and western blot analysis. Physiological analyses of the transgenic lines demonstrated that nuclear PYR1 is sufficient to generate ABA responses, such as, the inhibition of seed germination, root growth inhibition, the induction of gene expression, and stomatal closing movement. However, for the full recovery of ABA responses in the mutant background cytoplasmic PYR1 was required. The study suggests both nuclear and cytoplasmic PYR1 participate in the control of ABA signal transduction.

  11. The Arabidopsis transcription factor ABIG1 relays ABA signaled growth inhibition and drought induced senescence

    PubMed Central

    Liu, Tie; Longhurst, Adam D; Talavera-Rauh, Franklin; Hokin, Samuel A; Barton, M Kathryn

    2016-01-01

    Drought inhibits plant growth and can also induce premature senescence. Here we identify a transcription factor, ABA INSENSITIVE GROWTH 1 (ABIG1) required for abscisic acid (ABA) mediated growth inhibition, but not for stomatal closure. ABIG1 mRNA levels are increased both in response to drought and in response to ABA treatment. When treated with ABA, abig1 mutants remain greener and produce more leaves than comparable wild-type plants. When challenged with drought, abig1 mutants have fewer yellow, senesced leaves than wild-type. Induction of ABIG1 transcription mimics ABA treatment and regulates a set of genes implicated in stress responses. We propose a model in which drought acts through ABA to increase ABIG1 transcription which in turn restricts new shoot growth and promotes leaf senescence. The results have implications for plant breeding: the existence of a mutant that is both ABA resistant and drought resistant points to new strategies for isolating drought resistant genetic varieties. DOI: http://dx.doi.org/10.7554/eLife.13768.001 PMID:27697148

  12. A Comprehensive Proteomic Survey of ABA-Induced Protein Phosphorylation in Rice (Oryza sativa L.)

    PubMed Central

    Qiu, Jiehua; Hou, Yuxuan; Wang, Yifeng; Li, Zhiyong; Zhao, Juan; Tong, Xiaohong; Lin, Haiyan; Wei, Xiangjin; Ao, Hejun; Zhang, Jian

    2017-01-01

    abscisic acid (ABA) is a key phytohormone regulating plant development and stress response. The signal transduction of ABA largely relies on protein phosphorylation. However; little is known about the phosphorylation events occurring during ABA signaling in rice thus far. By employing a label-free; MS (Mass Spectrometry)-based phosphoproteomic approach; we identified 2271 phosphosites of young rice seedlings and their intensity dynamics in response to ABA; during which 1060 proteins were found to be differentially phosphorylated. Western-blot analysis verified the differential phosphorylation pattern of D1, SMG1 and SAPK9 as indicated by the MS result; suggesting the high reliability of our phosphoproteomic data. The DP (differentially phosphorylated) proteins are extensively involved in ABA as well as other hormone signaling pathways. It is suggested that ABA antagonistically regulates brassinosteroid (BR) signaling via inhibiting BR receptor activity. The result of this study not only expanded our knowledge of rice phosphoproteome, but also shed more light on the pattern of protein phosphorylation in ABA signaling. PMID:28054942

  13. Linking Turgor with ABA Biosynthesis: Implications for Stomatal Responses to Vapor Pressure Deficit across Land Plants.

    PubMed

    McAdam, Scott A M; Brodribb, Timothy J

    2016-07-01

    Stomatal responses to changes in vapor pressure deficit (VPD) constitute the predominant form of daytime gas-exchange regulation in plants. Stomatal closure in response to increased VPD is driven by the rapid up-regulation of foliar abscisic acid (ABA) biosynthesis and ABA levels in angiosperms; however, very little is known about the physiological trigger for this increase in ABA biosynthesis at increased VPD Using a novel method of modifying leaf cell turgor by the application of external pressures, we test whether changes in turgor pressure can trigger increases in foliar ABA levels over 20 min, a period of time most relevant to the stomatal response to VPD We found in angiosperm species that the biosynthesis of ABA was triggered by reductions in leaf turgor, and in two species tested, that a higher sensitivity of ABA synthesis to leaf turgor corresponded with a higher stomatal sensitivity to VPD In contrast, representative species from nonflowering plant lineages did not show a rapid turgor-triggered increase in foliar ABA levels, which is consistent with previous studies demonstrating passive stomatal responses to changes in VPD in these lineages. Our method provides a new tool for characterizing the response of stomata to water availability.

  14. ABA inhibits germination but not dormancy release in mature imbibed seeds of Lolium rigidum Gaud.

    PubMed

    Goggin, Danica E; Steadman, Kathryn J; Emery, R J Neil; Farrow, Scott C; Benech-Arnold, Roberto L; Powles, Stephen B

    2009-01-01

    Dormancy release in imbibed annual ryegrass (Lolium rigidum Gaud.) seeds is promoted in the dark but inhibited in the light. The role of abscisic acid (ABA) in inhibition of dormancy release was found to be negligible, compared with its subsequent effect on germination of dormant and non-dormant seeds. Inhibitors of ABA metabolism had the expected effects on seed germination but did not influence ABA concentration, suggesting that they act upon other (unknown) factors regulating dormancy. Although gibberellin (GA) synthesis was required for germination, the influence of exogenous GA on both germination and dormancy release was minor or non-existent. Embryo ABA concentration was the same following treatments to promote (dark stratification) and inhibit (light stratification) dormancy release; exogenous ABA had no effect on this process. However, the sensitivity of dark-stratified seeds to ABA supplied during germination was lower than that of light-stratified seeds. Therefore, although ABA definitely plays a role in the germination of annual ryegrass seeds, it is not the major factor mediating inhibition of dormancy release in imbibed seeds.

  15. The NF-YC–RGL2 module integrates GA and ABA signalling to regulate seed germination in Arabidopsis

    PubMed Central

    Liu, Xu; Hu, Pengwei; Huang, Mingkun; Tang, Yang; Li, Yuge; Li, Ling; Hou, Xingliang

    2016-01-01

    The antagonistic crosstalk between gibberellic acid (GA) and abscisic acid (ABA) plays a pivotal role in the modulation of seed germination. However, the molecular mechanism of such phytohormone interaction remains largely elusive. Here we show that three Arabidopsis NUCLEAR FACTOR-Y C (NF-YC) homologues NF-YC3, NF-YC4 and NF-YC9 redundantly modulate GA- and ABA-mediated seed germination. These NF-YCs interact with the DELLA protein RGL2, a key repressor of GA signalling. The NF-YC–RGL2 module targets ABI5, a gene encoding a core component of ABA signalling, via specific CCAAT elements and collectively regulates a set of GA- and ABA-responsive genes, thus controlling germination. These results suggest that the NF-YC–RGL2–ABI5 module integrates GA and ABA signalling pathways during seed germination. PMID:27624486

  16. Abscission is regulated by the ESCRT-III protein shrub in Drosophila germline stem cells.

    PubMed

    Matias, Neuza Reis; Mathieu, Juliette; Huynh, Jean-René

    2015-02-01

    Abscission is the final event of cytokinesis that leads to the physical separation of the two daughter cells. Recent technical advances have allowed a better understanding of the cellular and molecular events leading to abscission in isolated yeast or mammalian cells. However, how abscission is regulated in different cell types or in a developing organism remains poorly understood. Here, we characterized the function of the ESCRT-III protein Shrub during cytokinesis in germ cells undergoing a series of complete and incomplete divisions. We found that Shrub is required for complete abscission, and that levels of Shrub are critical for proper timing of abscission. Loss or gain of Shrub delays abscission in germline stem cells (GSCs), and leads to the formation of stem-cysts, where daughter cells share the same cytoplasm as the mother stem cell and cannot differentiate. In addition, our results indicate a negative regulation of Shrub by the Aurora B kinase during GSC abscission. Finally, we found that Lethal giant discs (lgd), known to be required for Shrub function in the endosomal pathway, also regulates the duration of abscission in GSCs.

  17. Natural Variation in Fruit Abscission-Related Traits in Apple (Malus)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Abscission or retention of ripening fruit is a major component of seed dispersal strategies and also has important implications for horticultural production. Abscission-related traits have generally not been targeted in breeding efforts, and their genetic bases remain mostly unknown. We evaluated ...

  18. MOLECULAR ANALYSIS OF THE INTERACTION OF ETHYLENE AND AUXIN DURING FLOWER ABSCISSION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Abscission, the separation of organs from the parent plant, results in postharvest quality loss in many ornamentals and other fresh produce. The process is initiated by changes in the auxin gradient across the abscission zone (AZ), is triggered by ethylene, and may be accelerated by postharvest stre...

  19. Nitric oxide modulates sensitivity to ABA

    PubMed Central

    Lozano-Juste, Jorge

    2010-01-01

    Nitric oxide (NO) is a gas with crucial signaling functions in plant defense and development. As demonstrated by generating a triple nia1nia2noa1-2 mutant with extremely low levels of NO (February 2010 issue of Plant Physiology), NO is synthesized in plants through mainly two different pathways involving nitrate reductase (NR/NIA) and NO Associated 1 (AtNOA1) proteins. Depletion of basal NO levels leads to a priming of ABA-triggered responses that causes hypersensitivity to this hormone and results in enhanced seed dormancy and decreased seed germination and seedling establishment in the triple mutant. NO produced under non-stressed conditions represses inhibition of seed developmental transitions by ABA. Moreover, NO plays a positive role in post-germinative vegetative development and also exerts a critical control of ABA-related functions on stomata closure. The triple nia1nia2noa1-2 mutant is hypersensitive to ABA in stomatal closure thus resulting in a extreme phenotype of resistance to drought. In the light of the recent discovery of PYR/PYL/RCAR as a family of potential ABA receptors, regulation of ABA sensitivity by NO may be exerted either directly on ABA receptors or on downstream signalling components; both two aspects that deserve our present and future attention. PMID:20168082

  20. ATR and a Chk1-Aurora B pathway coordinate postmitotic genome surveillance with cytokinetic abscission

    PubMed Central

    Mackay, Douglas R.; Ullman, Katharine S.

    2015-01-01

    Aurora B regulates cytokinesis timing and plays a central role in the abscission checkpoint. Cellular events monitored by this checkpoint are beginning to be elucidated, yet signaling pathways upstream of Aurora B in this context remain poorly understood. Here we reveal a new connection between postmitotic genome surveillance and cytokinetic abscission. Underreplicated DNA lesions are known to be transmitted through mitosis and protected in newly formed nuclei by recruitment of 53BP1 and other proteins until repair takes place. We find that this genome surveillance initiates before completion of cytokinesis. Elevating replication stress increases this postmitotic process and delays cytokinetic abscission by keeping the abscission checkpoint active. We further find that ATR activity in midbody-stage cells links postmitotic genome surveillance to abscission timing and that Chk1 integrates this and other signals upstream of Aurora B to regulate when the final step in the physical separation of daughter cells occurs. PMID:25904336

  1. ABA- and ethylene-mediated responses in osmotically stressed tomato are regulated by the TSS2 and TOS1 loci.

    PubMed

    Rosado, Abel; Amaya, Iraida; Valpuesta, Victoriano; Cuartero, Jesús; Botella, Miguel A; Borsani, Omar

    2006-01-01

    The study of mutants impaired in the sensitivity or synthesis of abscisic acid (ABA) has become a powerful tool to analyse the interactions occurring between the ABA and ethylene signalling pathways, with potential to change the traditional view of the role of ABA as just being involved in growth inhibition. The tss2 tomato mutant, which is hypersensitive to NaCl and osmotic stress, shows enhanced growth inhibition in the presence of exogenous ABA. The tos1 tomato mutant is also hypersensitive to osmotic stress, but in contrast to tss2, shows decreased sensitivity to ABA. Surprisingly, blocking ethylene signalling suppresses the growth defect of tss2 seedlings on ABA, NaCl, and osmotic stress, but not the osmotic hypersensitivity of tos1. The ethylene production of tss2 seedlings is increased compared with that of control seedlings under osmotic stress. In addition, the tss2 plants are hypersensitive to root growth inhibition by the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC). This suggests that, in addition to ABA regulation, TSS2 acts as a negative regulator of endogenous ethylene accumulation. As previously shown in Arabidopsis, it is shown here that extensive cross-talk occurs between the ABA and ethylene signalling pathways in tomato and that the TSS2 and TOS1 loci appear as regulators of this cross-talk.

  2. Ethylene-induced differential gene expression during abscission of citrus leaves

    PubMed Central

    Merelo, Paz; Cercós, Manuel; Tadeo, Francisco R.; Talón, Manuel

    2008-01-01

    The main objective of this work was to identify and classify genes involved in the process of leaf abscission in Clementina de Nules (Citrus clementina Hort. Ex Tan.). A 7 K unigene citrus cDNA microarray containing 12 K spots was used to characterize the transcriptome of the ethylene-induced abscission process in laminar abscission zone-enriched tissues and the petiole of debladed leaf explants. In these conditions, ethylene induced 100% leaf explant abscission in 72 h while, in air-treated samples, the abscission period started later and took 240 h. Gene expression monitored during the first 36 h of ethylene treatment showed that out of the 12 672 cDNA microarray probes, ethylene differentially induced 725 probes distributed as follows: 216 (29.8%) probes in the laminar abscission zone and 509 (70.2%) in the petiole. Functional MIPS classification and manual annotation of differentially expressed genes highlighted key processes regulating the activation and progress of the cell separation that brings about abscission. These included cell-wall modification, lipid transport, protein biosynthesis and degradation, and differential activation of signal transduction and transcription control pathways. Expression data associated with the petiole indicated the occurrence of a double defensive strategy mediated by the activation of a biochemical programme including scavenging ROS, defence and PR genes, and a physical response mostly based on lignin biosynthesis and deposition. This work identifies new genes probably involved in the onset and development of the leaf abscission process and suggests a different but co-ordinated and complementary role for the laminar abscission zone and the petiole during the process of abscission. PMID:18515267

  3. Role of PP2C-mediated ABA signaling in the moss Physcomitrella patens.

    PubMed

    Sakata, Yoichi; Komatsu, Kenji; Taji, Teruaki; Tanaka, Shigeo

    2009-09-01

    Plant hormone abscisic acid (ABA) is found in a wide range of land plants, from mosses to angiosperms. However, our knowledge concerning the function of ABA is limited to some angiosperm plant species. We have shown that the basal land plant Physcomitrella patens and the model plant Arabidopsis thaliana share a conserved abscisic acid (ABA) signaling pathway mediated through ABI1-related type 2C protein phosphatases (PP2Cs). Ectopic expression of Arabidopsis abi1-1, a dominant allele of ABI1 that functions as a negative regulator of ABA signaling, or targeted disruption of Physcomitrella ABI1-related gene (PpABI1A) resulted in altered ABA sensitivity and abiotic stress tolerance of Physcomitrella, as demonstrated by osmostress and freezing stress. Moreover, transgenic Physcomitrella overexpressing abi1-1 showed altered morphogenesis. These transgenic plants had longer stem lengths compared to the wild type, and continuous growth of archegonia (female organ) with few sporophytes under non-stress conditions. Our results suggest that PP2C-mediated ABA signaling is involved in both the abiotic stress responses and developmental regulation of Physcomitrella.

  4. Inhibitors of abscisic acid 8'-hydroxylase.

    PubMed

    Cutler, A J; Rose, P A; Squires, T M; Loewen, M K; Shaw, A C; Quail, J W; Krochko, J E; Abrams, S R

    2000-11-07

    Structural analogues of the phytohormone (+)-abscisic acid (ABA) have been synthesized and tested as inhibitors of the catabolic enzyme (+)-ABA 8'-hydroxylase. Assays employed microsomes from suspension-cultured corn cells. Four of the analogues [(+)-8'-acetylene-ABA, (+)-9'-propargyl-ABA, (-)-9'-propargyl-ABA, and (+)-9'-allyl-ABA] proved to be suicide substrates of ABA 8'-hydroxylase. For each suicide substrate, inactivation required NADPH, increased with time, and was blocked by addition of the natural substrate, (+)-ABA. The most effective suicide substrate was (+)-9'-propargyl-ABA (K(I) = 0.27 microM). Several analogues were competitive inhibitors of ABA 8'-hydroxylase, of which the most effective was (+)-8'-propargyl-ABA (K(i) = 1.1 microM). Enzymes in the microsomal extracts also hydroxylated (-)-ABA at the 7'-position at a low rate. This activity was not inhibited by the suicide substrates, showing that the 7'-hydroxylation of (-)-ABA was catalyzed by a different enzyme from that which catalyzed 8'-hydroxylation of (+)-ABA. Based on the results described, a simple model for the positioning of substrates in the active site of ABA 8'-hydroxylase is proposed. In a representative physiological assay, inhibition of Arabidopsis thaliana seed germination, (+)-9'-propargyl-ABA and (+)-8'-acetylene-ABA exhibited substantially stronger hormonal activity than (+)-ABA itself.

  5. Ascorbate Alleviates Fe Deficiency-Induced Stress in Cotton (Gossypium hirsutum) by Modulating ABA Levels.

    PubMed

    Guo, Kai; Tu, Lili; Wang, Pengcheng; Du, Xueqiong; Ye, Shue; Luo, Ming; Zhang, Xianlong

    2016-01-01

    Fe deficiency causes significant losses to crop productivity and quality. To understand better the mechanisms of plant responses to Fe deficiency, we used an in vitro cotton ovule culture system. We found that Fe deficiency suppressed the development of ovules and fibers, and led to tissue browning. RNA-seq analysis showed that the myo-inositol and galacturonic acid pathways were activated and cytosolic APX (ascorbate peroxidase) was suppressed in Fe-deficient treated fibers, which increased ASC (ascorbate) concentrations to prevent tissue browning. Suppression of cytosolic APX by RNAi in cotton increased ASC contents and delayed tissue browning by maintaining ferric reduction activity under Fe-deficient conditions. Meanwhile, APX RNAi line also exhibited the activation of expression of iron-regulated transporter (IRT1) and ferric reductase-oxidase2 (FRO2) to adapt to Fe deficiency. Abscisic acid (ABA) levels were significantly decreased in Fe-deficient treated ovules and fibers, while the upregulated expression of ABA biosynthesis genes and suppression of ABA degradation genes in Fe-deficient ovules slowed down the decreased of ABA in cytosolic APX suppressed lines to delay the tissue browning. Moreover, the application of ABA in Fe-deficient medium suppressed the development of tissue browning and completely restored the ferric reduction activity. In addition, ABA 8'-hydroxylase gene (GhABAH1) overexpressed cotton has a decreased level of ABA and shows more sensitivity to Fe deficiency. Based on the results, we speculate that ASC could improve the tolerance to Fe deficiency through activating Fe uptake and maintaining ABA levels in cotton ovules and fibers, which in turn reduces symptom formation.

  6. Ascorbate Alleviates Fe Deficiency-Induced Stress in Cotton (Gossypium hirsutum) by Modulating ABA Levels

    PubMed Central

    Guo, Kai; Tu, Lili; Wang, Pengcheng; Du, Xueqiong; Ye, Shue; Luo, Ming; Zhang, Xianlong

    2017-01-01

    Fe deficiency causes significant losses to crop productivity and quality. To understand better the mechanisms of plant responses to Fe deficiency, we used an in vitro cotton ovule culture system. We found that Fe deficiency suppressed the development of ovules and fibers, and led to tissue browning. RNA-seq analysis showed that the myo-inositol and galacturonic acid pathways were activated and cytosolic APX (ascorbate peroxidase) was suppressed in Fe-deficient treated fibers, which increased ASC (ascorbate) concentrations to prevent tissue browning. Suppression of cytosolic APX by RNAi in cotton increased ASC contents and delayed tissue browning by maintaining ferric reduction activity under Fe-deficient conditions. Meanwhile, APX RNAi line also exhibited the activation of expression of iron-regulated transporter (IRT1) and ferric reductase–oxidase2 (FRO2) to adapt to Fe deficiency. Abscisic acid (ABA) levels were significantly decreased in Fe-deficient treated ovules and fibers, while the upregulated expression of ABA biosynthesis genes and suppression of ABA degradation genes in Fe-deficient ovules slowed down the decreased of ABA in cytosolic APX suppressed lines to delay the tissue browning. Moreover, the application of ABA in Fe-deficient medium suppressed the development of tissue browning and completely restored the ferric reduction activity. In addition, ABA 8′-hydroxylase gene (GhABAH1) overexpressed cotton has a decreased level of ABA and shows more sensitivity to Fe deficiency. Based on the results, we speculate that ASC could improve the tolerance to Fe deficiency through activating Fe uptake and maintaining ABA levels in cotton ovules and fibers, which in turn reduces symptom formation. PMID:28101095

  7. Are diurnal patterns of stomatal movement the result of alternating metabolism of endogenous guard cell ABA and accumulation of ABA delivered to the apoplast around guard cells by transpiration?

    PubMed

    Tallman, Gary

    2004-09-01

    Abscisic acid (ABA) prevents opening of closed stomata and causes open stomata to close. A dual-source model is proposed linking ABA to diurnal stomatal movements. Darkness would favour guard cell biosynthesis of endogenous ABA and disfavour ABA catabolism. At first light, xanthophyll cycling, isomerization of ABA precursors, and activation of a cytochrome P450 mono-oxygenase (CytP450) would deplete endogenous guard cell ABA. The NADPH-requiring CytP450 would be activated by elevated O2 and reduced CO2 concentrations resulting from mesophyll photosynthesis. An increased O2-to-CO2 ratio would limit the Calvin cycle in guard cells, diverting NADPH produced by photosynthetic electron transport to the cytosol where, along with elevated O2, it would activate CytP450. Depletion of endogenous ABA would liberate guard cells to extrude protons and accumulate the ions and water needed to increase guard cell turgor and open stomata. By midday, stomata would be regulated by steady-state concentrations of ABA delivered to the apoplast around guard cells by transpiration. In temperate conditions, ABA would reach concentrations high enough to trigger ion efflux from guard cells, but too low to defeat the accumulation of sugars used to maintain opening. In dry conditions, ABA would reach effective concentrations by midday, high enough to trigger ion efflux and inhibit sugar uptake, reducing apertures for the rest of the day. At sunset, conditions would again favour biosynthesis and disfavour catabolism of endogenous guard cell ABA. The model can be used to reconcile proposed cellular mechanisms for guard cell signal transduction with patterns of stomatal movements in leaves.

  8. Eph-mediated tyrosine phosphorylation of citron kinase controls abscission

    PubMed Central

    Jungas, Thomas; Perchey, Renaud T.; Fawal, Mohamad; Callot, Caroline; Froment, Carine; Burlet-Schiltz, Odile; Besson, Arnaud

    2016-01-01

    Cytokinesis is the last step of cell division, culminating in the physical separation of daughter cells at the end of mitosis. Cytokinesis is a tightly regulated process that until recently was mostly viewed as a cell-autonomous event. Here, we investigated the role of Ephrin/Eph signaling, a well-known local cell-to-cell communication pathway, in cell division. We show that activation of Eph signaling in vitro leads to multinucleation and polyploidy, and we demonstrate that this is caused by alteration of the ultimate step of cytokinesis, abscission. Control of abscission requires Eph kinase activity, and Src and citron kinase (CitK) are downstream effectors in the Eph-induced signal transduction cascade. CitK is phosphorylated on tyrosines in neural progenitors in vivo, and Src kinase directly phosphorylates CitK. We have identified the specific tyrosine residues of CitK that are phosphorylated and show that tyrosine phosphorylation of CitK impairs cytokinesis. Finally, we show that, similar to CitK, Ephrin/Eph signaling controls neuronal ploidy in the developing neocortex. Our study indicates that CitK integrates intracellular and extracellular signals provided by the local environment to coordinate completion of cytokinesis. PMID:27551053

  9. Primary and Secondary Abscission in Pisum sativum and Euphorbia pulcherrima—How Do They Compare and How Do They Differ?

    PubMed Central

    Hvoslef-Eide, Anne K.; Munster, Cristel M.; Mathiesen, Cecilie A.; Ayeh, Kwadwo O.; Melby, Tone I.; Rasolomanana, Paoly; Lee, YeonKyeong

    2016-01-01

    Abscission is a highly regulated and coordinated developmental process in plants. It is important to understand the processes leading up to the event, in order to better control abscission in crop plants. This has the potential to reduce yield losses in the field and increase the ornamental value of flowers and potted plants. A reliable method of abscission induction in poinsettia (Euphorbia pulcherrima) flowers has been established to study the process in a comprehensive manner. By correctly decapitating buds of the third order, abscission can be induced in 1 week. AFLP differential display (DD) was used to search for genes regulating abscission. Through validation using qRT-PCR, more information of the genes involved during induced secondary abscission have been obtained. A study using two pea (Pisum sativum) mutants in the def (Developmental funiculus) gene, which was compared with wild type peas (tall and dwarf in both cases) was performed. The def mutant results in a deformed, abscission-less zone instead of normal primary abscission at the funiculus. RNA in situ hybridization studies using gene sequences from the poinsettia differential display, resulted in six genes differentially expressed for abscission specific genes in both poinsettia and pea. Two of these genes are associated with gene up- or down-regulation during the first 2 days after decapitation in poinsettia. Present and previous results in poinsettia (biochemically and gene expressions), enables a more detailed division of the secondary abscission phases in poinsettia than what has previously been described from primary abscission in Arabidopsis. This study compares the inducible secondary abscission in poinsettia and the non-abscising mutants/wild types in pea demonstrating primary abscission zones. The results may have wide implications on the understanding of abscission, since pea and poinsettia have been separated for 94–98 million years in evolution, hence any genes or processes in common

  10. Cross-talk between environmental stresses and plant metabolism during reproductive organ abscission

    PubMed Central

    Sawicki, Mélodie; Aït Barka, Essaïd; Clément, Christophe; Vaillant-Gaveau, Nathalie; Jacquard, Cédric

    2015-01-01

    In plants, flowering is a crucial process for reproductive success and continuity of the species through time. Fruit production requires the perfect development of reproductive structures. Abscission, a natural process, can occur to facilitate shedding of no longer needed, infected, or damaged organs. If stress occurs during flower development, abscission can intervene at flower level, leading to reduced yield. Flower abscission is a highly regulated developmental process simultaneously influenced and activated in response to exogenous (changing environmental conditions, interactions with microorganisms) and endogenous (physiological modifications) stimuli. During climate change, plant communities will be more susceptible to environmental stresses, leading to increased flower and fruit abscission, and consequently a decrease in fruit yield. Understanding the impacts of stress on the reproductive phase is therefore critical for managing future agricultural productivity. Here, current knowledge on flower/fruit abscission is summarized by focusing specifically on effects of environmental stresses leading to this process in woody plants. Many of these stresses impair hormonal balance and/or carbohydrate metabolism, but the exact mechanisms are far from completely known. Hormones are the abscission effectors and the auxin/ethylene balance is of particular importance. The carbohydrate pathway is the result of complex regulatory processes involving the balance between photosynthesis and mobilization of reserves. Hormones and carbohydrates together participate in complex signal transduction systems, especially in response to stress. The available data are discussed in relation to reproductive organ development and the process of abscission. PMID:25711702

  11. ULK3 regulates cytokinetic abscission by phosphorylating ESCRT-III proteins

    PubMed Central

    Caballe, Anna; Wenzel, Dawn M; Agromayor, Monica; Alam, Steven L; Skalicky, Jack J; Kloc, Magdalena; Carlton, Jeremy G; Labrador, Leticia; Sundquist, Wesley I; Martin-Serrano, Juan

    2015-01-01

    The endosomal sorting complexes required for transport (ESCRT) machinery mediates the physical separation between daughter cells during cytokinetic abscission. This process is regulated by the abscission checkpoint, a genome protection mechanism that relies on Aurora B and the ESCRT-III subunit CHMP4C to delay abscission in response to chromosome missegregation. In this study, we show that Unc-51-like kinase 3 (ULK3) phosphorylates and binds ESCRT-III subunits via tandem MIT domains, and thereby, delays abscission in response to lagging chromosomes, nuclear pore defects, and tension forces at the midbody. Our structural and biochemical studies reveal an unusually tight interaction between ULK3 and IST1, an ESCRT-III subunit required for abscission. We also demonstrate that IST1 phosphorylation by ULK3 is an essential signal required to sustain the abscission checkpoint and that ULK3 and CHMP4C are functionally linked components of the timer that controls abscission in multiple physiological situations. DOI: http://dx.doi.org/10.7554/eLife.06547.001 PMID:26011858

  12. Interplay between ABA and GA Modulates the Timing of Asymmetric Cell Divisions in the Arabidopsis Root Ground Tissue.

    PubMed

    Lee, Shin Ae; Jang, Sejeong; Yoon, Eun Kyung; Heo, Jung-Ok; Chang, Kwang Suk; Choi, Ji Won; Dhar, Souvik; Kim, Gyuree; Choe, Jeong-Eun; Heo, Jae Bok; Kwon, Chian; Ko, Jae-Heung; Hwang, Yong-Sic; Lim, Jun

    2016-06-06

    In multicellular organisms, controlling the timing and extent of asymmetric cell divisions (ACDs) is crucial for correct patterning. During post-embryonic root development in Arabidopsis thaliana, ground tissue (GT) maturation involves an additional ACD of the endodermis, which generates two different tissues: the endodermis (inner) and the middle cortex (outer). It has been reported that the abscisic acid (ABA) and gibberellin (GA) pathways are involved in middle cortex (MC) formation. However, the molecular mechanisms underlying the interaction between ABA and GA during GT maturation remain largely unknown. Through transcriptome analyses, we identified a previously uncharacterized C2H2-type zinc finger gene, whose expression is regulated by GA and ABA, thus named GAZ (GA- AND ABA-RESPONSIVE ZINC FINGER). Seedlings ectopically overexpressing GAZ (GAZ-OX) were sensitive to ABA and GA during MC formation, whereas GAZ-SRDX and RNAi seedlings displayed opposite phenotypes. In addition, our results indicated that GAZ was involved in the transcriptional regulation of ABA and GA homeostasis. In agreement with previous studies that ABA and GA coordinate to control the timing of MC formation, we also confirmed the unique interplay between ABA and GA and identified factors and regulatory networks bridging the two hormone pathways during GT maturation of the Arabidopsis root.

  13. The Arabidopsis MIEL1 E3 ligase negatively regulates ABA signalling by promoting protein turnover of MYB96

    PubMed Central

    Lee, Hong Gil; Seo, Pil Joon

    2016-01-01

    The phytohormone abscisic acid (ABA) regulates plant responses to various environmental challenges. Controlled protein turnover is an important component of ABA signalling. Here we show that the RING-type E3 ligase MYB30-INTERACTING E3 LIGASE 1 (MIEL1) regulates ABA sensitivity by promoting MYB96 turnover in Arabidopsis. Germination of MIEL1-deficient mutant seeds is hypersensitive to ABA, whereas MIEL1-overexpressing transgenic seeds are less sensitive. MIEL1 can interact with MYB96, a regulator of ABA signalling, and stimulate its ubiquitination and degradation. Genetic analysis shows that MYB96 is epistatic to MIEL1 in the control of ABA sensitivity in seeds. While MIEL1 acts primarily via MYB96 in seed germination, MIEL1 regulates protein turnover of both MYB96 and MYB30 in vegetative tissues. We find that ABA regulates the expression of MYB30-responsive genes during pathogen infection and this regulation is partly dependent on MIEL1. These results suggest that MIEL1 may facilitate crosstalk between ABA and biotic stress signalling. PMID:27615387

  14. The ABA receptor PYL9 together with PYL8 plays an important role in regulating lateral root growth

    PubMed Central

    Xing, Lu; Zhao, Yang; Gao, Jinghui; Xiang, Chengbin; Zhu, Jian-Kang

    2016-01-01

    Abscisic acid is a phytohormone regulating plant growth, development and stress responses. PYR1/PYL/RCAR proteins are ABA receptors that function by inhibiting PP2Cs to activate SnRK2s, resulting in phosphorylation of ABFs and other effectors of ABA response pathways. Exogenous ABA induces growth quiescence of lateral roots, which is prolonged by knockout of the ABA receptor PYL8. Among the 14 members of PYR1/PYL/RCAR protein family, PYL9 is a close relative of PYL8. Here we show that knockout of both PYL9 and PYL8 resulted in a longer ABA-induced quiescence on lateral root growth and a reduced sensitivity to ABA on primary root growth and lateral root formation compared to knockout of PYL8 alone. Induced overexpression of PYL9 promoted the lateral root elongation in the presence of ABA. The prolonged quiescent phase of the pyl8-1pyl9 double mutant was reversed by exogenous IAA. PYL9 may regulate auxin-responsive genes in vivo through direct interaction with MYB77 and MYB44. Thus, PYL9 and PYL8 are both responsible for recovery of lateral root from ABA inhibition via MYB transcription factors. PMID:27256015

  15. Auxin involvement in tepal senescence and abscission in Lilium: a tale of two lilies

    PubMed Central

    Lombardi, Lara; Arrom, Laia; Mariotti, Lorenzo; Battelli, Riccardo; Picciarelli, Piero; Kille, Peter; Stead, Tony; Munné-Bosch, Sergi; Rogers, Hilary J.

    2015-01-01

    Petal wilting and/or abscission terminates the life of the flower. However, how wilting and abscission are coordinated is not fully understood. There is wide variation in the extent to which petals wilt before abscission, even between cultivars of the same species. For example, tepals of Lilium longiflorum wilt substantially, while those of the closely related Lilium longiflorum×Asiatic hybrid (L.A.) abscise turgid. Furthermore, close comparison of petal death in these two Lilium genotypes shows that there is a dramatic fall in fresh weight/dry weight accompanied by a sharp increase in ion leakage in late senescent L. longiflorum tepals, neither of which occur in Lilium L.A. Despite these differences, a putative abscission zone was identified in both lilies, but while the detachment force was reduced to zero in Lilium L.A., wilting of the fused tepals in L. longiflorum occurred before abscission was complete. Abscission is often negatively regulated by auxin, and the possible role of auxin in regulating tepal abscission relative to wilting was tested in the two lilies. There was a dramatic increase in auxin levels with senescence in L. longiflorum but not in Lilium L.A. Fifty auxin-related genes were expressed in early senescent L. longiflorum tepals including 12 ARF-related genes. In Arabidopsis, several ARF genes are involved in the regulation of abscission. Expression of a homologous transcript to Arabidopsis ARF7/19 was 8-fold higher during senescence in L. longiflorum compared with abscising Lilium L.A., suggesting a conserved role for auxin-regulated abscission in monocotyledonous ethylene-insensitive flowers. PMID:25422499

  16. Relationship between petal abscission and programmed cell death in Prunus yedoensis and Delphinium belladonna

    PubMed Central

    Yamada, Tetsuya; Ichimura, Kazuo

    2007-01-01

    Depending on the species, the end of flower life span is characterized by petal wilting or by abscission of petals that are still fully turgid. Wilting at the end of petal life is due to programmed cell death (PCD). It is not known whether the abscission of turgid petals is preceded by PCD. We studied some parameters that indicate PCD: chromatin condensation, a decrease in nuclear diameter, DNA fragmentation, and DNA content per nucleus, using Prunus yedoensis and Delphiniumbelladonna which both show abscission of turgid petals at the end of floral life. No DNA degradation, no chromatin condensation, and no change in nuclear volume was observed in P. yedoensis petals, prior to abscission. In abscising D.belladonna petals, in contrast, considerable DNA degradation was found, chromatin was condensed and the nuclear volume considerably reduced. Following abscission, the nuclear area in both species drastically increased, and the chromatin became unevenly distributed. Similar chromatin changes were observed after dehydration (24 h at 60°C) of petals severed at the time of flower opening, and in dehydrated petals of Ipomoea nil and Petunia hybrida, severed at the time of flower opening. In these flowers the petal life span is terminated by wilting rather than abscission. It is concluded that the abscission of turgid petals in D. belladonna was preceded by a number of PCD indicators, whereas no such evidence for PCD was found at the time of P. yedoensis petal abscission. Dehydration of the petal cells, after abscission, was associated with a remarkable nuclear morphology which was also found in younger petals subjected to dehydration. This nuclear morphology has apparently not been described previously, for any organism. PMID:17618454

  17. Relationship between petal abscission and programmed cell death in Prunus yedoensis and Delphinium belladonna.

    PubMed

    Yamada, Tetsuya; Ichimura, Kazuo; van Doorn, Wouter G

    2007-10-01

    Depending on the species, the end of flower life span is characterized by petal wilting or by abscission of petals that are still fully turgid. Wilting at the end of petal life is due to programmed cell death (PCD). It is not known whether the abscission of turgid petals is preceded by PCD. We studied some parameters that indicate PCD: chromatin condensation, a decrease in nuclear diameter, DNA fragmentation, and DNA content per nucleus, using Prunus yedoensis and Delphinium belladonna which both show abscission of turgid petals at the end of floral life. No DNA degradation, no chromatin condensation, and no change in nuclear volume was observed in P. yedoensis petals, prior to abscission. In abscising D. belladonna petals, in contrast, considerable DNA degradation was found, chromatin was condensed and the nuclear volume considerably reduced. Following abscission, the nuclear area in both species drastically increased, and the chromatin became unevenly distributed. Similar chromatin changes were observed after dehydration (24 h at 60 degrees C) of petals severed at the time of flower opening, and in dehydrated petals of Ipomoea nil and Petunia hybrida, severed at the time of flower opening. In these flowers the petal life span is terminated by wilting rather than abscission. It is concluded that the abscission of turgid petals in D. belladonna was preceded by a number of PCD indicators, whereas no such evidence for PCD was found at the time of P. yedoensis petal abscission. Dehydration of the petal cells, after abscission, was associated with a remarkable nuclear morphology which was also found in younger petals subjected to dehydration. This nuclear morphology has apparently not been described previously, for any organism.

  18. Auxin involvement in tepal senescence and abscission in Lilium: a tale of two lilies.

    PubMed

    Lombardi, Lara; Arrom, Laia; Mariotti, Lorenzo; Battelli, Riccardo; Picciarelli, Piero; Kille, Peter; Stead, Tony; Munné-Bosch, Sergi; Rogers, Hilary J

    2015-02-01

    Petal wilting and/or abscission terminates the life of the flower. However, how wilting and abscission are coordinated is not fully understood. There is wide variation in the extent to which petals wilt before abscission, even between cultivars of the same species. For example, tepals of Lilium longiflorum wilt substantially, while those of the closely related Lilium longiflorum×Asiatic hybrid (L.A.) abscise turgid. Furthermore, close comparison of petal death in these two Lilium genotypes shows that there is a dramatic fall in fresh weight/dry weight accompanied by a sharp increase in ion leakage in late senescent L. longiflorum tepals, neither of which occur in Lilium L.A. Despite these differences, a putative abscission zone was identified in both lilies, but while the detachment force was reduced to zero in Lilium L.A., wilting of the fused tepals in L. longiflorum occurred before abscission was complete. Abscission is often negatively regulated by auxin, and the possible role of auxin in regulating tepal abscission relative to wilting was tested in the two lilies. There was a dramatic increase in auxin levels with senescence in L. longiflorum but not in Lilium L.A. Fifty auxin-related genes were expressed in early senescent L. longiflorum tepals including 12 ARF-related genes. In Arabidopsis, several ARF genes are involved in the regulation of abscission. Expression of a homologous transcript to Arabidopsis ARF7/19 was 8-fold higher during senescence in L. longiflorum compared with abscising Lilium L.A., suggesting a conserved role for auxin-regulated abscission in monocotyledonous ethylene-insensitive flowers.

  19. Design and Functional Characterization of a Novel Abscisic Acid Analog

    PubMed Central

    Han, Xiaoqiang; Jiang, Lun; Che, Chuanliang; Wan, Chuan; Lu, Huizhe; Xiao, Yumei; Xu, Yanjun; Chen, Zhongzhou; Qin, Zhaohai

    2017-01-01

    The phytohormone abscisic acid (ABA) plays a crucial role in mediating plant growth and development by recruiting genetically redundant ABA receptors. To overcome its oxidation inactivation, we developed a novel ABA analog named 2′,3′-benzo-iso-ABA (iso-PhABA) and studied its function and structural characterization with A. thaliana ABA receptors. The (+)-iso-PhABA form showed much higher ABA-like activities than (+)-ABA including inhibitory effects on the seed germination of lettuce and A. thaliana, wheat embryo germination and rice seedling elongation. The PP2C (protein phosphatases 2C) activity assay showed that (+)-iso-PhABA acted as a potent and selective ABA receptor agonist, which is preferred to PYL10. In some cases, (−)-iso-PhABA showed moderate to high activity for the PYL protein inhibiting PP2C activity, suggesting different mechanisms of action of iso-PhABA and ABA. The complex crystal structure of iso-PhABA with PYL10 was determined and elucidated successfully, revealing that (+)-iso-PhABA was better coordinated in the same binding pocket compared to (+)-ABA. Moreover, the detailed interaction network of iso-PhABA/PYL10 was disclosed and involves hydrogen bonds and multiple hydrophobic interactions that provide a robust framework for the design of novel ABA receptor agonists/antagonists. PMID:28272449

  20. De novo Transcriptome Sequencing and Development of Abscission Zone-Specific Microarray as a New Molecular Tool for Analysis of Tomato Organ Abscission

    PubMed Central

    Sundaresan, Srivignesh; Philosoph-Hadas, Sonia; Riov, Joseph; Mugasimangalam, Raja; Kuravadi, Nagesh A.; Kochanek, Bettina; Salim, Shoshana; Tucker, Mark L.; Meir, Shimon

    2016-01-01

    Abscission of flower pedicels and leaf petioles of tomato (Solanum lycopersicum) can be induced by flower removal or leaf deblading, respectively, which leads to auxin depletion, resulting in increased sensitivity of the abscission zone (AZ) to ethylene. However, the molecular mechanisms that drive the acquisition of abscission competence and its modulation by auxin gradients are not yet known. We used RNA-Sequencing (RNA-Seq) to obtain a comprehensive transcriptome of tomato flower AZ (FAZ) and leaf AZ (LAZ) during abscission. RNA-Seq was performed on a pool of total RNA extracted from tomato FAZ and LAZ, at different abscission stages, followed by de novo assembly. The assembled clusters contained transcripts that are already known in the Solanaceae (SOL) genomics and NCBI databases, and over 8823 identified novel tomato transcripts of varying sizes. An AZ-specific microarray, encompassing the novel transcripts identified in this study and all known transcripts from the SOL genomics and NCBI databases, was constructed to study the abscission process. Multiple probes for longer genes and key AZ-specific genes, including antisense probes for all transcripts, make this array a unique tool for studying abscission with a comprehensive set of transcripts, and for mining for naturally occurring antisense transcripts. We focused on comparing the global transcriptomes generated from the FAZ and the LAZ to establish the divergences and similarities in their transcriptional networks, and particularly to characterize the processes and transcriptional regulators enriched in gene clusters that are differentially regulated in these two AZs. This study is the first attempt to analyze the global gene expression in different AZs in tomato by combining the RNA-Seq technique with oligonucleotide microarrays. Our AZ-specific microarray chip provides a cost-effective approach for expression profiling and robust analysis of multiple samples in a rapid succession. PMID:26834766

  1. Expression of ABA Metabolism-Related Genes Suggests Similarities and Differences Between Seed Dormancy and Bud Dormancy of Peach (Prunus persica)

    PubMed Central

    Wang, Dongling; Gao, Zhenzhen; Du, Peiyong; Xiao, Wei; Tan, Qiuping; Chen, Xiude; Li, Ling; Gao, Dongsheng

    2016-01-01

    Dormancy inhibits seed and bud growth of perennial plants until the environmental conditions are optimal for survival. Previous studies indicated that certain co-regulation pathways exist in seed and bud dormancy. In our study, we found that seed and bud dormancy are similar to some extent but show different reactions to chemical treatments that induce breaking of dormancy. Whether the abscisic acid (ABA) regulatory networks are similar in dormant peach seeds and buds is not well known; however, ABA is generally believed to play a critical role in seed and bud dormancy. In peach, some genes putatively involved in ABA synthesis and catabolism were identified and their expression patterns were studied to learn more about ABA homeostasis and the possible crosstalk between bud dormancy and seed dormancy mechanisms. The analysis demonstrated that two 9-cis-epoxycarotenoid dioxygenase-encoding genes seem to be key in regulating ABA biosynthesis to induce seed and bud dormancy. Three CYP707As play an overlapping role in controlling ABA inactivation, resulting in dormancy-release. In addition, Transcript analysis of ABA metabolism-related genes was much similar demonstrated that ABA pathways was similar in the regulation of vegetative and flower bud dormancy, whereas, expression patterns of ABA metabolism-related genes were different in seed dormancy showed that ABA pathway maybe different in regulating seed dormancy in peach. PMID:26793222

  2. Expression of ABA Metabolism-Related Genes Suggests Similarities and Differences Between Seed Dormancy and Bud Dormancy of Peach (Prunus persica).

    PubMed

    Wang, Dongling; Gao, Zhenzhen; Du, Peiyong; Xiao, Wei; Tan, Qiuping; Chen, Xiude; Li, Ling; Gao, Dongsheng

    2015-01-01

    Dormancy inhibits seed and bud growth of perennial plants until the environmental conditions are optimal for survival. Previous studies indicated that certain co-regulation pathways exist in seed and bud dormancy. In our study, we found that seed and bud dormancy are similar to some extent but show different reactions to chemical treatments that induce breaking of dormancy. Whether the abscisic acid (ABA) regulatory networks are similar in dormant peach seeds and buds is not well known; however, ABA is generally believed to play a critical role in seed and bud dormancy. In peach, some genes putatively involved in ABA synthesis and catabolism were identified and their expression patterns were studied to learn more about ABA homeostasis and the possible crosstalk between bud dormancy and seed dormancy mechanisms. The analysis demonstrated that two 9-cis-epoxycarotenoid dioxygenase-encoding genes seem to be key in regulating ABA biosynthesis to induce seed and bud dormancy. Three CYP707As play an overlapping role in controlling ABA inactivation, resulting in dormancy-release. In addition, Transcript analysis of ABA metabolism-related genes was much similar demonstrated that ABA pathways was similar in the regulation of vegetative and flower bud dormancy, whereas, expression patterns of ABA metabolism-related genes were different in seed dormancy showed that ABA pathway maybe different in regulating seed dormancy in peach.

  3. Loss of heterophylly in aquatic plants: not ABA-mediated stress but exogenous ABA treatment induces stomatal leaves in Potamogeton perfoliatus.

    PubMed

    Iida, Satoko; Ikeda, Miyuki; Amano, Momoe; Sakayama, Hidetoshi; Kadono, Yasuro; Kosuge, Keiko

    2016-09-01

    Heterophyllous aquatic plants produce aerial (i.e., floating and terrestrial) and submerged leaves-the latter lack stomata-while homophyllous plants contain only submerged leaves, and cannot survive on land. To identify whether differences in morphogenetic potential and/or physiological stress responses are responsible for variation in phenotypic plasticity between two plants types, responses to abscisic acid (ABA) and salinity stress were compared between the closely related, but ecologically diverse pondweeds, Potamogeton wrightii (heterophyllous) and P. perfoliatus (homophyllous). The ABA-treated (1 or 10 μM) P. wrightii plants exhibited heterophylly and produced leaves with stomata. The obligate submerged P. perfoliatus plants were able to produce stomata on their leaves, but there were no changes to leaf shape, and stomatal production occurred only at a high ABA concentration (10 μM). Under salinity stress conditions, only P. wrightii leaves formed stomata. Additionally, the expression of stress-responsive NCED genes, which encode a key enzyme in ABA biosynthesis, was consistently up-regulated in P. wrightii, but only temporarily in P. perfoliatus. The observed species-specific gene expression patterns may be responsible for the induction or suppression of stomatal production during exposure to salinity stress. These results suggest that the two Potamogeton species have an innate morphogenetic ability to form stomata, but the actual production of stomata depends on ABA-mediated stress responses specific to each species and habitat.

  4. Auxin is a long-range signal that acts independently of ethylene signaling on leaf abscission in Populus

    PubMed Central

    Jin, Xu; Zimmermann, Jorma; Polle, Andrea; Fischer, Urs

    2015-01-01

    Timing of leaf abscission is an important trait for biomass production and seasonal acclimation in deciduous trees. The signaling leading to organ separation, from the external cue (decreasing photoperiod) to ethylene-regulated hydrolysis of the middle lamellae in the abscission zone, is only poorly understood. Data from annual species indicate that the formation of an auxin gradient spanning the abscission zone regulates the timing of abscission. We established an experimental system in Populus to induce leaf shedding synchronously under controlled greenhouse conditions in order to test the function of auxin in leaf abscission. Here, we show that exogenous auxin delayed abscission of dark-induced leaves over short and long distances and that a new auxin response maximum preceded the formation of an abscission zone. Several auxin transporters were down-regulated during abscission and inhibition of polar auxin transport delayed leaf shedding. Ethylene signaling was not involved in the regulation of these auxin transporters and in the formation of an abscission zone, but was required for the expression of hydrolytic enzymes associated with cell separation. Since exogenous auxin delayed abscission in absence of ethylene signaling auxin likely acts independently of ethylene signaling on cell separation. PMID:26322071

  5. Motor activity of centromere-associated protein-E contributes to its localization at the center of the midbody to regulate cytokinetic abscission

    PubMed Central

    Ohashi, Akihiro; Ohori, Momoko; Iwai, Kenichi

    2016-01-01

    Accurate control of cytokinesis is critical for genomic stability to complete high-fidelity transmission of genetic material to the next generation. A number of proteins accumulate in the intercellular bridge (midbody) during cytokinesis, and the dynamics of these proteins are temporally and spatially orchestrated to complete the process. In this study, we demonstrated that localization of centromere-associated protein-E (CENP-E) at the midbody is involved in cytokinetic abscission. The motor activity of CENP-E and the C-terminal midbody localization domain, which includes amino acids 2659–2666 (RYFDNSSL), are involved in the anchoring of CENP-E to the center of the midbody. Furthermore, CENP-E motor activity contributes to the accumulation of protein regulator of cytokinesis 1 (PRC1) in the midbody during cytokinesis. Midbody localization of PRC1 is critical to the antiparallel microtubule structure and recruitment of other midbody-associated proteins. Therefore, CENP-E motor activity appears to play important roles in the organization of these proteins to complete cytokinetic abscission. Our findings will be helpful for understanding how each step of cytokinesis is regulated to complete cytokinetic abscission. PMID:27835888

  6. Transcriptomic Analysis Reveals Possible Influences of ABA on Secondary Metabolism of Pigments, Flavonoids and Antioxidants in Tomato Fruit during Ripening

    PubMed Central

    Mou, Wangshu; Li, Dongdong; Luo, Zisheng; Mao, Linchun; Ying, Tiejin

    2015-01-01

    Abscisic acid (ABA) has been proven to be involved in the regulation of climacteric fruit ripening, but a comprehensive investigation of its influence on ripening related processes is still lacking. By applying the next generation sequencing technology, we conducted a comparative analysis of the effects of exogenous ABA and NDGA (Nordihydroguaiaretic acid, an inhibitor of ABA biosynthesis) on tomato fruit ripening. The high throughput sequencing results showed that out of the 25728 genes expressed across all three samples, 10388 were identified as significantly differently expressed genes. Exogenous ABA was found to enhance the transcription of genes involved in pigments metabolism, including carotenoids biosynthesis and chlorophyll degradation, whereas NDGA treatment inhibited these processes. The results also revealed the crucial role of ABA in flavonoids synthesis and regulation of antioxidant system. Intriguingly, we also found that an inhibition of endogenous ABA significantly enhanced the transcriptional abundance of genes involved in photosynthesis. Our results highlighted the significance of ABA in regulating tomato ripening, which provided insight into the regulatory mechanism of fruit maturation and senescence process. PMID:26053166

  7. Mycorrhizal and non-mycorrhizal Lactuca sativa plants exhibit contrasting responses to exogenous ABA during drought stress and recovery

    PubMed Central

    Aroca, Ricardo; Vernieri, Paolo; Ruiz-Lozano, Juan Manuel

    2008-01-01

    The arbuscular mycorrhizal (AM) symbiosis enhances plant tolerance to water deficit through the alteration of plant physiology and the expression of plant genes. These changes have been postulated to be caused (among others) by different contents of abscisic acid (ABA) between AM and non-AM plants. However, there are no studies dealing with the effects of exogenous ABA on the expression of stress-related genes and on the physiology of AM plants. The aim of the present study was to evaluate the influence of AM symbiosis and exogenous ABA application on plant development, physiology, and expression of several stress-related genes after both drought and a recovery period. Results show that the application of exogenous ABA had contrasting effects on AM and non-AM plants. Only AM plants fed with exogenous ABA maintained shoot biomass production unaltered by drought stress. The addition of exogenous ABA enhanced considerably the ABA content in shoots of non-AM plants, concomitantly with the expression of the stress marker genes Lsp5cs and Lslea and the gene Lsnced. By contrast, the addition of exogenous ABA decreased the content of ABA in shoots of AM plants and did not produce any further enhancement of the expression of these three genes. AM plants always exhibited higher values of root hydraulic conductivity and reduced transpiration rate under drought stress. From plants subjected to drought, only the AM plants recovered their root hydraulic conductivity completely after the 3 d recovery period. As a whole, the results indicate that AM plants regulate their ABA levels better and faster than non-AM plants, allowing a more adequate balance between leaf transpiration and root water movement during drought and recovery. PMID:18469324

  8. ESCRT-III assembly and cytokinetic abscission are induced by tension release in the intercellular bridge.

    PubMed

    Lafaurie-Janvore, Julie; Maiuri, Paolo; Wang, Irène; Pinot, Mathieu; Manneville, Jean-Baptiste; Betz, Timo; Balland, Martial; Piel, Matthieu

    2013-03-29

    The last step of cell division, cytokinesis, produces two daughter cells that remain connected by an intercellular bridge. This state often represents the longest stage of the division process. Severing the bridge (abscission) requires a well-described series of molecular events, but the trigger for abscission remains unknown. We found that pulling forces exerted by daughter cells on the intercellular bridge appear to regulate abscission. Counterintuitively, these forces prolonged connection, whereas a release of tension induced abscission. Tension release triggered the assembly of ESCRT-III (endosomal sorting complex required for transport-III), which was followed by membrane fission. This mechanism may allow daughter cells to remain connected until they have settled in their final locations, a process potentially important for tissue organization and morphogenesis.

  9. Allele-Specific Interactions between CAST AWAY and NEVERSHED Control Abscission in Arabidopsis Flowers.

    PubMed

    Groner, William D; Christy, Megan E; Kreiner, Catherine M; Liljegren, Sarah J

    2016-01-01

    An advantage of analyzing abscission in genetically tractable model plants is the ability to make use of classic genetic tools such as suppression analysis. We have investigated the regulation of organ abscission by carrying out suppression analysis in Arabidopsis flowers. Plants carrying mutations in the NEVERSHED (NEV) gene, which encodes an ADP-ribosylation factor GTPase-activating protein, retain their outer floral organs after fertilization. Mutant alleles of CAST AWAY (CST), which encodes a receptor-like cytoplasmic kinase, were found to restore organ abscission in nev flowers in an allele-specific manner. To further explore the basis of the interactions between CST and NEV, we tested whether the site of a nev mutation is predictive of its ability to be suppressed. Our results suggest instead that the strength of a nev allele influences whether organ abscission can be rescued by a specific allele of CST.

  10. Chlamydial infection induces host cytokinesis failure at abscission.

    PubMed

    Brown, Heather M; Knowlton, Andrea E; Grieshaber, Scott S

    2012-10-01

    Chlamydia trachomatis is an obligate intracellular bacteria and the infectious agent responsible for the sexually transmitted disease Chlamydia. Infection with Chlamydia can lead to serious health sequelae such as pelvic inflammatory disease and reproductive tract scarring contributing to infertility and ectopic pregnancies. Additionally, chlamydial infections have been epidemiologically linked to cervical cancer in patients with a prior human papilomavirus (HPV) infection. Chlamydial infection of cultured cells causes multinucleation, a potential pathway for chromosomal instability. Two mechanisms that are known to initiate multinucleation are cell fusion and cytokinesis failure. This study demonstrates that multinucleation of the host cell by Chlamydia is entirely due to cytokinesis failure. Moreover, cytokinesis failure is due in part to the chlamydial effector CPAF acting as an anaphase promoting complex mimic causing cells to exit mitosis with unaligned and unattached chromosomes. These lagging and missegregated chromosomes inhibit cytokinesis by blocking abscission, the final stage of cytokinesis.

  11. Chlamydial Infection Induces Host Cytokinesis Failure at Abscission

    PubMed Central

    Brown, Heather M.; Knowlton, Andrea E.; Grieshaber, Scott S.

    2012-01-01

    Chlamydia trachomatis is an obligate intracellular bacteria and the infectious agent responsible for the sexually transmitted disease Chlamydia. Infection with Chlamydia can lead to serious health sequelae such as pelvic inflammatory disease and reproductive tract scarring contributing to infertility and ectopic pregnancies. Additionally, chlamydial infections have been epidemiologically linked to cervical cancer in patients with a prior human papilomavirus (HPV) infection. Chlamydial infection of cultured cells causes multinucleation, a potential pathway for chromosomal instability. Two mechanisms that are known to initiate multinucleation are cell fusion and cytokinesis failure. This study demonstrates that multinucleation of the host cell by Chlamydia is entirely due to cytokinesis failure. Moreover, cytokinesis failure is due in part to the chlamydial effector CPAF acting as an anaphase promoting complex mimic causing cells to exit mitosis with unaligned and unattached chromosomes. These lagging and missegregated chromosomes inhibit cytokinesis by blocking abscission, the final stage of cytokinesis. PMID:22646503

  12. Isolation of ABA-responsive mutants in allohexaploid bread wheat (Triticum aestivum L.): Drawing connections to grain dormancy, preharvest sprouting, and drought tolerance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This paper describes the isolation of Wheat ABA-responsive mutants (Warm) in Chinese spring background of allohexaploid Triticum aestivum. The plant hormone abscisic acid (ABA) is required for the induction of seed dormancy, the induction of stomatal closure and drought tolerance, and is associated...

  13. ALIX and ESCRT-I/II function as parallel ESCRT-III recruiters in cytokinetic abscission.

    PubMed

    Christ, Liliane; Wenzel, Eva M; Liestøl, Knut; Raiborg, Camilla; Campsteijn, Coen; Stenmark, Harald

    2016-02-29

    Cytokinetic abscission, the final stage of cell division where the two daughter cells are separated, is mediated by the endosomal sorting complex required for transport (ESCRT) machinery. The ESCRT-III subunit CHMP4B is a key effector in abscission, whereas its paralogue, CHMP4C, is a component in the abscission checkpoint that delays abscission until chromatin is cleared from the intercellular bridge. How recruitment of these components is mediated during cytokinesis remains poorly understood, although the ESCRT-binding protein ALIX has been implicated. Here, we show that ESCRT-II and the ESCRT-II-binding ESCRT-III subunit CHMP6 cooperate with ESCRT-I to recruit CHMP4B, with ALIX providing a parallel recruitment arm. In contrast to CHMP4B, we find that recruitment of CHMP4C relies predominantly on ALIX. Accordingly, ALIX depletion leads to furrow regression in cells with chromosome bridges, a phenotype associated with abscission checkpoint signaling failure. Collectively, our work reveals a two-pronged recruitment of ESCRT-III to the cytokinetic bridge and implicates ALIX in abscission checkpoint signaling.

  14. ALIX and ESCRT-I/II function as parallel ESCRT-III recruiters in cytokinetic abscission

    PubMed Central

    Christ, Liliane; Wenzel, Eva M.; Liestøl, Knut; Raiborg, Camilla

    2016-01-01

    Cytokinetic abscission, the final stage of cell division where the two daughter cells are separated, is mediated by the endosomal sorting complex required for transport (ESCRT) machinery. The ESCRT-III subunit CHMP4B is a key effector in abscission, whereas its paralogue, CHMP4C, is a component in the abscission checkpoint that delays abscission until chromatin is cleared from the intercellular bridge. How recruitment of these components is mediated during cytokinesis remains poorly understood, although the ESCRT-binding protein ALIX has been implicated. Here, we show that ESCRT-II and the ESCRT-II–binding ESCRT-III subunit CHMP6 cooperate with ESCRT-I to recruit CHMP4B, with ALIX providing a parallel recruitment arm. In contrast to CHMP4B, we find that recruitment of CHMP4C relies predominantly on ALIX. Accordingly, ALIX depletion leads to furrow regression in cells with chromosome bridges, a phenotype associated with abscission checkpoint signaling failure. Collectively, our work reveals a two-pronged recruitment of ESCRT-III to the cytokinetic bridge and implicates ALIX in abscission checkpoint signaling. PMID:26929449

  15. Interplay between ABA and phospholipases A(2) and D in the response of citrus fruit to postharvest dehydration.

    PubMed

    Romero, Paco; Gandía, Mónica; Alférez, Fernando

    2013-09-01

    The interplay between abscisic acid (ABA) and phospholipases A2 and D (PLA2 and PLD) in the response of citrus fruit to water stress was investigated during postharvest by using an ABA-deficient mutant from 'Navelate' orange named 'Pinalate'. Fruit from both varieties harvested at two different maturation stages (mature-green and full-mature) were subjected to prolonged water loss inducing stem-end rind breakdown (SERB) in full-mature fruit. Treatment with PLA2 inhibitor aristolochic acid (AT) and PLD inhibitor lysophosphatidylethanolamine (LPE) reduced the disorder in both varieties, suggesting that phospholipid metabolism is involved in citrus peel quality. Expression of CsPLDα and CsPLDβ, and CssPLA2α and CssPLA2β was studied by real-time RT-PCR during water stress and in response to ABA. CsPLDα expression increased in mature-green fruit from 'Navelate' but not in 'Pinalate' and ABA did not counteract this effect. ABA enhanced repression of CsPLDα in full-mature fruit. CsPLDβ gene expression decreased in mature-green 'Pinalate', remained unchanged in 'Navelate' and was induced in full-mature fruit from both varieties. CssPLA2α expression increased in mature-green fruit from both varieties whereas in full-mature fruit only increased in 'Navelate'. CssPLA2β expression increased in mature-green flavedo from both varieties, but in full-mature fruit remained steady in 'Navelate' and barely increased in 'Pinalate' fruit. ABA reduced expression in both after prolonged storage. Responsiveness to ABA increased with maturation. Our results show interplay between PLA2 and PLD and suggest that ABA action is upstream phospholipase activation. Response to ABA during water stress in citrus is regulated during fruit maturation and involves membrane phospholipid degradation.

  16. Is the ABA concentration in the sap collected by pressurizing leaves relevant for analysing drought effects on stomata? Evidence from ABA-fed leaves of transgenic plants with modified capacities to synthesize ABA.

    PubMed

    Borel, Charlotte; Simonneau, Thierry

    2002-02-01

    Most studies on the role of ABA in the stomatal response of the whole plant to drought rely on a good estimate of ABA concentration in xylem sap. In this report, varying volumes of sap (V(sap)) were collected by pressurizing leaves cut from several lines of N. plumbaginifolia with modified capacities to synthesize ABA. Leaves were fed with solutions of known ABA concentration ([ABA](solution) from 0-500 micromol m(-3)) for 2-3 h before sap collection. ABA concentration in extruded sap ([ABA](sap)) was compared with [ABA](solution). In low-volume extracts (less than 0.35 mm(3) cm(-2) leaf area) collected from leaves of well-watered plants, [ABA](sap) was close to [ABA](solution). For all lines, [ABA](sap) decreased with increasing V(sap). The same dilution effect was observed for leaves pressurized just after sampling on droughted plants, suggesting, as for detached leaves fed with ABA, that [ABA](sap) in low-volume extracts approximated well with the concentration of ABA entering leaves still attached on droughted plants. However, ABA-fed leaves sampled from droughted plants yielded higher [ABA](sap) than ABA-fed leaves sampled from well-watered plants. [ABA](sap) was also increased, although very slightly, when leaves were preincubated in highly enriched ABA solution. This indicates that some leaf ABA contributed to the ABA concentration returned in the extruded sap. Consistently, [ABA](sap) in medium-volume extracts (0.35-0.65 mm(3) cm(-2) leaf area) was lower for leaves sampled on under-producing lines than on the wild type. Despite these distortions between [ABA](solution) and [ABA](sap) in medium-volume extracts, stomatal conductance of ABA-fed leaves closely correlated with [ABA](sap) with a similar relationship in all cases, whilst relationships with [ABA](solution) were more scattered.

  17. Function of the HD-Zip I gene Oshox22 in ABA-mediated drought and salt tolerances in rice.

    PubMed

    Zhang, Shuxin; Haider, Imran; Kohlen, Wouter; Jiang, Li; Bouwmeester, Harro; Meijer, Annemarie H; Schluepmann, Henriette; Liu, Chun-Ming; Ouwerkerk, Pieter B F

    2012-12-01

    Oshox22 belongs to the homeodomain-leucine zipper (HD-Zip) family I of transcription factors, most of which have unknown functions. Here we show that the expression of Oshox22 is strongly induced by salt stress, abscisic acid (ABA), and polyethylene glycol treatment (PEG), and weakly by cold stress. Trans-activation assays in yeast and transient expression analyses in rice protoplasts demonstrated that Oshox22 is able to bind the CAAT(G/C)ATTG element and acts as a transcriptional activator that requires both the HD and Zip domains. Rice plants homozygous for a T-DNA insertion in the promoter region of Oshox22 showed reduced Oshox22 expression and ABA content, decreased sensitivity to ABA, and enhanced tolerance to drought and salt stresses at the seedling stage. In contrast, transgenic rice over-expressing Oshox22 showed increased sensitivity to ABA, increased ABA content, and decreased drought and salt tolerances. Based on these results, we conclude that Oshox22 affects ABA biosynthesis and regulates drought and salt responses through ABA-mediated signal transduction pathways.

  18. Linking Turgor with ABA Biosynthesis: Implications for Stomatal Responses to Vapor Pressure Deficit across Land Plants1[OPEN

    PubMed Central

    McAdam, Scott A.M.; Brodribb, Timothy J.

    2016-01-01

    Stomatal responses to changes in vapor pressure deficit (VPD) constitute the predominant form of daytime gas-exchange regulation in plants. Stomatal closure in response to increased VPD is driven by the rapid up-regulation of foliar abscisic acid (ABA) biosynthesis and ABA levels in angiosperms; however, very little is known about the physiological trigger for this increase in ABA biosynthesis at increased VPD. Using a novel method of modifying leaf cell turgor by the application of external pressures, we test whether changes in turgor pressure can trigger increases in foliar ABA levels over 20 min, a period of time most relevant to the stomatal response to VPD. We found in angiosperm species that the biosynthesis of ABA was triggered by reductions in leaf turgor, and in two species tested, that a higher sensitivity of ABA synthesis to leaf turgor corresponded with a higher stomatal sensitivity to VPD. In contrast, representative species from nonflowering plant lineages did not show a rapid turgor-triggered increase in foliar ABA levels, which is consistent with previous studies demonstrating passive stomatal responses to changes in VPD in these lineages. Our method provides a new tool for characterizing the response of stomata to water availability. PMID:27208264

  19. The effect of light on ABA catabolism in excised seedlings of Phaseolus vulgaris L. cv. top-crop

    SciTech Connect

    Cowan, A.K.; Myemane, D.M. )

    1990-05-01

    Studies on the influence of light quality on ABA catabolism have implicated the involvement of phytochrome in this process. Detailed experiments were therefore carried out to determine whether light could be a factor involved in the regulation of ABA catabolism in higher plants. Excised, etiolated seedlings of Phaseolus vulgaris (4.5g fr. wt.) were supplied with (R,S,)-(2-{sup 14}C)-ABA (5.0 kBq) and exposed to various combinations of red (37 {mu}mol m{sup {minus}2} s{sup {minus}1}) and far-red (23 {mu}mol m{sup {minus}2} s{sup {minus}1}) light. Following light treatments seedlings were returned to darkness for the remainder of the 20 h incubation period. Far-red light illumination stimulated ABA catabolism whereas red light had no significant effect on this process. Kinetic studies and analysis of water-soluble conjugates revealed that far-red light treatment enhanced the sequestration of ABA and its acidic products. The apparent inhibition of ABA catabolism by red light was relieved, if red light irradiation was followed immediately by a dose of far-red light. Thus, these data indicate that ABA catabolism might be mediated by phytochrome and that control is exerted at the level of conjugation rather than oxidation.

  20. Opposing Activities of Aurora B Kinase and B56-PP2A Phosphatase on MKlp2 Determine Abscission Timing.

    PubMed

    Fung, Suet Yin Sarah; Kitagawa, Mayumi; Liao, Pei-Ju; Wong, Jasmine; Lee, Sang Hyun

    2017-01-09

    After cleavage furrow ingression during cytokinesis, nascent daughter cells remain connected by an intercellular bridge (ICB) and the midbody [1, 2]. The midbody becomes an assembly platform for ESCRT complexes that split apart the plasma membrane (PM) anchored to the ICB and complete abscission, which is the final step of cell division [3-5]. Aurora B governs abscission by regulating its timing as a checkpoint [6-10]. However, the underlying mechanisms for this process remain unknown. Here, we reveal the mechanism controlling abscission through integration of Aurora B kinase and B56-bound PP2A phosphatase activities on the kinesin motor protein MKlp2. We identify MKlp2 as an essential protein for promoting abscission, which may regulate tethering and stabilizing of the PM to the microtubule cytoskeleton at the ICB through its previously uncharacterized lipid association motif (LAM). MKlp2 recruits Aurora B to the ICB [11-15]. In turn, Aurora B phosphorylation of MKlp2 S878 in the LAM is a key inhibitory signal for abscission. Conversely, B56-PP2A promotes abscission by opposing Aurora B phosphorylation of MKlp2 S878. Strikingly, a phospho-resistant MKlp2 S878A mutant overcomes Aurora-B-mediated abscission blockade. Thus, abscission is determined by the balance of Aurora B and B56-PP2A activities on MKlp2 S878 within the LAM. Together, these findings establish a key mechanism for Aurora B regulation of abscission in mammalian cells.

  1. Transcriptome Analysis of Soybean Leaf Abscission Identifies Transcriptional Regulators of Organ Polarity and Cell Fate

    PubMed Central

    Kim, Joonyup; Yang, Jinyoung; Yang, Ronghui; Sicher, Richard C.; Chang, Caren; Tucker, Mark L.

    2016-01-01

    Abscission, organ separation, is a developmental process that is modulated by endogenous and environmental factors. To better understand the molecular events underlying the progression of abscission in soybean, an agriculturally important legume, we performed RNA sequencing (RNA-seq) of RNA isolated from the leaf abscission zones (LAZ) and petioles (Non-AZ, NAZ) after treating stem/petiole explants with ethylene for 0, 12, 24, 48, and 72 h. As expected, expression of several families of cell wall modifying enzymes and many pathogenesis-related (PR) genes specifically increased in the LAZ as abscission progressed. Here, we focus on the 5,206 soybean genes we identified as encoding transcription factors (TFs). Of the 5,206 TFs, 1,088 were differentially up- or down-regulated more than eight-fold in the LAZ over time, and, within this group, 188 of the TFs were differentially regulated more than eight-fold in the LAZ relative to the NAZ. These 188 abscission-specific TFs include several TFs containing domains for homeobox, MYB, Zinc finger, bHLH, AP2, NAC, WRKY, YABBY, and auxin-related motifs. To discover the connectivity among the TFs and highlight developmental processes that support organ separation, the 188 abscission-specific TFs were then clustered based on a >four-fold up- or down-regulation in two consecutive time points (i.e., 0 and 12 h, 12 and 24 h, 24 and 48 h, or 48 and 72 h). By requiring a sustained change in expression over two consecutive time intervals and not just one or several time intervals, we could better tie changes in TFs to a particular process or phase of abscission. The greatest number of TFs clustered into the 0 and 12 h group. Transcriptional network analysis for these abscission-specific TFs indicated that most of these TFs are known as key determinants in the maintenance of organ polarity, lateral organ growth, and cell fate. The abscission-specific expression of these TFs prior to the onset of abscission and their functional

  2. Transcriptome Analysis of Soybean Leaf Abscission Identifies Transcriptional Regulators of Organ Polarity and Cell Fate.

    PubMed

    Kim, Joonyup; Yang, Jinyoung; Yang, Ronghui; Sicher, Richard C; Chang, Caren; Tucker, Mark L

    2016-01-01

    Abscission, organ separation, is a developmental process that is modulated by endogenous and environmental factors. To better understand the molecular events underlying the progression of abscission in soybean, an agriculturally important legume, we performed RNA sequencing (RNA-seq) of RNA isolated from the leaf abscission zones (LAZ) and petioles (Non-AZ, NAZ) after treating stem/petiole explants with ethylene for 0, 12, 24, 48, and 72 h. As expected, expression of several families of cell wall modifying enzymes and many pathogenesis-related (PR) genes specifically increased in the LAZ as abscission progressed. Here, we focus on the 5,206 soybean genes we identified as encoding transcription factors (TFs). Of the 5,206 TFs, 1,088 were differentially up- or down-regulated more than eight-fold in the LAZ over time, and, within this group, 188 of the TFs were differentially regulated more than eight-fold in the LAZ relative to the NAZ. These 188 abscission-specific TFs include several TFs containing domains for homeobox, MYB, Zinc finger, bHLH, AP2, NAC, WRKY, YABBY, and auxin-related motifs. To discover the connectivity among the TFs and highlight developmental processes that support organ separation, the 188 abscission-specific TFs were then clustered based on a >four-fold up- or down-regulation in two consecutive time points (i.e., 0 and 12 h, 12 and 24 h, 24 and 48 h, or 48 and 72 h). By requiring a sustained change in expression over two consecutive time intervals and not just one or several time intervals, we could better tie changes in TFs to a particular process or phase of abscission. The greatest number of TFs clustered into the 0 and 12 h group. Transcriptional network analysis for these abscission-specific TFs indicated that most of these TFs are known as key determinants in the maintenance of organ polarity, lateral organ growth, and cell fate. The abscission-specific expression of these TFs prior to the onset of abscission and their functional

  3. Effects of ABA and CaCl₂ on GABA accumulation in fava bean germinating under hypoxia-NaCl stress.

    PubMed

    Yang, Runqiang; Hui, Qianru; Gu, Zhenxin

    2016-01-01

    Effects of exogenous abscisic acid (ABA) and CaCl2 on γ-aminobutyric acid (GABA) accumulation of germinated fava bean under hypoxia-NaCl stress were investigated. Exogenous ABA resulted in the enhancement of glutamate decarboxylase (GAD) and diamine oxidase (DAO) activity as well as GABA content in cotyledon and shoot. CaCl2 increased both enzyme activities in shoot and GABA content in cotyledon and shoot. ABA downregulated GAD expression in cotyledon and radicle, while upregulated that in shoot; it also upregulated DAO expression in each organ. CaCl2 upregulated GAD expression in cotyledon, while downregulated that in radicle. However, it upregulated DAO expression in shoot, downregulated that in radicle. ABA inhibitor fluridon and ethylenediaminetetraacetic acid inhibited GAD and DAO activities significantly so that inhibited GABA accumulation through reducing ABA biosynthesis and chelating Ca(2+), respectively. However, they upregulated GAD and DAO expression in varying degrees. These results indicate that ABA and Ca(2+) participate in GABA biosynthesis in fava bean during germination under hypoxia-NaCl stress.

  4. Proteomic analysis of the effects of ABA treatments on ripening Vitis vinifera berries

    PubMed Central

    Giribaldi, Marzia; Gény, Laurence; Delrot, Serge; Schubert, Andrea

    2010-01-01

    The control of ripening of the non-climacteric grapevine fruit is still a matter of debate, but several lines of evidence point to an important role for the hormone abscisic acid (ABA). The effects of ABA treatments on Cabernet Sauvignon berries before and at véraison were studied using a 2-DE proteomic approach. Proteins from whole deseeded berries (before véraison) and berry flesh and skin (at véraison) treated with 0.76 mM ABA and collected 24 h after treatment were separated and analysed. A total of 60 protein spots showed significant variations between treated and control berries, and 40 proteins, mainly related to general metabolism and cell defence, were identified by LC MS/MS. Our results show that ABA acts mainly through the regulation of mostly the same proteins which are involved in the ripening process, and that several of these changes share common elements with the ABA-induced responses in vegetative tissues. PMID:20388747

  5. Grafting cucumber onto luffa improves drought tolerance by increasing ABA biosynthesis and sensitivity

    PubMed Central

    Liu, Shanshan; Li, Hao; Lv, Xiangzhang; Ahammed, Golam Jalal; Xia, Xiaojian; Zhou, Jie; Shi, Kai; Asami, Tadao; Yu, Jingquan; Zhou, Yanhong

    2016-01-01

    Balancing stomata-dependent CO2 assimilation and transpiration is a key challenge for increasing crop productivity and water use efficiency under drought stress for sustainable crop production worldwide. Here, we show that cucumber and luffa plants with luffa as rootstock have intrinsically increased water use efficiency, decreased transpiration rate and less affected CO2 assimilation capacity following drought stress over those with cucumber as rootstock. Drought accelerated abscisic acid (ABA) accumulation in roots, xylem sap and leaves, and induced the transcript of ABA signaling genes, leading to a decreased stomatal aperture and transpiration in the plants grafted onto luffa roots as compared to plants grafted onto cucumber roots. Furthermore, stomatal movement in the plants grafted onto luffa roots had an increased sensitivity to ABA. Inhibition of ABA biosynthesis in luffa roots decreased the drought tolerance in cucumber and luffa plants. Our study demonstrates that the roots of luffa have developed an enhanced ability to sense the changes in root-zone moisture and could eventually deliver modest level of ABA from roots to shoots that enhances water use efficiency under drought stress. Such a mechanism could be greatly exploited to benefit the agricultural production especially in arid and semi-arid areas. PMID:26832070

  6. Characterization of the ABA-regulated global responses to dehydration in Arabidopsis by metabolomics.

    PubMed

    Urano, Kaoru; Maruyama, Kyonoshin; Ogata, Yoshiyuki; Morishita, Yoshihiko; Takeda, Migiwa; Sakurai, Nozomu; Suzuki, Hideyuki; Saito, Kazuki; Shibata, Daisuke; Kobayashi, Masatomo; Yamaguchi-Shinozaki, Kazuko; Shinozaki, Kazuo

    2009-03-01

    Drought is the major environmental threat to agricultural production and distribution worldwide. Adaptation by plants to dehydration stress is a complex biological process that involves global changes in gene expression and metabolite composition. Here, using one type of functional genomics analysis, metabolomics, we characterized the metabolic phenotypes of Arabidopsis wild-type and a knockout mutant of the NCED3 gene (nc3-2) under dehydration stress. NCED3 plays a role in the dehydration-inducible biosynthesis of abscisic acid (ABA), a phytohormone that is important in the dehydration-stress response in higher plants. Metabolite profiling performed using two types of mass spectrometry (MS) systems, gas chromatography/time-of-flight MS (GC/TOF-MS) and capillary electrophoresis MS (CE-MS), revealed that accumulation of amino acids depended on ABA production, but the level of the oligosaccharide raffinose was regulated by ABA independently under dehydration stress. Metabolic network analysis showed that global metabolite-metabolite correlations occurred in dehydration-increased amino acids in wild-type, and strong correlations with raffinose were reconstructed in nc3-2. An integrated metabolome and transcriptome analysis revealed ABA-dependent transcriptional regulation of the biosynthesis of the branched-chain amino acids, saccharopine, proline and polyamine. This metabolomics analysis revealed new molecular mechanisms of dynamic metabolic networks in response to dehydration stress.

  7. Implications of nonrandom seed abscission and global stilling for migration of wind-dispersed plant species.

    PubMed

    Thompson, Sally E; Katul, Gabriel G

    2013-06-01

    Migration of plant populations is a potential survival response to climate change that depends critically on seed dispersal. Biological and physical factors determine dispersal and migration of wind-dispersed species. Recent field and wind tunnel studies demonstrate biological adaptations that bias seed release toward conditions of higher wind velocity, promoting longer dispersal distances and faster migration. However, another suite of international studies also recently highlighted a global decrease in near-surface wind speeds, or 'global stilling'. This study assessed the implications of both factors on potential plant population migration rates, using a mechanistic modeling framework. Nonrandom abscission was investigated using models of three seed release mechanisms: (i) a simple drag model; (ii) a seed deflection model; and (iii) a 'wear and tear' model. The models generated a single functional relationship between the frequency of seed release and statistics of the near-surface wind environment, independent of the abscission mechanism. An Inertial-Particle, Coupled Eulerian-Lagrangian Closure model (IP-CELC) was used to investigate abscission effects on seed dispersal kernels and plant population migration rates under contemporary and potential future wind conditions (based on reported global stilling trends). The results confirm that nonrandom seed abscission increased dispersal distances, particularly for light seeds. The increases were mitigated by two physical feedbacks: (i) although nonrandom abscission increased the initial acceleration of seeds from rest, the sensitivity of the seed dispersal to this initial condition declined as the wind speed increased; and (ii) while nonrandom abscission increased the mean dispersal length, it reduced the kurtosis of seasonal dispersal kernels, and thus the chance of long-distance dispersal. Wind stilling greatly reduced the modeled migration rates under biased seed release conditions. Thus, species that require

  8. Post-pruning shoot growth increases fruit abscission and reduces stem carbohydrates and yield in macadamia

    PubMed Central

    McFadyen, Lisa M.; Robertson, David; Sedgley, Margaret; Kristiansen, Paul; Olesen, Trevor

    2011-01-01

    Background and Aims There is good evidence for deciduous trees that competition for carbohydrates from shoot growth accentuates early fruit abscission and reduces yield but the effect for evergreen trees is not well defined. Here, whole-tree tip-pruning at anthesis is used to examine the effect of post-pruning shoot development on fruit abscission in the evergreen subtropical tree macadamia (Macadamia integrifolia, M. integrifolia × tetraphylla). Partial-tree tip-pruning is also used to test the localization of the effect. Methods In the first experiment (2005/2006), all branches on trees were tip-pruned at anthesis, some trees were allowed to re-shoot (R treatment) and shoots were removed from others (NR treatment). Fruit set and stem total non-structural carbohydrates (TNSC) over time, and yield were measured. In the second experiment (2006/2007), upper branches of trees were tip-pruned at anthesis, some trees were allowed to re-shoot (R) and shoots were removed from others (NR). Fruit set and yield were measured separately for upper (pruned) and lower (unpruned) branches. Key Results In the first experiment, R trees set far fewer fruit and had lower yield than NR trees. TNSC fell and rose in all treatments but the decline in R trees occurred earlier than in NR trees and coincided with early shoot growth and the increase in fruit abscission relative to the other treatments. In the second experiment, fruit abscission on upper branches of R trees increased relative to the other treatments but there was little difference in fruit abscission between treatments on lower branches. Conclusions This study is the first to demonstrate an increase in fruit abscission in an evergreen tree in response to pruning. The effect appeared to be related to competition for carbohydrates between post-pruning shoot growth and fruit development and was local, with shoot growth on pruned branches having no effect on fruit abscission on unpruned branches. PMID:21325025

  9. Ethylene: role in fruit abscission and dehiscence processes.

    PubMed

    Lipe, J A; Morgan, P W

    1972-12-01

    Two peaks of ethylene production occur during the development of cotton fruitz (Gossypium hirsutum L.). These periods precede the occurrence of young fruit shedding and mature fruit dehiscence, both of which are abscission phenomena and the latter is generally assumed to be part of the total ripening process. Detailed study of the dehiscence process revealed that ethylene production of individual, attached cotton fruits goes through a rising, cyclic pattern which reaches a maximum prior to dehiscence. With detached pecan fruits (Carya illinoensis [Wang.] K. Koch), ethylene production measured on alternate days rose above 1 microliter per kilogram fresh weight per hour before dehiscence began and reached a peak several days prior to complete dehiscence. Ethylene production by cotton and pecan fruits was measured just prior to dehiscence and then the internal concentration of the gas near the center of the fruit was determined. From these data a ratio of production rate to internal concentration was determined which allowed calculation of the approximate ethylene concentration in the intact fruit prior to dehiscence and selection of appropriate levels to apply to fruits. Ethylene at 10 microliters per liter of air appears to saturate dehiscence of cotton, pecan, and okra (Hibiscus esculentus L.) fruits and the process is completed in 3 to 4 days. In all cases some hastening of dehiscence was observed with as little as 0.1 microliter of exogenous ethylene per liter of air. The time required for response to different levels of ethylene was determined and compared to the time course of ethylene production and dehiscence. We concluded that internal levels of ethylene rose to dehiscence-stimulating levels a sufficience time before dehiscence for the gas to have initiated the process. Since our data and calculations indicate that enough ethylene is made a sufficient time before dehiscence, to account for the process, we propose that ethylene is one of the regulators of

  10. Ethylene: Role in Fruit Abscission and Dehiscence Processes 12

    PubMed Central

    Lipe, John A.; Morgan, Page W.

    1972-01-01

    Two peaks of ethylene production occur during the development of cotton fruitz (Gossypium hirsutum L.). These periods precede the occurrence of young fruit shedding and mature fruit dehiscence, both of which are abscission phenomena and the latter is generally assumed to be part of the total ripening process. Detailed study of the dehiscence process revealed that ethylene production of individual, attached cotton fruits goes through a rising, cyclic pattern which reaches a maximum prior to dehiscence. With detached pecan fruits (Carya illinoensis [Wang.] K. Koch), ethylene production measured on alternate days rose above 1 microliter per kilogram fresh weight per hour before dehiscence began and reached a peak several days prior to complete dehiscence. Ethylene production by cotton and pecan fruits was measured just prior to dehiscence and then the internal concentration of the gas near the center of the fruit was determined. From these data a ratio of production rate to internal concentration was determined which allowed calculation of the approximate ethylene concentration in the intact fruit prior to dehiscence and selection of appropriate levels to apply to fruits. Ethylene at 10 microliters per liter of air appears to saturate dehiscence of cotton, pecan, and okra (Hibiscus esculentus L.) fruits and the process is completed in 3 to 4 days. In all cases some hastening of dehiscence was observed with as little as 0.1 microliter of exogenous ethylene per liter of air. The time required for response to different levels of ethylene was determined and compared to the time course of ethylene production and dehiscence. We concluded that internal levels of ethylene rose to dehiscence-stimulating levels a sufficience time before dehiscence for the gas to have initiated the process. Since our data and calculations indicate that enough ethylene is made a sufficient time before dehiscence, to account for the process, we propose that ethylene is one of the regulators of

  11. Comparative transcriptional survey between laser-microdissected cells from laminar abscission zone and petiolar cortical tissue during ethylene-promoted abscission in citrus leaves

    PubMed Central

    Agustí, Javier; Merelo, Paz; Cercós, Manuel; Tadeo, Francisco R; Talón, Manuel

    2009-01-01

    Background Abscission is the cell separation process by which plants are able to shed organs. It has a great impact on the yield of most crop plants. At the same time, the process itself also constitutes an excellent model to study cell separation processes, since it occurs in concrete areas known as abscission zones (AZs) which are composed of a specific cell type. However, molecular approaches are generally hampered by the limited area and cell number constituting the AZ. Therefore, detailed studies at the resolution of cell type are of great relevance in order to accurately describe the process and to identify potential candidate genes for biotechnological applications. Results Efficient protocols for the isolation of specific citrus cell types, namely laminar abscission zone (LAZ) and petiolar cortical (Pet) cells based on laser capture microdissection (LCM) and for RNA microextraction and amplification have been developed. A comparative transcriptome analysis between LAZ and Pet from citrus leaf explants subjected to an in-vitro 24 h ethylene treatment was performed utilising microarray hybridization and analysis. Our analyses of gene functional classes differentially represented in ethylene-treated LAZ revealed an activation program dominated by the expression of genes associated with protein synthesis, protein fate, cell type differentiation, development and transcription. The extensive repertoire of genes associated with cell wall biosynthesis and metabolism strongly suggests that LAZ layers activate both catabolic and anabolic wall modification pathways during the abscission program. In addition, over-representation of particular members of different transcription factor families suggests important roles for these genes in the differentiation of the effective cell separation layer within the many layers contained in the citrus LAZ. Preferential expression of stress-related and defensive genes in Pet reveals that this tissue is likely to be reprogrammed to

  12. Evolutionary Conservation of ABA Signaling for Stomatal Closure in Ferns.

    PubMed

    Cai, Shengguan; Chen, Guang; Wang, Yuanyuan; Huang, Yuqing; Marchant, Blaine; Wang, Yizhou; Yang, Qian; Dai, Fei; Hills, Adrian; Franks, Peter J; Nevo, Eviatar; Soltis, Doug; Soltis, Pamela; Sessa, Emily; Wolf, Paul G; Xue, Dawei; Zhang, Guoping; Pogson, Barry J; Blatt, Mike R; Chen, Zhong-Hua

    2017-02-23

    ABA-driven stomatal regulation reportedly evolved after the divergence of ferns, during the early evolution of seed plants approximately 360 Mya. This hypothesis is based on the observation that the stomata of certain fern species are unresponsive to ABA, but exhibit passive hydraulic control. However, ABA-induced stomatal closure was detected in some mosses and lycophytes. Here, we observed that a number of ABA signaling and membrane transporter protein families diversified over the evolutionary history of land plants. The aquatic ferns Azolla filiculoides and Salvinia cucullata have representatives of 23 families of proteins orthologous to those of Arabidopsis thaliana and all other land plant species studied. Phylogenetic analysis of the key ABA signaling proteins indicates an evolutionarily conserved stomatal response to ABA. Moreover, comparative transcriptomic analysis has identified a suite of ABA responsive genes that differentially expressed in a terrestrial fern species, Polystichum proliferum. These genes encode proteins associated with ABA biosynthesis, transport, reception, transcription, signaling, and ion and sugar transport, which fit the general ABA signaling pathway constructed from Arabidopsis thaliana and Hordeum vulgare. The retention of these key ABA-responsive genes could have had a profound effect on the adaptation of ferns to dry conditions. Furthermore, stomatal assays have shown the primary evidence for ABA-induced closure of stomata in two terrestrial fern species P. proliferum and Nephrolepis exaltata. In summary, we report new molecular and physiological evidence for the presence of active stomatal control in ferns.

  13. Computational model of cytokinetic abscission driven by ESCRT-III polymerization and remodeling.

    PubMed

    Elia, Natalie; Fabrikant, Gur; Kozlov, Michael M; Lippincott-Schwartz, Jennifer

    2012-05-16

    The endosomal sorting complex required for transport (ESCRT)-III complex, capable of polymerization and remodeling, participates in abscission of the intercellular membrane bridge connecting two daughter cells at the end of cytokinesis. Here, we integrate quantitative imaging of ESCRT-III during cytokinetic abscission with biophysical properties of ESCRT-III complexes to formulate and test a computational model for ESCRT-mediated cytokinetic abscission. We propose that cytokinetic abscission is driven by an ESCRT-III fission complex, which arises from ESCRT-III polymerization at the edge of the cytokinetic midbody structure, located at the center of the intercellular bridge. Formation of the fission complex is completed by remodeling and breakage of the ESCRT-III polymer assisted by VPS4. Subsequent spontaneous constriction of the fission complex generates bending deformation of the intercellular bridge membrane. The related membrane elastic force propels the fission complex along the intercellular bridge away from the midbody until it reaches an equilibrium position, determining the scission site. Membrane attachment to the dome-like end-cap of the fission complex drives membrane fission, completing the abscission process. We substantiate the model by theoretical analysis of the membrane elastic energy and by experimental verification of the major model assumptions.

  14. Optically Pure Abscisic Acid Analogs—Tools for Relating Germination Inhibition and Gene Expression in Wheat Embryos 1

    PubMed Central

    Walker-Simmons, M. K.; Anderberg, Robert J.; Rose, Patricia A.; Abrams, Suzanne R.

    1992-01-01

    We report an examination of the structural requirements of the abscisic acid (ABA) recognition response in wheat dormant seed embryos using optically pure isomers of ABA analogs. These compounds include permutations to the ABA structure with either an acetylene or a trans bond at C-4 C-5, and either a single or double bond at the C-2′ C-3′ double bond. (R)-ABA and the three isomers with the same configuration at C-1′ as natural ABA were found to be effective germination inhibitors. The biologically active ABA analogs exhibited differential effects on ABA-responsive gene expression. All the ABA analogs that inhibited germination induced two ABA-responsive genes, wheat group 3 lea and dhn (rab). However, (R)-ABA and (S)-dihydroABA were less effective in inducing the ABA-responsive gene Em within the time that embryonic germination was inhibited. ImagesFigure 3Figure 4 PMID:16668914

  15. Sensitivity of Stomata to Abscisic Acid (An Effect of the Mesophyll).

    PubMed Central

    Trejo, C. L.; Davies, W. J.; Ruiz, LdMP.

    1993-01-01

    The effects of added abscisic acid (ABA) on the stomatal behavior of Commelina communis L. were tested using three different systems. ABA was applied to isolated epidermis or to leaf pieces incubated in the light in bathing solutions perfused with CO2-free air. ABA was also fed to detached leaves in a transpiration bioassay. The apparent sensitivity of stomata to ABA was highly dependent on the method used to feed ABA. Stomata of isolated epidermis were apparently most sensitive to ABA, such that a concentration of 1 [mu]M caused almost complete stomatal closure. When pieces of whole leaves were floated on solutions of ABA of the same concentration, the stomata were almost completely open. The same concentration of ABA fed through the midrib of transpiring detached leaves caused an intermediate response. These differences in stomatal sensitivity to added ABA were found to be a function of differences in the ABA concentration in the epidermes. Comparison of the three application systems suggested that, when leaf pieces were incubated in ABA or fed with ABA through the midrib, accumulation of ABA in the epidermes was limited by the presence of the mesophyll. Even bare mesophyll incubated in ABA solution did not accumulate ABA. Accumulation of radioactivity by leaf pieces floated on [3H]ABA confirmed ABA uptake in this system. Experiments with tetcyclacis, an inhibitor of phaseic acid formation, suggested that rapid metabolism of ABA in mesophyll can have a controlling influence on ABA concentration in both the mesophyll and the epidermis. Inhibition of ABA catabolism with tetcyclacis allows ABA accumulation and increases the apparent sensitivity of stomata to applied ABA. The results are discussed in the context of an important role for ABA metabolism in the regulation of stomatal behavior. PMID:12231838

  16. ABA Inducible Rice Protein Phosphatase 2C Confers ABA Insensitivity and Abiotic Stress Tolerance in Arabidopsis

    PubMed Central

    Singh, Amarjeet; Jha, Saroj K.; Bagri, Jayram; Pandey, Girdhar K.

    2015-01-01

    Arabidopsis PP2C belonging to group A have been extensively worked out and known to negatively regulate ABA signaling. However, rice (Oryza sativa) orthologs of Arabidopsis group A PP2C are scarcely characterized functionally. We have identified a group A PP2C from rice (OsPP108), which is highly inducible under ABA, salt and drought stresses and localized predominantly in the nucleus. Genetic analysis revealed that Arabidopsis plants overexpressing OsPP108 are highly insensitive to ABA and tolerant to high salt and mannitol stresses during seed germination, root growth and overall seedling growth. At adult stage, OsPP108 overexpression leads to high tolerance to salt, mannitol and drought stresses with far better physiological parameters such as water loss, fresh weight, chlorophyll content and photosynthetic potential (Fv/Fm) in transgenic Arabidopsis plants. Expression profile of various stress marker genes in OsPP108 overexpressing plants revealed interplay of ABA dependent and independent pathway for abiotic stress tolerance. Overall, this study has identified a potential rice group A PP2C, which regulates ABA signaling negatively and abiotic stress signaling positively. Transgenic rice plants overexpressing this gene might provide an answer to the problem of low crop yield and productivity during adverse environmental conditions. PMID:25886365

  17. ABA inducible rice protein phosphatase 2C confers ABA insensitivity and abiotic stress tolerance in Arabidopsis.

    PubMed

    Singh, Amarjeet; Jha, Saroj K; Bagri, Jayram; Pandey, Girdhar K

    2015-01-01

    Arabidopsis PP2C belonging to group A have been extensively worked out and known to negatively regulate ABA signaling. However, rice (Oryza sativa) orthologs of Arabidopsis group A PP2C are scarcely characterized functionally. We have identified a group A PP2C from rice (OsPP108), which is highly inducible under ABA, salt and drought stresses and localized predominantly in the nucleus. Genetic analysis revealed that Arabidopsis plants overexpressing OsPP108 are highly insensitive to ABA and tolerant to high salt and mannitol stresses during seed germination, root growth and overall seedling growth. At adult stage, OsPP108 overexpression leads to high tolerance to salt, mannitol and drought stresses with far better physiological parameters such as water loss, fresh weight, chlorophyll content and photosynthetic potential (Fv/Fm) in transgenic Arabidopsis plants. Expression profile of various stress marker genes in OsPP108 overexpressing plants revealed interplay of ABA dependent and independent pathway for abiotic stress tolerance. Overall, this study has identified a potential rice group A PP2C, which regulates ABA signaling negatively and abiotic stress signaling positively. Transgenic rice plants overexpressing this gene might provide an answer to the problem of low crop yield and productivity during adverse environmental conditions.

  18. A Role for Arabidopsis miR399f in Salt, Drought, and ABA Signaling

    PubMed Central

    Baek, Dongwon; Chun, Hyun Jin; Kang, Songhwa; Shin, Gilok; Park, Su Jung; Hong, Hyewon; Kim, Chanmin; Kim, Doh Hoon; Lee, Sang Yeol; Kim, Min Chul; Yun, Dae-Jin

    2016-01-01

    MiR399f plays a crucial role in maintaining phosphate homeostasis in Arabidopsis thaliana. Under phosphate starvation conditions, AtMYB2, which plays a role in plant salt and drought stress responses, directly regulates the expression of miR399f. In this study, we found that miR399f also participates in plant responses to abscisic acid (ABA), and to abiotic stresses including salt and drought. Salt and ABA treatment induced the expression of miR399f, as confirmed by histochemical analysis of promoter-GUS fusions. Transgenic Arabidopsis plants overexpressing miR399f (miR399f-OE) exhibited enhanced tolerance to salt stress and exogenous ABA, but hypersensitivity to drought. Our in silico analysis identified ABF3 and CSP41b as putative target genes of miR399f, and expression analysis revealed that mRNA levels of ABF3 and CSP41b decreased remarkably in miR399f-OE plants under salt stress and in response to treatment with ABA. Moreover, we showed that activation of stress-responsive gene expression in response to salt stress and ABA treatment was impaired in miR399f-OE plants. Thus, these results suggested that in addition to phosphate starvation signaling, miR399f might also modulates plant responses to salt, ABA, and drought, by regulating the expression of newly discovered target genes such as ABF3 and CSP41b. PMID:26674968

  19. A NAP-AAO3 regulatory module promotes chlorophyll degradation via ABA biosynthesis in Arabidopsis leaves.

    PubMed

    Yang, Jiading; Worley, Eric; Udvardi, Michael

    2014-12-01

    Chlorophyll degradation is an important part of leaf senescence, but the underlying regulatory mechanisms are largely unknown. Excised leaves of an Arabidopsis thaliana NAC-LIKE, ACTIVATED BY AP3/PI (NAP) transcription factor mutant (nap) exhibited lower transcript levels of known chlorophyll degradation genes, STAY-GREEN1 (SGR1), NON-YELLOW COLORING1 (NYC1), PHEOPHYTINASE (PPH), and PHEIDE a OXYGENASE (PaO), and higher chlorophyll retention than the wild type during dark-induced senescence. Transcriptome coexpression analysis revealed that abscisic acid (ABA) metabolism/signaling genes were disproportionately represented among those positively correlated with NAP expression. ABA levels were abnormally low in nap leaves during extended darkness. The ABA biosynthetic genes 9-CIS-EPOXYCAROTENOID DIOXYGENASE2, ABA DEFICIENT3, and ABSCISIC ALDEHYDE OXIDASE3 (AAO3) exhibited abnormally low transcript levels in dark-treated nap leaves. NAP transactivated the promoter of AAO3 in mesophyll cell protoplasts, and electrophoretic mobility shift assays showed that NAP can bind directly to a segment (-196 to -162 relative to the ATG start codon) of the AAO3 promoter. Exogenous application of ABA increased the transcript levels of SGR1, NYC1, PPH, and PaO and suppressed the stay-green phenotype of nap leaves during extended darkness. Overexpression of AAO3 in nap leaves also suppressed the stay-green phenotype under extended darkness. Collectively, the results show that NAP promotes chlorophyll degradation by enhancing transcription of AAO3, which leads to increased levels of the senescence-inducing hormone ABA.

  20. Abscisic acid: biosynthesis, inactivation, homoeostasis and signalling.

    PubMed

    Dong, Ting; Park, Youngmin; Hwang, Inhwan

    2015-01-01

    The phytohormone abscisic acid (ABA) plays crucial roles in numerous physiological processes during plant growth and abiotic stress responses. The endogenous ABA level is controlled by complex regulatory mechanisms involving biosynthesis, catabolism, transport and signal transduction pathways. This complex regulatory network may target multiple levels, including transcription, translation and post-translational regulation of genes involved in ABA responses. Most of the genes involved in ABA biosynthesis, catabolism and transport have been characterized. The local ABA concentration is critical for initiating ABA-mediated signalling during plant development and in response to environmental changes. In this chapter we discuss the mechanisms that regulate ABA biosynthesis, catabolism, transport and homoeostasis. We also present the findings of recent research on ABA perception by cellular receptors, and ABA signalling in response to cellular and environmental conditions.

  1. UDP-glucosyltransferase71c5, a major glucosyltransferase, mediates abscisic acid homeostasis in Arabidopsis.

    PubMed

    Liu, Zhen; Yan, Jin-Ping; Li, De-Kuan; Luo, Qin; Yan, Qiujie; Liu, Zhi-Bin; Ye, Li-Ming; Wang, Jian-Mei; Li, Xu-Feng; Yang, Yi

    2015-04-01

    Abscisic acid (ABA) plays a key role in plant growth and development. The effect of ABA in plants mainly depends on its concentration, which is determined by a balance between biosynthesis and catabolism of ABA. In this study, we characterize a unique UDP-glucosyltransferase (UGT), UGT71C5, which plays an important role in ABA homeostasis by glucosylating ABA to abscisic acid -: glucose ester (GE) in Arabidopsis (Arabidopsis thaliana). Biochemical analyses show that UGT71C5 glucosylates ABA in vitro and in vivo. Mutation of UGT71C5 and down-expression of UGT71C5 in Arabidopsis cause delay in seed germination and enhanced drought tolerance. In contrast, overexpression of UGT71C5 accelerates seed germination and reduces drought tolerance. Determination of the content of ABA and ABA-GE in Arabidopsis revealed that mutation in UGT71C5 and down-expression of UGT71C5 resulted in increased level of ABA and reduced level of ABA-GE, whereas overexpression of UGT71C5 resulted in reduced level of ABA and increased level of ABA-GE. Furthermore, altered levels of ABA in plants lead to changes in transcript abundance of ABA-responsive genes, correlating with the concentration of ABA regulated by UGT71C5 in Arabidopsis. Our work shows that UGT71C5 plays a major role in ABA glucosylation for ABA homeostasis.

  2. CAST AWAY, a membrane-associated receptor-like kinase, inhibits organ abscission in Arabidopsis.

    PubMed

    Burr, Christian A; Leslie, Michelle E; Orlowski, Sara K; Chen, Iris; Wright, Catherine E; Daniels, Mark J; Liljegren, Sarah J

    2011-08-01

    Receptor-like kinase-mediated cell signaling pathways play fundamental roles in many aspects of plant growth and development. A pair of Arabidopsis (Arabidopsis thaliana) leucine-rich repeat receptor-like kinases (LRR-RLKs), HAESA (HAE) and HAESA-LIKE2 (HSL2), have been shown to activate the cell separation process that leads to organ abscission. Another pair of LRR-RLKs, EVERSHED (EVR) and SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE1, act as inhibitors of abscission, potentially by modulating HAE/HSL2 activity. Cycling of these RLKs to and from the cell surface may be regulated by NEVERSHED (NEV), a membrane trafficking regulator that is essential for organ abscission. We report here the characterization of CAST AWAY (CST), a receptor-like cytoplasmic kinase that acts as a spatial inhibitor of cell separation. Disruption of CST suppresses the abscission defects of nev mutant flowers and restores the discrete identity of the trans-Golgi network in nev abscission zones. After organ shedding, enlarged abscission zones with obscured boundaries are found in nev cst flowers. We show that CST is a dual-specificity kinase in vitro and that myristoylation at its amino terminus promotes association with the plasma membrane. Using the bimolecular fluorescence complementation assay, we have detected interactions of CST with HAE and EVR at the plasma membrane of Arabidopsis protoplasts and hypothesize that CST negatively regulates cell separation signaling directly and indirectly. A model integrating the potential roles of receptor-like kinase signaling and membrane trafficking during organ separation is presented.

  3. FCA does not bind abscisic acid.

    PubMed

    Risk, Joanna M; Macknight, Richard C; Day, Catherine L

    2008-12-11

    The RNA-binding protein FCA promotes flowering in Arabidopsis. Razem et al. reported that FCA is also a receptor for the phytohormone abscisic acid (ABA). However, we find that FCA does not bind ABA, suggesting that the quality of the proteins assayed and the sensitivity of the ABA-binding assay have led Razem et al. to erroneous conclusions. Because similar assays have been used to characterize other ABA receptors, our results indicate that the ABA-binding properties of these proteins should be carefully re-evaluated and that alternative ABA receptors are likely to be discovered.

  4. Identification of OsbZIP72 as a positive regulator of ABA response and drought tolerance in rice.

    PubMed

    Lu, Guojun; Gao, Chenxi; Zheng, Xingnan; Han, Bin

    2009-02-01

    Abscisic Acid (ABA) is an important phytohormone involved in abiotic stress resistance in plants. A group of bZIP transcription factors play important roles in the ABA signaling pathway in Arabidopsis. However, little is known about the function of their orthologs in rice, where they may hold a great potential for developing drought resistant food crops. In this study, our phylogenetic analysis showed that this group of bZIPs was evolutionarily conserved between Arabidopsis and rice, which implies that they may share similar functions. We demonstrated with quantitative RT-PCR that the expressions of most of these OsbZIPs were significantly induced by ABA, ACC, and abiotic stresses. OsbZIP72, a member of this group, was proved to be an ABRE binding factor in rice using the yeast hybrid systems. We showed that it could bind to ABRE and transactivate the downstream reporter genes in yeast, and the transactivity was depending on its N-terminal region. Transgenic rice overexpressing OsbZIP72 showed a hypersensitivity to ABA, elevated levels of expression of ABA response gene such as LEAs, and an enhanced ability of drought tolerance. These results suggest that OsbZIP72 plays a positive role in drought resistance through ABA signaling, and is potential useful for engineering drought tolerant rice.

  5. Nitrophenolates spray can alter boll abscission rate in cotton through enhanced peroxidase activity and increased ascorbate and phenolics levels.

    PubMed

    Djanaguiraman, M; Sheeba, J Annie; Devi, D Durga; Bangarusamy, U; Prasad, P V V

    2010-01-01

    Field studies were conducted from 2002 to 2005 to evaluate foliar spray of Atonik (a plant growth regulator (PGR) containing nitrophenolates) on cotton boll abscission rate by assessing various reactive oxygen species (ROS) contents, antioxidant content and antioxidant enzyme activity from 1 to 9 days after anthesis (DAA). The result indicated that the nitrophenolate spray reduced hydrogen peroxide (H(2)O(2)), superoxide anion (O(2)(-)) accumulation, lipid peroxidation (malondialdehyde--MDA), lipoxygenase (LOX) activity and membrane permeability relative to the control. Antioxidant enzyme activity (superoxide dismutase, SOD; ascorbate peroxidase, APX; peroxidase, POX; glutathione peroxidase, GSH-Px) was significantly increased by the nitrophenolate spray. The POX (217%) and GSH-Px (242%) activities were enhanced compared with APX (7.7%) activity at 9 DAA. Enhanced accumulation of ascorbate (245%), phenol (253%) and proline (150%) was observed in nitrophenolate-sprayed plants compared with control at 9 DAA. Because ascorbate content is increased by higher dehydroascorbate reductase (DHAR) enzyme activity, the ascorbate was able to replenish reducing equivalents to phenoxyl radicals, resulting in an increase of phenolic compounds. The increased phenolic acid content may be involved in scavenging the ROS produced in developing cotton boll. The role of DHAR and glutathione reductase (GR) in keeping higher levels of reduced ascorbate and low levels of endogenous H(2)O(2) in the developing cotton boll may be the prerequisite for boll retention. Based on the present work, we conclude that nitrophenolate-sprayed plants counteracted the deleterious effects of ROS by the peroxide/phenolics/ascorbate system, which causes reduced boll abscission and increased yield.

  6. Carbon dioxide enrichment alleviates heat stress by improving cellular redox homeostasis through an ABA-independent process in tomato plants.

    PubMed

    Li, X; Ahammed, G J; Zhang, Y Q; Zhang, G Q; Sun, Z H; Zhou, J; Zhou, Y H; Xia, X J; Yu, J Q; Shi, K

    2015-01-01

    Plant responses to elevated CO₂ and high temperature are critically regulated through a complex network of phytohormones and redox homeostasis. However, the involvement of abscisic acid (ABA) in plant adaptation to heat stress under elevated CO₂ conditions has not been thoroughly studied. This study investigated the interactive effects of elevated CO₂ (800 μmol·mol(-1) ) and heat stress (42 °C for 24 h) on the endogenous level of ABA and the cellular redox state of two genotypes of tomato with different ABA biosynthesis capacities. Heat stress significantly decreased maximum photochemical efficiency of PSII (Fv/Fm) and leaf water potential, but also increased levels of malondialdehyde (MDA) and electrolyte leakage (EL) in both genotypes. Heat-induced damage was more severe in the ABA-deficient mutant notabilis (not) than in its parental cultivar Ailsa Craig (Ailsa), suggesting that a certain level of endogenous ABA is required to minimise the heat-induced oxidative damage to the photosynthetic apparatus. Irrespective of genotype, the enrichment of CO₂ remarkably stimulated Fv/Fm, MDA and EL in heat-stressed plants towards enhanced tolerance. In addition, elevated CO₂ significantly strengthened the antioxidant capacity of heat-stressed tomato seedlings towards a reduced cellular redox state for a prolonged period, thereby mitigating oxidative stress. However, elevated CO₂ and heat stress did not alter the endogenous level of ABA or the expression of its biosynthetic gene NCED2 in either genotype, indicating that ABA is not involved in elevated CO₂ -induced heat stress alleviation. The results of this study suggest that elevated CO₂ alleviated heat stress through efficient regulation of the cellular redox poise in an ABA-independent manner in tomato plants.

  7. Abscisic acid and blue light signaling pathways in chloroplast movements in Arabidopsis mesophyll.

    PubMed

    Eckstein, Aleksandra; Krzeszowiec, Weronika; Banaś, Agnieszka Katarzyna; Janowiak, Franciszek; Gabryś, Halina

    2016-01-01

    Abscisic acid (ABA) and phototropins act antagonistically to control stomatal movements. Here, we investigated the role of ABA in phototropin-directed chloroplast movements in mesophyll cells of Arabidopsis thaliana. We analyzed the expression of phototropins at mRNA and protein level under the influence of ABA. PHOT1 mRNA level was decreased by ABA in the dark while it was insensitive to ABA in light. PHOT2 mRNA level was independent of the hormone treatment. The levels of phototropin proteins were down-regulated by ABA, both in darkness and light. No impact of exogenous ABA on amplitudes and kinetics of chloroplast movements was detected. Chloroplast responses in wild type Arabidopsis and three mutants, abi4, abi2 (abscisic acid insensitive4, 2) and aba1 (abscisic acid1), were measured to account for endogenous ABA signaling. The chloroplast responses were slightly reduced in abi2 and aba1 mutants in strong light. To further investigate the effect, abi2 and aba1 mutants were supplemented with exogenous ABA. In the aba1 mutant, the reaction was rescued but in abi2 it was unaffected. Our results show that ABA is not directly involved in phototropin-controlled chloroplast responses in mature leaves of Arabidopsis. However, the disturbance of ABA biosynthesis and signaling in mutants affects some elements of the chloroplast movement mechanism. In line with its role as a stress hormone, ABA appears to enhance plant sensitivity to light and promote the chloroplast avoidance response.

  8. 1-Aminocyclopropane-1-Carboxylate Oxidase Induction in Tomato Flower Pedicel Phloem and Abscission Related Processes Are Differentially Sensitive to Ethylene

    PubMed Central

    Chersicola, Marko; Kladnik, Aleš; Tušek Žnidarič, Magda; Mrak, Tanja; Gruden, Kristina; Dermastia, Marina

    2017-01-01

    Ethylene has impact on several physiological plant processes, including abscission, during which plants shed both their vegetative and reproductive organs. Cell separation and programmed cell death are involved in abscission, and these have also been correlated with ethylene action. However, the detailed spatiotemporal pattern of the molecular events during abscission remains unknown. We examined the expression of two tomato ACO genes, LeACO1, and LeACO4 that encode the last enzyme in ethylene biosynthesis, 1-aminocyclopropane-1-carboxylate oxidase (ACO), together with the expression of other abscission-associated genes involved in cell separation and programmed cell death, during a period of 0–12 h after abscission induction in the tomato flower pedicel abscission zone and nearby tissues. In addition, we determined their localization in specific cell layers of the flower pedicel abscission zone and nearby tissues obtained by laser microdissection before and 8 h after abscission induction. The expression of both ACO genes was localized to the vascular tissues in the pedicel. While LeACO4 was more uniformly expressed in all examined cell layers, the main expression site of LeACO1 was in cell layers just outside the abscission zone in its proximal and distal part. We showed that after abscission induction, ACO1 protein was synthesized in phloem companion cells, in which it was localized mainly in the cytoplasm. Samples were additionally treated with 1-methylcyclopropene (1-MCP), a competitive inhibitor of ethylene actions, and analyzed 8 h after abscission induction. Cell-layer-specific changes in gene expression were observed together with the specific localization and ethylene sensitivity of the hallmarks of cell separation and programmed cell death. While treatment with 1-MCP prevented separation of cells through inhibition of the expression of polygalacturonases, which are the key enzymes involved in degradation of the middle lamella, this had less impact on

  9. Conservation of the abscission signaling peptide IDA during Angiosperm evolution: withstanding genome duplications and gain and loss of the receptors HAE/HSL2

    PubMed Central

    Stø, Ida M.; Orr, Russell J. S.; Fooyontphanich, Kim; Jin, Xu; Knutsen, Jonfinn M. B.; Fischer, Urs; Tranbarger, Timothy J.; Nordal, Inger; Aalen, Reidunn B.

    2015-01-01

    The peptide INFLORESCENCE DEFICIENT IN ABSCISSION (IDA), which signals through the leucine-rich repeat receptor-like kinases HAESA (HAE) and HAESA-LIKE2 (HSL2), controls different cell separation events in Arabidopsis thaliana. We hypothesize the involvement of this signaling module in abscission processes in other plant species even though they may shed other organs than A. thaliana. As the first step toward testing this hypothesis from an evolutionarily perspective we have identified genes encoding putative orthologs of IDA and its receptors by BLAST searches of publically available protein, nucleotide and genome databases for angiosperms. Genes encoding IDA or IDA-LIKE (IDL) peptides and HSL proteins were found in all investigated species, which were selected as to represent each angiosperm order with available genomic sequences. The 12 amino acids representing the bioactive peptide in A. thaliana have virtually been unchanged throughout the evolution of the angiosperms; however, the number of IDL and HSL genes varies between different orders and species. The phylogenetic analyses suggest that IDA, HSL2, and the related HSL1 gene, were present in the species that gave rise to the angiosperms. HAE has arisen from HSL1 after a genome duplication that took place after the monocot—eudicots split. HSL1 has also independently been duplicated in the monocots, while HSL2 has been lost in gingers (Zingiberales) and grasses (Poales). IDA has been duplicated in eudicots to give rise to functionally divergent IDL peptides. We postulate that the high number of IDL homologs present in the core eudicots is a result of multiple whole genome duplications (WGD). We substantiate the involvement of IDA and HAE/HSL2 homologs in abscission by providing gene expression data of different organ separation events from various species. PMID:26579174

  10. Genome-wide identification of cassava R2R3 MYB family genes related to abscission zone separation after environmental-stress-induced abscission

    PubMed Central

    Liao, Wenbin; Yang, Yiling; Li, Yayun; Wang, Gan; Peng, Ming

    2016-01-01

    Cassava plants (Manihot esculenta Crantz) resist environmental stresses by shedding leaves in leaf pulvinus abscission zones (AZs), thus leading to adaptation to new environmental conditions. Little is known about the roles of cassava R2R3 MYB factors in regulating AZ separation. Herein, 166 cassava R2R3 MYB genes were identified. Evolutionary analysis indicated that the 166 R2R3 MYB genes could be divided into 11 subfamilies. Transcriptome analysis indicated that 26 R2R3 MYB genes were expressed in AZs across six time points during both ethylene- and water-deficit stress-induced leaf abscission. Comparative expression profile analysis of similar SOTA (Self Organizing Tree Algorithm) clusters demonstrated that 10 R2R3 MYB genes had similar expression patterns at six time points in response to both treatments. GO (Gene Ontology) annotation confirmed that all 10 R2R3 MYB genes participated in the responses to stress and ethylene and auxin stimuli. Analysis of the putative 10 R2R3 MYB promoter regions showed that those genes primarily contained ethylene- and stress-related cis-elements. The expression profiles of the genes acting downstream of the selected MYBs were confirmed to be involved in cassava abscission zone separation. All these results indicated that R2R3 MYB plays an important regulatory role in AZ separation. PMID:27573926

  11. Characterization of Abscisic Acid-Induced Ethylene Production in Citrus Leaf and Tomato Fruit Tissues 1

    PubMed Central

    Riov, Joseph; Dagan, Eliahu; Goren, Raphael; Yang, Shang Fa

    1990-01-01

    Abscisic acid (ABA) significantly stimulated ethylene production in citrus (Citrus sinensis [L.] Osbeck, cv Shamouti orange) leaf discs. The extent of stimulation was dependent upon the concentration of ABA (0.1-1 milimolar) and the duration of treatment (15-300 minutes). Aging the discs before applying ABA increased ABA-induced ethylene production due to enhancement of both ethylene-forming enzyme activity and the responsiveness of ABA. Discs excised from mature leaves were much more responsive to ABA than discs excised from young or senescing leaves. ABA stimulated ethylene production shortly after application, suggesting that ABA does not enhance ethylene production via the acceleration of senescence. The stimulating effect of ABA on ethylene production resulted mainly from the enhancement of 1-aminocylopropane-1-carboxylic acid synthesis. Stimulation of ethylene production by ABA in intact citrus leaves and tomato (Lycopersicon esculentum Mill., cv Castlemart) fruit was small but could be increased by various forms of wounding. PMID:16667264

  12. ABA Suppresses Root Hair Growth via the OBP4 Transcriptional Regulator1[OPEN

    PubMed Central

    Kawamura, Ayako; Schäfer, Sabine; Breuer, Christian; Shibata, Michitaro; Mitsuda, Nobutaka; Ohme-Takagi, Masaru; Matsui, Minami

    2017-01-01

    Plants modify organ growth and tune morphogenesis in response to various endogenous and environmental cues. At the cellular level, organ growth is often adjusted by alterations in cell growth, but the molecular mechanisms underlying this control remain poorly understood. In this study, we identify the DNA BINDING WITH ONE FINGER (DOF)-type transcription regulator OBF BINDING PROTEIN4 (OBP4) as a repressor of cell growth. Ectopic expression of OBP4 in Arabidopsis (Arabidopsis thaliana) inhibits cell growth, resulting in severe dwarfism and the repression of genes involved in the regulation of water transport, root hair development, and stress responses. Among the basic helix-loop-helix transcription factors known to control root hair growth, OBP4 binds the ROOT HAIR DEFECTIVE6-LIKE2 (RSL2) promoter to repress its expression. The accumulation of OBP4 proteins is detected in expanding root epidermal cells, and its expression level is increased by the application of abscisic acid (ABA) at concentrations sufficient to inhibit root hair growth. ABA-dependent induction of OBP4 is associated with the reduced expression of RSL2. Furthermore, ectopic expression of OBP4 or loss of RSL2 function results in ABA-insensitive root hair growth. Taken together, our results suggest that OBP4-mediated transcriptional repression of RSL2 contributes to the ABA-dependent inhibition of root hair growth in Arabidopsis. PMID:28167701

  13. MYB96 shapes the circadian gating of ABA signaling in Arabidopsis

    PubMed Central

    Lee, Hong Gil; Mas, Paloma; Seo, Pil Joon

    2016-01-01

    Circadian clocks regulate the rhythms of biological activities with a period of approximately 24-hours and synchronize plant metabolism and physiology with the environmental cycles. The clock also gates responses to environmental stresses to maximize fitness advantages. Here we report that the MYB96 transcription factor is connected with the clock oscillator to shape the circadian gating of abscisic acid (ABA) responses. MYB96 directly binds to the TIMING OF CAB EXPRESSION 1 (TOC1) promoter to positively regulate its expression. The use of myb96 mutant plants shows that this regulation is essential for the gated induction of TOC1 by ABA. In turn, MYB96 induction by ABA is also altered in toc1-3 mutant plants. The increased tolerance to drought of MYB96 over-expressing plants is decreased in the toc1-3 mutant background, suggesting that MYB96 and TOC1 intersect the circadian clock and ABA signaling. The MYB96-TOC1 function might be also regulated by the clock component CIRCADIAN CLOCK-ASSOCIATED 1 (CCA1), which binds to the MYB96 promoter and alters its circadian expression. Thus, a complex circuitry of CCA1-MYB96-TOC1 regulatory interactions provides the mechanistic basis underlying the connection between circadian and stress signaling to optimize plant fitness to ambient stresses. PMID:26725725

  14. Calcium-dependent oligomerization of CAR proteins at cell membrane modulates ABA signaling

    PubMed Central

    Diaz, Maira; Sanchez-Barrena, Maria Jose; Gonzalez-Rubio, Juana Maria; Rodriguez, Lesia; Fernandez, Daniel; Antoni, Regina; Yunta, Cristina; Belda-Palazon, Borja; Gonzalez-Guzman, Miguel; Peirats-Llobet, Marta; Menendez, Margarita; Boskovic, Jasminka; Marquez, Jose A.; Rodriguez, Pedro L.; Albert, Armando

    2016-01-01

    Regulation of ion transport in plants is essential for cell function. Abiotic stress unbalances cell ion homeostasis, and plants tend to readjust it, regulating membrane transporters and channels. The plant hormone abscisic acid (ABA) and the second messenger Ca2+ are central in such processes, as they are involved in the regulation of protein kinases and phosphatases that control ion transport activity in response to environmental stimuli. The identification and characterization of the molecular mechanisms underlying the effect of ABA and Ca2+ signaling pathways on membrane function are central and could provide opportunities for crop improvement. The C2-domain ABA-related (CAR) family of small proteins is involved in the Ca2+-dependent recruitment of the pyrabactin resistance 1/PYR1-like (PYR/PYL) ABA receptors to the membrane. However, to fully understand CAR function, it is necessary to define a molecular mechanism that integrates Ca2+ sensing, membrane interaction, and the recognition of the PYR/PYL interacting partners. We present structural and biochemical data showing that CARs are peripheral membrane proteins that functionally cluster on the membrane and generate strong positive membrane curvature in a Ca2+-dependent manner. These features represent a mechanism for the generation, stabilization, and/or specific recognition of membrane discontinuities. Such structures may act as signaling platforms involved in the recruitment of PYR/PYL receptors and other signaling components involved in cell responses to stress. PMID:26719420

  15. ABA control of plant macroelement membrane transport systems in response to water deficit and high salinity.

    PubMed

    Osakabe, Yuriko; Yamaguchi-Shinozaki, Kazuko; Shinozaki, Kazuo; Tran, Lam-Son Phan

    2014-04-01

    Plant growth and productivity are adversely affected by various abiotic stressors and plants develop a wide range of adaptive mechanisms to cope with these adverse conditions, including adjustment of growth and development brought about by changes in stomatal activity. Membrane ion transport systems are involved in the maintenance of cellular homeostasis during exposure to stress and ion transport activity is regulated by phosphorylation/dephosphorylation networks that respond to stress conditions. The phytohormone abscisic acid (ABA), which is produced rapidly in response to drought and salinity stress, plays a critical role in the regulation of stress responses and induces a series of signaling cascades. ABA signaling involves an ABA receptor complex, consisting of an ABA receptor family, phosphatases and kinases: these proteins play a central role in regulating a variety of diverse responses to drought stress, including the activities of membrane-localized factors, such as ion transporters. In this review, recent research on signal transduction networks that regulate the function ofmembrane transport systems in response to stress, especially water deficit and high salinity, is summarized and discussed. The signal transduction networks covered in this review have central roles in mitigating the effect of stress by maintaining plant homeostasis through the control of membrane transport systems.

  16. Calcium-dependent oligomerization of CAR proteins at cell membrane modulates ABA signaling.

    PubMed

    Diaz, Maira; Sanchez-Barrena, Maria Jose; Gonzalez-Rubio, Juana Maria; Rodriguez, Lesia; Fernandez, Daniel; Antoni, Regina; Yunta, Cristina; Belda-Palazon, Borja; Gonzalez-Guzman, Miguel; Peirats-Llobet, Marta; Menendez, Margarita; Boskovic, Jasminka; Marquez, Jose A; Rodriguez, Pedro L; Albert, Armando

    2016-01-19

    Regulation of ion transport in plants is essential for cell function. Abiotic stress unbalances cell ion homeostasis, and plants tend to readjust it, regulating membrane transporters and channels. The plant hormone abscisic acid (ABA) and the second messenger Ca(2+) are central in such processes, as they are involved in the regulation of protein kinases and phosphatases that control ion transport activity in response to environmental stimuli. The identification and characterization of the molecular mechanisms underlying the effect of ABA and Ca(2+) signaling pathways on membrane function are central and could provide opportunities for crop improvement. The C2-domain ABA-related (CAR) family of small proteins is involved in the Ca(2+)-dependent recruitment of the pyrabactin resistance 1/PYR1-like (PYR/PYL) ABA receptors to the membrane. However, to fully understand CAR function, it is necessary to define a molecular mechanism that integrates Ca(2+) sensing, membrane interaction, and the recognition of the PYR/PYL interacting partners. We present structural and biochemical data showing that CARs are peripheral membrane proteins that functionally cluster on the membrane and generate strong positive membrane curvature in a Ca(2+)-dependent manner. These features represent a mechanism for the generation, stabilization, and/or specific recognition of membrane discontinuities. Such structures may act as signaling platforms involved in the recruitment of PYR/PYL receptors and other signaling components involved in cell responses to stress.

  17. ABA induces H2O2 production in guard cells, but does not close the stomata on Vicia faba leaves developed at high air humidity.

    PubMed

    Arve, Louise E; Carvalho, Dália R A; Olsen, Jorunn E; Torre, Sissel

    2014-01-01

    Plants developed under constant high (> 85%) relative air humidity (RH) have larger stomata that are unable to close completely. One of the hypotheses for the less responsive stomata is that the plants have reduced sensitivity to abscisic acid (ABA). Both ABA and darkness are signals for stomatal closure and induce the production of the secondary messenger hydrogen peroxide (H2O2). In this study, the ability of Vicia faba plants developed in moderate or high RH to close the stomata in response to darkness, ABA and H2O2 was investigated. Moreover, the ability of the plants to produce H2O2 when treated with ABA or transferred to darkness was also assessed. Our results show that the ABA concentration in moderate RH is not increased during darkness even though the stomata are closing. This indicates that stomatal closure in V. faba during darkness is independent of ABA production. ABA induced both H2O2 production and stomatal closure in stomata formed at moderate RH. H2O2 production, as a result of treatment with ABA, was also observed in stomata formed at high RH, though the closing response was considerably smaller as compared with moderate RH. In either RH, leaf ABA concentration was not affected by darkness. Similarly to ABA treatment, darkness elicited both H2O2 production and stomatal closure following plant cultivation at moderate RH. Contrary to this, neither H2O2 production nor stomatal closure took place when stomata were formed at high RH. These results suggest that the reduced stomatal response in plants developed in continuous high RH is caused by one or more factors downstream of H2O2 in the signaling pathway toward stomatal closure.

  18. Timing is everything: early degradation of abscission layer is associated with increased seed shattering in U.S. weedy rice

    PubMed Central

    2011-01-01

    Background Seed shattering, or shedding, is an important fitness trait for wild and weedy grasses. U.S. weedy rice (Oryza sativa) is a highly shattering weed, thought to have evolved from non-shattering cultivated ancestors. All U.S. weedy rice individuals examined to date contain a mutation in the sh4 locus associated with loss of shattering during rice domestication. Weedy individuals also share the shattering trait with wild rice, but not the ancestral shattering mutation at sh4; thus, how weedy rice reacquired the shattering phenotype is unknown. To establish the morphological basis of the parallel evolution of seed shattering in weedy rice and wild, we examined the abscission layer at the flower-pedicel junction in weedy individuals in comparison with wild and cultivated relatives. Results Consistent with previous work, shattering wild rice individuals possess clear, defined abscission layers at flowering, whereas non-shattering cultivated rice individuals do not. Shattering weedy rice from two separately evolved populations in the U.S. (SH and BHA) show patterns of abscission layer formation and degradation distinct from wild rice. Prior to flowering, the abscission layer has formed in all weedy individuals and by flowering it is already degrading. In contrast, wild O. rufipogon abscission layers have been shown not to degrade until after flowering has occurred. Conclusions Seed shattering in weedy rice involves the formation and degradation of an abscission layer in the flower-pedicel junction, as in wild Oryza, but is a developmentally different process from shattering in wild rice. Weedy rice abscission layers appear to break down earlier than wild abscission layers. The timing of weedy abscission layer degradation suggests that unidentified regulatory genes may play a critical role in the reacquisition of shattering in weedy rice, and sheds light on the morphological basis of parallel evolution for shattering in weedy and wild rice. PMID:21235796

  19. Genome-wide digital transcript analysis of putative fruitlet abscission related genes regulated by ethephon in litchi

    PubMed Central

    Li, Caiqin; Wang, Yan; Ying, Peiyuan; Ma, Wuqiang; Li, Jianguo

    2015-01-01

    The high level of physiological fruitlet abscission in litchi (Litchi chinensis Sonn.) causes severe yield loss. Cell separation occurs at the fruit abscission zone (FAZ) and can be triggered by ethylene. However, a deep knowledge of the molecular events occurring in the FAZ is still unknown. Here, genome-wide digital transcript abundance (DTA) analysis of putative fruit abscission related genes regulated by ethephon in litchi were studied. More than 81 million high quality reads from seven ethephon treated and untreated control libraries were obtained by high-throughput sequencing. Through DTA profile analysis in combination with Gene Ontology and KEGG pathway enrichment analyses, a total of 2730 statistically significant candidate genes were involved in the ethephon-promoted litchi fruitlet abscission. Of these, there were 1867 early-responsive genes whose expressions were up- or down-regulated from 0 to 1 d after treatment. The most affected genes included those related to ethylene biosynthesis and signaling, auxin transport and signaling, transcription factors (TFs), protein ubiquitination, ROS response, calcium signal transduction, and cell wall modification. These genes could be clustered into four groups and 13 subgroups according to their similar expression patterns. qRT-PCR displayed the expression pattern of 41 selected candidate genes, which proved the accuracy of our DTA data. Ethephon treatment significantly increased fruit abscission and ethylene production of fruitlet. The possible molecular events to control the ethephon-promoted litchi fruitlet abscission were prompted out. The increased ethylene evolution in fruitlet would suppress the synthesis and polar transport of auxin and trigger abscission signaling. To the best of our knowledge, it is the first time to monitor the gene expression profile occurring in the FAZ-enriched pedicel during litchi fruit abscission induced by ethephon on the genome-wide level. This study will contribute to a better

  20. Genome-wide digital transcript analysis of putative fruitlet abscission related genes regulated by ethephon in litchi.

    PubMed

    Li, Caiqin; Wang, Yan; Ying, Peiyuan; Ma, Wuqiang; Li, Jianguo

    2015-01-01

    The high level of physiological fruitlet abscission in litchi (Litchi chinensis Sonn.) causes severe yield loss. Cell separation occurs at the fruit abscission zone (FAZ) and can be triggered by ethylene. However, a deep knowledge of the molecular events occurring in the FAZ is still unknown. Here, genome-wide digital transcript abundance (DTA) analysis of putative fruit abscission related genes regulated by ethephon in litchi were studied. More than 81 million high quality reads from seven ethephon treated and untreated control libraries were obtained by high-throughput sequencing. Through DTA profile analysis in combination with Gene Ontology and KEGG pathway enrichment analyses, a total of 2730 statistically significant candidate genes were involved in the ethephon-promoted litchi fruitlet abscission. Of these, there were 1867 early-responsive genes whose expressions were up- or down-regulated from 0 to 1 d after treatment. The most affected genes included those related to ethylene biosynthesis and signaling, auxin transport and signaling, transcription factors (TFs), protein ubiquitination, ROS response, calcium signal transduction, and cell wall modification. These genes could be clustered into four groups and 13 subgroups according to their similar expression patterns. qRT-PCR displayed the expression pattern of 41 selected candidate genes, which proved the accuracy of our DTA data. Ethephon treatment significantly increased fruit abscission and ethylene production of fruitlet. The possible molecular events to control the ethephon-promoted litchi fruitlet abscission were prompted out. The increased ethylene evolution in fruitlet would suppress the synthesis and polar transport of auxin and trigger abscission signaling. To the best of our knowledge, it is the first time to monitor the gene expression profile occurring in the FAZ-enriched pedicel during litchi fruit abscission induced by ethephon on the genome-wide level. This study will contribute to a better

  1. A knotted1-like homeobox protein regulates abscission in tomato by modulating the auxin pathway

    Technology Transfer Automated Retrieval System (TEKTRAN)

    KD1, a gene encoding a KNOTTED1-LIKE HOMEOBOX transcription factor is known to be involved, in tomato, in ontogeny of the compound leaf. KD1 is also highly expressed in both leaf and flower abscission zones. Reducing abundance of transcripts of this gene in tomato, using both virus induced gene sile...

  2. Roles of Ethylene Production and Ethylene Receptor Expression in Regulating Apple Fruitlet Abscission1[OPEN

    PubMed Central

    Eccher, Giulia; Begheldo, Maura; Boschetti, Andrea; Ruperti, Benedetto; Botton, Alessandro

    2015-01-01

    Apple (Malus × domestica) is increasingly being considered an interesting model species for studying early fruit development, during which an extremely relevant phenomenon, fruitlet abscission, may occur as a response to both endogenous and/or exogenous cues. Several studies were carried out shedding light on the main physiological and molecular events leading to the selective release of lateral fruitlets within a corymb, either occurring naturally or as a result of a thinning treatment. Several studies pointed out a clear association between a rise of ethylene biosynthetic levels in the fruitlet and its tendency to abscise. A direct mechanistic link, however, has not yet been established between this gaseous hormone and the generation of the abscission signal within the fruit. In this work, the role of ethylene during the very early stages of abscission induction was investigated in fruitlet populations with different abscission potentials due either to the natural correlative inhibitions determining the so-called physiological fruit drop or to a well-tested thinning treatment performed with the cytokinin benzyladenine. A crucial role was ascribed to the ratio between the ethylene produced by the cortex and the expression of ethylene receptor genes in the seed. This ratio would determine the final probability to abscise. A working model has been proposed consistent with the differential distribution of four receptor transcripts within the seed, which resembles a spatially progressive cell-specific immune-like mechanism evolved by apple to protect the embryo from harmful ethylene. PMID:25888617

  3. Profiling gene expression in citrus fruit calyx abscission zone (AZ-C) treated with ethylene.

    PubMed

    Cheng, Chunzhen; Zhang, Lingyun; Yang, Xuelian; Zhong, Guangyan

    2015-10-01

    On-tree storage and harvesting of mature fruit account for a large proportion of cost in the production of citrus, and a reduction of the cost would not be achieved without a thorough understanding of the mechani sm of the mature fruit abscission. Genome-wide gene expression changes in ethylene-treated fruit calyx abscission zone (AZ-C) of Citrus sinensis cv. Olinda were therefore investigated using a citrus genome array representing up to 33,879 citrus transcripts. In total, 1313 and 1044 differentially regulated genes were identified in AZ-C treated with ethylene for 4 and 24 h, respectively. The results showed that mature citrus fruit abscission commenced with the activation of ethylene signal transduction pathway that led to the activation of ethylene responsive transcription factors and the subsequent transcriptional regulation of a large set of ethylene responsive genes. Significantly down-regulated genes included those of starch/sugar biosynthesis, transportation of water and growth promoting hormone synthesis and signaling, whereas significantly up-regulated genes were those involved in defense, cell wall degradation, and secondary metabolism. Our data unraveled the underlying mechanisms of some known important biochemical events occurring at AZ-C and should provide informative suggestions for future manipulation of the events to achieve a controllable abscission for mature citrus fruit.

  4. Roles of Ethylene Production and Ethylene Receptor Expression in Regulating Apple Fruitlet Abscission.

    PubMed

    Eccher, Giulia; Begheldo, Maura; Boschetti, Andrea; Ruperti, Benedetto; Botton, Alessandro

    2015-09-01

    Apple (Malus × domestica) is increasingly being considered an interesting model species for studying early fruit development, during which an extremely relevant phenomenon, fruitlet abscission, may occur as a response to both endogenous and/or exogenous cues. Several studies were carried out shedding light on the main physiological and molecular events leading to the selective release of lateral fruitlets within a corymb, either occurring naturally or as a result of a thinning treatment. Several studies pointed out a clear association between a rise of ethylene biosynthetic levels in the fruitlet and its tendency to abscise. A direct mechanistic link, however, has not yet been established between this gaseous hormone and the generation of the abscission signal within the fruit. In this work, the role of ethylene during the very early stages of abscission induction was investigated in fruitlet populations with different abscission potentials due either to the natural correlative inhibitions determining the so-called physiological fruit drop or to a well-tested thinning treatment performed with the cytokinin benzyladenine. A crucial role was ascribed to the ratio between the ethylene produced by the cortex and the expression of ethylene receptor genes in the seed. This ratio would determine the final probability to abscise. A working model has been proposed consistent with the differential distribution of four receptor transcripts within the seed, which resembles a spatially progressive cell-specific immune-like mechanism evolved by apple to protect the embryo from harmful ethylene.

  5. Survival and arm abscission are linked to regional heterothermy in an intertidal sea star.

    PubMed

    Pincebourde, Sylvain; Sanford, Eric; Helmuth, Brian

    2013-06-15

    Body temperature is a more pertinent variable to physiological stress than ambient air temperature. Modeling and empirical studies on the impacts of climate change on ectotherms usually assume that body temperature within organisms is uniform. However, many ectotherms show significant within-body temperature heterogeneity. The relationship between regional heterothermy and the response of ectotherms to sublethal and lethal conditions remains underexplored. We quantified within-body thermal heterogeneity in an intertidal sea star (Pisaster ochraceus) during aerial exposure at low tide to examine the lethal and sublethal effects of temperatures of different body regions. In manipulative experiments, we measured the temperature of the arms and central disc, as well as survival and arm abscission under extreme aerial conditions. Survival was related strongly to central disc temperature. Arms were generally warmer than the central disc in individuals that survived aerial heating, but we found the reverse in those that died. When the central disc reached sublethal temperatures of 31-35°C, arms reached temperatures of 33-39°C, inducing arm abscission. The absolute temperature of individual arms was a poor predictor of arm abscission, but the arms lost were consistently the hottest at the within-individual scale. Therefore, the vital region of this sea star may remain below the lethal threshold under extreme conditions, possibly through water movement from the arms to the central disc and/or evaporative cooling, but at the cost of increased risk of arm abscission. Initiation of arm abscission seems to reflect a whole-organism response while death occurs as a result of stress acting directly on central disc tissues.

  6. A balanced JA/ABA status may correlate with adaptation to osmotic stress in Vitis cells.

    PubMed

    Ismail, Ahmed; Seo, Mitsunori; Takebayashi, Yumiko; Kamiya, Yuji; Nick, Peter

    2015-08-01

    Water-related stress is considered a major type of plant stress. Osmotic stress, in particular, represents the common part of all water-related stresses. Therefore, plants have evolved different adaptive mechanisms to cope with osmotic-related disturbances. In the current work, two grapevine cell lines that differ in their osmotic adaptability, Vitis rupestris and Vitis riparia, were investigated under mannitol-induced osmotic stress. To dissect signals that lead to adaptability from those related to sensitivity, osmotic-triggered responses with respect to jasmonic acid (JA) and its active form JA-Ile, abscisic acid (ABA), and stilbene compounds, as well as the expression of their related genes were observed. In addition, the transcript levels of the cellular homeostasis gene NHX1 were examined. The data are discussed with a hypothesis suggesting that a balance of JA and ABA status might correlate with cellular responses, either guiding cells to sensitivity or to progress toward adaptation.

  7. Sulphate as a xylem-borne chemical signal precedes the expression of ABA biosynthetic genes in maize roots.

    PubMed

    Ernst, Laura; Goodger, Jason Q D; Alvarez, Sophie; Marsh, Ellen L; Berla, Bert; Lockhart, Eric; Jung, Jiyul; Li, Pinghua; Bohnert, Hans J; Schachtman, Daniel P

    2010-07-01

    Recent reports suggest that early sensing of soil water stress by plant roots and the concomitant reduction in stomatal conductance may not be mediated by root-sourced abscisic acid (ABA), but that other xylem-borne chemicals may be the primary stress signal(s). To gain more insight into the role of root-sourced ABA, the timing and location of the expression of genes for key enzymes involved in ABA biosynthesis in Zea mays roots was measured and a comprehensive analysis of root xylem sap constituents from the early to the later stages of water stress was conducted. Xylem sap and roots were sampled from plants at an early stage of water stress when only a reduction in leaf conductance was measured, as well as at later stages when leaf xylem pressure potential decreased. It was found that the majority of ABA biosynthetic genes examined were only significantly expressed in the elongation region of roots at a later stage of water stress. Apart from ABA, sulphate was the only xylem-borne chemical that consistently showed significantly higher concentrations from the early to the later stages of stress. Moreover, there was an interactive effect of ABA and sulphate in decreasing maize transpiration rate and Vicia faba stomatal aperture, as compared to ABA alone. The expression of a sulphate transporter gene was also analysed and it was found that it had increased in the elongation region of roots from the early to the later stages of water stress. Our results support the suggestion that in the early stage of water stress, increased levels of ABA in xylem sap may not be due to root biosynthesis, ABA glucose ester catabolism or pH-mediated redistribution, but may be due to shoot biosynthesis and translocation to the roots. The analysis of xylem sap mineral content and bioassays indicate that the anti-transpirant effect of the ABA reaching the stomata at the early stages of water stress may be enhanced by the increased concentrations of sulphate in the xylem which is also

  8. Cellular and Pectin Dynamics during Abscission Zone Development and Ripe Fruit Abscission of the Monocot Oil Palm

    PubMed Central

    Roongsattham, Peerapat; Morcillo, Fabienne; Fooyontphanich, Kim; Jantasuriyarat, Chatchawan; Tragoonrung, Somvong; Amblard, Philippe; Collin, Myriam; Mouille, Gregory; Verdeil, Jean-Luc; Tranbarger, Timothy J.

    2016-01-01

    The oil palm (Elaeis guineensis Jacq.) fruit primary abscission zone (AZ) is a multi-cell layered boundary region between the pedicel (P) and mesocarp (M) tissues. To examine the cellular processes that occur during the development and function of the AZ cell layers, we employed multiple histological and immunohistochemical methods combined with confocal, electron and Fourier-transform infrared (FT-IR) microspectroscopy approaches. During early fruit development and differentiation of the AZ, the orientation of cell divisions in the AZ was periclinal compared with anticlinal divisions in the P and M. AZ cell wall width increased earlier during development suggesting cell wall assembly occurred more rapidly in the AZ than the adjacent P and M tissues. The developing fruit AZ contain numerous intra-AZ cell layer plasmodesmata (PD), but very few inter-AZ cell layer PD. In the AZ of ripening fruit, PD were less frequent, wider, and mainly intra-AZ cell layer localized. Furthermore, DAPI staining revealed nuclei are located adjacent to PD and are remarkably aligned within AZ layer cells, and remain aligned and intact after cell separation. The polarized accumulation of ribosomes, rough endoplasmic reticulum, mitochondria, and vesicles suggested active secretion at the tip of AZ cells occurred during development which may contribute to the striated cell wall patterns in the AZ cell layers. AZ cells accumulated intracellular pectin during development, which appear to be released and/or degraded during cell separation. The signal for the JIM5 epitope, that recognizes low methylesterified and un-methylesterified homogalacturonan (HG), increased in the AZ layer cell walls prior to separation and dramatically increased on the separated AZ cell surfaces. Finally, FT-IR microspectroscopy analysis indicated a decrease in methylesterified HG occurred in AZ cell walls during separation, which may partially explain an increase in the JIM5 epitope signal. The results obtained

  9. Cellular and Pectin Dynamics during Abscission Zone Development and Ripe Fruit Abscission of the Monocot Oil Palm.

    PubMed

    Roongsattham, Peerapat; Morcillo, Fabienne; Fooyontphanich, Kim; Jantasuriyarat, Chatchawan; Tragoonrung, Somvong; Amblard, Philippe; Collin, Myriam; Mouille, Gregory; Verdeil, Jean-Luc; Tranbarger, Timothy J

    2016-01-01

    The oil palm (Elaeis guineensis Jacq.) fruit primary abscission zone (AZ) is a multi-cell layered boundary region between the pedicel (P) and mesocarp (M) tissues. To examine the cellular processes that occur during the development and function of the AZ cell layers, we employed multiple histological and immunohistochemical methods combined with confocal, electron and Fourier-transform infrared (FT-IR) microspectroscopy approaches. During early fruit development and differentiation of the AZ, the orientation of cell divisions in the AZ was periclinal compared with anticlinal divisions in the P and M. AZ cell wall width increased earlier during development suggesting cell wall assembly occurred more rapidly in the AZ than the adjacent P and M tissues. The developing fruit AZ contain numerous intra-AZ cell layer plasmodesmata (PD), but very few inter-AZ cell layer PD. In the AZ of ripening fruit, PD were less frequent, wider, and mainly intra-AZ cell layer localized. Furthermore, DAPI staining revealed nuclei are located adjacent to PD and are remarkably aligned within AZ layer cells, and remain aligned and intact after cell separation. The polarized accumulation of ribosomes, rough endoplasmic reticulum, mitochondria, and vesicles suggested active secretion at the tip of AZ cells occurred during development which may contribute to the striated cell wall patterns in the AZ cell layers. AZ cells accumulated intracellular pectin during development, which appear to be released and/or degraded during cell separation. The signal for the JIM5 epitope, that recognizes low methylesterified and un-methylesterified homogalacturonan (HG), increased in the AZ layer cell walls prior to separation and dramatically increased on the separated AZ cell surfaces. Finally, FT-IR microspectroscopy analysis indicated a decrease in methylesterified HG occurred in AZ cell walls during separation, which may partially explain an increase in the JIM5 epitope signal. The results obtained

  10. GSTF1 Gene Expression Analysis in Cultivated Wheat Plants under Salinity and ABA Treatments

    PubMed Central

    Niazi, Ali; Ramezani, Amin; Dinari, Ali

    2014-01-01

    Most plants encounter stress such as drought and salinity that adversely affect growth, development and crop productivity. The expression of the gene glutathione-s-transferases (GST) extends throughout various protective mechanisms in plants and allows them to adapt to unfavorable environmental conditions. GSTF1 (the first phi GSTFs class) gene expression patterns in the wheat cultivars Mahuti and Alamut were studied under salt and ABA treatments using a qRT-PCR technique. Results showed that gene expression patterns were significantly different in these two cultivars. Data showed that in Mahuti, there was an increase of transcript accumulation under salt and ABA treatments at 3h, 10h and 72h respectively. In Alamut, however, the pattern of transcript accumulation was different; the maximum was at 3h. In contrast, there were no significant differences observed between the cultivars for GSTF1 gene expression profiles at three levels of NaCl concentration (50, 100, and 200 mM) or in ABA (Abscisic Acid) treatment. It is likely that difference of gene expression patterns between the cultivars (Mahuti as a salt tolerant cultivar and Alamut as a salt sensitive cultivar) is due to distinct signaling pathways which activate GSTF1 expression. Lack of a significant difference between the GSTF1 gene expression profile under salt and ABA treatments suggests that the GSTF1 gene is not induced by stress stimuli. Of course it is possible that other levels of NaCl and ABA treatments cause a change in the GSTF1 gene. PMID:27843973

  11. Root ABA Accumulation Enhances Rice Seedling Drought Tolerance under Ammonium Supply: Interaction with Aquaporins

    PubMed Central

    Ding, Lei; Li, Yingrui; Wang, Ying; Gao, Limin; Wang, Min; Chaumont, François; Shen, Qirong; Guo, Shiwei

    2016-01-01

    In previous studies, we demonstrated that ammonium nutrition enhances the drought tolerance of rice seedlings compared to nitrate nutrition and contributes to a higher root water uptake ability. It remains unclear why rice seedlings maintain a higher water uptake ability when supplied with ammonium under drought stress. Here, we focused on the effects of nitrogen form and drought stress on root abscisic acid (ABA) concentration and aquaporin expression using hydroponics experiments and stimulating drought stress with 10% PEG6000. Drought stress decreased the leaf photosynthetic rate and stomatal conductivity and increased the leaf temperature of plants supplied with either ammonium or nitrate, but especially under nitrate supply. After 4 h of PEG treatment, the root protoplast water permeability and the expression of root PIP and TIP genes decreased in plants supplied with ammonium or nitrate. After 24 h of PEG treatment, the root hydraulic conductivity, the protoplast water permeability, and the expression of some aquaporin genes increased in plants supplied with ammonium compared to those under non-PEG treatment. Root ABA accumulation was induced by 24 h of PEG treatment, especially in plants supplied with ammonium. The addition of exogenous ABA decreased the expression of PIP and TIP genes under non-PEG treatment but increased the expression of some of them under PEG treatment. We concluded that drought stress induced a down-regulation of aquaporin expression, which appeared earlier than did root ABA accumulation. With continued drought stress, aquaporin expression and activity increased due to root ABA accumulation in plants supplied with ammonium. PMID:27559341

  12. ABA signaling is necessary but not sufficient for RD29B transcriptional memory during successive dehydration stresses in Arabidopsis thaliana.

    PubMed

    Virlouvet, Laetitia; Ding, Yong; Fujii, Hiroaki; Avramova, Zoya; Fromm, Michael

    2014-07-01

    Plants subjected to a prior dehydration stress were seen to have altered transcriptional responses during a subsequent dehydration stress for up to 5 days after the initial stress. The abscisic acid (ABA) inducible RD29B gene of Arabidopsis thaliana was strongly induced after the first stress and displayed transcriptional memory with transcript levels nine-fold higher during the second dehydration stress. These increased transcript levels were due to an increased rate of transcription and are associated with an altered chromatin template during the recovery interval between the dehydration stresses. Here we use a combination of promoter deletion/substitutions, mutants in the trans-acting transcription factors and their upstream protein kinases, and treatments with exogenous ABA or dehydration stress to advance our understanding of the features required for transcriptional memory of RD29B. ABA Response Elements (ABREs) are sufficient to confer transcriptional memory on a minimal promoter, although there is a context effect from flanking sequences. Different mutations in Snf1 Related Protein Kinase 2 (SnRK2) genes positively and negatively affected the response, suggesting that this effect is important for transcriptional memory. Although exogenous ABA treatments could prime transcriptional memory, a second ABA treatment was not sufficient to activate transcriptional memory. Therefore, we concluded that transcriptional memory requires ABA and an ABA-independent factor that is induced or activated by a subsequent dehydration stress and directly or indirectly results in a more active RD29B chromatin template. These results advance our knowledge of the cis- and trans-acting factors that are required for transcriptional memory of RD29B.

  13. Pepper CaREL1, a ubiquitin E3 ligase, regulates drought tolerance via the ABA-signalling pathway.

    PubMed

    Lim, Chae Woo; Park, Chanmi; Kim, Jung-Hyun; Joo, Hyunhee; Hong, Eunji; Lee, Sung Chul

    2017-03-28

    Drought stress conditions in soil or air hinder plant growth and development. Here, we report that the hot pepper (C apsicum a nnuum) RING type E3 Ligase 1 gene (CaREL1) is essential to the drought stress response. CaREL1 encodes a cytoplasmic- and nuclear-localized protein with E3 ligase activity. CaREL1 expression was induced by abscisic acid (ABA) and drought. CaREL1 contains a C3H2C3-type RING finger motif, which functions in ubiquitination of the target protein. We used CaREL1-silenced pepper plants and CaREL1-overexpressing (OX) transgenic Arabidopsis plants to evaluate the in vivo function of CaREL1 in response to drought stress and ABA treatment. CaREL1-silenced pepper plants displayed a drought-tolerant phenotype characterized by ABA hypersensitivity. In contrast, CaREL1-OX plants exhibited ABA hyposensitivity during the germination, seedling, and adult stages. In addition, plant growth was severely impaired under drought stress conditions, via a high level of transpirational water loss and decreased stomatal closure. Quantitative RT-PCR analyses revealed that ABA-related drought stress responsive genes were more weakly expressed in CaREL1-OX plants than in wild-type plants, indicating that CaREL1 functions in the drought stress response via the ABA-signalling pathway. Taken together, our results indicate that CaREL1 functions as a negative regulator of ABA-mediated drought stress tolerance.

  14. Quantitative Proteomic Analyses Identify ABA-Related Proteins and Signal Pathways in Maize Leaves under Drought Conditions.

    PubMed

    Zhao, Yulong; Wang, Yankai; Yang, Hao; Wang, Wei; Wu, Jianyu; Hu, Xiuli

    2016-01-01

    Drought stress is one of major factors resulting in maize yield loss. The roles of abscisic acid (ABA) have been widely studied in crops in response to drought stress. However, more attention is needed to identify key ABA-related proteins and also gain deeper molecular insights about drought stress in maize. Based on this need, the physiology and proteomics of the ABA-deficient maize mutant vp5 and its wild-type Vp5 under drought stress were examined and analyzed. Malondialdehyde content increased and quantum efficiency of photosystem II decreased under drought stress in both genotypes. However, the magnitude of the increase or decrease was significantly higher in vp5 than in Vp5. A total of 7051 proteins with overlapping expression patterns among three replicates in the two genotypes were identified by Multiplex run iTRAQ-based quantitative proteomic and liquid chromatography-tandem mass spectrometry methods, of which the expression of only 150 proteins (130 in Vp5, 27 in vp5) showed changes of at least 1.5-fold under drought stress. Among the 150 proteins, 67 and 60 proteins were up-regulated and down-regulated by drought stress in an ABA-dependent way, respectively. ABA was found to play active roles in regulating signaling pathways related to photosynthesis, oxidative phosphorylation (mainly related to ATP synthesis), and glutathione metabolism (involved in antioxidative reaction) in the maize response to drought stress. Our results provide an extensive dataset of ABA-dependent, drought-regulated proteins in maize plants, which may help to elucidate the underlying mechanisms of ABA-enhanced tolerance to drought stress in maize.

  15. Stomatal malfunctioning under low VPD conditions: induced by alterations in stomatal morphology and leaf anatomy or in the ABA signaling?

    PubMed

    Aliniaeifard, Sasan; Malcolm Matamoros, Priscila; van Meeteren, Uulke

    2014-12-01

    Exposing plants to low VPD reduces leaf capacity to maintain adequate water status thereafter. To find the impact of VPD on functioning of stomata, stomatal morphology and leaf anatomy, fava bean plants were grown at low (L, 0.23 kPa) or moderate (M, 1.17 kPa) VPDs and some plants that developed their leaves at moderate VPD were then transferred for 4 days to low VPD (M→L). Part of the M→L-plants were sprayed with ABA (abscisic acid) during exposure to L. L-plants showed bigger stomata, larger pore area, thinner leaves and less spongy cells compared with M-plants. Stomatal morphology (except aperture) and leaf anatomy of the M→L-plants were almost similar to the M-plants, while their transpiration rate and stomatal conductance were identical to that of L-plants. The stomatal response to ABA was lost in L-plants, but also after 1-day exposure of M-plants to low VPD. The level of foliar ABA sharply decreased within 1-day exposure to L, while the level of ABA-GE (ABA-glucose ester) was not affected. Spraying ABA during the exposure to L prevented loss of stomatal closing response thereafter. The effect of low VPD was largely depending on exposure time: the stomatal responsiveness to ABA was lost after 1-day exposure to low VPD, while the responsiveness to desiccation was gradually lost during 4-day exposure to low VPD. Leaf anatomical and stomatal morphological alterations due to low VPD were not the main cause of loss of stomatal closure response to closing stimuli.

  16. Quantitative Proteomic Analyses Identify ABA-Related Proteins and Signal Pathways in Maize Leaves under Drought Conditions

    PubMed Central

    Zhao, Yulong; Wang, Yankai; Yang, Hao; Wang, Wei; Wu, Jianyu; Hu, Xiuli

    2016-01-01

    Drought stress is one of major factors resulting in maize yield loss. The roles of abscisic acid (ABA) have been widely studied in crops in response to drought stress. However, more attention is needed to identify key ABA-related proteins and also gain deeper molecular insights about drought stress in maize. Based on this need, the physiology and proteomics of the ABA-deficient maize mutant vp5 and its wild-type Vp5 under drought stress were examined and analyzed. Malondialdehyde content increased and quantum efficiency of photosystem II decreased under drought stress in both genotypes. However, the magnitude of the increase or decrease was significantly higher in vp5 than in Vp5. A total of 7051 proteins with overlapping expression patterns among three replicates in the two genotypes were identified by Multiplex run iTRAQ-based quantitative proteomic and liquid chromatography-tandem mass spectrometry methods, of which the expression of only 150 proteins (130 in Vp5, 27 in vp5) showed changes of at least 1.5-fold under drought stress. Among the 150 proteins, 67 and 60 proteins were up-regulated and down-regulated by drought stress in an ABA-dependent way, respectively. ABA was found to play active roles in regulating signaling pathways related to photosynthesis, oxidative phosphorylation (mainly related to ATP synthesis), and glutathione metabolism (involved in antioxidative reaction) in the maize response to drought stress. Our results provide an extensive dataset of ABA-dependent, drought-regulated proteins in maize plants, which may help to elucidate the underlying mechanisms of ABA-enhanced tolerance to drought stress in maize. PMID:28008332

  17. RhHB1 mediates the antagonism of gibberellins to ABA and ethylene during rose (Rosa hybrida) petal senescence.

    PubMed

    Lü, Peitao; Zhang, Changqing; Liu, Jitao; Liu, Xiaowei; Jiang, Guimei; Jiang, Xinqiang; Khan, Muhammad Ali; Wang, Liangsheng; Hong, Bo; Gao, Junping

    2014-05-01

    Rose (Rosa hybrida) is one of the most important ornamental plants worldwide; however, senescence of its petals terminates the ornamental value of the flower, resulting in major economic loss. It is known that the hormones abscisic acid (ABA) and ethylene promote petal senescence, while gibberellins (GAs) delay the process. However, the molecular mechanisms underlying the antagonistic effects amongst plant hormones during petal senescence are still unclear. Here we isolated RhHB1, a homeodomain-leucine zipper I transcription factor gene, from rose flowers. Quantitative RT-PCR and GUS reporter analyses showed that RhHB1 was strongly expressed in senescing petals, and its expression was induced by ABA or ethylene in petals. ABA or ethylene treatment clearly accelerated rose petal senescence, while application of the gibberellin GA3 delayed the process. However, silencing of RhHB1 delayed the ABA- or ethylene-mediated senescence, and resulted in higher petal anthocyanin levels and lower expression of RhSAG12. Moreover, treatment with paclobutrazol, an inhibitor of GA biosynthesis, repressed these delays. In addition, silencing of RhHB1 blocked the ABA- or ethylene-induced reduction in expression of the GA20 oxidase encoded by RhGA20ox1, a gene in the GA biosynthetic pathway. Furthermore, RhHB1 directly binds to the RhGA20ox1 promoter, and silencing of RhGA20ox1 promoted petal senescence. Eight senescence-related genes showed substantial differences in expression in petals after treatment with GA3 or paclobutrazol. These results suggest that RhHB1 mediates the antagonistic effect of GAs on ABA and ethylene during rose petal senescence, and that the promotion of petal senescence by ABA or ethylene operates through an RhHB1-RhGA20ox1 regulatory checkpoint.

  18. The evolution of the role of ABA in the regulation of water-use efficiency: From biochemical mechanisms to stomatal conductance.

    PubMed

    Negin, Boaz; Moshelion, Menachem

    2016-10-01

    Abscisic acid is found in a wide variety of organisms. In the plant kingdom, ABA's role in mediating responses to abiotic stress has been conserved and enhanced throughout evolution. The emergence of plants to terrestrial environments required the development of mechanisms to cope with ongoing and severe abiotic stress such as drought and rapid changes in humidity and temperature. The common understanding is that terrestrial plants evolved strategies ranging from desiccation-tolerance mechanisms (mosses) to drought tolerance (CAM plants), to better exploit different ecological niches. In between these divergent water regulation strategies, ABA plays a significant role in managing plants' adaptation to new environments by optimizing water-use efficiency (WUE) under particular environmental conditions. ABA plays some very different roles in the regulation of WUE. ABA's role in the regulation of guard cells and transpiration has yielded a wide variety of WUE-regulation mechanisms, ranging from no sensitivity (ferns) to low sensitivity (anisohydric behavior) to hypersensitivity to ABA (isohydric behavior and putatively CAM plants). ABA also plays a role in the regulation of non-stomatal, biochemical mechanisms of WUE regulation. In angiosperms, this includes the control of osmotic adjustment and morphological changes, including changes in leaf size, stomatal density, stomatal size and root development. Under severe stress, ABA also appears to initiate leaf senescence via transcriptional regulation, to directly inhibit photosynthesis.

  19. The AvrB_AvrC domain of AvrXccC of Xanthomonas campestris pv. campestris is required to elicit plant defense responses and manipulate ABA homeostasis.

    PubMed

    Ho, Yi-Ping; Tan, Choon Meng; Li, Meng-Ying; Lin, Hong; Deng, Wen-Ling; Yang, Jun-Yi

    2013-04-01

    Plant disease induced by Xanthomonas campestris pv. campestris depends on type III effectors but the molecular basis is poorly understood. Here, AvrXccC8004 was characterized, and it was found that the AvrB_AvrC domain was essential and sufficient to elicit defense responses in an Arabidopsis-resistant ecotype (Col-0). An upregulation of genes in responding to the AvrB_AvrC domain of AvrXccC8004 was shown in a profile of host gene expression. The molecular changes were correlated with morphological changes observed in phenotypic and ultrastructural characterizations. Interestingly, the abscisic acid (ABA)-signaling pathway was also a prominent target for the AvrB_AvrC domain of AvrXccC8004. The highly elicited NCED5, encoding a key enzyme of ABA biosynthesis, was increased in parallel with ABA levels in AvrXccC8004 transgenic plants. Consistently, the X. campestris pv. campestris 8004 ΔavrXccC mutant was severely impaired in the ability to manipulate the accumulation of ABA and induction of ABA-related genes in challenged leaves. Moreover, exogenous application of ABA also enhanced the susceptibility of Arabidopsis to the X. campestris pv. campestris strains. These results indicate that the AvrB_AvrC domain of AvrXccC8004 alone has the activity to manipulate ABA homeostasis, which plays an important role in regulating the interactions of X. campestris pv. campestris and Arabidopsis.

  20. Movement of abscisic acid into the apoplast in response to water stress in Xanthium strumarium L

    SciTech Connect

    Cornish, K.; Zeevaart, J.A.D.

    1985-07-01

    The effect of water stress on the redistribution of abscisic acid (ABA) in mature leaves of Xanthium strumarium L. was investigated using a pressure dehydration technique. In both turgid and stressed leaves, the ABA in the xylem exudate, the apoplastic ABA, increased before bulk leaf stress-induced ABA accumulation began. In the initially turgid leaves, the ABA level remained constant in both the apoplast and the leaf as a whole until wilting symptoms appeared. Following turgor loss, sufficient quantities of ABA moved into the apoplast to stimulate stomatal closure. Thus, the initial increase of apoplastic ABA may be relevant to the rapid stomatal closure seen in stressed leaves before their bulk leaf ABA levels rise. Following recovery from water stress, elevated levels of ABA remained in the apoplast after the bulk leaf contents had returned to their prestress values. This apoplastic ABA may retard stomatal reopening during the initial recovery period. 32 references, 5 figures.

  1. Differential expression of several xyloglucan endotransglucosylase/hydrolase genes regulates flower opening and petal abscission in roses

    PubMed Central

    Singh, Amar Pal; Dubey, Shveta; Lakhwani, Deepika; Pandey, Saurabh Prakash; Khan, Kasim; Dwivedi, Upendra Nath; Nath, Pravendra; Sane, Aniruddha P.

    2013-01-01

    Flower opening is a process that requires movement of petals from a closed position to a horizontal open position, while petal abscission requires cell-wall disassembly. Both processes are controlled by ethylene and require cell-wall modification at the junction (abscission zone) of the petal and thalamus to facilitate the movement or separation of petals. In the present study, a family of xyloglucan endotransglucosylase/hydrolase (XTH) genes was studied to understand their role in petal abscission in flowers of Rosa bourboniana (ethylene sensitive, early abscising) and Rosa hybrida (less ethylene sensitive, late abscising). Transcriptome sequencing of petal abscission zone cDNA was performed at different time points (ethylene treated and untreated) and screened for XTH genes. The study identified nine new XTH genes that showed differential changes in gene expression during flower opening and abscission. Of these, RbXTH3, RbXTH5, RbXTH6 and RbXTH12 were rapidly induced by ethylene within 1–4 h of ethylene treatment, corresponding to the period of flower opening. These genes also showed an early up-regulation during flower opening under ethylene-untreated (field abscission) conditions, indicating a possible role in anthesis and petal movement during flower opening. Other genes such as RbXTH4 and RbXTH9 were up-regulated later at 8–12 h after ethylene treatment and at 24–36 h under natural abscission conditions, indicating a possible role in abscission. Treatment with a higher ethylene dose (15 µL L−1 ethylene) accelerated abscission, leading to higher steady-state levels of XTH gene transcripts at an earlier time point compared with 0.5 µL L−1 ethylene. In contrast, transcript accumulation of most of the XTHs was considerably delayed in the late-abscising rose, R. hybrida, in keeping with the slower flower opening and delayed petal abscission. The results suggest coordinated action of different XTHs in cell-wall modification of xyloglucan moieties during

  2. Abscisic Acid Synthesis and Response

    PubMed Central

    Finkelstein, Ruth

    2013-01-01

    Abscisic acid (ABA) is one of the “classical” plant hormones, i.e. discovered at least 50 years ago, that regulates many aspects of plant growth and development. This chapter reviews our current understanding of ABA synthesis, metabolism, transport, and signal transduction, emphasizing knowledge gained from studies of Arabidopsis. A combination of genetic, molecular and biochemical studies has identified nearly all of the enzymes involved in ABA metabolism, almost 200 loci regulating ABA response, and thousands of genes regulated by ABA in various contexts. Some of these regulators are implicated in cross-talk with other developmental, environmental or hormonal signals. Specific details of the ABA signaling mechanisms vary among tissues or developmental stages; these are discussed in the context of ABA effects on seed maturation, germination, seedling growth, vegetative stress responses, stomatal regulation, pathogen response, flowering, and senescence. PMID:24273463

  3. Arabidopsis LOS5/ABA3 overexpression in transgenic tobacco (Nicotiana tabacum cv. Xanthi-nc) results in enhanced drought tolerance.

    PubMed

    Yue, Yuesen; Zhang, Mingcai; Zhang, Jiachang; Duan, Liusheng; Li, Zhaohu

    2011-10-01

    Drought is a major environmental stress factor that affects growth and development of plants. Abscisic acid (ABA), osmotically active compounds, and synthesis of specific proteins, such as proteins that scavenge oxygen radicals, are crucial for plants to adapt to water deficit. LOS5/ABA3 (LOS5) encodes molybdenum-cofactor sulfurase, which is a key regulator of ABA biosynthesis. We overexpressed LOS5 in tobacco using Agrobacterium-mediated transformation. Detached leaves of LOS5-overexpressing seedlings showed lower transpirational water loss than that of nontransgenic seedlings in the same period under normal conditions. When subjected to water-deficit stress, transgenic plants showed less wilting, maintained higher water content and better cellular membrane integrity, accumulated higher quantities of ABA and proline, and exhibited higher activities of antioxidant enzymes, i.e., superoxide dismutase, catalase, peroxidase and ascorbate peroxidase, as compared with control plants. Furthermore, LOS5-overexpressing plants treated with 30% polyethylene glycol showed similar performance in cellular membrane protection, ABA and proline accumulation, and activities of catalase and peroxidase to those under drought stress. Thus, overexpression of LOS5 in transgenic tobacco can enhance drought tolerance.

  4. Hormone profiling and transcription analysis reveal a major role of ABA in tomato salt tolerance.

    PubMed

    Yang, Rongchao; Yang, Ting; Zhang, Haijun; Qi, Yan; Xing, Yanxia; Zhang, Na; Li, Ren; Weeda, Sarah; Ren, Shuxin; Ouyang, Bo; Guo, Yang-Dong

    2014-04-01

    The response and adaptation of plants to different environmental stresses are of great interest as they provide the key to understanding the mechanisms underlying stress tolerance. In this study, the changing patterns of four endogenous hormones and various physiological and biochemical parameters of both a salt-tolerant (LA2711) and a salt-sensitive (ZS-5) tomato cultivar were examined under salt stress and non-stress conditions. Additionally, the transcription of key genes in the abscisic acid (ABA) biosynthesis and metabolism were analyzed at different time points. The results indicated that gene expression responsible for ABA biosynthesis and metabolism coincided with the hormone level, and SlNCED1 and SlCYP707A3 may play major roles in the process. LA2711 performed superior to ZS-5 on various parameters, including seed germination, Na(+) compartmentation, selective absorption of K(+), and antioxidant enzymes activity. The difference in salt tolerance between the two genotypes could be attributed to the different levels of ABA due to differences in gene expression of key genes in ABA biosynthesis and metabolism. Although gibberellin, cytokinin and auxin were involved, our results indicated that ABA signaling plays a major role in tomato salt tolerance. As compared to ZS-5, LA2711 had a higher capability to selectively absorb and redistribute K(+) and a higher tolerance to Na(+) in young leaves, which may be the main physiological mechanisms of salt tolerance.

  5. Registration of Zak ERA8 soft white spring wheat germplasm with enhanced response to ABA and increased seed dormancy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    ZakERA8 is a unique mutant line selected from mutagenized soft white spring 'Zak' that has increased seed dormancy as a result of enhanced responsiveness to the plant hormone abscisic acid (ABA) during germination. This germplasm was developed by USDA-ARS, Pullman, WA in collaboration with Washingt...

  6. Increased ABA sensitivity results in higher seed dormancy in soft white spring wheat cultivar ‘Zak’

    Technology Transfer Automated Retrieval System (TEKTRAN)

    As a strategy to increase the seed dormancy of soft white wheat, mutants with increased sensitivity to the plant hormone abscisic acid (ABA) were identified in mutagenized grain of soft white spring wheat ‘Zak”. Lack of seed dormancy is correlated with increased susceptibility to preharvest sprouti...

  7. AtRAV and AtbZIP transcription factors positively regulate ABA responses: Overexpression in cotton enhances drought stress adaptation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Drought tolerance is an important trait being pursued by the agbiotech industry. Abscisic acid (ABA) is a stress hormone that mediates a multitude of processes in growth and development, water use efficiency, and gene expression during seed development and in response to environmental stresses. Ar...

  8. ABA-dependent control of GIGANTEA signalling enables drought escape via up-regulation of FLOWERING LOCUS T in Arabidopsis thaliana

    PubMed Central

    Riboni, Matteo; Robustelli Test, Alice; Galbiati, Massimo; Tonelli, Chiara; Conti, Lucio

    2016-01-01

    One strategy deployed by plants to endure water scarcity is to accelerate the transition to flowering adaptively via the drought escape (DE) response. In Arabidopsis thaliana, activation of the DE response requires the photoperiodic response gene GIGANTEA (GI) and the florigen genes FLOWERING LOCUS T (FT) and TWIN SISTER OF FT (TSF). The phytohormone abscisic acid (ABA) is also required for the DE response, by promoting the transcriptional up-regulation of the florigen genes. The mode of interaction between ABA and the photoperiodic genes remains obscure. In this work we use a genetic approach to demonstrate that ABA modulates GI signalling and consequently its ability to activate the florigen genes. We also reveal that the ABA-dependent activation of FT, but not TSF, requires CONSTANS (CO) and that impairing ABA signalling dramatically reduces the expression of florigen genes with little effect on the CO transcript profile. ABA signalling thus has an impact on the core genes of photoperiodic signalling GI and CO by modulating their downstream function and/or activities rather than their transcript accumulation. In addition, we show that as well as promoting flowering, ABA simultaneously represses flowering, independent of the florigen genes. Genetic analysis indicates that the target of the repressive function of ABA is the flowering-promoting gene SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1), a transcription factor integrating floral cues in the shoot meristem. Our study suggests that variations in ABA signalling provide different developmental information that allows plants to co-ordinate the onset of the reproductive phase according to the available water resources. PMID:27733440

  9. Overexpression of an ABA biosynthesis gene using a stress-inducible promoter enhances drought resistance in petunia.

    PubMed

    Estrada-Melo, Alejandro C; Chao; Reid, Michael S; Jiang, Cai-Zhong

    2015-01-01

    The response of plants to drought stress includes reduced transpiration as stomates close in response to increased abscisic acid (ABA) concentrations. Constitutive overexpression of 9-cis-epoxycarotenoid dioxygenase (NCED), a key enzyme in ABA biosynthesis, increases drought resistance, but causes negative pleiotropic effects on plant growth and development. We overexpressed the tomato NCED (LeNCED1) in petunia plants under the control of a stress-inducible promoter, rd29A. Under water stress, the transgenic plants had increased transcripts of NCED mRNA, elevated leaf ABA concentrations, increased concentrations of proline, and a significant increase in drought resistance. The transgenic plants also displayed the expected decreases in stomatal conductance, transpiration, and photosynthesis. After 14 days without water, the control plants were dead, but the transgenic plants, though wilted, recovered fully when re-watered. Well-watered transgenic plants grew like non-transformed control plants and there was no effect of the transgene on seed dormancy.

  10. Overexpression of an ABA biosynthesis gene using a stress-inducible promoter enhances drought resistance in petunia

    PubMed Central

    Estrada-Melo, Alejandro C; Chao; Reid, Michael S; Jiang, Cai-Zhong

    2015-01-01

    The response of plants to drought stress includes reduced transpiration as stomates close in response to increased abscisic acid (ABA) concentrations. Constitutive overexpression of 9-cis-epoxycarotenoid dioxygenase (NCED), a key enzyme in ABA biosynthesis, increases drought resistance, but causes negative pleiotropic effects on plant growth and development. We overexpressed the tomato NCED (LeNCED1) in petunia plants under the control of a stress-inducible promoter, rd29A. Under water stress, the transgenic plants had increased transcripts of NCED mRNA, elevated leaf ABA concentrations, increased concentrations of proline, and a significant increase in drought resistance. The transgenic plants also displayed the expected decreases in stomatal conductance, transpiration, and photosynthesis. After 14 days without water, the control plants were dead, but the transgenic plants, though wilted, recovered fully when re-watered. Well-watered transgenic plants grew like non-transformed control plants and there was no effect of the transgene on seed dormancy. PMID:26504568

  11. Increasing abscisic acid levels by immunomodulation in barley grains induces precocious maturation without changing grain composition.

    PubMed

    Staroske, Nicole; Conrad, Udo; Kumlehn, Jochen; Hensel, Götz; Radchuk, Ruslana; Erban, Alexander; Kopka, Joachim; Weschke, Winfriede; Weber, Hans

    2016-04-01

    Abscisic acid (ABA) accumulates in seeds during the transition to the seed filling phase. ABA triggers seed maturation, storage activity, and stress signalling and tolerance. Immunomodulation was used to alter the ABA status in barley grains, with the resulting transgenic caryopses responding to the anti-ABA antibody gene expression with increased accumulation of ABA. Calculation of free versus antibody-bound ABA reveals large excess of free ABA, increasing signficantly in caryopses from 10 days after fertilization. Metabolite and transcript profiling in anti-ABA grains expose triggered and enhanced ABA-functions such as transcriptional up-regulation of sucrose-to-starch metabolism, storage protein synthesis and ABA-related signal transduction. Thus, enhanced ABA during transition phases induces precocious maturation but negatively interferes with growth and development. Anti-ABA grains display broad constitutive gene induction related to biotic and abiotic stresses. Most of these genes are ABA- and/or stress-inducible, including alcohol and aldehyde dehydrogenases, peroxidases, chaperones, glutathione-S-transferase, drought- and salt-inducible proteins. Conclusively, ABA immunomodulation results in precocious ABA accumulation that generates an integrated response of stress and maturation. Repression of ABA signalling, occurring in anti-ABA grains, potentially antagonizes effects caused by overshooting production. Finally, mature grain weight and composition are unchanged in anti-ABA plants, although germination is somewhat delayed. This indicates that anti-ABA caryopses induce specific mechanisms to desensitize ABA signalling efficiently, which finally yields mature grains with nearly unchanged dry weight and composition. Such compensation implicates the enormous physiological and metabolic flexibilities of barley grains to adjust effects of unnaturally high ABA amounts in order to ensure and maintain proper grain development.

  12. Immunolocalization of IAA and ABA in roots and needles of radiata pine (Pinus radiata) during drought and rewatering.

    PubMed

    De Diego, N; Rodríguez, J L; Dodd, I C; Pérez-Alfocea, F; Moncaleán, P; Lacuesta, M

    2013-05-01

    Anatomical, physiological and phytohormonal changes involved in drought tolerance were examined in different Pinus radiata D. Don breeds subjected to soil drying and rewatering. Breeds with the smallest stomatal chamber size had the lowest transpiration rate and the highest intrinsic water-use efficiency. Xylem cell size was positively correlated with leaf hydraulic conductance and needle indole-3-acetic acid (IAA) concentrations, whereas transpiration rate was negatively correlated with needle abscisic acid (ABA) levels. Since these two phytohormones seem important in regulating the P. radiata drought response, they were simultaneously immunolocalized in roots and needles of the most tolerant breed (P. radiata var. radiata × var. cedrosensis) during two sequential drought cycles and after rewatering. During drought, IAA was unequally distributed into the pointed area of the needle cross-section and mainly located in mesophyll and vascular tissue cells of needles, possibly inducing needle epinasty, whereas ABA was principally located in guard cells, presumably to elicit stomata closure. In the roots, at the end of the first drought cycle, while strong IAA accumulation was observed in the cortex, ABA levels decreased probably due to translocation to the leaves. Rewatering modified the distribution of both IAA and ABA in the needles, causing an accumulation principally in vascular tissue, with residual concentrations in mesophyll, likely favouring the acclimatization of the plants for further drought cycles. Contrarily, in the roots IAA and ABA were located in the exodermis, a natural barrier that regulates the phytohormone translocation to other plant tissues and hormone losses to the soil solution after rewatering. These results confirm that immunolocalization is an efficient tool to understand the translocation of IAA and ABA in plants subjected to different water stress situations, and clarify their role in regulating physiological responses such as stomata

  13. ALA Inhibits ABA-induced Stomatal Closure via Reducing H2O2 and Ca2+ Levels in Guard Cells

    PubMed Central

    An, Yuyan; Liu, Longbo; Chen, Linghui; Wang, Liangju

    2016-01-01

    5-Aminolevulinic acid (ALA), a newly proved natural plant growth regulator, is well known to improve plant photosynthesis under both normal and stressful conditions. However, its underlying mechanism remains largely unknown. Stomatal closure is one of the major limiting factors for photosynthesis and abscisic acid (ABA) is the most important hormone in provoking stomatal closing. Here, we showed that ALA significantly inhibited ABA-induced stomatal closure using wild-type and ALA-overproducing transgenic Arabidopsis (YHem1). We found that ALA decreased ABA-induced H2O2 and cytosolic Ca2+ accumulation in guard cells with stomatal bioassay, laser-scanning confocal microscopy and pharmacological methods. The inhibitory effect of ALA on ABA-induced stomatal closure was similar to that of AsA (an important reducing substrate for H2O2 removal), CAT (a H2O2-scavenging enzyme), DPI (an inhibitor of the H2O2-generating NADPH oxidase), EGTA (a Ca-chelating agent), and AlCl3 (an inhibitor of calcium channel). Furthermore, ALA inhibited exogenous H2O2- or Ca2+-induced stomatal closure. Taken together, we conclude that ALA inhibits ABA-induced stomatal closure via reducing H2O2, probably by scavenging, and Ca2+ levels in guard cells. Moreover, the inhibitive effect of ALA on ABA-induced stomatal closure was further confirmed in the whole plant. Finally, we demonstrated that ALA inhibits stomatal closing, but significantly improves plant drought tolerance. Our results provide valuable information for the promotion of plant production and development of a sustainable low-carbon society. PMID:27148309

  14. BnSIP1-1, a Trihelix Family Gene, Mediates Abiotic Stress Tolerance and ABA Signaling in Brassica napus

    PubMed Central

    Luo, Junling; Tang, Shaohua; Mei, Fengling; Peng, Xiaojue; Li, Jun; Li, Xiaofei; Yan, Xiaohong; Zeng, Xinhua; Liu, Fang; Wu, Yuhua; Wu, Gang

    2017-01-01

    The trihelix family genes have important functions in light-relevant and other developmental processes, but their roles in response to adverse environment are largely unclear. In this study, we identified a new gene, BnSIP1-1, which fell in the SIP1 (6b INTERACTING PROTEIN1) clade of the trihelix family with two trihelix DNA binding domains and a fourth amphipathic α-helix. BnSIP1-1 protein specifically targeted to the nucleus, and its expression can be induced by abscisic acid (ABA) and different stresses. Overexpression of BnSIP1-1 improved seed germination under osmotic pressure, salt, and ABA treatments. Moreover, BnSIP1-1 decreased the susceptibility of transgenic seedlings to osmotic pressure and ABA treatments, whereas there was no difference under salt stress between the transgenic and wild-type seedlings. ABA level in the transgenic seedlings leaves was higher than those in the control plants under normal condition. Under exogenous ABA treatment and mannitol stress, the accumulation of ABA in the transgenic plants was higher than that in the control plants; while under salt stress, the difference of ABA content before treatment was gradually smaller with the prolongation of salt treatment time, then after 24 h of treatment the ABA level was similar in transgenic and wild-type plants. The transcription levels of several general stress marker genes (BnRD29A, BnERD15, and BnLEA1) were higher in the transgenic plants than the wild-type plants, whereas salt-responsive genes (BnSOS1, BnNHX1, and BnHKT) were not significantly different or even reduced compared with the wild-type plants, which indicated that BnSIP1-1 specifically exerted different regulatory mechanisms on the osmotic- and salt-response pathways in seedling period. Overall, these findings suggested that BnSIP1-1 played roles in ABA synthesis and signaling, salt and osmotic stress response. To date, information about the involvement of the Brassica napus trihelix gene in abiotic response is scarce

  15. Isohydric and anisohydric strategies of wheat genotypes under osmotic stress: biosynthesis and function of ABA in stress responses.

    PubMed

    Gallé, Ágnes; Csiszár, Jolán; Benyó, Dániel; Laskay, Gábor; Leviczky, Tünde; Erdei, László; Tari, Irma

    2013-11-01

    Changes in water potential (ψw), stomatal conductance, abscisic acid (ABA) accumulation, expression of the major genes involved in ABA biosynthesis, activities of abscisic aldehyde oxidase (AO, EC 1.2.3.1) and antioxidant enzymes were studied in two wheat cultivars with contrasting acclimation strategies subjected to medium strength osmotic stress (-0.976MPa) induced by polyethylene glycol (PEG 6000). Because the biosynthetic pathway of ABA involves multiple gene products, the aim of this study was to unravel how these genes are regulated in isohydric and anisohydric wheat genotypes. In the root tissues of the isohydric cultivar, Triticum aestivum cv. Kobomugi, osmotic stress increased the transcript levels of 9-cis-epoxycarotenoid dioxygenase (NCED) gene, controlling the rate limiting step of ABA biosynthesis. Moreover, this cultivar exhibited a higher basal activity and a higher induction of aldehyde oxidase isoenzymes (AAO2-AAO3), responsible for converting ABAldehyde to ABA. It was found that the fast activation of the ABA biosynthesis in the roots generated an enhanced ABA pool in the shoot, which brought about a faster closure of the stomata upon increasing osmotic stress and, as a result, the plants could maintain ψw in the tissues close to the control level. In contrast, the anisohydric genotype, cv. GK Öthalom, exhibited a moderate induction of ABA biosynthesis in the roots, leading to the maintenance but no increase in the concentration of ABA on the basis of tissue water content in the leaves. Due to the slower response of their stomata to water deficit, the tissues of cv. GK Öthalom have to acclimate to much more negative water potentials during increasing osmotic stress. A decreased activity of superoxide dismutase (SOD) was found in the leaves and roots of both cultivars exposed to osmotic stress, but in the roots elevated activities of catalase (CAT), peroxidase (POX), glutathione reductase (GR) and glutathione transferase (GST) were detected in

  16. Identification and molecular characterization of an IDA-like gene from litchi, LcIDL1, whose ectopic expression promotes floral organ abscission in Arabidopsis

    PubMed Central

    Ying, Peiyuan; Li, Caiqin; Liu, Xuncheng; Xia, Rui; Zhao, Minglei; Li, Jianguo

    2016-01-01

    Unexpected abscission of flowers or fruits is a major limiting factor for crop productivity. Key genes controlling abscission in plants, especially in popular fruit trees, are largely unknown. Here we identified a litchi (Litchi chinensis Sonn.) IDA-like (INFLORESCENCE DEFICIENT IN ABSCISSION-like) gene LcIDL1 as a potential key regulator of abscission. LcIDL1 encodes a peptide that shows the closest homology to Arabidopsis IDA, and is localized in cell membrane and cytoplasm. Real-time PCR analysis showed that the expression level of LcIDL1 accumulated gradually following flower abscission, and it was obviously induced by fruit abscission-promoting treatments. Transgenic plants expressing LcIDL1 in Arabidopsis revealed a role of LcIDL1 similar to IDA in promoting floral organ abscission. Moreover, ectopic expression of LcIDL1 in Arabidopsis activated the expression of abscission-related genes. Taken together, our findings provide evidence that LcIDL1 may act as a key regulator in control of abscission. PMID:27845425

  17. Proteomic analysis of B-aminobutyric acid priming and aba-induction of drought resistance in crabapple (Malus pumila): effect on general metabolism, the phenylpropanoid pathway and cell wall enzymes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In a variety of annual crops and model plants, the xenobiotic compound, DL-beta-aminobutyric acid (BABA), has been shown to enhance disease resistance and increase salt, drought, and thermotolerance. BABA does not activate stress genes directly but rather sensitizes plants to respond more quickly a...

  18. Stamen Abscission Zone Transcriptome Profiling Reveals New Candidates for Abscission Control: Enhanced Retention of Floral Organs in Transgenic Plants Overexpressing Arabidopsis ZINC FINGER PROTEIN21[C][W][OA

    PubMed Central

    Cai, Suqin; Lashbrook, Coralie C.

    2008-01-01

    Organ detachment requires cell separation within abscission zones (AZs). Physiological studies have established that ethylene and auxin contribute to cell separation control. Genetic analyses of abscission mutants have defined ethylene-independent detachment regulators. Functional genomic strategies leading to global understandings of abscission have awaited methods for isolating AZ cells of low abundance and very small size. Here, we couple laser capture microdissection of Arabidopsis thaliana stamen AZs and GeneChip profiling to reveal the AZ transcriptome responding to a developmental shedding cue. Analyses focus on 551 AZ genes (AZ551) regulated at the highest statistical significance (P ≤ 0.0001) over five floral stages linking prepollination to stamen shed. AZ551 includes mediators of ethylene and auxin signaling as well as receptor-like kinases and extracellular ligands thought to act independent of ethylene. We hypothesized that novel abscission regulators might reside in disproportionately represented Gene Ontology Consortium functional categories for cell wall modifying proteins, extracellular regulators, and nuclear-residing transcription factors. Promoter-β-glucuronidase expression of one transcription factor candidate, ZINC FINGER PROTEIN2 (AtZFP2), was elevated in stamen, petal, and sepal AZs. Flower parts of transgenic lines overexpressing AtZFP2 exhibited asynchronous and delayed abscission. Abscission defects were accompanied by altered floral morphology limiting pollination and fertility. Hand-pollination restored transgenic fruit development but not the rapid abscission seen in wild-type plants, demonstrating that pollination does not assure normal rates of detachment. In wild-type stamen AZs, AtZFP2 is significantly up-regulated postanthesis. Phenotype data from transgene overexpression studies suggest that AtZFP2 participates in processes that directly or indirectly influence organ shed. PMID:18192438

  19. The Phytotoxin Coronatine Induces Abscission-Related Gene Expression and Boll Ripening during Defoliation of Cotton

    PubMed Central

    Tian, Xiaoli; Duan, Liusheng; Zhang, Mingcai; Tan, Weiming; Xu, Dongyong; Li, Zhaohu

    2014-01-01

    Defoliants can increase machine harvest efficiency of cotton (Gossypium hirusutum L.), prevent lodging and reduce the time from defoliation to harvest. Coronatine (COR) is a chlorosis-inducing non-host-specific phytotoxin that induces leaf and/or fruit abscission in some crops. The present study investigates how COR might induce cotton leaf abscission by modulating genes involved in cell wall hydrolases and ACC (ethylene precursor) in various cotton tissues. The effects of COR on cotton boll ripening, seedcotton yield, and seed development were also studied. After 14 d of treatment with COR, cells within the leaf abscission zone (AZ) showed marked differentiation. Elevated transcripts of GhCEL1, GhPG and GhACS were observed in the AZs treated with COR and Thidiazuron (TDZ). The relative expression of GhCEL1 and GhACS in TDZ treated plants was approximately twice that in plants treated with COR for 12 h. However, only GhACS expression increased in leaf blade and petiole. There was a continuous increase in the activity of hydrolytic enzymes such as cellulase (CEL) and polygalacturonase (PG), and ACC accumulation in AZs following COR and TDZ treatments, but there was greater increase in ACC activity of COR treated boll crust, indicating that COR had greater ripening effect than TDZ. Coronatine significantly enhanced boll opening without affecting boll weight, lint percentage and seed quality. Therefore, COR can be a potential cotton defoliant with different physiological mechanism of action from the currently used TDZ. PMID:24845465

  20. The phytotoxin coronatine induces abscission-related gene expression and boll ripening during defoliation of cotton.

    PubMed

    Du, Mingwei; Li, Yi; Tian, Xiaoli; Duan, Liusheng; Zhang, Mingcai; Tan, Weiming; Xu, Dongyong; Li, Zhaohu

    2014-01-01

    Defoliants can increase machine harvest efficiency of cotton (Gossypium hirusutum L.), prevent lodging and reduce the time from defoliation to harvest. Coronatine (COR) is a chlorosis-inducing non-host-specific phytotoxin that induces leaf and/or fruit abscission in some crops. The present study investigates how COR might induce cotton leaf abscission by modulating genes involved in cell wall hydrolases and ACC (ethylene precursor) in various cotton tissues. The effects of COR on cotton boll ripening, seedcotton yield, and seed development were also studied. After 14 d of treatment with COR, cells within the leaf abscission zone (AZ) showed marked differentiation. Elevated transcripts of GhCEL1, GhPG and GhACS were observed in the AZs treated with COR and Thidiazuron (TDZ). The relative expression of GhCEL1 and GhACS in TDZ treated plants was approximately twice that in plants treated with COR for 12 h. However, only GhACS expression increased in leaf blade and petiole. There was a continuous increase in the activity of hydrolytic enzymes such as cellulase (CEL) and polygalacturonase (PG), and ACC accumulation in AZs following COR and TDZ treatments, but there was greater increase in ACC activity of COR treated boll crust, indicating that COR had greater ripening effect than TDZ. Coronatine significantly enhanced boll opening without affecting boll weight, lint percentage and seed quality. Therefore, COR can be a potential cotton defoliant with different physiological mechanism of action from the currently used TDZ.

  1. Mechanistic insight into a peptide hormone signaling complex mediating floral organ abscission

    PubMed Central

    Santiago, Julia; Brandt, Benjamin; Wildhagen, Mari; Hohmann, Ulrich; Hothorn, Ludwig A; Butenko, Melinka A; Hothorn, Michael

    2016-01-01

    Plants constantly renew during their life cycle and thus require to shed senescent and damaged organs. Floral abscission is controlled by the leucine-rich repeat receptor kinase (LRR-RK) HAESA and the peptide hormone IDA. It is unknown how expression of IDA in the abscission zone leads to HAESA activation. Here we show that IDA is sensed directly by the HAESA ectodomain. Crystal structures of HAESA in complex with IDA reveal a hormone binding pocket that accommodates an active dodecamer peptide. A central hydroxyproline residue anchors IDA to the receptor. The HAESA co-receptor SERK1, a positive regulator of the floral abscission pathway, allows for high-affinity sensing of the peptide hormone by binding to an Arg-His-Asn motif in IDA. This sequence pattern is conserved among diverse plant peptides, suggesting that plant peptide hormone receptors may share a common ligand binding mode and activation mechanism. DOI: http://dx.doi.org/10.7554/eLife.15075.001 PMID:27058169

  2. Transcriptomic signatures in seeds of apple (Malus domestica L. Borkh) during fruitlet abscission.

    PubMed

    Ferrero, Sergio; Carretero-Paulet, Lorenzo; Mendes, Marta Adelina; Botton, Alessandro; Eccher, Giulia; Masiero, Simona; Colombo, Lucia

    2015-01-01

    Abscission is the regulated process of detachment of an organ from a plant. In apple the abscission of fruits occurs during their early development to control the fruit load depending on the nutritional state of the plant. In order to control production and obtain fruits with optimal market qualities, the horticultural procedure of thinning is performed to further reduce the number of fruitlets. In this study we have conducted a transcriptomic profiling of seeds from two different types of fruitlets, according to size and position in the fruit cluster. Transcriptomic profiles of central and lateral fruit seeds were obtained by RNAseq. Comparative analysis was performed by the functional categorization of differentially expressed genes by means of Gene Ontology (GO) annotation of the apple genome. Our results revealed the overexpression of genes involved in responses to stress, hormone biosynthesis and also the response and/or transport of auxin and ethylene. A smaller set of genes, mainly related to ion transport and homeostasis, were found to be down-regulated. The transcriptome characterization described in this manuscript contributes to unravelling the molecular mechanisms and pathways involved in the physiological abscission of apple fruits and suggests a role for seeds in this process.

  3. Imidazolium-Containing ABA Triblock Copolymers as Electroactive Devices.

    PubMed

    Margaretta, Evan; Fahs, Gregory B; Inglefield, David L; Jangu, Chainika; Wang, Dong; Heflin, James R; Moore, Robert B; Long, Timothy E

    2016-01-20

    Two-step reversible addition-fragmentation chain transfer (RAFT) polymerization and two subsequent postpolymerization modification steps afforded well-defined ABA triblock copolymers featuring mechanically reinforcing polystyrene outer blocks and 1-methylimidazole-neutralized poly(acrylic acid)-based central blocks. Size exclusion chromatography and (1)H NMR spectroscopy confirmed predictable molecular weights and narrow distributions. The ionic liquid (IL) 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIm][OTf]) was incorporated at 30 wt % into polymeric films. Thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis determined the thermomechanical properties of the polymers and polymer-IL composites. Atomic force microscopy, small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM) determined surface and bulk morphologies, and poly(Sty-b-AA(MeIm)-b-Sty) exhibited a change from packed cylindrical to lamellar morphology in SAXS upon IL incorporation. Electrochemical impedance spectroscopy determined the in-plane ionic conductivities of the polymer-IL membranes (σ ∼ 10(-4) S/cm). A device fabricated from poly(Sty-b-AA(MeIm)-b-Sty) with 30 wt % incorporated IL demonstrated mechanical actuation under a low applied voltage of 4 V.

  4. abaA controls phialide differentiation in Aspergillus nidulans.

    PubMed Central

    Sewall, T C; Mims, C W; Timberlake, W E

    1990-01-01

    Aspergillus nidulans is an ascomycetous fungus that reproduces asexually by forming multicellular conidiophores and uninucleate spores called conidia. Loss of function mutations in the abacus A (abaA) regulatory locus result in formation of aberrant conidiophores that fail to produce conidia. Wild-type conidiophores form two tiers of sterigmata. The first tier, metulae, divide to produce the second tier, phialides. Phialides are sporogenous cells that produce conidia through a specialized apical budding process. We have examined conidiophore development in an abaA- strain at the ultrastructural level. The results showed that in the mutant metulae produce supernumerary tiers of cells with metula-like, rather than phialide-like, properties. Temperature shift experiments with an abaA14ts strain demonstrated that abaA+ function induced phialide formation by the aberrant abacus cells and was continuously required for maintenance of phialide function. In the absence of abaA+ activity, metulae simply proliferated and later developmental steps never occurred. We conclude that abaA+ directs the differentiation of phialides and is continuously required for maintenance of their function. PMID:2152124

  5. The ABA-mediated switch between submersed and emersed life-styles in aquatic macrophytes.

    PubMed

    Wanke, Dierk

    2011-07-01

    Hydrophytes comprise aquatic macrophytes from various taxa that are able to sustain and to complete their lifecycle in a flooded environment. Their ancestors, however, underwent adaptive processes to withstand drought on land and became partially or completely independent of water for sexual reproduction. Interestingly, the step backwards into the high-density aquatic medium happened independently several times in numerous plant taxa. For flowering plants, this submersed life-style is especially difficult as they need to erect their floral organs above the water surface to be pollinated. Moreover, fresh-water plants evolved the adaptive mechanism of heterophylly, which enabled them to switch between a submersed and an emersed leaf morphology. The plant hormone abscisic acid (ABA) is a key factor of heterophylly induction in aquatic plants and is a major switch between a submersed and emersed life. The mechanisms of ABA signal perception and transduction appear to be conserved throughout the evolution of basal plants to angiosperms and from terrestrial to aquatic plants. This review summarizes the interplay of environmental factors that act through ABA to orchestrate adaptation of plants to their aquatic environment.

  6. ASG2 is a farnesylated DWD protein that acts as ABA negative regulator in Arabidopsis.

    PubMed

    Dutilleul, Christelle; Ribeiro, Iliana; Blanc, Nathalie; Nezames, Cynthia D; Deng, Xing Wang; Zglobicki, Piotr; Palacio Barrera, Ana María; Atehortùa, Lucia; Courtois, Martine; Labas, Valérie; Giglioli-Guivarc'h, Nathalie; Ducos, Eric

    2016-01-01

    The tagging-via-substrate approach designed for the capture of mammal prenylated proteins was adapted to Arabidopsis cell culture. In this way, proteins are in vivo tagged with an azide-modified farnesyl moiety and captured thanks to biotin alkyne Click-iT® chemistry with further streptavidin-affinity chromatography. Mass spectrometry analyses identified four small GTPases and ASG2 (ALTERED SEED GERMINATION 2), a protein previously associated to the seed germination gene network. ASG2 is a conserved protein in plants and displays a unique feature that associates WD40 domains and tetratricopeptide repeats. Additionally, we show that ASG2 has a C-terminal CaaX-box that is farnesylated in vitro. Protoplast transfections using CaaX prenyltransferase mutants show that farnesylation provokes ASG2 nucleus exclusion. Moreover, ASG2 interacts with DDB1 (DAMAGE DNA BINDING protein 1), and the subcellular localization of this complex depends on ASG2 farnesylation status. Finally, germination and root elongation experiments reveal that asg2 and the farnesyltransferase mutant era1 (ENHANCED RESPONSE TO ABSCISIC ACID (ABA) 1) behave in similar manners when exposed to ABA or salt stress. To our knowledge, ASG2 is the first farnesylated DWD (DDB1 binding WD40) protein related to ABA response in Arabidopsis that may be linked to era1 phenotypes.

  7. Arabidopsis cold shock domain protein 2 influences ABA accumulation in seed and negatively regulates germination.

    PubMed

    Sasaki, Kentaro; Kim, Myung-Hee; Kanno, Yuri; Seo, Mitsunori; Kamiya, Yuji; Imai, Ryozo

    2015-01-02

    The cold shock domain (CSD) is the most conserved nucleic acid binding domain and is distributed from bacteria to animals and plants. CSD proteins are RNA chaperones that destabilize RNA secondary structures to regulate stress tolerance and development. AtCSP2 is one of the four CSD proteins in Arabidopsis and is up-regulated in response to cold. Since AtCSP2 negatively regulates freezing tolerance, it was proposed to be a modulator of freezing tolerance during cold acclimation. Here, we examined the function of AtCSP2 in seed germination. We found that AtCSP2-overexpressing lines demonstrated retarded germination as compared with the wild type, with or without stress treatments. The ABA levels in AtCSP2-overexpressing seeds were higher than those in the wild type. In addition, overexpression of AtCSP2 reduced the expression of an ABA catabolic gene (CYP707A2) and gibberellin biosynthesis genes (GA20ox and GA3ox). These results suggest that AtCSP2 negatively regulates seed germination by controlling ABA and GA levels.

  8. The second step of the biphasic endosperm cap weakening that mediates tomato (Lycopersicon esculentum) seed germination is under control of ABA.

    PubMed

    Toorop, P E; van Aelst, A C; Hilhorst, H W

    2000-08-01

    The role of abscisic acid (ABA) in the weakening of the endosperm cap prior to radicle protrusion in tomato (Lycopersicon esculentum Mill. cv. Moneymaker) seeds was studied. The endosperm cap weakened substantially in both water and ABA during the first 38 h of imbibition. After 38 h the force required for endosperm cap puncturing was arrested at 0.35 N in ABA, whereas in water a further decrease occurred until the radicle protruded. During the first 2 d of imbibition endo-beta-mannanase activity was correlated with the decrease in required puncture force and with the appearance of ice-crystal-induced porosity in the cell walls as observed by scanning electron microscopy. Prolonged incubation in ABA resulted in the loss of endo-beta-mannanase activity and the loss of ice-crystal-induced porosity, but not in a reversion of the required puncture force. ABA also had a distinct but minor effect on the growth potential of the embryo. However, endosperm cap resistance played the limiting role in the completion of germination. It was concluded that (a) endosperm cap weakening is a biphasic process and (b) inhibition of germination by ABA is through the second step in the endosperm cap weakening process.

  9. AsHSP17, a creeping bentgrass small heat shock protein modulates plant photosynthesis and ABA-dependent and independent signalling to attenuate plant response to abiotic stress.

    PubMed

    Sun, Xinbo; Sun, Chunyu; Li, Zhigang; Hu, Qian; Han, Liebao; Luo, Hong

    2016-06-01

    Heat shock proteins (HSPs) are molecular chaperones that accumulate in response to heat and other abiotic stressors. Small HSPs (sHSPs) belong to the most ubiquitous HSP subgroup with molecular weights ranging from 12 to 42 kDa. We have cloned a new sHSP gene, AsHSP17 from creeping bentgrass (Agrostis stolonifera) and studied its role in plant response to environmental stress. AsHSP17 encodes a protein of 17 kDa. Its expression was strongly induced by heat in both leaf and root tissues, and by salt and abscisic acid (ABA) in roots. Transgenic Arabidopsis plants constitutively expressing AsHSP17 exhibited enhanced sensitivity to heat and salt stress accompanied by reduced leaf chlorophyll content and decreased photosynthesis under both normal and stressed conditions compared to wild type. Overexpression of AsHSP17 also led to hypersensitivity to exogenous ABA and salinity during germination and post-germinative growth. Gene expression analysis indicated that AsHSP17 modulates expression of photosynthesis-related genes and regulates ABA biosynthesis, metabolism and ABA signalling as well as ABA-independent stress signalling. Our results suggest that AsHSP17 may function as a protein chaperone to negatively regulate plant responses to adverse environmental stresses through modulating photosynthesis and ABA-dependent and independent signalling pathways.

  10. Abscisic Acid Transport in Human Erythrocytes*

    PubMed Central

    Vigliarolo, Tiziana; Guida, Lucrezia; Millo, Enrico; Fresia, Chiara; Turco, Emilia; De Flora, Antonio; Zocchi, Elena

    2015-01-01

    Abscisic acid (ABA) is a plant hormone involved in the response to environmental stress. Recently, ABA has been shown to be present and active also in mammals, where it stimulates the functional activity of innate immune cells, of mesenchymal and hemopoietic stem cells, and insulin-releasing pancreatic β-cells. LANCL2, the ABA receptor in mammalian cells, is a peripheral membrane protein that localizes at the intracellular side of the plasma membrane. Here we investigated the mechanism enabling ABA transport across the plasmamembrane of human red blood cells (RBC). Both influx and efflux of [3H]ABA occur across intact RBC, as detected by radiometric and chromatographic methods. ABA binds specifically to Band 3 (the RBC anion transporter), as determined by labeling of RBC membranes with biotinylated ABA. Proteoliposomes reconstituted with human purified Band 3 transport [3H]ABA and [35S]sulfate, and ABA transport is sensitive to the specific Band 3 inhibitor 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid. Once inside RBC, ABA stimulates ATP release through the LANCL2-mediated activation of adenylate cyclase. As ATP released from RBC is known to exert a vasodilator response, these results suggest a role for plasma ABA in the regulation of vascular tone. PMID:25847240

  11. Multiple impacts of the plant growth-promoting rhizobacterium Variovorax paradoxus 5C-2 on nutrient and ABA relations of Pisum sativum

    PubMed Central

    Dodd, Ian C.

    2012-01-01

    Resolving the physiological mechanisms by which rhizobacteria enhance plant growth is difficult, since many such bacteria contain multiple plant growth-promoting properties. To understand further how the 1-aminocyclopropane-1-carboxylate (ACC) deaminase (ACCd)-containing rhizobacterium Variovorax paradoxus 5C-2 affects plant growth, the flows and partitioning of mineral nutrients and abscisic acid (ABA) and ABA metabolism were studied in pea (Pisum sativum) plants following rhizosphere bacterial inoculation. Although root architecture was not affected, inoculation increased root and shoot biomass, and stomatal conductance, by 20, 15, and 24%, respectively, and increased N, P, K, Ca, and Mg uptake by 16, 81, 50, 46, and 58%, respectively. P deposition in inoculated plant roots was 4.9 times higher than that in uninoculated controls. Rhizobacterial inoculation increased root to shoot xylem flows and shoot to root phloem flows of K by 1.8- and 2.1-fold, respectively. In control plants, major sinks for K deposition were the roots and upper shoot (43% and 49% of total uptake, respectively), while rhizobacterial inoculation increased K distribution to the lower shoot at the expense of other compartments (xylem, phloem, and upper shoot). Despite being unable to metabolize ABA in vitro, V. paradoxus 5C-2 decreased root ABA concentrations and accumulation by 40–60%. Although inoculation decreased xylem ABA flows, phloem ABA flows increased. Whether bacterial ACCd attenuates root to shoot ABA signalling requires further investigation, since ABA is critical to maintain growth of droughted plants, and ACCd-containing organisms have been advocated as a means of minimizing growth inhibition of plants in drying soil. PMID:23136167

  12. Negative feedback regulation of ABA biosynthesis in peanut (Arachis hypogaea): a transcription factor complex inhibits AhNCED1 expression during water stress

    PubMed Central

    Liu, Shuai; Li, Meijuan; Su, Liangchen; Ge, Kui; Li, Limei; Li, Xiaoyun; Liu, Xu; Li, Ling

    2016-01-01

    Abscisic acid (ABA), a key plant stress-signaling hormone, is produced in response to drought and counteracts the effects of this stress. The accumulation of ABA is controlled by the enzyme 9-cis-epoxycarotenoid dioxygenase (NCED). In Arabidopsis, NCED3 is regulated by a positive feedback mechanism by ABA. In this study in peanut (Arachis hypogaea), we demonstrate that ABA biosynthesis is also controlled by negative feedback regulation, mediated by the inhibitory effect on AhNCED1 transcription of a protein complex between transcription factors AhNAC2 and AhAREB1. AhNCED1 was significantly down-regulated after PEG treatment for 10 h, at which time ABA content reached a peak. A ChIP-qPCR assay confirmed AhAREB1 and AhNAC2 binding to the AhNCED1 promoter in response to ABA. Moreover, the interaction between AhAREB1 and AhNAC2, and a transient expression assay showed that the protein complex could negatively regulate the expression of AhNCED1. The results also demonstrated that AhAREB1 was the key factor in AhNCED1 feedback regulation, while AhNAC2 played a subsidiary role. ABA reduced the rate of AhAREB1 degradation and enhanced both the synthesis and degradation rate of the AhNAC2 protein. In summary, the AhAREB1/AhNAC2 protein complex functions as a negative feedback regulator of drought-induced ABA biosynthesis in peanut. PMID:27892506

  13. A role for PacMYBA in ABA-regulated anthocyanin biosynthesis in red-colored sweet cherry cv. Hong Deng (Prunus avium L.).

    PubMed

    Shen, Xinjie; Zhao, Kai; Liu, Linlin; Zhang, Kaichun; Yuan, Huazhao; Liao, Xiong; Wang, Qi; Guo, Xinwei; Li, Fang; Li, Tianhong

    2014-05-01

    The MYB transcription factors and plant hormone ABA have been suggested to play a role in fruit anthocyanin biosynthesis, but supporting genetic evidence has been lacking in sweet cherry. The present study describes the first functional characterization of an R2R3-MYB transcription factor, PacMYBA, from red-colored sweet cherry cv. Hong Deng (Prunus avium L.). Transient promoter assays demonstrated that PacMYBA physically interacted with several anthocyanin-related basic helix-loop-helix (bHLH) transcription factors to activate the promoters of PacDFR, PacANS and PacUFGT, which are thought to be involved in anthocyanin biosynthesis. Furthermore, the immature seeds of transgenic Arabidopsis plants overexpressing PacMYBA exhibited ectopic pigmentation. Silencing of PacMYBA, using a Tobacco rattle virus (TRV)-induced gene silencing technique, resulted in sweet cherry fruit that lacked red pigment. ABA treatment significantly induced anthocyanin accumulation, while treatment with the ABA biosynthesis inhibitor nordihydroguaiaretic acid (NDGA) blocked anthocyanin production. PacMYBA expression peaked after 2 h of pre-incubation in ABA and was 15.2-fold higher than that of sweet cherries treated with NDGA. The colorless phenotype was also observed in the fruits silenced in PacNCED1, which encodes a key enzyme in the ABA biosynthesis pathway. The endogenous ABA content as well as the transcript levels of six structural genes and PacMYBA in PacNCED1-RNAi (RNA interference) fruit were significantly lower than in the TRV vector control fruit. These results suggest that PacMYBA plays an important role in ABA-regulated anthocyanin biosynthesis and ABA is a signal molecule that promotes red-colored sweet cherry fruit accumulating anthocyanin.

  14. Multiple impacts of the plant growth-promoting rhizobacterium Variovorax paradoxus 5C-2 on nutrient and ABA relations of Pisum sativum.

    PubMed

    Jiang, Fan; Chen, Lin; Belimov, Andrey A; Shaposhnikov, Alexander I; Gong, Fan; Meng, Xu; Hartung, Wolfram; Jeschke, Dieter W; Davies, William J; Dodd, Ian C

    2012-11-01

    Resolving the physiological mechanisms by which rhizobacteria enhance plant growth is difficult, since many such bacteria contain multiple plant growth-promoting properties. To understand further how the 1-aminocyclopropane-1-carboxylate (ACC) deaminase (ACCd)-containing rhizobacterium Variovorax paradoxus 5C-2 affects plant growth, the flows and partitioning of mineral nutrients and abscisic acid (ABA) and ABA metabolism were studied in pea (Pisum sativum) plants following rhizosphere bacterial inoculation. Although root architecture was not affected, inoculation increased root and shoot biomass, and stomatal conductance, by 20, 15, and 24%, respectively, and increased N, P, K, Ca, and Mg uptake by 16, 81, 50, 46, and 58%, respectively. P deposition in inoculated plant roots was 4.9 times higher than that in uninoculated controls. Rhizobacterial inoculation increased root to shoot xylem flows and shoot to root phloem flows of K by 1.8- and 2.1-fold, respectively. In control plants, major sinks for K deposition were the roots and upper shoot (43% and 49% of total uptake, respectively), while rhizobacterial inoculation increased K distribution to the lower shoot at the expense of other compartments (xylem, phloem, and upper shoot). Despite being unable to metabolize ABA in vitro, V. paradoxus 5C-2 decreased root ABA concentrations and accumulation by 40-60%. Although inoculation decreased xylem ABA flows, phloem ABA flows increased. Whether bacterial ACCd attenuates root to shoot ABA signalling requires further investigation, since ABA is critical to maintain growth of droughted plants, and ACCd-containing organisms have been advocated as a means of minimizing growth inhibition of plants in drying soil.

  15. Shoot-derived abscisic acid promotes root growth.

    PubMed

    McAdam, Scott A M; Brodribb, Timothy J; Ross, John J

    2016-03-01

    The phytohormone abscisic acid (ABA) plays a major role in regulating root growth. Most work to date has investigated the influence of root-sourced ABA on root growth during water stress. Here, we tested whether foliage-derived ABA could be transported to the roots, and whether this foliage-derived ABA had an influence on root growth under well-watered conditions. Using both application studies of deuterium-labelled ABA and reciprocal grafting between wild-type and ABA-biosynthetic mutant plants, we show that both ABA levels in the roots and root growth in representative angiosperms are controlled by ABA synthesized in the leaves rather than sourced from the roots. Foliage-derived ABA was found to promote root growth relative to shoot growth but to inhibit the development of lateral roots. Increased root auxin (IAA) levels in plants with ABA-deficient scions suggest that foliage-derived ABA inhibits root growth through the root growth-inhibitor IAA. These results highlight the physiological and morphological importance, beyond the control of stomata, of foliage-derived ABA. The use of foliar ABA as a signal for root growth has important implications for regulating root to shoot growth under normal conditions and suggests that leaf rather than root hydration is the main signal for regulating plant responses to moisture.

  16. Expression analysis in soybean of IDA-like, HAESA-like and other key regulatory proteins during leaf abscission and cyst nematode infected roots

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The stimulatory and inhibitory role of ethylene and auxin, respectively, in leaf abscission is well documented. More recently, IDA peptides and their putative interacting receptor like kinase partner, HAESA, were shown to be essential components in Arabidopsis floral organ abscission. It was propo...

  17. Transcriptome profiling of petal abscission zone and functional analysis of AUX/IAA family genes reveal that RhIAA16 is involved in petal shedding in rose

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rose is one of the most important cut flowers among ornamental plants. Rose flower longevity is largely dependent on the timing of petal shedding occurrence. To understand the molecular mechanism underlying petal abscission in rose, we performed transcriptome profiling of the petal abscission zone d...

  18. Response of Cultured Maize Cells to (+)-Abscisic Acid, (-)-Abscisic Acid, and Their Metabolites.

    PubMed Central

    Balsevich, J. J.; Cutler, A. J.; Lamb, N.; Friesen, L. J.; Kurz, E. U.; Perras, M. R.; Abrams, S. R.

    1994-01-01

    The metabolism and effects of (+)-S- and (-)-R-abscisic acid (ABA) and some metabolites were studied in maize (Zea mays L. cv Black Mexican Sweet) suspension-cultured cells. Time-course studies of metabolite formation were performed in both cells and medium via analytical high-performance liquid chromatography. Metabolites were isolated and identified using physical and chemical methods. At 10 [mu]M concentration and 28[deg] C, (+)-ABA was metabolized within 24 h, yielding natural (-)-phaseic acid [(-)-PA] as the major product. The unnatural enantiomer (-)-ABA was less than 50% metabolized within 24 h and gave primarily (-)-7[prime]-hydroxyABA [(-)-7[prime]-HOABA], together with (+)-PA and ABA glucose ester. The distribution of metabolites in cells and medium was different, reflecting different sites of metabolism and membrane permeabilities of conjugated and nonconjugated metabolites. The results imply that (+)-ABA was oxidized to (-)-PA inside the cell, whereas (-)-ABA was converted to (-)-7[prime]-HOABA at the cell surface. Growth of maize cells was inhibited by both (+)- and (-)-ABA, with only weak contributions from their metabolites. The concentration of (+)-ABA that caused a 50% inhibition of growth of maize cells was approximately 1 [mu]M, whereas that for its metabolite (-)-PA was approximately 50 [mu]M. (-)-ABA was less active than (+)-ABA, with 50% growth inhibition observed at about 10 [mu]M. (-)-7[prime]-HOABA was only weakly active, with 50% inhibition caused by approximately 500 [mu]M. Time-course studies of medium pH indicated that (+)-ABA caused a transient pH increase (+0.3 units) at 6 h after addition that was not observed in controls or in samples treated with (-)-PA. The effect of (-)-ABA on medium Ph was marginal. No racemization at C-1[prime] of (+)-ABA, (-)-ABA, or metabolites was observed during the studies. PMID:12232311

  19. Abscisic acid-lipid interactions: a phospholipid monolayer study.

    PubMed

    Bürner, H; Benz, R; Gimmler, H; Hartung, W; Stillwell, W

    1993-08-15

    Lipid monolayer studies were performed on a Langmuir trough in the absence and in the presence of the plant hormone abscisic acid (ABA). The ABA-induced effects on the lipid monolayers can be summarized as follows: (i) ABA as the free acid (pH below 5.3) increased the molecular area and slightly decreased the surface pressure in the collapse points of monolayers made of saturated, unsaturated and of mixed lipids; ABA as the anion showed only minor effects. (ii) The ABA-induced area increase of the lipid monolayers decreased when the surface pressure increased, but some ABA remained in the monolayers made of unsaturated phospholipids even at collapse pressure. (iii) The incorporation of ABA into the monolayers could be inhibited by adding the plant sterol beta-sitosterol to the monolayer forming phospholipids. (iv) There was no substantial difference of ABA action on plant phospholipids as compared with other phospholipids. (v) ABA had a much stronger influence on unsaturated phospholipids than on saturated ones. (vi) ABA decreased the phase-transition temperature of saturated phospholipids. These results, which agree with those obtained from phospholipid vesicle studies, indicate that the physical state of the lipid is important for the ability of ABA penetrating into the lipid monolayer. Finally, a possible relevance of these results is discussed in terms of the action of ABA on guard cell membranes of plants.

  20. The Role and Regulation of ABI5 (ABA-Insensitive 5) in Plant Development, Abiotic Stress Responses and Phytohormone Crosstalk

    PubMed Central

    Skubacz, Anna; Daszkowska-Golec, Agata; Szarejko, Iwona

    2016-01-01

    ABA Insensitive 5 (ABI5) is a basic leucine zipper transcription factor that plays a key role in the regulation of seed germination and early seedling growth in the presence of ABA and abiotic stresses. ABI5 functions in the core ABA signaling, which is composed of PYR/PYL/RCAR receptors, PP2C phosphatases and SnRK2 kinases, through the regulation of the expression of genes that contain the ABSCISIC ACID RESPONSE ELEMENT (ABRE) motif within their promoter region. The regulated targets include stress adaptation genes, e.g., LEA proteins. However, the expression and activation of ABI5 is not only dependent on the core ABA signaling. Many transcription factors such as ABI3, ABI4, MYB7 and WRKYs play either a positive or a negative role in the regulation of ABI5 expression. Additionally, the stability and activity of ABI5 are also regulated by other proteins through post-translational modifications such as phosphorylation, ubiquitination, sumoylation and S-nitrosylation. Moreover, ABI5 also acts as an ABA and other phytohormone signaling integrator. Components of auxin, cytokinin, gibberellic acid, jasmonate and brassinosteroid signaling and metabolism pathways were shown to take part in ABI5 regulation and/or to be regulated by ABI5. Monocot orthologs of AtABI5 have been identified. Although their roles in the molecular and physiological adaptations during abiotic stress have been elucidated, knowledge about their detailed action still remains elusive. Here, we describe the recent advances in understanding the action of ABI5 in early developmental processes and the adaptation of plants to unfavorable environmental conditions. We also focus on ABI5 relation to other phytohormones in the abiotic stress response of plants. PMID:28018412

  1. Abscisic acid interacts antagonistically with salicylic acid signaling pathway in rice-Magnaporthe grisea interaction.

    PubMed

    Jiang, Chang-Jie; Shimono, Masaki; Sugano, Shoji; Kojima, Mikiko; Yazawa, Katsumi; Yoshida, Riichiro; Inoue, Haruhiko; Hayashi, Nagao; Sakakibara, Hitoshi; Takatsuji, Hiroshi

    2010-06-01

    Plant hormones play pivotal signaling roles in plant-pathogen interactions. Here, we report characterization of an antagonistic interaction of abscisic acid (ABA) with salicylic acid (SA) signaling pathways in the rice-Magnaporthe grisea interaction. Exogenous application of ABA drastically compromised the rice resistance to both compatible and incompatible M. grisea strains, indicating that ABA negatively regulates both basal and resistance gene-mediated blast resistance. ABA markedly suppressed the transcriptional upregulation of WRKY45 and OsNPR1, the two key components of the SA signaling pathway in rice, induced by SA or benzothiadiazole or by blast infection. Overexpression of OsNPR1 or WRKY45 largely negated the enhancement of blast susceptibility by ABA, suggesting that ABA acts upstream of WRKY45 and OsNPR1 in the rice SA pathway. ABA-responsive genes were induced during blast infection in a pattern reciprocal to those of WRKY45 and OsPR1b in the compatible rice-blast interaction but only marginally in the incompatible one. These results suggest that the balance of SA and ABA signaling is an important determinant for the outcome of the rice-M. grisea interaction. ABA was detected in hyphae and conidia of M. grisea as well as in culture media, implying that blast-fungus-derived ABA could play a role in triggering ABA signaling at host infection sites.

  2. The molecular basis of ABA-independent inhibition of PP2Cs by a subclass of PYL proteins.

    PubMed

    Hao, Qi; Yin, Ping; Li, Wenqi; Wang, Li; Yan, Chuangye; Lin, Zhaohu; Wu, Jim Zhen; Wang, Jiawei; Yan, S Frank; Yan, Nieng

    2011-06-10

    PYR1/PYL/RCAR proteins (PYLs) are confirmed abscisic acid (ABA) receptors, which inhibit protein phosphatase 2C (PP2C) upon binding to ABA. Arabidopsis thaliana has 14 PYLs, yet their functional distinction remains unclear. Here, we report systematic biochemical characterization of PYLs. A subclass of PYLs, represented by PYL10, inhibited PP2C in the absence of any ligand. Crystal structures of PYL10, both in the free form and in the HAB1 (PP2C)-bound state, revealed the structural basis for its constitutive activity. Structural-guided biochemical analyses revealed that ABA-independent inhibition of PP2C requires the PYLs to exist in a monomeric state. In addition, the residues guarding the entrance to the ligand-binding pocket of these PYLs should be bulky and hydrophobic. Based on these principles, we were able to generate monomeric PYL2 variants that gained constitutive inhibitory effect on PP2Cs. These findings provide an important framework for understanding the complex regulation of ABA signaling by PYL proteins.

  3. Anti-transpirant activity in xylem sap from flooded tomato (Lycopersicon esculentum Mill.) plants is not due to pH-mediated redistributions of root- or shoot-sourced ABA.

    PubMed

    Else, Mark A; Taylor, June M; Atkinson, Christopher J

    2006-01-01

    In flooded soils, the rapid effects of decreasing oxygen availability on root metabolic activity are likely to generate many potential chemical signals that may impact on stomatal apertures. Detached leaf transpiration tests showed that filtered xylem sap, collected at realistic flow rates from plants flooded for 2 h and 4 h, contained one or more factors that reduced stomatal apertures. The closure could not be attributed to increased root output of the glucose ester of abscisic acid (ABA-GE), since concentrations and deliveries of ABA conjugates were unaffected by soil flooding. Although xylem sap collected from the shoot base of detopped flooded plants became more alkaline within 2 h of flooding, this rapid pH change of 0.5 units did not alter partitioning of root-sourced ABA sufficiently to prompt a transient increase in xylem ABA delivery. More shoot-sourced ABA was detected in the xylem when excised petiole sections were perfused with pH 7 buffer, compared with pH 6 buffer. Sap collected from the fifth oldest leaf of "intact" well-drained plants and plants flooded for 3 h was more alkaline, by approximately 0.4 pH units, than sap collected from the shoot base. Accordingly, xylem [ABA] was increased 2-fold in sap collected from the fifth oldest petiole compared with the shoot base of flooded plants. However, water loss from transpiring, detached leaves was not reduced when the pH of the feeding solution containing 3-h-flooded [ABA] was increased from 6.7 to 7.1 Thus, the extent of the pH-mediated, shoot-sourced ABA redistribution was not sufficient to raise xylem [ABA] to physiologically active levels. Using a detached epidermis bioassay, significant non-ABA anti-transpirant activity was also detected in xylem sap collected at intervals during the first 24 h of soil flooding.

  4. Abscisic acid in soil facilitates community succession in three forests in China.

    PubMed

    Zhao, Houben; Peng, Shaolin; Chen, Zhuoquan; Wu, Zhongmin; Zhou, Guangyi; Wang, Xu; Qiu, Zhijun

    2011-07-01

    Plants release secondary metabolites into the soil that change the chemical environment around them. Exogenous abscisic acid (ABA) is an important allelochemical whose role in successional trajectories has not been examined. We hypothesized that ABA can accumulate in the soil through successional processes and have an influence on forest dynamics. To this end, we investigated the distribution of ABA in forest communities from early to late successional stages and the response of dominant species to the gradient of ABA concentrations in three types of forests from northern to southern China. Concentrations of ABA in the soils of three forest types increased from early to late successional stages. Pioneer species' litters had the lowest ABA content, and their seed germination and seedling early growth were the most sensitive to the inhibitory effect of ABA. Mid- and late-successional species had a much higher ABA content in fallen leaves than pioneer species, and their seed germination and seedling early growth were inhibited by higher concentrations of ABA than pioneers. Late-successional species showed little response to the highest ABA concentration, possibly due to their large seed size. The results suggest that ABA accumulates in the soil as community succession proceeds. Sensitivity to ABA in the early stages, associated with other characteristics, may result in pioneer species losing their advantage in competition with late-successional species in an increasingly high ABA concentration environment, and being replaced by ABA-tolerant, late-successional species.

  5. Assessment battery for communication (ABaCo): normative data.

    PubMed

    Angeleri, Romina; Bosco, Francesca M; Gabbatore, Ilaria; Bara, Bruno G; Sacco, Katiuscia

    2012-09-01

    The Assessment Battery for Communication (ABaCo) was introduced to evaluate pragmatic abilities in patients with cerebral lesions. The battery is organized into five evaluation scales focusing on separate components of pragmatic competence. In the present study, we present normative data for individuals 15-75 years of age (N = 300). The sample was stratified by age, sex, and years of education, according to Italian National Institute of Statistics indications in order to be representative of the general national population. Since performance on the ABaCo decreases with age and lower years of education, the norms were stratified for both age and education. The ABaCo is a valuable tool in clinical practice; the normative data provided here will enable clinicians to determine different kinds and specific levels of communicative impairments more precisely.

  6. The rose (Rosa hybrida) NAC transcription factor 3 gene, RhNAC3, involved in ABA signaling pathway both in rose and Arabidopsis.

    PubMed

    Jiang, Guimei; Jiang, Xinqiang; Lü, Peitao; Liu, Jitao; Gao, Junping; Zhang, Changqing

    2014-01-01

    Plant transcription factors involved in stress responses are generally classified by their involvement in either the abscisic acid (ABA)-dependent or the ABA-independent regulatory pathways. A stress-associated NAC gene from rose (Rosa hybrida), RhNAC3, was previously found to increase dehydration tolerance in both rose and Arabidopsis. However, the regulatory mechanism involved in RhNAC3 action is still not fully understood. In this study, we isolated and analyzed the upstream regulatory sequence of RhNAC3 and found many stress-related cis-elements to be present in the promoter, with five ABA-responsive element (ABRE) motifs being of particular interest. Characterization of Arabidopsis thaliana plants transformed with the putative RhNAC3 promoter sequence fused to the β-glucuronidase (GUS) reporter gene revealed that RhNAC3 is expressed at high basal levels in leaf guard cells and in vascular tissues. Moreover, the ABRE motifs in the RhNAC3 promoter were observed to have a cumulative effect on the transcriptional activity of this gene both in the presence and absence of exogenous ABA. Overexpression of RhNAC3 in A. thaliana resulted in ABA hypersensitivity during seed germination and promoted leaf closure after ABA or drought treatments. Additionally, the expression of 11 ABA-responsive genes was induced to a greater degree by dehydration in the transgenic plants overexpressing RhNAC3 than control lines transformed with the vector alone. Further analysis revealed that all these genes contain NAC binding cis-elements in their promoter regions, and RhNAC3 was found to partially bind to these putative NAC recognition sites. We further found that of 219 A. thaliana genes previously shown by microarray analysis to be regulated by heterologous overexpression RhNAC3, 85 are responsive to ABA. In rose, the expression of genes downstream of the ABA-signaling pathways was also repressed in RhNAC3-silenced petals. Taken together, we propose that the rose RhNAC3 protein

  7. The Top 10 Reasons Children With Autism Deserve ABA

    PubMed Central

    Walsh, Mary Beth

    2011-01-01

    We who advocate for applied behavior analysis (ABA) for children with autism spectrum disorders often construct our arguments based on the scientific evidence. However, the audience that most needs to hear this argument, that is, the parents of children, especially very young children, diagnosed with autism, may not be convinced by the science alone. This essay attempts to make the case for the multiple benefits of ABA intervention through the use of humor and anecdotes couched in a “Top Ten List,” and illustrating most points with stories of an engaging child with autism (my son, Ben). PMID:22532906

  8. Spatio-temporal changes in endogenous abscisic acid contents during etiolated growth and photomorphogenesis in tomato seedlings

    PubMed Central

    Humplík, Jan F; Turečková, Veronika; Fellner, Martin; Bergougnoux, Véronique

    2015-01-01

    The role of abscisic acid (ABA) during early development was investigated in tomato seedlings. The endogenous content of ABA in particular organs was analyzed in seedlings grown in the dark and under blue light. Our results showed that in dark-grown seedlings, the ABA accumulation was maximal in the cotyledons and elongation zone of hypocotyl, whereas under blue-light, the ABA content was distinctly reduced. Our data are consistent with the conclusion that ABA promotes the growth of etiolated seedlings and the results suggest that ABA plays an inhibitory role in de-etiolation and photomorphogenesis in tomato. PMID:26322576

  9. WRKY41 controls Arabidopsis seed dormancy via direct regulation of ABI3 transcript levels not downstream of ABA.

    PubMed

    Ding, Zhong Jie; Yan, Jing Ying; Li, Gui Xin; Wu, Zhong Chang; Zhang, Shu Qun; Zheng, Shao Jian

    2014-09-01

    Although seed dormancy is an important agronomic trait, its molecular basis is poorly understood. ABSCISIC ACID INSENSITIVE 3 (ABI3) plays an essential role in the establishment of seed dormancy. Here, we show that the lack of a seed-expressed WRKY transcription factor, WRKY41, confers reduced primary seed dormancy and thermoinhibition, phenotypes resembling those for a lack of ABI3. Loss-of-function abi3-17 and wrky41 alleles also both confer reduced sensitivity to ABA during germination and early seedling growth. Absence of WRKY41 decreases ABI3 transcript abundance in maturing and imbibed seeds, whereas transgenically overexpressing WRKY41 increases ABI3 expression. Moreover, transgenic overexpression of ABI3 completely restores seed dormancy phenotypes on wrky41. ChIP-qPCR and EMSA reveal that WRKY41 binds directly to the ABI3 promoter through three adjacent W-boxes, and a transactivation assay indicates that these W-boxes are essential for ABI3 expression. Whilst RT-qPCR analysis shows that the regulation of ABI3 by WRKY41 is not through ABA and other factors known to promote ABI3 transcription during seed maturation and germination, we also show that high concentrations of ABA might promote negative feedback regulation of WRKY41 expression. Finally, analysis of the wrky41 aba2 double mutant confirms that WRKY41 and ABA collaboratively regulate ABI3 expression and seed dormancy. In summary, our results demonstrate that WRKY41 is an important regulator of ABI3 expression, and hence of seed dormancy.

  10. Signalling of abscisic acid to regulate plant growth.

    PubMed Central

    Himmelbach, A; Iten, M; Grill, E

    1998-01-01

    Abscisic acid (ABA) mediated growth control is a fundamental response of plants to adverse environmental cues. The linkage between ABA perception and growth control is currently being unravelled by using different experimental approaches such as mutant analysis and microinjection experiments. So far, two protein phosphatases, ABI1 and ABI2, cADPR, pH, and Ca2+ have been identified as main components of the ABA signalling pathway. Here, the ABA signal transduction pathway is compared to signalling cascades from yeast and mammalian cells. A model for a bifurcated ABA signal transduction pathway exerting a positive and negative control mechanism is proposed. PMID:9800207

  11. Abscisic acid is not necessary for gravitropism in primary roots of Zea mays

    NASA Technical Reports Server (NTRS)

    Moore, R.

    1990-01-01

    Primary roots of Zea mays L. cv. Tx 5855 treated with fluridone are strongly graviresponsive, but have undetectable levels of abscisic acid (ABA). Primary roots of the carotenoid-deficient w-3, vp-5, and vp-7 mutants of Z. mays are also graviresponsive despite having undetectable amounts of ABA. Graviresponsive roots of untreated and wild-type seedlings contain 286 to 317 ng ABA g-1 f. wt, respectively. These results indicate that ABA is not necessary for root gravicurvature.

  12. Profilin 1 is required for abscission during late cytokinesis of chondrocytes

    PubMed Central

    Böttcher, Ralph T; Wiesner, Sebastian; Braun, Attila; Wimmer, Reiner; Berna, Alejandro; Elad, Nadav; Medalia, Ohad; Pfeifer, Alexander; Aszódi, Attila; Costell, Mercedes; Fässler, Reinhard

    2009-01-01

    Profilins are key factors for dynamic rearrangements of the actin cytoskeleton. However, the functions of profilins in differentiated mammalian cells are uncertain because profilin deficiency is early embryonic lethal for higher eukaryotes. To examine profilin function in chondrocytes, we disrupted the profilin 1 gene in cartilage (Col2pfn1). Homozygous Col2pfn1 mice develop progressive chondrodysplasia caused by disorganization of the growth plate and defective chondrocyte cytokinesis, indicated by the appearance of binucleated cells. Surprisingly, Col2pfn1 chondrocytes assemble and contract actomyosin rings normally during cell division; however, they display defects during late cytokinesis as they frequently fail to complete abscission due to their inability to develop strong traction forces. This reduced force generation results from an impaired formation of lamellipodia, focal adhesions and stress fibres, which in part could be linked to an impaired mDia1-mediated actin filament elongation. Neither an actin nor a poly-proline binding-deficient profilin 1 is able to rescue the defects. Taken together, our results demonstrate that profilin 1 is not required for actomyosin ring formation in dividing chondrocytes but necessary to generate sufficient force for abscission during late cytokinesis. PMID:19262563

  13. Arabidopsis ABA-Activated Kinase MAPKKK18 is Regulated by Protein Phosphatase 2C ABI1 and the Ubiquitin-Proteasome Pathway.

    PubMed

    Mitula, Filip; Tajdel, Malgorzata; Cieśla, Agata; Kasprowicz-Maluśki, Anna; Kulik, Anna; Babula-Skowrońska, Danuta; Michalak, Michal; Dobrowolska, Grazyna; Sadowski, Jan; Ludwików, Agnieszka

    2015-12-01

    Phosphorylation and dephosphorylation events play an important role in the transmission of the ABA signal. Although SnRK2 [sucrose non-fermenting1-related kinase2] protein kinases and group A protein phosphatase type 2C (PP2C)-type phosphatases constitute the core ABA pathway, mitogen-activated protein kinase (MAPK) pathways are also involved in plant response to ABA. However, little is known about the interplay between MAPKs and PP2Cs or SnRK2 in the regulation of ABA pathways. In this study, an effort was made to elucidate the role of MAP kinase kinase kinase18 (MKKK18) in relation to ABA signaling and response. The MKKK18 knockout lines showed more vigorous root growth, decreased abaxial stomatal index and increased stomatal aperture under normal growth conditions, compared with the control wild-type Columbia line. In addition to transcriptional regulation of the MKKK18 promoter by ABA, we demonstrated using in vitro and in vivo kinase assays that the kinase activity of MKKK18 was regulated by ABA. Analysis of the cellular localization of MKKK18 showed that the active kinase was targeted specifically to the nucleus. Notably, we identified abscisic acid insensitive 1 (ABI1) PP2C as a MKKK18-interacting protein, and demonstrated that ABI1 inhibited its activity. Using a cell-free degradation assay, we also established that MKKK18 was unstable and was degraded by the proteasome pathway. The rate of MKKK18 degradation was delayed in the ABI1 knockout line. Overall, we provide evidence that ABI1 regulates the activity and promotes proteasomal degradation of MKKK18.

  14. Arabidopsis ABA-Activated Kinase MAPKKK18 is Regulated by Protein Phosphatase 2C ABI1 and the Ubiquitin–Proteasome Pathway

    PubMed Central

    Mitula, Filip; Tajdel, Malgorzata; Cieśla, Agata; Kasprowicz-Maluśki, Anna; Kulik, Anna; Babula-Skowrońska, Danuta; Michalak, Michal; Dobrowolska, Grazyna; Sadowski, Jan; Ludwików, Agnieszka

    2015-01-01

    Phosphorylation and dephosphorylation events play an important role in the transmission of the ABA signal. Although SnRK2 [sucrose non-fermenting1-related kinase2] protein kinases and group A protein phosphatase type 2C (PP2C)-type phosphatases constitute the core ABA pathway, mitogen-activated protein kinase (MAPK) pathways are also involved in plant response to ABA. However, little is known about the interplay between MAPKs and PP2Cs or SnRK2 in the regulation of ABA pathways. In this study, an effort was made to elucidate the role of MAP kinase kinase kinase18 (MKKK18) in relation to ABA signaling and response. The MKKK18 knockout lines showed more vigorous root growth, decreased abaxial stomatal index and increased stomatal aperture under normal growth conditions, compared with the control wild-type Columbia line. In addition to transcriptional regulation of the MKKK18 promoter by ABA, we demonstrated using in vitro and in vivo kinase assays that the kinase activity of MKKK18 was regulated by ABA. Analysis of the cellular localization of MKKK18 showed that the active kinase was targeted specifically to the nucleus. Notably, we identified abscisic acid insensitive 1 (ABI1) PP2C as a MKKK18-interacting protein, and demonstrated that ABI1 inhibited its activity. Using a cell-free degradation assay, we also established that MKKK18 was unstable and was degraded by the proteasome pathway. The rate of MKKK18 degradation was delayed in the ABI1 knockout line. Overall, we provide evidence that ABI1 regulates the activity and promotes proteasomal degradation of MKKK18. PMID:26443375

  15. The Transcription Factor AtDOF4.7 Is Involved in Ethylene- and IDA-Mediated Organ Abscission in Arabidopsis.

    PubMed

    Wang, Gao-Qi; Wei, Peng-Cheng; Tan, Feng; Yu, Man; Zhang, Xiao-Yan; Chen, Qi-Jun; Wang, Xue-Chen

    2016-01-01

    Organ abscission is an important plant developmental process that occurs in response to environmental stress or pathogens. In Arabidopsis, ligand signals, such as ethylene or INFLORESCENCE DEFICIENT IN ABSCISSION (IDA), can regulate organ abscission. Previously, we reported that overexpression of AtDOF4.7, a transcription factor gene, directly suppresses the expression of the abscission-related gene ARABIDOPSIS DEHISCENCE ZONE POLYGALACTURONASE 2 (ADPG2), resulting in a deficiency of floral organ abscission. However, the relationship between AtDOF4.7 and abscission pathways still needs to be investigated. In this study, we showed that ethylene regulates the expression of AtDOF4.7, and the peptide ligand, IDA negatively regulates AtDOF4.7 at the transcriptional level. Genetic evidence indicates that AtDOF4.7 and IDA are involved in a common pathway, and a MAPK cascade can phosphorylate AtDOF4.7 in vitro. Further in vivo data suggest that AtDOF4.7 protein levels may be regulated by this phosphorylation. Collectively, our results indicate that ethylene regulates AtDOF4.7 that is involved in the IDA-mediated floral organ abscission pathway.

  16. The Transcription Factor AtDOF4.7 Is Involved in Ethylene- and IDA-Mediated Organ Abscission in Arabidopsis

    PubMed Central

    Wang, Gao-Qi; Wei, Peng-Cheng; Tan, Feng; Yu, Man; Zhang, Xiao-Yan; Chen, Qi-Jun; Wang, Xue-Chen

    2016-01-01

    Organ abscission is an important plant developmental process that occurs in response to environmental stress or pathogens. In Arabidopsis, ligand signals, such as ethylene or INFLORESCENCE DEFICIENT IN ABSCISSION (IDA), can regulate organ abscission. Previously, we reported that overexpression of AtDOF4.7, a transcription factor gene, directly suppresses the expression of the abscission-related gene ARABIDOPSIS DEHISCENCE ZONE POLYGALACTURONASE 2 (ADPG2), resulting in a deficiency of floral organ abscission. However, the relationship between AtDOF4.7 and abscission pathways still needs to be investigated. In this study, we showed that ethylene regulates the expression of AtDOF4.7, and the peptide ligand, IDA negatively regulates AtDOF4.7 at the transcriptional level. Genetic evidence indicates that AtDOF4.7 and IDA are involved in a common pathway, and a MAPK cascade can phosphorylate AtDOF4.7 in vitro. Further in vivo data suggest that AtDOF4.7 protein levels may be regulated by this phosphorylation. Collectively, our results indicate that ethylene regulates AtDOF4.7 that is involved in the IDA-mediated floral organ abscission pathway. PMID:27379143

  17. A vacuolar β-glucosidase homolog that possesses glucose-conjugated abscisic acid hydrolyzing activity plays an important role in osmotic stress responses in Arabidopsis.

    PubMed

    Xu, Zheng-Yi; Lee, Kwang Hee; Dong, Ting; Jeong, Jae Cheol; Jin, Jing Bo; Kanno, Yuri; Kim, Dae Heon; Kim, Soo Youn; Seo, Mitsunori; Bressan, Ray A; Yun, Dae-Jin; Hwang, Inhwan

    2012-05-01

    The phytohormone abscisic acid (ABA) plays a critical role in various physiological processes, including adaptation to abiotic stresses. In Arabidopsis thaliana, ABA levels are increased both through de novo biosynthesis and via β-glucosidase homolog1 (BG1)-mediated hydrolysis of Glc-conjugated ABA (ABA-GE). However, it is not known how many different β-glucosidase proteins produce ABA from ABA-GE and how the multiple ABA production pathways are coordinated to increase ABA levels. Here, we report that a previously undiscovered β-glucosidase homolog, BG2, produced ABA by hydrolyzing ABA-GE and plays a role in osmotic stress response. BG2 localized to the vacuole as a high molecular weight complex and accumulated to high levels under dehydration stress. BG2 hydrolyzed ABA-GE to ABA in vitro. In addition, BG2 increased ABA levels in protoplasts upon application of exogenous ABA-GE. Overexpression of BG2 rescued the bg1 mutant phenotype, as observed for the overexpression of NCED3 in bg1 mutants. Multiple Arabidopsis bg2 alleles with a T-DNA insertion in BG2 were more sensitive to dehydration and NaCl stress, whereas BG2 overexpression resulted in enhanced resistance to dehydration and NaCl stress. Based on these observations, we propose that, in addition to the de novo biosynthesis, ABA is produced in multiple organelles by organelle-specific β-glucosidases in response to abiotic stresses.

  18. HLB-associated pre-harvest fruit abscission is mediated by jasmonate/ethylene signaling triggered by secondary fungal infection

    Technology Transfer Automated Retrieval System (TEKTRAN)

    One symptom of citrus huanglongbing (HLB) is excessive pre-harvest fruit drop. Recently, higher incidence of Lasiodiplodia theobromae (Diplodia) was found in HLB-symptomatic orange calyx abscission zones (AZ-C) than in non-symptomatic fruit, and the infection was positively correlated with the reduc...

  19. High-resolution transcript profiling reveals shoot abscission process of spruce dwarf mistletoe Arceuthobium sichuanense in response to ethephon

    PubMed Central

    Wang, Yonglin; Xiong, Dianguang; Jiang, Ning; Li, Xuewu; Yang, Qiqing; Tian, Chengming

    2016-01-01

    Arceuthobium (dwarf mistletoes) are hemiparasites that may cause great damage to infected trees belonging to Pinaceae and Cupressaceae. Currently, dwarf mistletoe control involves the use of the ethylene-producing product ethephon (ETH), which acts by inducing dwarf mistletoe shoot abscission. However, the process by which ETH functions is mostly unknown. Therefore, the transcriptome of the ETH-exposed plants was compared to non-exposed controls to identify genes associated with the response to ethephon. In this study, the reference transcriptome was contained 120,316 annotated unigenes, with a total of 21,764 ETH-responsive differentially expressed unigenes were identified. These ETH-associated genes clustered into 20 distinctly expressed pattern groups, providing a view of molecular events with good spatial and temporal resolution. As expected, the greatest number of unigenes with changed expression were observed at the onset of abscission, suggesting induction by ethylene. ETH also affected genes associated with shoot abscission processes including hormone biosynthesis and signaling, cell wall hydrolysis and modification, lipid transference, and more. The comprehensive transcriptome data set provides a wealth of genomic resources for dwarf mistletoe communities and contributes to a better understanding of the molecular regulatory mechanism of ethylene-caused shoots abscission. PMID:27941945

  20. Clks 1, 2 and 4 prevent chromatin breakage by regulating the Aurora B-dependent abscission checkpoint

    PubMed Central

    Petsalaki, Eleni; Zachos, George

    2016-01-01

    When chromatin is trapped at the intercellular bridge, cells delay completion of cytokinesis (abscission) to prevent chromosome breakage. Here we show that inhibition of Cdc-like kinases (Clks) 1, 2 or 4 accelerates midbody resolution in normally segregating cells and correlates with premature abscission, chromatin breakage and generation of DNA damage in cytokinesis with trapped chromatin. Clk1, Clk2 and Clk4 localize to the midbody in an interdependent manner, associate with Aurora B kinase and are required for Aurora B–serine 331 (S331) phosphorylation and complete Aurora B activation in late cytokinesis. Phosphorylated Aurora B–S331 localizes to the midbody centre and is required for phosphorylation and optimal localization of the abscission protein Chmp4c. In addition, expression of phosphomimetic mutants Aurora B–S331E or Chmp4c-S210D delays midbody disassembly and prevents chromatin breakage in Clk-deficient cells. We propose that Clks 1, 2 and 4 impose the abscission checkpoint by phosphorylating Aurora B–S331 at the midbody. PMID:27126587

  1. Flavor of oranges as impacted by abscission zone formation for trees affected by huanglongbing disease and Lasiodiploida infection

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Trees affected by Huanglongbing (HLB) exhibit excessive fruit drop, which is exacerbated by secondary infection of the abscission zone by the fungus Lasiodiplodia. ‘Hamlin’ orange trees, both healthy and affected by HLB, Candidatus Liberibacter asiaticus (CLas, determined by Polymerase chain reactio...

  2. Overexpression of a novel MADS-box gene SlFYFL delays senescence, fruit ripening and abscission in tomato

    NASA Astrophysics Data System (ADS)

    Xie, Qiaoli; Hu, Zongli; Zhu, Zhiguo; Dong, Tingting; Zhao, Zhiping; Cui, Baolu; Chen, Guoping

    2014-03-01

    MADS-domain proteins are important transcription factors involved in many biological processes of plants. In our study, a tomato MADS-box gene, SlFYFL, was isolated. SlFYFL is expressed in all tissues of tomato and significantly higher in mature leave, fruit of different stages, AZ (abscission zone) and sepal. Delayed leaf senescence and fruit ripening, increased storability and longer sepals were observed in 35S:FYFL tomato. The accumulation of carotenoid was reduced, and ethylene content, ethylene biosynthetic and responsive genes were down-regulated in 35S:FYFL fruits. Abscission zone (AZ) did not form normally and abscission zone development related genes were declined in AZs of 35S:FYFL plants. Yeast two-hybrid assay revealed that SlFYFL protein could interact with SlMADS-RIN, SlMADS1 and SlJOINTLESS, respectively. These results suggest that overexpression of SlFYFL regulate fruit ripening and development of AZ via interactions with the ripening and abscission zone-related MADS box proteins.

  3. Clks 1, 2 and 4 prevent chromatin breakage by regulating the Aurora B-dependent abscission checkpoint.

    PubMed

    Petsalaki, Eleni; Zachos, George

    2016-04-29

    When chromatin is trapped at the intercellular bridge, cells delay completion of cytokinesis (abscission) to prevent chromosome breakage. Here we show that inhibition of Cdc-like kinases (Clks) 1, 2 or 4 accelerates midbody resolution in normally segregating cells and correlates with premature abscission, chromatin breakage and generation of DNA damage in cytokinesis with trapped chromatin. Clk1, Clk2 and Clk4 localize to the midbody in an interdependent manner, associate with Aurora B kinase and are required for Aurora B-serine 331 (S331) phosphorylation and complete Aurora B activation in late cytokinesis. Phosphorylated Aurora B-S331 localizes to the midbody centre and is required for phosphorylation and optimal localization of the abscission protein Chmp4c. In addition, expression of phosphomimetic mutants Aurora B-S331E or Chmp4c-S210D delays midbody disassembly and prevents chromatin breakage in Clk-deficient cells. We propose that Clks 1, 2 and 4 impose the abscission checkpoint by phosphorylating Aurora B-S331 at the midbody.

  4. Fungal endophyte Penicillium janthinellum LK5 improves growth of ABA-deficient tomato under salinity.

    PubMed

    Khan, Abdul Latif; Waqas, Muhammad; Khan, Abdur Rahim; Hussain, Javid; Kang, Sang-Mo; Gilani, Syed Abdullah; Hamayun, Muhammad; Shin, Jae-Ho; Kamran, Muhammad; Al-Harrasi, Ahmed; Yun, Byung-Wook; Adnan, Muhammad; Lee, In-Jung

    2013-11-01

    An endophytic fungus was isolated from the roots of tomato (Solanum lycopersicum Mill) and identified as Penicillium janthinellum LK5. The culture filtrate (CF) of P. janthinellum significantly increased the shoot length of gibberellins (GAs) deficient mutant waito-c and normal Dongjin-beyo rice seedlings as compared to control. The CF of P. janthinellum contained GAs (GA3, GA4, GA7 and GA12). To assess endophyte-growth promoting and stress-tolerance potential, the CF along with the propagules of endophyte was applied to tomato-host and abscisic acid (ABA)-deficient mutant Sitiens plants under sodium chloride (NaCl) induced salinity stress. Sitiens plants had retarded growth under normal and salinity stress however its growth was much improved during P. janthinellum-association. The endophyte inoculation reduced the membrane injury by decreasing lipid peroxidation as compared to non-inoculated control under salinity. Endophyte-associated Sitiens plants have significantly higher catalase, peroxidase and glutathione activities as compared to control. Endophyte-infected host and Sitiens plants had low level of sodium ion toxicity and high calcium contents in its root as compared to control. P. janthinellum LK5 helped the Sitiens plants to synthesis significantly higher ABA and reduced the level of jasmonic acid to modulate stress responses. The results suggest that endophytes-association can resist salinity stress by producing gibberellins and activating defensive mechanisms of host and Sitiens plants to achieve improved growth.

  5. Investigating the role of ABA signaling in wheat drought tolerance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Allohexaploid wheat (Triticum aestivum L.) is one of the three major cereal crops supporting human nutrition. Because wheat is often grown under dryland conditions, it is subject to losses as a result of drought stress. This study examines the role of the plant hormone ABA is wheat responses to wate...

  6. ABA and Diverse Cultural and Linguistic Environments: A Welsh Perspective

    ERIC Educational Resources Information Center

    Jones, E. W.; Hoerger, M.; Hughes, J. C.; Williams, B. M.; Jones, B.; Moseley, Y.; Hughes, D. R.; Prys, D.

    2011-01-01

    Gwynedd Local Education Authority (LEA) in North West Wales, UK, is funding a small-scale autism-specific specialist education service using ABA methodology. The program is available through the medium of Welsh, English or bilingually, depending on the individual needs of the child (Jones and Hoerger in Eur J Behav Anal 10:249-253,…

  7. ABA, AAB and ABC Renewal in Taste Aversion Learning

    ERIC Educational Resources Information Center

    Bernal-Gamboa, Rodolfo; Juarez, Yectivani; Gonzalez-Martin, Gabriela; Carranza, Rodrigo; Sanchez-Carrasco, Livia; Nieto, Javier

    2012-01-01

    Context renewal is identified when the conditioned response (CR) elicited by an extinguished conditioned stimulus (CS) reappears as a result of changing the contextual cues during the test. Two experiments were designed for testing contextual renewal in a conditioned taste aversion preparation. Experiment 1 assessed ABA and AAB context renewal,…

  8. Adaptive Behaviour Assessment System: Indigenous Australian Adaptation Model (ABAS: IAAM)

    ERIC Educational Resources Information Center

    du Plessis, Santie

    2015-01-01

    The study objectives were to develop, trial and evaluate a cross-cultural adaptation of the Adaptive Behavior Assessment System-Second Edition Teacher Form (ABAS-II TF) ages 5-21 for use with Indigenous Australian students ages 5-14. This study introduced a multiphase mixed-method design with semi-structured and informal interviews, school…

  9. Personality Traits Associated with Occupational "Burnout" in ABA Therapists

    ERIC Educational Resources Information Center

    Hurt, Amy A.; Grist, Cathy Lann; Malesky, Lann A., Jr.; McCord, David M.

    2013-01-01

    Background: Applied behaviour analysis (ABA) therapists typically work one-to-one with children with autism for extended periods of time, which often leads to high levels of job-related stress, lower levels of job satisfaction, increased frequency of occupational "burnout" and higher than average job turnover (Journal of Autism…

  10. Dissociations among ABA, ABC, and AAB Recovery Effects

    ERIC Educational Resources Information Center

    Ungor, Metin; Lachnit, Harald

    2008-01-01

    In a human predictive learning experiment, the strengths of ABA, ABC, and AAB recovery effects after discrimination reversal learning were compared. Initially, a discrimination between two stimuli (X+, Y-) was trained in Context A. During Phase 2, participants received discrimination reversal training (X-, Y+) either in Context A (Group AAB) or in…

  11. ABA and Instruction of Students with Autism Spectrum Disorders: Introduction to the Special Series.

    ERIC Educational Resources Information Center

    Heflin, L. Juane; Alberto, Paul A.

    2001-01-01

    This introductory article to this special issue on the use of applied behavior analysis (ABA) with autism spectrum disorders (ASD) notes the 40-year history of ABA strategy development, verification, and generalization. It briefly introduces the following articles, which are intended to illustrate the range of ABA applications and the depth of…

  12. Coping as a Predictor of Burnout and General Health in Therapists Working in ABA Schools

    ERIC Educational Resources Information Center

    Griffith, G. M.; Barbakou, A.; Hastings, R. P.

    2014-01-01

    Background: Little is known about the work-related well-being of applied behaviour analysis (ABA) therapists who work in school-based contexts and deliver ABA interventions to children with autism. Methods: A questionnaire on work-related stress (burnout), general distress, perceived supervisor support and coping was completed by 45 ABA therapists…

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

    PubMed Central

    Zandalinas, Sara I.; Balfagón, Damián; Arbona, Vicent; Gómez-Cadenas, Aurelio; Inupakutika, Madhuri A.; Mittler, Ron

    2016-01-01

    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. PMID:27497287

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

    PubMed

    Zandalinas, Sara I; Balfagón, Damián; Arbona, Vicent; Gómez-Cadenas, Aurelio; Inupakutika, Madhuri A; Mittler, Ron

    2016-10-01

    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.

  15. Seasonal changes in needle water content and needle ABA concentration of Japanese red pine, Pinus densiflora, in declining forests on Mt. Gokurakuji, Hiroshima prefecture, Japan.

    PubMed

    Kume, Atsushi; Hanba, Yuko T; Nakane, Kaneyuki; Sakurai, Naoki; Sakugawa, Hiroshi

    2006-05-01

    To evaluate the effects of air pollution on the decline of Pinus densiflora forests, various research has been conducted around Mt. Gokurakuji (34 degrees 23'N, 132 degrees 19'E, 693 m a.s.l.) north of the Seto Inland Sea, west Japan. To investigate the mechanisms responsible for decreases in photosynthesis (Pn) and stomatal conductance (gl), delta13C of needles and seasonal changes in the water content (WC) and abscisic acid concentration (ABA) of needles were measured in various stands. The delta13C values were less negative in declining stands and younger needles. ABA and WC were not correlated with each other. WC decreased consistently with needle age while the ABA showed a minimum in August and a smaller content in older needles. Monthly precipitation and the daily maximum vapor pressure were not correlated with ABA and WC. In declining stands, WC and ABA tended to be higher and lower, respectively, than in nondeclining stands. These results suggest that the trees in declining stands received less water stress than those in nondeclining stands and the differences in gl and delta13C are not caused by the difference in water stress. The possibilities of the effects of air pollution and the infection of pine-wood nematode on the physiological decline on the pine needles are discussed.

  16. Unravelling molecular responses to moderate dehydration in harvested fruit of sweet orange (Citrus sinensis L. Osbeck) using a fruit-specific ABA-deficient mutant

    PubMed Central

    Romero, Paco; Rodrigo, María J.; Alférez, Fernando; Ballester, Ana-Rosa; González-Candelas, Luis; Zacarías, Lorenzo; Lafuente, María T.

    2012-01-01

    Water stress affects many agronomic traits that may be regulated by the phytohormone abscisic acid (ABA). Within these traits, loss of fruit quality becomes important in many citrus cultivars that develop peel damage in response to dehydration. To study peel dehydration transcriptional responsiveness in harvested citrus fruit and the putative role of ABA in this process, this study performed a comparative large-scale transcriptional analysis of water-stressed fruits of the wild-type Navelate orange (Citrus sinesis L. Osbeck) and its spontaneous ABA-deficient mutant Pinalate, which is more prone to dehydration and to developing peel damage. Major changes in gene expression occurring in the wild-type line were impaired in the mutant fruit. Gene ontology analysis revealed the ability of Navelate fruits to induce the response to water deprivation and di-, tri-valent inorganic cation transport biological processes, as well as repression of the carbohydrate biosynthesis process in the mutant. Exogenous ABA triggered relevant transcriptional changes and repressed the protein ubiquitination process, although it could not fully rescue the physiological behaviour of the mutant. Overall, the results indicated that dehydration responsiveness requires ABA-dependent and -independent signals, and highlight that the ability of citrus fruits to trigger molecular responses against dehydration is an important factor in reducing their susceptibility to developing peel damage. PMID:22315241

  17. Unravelling molecular responses to moderate dehydration in harvested fruit of sweet orange (Citrus sinensis L. Osbeck) using a fruit-specific ABA-deficient mutant.

    PubMed

    Romero, Paco; Rodrigo, María J; Alférez, Fernando; Ballester, Ana-Rosa; González-Candelas, Luis; Zacarías, Lorenzo; Lafuente, María T

    2012-04-01

    Water stress affects many agronomic traits that may be regulated by the phytohormone abscisic acid (ABA). Within these traits, loss of fruit quality becomes important in many citrus cultivars that develop peel damage in response to dehydration. To study peel dehydration transcriptional responsiveness in harvested citrus fruit and the putative role of ABA in this process, this study performed a comparative large-scale transcriptional analysis of water-stressed fruits of the wild-type Navelate orange (Citrus sinesis L. Osbeck) and its spontaneous ABA-deficient mutant Pinalate, which is more prone to dehydration and to developing peel damage. Major changes in gene expression occurring in the wild-type line were impaired in the mutant fruit. Gene ontology analysis revealed the ability of Navelate fruits to induce the response to water deprivation and di-, tri-valent inorganic cation transport biological processes, as well as repression of the carbohydrate biosynthesis process in the mutant. Exogenous ABA triggered relevant transcriptional changes and repressed the protein ubiquitination process, although it could not fully rescue the physiological behaviour of the mutant. Overall, the results indicated that dehydration responsiveness requires ABA-dependent and -independent signals, and highlight that the ability of citrus fruits to trigger molecular responses against dehydration is an important factor in reducing their susceptibility to developing peel damage.

  18. Arabidopsis Tóxicos en Levadura 78 (AtATL78) mediates ABA-dependent ROS signaling in response to drought stress.

    PubMed

    Suh, Ji Yeon; Kim, Soo Jin; Oh, Tae Rin; Cho, Seok Keun; Yang, Seong Wook; Kim, Woo Taek

    2016-01-01

    Plants have developed a variety of complicated responses to cope with drought, one of the most challenging environmental stresses. As a quick response, plants rapidly inhibit stomatal opening under the control of abscisic acid (ABA) signaling pathway, in order to preserve water. Here, we report that Arabidopsis Tóxicos en Levadura (ATL), a RING-type E3 ubiquitin ligase, mediates the ABA-dependent stomatal closure. In contrast to wild-type plants, the stomatal closure was fully impaired in atatl78 mutant plants even in the presence of exogenous ABA and reactive oxygen species (ROS). Besides, under high concentrations of Ca(2+), a down-stream signaling molecule of ABA signaling pathway, atatl78 mutant plants successfully closed the pores. Furthermore, AtATL78 protein indirectly associated with catalases and the deficiency of AtATL78 led the reduction of catalase activity and H2O2, implying the function of AtATL78 in the modulation of ROS activity. Based on these results, we suggest that AtATL78 possibly plays a role in promoting ROS-mediated ABA signaling pathway during drought stress.

  19. Grain dormancy loss is associated with changes in ABA and GA sensitivity and hormone accumulation in bread wheat, Triticum aestivum (L.)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Knowledge about the hormonal control of seed dormancy and dormancy loss is essential in wheat, because low seed dormancy at maturity is associated with the problem of preharvest sprouting (PHS) when rain occurs before harvest. Low GA (gibberellin) hormone sensitivity and high ABA (abscisic acid) sen...

  20. Related to ABA-Insensitive3(ABI3)/Viviparous1 and AtABI5 transcription factor coexpression in cotton enhances drought stress adaptation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Drought tolerance is an important trait being pursued by the agbiotech industry. Abscisic acid (ABA) is a stress hormone that mediates a multitude of processes in growth and development, water use efficiency and gene expression during seed development and in response to environmental stresses. Arabi...

  1. Type B Heterotrimeric G Protein γ-Subunit Regulates Auxin and ABA Signaling in Tomato.

    PubMed

    Subramaniam, Gayathery; Trusov, Yuri; Lopez-Encina, Carlos; Hayashi, Satomi; Batley, Jacqueline; Botella, José Ramón

    2016-02-01

    Heterotrimeric G proteins composed of α, β, and γ subunits are central signal transducers mediating the cellular response to multiple stimuli in most eukaryotes. Gγ subunits provide proper cellular localization and functional specificity to the heterotrimer complex. Plant Gγ subunits, divided into three structurally distinct types, are more diverse than their animal counterparts. Type B Gγ subunits, lacking a carboxyl-terminal isoprenylation motif, are found only in flowering plants. We present the functional characterization of type B Gγ subunit (SlGGB1) in tomato (Solanum lycopersicum). We show that SlGGB1 is the most abundant Gγ subunit in tomato and strongly interacts with the Gβ subunit. Importantly, the green fluorescent protein-SlGGB1 fusion protein as well as the carboxyl-terminal yellow fluorescent protein-SlGGB1/amino-terminal yellow fluorescent protein-Gβ heterodimer were localized in the plasma membrane, nucleus, and cytoplasm. RNA interference-mediated silencing of SlGGB1 resulted in smaller seeds, higher number of lateral roots, and pointy fruits. The silenced lines were hypersensitive to exogenous auxin, while levels of endogenous auxins were lower or similar to those of the wild type. SlGGB1-silenced plants also showed strong hyposensitivity to abscisic acid (ABA) during seed germination but not in other related assays. Transcriptome analysis of the transgenic seeds revealed abnormal expression of genes involved in ABA sensing, signaling, and response. We conclude that the type B Gγ subunit SlGGB1 mediates auxin and ABA signaling in tomato.

  2. Two abscission zones proximal to Lansium domesticum fruit: one more sensitive to exogenous ethylene than the other

    PubMed Central

    Taesakul, Prapinporn; Siriphanich, Jingtair; van Doorn, Wouter G.

    2015-01-01

    Longkong (Lansium domesticum) fruit grows in bunches and is also sold as bunches. Individual fruit can separate from the bunch both before and after commercial harvest. The fruit has two separation sites. The first is located between bracts on the stem and the fused sepals (separation zone 1: SZ1) and the second between the fused sepals and the fruit (separation zone 2: SZ2). True abscission occurred at both zones. We investigated whether the two zones were active at different stages of development and if they were differentially sensitive to ethylene. Abscission occurred in the SZ1 in very young fruit (fruit still at the ovary stage), during early fruit development (5 weeks after full bloom; WAFB), and in ripe and overripe fruit (15–17 WAFB). Abscission did not spontaneously occur in the SZ2, but by the time the fruit was fully ripe, 15 WAFB, and later, a slight mechanical force was sufficient to break this zone. In fruit bunches severed from the tree at 5, 8, and 13 WAFB, break strength (BS) in SZ1 decreased much more after exogenous ethylene treatment than that in SZ2. Ethylene induced abscission in the SZ1, but not in SZ2. At 5, 8, and 13 WAFB, treatment with 1-methylcyclopropane (1-MCP; an inhibitor of ethylene perception) had a small effect on BS in the SZ1 and no effect in the SZ2. It is concluded that abscission in the SZ1 was much more sensitive to ethylene than that in the SZ2. In intact plants SZ1 reacts to endogenous ethylene, e.g., as a result of stress, while SZ2 apparently allows animals to remove the ripe fruit from the tree with minimal force. PMID:25954290

  3. Abscisic acid uridine diphosphate glucosyltransferases play a crucial role in abscisic acid homeostasis in Arabidopsis.

    PubMed

    Dong, Ting; Xu, Zheng-Yi; Park, Youngmin; Kim, Dae Heon; Lee, Yongjik; Hwang, Inhwan

    2014-05-01

    The phytohormone abscisic acid (ABA) is crucial for plant growth and adaptive responses to various stress conditions. Plants continuously adjust the ABA level to meet physiological needs, but how ABA homeostasis occurs is not fully understood. This study provides evidence that UGT71B6, an ABA uridine diphosphate glucosyltransferase (UGT), and its two closely related homologs, UGT71B7 and UGT71B8, play crucial roles in ABA homeostasis and in adaptation to dehydration, osmotic stress, and high-salinity stresses in Arabidopsis (Arabidopsis thaliana). UGT RNA interference plants that had low levels of these three UGT transcripts displayed hypersensitivity to exogenous ABA and high-salt conditions during germination and exhibited a defect in plant growth. However, the ectopic expression of UGT71B6 in the atbg1 (for β-glucosidase) mutant background aggravated the ABA-deficient phenotype of atbg1 mutant plants. In addition, modulation of the expression of the three UGTs affects the expression of CYP707A1 to CYP707A4, which encode ABA 8'-hydroxylases; four CYP707As were expressed at higher levels in the UGT RNA interference plants but at lower levels in the UGT71B6:GFP-overexpressing plants. Based on these data, this study proposes that UGT71B6 and its two homologs play a critical role in ABA homeostasis by converting active ABA to an inactive form (abscisic acid-glucose ester) depending on intrinsic cellular and environmental conditions in plants.

  4. Abscisic Acid Biosynthesis in Leaves and Roots of Xanthium strumarium.

    PubMed

    Creelman, R A; Gage, D A; Stults, J T; Zeevaart, J A

    1987-11-01

    RESEARCH ON THE BIOSYNTHESIS OF ABSCISIC ACID (ABA) HAS FOCUSED PRIMARILY ON TWO PATHWAYS: (a) the direct pathway from farnesyl pyrophosphate, and (b) the indirect pathway involving a carotenoid precursor. We have investigated which biosynthetic pathway is operating in turgid and stressed Xanthium leaves, and in stressed Xanthium roots using long-term incubations in (18)O(2). It was found that in stressed leaves three atoms of (18)O from (18)O(2) are incorporated into the ABA molecule, and that the amount of (18)O incorporated increases with time. One (18)O atom is incorporated rapidly into the carboxyl group of ABA, whereas the other two atoms are very slowly incorporated into the ring oxygens. The fourth oxygen atom in the carboxyl group of ABA is derived from water. ABA from stressed roots of Xanthium incubated in (18)O(2) shows a labeling pattern similar to that of ABA in stressed leaves, but with incorporation of more (18)O into the tertiary hydroxyl group at C-1' after 6 and 12 hours than found in ABA from stressed leaves. It is proposed that the precursors to stress-induced ABA are xanthophylls, and that a xanthophyll lacking an oxygen function at C-6 (carotenoid numbering scheme) plays a crucial role in ABA biosynthesis in Xanthium roots. In turgid Xanthium leaves, (18)O is incorporated into ABA to a much lesser extent than it is in stressed leaves, whereas exogenously applied (14)C-ABA is completely catabolized within 48 hours. This suggests that ABA in turgid leaves is either (a) made via a biosynthetic pathway which is different from the one in stressed leaves, or (b) has a half-life on the order of days as compared with a half-life of 15.5 hours in water-stressed Xanthium leaves. Phaseic acid showed a labeling pattern similar to that of ABA, but with an additional (18)O incorporated during 8'-hydroxylation of ABA to phaseic acid.

  5. Arabidopsis HY1-Modulated Stomatal Movement: An Integrative Hub Is Functionally Associated with ABI4 in Dehydration-Induced ABA Responsiveness1

    PubMed Central

    Xie, Yanjie; Mao, Yu; Duan, Xingliang; Zhou, Heng; Lai, Diwen; Zhang, Yihua; Shen, Wenbiao

    2016-01-01

    Heme oxygenase (HO; EC 1.14.99.3) has recently been proposed as a novel component in mediating wide ranges of the plant adaptive signaling processes. However, the physiological significance and molecular basis underlying Arabidopsis (Arabidopsis thaliana) HO1 (HY1) functioning in drought tolerance remained unclear. Here, we report that mutation of HY1 promoted, but overexpression of this gene impaired, Arabidopsis drought tolerance. This was attributed to the abscisic acid (ABA)-hypersensitive or -hyposensitive phenotypes, with the regulation of stomatal closure in particular. However, comparative transcriptomic profile analysis showed that the induction of numerous ABA/stress-dependent genes in dehydrated wild-type plants was differentially impaired in the hy1 mutant. In agreement, ABA-induced ABSCISIC ACID-INSENSITIVE4 (ABI4) transcript accumulation was strengthened in the hy1 mutant. Genetic analysis further identified that the hy1-associated ABA hypersensitivity and drought tolerance were arrested in the abi4 background. Moreover, the promotion of ABA-triggered up-regulation of RbohD abundance and reactive oxygen species (ROS) levels in the hy1 mutant was almost fully blocked by the mutation of ABI4, suggesting that the HY1-ABI4 signaling in the wild type involved in stomatal closure was dependent on the RbohD-derived ROS production. However, hy1-promoted stomatal closure was not affected by a nitric oxide scavenger. Correspondingly, ABA-insensitive behaviors in rbohD stomata were not affected by either the mutation of HY1 or its ectopic expression in the rbohD background, both of which responded significantly to exogenous ROS. These data indicate that HY1 functioned negatively and acted upstream of ABI4 in drought signaling, which was casually dependent on the RbohD-derived ROS in the regulation of stomatal closure. PMID:26704641

  6. Conformationally constrained opioid ligands: the Dmt-Aba and Dmt-Aia versus Dmt-Tic scaffold.

    PubMed

    Ballet, Steven; Feytens, Debby; Wachter, Rien De; Vlaeminck, Magali De; Marczak, Ewa D; Salvadori, Severo; Graaf, Chris de; Rognan, Didier; Negri, Lucia; Lattanzi, Roberta; Lazarus, Lawrence H; Tourwé, Dirk; Balboni, Gianfranco

    2009-01-15

    Replacement of the constrained phenylalanine analogue 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (Tic) in the opioid Dmt-Tic-Gly-NH-Bn scaffold by the 4-amino-1,2,4,5-tetrahydro-indolo[2,3-c]azepin-3-one (Aia) and 4-amino-1,2,4,5-tetrahydro-2-benzazepin-3-one (Aba) scaffolds has led to the discovery of novel potent mu-selective agonists (Structures 5 and 12) as well as potent and selective delta-opioid receptor antagonists (Structures 9 and 15). Both stereochemistry and N-terminal N,N-dimethylation proved to be crucial factors for opioid receptor selectivity and functional bioactivity in the investigated small peptidomimetic templates. In addition to the in vitro pharmacological evaluation, automated docking models of Dmt-Tic and Dmt-Aba analogues were constructed in order to rationalize the observed structure-activity data.

  7. PzsS3a, a novel endosperm specific promoter from maize (Zea mays L.) induced by ABA.

    PubMed

    Hu, Yu-Feng; Li, Yang-ping; Zhang, Junjie; Liu, Hanmei; Chen, Zhiyu; Huang, Yubi

    2011-07-01

    The maize zsS3a gene codes for starch synthase. Transcriptional analysis revealed that it is mainly expressed in endosperm and is induced by abscisic acid (ABA). The 5'-flanking region of zsS3a was isolated, and a 1772 bp zsS3a promoter (PzsS3a) was fused to a Luc reporter gene with a maize Adh1 intron. Transient expression assay by bombardment transformation showed that, although the addition of the Adh1 intron enhanced the promoter activity approx. 52-fold, it did not alter the promoter specificity. PzsS3a with the Adh1 intron drove the Luc gene preferentially and it was highly expressed in the endosperm relative to the embryo but not in the leaf or root. Furthermore, the promoter activity in the endosperm was enhanced four fold by 100 mM ABA.

  8. Abscisic acid and pyrabactin improve vitamin C contents in raspberries.

    PubMed

    Miret, Javier A; Munné-Bosch, Sergi

    2016-07-15

    Abscisic acid (ABA) is a plant growth regulator with roles in senescence, fruit ripening and environmental stress responses. ABA and pyrabactin (a non-photosensitive ABA agonist) effects on red raspberry (Rubus idaeus L.) fruit development (including ripening) were studied, with a focus on vitamin and antioxidant composition. Application of ABA and/or pyrabactin just after fruit set did not affect the temporal pattern of fruit development and ripening; neither provitamin A (carotenoids) nor vitamin E contents were modified. In contrast, ABA and pyrabactin altered the vitamin C redox state at early stages of fruit development and more than doubled vitamin C contents at the end of fruit ripening. These were partially explained by changes in ascorbate oxidation and recycling. Therefore, ABA and pyrabactin applications may be used to increase vitamin C content of ripe fruits, increasing fruit quality and value. However, treatments containing pyrabactin-combined with ABA or alone-diminished protein content, thus partially limiting its potential applicability.

  9. Selection and characterization of single stranded DNA aptamers for the hormone abscisic Acid.

    PubMed

    Grozio, Alessia; Gonzalez, Victor M; Millo, Enrico; Sturla, Laura; Vigliarolo, Tiziana; Bagnasco, Luca; Guida, Lucrezia; D'Arrigo, Cristina; De Flora, Antonio; Salis, Annalisa; Martin, Elena M; Bellotti, Marta; Zocchi, Elena

    2013-10-01

    The hormone abscisic acid (ABA) is a small molecule involved in pivotal physiological functions in higher plants. Recently, ABA has been also identified as an endogenous hormone in mammals, regulating different cell functions including inflammatory processes, stem cell expansion, insulin release, and glucose uptake. Aptamers are short, single-stranded (ss) oligonucleotidesable to recognize target molecules with high affinity. The small size of the ABA molecule represented a challenge for aptamer development and the aim of this study was to develop specific anti-ABA DNA aptamers. Biotinylated abscisic acid (bio-ABA) was immobilized on streptavidin-coated magnetic beads. DNA aptamers against bio-ABA were selected with 7 iterative rounds of the systematic evolution of ligands by exponential enrichment method (SELEX), each round comprising incubation of the ABA-binding beads with the ssDNA sequences, DNA elution, electrophoresis, and polymerase chain reaction (PCR) amplification. The PCR product was cloned and sequenced. The binding affinity of several clones was determined using bio-ABA immobilized on streptavidin-coated plates. Aptamer 2 and aptamer 9 showed the highest binding affinity, with dissociation constants values of 0.98 ± 0.14 μM and 0.80 ± 0.07 μM, respectively. Aptamers 2 and 9 were also able to bind free, unmodified ABA and to discriminate between different ABA enantiomers and isomers. Our findings indicate that ssDNA aptamers can selectively bind ABA and could be used for the development of ABA quantitation assays.

  10. Pollination increases ethylene production in Lilium hybrida cv. Brindisi flowers but does not affect the time to tepal senescence or tepal abscission.

    PubMed

    Pacifici, Silvia; Prisa, Domenico; Burchi, Gianluca; van Doorn, Wouter G

    2015-01-15

    In many species, pollination induces a rapid increase in ethylene production, which induces early petal senescence, petal abscission, or flower closure. Cross-pollination in Lilium hybrida cv. Brindisi resulted in a small increase in flower ethylene production. In intact plants and in isolated flowers, pollination had no effect on the time to tepal senescence or tepal abscission. When applied to closed buds of unpollinated flowers, exogenous ethylene slightly hastened the time to tepal senescence and abscission. However, exogenous ethylene had no effect when the flowers had just opened, i.e. at the time of pollination. Experiments with silver thiosulphate, which blocks the ethylene receptor, indicated that endogenous ethylene had a slight effect on the regulation of tepal senescence and tepal abscission, although only at the time the tepals were still inside buds and not in open flowers. Low ethylene-sensitivity after anthesis therefore explains why pollination had no effect on the processes studied.

  11. Somatic cell encystment promotes abscission in germline stem cells following a regulated block in cytokinesis.

    PubMed

    Lenhart, Kari F; DiNardo, Stephen

    2015-07-27

    In many tissues, the stem cell niche must coordinate behavior across multiple stem cell lineages. How this is achieved is largely unknown. We have identified delayed completion of cytokinesis in germline stem cells (GSCs) as a mechanism that regulates the production of stem cell daughters in the Drosophila testis. Through live imaging, we show that a secondary F-actin ring is formed through regulation of Cofilin activity to block cytokinesis progress after contractile ring disassembly. The duration of this block is controlled by Aurora B kinase. Additionally, we have identified a requirement for somatic cell encystment of the germline in promoting GSC abscission. We suggest that this non-autonomous role promotes coordination between stem cell lineages. These findings reveal the mechanisms by which cytokinesis is inhibited and reinitiated in GSCs and why such complex regulation exists within the stem cell niche.

  12. Examination of the Abscission-Associated Transcriptomes for Soybean, Tomato, and Arabidopsis Highlights the Conserved Biosynthesis of an Extensible Extracellular Matrix and Boundary Layer

    PubMed Central

    Kim, Joonyup; Sundaresan, Srivignesh; Philosoph-Hadas, Sonia; Yang, Ronghui; Meir, Shimon; Tucker, Mark L.

    2015-01-01

    Abscission zone (AZ) development and the progression of abscission (detachment of plant organs) have been roughly separated into four stages: first, AZ differentiation; second, competence to respond to abscission signals; third, activation of abscission; and fourth, formation of a protective layer and post-abscission trans-differentiation. Stage three, activation of abscission, is when changes in the cell wall and extracellular matrix occur to support successful organ separation. Most abscission research has focused on gene expression for enzymes that disassemble the cell wall within the AZ and changes in phytohormones and other signaling events that regulate their expression. Here, transcriptome data for soybean, tomato and Arabidopsis were examined and compared with a focus not only on genes associated with disassembly of the cell wall but also on gene expression linked to the biosynthesis of a new extracellular matrix. AZ-specific up-regulation of genes associated with cell wall disassembly including cellulases (beta-1,4-endoglucanases, CELs), polygalacturonases (PGs), and expansins (EXPs) were much as expected; however, curiously, changes in expression of xyloglucan endotransglucosylase/hydrolases (XTHs) were not AZ-specific in soybean. Unexpectedly, we identified an early increase in the expression of genes underlying the synthesis of a waxy-like cuticle. Based on the expression data, we propose that the early up-regulation of an abundance of small pathogenesis-related (PR) genes is more closely linked to structural changes in the extracellular matrix of separating cells than an enzymatic role in pathogen resistance. Furthermore, these observations led us to propose that, in addition to cell wall loosening enzymes, abscission requires (or is enhanced by) biosynthesis and secretion of small proteins (15–25 kDa) and waxes that form an extensible extracellular matrix and boundary layer on the surface of separating cells. The synthesis of the boundary layer

  13. Bimodal effect of hydrogen peroxide and oxidative events in nitrite-induced rapid root abscission by the water fern Azolla pinnata

    DOE PAGES

    Cohen, Michael F.; Gurung, Sushma; Birarda, Giovanni; ...

    2015-07-09

    In the genus Azolla rapid abscission of roots from floating fronds occurs within minutes in response to a variety of stresses, including exposure to nitrite. We found that hydrogen peroxide, though itself not an inducer of root abscission, modulates nitrite-induced root abscission by Azolla pinnata in a dose-dependent manner, with 2 mM H2O2 significantly diminishing the responsiveness to 2 mM NaNO2, and 10 mM H2O2 slightly enhancing it. Hypoxia, which has been found in other plants to result in autogenic production of H2O2, dramatically stimulated root abscission of A. pinnata in response to nitrite, especially for plants previously cultivated inmore » medium containing 5 mM KNO3 compared to plants cultivated under N2-fixing conditions without combined nitrogen. Plants, including Azolla, produce the small signaling molecule nitric oxide (NO) from nitrite using nitrate reductase. We found Azolla plants to display dose-dependent root abscission in response to the NO donor spermine NONOate. Treatment of plants with the thiol-modifying agents S-methyl methanethiosulfonate or glutathione inhibited the nitrite-induced root abscission response. Synchrotron radiation-based Fourier transform infrared spectromicroscopy revealed higher levels of carbonylation in the abscission zone of dropped roots, indicative of reaction products of polysaccharides with potent free radical oxidants. Lastly, we hypothesize that metabolic products of nitrite and NO react with H2O2 in the apoplast leading to free-radical-mediated cleavage of structural polysaccharides and consequent rapid root abscission.« less

  14. Bimodal effect of hydrogen peroxide and oxidative events in nitrite-induced rapid root abscission by the water fern Azolla pinnata

    SciTech Connect

    Cohen, Michael F.; Gurung, Sushma; Birarda, Giovanni; Holman, Hoi-Ying N.; Yamasaki, Hideo

    2015-07-09

    In the genus Azolla rapid abscission of roots from floating fronds occurs within minutes in response to a variety of stresses, including exposure to nitrite. We found that hydrogen peroxide, though itself not an inducer of root abscission, modulates nitrite-induced root abscission by Azolla pinnata in a dose-dependent manner, with 2 mM H2O2 significantly diminishing the responsiveness to 2 mM NaNO2, and 10 mM H2O2 slightly enhancing it. Hypoxia, which has been found in other plants to result in autogenic production of H2O2, dramatically stimulated root abscission of A. pinnata in response to nitrite, especially for plants previously cultivated in medium containing 5 mM KNO3 compared to plants cultivated under N2-fixing conditions without combined nitrogen. Plants, including Azolla, produce the small signaling molecule nitric oxide (NO) from nitrite using nitrate reductase. We found Azolla plants to display dose-dependent root abscission in response to the NO donor spermine NONOate. Treatment of plants with the thiol-modifying agents S-methyl methanethiosulfonate or glutathione inhibited the nitrite-induced root abscission response. Synchrotron radiation-based Fourier transform infrared spectromicroscopy revealed higher levels of carbonylation in the abscission zone of dropped roots, indicative of reaction products of polysaccharides with potent free radical oxidants. Lastly, we hypothesize that metabolic products of nitrite and NO react with H2O2 in the apoplast leading to free-radical-mediated cleavage of structural polysaccharides and consequent rapid root abscission.

  15. Bimodal effect of hydrogen peroxide and oxidative events in nitrite-induced rapid root abscission by the water fern Azolla pinnata

    PubMed Central

    Cohen, Michael F.; Gurung, Sushma; Birarda, Giovanni; Holman, Hoi-Ying N.; Yamasaki, Hideo

    2015-01-01

    In the genus Azolla rapid abscission of roots from floating fronds occurs within minutes in response to a variety of stresses, including exposure to nitrite. We found that hydrogen peroxide, though itself not an inducer of root abscission, modulates nitrite-induced root abscission by Azolla pinnata in a dose-dependent manner, with 2 mM H2O2 significantly diminishing the responsiveness to 2 mM NaNO2, and 10 mM H2O2 slightly enhancing it. Hypoxia, which has been found in other plants to result in autogenic production of H2O2, dramatically stimulated root abscission of A. pinnata in response to nitrite, especially for plants previously cultivated in medium containing 5 mM KNO3 compared to plants cultivated under N2-fixing conditions without combined nitrogen. Plants, including Azolla, produce the small signaling molecule nitric oxide (NO) from nitrite using nitrate reductase. We found Azolla plants to display dose-dependent root abscission in response to the NO donor spermine NONOate. Treatment of plants with the thiol-modifying agents S-methyl methanethiosulfonate or glutathione inhibited the nitrite-induced root abscission response. Synchrotron radiation-based Fourier transform infrared spectromicroscopy revealed higher levels of carbonylation in the abscission zone of dropped roots, indicative of reaction products of polysaccharides with potent free radical oxidants. We hypothesize that metabolic products of nitrite and NO react with H2O2 in the apoplast leading to free-radical-mediated cleavage of structural polysaccharides and consequent rapid root abscission. PMID:26217368

  16. An improved fruit transcriptome and the identification of the candidate genes involved in fruit abscission induced by carbohydrate stress in litchi

    PubMed Central

    Li, Caiqin; Wang, Yan; Huang, Xuming; Li, Jiang; Wang, Huicong; Li, Jianguo

    2015-01-01

    Massive young fruit abscission usually causes low and unstable yield in litchi (Litchi chinensis Sonn.), an important fruit crop cultivated in tropical and subtropical areas. However, the molecular mechanism of fruit drop has not been fully characterized. This study aimed at identification of molecular components involved in fruitlet abscission in litchi, for which reference genome is not available at present. An improved de novo transcriptome assembly was firstly achieved by using an optimized assembly software, Trinity. Using improved transcriptome assembly as reference, digital transcript abundance (DTA) profiling was performed to screen and identify candidate genes involved in fruit abscission induced by girdling plus defoliation (GPD), a treatment significantly decreased the soluble sugar contents causing carbohydrate stress to fruit. Our results showed that the increasing fruit abscission rate after GPD treatment was associated with higher ethylene production and lower glucose levels in fruit. A total of 2,771 differentially expressed genes were identified as GPD-responsive genes, 857 of which were defined by GO and KEGG enrichment analyses as the candidate genes involved in fruit abscission process. These genes were involved in diverse metabolic processes and pathways, including carbohydrate metabolism, plant hormone synthesis, and signaling, transcription factor activity and cell wall modification that were rapidly induced in the early stages (within 2 days after treatment). qRT-PCR was used to explore the expression pattern of 15 selected candidate genes in the abscission zone, pericarp, and seed, which confirmed the accuracy of our DTA data. More detailed information for different functional categories was also analyzed. This study profiled the gene expression related to fruit abscission induced by carbohydrate stress at whole transcriptome level and thus provided a better understanding of the regulatory mechanism of young fruit abscission in litchi. PMID

  17. Rheology and Relaxation Timescales of ABA Triblock Polymer Gels

    NASA Astrophysics Data System (ADS)

    Peters, Andrew; Lodge, Timothy

    When dissolved in a midblock selective solvent, ABA polymers form gels composed of aggregated end block micelles bridged by the midblocks. While much effort has been devoted to the study of the structure of these systems, the dynamics of these systems has received less attention. We examine the underlying mechanism of shear relaxation of ABA triblock polymer gels, especially as a function of chain length, composition, and concentration. Recent work using time-resolved small-angle neutron scattering of polystyrene (PS)-block-poly(ethylene-alt-propylene) (PEP) in squalane has elucidated many aspects of the dynamics of diblock chain exchange. By using rheology to study bulk relaxation phenomena of the triblock equivalent, PS-PEP-PS, we apply the knowledge gained from the chain exchange studies to bridge the gap between the molecular and macroscopic relaxation phenomena in PS-PEP-PS triblock gels.

  18. Total soil water content accounts for augmented ABA leaf concentration and stomatal regulation of split-rooted apple trees during heterogeneous soil drying.

    PubMed

    Einhorn, Todd C; Caspari, Horst W; Green, Steve

    2012-09-01

    A split-rooted containerized system was developed by approach grafting two, 1-year-old apple (Malus×domestica Borkh. cv 'Gala') trees to investigate the effect of soil moisture heterogeneity and total soil moisture content (θ(v)) on tree water relations, gas exchange, and leaf abscisic acid (ABA) concentration [ABA(leaf)]. Four irrigation treatments comprising a 2×2 factorial experiment of irrigation volume and placement were imposed over a 30-day period: control (C) [>100% of crop evapotranspiration (ET(c))] applied to both containers; PRD100 (>100% ET(c)) applied to one container only; and two treatments receiving 50% ET(c) applied to either one (PRD50) or both containers (DI50). Irrigation between PRD (partial rootzone drying) root compartments was alternated when θ(v) reached ~35% of field capacity. Maximum daily sap flow of the irrigated roots of PRD100 exceeded that of C roots throughout the experimental period. Pre-dawn water potential (Ψ(pd)) was similar between C and PRD100; however, daily water use and mid-day gas exchange of PRD100 was 30% lower. Slightly higher [ABA(leaf)] was observed in PRD100, but the effect was not significant and could not explain the observed reductions in leaf gas exchange. Both 50% ET(c) treatments had similar, but lower θ(v), Ψ(pd), and gas exchange, and higher [ABA(leaf)] than C and PRD100. Regardless of treatment, the container having the lower θ(v) of a split-rooted system correlated poorly with [ABA(leaf)], but when θ(v) of both containers or θ(v) of the container possessing the higher soil moisture was used, the relationship markedly improved. These results imply that apple canopy gas exchange and [ABA(leaf)] are responsive to the total soil water environment.

  19. Salt tolerance in soybean WF-7 is partially regulated by ABA and ROS signaling and involves withholding toxic Cl- ions from aerial tissues.

    PubMed

    Ren, Shuxin; Weeda, Sarah; Li, Haiwen; Whitehead, Brodie; Guo, Yangdong; Atalay, Asmare; Parry, John

    2012-08-01

    Salt tolerance in plants is a complex trait involving multiple mechanisms. Understanding these mechanisms and their regulation will assist in developing novel strategies to engineer salt-tolerant crops. In the current study, we investigated salt-tolerant mechanisms in soybean (Glycine max) cultivar WF-7 in comparison to salt-sensitive Union. In vivo and in vitro salt assays demonstrated the salt tolerance of WF-7 at the seedling stage and during germination. After a 10-day 200 mM NaCl treatment, chlorophyll content in Union was reduced by 50 % compared to a 17 % reduction in WF-7. WF-7 was also less affected by abscisic acid (ABA) and NaCl during germination than Union. Upon ABA and NaCl treatment, the ABA-responsive genes SCOF1, ASN1, bZIP44, and AAPK1 are differentially expressed in WF-7 and Union seedlings. These results suggest that salt tolerance in WF-7 is in part regulated through an ABA-dependent pathway. In addition, following a 4-day 200 mM NaCl treatment, WF-7 produced more H₂O₂ than Union indicating the involvement of reactive oxygen species (ROS) in regulating salt tolerance in WF-7. Yet another mechanism WF-7 employs is withholding toxic chloride (Cl⁻) ions from aerial tissues. Following 200 mM NaCl treatment, Cl⁻ accumulation was mostly localized to the roots of WF-7. In contrast, most of the Cl⁻ in Union was transported into the stems and leaves. Taken together, our results demonstrated a role of ABA and ROS in regulating salt tolerance in WF-7, and the critical role of Cl⁻ in NaCl-induced mortality in soybean. Key message Withholding toxic Cl⁻ ions from leaves and, to a lesser extent, stems, confers salt tolerance to soybean WF-7. In addition, ABA and ROS may be involved in salt-stress signal transduction.

  20. Overexpression of Rosa rugosa anthocyanidin reductase enhances tobacco tolerance to abiotic stress through increased ROS scavenging and modulation of ABA signaling.

    PubMed

    Luo, Ping; Shen, Yuxiao; Jin, Shuangxia; Huang, Shasha; Cheng, Xu; Wang, Zhen; Li, Penghui; Zhao, Jian; Bao, Manzhu; Ning, Guogui

    2016-04-01

    Anthocyanidin reductase (ANR) is a key enzyme involved in the biosynthesis of proanthocyanidins (PAs) and plays a role in the plant stress response. However, the mechanism by which ANR confers stress tolerance in plants is not understood. Here, we report the isolation of RrANR, the homologous gene from rose, and NtABF, an ABA-response related transcription factor gene from tobacco. These genes were characterized regarding their functions in stress responses through the use of transgenic, transcriptomic and physiological analyses. Over-expression of RrANR in tobacco resulted in an increased accumulation of both PAs and abscisic acid (ABA), and also enhanced stress tolerance. Transcriptomic analysis of these transgenic tobacco lines indicated that RrANR overexpression induced global transcriptomic changes, including these involved in oxidation/reduction, hormone response and secondary metabolism. Genes related to ABA biosynthesis and reactive oxygen species (ROS)-scavenging were up-regulated in RrANR transgenic lines, and these effects were phenocopied by the direct treatment of tobacco plants with PAs and ABA. Transcriptomic data from each of these treatments identified the upregulation of a putative NtABF. Furthermore, the up-regulation of NtABF in RrANR transformants or in PAs- and ABA-treated tobacco plants was associated with enhanced stress tolerance. Overexpression of NtABF in transgenic tobacco mimicked the effects of RrANR-transgenic plants with regard to the up-regulation of ROS-scavenging genes and an increase in oxidative tolerance. Taken together, our findings indicate that overexpression of RrANR results in an increase in plant tolerance to oxidative stress via increased scavenging of ROS and modulation of the ABA signaling pathway.

  1. 1-Aminocyclopropane-1-carboxylic acid and abscisic acid during the germination of sugar beet (Beta vulgaris L.): a comparative study of fruits and seeds.

    PubMed

    Hermann, Katrin; Meinhard, Juliane; Dobrev, Peter; Linkies, Ada; Pesek, Bedrich; Hess, Barbara; Machácková, Ivana; Fischer, Uwe; Leubner-Metzger, Gerhard

    2007-01-01

    The control of sugar beet (Beta vulgaris L.) germination by plant hormones was studied by comparing fruits and seeds. Treatment of sugar beet fruits and seeds with gibberellins, brassinosteroids, auxins, cytokinins, and jasmonates or corresponding hormone biosynthesis inhibitors did not appreciably affect radicle emergence of fruits or seeds. By contrast, treatment with ethylene or the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) promoted radicle emergence of fruits and seeds. Abscisic acid (ABA) acted as an antagonist of ethylene and inhibited radicle emergence of seeds, but not appreciably of fruits. High endogenous contents of ACC and of ABA were evident in seeds and pericarps of dry mature fruits, but declined early during imbibition. ABA-treatment of seeds and fruits induced seed ACC accumulation while ACC-treatment did not affect the seed ABA content. Transcripts of ACC oxidase (ACO, ethylene-forming enzyme) and ABA 8'-hydroxylase (CYP707A, ABA-degrading enzyme) accumulate in fruits and seeds upon imbibition. ABA and ACC and the pericarp did not affect the seed CYP707A transcript levels. By contrast, seed ACO transcript accumulation was promoted by ABA and by pericarp removal, but not by ACC. Quantification of the endogenous ABA and ACC contents, ABA and ACC leaching, and ethylene evolution, demonstrate that an embryo-mediated active ABA extrusion system is involved in keeping the endogenous seed ABA content low by 'active ABA leaching', while the pericarp restricts ACC leaching during imbibition. Sugar beet radicle emergence appears to be controlled by the pericarp, by ABA and ACC leaching, and by an ABA-ethylene antagonism that affects ACC biosynthesis and ACO gene expression.

  2. Arabidopsis CBL interacting protein kinase 3 interacts with ABR1, an APETALA2 domain transcription factor, to regulate ABA responses.

    PubMed

    Sanyal, Sibaji K; Kanwar, Poonam; Yadav, Akhilesh K; Sharma, Cheshta; Kumar, Ashish; Pandey, Girdhar K

    2017-01-01

    Calcium (Ca(2+)) plays a vital role as a second messenger in several signaling pathways in plants. The calcineurin B-like proteins (CBLs) represent a family of plant calcium-binding proteins that function in propagating Ca(2+) signals by interacting with CBL interacting protein kinases (CIPKs). Phosphorylation of CBL by CIPK is essential for the module to display full activity towards its target protein. Previous genetic analysis showed that the function of CBL9-CIPK3 module was implicated in negatively regulating seed germination and early development. In the present study, we have biochemically investigated the interaction of CBL9-CIPK3 module and our findings show that CBL9 is phosphorylated by CIPK3. Moreover, Abscisic acid repressor 1 (ABR1) is identified as the downstream target of CIPK3 and CIPK3-ABR1 function to regulate ABA responses during seed germination. Our study also indicates that the role of ABR1 is not limited to seed germination but it also regulates the ABA dependent processes in the adult stage of plant development. Combining our results, we conclude that the CBL9-CIPK3-ABR1 pathway functions to regulate seed germination and ABA dependent physiological processes in Arabidopsis.

  3. FIA functions as an early signal component of abscisic acid signal cascade in Vicia faba guard cells.

    PubMed

    Sugiyama, Yusuke; Uraji, Misugi; Watanabe-Sugimoto, Megumi; Okuma, Eiji; Munemasa, Shintaro; Shimoishi, Yasuaki; Nakamura, Yoshimasa; Mori, Izumi C; Iwai, Sumio; Murata, Yoshiyuki

    2012-02-01

    An abscisic acid (ABA)-insensitive Vicia faba mutant, fia (fava bean impaired in ABA-induced stomatal closure) had previously been isolated. In this study, it was investigated how FIA functions in ABA signalling in guard cells of Vicia faba. Unlike ABA, methyl jasmonate (MeJA), H(2)O(2), and nitric oxide (NO) induced stomatal closure in the fia mutant. ABA did not induce production of either reactive oxygen species or NO in the mutant. Moreover, ABA did not suppress inward-rectifying K(+) (K(in)) currents or activate ABA-activated protein kinase (AAPK) in mutant guard cells. These results suggest that FIA functions as an early signal component upstream of AAPK activation in ABA signalling but does not function in MeJA signalling in guard cells of Vicia faba.

  4. Liming can decrease legume crop yield and leaf gas exchange by enhancing root to shoot ABA signalling.

    PubMed

    Rothwell, Shane A; Elphinstone, E David; Dodd, Ian C

    2015-04-01

    To meet future requirements for food production, sustainable intensive agricultural systems need to optimize nutrient availability to maximize yield, traditionally achieved by maintaining soil pH within an optimal range (6-6.5) by applying lime (calcium carbonate). However, a field trial that applied recommended liming rates to a sandy loam soil (increasing soil pH from 5.5 to 6.2) decreased pod yield of field bean (Vicia faba L. cv. Fuego) by ~30%. Subsequent pot trials, with liming that raised soil pH to 6.3-6.7, reduced stomatal conductance (g(s)) by 63, 26, and 59% in V. faba, bean (Phaseolus vulgaris), and pea (Pisum sativum), respectively. Furthermore, liming reduced shoot dry biomass by 16-24% in these species. Ionomic analysis of root xylem sap and leaf tissue revealed a decrease in phosphorus concentration that was correlated with decreased g(s): both reductions were partially reversed by adding superphosphate fertilizer. Further analysis of pea suggests that leaf gas exchange was reduced by a systemic increase (roots, xylem sap, and leaves) in the phytohormone abscisic acid (ABA) in response to lime-induced suboptimal plant phosphorus concentrations. Supplying synthetic ABA via the transpiration stream to detached pea leaves, at the same xylem sap concentrations induced by liming, decreased transpiration. Furthermore, the g(s) of the ABA-deficient mutant pea wilty was unresponsive to liming, apparently confirming that ABA mediates some responses to low phosphorus availability caused by liming. This research provides a detailed mechanistic understanding of the physiological processes by which lime application can limit crop yields, and questions the suitability of current liming recommendations.

  5. Liming can decrease legume crop yield and leaf gas exchange by enhancing root to shoot ABA signalling

    PubMed Central

    Rothwell, Shane A.; Elphinstone, E. David; Dodd, Ian C.

    2015-01-01

    To meet future requirements for food production, sustainable intensive agricultural systems need to optimize nutrient availability to maximize yield, traditionally achieved by maintaining soil pH within an optimal range (6–6.5) by applying lime (calcium carbonate). However, a field trial that applied recommended liming rates to a sandy loam soil (increasing soil pH from 5.5 to 6.2) decreased pod yield of field bean (Vicia faba L. cv. Fuego) by ~30%. Subsequent pot trials, with liming that raised soil pH to 6.3–6.7, reduced stomatal conductance (g s) by 63, 26, and 59% in V. faba, bean (Phaseolus vulgaris), and pea (Pisum sativum), respectively. Furthermore, liming reduced shoot dry biomass by 16–24% in these species. Ionomic analysis of root xylem sap and leaf tissue revealed a decrease in phosphorus concentration that was correlated with decreased g s: both reductions were partially reversed by adding superphosphate fertilizer. Further analysis of pea suggests that leaf gas exchange was reduced by a systemic increase (roots, xylem sap, and leaves) in the phytohormone abscisic acid (ABA) in response to lime-induced suboptimal plant phosphorus concentrations. Supplying synthetic ABA via the transpiration stream to detached pea leaves, at the same xylem sap concentrations induced by liming, decreased transpiration. Furthermore, the g s of the ABA-deficient mutant pea wilty was unresponsive to liming, apparently confirming that ABA mediates some responses to low phosphorus availability caused by liming. This research provides a detailed mechanistic understanding of the physiological processes by which lime application can limit crop yields, and questions the suitability of current liming recommendations. PMID:25740925

  6. [Accumulation of ABA and ODAP in Lathyrus sativus under water stress].

    PubMed

    Xing, G; Zhou, G; Li, Z; Cui, K

    2000-10-01

    The roots of fifteen days old Lathyrus sativus seedlings were treated by PEG, PEG + ABA and ABA, and their leaves were sampled to determine the contents of endogenic ABA, ODAP, MDA and H2O2 and the activity of superoxide dismutase, catalase, peroxidase and glutathione reductase. The results showed that after treated, the contents of ABA and ODAP in leaves increased markedly. The addition of exogenous ABA decreased the increment of MDA and H2O2 contents and retarded the attenuation of CAT activity, which were induced by PEG stress, and enhanced the GR activity. In addition, when materials were treated with exogenous ABA in a long time, the ABA content in leaves was increased markedly, and ODAP was then accumulated. There was no significant effect on metabolism of active oxygen in the early days(0-3 days) of ABA treatment, but the activities of SOD, POD, CAT and GR decreased, and the contents of MDA and H2O2 increased in leaves of Lathyrus sativus with the duration of ABA treatment(7-15 days). The results indicated that ABA could promote the accumulation of ODAP in leaves of Lathyrus sativus.

  7. Molecular basis of the core regulatory network in ABA responses: sensing, signaling and transport.

    PubMed

    Umezawa, Taishi; Nakashima, Kazuo; Miyakawa, Takuya; Kuromori, Takashi; Tanokura, Masaru; Shinozaki, Kazuo; Yamaguchi-Shinozaki, Kazuko

    2010-11-01

    ABA is a major phytohormone that regulates a broad range of plant traits and is especially important for adaptation to environmental conditions. Our understanding of the molecular basis of ABA responses in plants improved dramatically in 2009 and 2010, banner years for ABA research. There are three major components; PYR/PYL/ RCAR (an ABA receptor), type 2C protein phosphatase (PP2C; a negative regulator) and SNF1-related protein kinase 2 (SnRK2; a positive regulator), and they offer a double negative regulatory system, [PYR/PYL/RCAR-| PP2C-| SnRK2]. In the absence of ABA, PP2C inactivates SnRK2 by direct dephosphorylation. In response to environmental or developmental cues, ABA promotes the interaction of PYR/PYL/RCAR and PP2C, resulting in PP2C inhibition and SnRK2 activation. This signaling complex can work in both the nucleus and cytosol, as it has been shown that SnRK2 phosphorylates basic-domain leucine zipper (bZIP) transcription factors or membrane proteins. Several structural analyses of PYR/PYL/RCAR have provided the mechanistic basis for this 'core signaling' model, by elucidating the mechanism of ABA binding of receptors, or the 'gate-latch-lock' mechanism of interaction with PP2C in inhibiting activity. On the other hand, intercellular ABA transport had remained a major issue, as had intracellular ABA signaling. Recently, two plasma membrane-type ABC transporters were identified and shed light on the influx/efflux system of ABA, resolving how ABA is transported from cell to cell in plants. Our knowledge of ABA responses in plants has been greatly expanded from intracellular signaling to intercellular transport of ABA.

  8. Abscisic acid has a key role in modulating diverse plant-pathogen interactions.

    PubMed

    Fan, Jun; Hill, Lionel; Crooks, Casey; Doerner, Peter; Lamb, Chris

    2009-08-01

    We isolated an activation-tagged Arabidopsis (Arabidopsis thaliana) line, constitutive disease susceptibility2-1D (cds2-1D), that showed enhanced bacterial growth when challenged with various Pseudomonas syringae strains. Systemic acquired resistance and systemic PATHOGENESIS-RELATED GENE1 induction were also compromised in cds2-1D. The T-DNA insertion adjacent to NINE-CIS-EPOXYCAROTENOID DIOXYGENASE5 (NCED5), one of six genes encoding the abscisic acid (ABA) biosynthetic enzyme NCED, caused a massive increase in transcript level and enhanced ABA levels >2-fold. Overexpression of NCED genes recreated the enhanced disease susceptibility phenotype. NCED2, NCED3, and NCED5 were induced, and ABA accumulated strongly following compatible P. syringae infection. The ABA biosynthetic mutant aba3-1 showed reduced susceptibility to virulent P. syringae, and ABA, whether through exogenous application or endogenous accumulation in response to mild water stress, resulted in increased bacterial growth following challenge with virulent P. syringae, indicating that ABA suppresses resistance to P. syringae. Likewise ABA accumulation also compromised resistance to the biotrophic oomycete Hyaloperonospora arabidopsis, whereas resistance to the fungus Alternaria brassicicola was enhanced in cds2-1D plants and compromised in aba3-1 plants, indicating that ABA promotes resistance to this necrotroph. Comparison of the accumulation of salicylic acid and jasmonic acid in the wild type, cds2-1D, and aba3-1 plants challenged with P. syringae showed that ABA promotes jasmonic acid accumulation and exhibits a complex antagonistic relationship with salicylic acid. Our findings provide genetic evidence that the abiotic stress signal ABA also has profound roles in modulating diverse plant-pathogen interactions mediated at least in part by cross talk with the jasmonic acid and salicylic acid biotic stress signal pathways.

  9. FOREVER YOUNG FLOWER Negatively Regulates Ethylene Response DNA-Binding Factors by Activating an Ethylene-Responsive Factor to Control Arabidopsis Floral Organ Senescence and Abscission.

    PubMed

    Chen, Wei-Han; Li, Pei-Fang; Chen, Ming-Kun; Lee, Yung-I; Yang, Chang-Hsien

    2015-08-01

    In this study of Arabidopsis (Arabidopsis thaliana), we investigated the relationship between FOREVER YOUNG FLOWER (FYF) and Ethylene Response DNA-binding Factors (EDFs) and functionally analyzed a key FYF target, an Ethylene-Responsive Factor (ERF), that controls flower senescence/abscission. Ectopic expression of EDF1/2/3/4 caused promotion of flower senescence/abscission and the activation of the senescence-associated genes. The presence of a repressor domain in EDFs and the enhancement of the promotion of senescence/abscission in EDF1/2/3/4+SRDX (converting EDFs to strong repressors by fusion with the ERF-associated amphiphilic repression motif repression domain SRDX) transgenic plants suggested that EDFs act as repressors. The significant reduction of β-glucuronidase (GUS) expression by 35S:FYF in EDF1/2/3/4:GUS plants indicates that EDF1/2/3/4 functions downstream of FYF in regulating flower senescence/abscission. In this study, we also characterized an ERF gene, FOREVER YOUNG FLOWER UP-REGULATING FACTOR1 (FUF1), which is up-regulated by FYF during flower development. Ectopic expression of FUF1 caused similar delayed flower senescence/abscission as seen in 35S:FYF plants. This phenotype was correlated with deficient abscission zone formation, ethylene insensitivity, and down-regulation of EDF1/2/3/4 and abscission-associated genes in 35S:FUF1 flowers. In contrast, significant promotion of flower senescence/abscission and up-regulation of EDF1/2/3/4 were observed in 35S:FUF1+SRDX transgenic dominant-negative plants, in which FUF1 is converted to a potent repressor by fusion to an SRDX-suppressing motif. Thus, FUF1 acts as an activator in suppressing EDF1/2/3/4 function and senescence/abscission of the flowers. Our results reveal that FYF regulates flower senescence/abscission by negatively regulating EDF1/2/3/4, which is the downstream gene in the ethylene response, by activating FUF1 in Arabidopsis.

  10. Transcriptome analysis of Arabidopsis mutants suggests a crosstalk between ABA, ethylene and GSH against combined cold and osmotic stress

    PubMed Central

    Kumar, Deepak; Hazra, Saptarshi; Datta, Riddhi; Chattopadhyay, Sharmila

    2016-01-01

    The involvement of ethylene and abscisic acid in providing stress tolerance and defence response to plants is widely recognized. However, little is known about the cross-talk between glutathione with ethylene and abscisic acid to combat stress in planta. Here, transcriptome analysis of combined cold and osmotic stress treated Arabidopsis mutants were carried out to elucidate the crosstalk between the abscisic acid, ethylene and glutathione. Microarray experiment revealed the differential regulation of about 2313 and 4131 transcripts in ein2 (ethylene insensitive mutant) and aba1.6 (abscisic acid mutant) respectively. Functional analysis exposed common down-regulated stress and defence, secondary metabolite biosynthesis viz. phenylpropanoid, lignin and flavonols, redox and transcription factors related genes in ein2, aba1.6 and pad2.1 (glutathione mutant) in response to combined stress treatment. The reduced glutathione content was less in stress treated mutants in comparison to Col-0. Again, selective down-regulated transcripts in stress treated mutants were noted up-regulated after glutathione feeding. Some of the important differentially expressed genes were also validated by comparative proteomics analysis of stress treated mutants. In summary, our results suggested the role of ethylene and abscisic acid in inducing stress-responsive genes and proteins by activating glutathione biosynthesis to combat abiotic stress conditions in plant system. PMID:27845361

  11. Grape hexokinases are involved in the expression regulation of sucrose synthase- and cell wall invertase-encoding genes by glucose and ABA.

    PubMed

    Wang, Xiu-Qin; Zheng, Li-Li; Lin, Hao; Yu, Fei; Sun, Li-Hui; Li, Li-Mei

    2017-02-28

    Hexokinase (HXK, EC 2.7.1.1) is a multifunctional protein that both is involved in catalyzing the first step of glycolysis and plays an important role in sugar signaling. However, the supporting genetic evidence on hexokinases (CsHXKs) from grape (Vitis vinifera L. cv. Cabernet Sauvignon) berries has been lacking. Here, to investigate the role of CsHXK isoforms as glucose (Glc) and abscisic acid (ABA) sensors, we cloned two hexokinase isozymes, CsHXK1 and CsHXK2 with highly conserved genomic structure of nine exons and eight introns. We also found adenosine phosphate binding, substrate recognition and connection sites in their putative proteins. During grape berry development, the expression profiles of two CsHXK isoforms, sucrose synthases (SuSys) and cell wall invertase (CWINV) genes increased concomitantly with high levels of endogenous Glc and ABA. Furthermore, we showed that in wild type grape berry calli (WT), glucose repressed the expression levels of sucrose synthase (SuSy) and cell wall invertase (CWINV) genes, while ABA increased their expression levels. ABA could not only effectively improve the expression levels of SuSy and CWINV, but also block the repression induced by glucose on the expression of both genes. However, after silencing CsHXK1 or CsHXK2 in grape calli, SuSy and CWINV expression were enhanced, and the expressions of the two genes are insensitive in response to Glc treatment. Interestingly, exogenous ABA alone could not or less increase SuSy and CWINV expression in silencing CsHXK1 or CsHXK2 grape calli compared to WT. Meantime, ABA could not block the repression induced by glucose on the expression of SuSy and CWINV in CsHXK1 or CsHXK2 mutants. Therefore, Glc signal transduction depends on the regulation of CsHXK1 or CsHXK2. ABA signal was also disturbed by CsHXK1 or CsHXK2 silencing. The present results provide new insights into the regulatory role of Glc and ABA on the enzymes related to sugar metabolism in grape berry.

  12. Cross-species approaches to seed dormancy and germination: conservation and biodiversity of ABA-regulated mechanisms and the Brassicaceae DOG1 genes.

    PubMed

    Graeber, Kai; Linkies, Ada; Müller, Kerstin; Wunchova, Andrea; Rott, Anita; Leubner-Metzger, Gerhard

    2010-05-01

    Seed dormancy is genetically determined with substantial environmental influence mediated, at least in part, by the plant hormone abscisic acid (ABA). The ABA-related transcription factor ABI3/VP1 (ABA INSENSITIVE3/VIVIPAROUS1) is widespread among green plants. Alternative splicing of its transcripts appears to be involved in regulating seed dormancy, but the role of ABI3/VP1 goes beyond seeds and dormancy. In contrast, DOG1 (DELAY OF GERMINATION 1), a major quantitative trait gene more specifically involved in seed dormancy, was so far only known from Arabidopsis thaliana (AtDOG1) and whether it also has roles during the germination of non-dormant seeds was not known. Seed germination of Lepidium sativum ('garden cress') is controlled by ABA and its antagonists gibberellins and ethylene and involves the production of apoplastic hydroxyl radicals. We found orthologs of AtDOG1 in the Brassicaceae relatives L. sativum (LesaDOG1) and Brassica rapa (BrDOG1) and compared their gene structure and the sequences of their transcripts expressed in seeds. Tissue-specific analysis of LesaDOG1 transcript levels in L. sativum seeds showed that they are degraded upon imbibition in the radicle and the micropylar endosperm. ABA inhibits germination in that it delays radicle protrusion and endosperm weakening and it increased LesaDOG1 transcript levels during early germination due to enhanced transcription and/or inhibited degradation. A reduced decrease in LesaDOG1 transcript levels upon ABA treatment is evident in the late germination phase in both tissues. This temporal and ABA-related transcript expression pattern suggests a role for LesaDOG1 in the control of germination timing of non-dormant L. sativum seeds. The possible involvement of the ABA-related transcription factors ABI3 and ABI5 in the regulation of DOG1 transcript expression is discussed. Other species of the monophyletic genus Lepidium showed coat or embryo dormancy and are therefore highly suited for comparative

  13. SlNCED1 and SlCYP707A2: key genes involved in ABA metabolism during tomato fruit ripening.

    PubMed

    Ji, Kai; Kai, Wenbin; Zhao, Bo; Sun, Yufei; Yuan, Bing; Dai, Shengjie; Li, Qian; Chen, Pei; Wang, Ya; Pei, Yuelin; Wang, Hongqing; Guo, Yangdong; Leng, Ping

    2014-10-01

    Abscisic acid (ABA) plays an important role in fruit development and ripening. Here, three NCED genes encoding 9-cis-epoxycarotenoid dioxygenase (NCED, a key enzyme in the ABA biosynthetic pathway) and three CYP707A genes encoding ABA 8'-hydroxylase (a key enzyme in the oxidative catabolism of ABA) were identified in tomato fruit by tobacco rattle virus-induced gene silencing (VIGS). Quantitative real-time PCR showed that VIGS-treated tomato fruits had significant reductions in target gene transcripts. In SlNCED1-RNAi-treated fruits, ripening slowed down, and the entire fruit turned to orange instead of red as in the control. In comparison, the downregulation of SlCYP707A2 expression in SlCYP707A2-silenced fruit could promote ripening; for example, colouring was quicker than in the control. Silencing SlNCED2/3 or SlCYP707A1/3 made no significant difference to fruit ripening comparing RNAi-treated fruits with control fruits. ABA accumulation and SlNCED1transcript levels in the SlNCED1-RNAi-treated fruit were downregulated to 21% and 19% of those in control fruit, respectively, but upregulated in SlCYP707A2-RNAi-treated fruit. Silencing SlNCED1 or SlCYP707A2 by VIGS significantly altered the transcripts of a set of both ABA-responsive and ripening-related genes, including ABA-signalling genes (PYL1, PP2C1, and SnRK2.2), lycopene-synthesis genes (SlBcyc, SlPSY1 and SlPDS), and cell wall-degrading genes (SlPG1, SlEXP, and SlXET) during ripening. These data indicate that SlNCED1 and SlCYP707A2 are key genes in the regulation of ABA synthesis and catabolism, and are involved in fruit ripening as positive and negative regulators, respectively.

  14. Melatonin promotes seed germination under high salinity by regulating antioxidant systems, ABA and GA₄ interaction in cucumber (Cucumis sativus L.).

    PubMed

    Zhang, Hai-Jun; Zhang, Na; Yang, Rong-Chao; Wang, Li; Sun, Qian-Qian; Li, Dian-Bo; Cao, Yun-Yun; Weeda, Sarah; Zhao, Bing; Ren, Shuxin; Guo, Yang-Dong

    2014-10-01

    Although previous studies have found that melatonin can promote seed germination, the mechanisms involved in perceiving and signaling melatonin remain poorly understood. In this study, it was found that melatonin was synthesized during cucumber seed germination with a peak in melatonin levels occurring 14 hr into germination. This is indicative of a correlation between melatonin synthesis and seed germination. Meanwhile, seeds pretreated with exogenous melatonin (1 μM) showed enhanced germination rates under 150 mM NaCl stress compared to water-pretreated seeds under salinity stress. There are two apparent mechanisms by which melatonin alleviated salinity-induced inhibition of seed germination. Exogenous melatonin decreased oxidative damage induced by NaCl stress by enhancing gene expression of antioxidants. Under NaCl stress, compared to untreated control, the activities of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) were significantly increased by approximately 1.3-5.0-fold, with a concomitant 1.4-2.0-fold increase of CsCu-ZnSOD, CsFe-ZnSOD, CsCAT, and CsPOD in melatonin-pretreated seeds. Melatonin also alleviated salinity stress by affecting abscisic acid (ABA) and gibberellin acid (GA) biosynthesis and catabolism during seed germination. Compared to NaCl treatment, melatonin significantly up-regulated ABA catabolism genes (e.g., CsCYP707A1 and CsCYP707A2, 3.5 and 105-fold higher than NaCl treatment at 16 hr, respectively) and down-regulated ABA biosynthesis genes (e.g., CsNECD2, 0.29-fold of CK2 at 16 hr), resulting in a rapid decrease of ABA content during the early stage of germination. At the same time, melatonin positively up-regulated GA biosynthesis genes (e.g., GA20ox and GA3ox, 2.3 and 3.9-fold higher than NaCl treatment at 0 and 12 hr, respectively), contributing to a significant increase of GA (especially GA4) content. In this study, we provide new evidence suggesting that melatonin alleviates the

  15. A Putative PP2C-Encoding Gene Negatively Regulates ABA Signaling in Populus euphratica.

    PubMed

    Chen, Jinhuan; Zhang, Dongzhi; Zhang, Chong; Xia, Xinli; Yin, Weilun; Tian, Qianqian

    2015-01-01

    A PP2C homolog gene was cloned from the drought-treated cDNA library of Populus euphratica. Multiple sequence alignment analysis suggested that the gene is a potential ortholog of HAB1. The expression of this HAB1 ortholog (PeHAB1) was markedly induced by drought and moderately induced by ABA. To characterize its function in ABA signaling, we generated transgenic Arabidopsis thaliana plants overexpressing this gene. Transgenic lines exhibited reduced responses to exogenous ABA and reduced tolerance to drought compared to wide-type lines. Yeast two-hybrid analyses indicated that PeHAB1 could interact with the ABA receptor PYL4 in an ABA-independent manner. Taken together; these results indicated that PeHAB1 is a new negative regulator of ABA responses in poplar.

  16. A proteomic analysis of rice seed germination as affected by high temperature and ABA treatment.

    PubMed

    Liu, Shu-Jun; Xu, Heng-Heng; Wang, Wei-Qing; Li, Ni; Wang, Wei-Ping; Møller, Ian Max; Song, Song-Quan

    2015-05-01

    Seed germination is a critical phase in the plant life cycle, but the specific events associated with seed germination are still not fully understood. In this study, we used two-dimensional gel electrophoresis followed by mass spectrometry to investigate the changes in the proteome during imbibition of Oryza sativa seeds at optimal temperature with or without abscisic acid (ABA) and high temperature (germination thermoinhibition) to further identify and quantify key proteins required for seed germination. A total of 121 protein spots showed a significant change in abundance (1.5-fold increase/decrease) during germination under all conditions. Among these proteins, we found seven proteins specifically associated with seed germination including glycosyl hydrolases family 38 protein, granule-bound starch synthase 1, Os03g0842900 (putative steroleosin-B), N-carbamoylputrescine amidase, spermidine synthase 1, tubulin α-1 chain and glutelin type-A; and a total of 20 imbibition response proteins involved in energy metabolism, cell growth, cell defense and storage proteins. High temperature inhibited seed germination by decreasing the abundance of proteins involved in methionine metabolism, amino acid biosynthesis, energy metabolism, reserve degradation, protein folding and stress responses. ABA treatment inhibited germination and decreased the abundance of proteins associated with methionine metabolism, energy production and cell division. Our results show that changes in many biological processes including energy metabolism, protein synthesis and cell defense and rescue occurred as a result of all treatments, while enzymes involved in methionine metabolism and weakening of cell wall specifically accumulated when the seeds germinated at the optimal temperature.

  17. GENETIC ANALYSIS OF ABSCISIC ACID BIOSYNTHESIS

    SciTech Connect

    MCCARTY D R

    2012-01-10

    The carotenoid cleavage dioxygenases (CCD) catalyze synthesis of a variety of apo-carotenoid secondary metabolites in plants, animals and bacteria. In plants, the reaction catalyzed by the 11, 12, 9-cis-epoxy carotenoid dioxygenase (NCED) is the first committed and key regulated step in synthesis of the plant hormone, abscisic acid (ABA). ABA is a key regulator of plant stress responses and has critical functions in normal root and seed development. The molecular mechanisms responsible for developmental control of ABA synthesis in plant tissues are poorly understood. Five of the nine CCD genes present in the Arabidopsis genome encode NCED's involved in control of ABA synthesis in the plant. This project is focused on functional analysis of these five AtNCED genes as a key to understanding developmental regulation of ABA synthesis and dissecting the role of ABA in plant development. For this purpose, the project developed a comprehensive set of gene knockouts in the AtNCED genes that facilitate genetic dissection of ABA synthesis. These mutants were used in combination with key molecular tools to address the following specific objectives: (1) the role of ABA synthesis in root development; (2) developmental control of ABA synthesis in seeds; (3) analysis of ATNCED over-expressers; (4) preliminary crystallography of the maize VP14 protein.

  18. Regulation of hormone metabolism in Arabidopsis seeds: phytochrome regulation of abscisic acid metabolism and abscisic acid regulation of gibberellin metabolism.

    PubMed

    Seo, Mitsunori; Hanada, Atsushi; Kuwahara, Ayuko; Endo, Akira; Okamoto, Masanori; Yamauchi, Yukika; North, Helen; Marion-Poll, Annie; Sun, Tai-Ping; Koshiba, Tomokazu; Kamiya, Yuji; Yamaguchi, Shinjiro; Nambara, Eiji

    2006-11-01

    In a wide range of plant species, seed germination is regulated antagonistically by two plant hormones, abscisic acid (ABA) and gibberellin (GA). In the present study, we have revealed that ABA metabolism (both biosynthesis and inactivation) was phytochrome-regulated in an opposite fashion to GA metabolism during photoreversible seed germination in Arabidopsis. Endogenous ABA levels were decreased by irradiation with a red (R) light pulse in dark-imbibed seeds pre-treated with a far-red (FR) light pulse, and the reduction in ABA levels in response to R light was inhibited in a phytochrome B (PHYB)-deficient mutant. Expression of an ABA biosynthesis gene, AtNCED6, and the inactivation gene, CYP707A2, was regulated in a photoreversible manner, suggesting a key role for the genes in PHYB-mediated regulation of ABA metabolism. Abscisic acid-deficient mutants such as nced6-1, aba2-2 and aao3-4 exhibited an enhanced ability to germinate relative to wild type when imbibed in the dark after irradiation with an FR light pulse. In addition, the ability to synthesize GA was improved in the aba2-2 mutant compared with wild type during dark-imbibition after an FR light pulse. Activation of GA biosynthesis in the aba2-2 mutant was also observed during seed development. These data indicate that ABA is involved in the suppression of GA biosynthesis in both imbibed and developing seeds. Spatial expression patterns of the AtABA2 and AAO3 genes, responsible for last two steps of ABA biosynthesis, were distinct from that of the GA biosynthesis gene, AtGA3ox2, in both imbibed and developing seeds, suggesting that biosynthesis of ABA and GA in seeds occurs in different cell types.

  19. The plastid outer envelope protein OEP16 affects metabolic fluxes during ABA-controlled seed development and germination

    PubMed Central

    Pudelski, Birgit; Schock, Annette; Hoth, Stefan; Radchuk, Ruslana; Weber, Hans; Hofmann, Jörg; Sonnewald, Uwe; Soll, Jürgen; Philippar, Katrin

    2012-01-01

    Previously, the OEP16.1 channel pore in the outer envelope membrane of mature pea (Pisum sativum) chloroplasts in vitro has been characterized to be selective for amino acids. Isolation of OEP16.2, a second OEP16 isoform from pea, in the current study allowed membrane localization and gene expression of OEP16 to be followed throughout seed development and germination of Arabidopsis thaliana and P. sativum. Thereby it can be shown on the transcript and protein level that the isoforms OEP16.1 and OEP16.2 in both plant species are alternating: whereas OEP16.1 is prominent in early embryo development and first leaves of the growing plantlet, OEP16.2 dominates in late seed development stages, which are associated with dormancy and desiccation, as well as early germination events. Further, OEP16.2 expression in seeds is under control of the phytohormone abscisic acid (ABA), leading to an ABA-hypersensitive phenotype of germinating oep16 knockout mutants. In consequence, the loss of OEP16 causes metabolic imbalance, in particular that of amino acids during seed development and early germination. It is thus concluded that in vivo OEP16 most probably functions in shuttling amino acids across the outer envelope of seed plastids. PMID:22155670

  20. Differential abscisic acid regulation of guard cell slow anion channels in Arabidopsis wild-type and abi1 and abi2 mutants.

    PubMed Central

    Pei, Z M; Kuchitsu, K; Ward, J M; Schwarz, M; Schroeder, J I

    1997-01-01

    Abscisic acid (ABA) regulates vital physiological responses, and a number of events in the ABA signaling cascade remain to be identified. To allow quantitative analysis of genetic signaling mutants, patch-clamp experiments were developed and performed with the previously inaccessible Arabidopsis guard cells from the wild type and ABA-insensitive (abi) mutants. Slow anion channels have been proposed to play a rate-limiting role in ABA-induced stomatal closing. We now directly demonstrate that ABA strongly activates slow anion channels in wild-type guard cells. Furthermore, ABA-induced anion channel activation and stomatal closing were suppressed by protein phosphatase inhibitors. In abi1-1 and abi2-1 mutant guard cells, ABA activation of slow anion channels and ABA-induced stomatal closing were abolished. These impairments in ABA signaling were partially rescued by kinase inhibitors in abi1 but not in abi2 guard cells. These data provide cell biological evidence that the abi2 locus disrupts early ABA signaling, that abi1 and abi2 affect ABA signaling at different steps in the cascade, and that protein kinases act as negative regulators of ABA signaling in Arabidopsis. New models for ABA signaling pathways and roles for abi1, abi2, and protein kinases and phosphatases are discussed. PMID:9090884

  1. Ethylene-dependent/ethylene-independent ABA regulation of tomato plants colonized by arbuscular mycorrhiza fungi.

    PubMed

    Martín-Rodríguez, José Ángel; León-Morcillo, Rafael; Vierheilig, Horst; Ocampo, Juan Antonio; Ludwig-Müller, Jutta; García-Garrido, José Manuel

    2011-04-01

    We investigated the relationship between ABA and ethylene regulating the formation of the arbuscular mycorrhiza (AM) symbiosis in tomato (Solanum lycopersicum) plants and tried to define the specific roles played by each of these phytohormones in the mycorrhization process. We analysed the impact of ABA biosynthesis inhibition on mycorrhization by Glomus intraradices in transgenic tomato plants with an altered ethylene pathway. We also studied the effects on mycorrhization in sitiens plants treated with the aminoethoxyvinyl glycine hydrochloride (AVG) ethylene biosynthesis inhibitor and supplemented with ABA. In addition, the expression of plant and fungal genes involved in the mycorrhization process was studied. ABA biosynthesis inhibition qualitatively altered the parameters of mycorrhization in accordance with the plant's ethylene perception and ethylene biosynthesis abilities. Inhibition of ABA biosynthesis in wild-type plants negatively affected all the mycorrhization parameters studied, while tomato mutants impaired in ethylene synthesis only showed a reduced arbuscular abundance in mycorrhizal roots. Inhibition of ethylene synthesis in ABA-deficient sitiens plants increased the intensity of mycorrhiza development, while ABA application rescued arbuscule abundance in the root's mycorrhizal zones. The results of our study show an antagonistic interaction between ABA and ethylene, and different roles of each of the two hormones during AM formation. This suggests that a dual ethylene-dependent/ethylene-independent mechanism is involved in ABA regulation of AM formation.

  2. 77 FR 36231 - Americans With Disabilities Act (ADA) and Architectural Barriers Act (ABA) Accessibility...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-18

    ... standards for residential facilities are the Uniform Federal Accessibility Standards (UFAS). When HUD... residential facilities covered by the ABA are the Uniform Federal Accessibility Standards (UFAS).\\5\\ HUD...

  3. Root ABA Accumulation in Long-Term Water-Stressed Plants is Sustained by Hormone Transport from Aerial Organs.

    PubMed

    Manzi, Matías; Lado, Joanna; Rodrigo, María Jesús; Zacarías, Lorenzo; Arbona, Vicent; Gómez-Cadenas, Aurelio

    2015-12-01

    The reduced pool of the ABA precursors, β,β-carotenoids, in roots does not account for the substantial increase in ABA content in response to water stress (WS) conditions, suggesting that ABA could be transported from other organs. Basipetal transport was interrupted by stem-girdling, and ABA levels were determined in roots after two cycles of WS induced by transplanting plants to dry perlite. Leaf applications of isotope-labeled ABA and reciprocal grafting of ABA-deficient tomato mutants were used to confirm the involvement of aerial organs on root ABA accumulation. Disruption of basipetal transport reduced ABA accumulation in roots, and this decrease was more severe after two consecutive WS periods. This effect was linked to a sharp decrease in the β,β-carotenoid pool in roots in response to water deficit. Significant levels of isotope-labeled ABA were transported from leaves to roots, mainly in plants subjected to water dehydration. Furthermore, the use of different ABA-deficient tomato mutants in reciprocal grafting combinations with wild-type genotypes confirmed the involvement of aerial organs in the ABA accumulation in roots. In conclusion, accumulation of ABA in roots after long-term WS periods largely relies on the aerial organs, suggesting a reduced ability of the roots to synthesize ABA from carotenoids. Furthermore, plants are able to transport ABA basipetally to sustain high hormone levels in roots.

  4. Abscisic acid sensor RCAR7/PYL13, specific regulator of protein phosphatase coreceptors.

    PubMed

    Fuchs, Stefan; Tischer, Stefanie V; Wunschel, Christian; Christmann, Alexander; Grill, Erwin

    2014-04-15

    The plant hormone abscisic acid (ABA) acts both as a developmental signal and as an integrator of environmental cues such as drought and cold. ABA perception recruits an ABA-binding regulatory component [regulatory component of ABA receptor (RCAR)/PYR1/PYL] and an associated protein phosphatase 2C (PP2C). Phytohormone binding inactivates the phosphatase activity of the coreceptor, permitting phosphorelay of the ABA signal via downstream protein kinases. RCARs and PP2C coreceptors are represented by small protein families comprising 14 and 9 members in Arabidopsis, respectively. The specificity of the RCAR-PP2C interaction and the constraints contributing to specific combinations are poorly understood. In this contribution, we analyzed RCAR7/PYL13, which is characterized by three variant amino acid residues in the conserved ABA-binding pocket. RCAR7 regulated the phosphatase activity of the PP2Cs ABI1, ABI2, and PP2CA in vitro at nanomolar ABA levels; however, it was unable to regulate the structurally related hypersensitive to ABA 1 (HAB1). Site-directed mutagenesis of HAB1 established ABA-dependent regulation by RCAR7. Conversion of the noncanonical amino acid residues of RCAR7 into the consensus ABA-binding pocket did not perceptibly change receptor function. Ectopic expression of RCAR7 in Arabidopsis resulted in ABA hypersensitivity affecting gene regulation, seed germination, and stomatal closure. The RCAR7 loss-of-function mutant revealed no changes in ABA responses, similar to the RCAR9 knockout line, whereas the combined deficiency of RCAR7 and RCAR9 resulted in ABA-insensitive seed germination. The study shows a role of RCAR7 in early plant development, proves its ABA receptor function, and identifies structural constraints of RCAR7-PP2C interaction.

  5. Rapid changes in leaf elongation, ABA and water status during the recovery phase following application of water stress in two durum wheat varieties differing in drought tolerance.

    PubMed

    Mahdid, Mohamed; Kameli, Abdelkrim; Ehlert, Christina; Simonneau, Thierry

    2011-10-01

    This study aims to investigate the role of Abscisic acid (ABA) in water potential and turgor variations as well as growth recovery during the first phase of a rapid water stress induced by PEG6000. Two wheat varieties (Triticum durum L.), MBB (more tolerant) and OZ (less productive under drought), were grown in aerated nutrient solutions. Leaf elongation kinetics of the growing leaf 3 was estimated using LVDT. Water potential was measured using a pressure chamber; osmotic potential was estimated from expressed sap of elongation zone, turgor pressure of the same zone of leaf three was estimated directly by pressure probe. Growth rapidly ceased for a period of about one hour after the addition of PEG, gradual recovery was then observed for about 2 h. A significant difference was found in the % recovery of Leaf Elongation Rate (LER) and ABA between the two varieties, leading to better water status in MBB compared to OZ. The results of this study showed the possible role of ABA on growth resumption by the increase of relative water content and turgor via osmotic adjustment during the stress period in the leaves, which indicates the importance of OA in the resumption of LER even in the short term under conditions of water deficit. Full recovery of turgor but not of LER at the end stress period suggested the possible effect on cell wall extensibility (hardening) even at short term resulting from the rapid accumulation of ABA.

  6. H2O2 and ABA signaling are responsible for the increased Na+ efflux and water uptake in Gossypium hirsutum L. roots in the non-saline side under non-uniform root zone salinity.

    PubMed

    Kong, Xiangqiang; Luo, Zhen; Dong, Hezhong; Eneji, A Egrinya; Li, Weijiang

    2016-04-01

    Non-uniform root salinity increases the Na(+)efflux, water use, and growth of the root in non-saline side, which may be regulated by some form of signaling induced by the high-salinity side. However, the signaling and its specific function have remained unknown. Using a split-root system to simulate a non-uniform root zone salinity in Gossypium hirsutum L., we showed that the up-regulated expression of sodium efflux-related genes (SOS1, SOS2, PMA1, and PMA2) and water uptake-related genes (PIP1 and PIP2) was possibly involved in the elevated Na(+) efflux and water use in the the roots in the non-saline side. The increased level of indole acetic acid (IAA) in the non-saline side was the likely cause of the increased root growth. Also, the abscisic acid (ABA) and H2O2 contents in roots in the non-saline side increased, possibly due to the increased expression of their key biosynthesis genes, NCED and RBOHC, and the decreased expression of ABA catabolic CYP707A genes. Exogenous ABA added to the non-saline side induced H2O2 generation by up-regulating the RBOHC gene, but this was decreased by exogenous fluridone. Exogenous H2O2 added to the non-saline side reduced the ABA content by down-regulating NCED genes, which can be induced by diphenylene iodonium (DPI) treatment in the non-saline side, suggesting a feedback mechanism between ABA and H2O2.Both exogenous ABA and H2O2 enhanced the expression of SOS1, PIP1;7 ,PIP2;2, and PIP2;10 genes, but these were down-regulated by fluridone and DPI, suggesting that H2O2 and ABA are important signals for increasing root Na(+) efflux and water uptake in the roots in the non-saline side.

  7. Structural basis and functions of abscisic acid receptors PYLs

    PubMed Central

    Zhang, Xing L.; Jiang, Lun; Xin, Qi; Liu, Yang; Tan, Jian X.; Chen, Zhong Z.

    2015-01-01

    Abscisic acid (ABA) plays a key role in many developmental processes and responses to adaptive stresses in plants. Recently, a new family of nucleocytoplasmic PYR/PYL/RCAR (PYLs) has been identified as bona fide ABA receptors. PYLs together with protein phosphatases type-2C (PP2Cs), Snf1 (Sucrose-non-fermentation 1)-related kinases subfamily 2 (SnRK2s) and downstream substrates constitute the core ABA signaling network. Generally, PP2Cs inactivate SnRK2s kinases by physical interaction and direct dephosphorylation. Upon ABA binding, PYLs change their conformations and then contact and inhibit PP2Cs, thus activating SnRK2s. Here, we reviewed the recent progress in research regarding the structures of the core signaling pathways of ABA, including the (+)-ABA, (−)-ABA and ABA analogs pyrabactin as well as 6AS perception by PYLs, SnRK2s mimicking PYLs in binding PP2Cs. PYLs inhibited PP2Cs in both the presence and absence of ABA and activated SnRK2s. The present review elucidates multiple ABA signal perception and transduction by PYLs, which might shed light on how to design small chemical compounds for improving plant performance in the future. PMID:25745428

  8. Evolution of Abscisic Acid Synthesis and Signaling Mechanisms

    PubMed Central

    Hauser, Felix; Waadt, Rainer; Schroeder, Julian I.

    2011-01-01

    The plant hormone abscisic acid (ABA) mediates seed dormancy, controls seedling development and triggers tolerance to abiotic stresses, including drought. Core ABA signaling components consist of a recently identified group of ABA receptor proteins of the PYRABACTIN RESISTANCE (PYR)/REGULATORY COMPONENT OF ABA RECEPTOR (RCAR) family that act as negative regulators of members of the PROTEIN PHOSPHATASE 2C (PP2C) family. Inhibition of PP2C activity enables activation of SNF1-RELATED KINASE 2 (SnRK2) protein kinases, which target downstream components, including transcription factors, ion channels and NADPH oxidases. These and other components form a complex ABA signaling network. Here, an in depth analysis of the evolution of components in this ABA signaling network shows that (i) PYR/RCAR ABA receptor and ABF-type transcription factor families arose during land colonization of plants and are not found in algae and other species, (ii) ABA biosynthesis enzymes have evolved to plant- and fungal-specific forms, leading to different ABA synthesis pathways, (iii) existing stress signaling components, including PP2C phosphatases and SnRK kinases, were adapted for novel roles in this plant-specific network to respond to water limitation. In addition, evolutionarily conserved secondary structures in the PYR/RCAR ABA receptor family are visualized. PMID:21549957

  9. Evolution of abscisic acid synthesis and signaling mechanisms.

    PubMed

    Hauser, Felix; Waadt, Rainer; Schroeder, Julian I

    2011-05-10

    The plant hormone abscisic acid (ABA) mediates seed dormancy, controls seedling development and triggers tolerance to abiotic stresses, including drought. Core ABA signaling components consist of a recently identified group of ABA receptor proteins of the PYRABACTIN RESISTANCE (PYR)/REGULATORY COMPONENT OF ABA RECEPTOR (RCAR) family that act as negative regulators of members of the PROTEIN PHOSPHATASE 2C (PP2C) family. Inhibition of PP2C activity enables activation of SNF1-RELATED KINASE 2 (SnRK2) protein kinases, which target downstream components, including transcription factors, ion channels and NADPH oxidases. These and other components form a complex ABA signaling network. Here, an in depth analysis of the evolution of components in this ABA signaling network shows that (i) PYR/RCAR ABA receptor and ABF-type transcription factor families arose during land colonization of plants and are not found in algae and other species, (ii) ABA biosynthesis enzymes have evolved to plant- and fungal-specific forms, leading to different ABA synthesis pathways, (iii) existing stress signaling components, including PP2C phosphatases and SnRK kinases, were adapted for novel roles in this plant-specific network to respond to water limitation. In addition, evolutionarily conserved secondary structures in the PYR/RCAR ABA receptor family are visualized.

  10. Abscisic acid signalling when soil moisture is heterogeneous: decreased photoperiod sap flow from drying roots limits abscisic acid export to the shoots.

    PubMed

    Dodd, Ian C; Egea, Gregorio; Davies, William J

    2008-09-01

    To investigate the contribution of different parts of the root system to total sap flow and leaf xylem abscisic acid (ABA) concentration ([X-ABA](leaf)), individual sunflower (Helianthus annuus L.) shoots were grafted onto the root systems of two plants grown in separate pots and sap flow through each hypocotyl measured below the graft union. During deficit irrigation (DI), both pots received the same irrigation volumes, while during partial root zone drying (PRD) one pot ('wet') was watered and another ('dry') was not. During PRD, once soil water content (theta) decreased below a threshold, the fraction of sap flow from drying roots declined. As theta declined, root xylem ABA concentration increased in both irrigation treatments, and [X-ABA](leaf) increased in DI plants, but [X-ABA](leaf) of PRD plants actually decreased within a certain theta range. A simple model that weighted ABA contributions of wet and dry root systems to [X-ABA](leaf) according to the sap flow from each, better predicted [X-ABA](leaf) of PRD plants than either [X-ABA](dry), [X-ABA](wet) or their mean. Model simulations revealed that [X-ABA](leaf) during PRD exceeded that of DI with moderate soil drying, but continued soil drying (such that sap flow from roots in drying soil ceased) resulted in the opposite effect.

  11. Multipolar mitosis and aneuploidy after chrysotile treatment: a consequence of abscission failure and cytokinesis regression

    PubMed Central

    Cortez, Beatriz Araujo; Teixeira, Paula Rezende; Redick, Sambra; Doxsey, Stephen; Machado-Santelli, Glaucia Maria

    2016-01-01

    Chrysotile, like other types of asbestos, has been associated with mesothelioma, lung cancer and asbestosis. However, the cellular abnormalities induced by these fibers involved in cancer development have not been elucidated yet. Previous works show that chrysotile fibers induce features of cancer cells, such as aneuploidy, multinucleation and multipolar mitosis. In the present study, normal and cancer derived human cell lines were treated with chrysotile and the cellular and molecular mechanisms related to generation of aneuploid cells was elucidated. The first alteration observed was cytokinesis regression, the main cause of multinucleated cells formation and centrosome amplification. The multinucleated cells formed after cytokinesis regression were able to progress through cell cycle and generated aneuploid cells after abnormal mitosis. To understand the process of cytokinesis regression, localization of cytokinetic proteins was investigated. It was observed mislocalization of Anillin, Aurora B, Septin 9 and Alix in the intercellular bridge, and no determination of secondary constriction and abscission sites. Fiber treatment also led to overexpression of genes related to cancer, cytokinesis and cell cycle. The results show that chrysotile fibers induce cellular and molecular alterations in normal and tumor cells that have been related to cancer initiation and progression, and that tetraploidization and aneuploid cell formation are striking events after fiber internalization, which could generate a favorable context to cancer development. PMID:26788989

  12. Reed-Sternberg Cells Form by Abscission Failure in the Presence of Functional Aurora B Kinase

    PubMed Central

    Maia, André F.; Ribeiro, Susana A.; Pontes, Patrícia; Bickmore, Wendy; Earnshaw, William C.; Sambade, Clara

    2015-01-01

    Large multinucleated Reed-Sternberg cells (RS) and large mononucleated Hodgkin cells (H) are traditionally considered to be the neoplastic population in classical Hodgkin lymphoma, (cHL) and postulated to promote the disease. However, the contribution of these larger cells to the progression of cHL remains debatable. We used established cHL cell lines and cHL cellular fractions composed of small mononucleated cells only or enriched in large RS/H cells to investigate RS/H cell origin and to characterize the cells which they derive from. We confirm that the small mononucleated cells give rise to RS/H cells, and we show that the latter proliferate significantly more slowly than the small cells. By using live-cell imaging, we demonstrate that binucleated RS cells are generated by failure of abscission when a few small cells attempt to divide. Finally, our results reveal that the small mononucleated cells are chromosomally unstable, but this is unlikely to be related to a malfunctioning chromosomal passenger protein complex. We propose that the small mononucleated cells, rather than the RS/H cells, are the main drivers of cHL. PMID:25933052

  13. Analysis of Phosphorylation of the Receptor-Like Protein Kinase HAESA during Arabidopsis Floral Abscission

    PubMed Central

    Taylor, Isaiah; Wang, Ying; Seitz, Kati; Baer, John; Bennewitz, Stefan; Mooney, Brian P.; Walker, John C.

    2016-01-01

    Receptor-like protein kinases (RLKs) are the largest family of plant transmembrane signaling proteins. Here we present functional analysis of HAESA, an RLK that regulates floral organ abscission in Arabidopsis. Through in vitro and in vivo analysis of HAE phosphorylation, we provide evidence that a conserved phosphorylation site on a region of the HAE protein kinase domain known as the activation segment positively regulates HAE activity. Additional analysis has identified another putative activation segment phosphorylation site common to multiple RLKs that potentially modulates HAE activity. Comparative analysis suggests that phosphorylation of this second activation segment residue is an RLK specific adaptation that may regulate protein kinase activity and substrate specificity. A growing number of RLKs have been shown to exhibit biologically relevant dual specificity toward serine/threonine and tyrosine residues, but the mechanisms underlying dual specificity of RLKs are not well understood. We show that a phospho-mimetic mutant of both HAE activation segment residues exhibits enhanced tyrosine auto-phosphorylation in vitro, indicating phosphorylation of this residue may contribute to dual specificity of HAE. These results add to an emerging framework for understanding the mechanisms and evolution of regulation of RLK activity and substrate specificity. PMID:26784444

  14. Augmin shapes the anaphase spindle for efficient cytokinetic furrow ingression and abscission

    PubMed Central

    Uehara, Ryota; Kamasaki, Tomoko; Hiruma, Shota; Poser, Ina; Yoda, Kinya; Yajima, Junichiro; Gerlich, Daniel W.; Goshima, Gohta

    2016-01-01

    During anaphase, distinct populations of microtubules (MTs) form by either centrosome-dependent or augmin-dependent nucleation. It remains largely unknown whether these different MT populations contribute distinct functions to cytokinesis. Here we show that augmin-dependent MTs are required for the progression of both furrow ingression and abscission. Augmin depletion reduced the accumulation of anillin, a contractile ring regulator at the cell equator, yet centrosomal MTs were sufficient to mediate RhoA activation at the furrow. This defect in contractile ring organization, combined with incomplete spindle pole separation during anaphase, led to impaired furrow ingression. During the late stages of cytokinesis, astral MTs formed bundles in the intercellular bridge, but these failed to assemble a focused midbody structure and did not establish tight linkage to the plasma membrane, resulting in furrow regression. Thus augmin-dependent acentrosomal MTs and centrosomal MTs contribute to nonredundant targeting mechanisms of different cytokinesis factors, which are required for the formation of a functional contractile ring and midbody. PMID:26764096

  15. Multipolar mitosis and aneuploidy after chrysotile treatment: a consequence of abscission failure and cytokinesis regression.

    PubMed

    Cortez, Beatriz Araujo; Rezende-Teixeira, Paula; Redick, Sambra; Doxsey, Stephen; Machado-Santelli, Glaucia Maria

    2016-02-23

    Chrysotile, like other types of asbestos, has been associated with mesothelioma, lung cancer and asbestosis. However, the cellular abnormalities induced by these fibers involved in cancer development have not been elucidated yet. Previous works show that chrysotile fibers induce features of cancer cells, such as aneuploidy, multinucleation and multipolar mitosis. In the present study, normal and cancer derived human cell lines were treated with chrysotile and the cellular and molecular mechanisms related to generation of aneuploid cells was elucidated. The first alteration observed was cytokinesis regression, the main cause of multinucleated cells formation and centrosome amplification. The multinucleated cells formed after cytokinesis regression were able to progress through cell cycle and generated aneuploid cells after abnormal mitosis. To understand the process of cytokinesis regression, localization of cytokinetic proteins was investigated. It was observed mislocalization of Anillin, Aurora B, Septin 9 and Alix in the intercellular bridge, and no determination of secondary constriction and abscission sites. Fiber treatment also led to overexpression of genes related to cancer, cytokinesis and cell cycle. The results show that chrysotile fibers induce cellular and molecular alterations in normal and tumor cells that have been related to cancer initiation and progression, and that tetraploidization and aneuploid cell formation are striking events after fiber internalization, which could generate a favorable context to cancer development.

  16. Regulators of PP2C phosphatase activity function as abscisic acid sensors.

    PubMed

    Ma, Yue; Szostkiewicz, Izabela; Korte, Arthur; Moes, Danièle; Yang, Yi; Christmann, Alexander; Grill, Erwin

    2009-05-22

    The plant hormone abscisic acid (ABA) acts as a developmental signal and as an integrator of environmental cues such as drought and cold. Key players in ABA signal transduction include the type 2C protein phosphatases (PP2Cs) ABI1 and ABI2, which act by negatively regulating ABA responses. In this study, we identify interactors of ABI1 and ABI2 which we have named regulatory components of ABA receptor (RCARs). In Arabidopsis, RCARs belong to a family with 14 members that share structural similarity with class 10 pathogen-related proteins. RCAR1 was shown to bind ABA, to mediate ABA-dependent inactivation of ABI1 or ABI2 in vitro, and to antagonize PP2C action in planta. Other RCARs also mediated ABA-dependent regulation of ABI1 and ABI2, consistent with a combinatorial assembly of receptor complexes.

  17. [ABA accumulation and distribution during the leaf tissues shows its role stomatal conductance regulation under short-term salinity].

    PubMed

    Akhiiarova, G R; Fricke, W; Veselov, D S; Kudoiarova, G R; Veselov, S Iu

    2006-01-01

    The regulative role of ABA in the rapid plant stomatal reactions in response to salinity was investigated. The influence of the short-term salinity on the overall ABA accumulation and its distribution within the mature leaf (revealed by immunohystochemical technique) and stomatal conductance of barley (Hordeum vulgare L.) were determined. Rapid bulk leaf ABA accumulation and increase in ABA immunolabeling in the mesophyl and guard cells of stomata were shown. The bulk ABA increasing in mature barley leaves coincided with stomatal closure induced by salt treatment indicating on the ABA contribution to the rapid stomatal closure.

  18. FRET-based reporters for the direct visualization of abscisic acid concentration changes and distribution in Arabidopsis

    PubMed Central

    Waadt, Rainer; Hitomi, Kenichi; Nishimura, Noriyuki; Hitomi, Chiharu; Adams, Stephen R; Getzoff, Elizabeth D; Schroeder, Julian I

    2014-01-01

    Abscisic acid (ABA) is a plant hormone that regulates plant growth and development and mediates abiotic stress responses. Direct cellular monitoring of dynamic ABA concentration changes in response to environmental cues is essential for understanding ABA action. We have developed ABAleons: ABA-specific optogenetic reporters that instantaneously convert the phytohormone-triggered interaction of ABA receptors with PP2C-type phosphatases to send a fluorescence resonance energy transfer (FRET) signal in response to ABA. We report the design, engineering and use of ABAleons with ABA affinities in the range of 100–600 nM to map ABA concentration changes in plant tissues with spatial and temporal resolution. High ABAleon expression can partially repress Arabidopsis ABA responses. ABAleons report ABA concentration differences in distinct cell types, ABA concentration increases in response to low humidity and NaCl in guard cells and to NaCl and osmotic stress in roots and ABA transport from the hypocotyl to the shoot and root. DOI: http://dx.doi.org/10.7554/eLife.01739.001 PMID:24737861

  19. Induction of Lipid and Oleosin Biosynthesis by (+)-Abscisic Acid and Its Metabolites in Microspore-Derived Embryos of Brassica napus L.cv Reston (Biological Responses in the Presence of 8[prime]-Hydroxyabscisic Acid).

    PubMed Central

    Zou, J.; Abrams, G. D.; Barton, D. L.; Taylor, D. C.; Pomeroy, M. K.; Abrams, S. R.

    1995-01-01

    Microspore-derived (MD) embryos of Brassica napus L. cv Reston were used to test the effects of (+)-abscisic acid ([(+)-ABA]) and its metabolites, 8[prime]-hydroxyabscisic acid (8[prime]-OH ABA) and (-)-phaseic acid (PA), on the accumulation of very long-chain monounsaturated fatty acids (VLCMFAs) and induction of genes encoding a 19-kD oleosin protein and a [delta]15 desaturase during embryogenesis. Developing early to mid-cotyledonary MD embryos at 16 to 19 d in culture were treated with 10 [mu]M hormone/metabolite for 4 d. At various times during incubation, embryos and medium were analyzed to determine levels of hormone/metabolite, VLCMFAs, and oleosin or [delta]15 desaturase transcripts. The VLCMFAs, 20:1 and 22:1, primarily in triacylglycerols, increased by 200% after 72 h in the presence of (+)-ABA and 8[prime]-OH ABA relative to the control. In contrast, treatment with PA for 72 h had little effect (20% increase) on the level of VLCMFAs. The first 24 to 72 h of (+)-ABA treatment were critical in the induction of VLCMFA biosynthesis, with 8[prime]-OH ABA lagging slightly behind (+)-ABA in promoting this response. The accumulation of VLCMFAs was positively correlated with an increase in elongase activity. (+)-ABA and its 8[prime]-OH ABA metabolite induced the accumulation of a 19-kD oleosin transcript within 2 to 4 h in culture. In addition, both (+)-ABA and 8[prime]-OH ABA induced the same level of [delta]15 desaturase transcript by 8 h. PA had no effect on the induction of either oleosin or [delta]15 desaturase transcripts. To our knowledge, this is the first report of the biological activity of 8[prime]-OH ABA and of stimulatory effects of (+)-ABA and 8[prime]-OH ABA on lipid and oleosin biosynthesis. PMID:12228493

  20. Antagonistic effects of abscisic acid and jasmonates on salt stress-inducible transcripts in rice roots.

    PubMed Central

    Moons, A; Prinsen, E; Bauw, G; Van Montagu, M

    1997-01-01

    Abscisic acid (ABA) and jasmonates have been implicated in responses to water deficit and wounding. We compared the molecular and physiological effects of jasmonic acid (JA) (< or = 10 microM), ABA, and salt stress in roots of rice. JA markedly induced a cationic peroxidase, two novel 32- and 28-kD proteins, acidic PR-1 and PR-10 pathogenesis-related proteins, and the salt stress-responsive SalT protein in roots. Most JA-responsive proteins (JIPs) from roots also accumulated when plants were subjected to salt stress. None of the JIPs accumulated when plants were treated with ABA. JA did not induce an ABA-responsive group 3 late-embryogenesis abundant (LEA) protein. Salt stress and ABA but not JA induced oslea3 transcript accumulation. By contrast, JA, ABA, and salt stress induced transcript accumulation of salT and osdrr, which encodes a rice PR-10 protein. However, ABA also negatively affected salT transcript accumulation, whereas JA negatively affected ABA-induced oslea3 transcript levels. Endogenous root ABA and methyl jasmonate levels showed a differential increase with the dose and the duration of salt stress. The results indicate that ABA and jasmonates antagonistically regulated the expression of salt stress-inducible proteins associated with water deficit or defense responses. PMID:9437865

  1. Disruption of abscisic acid signaling constitutively activates Arabidopsis resistance to the necrotrophic fungus Plectosphaerella cucumerina.

    PubMed

    Sánchez-Vallet, Andrea; López, Gemma; Ramos, Brisa; Delgado-Cerezo, Magdalena; Riviere, Marie-Pierre; Llorente, Francisco; Fernández, Paula Virginia; Miedes, Eva; Estevez, José Manuel; Grant, Murray; Molina, Antonio

    2012-12-01

    Plant resistance to necrotrophic fungi is regulated by a complex set of signaling pathways that includes those mediated by the hormones salicylic acid (SA), ethylene (ET), jasmonic acid (JA), and abscisic acid (ABA). The role of ABA in plant resistance remains controversial, as positive and negative regulatory functions have been described depending on the plant-pathogen interaction analyzed. Here, we show that ABA signaling negatively regulates Arabidopsis (Arabidopsis thaliana) resistance to the necrotrophic fungus Plectosphaerella cucumerina. Arabidopsis plants impaired in ABA biosynthesis, such as the aba1-6 mutant, or in ABA signaling, like the quadruple pyr/pyl mutant (pyr1pyl1pyl2pyl4), were more resistant to P. cucumerina than wild-type plants. In contrast, the hab1-1abi1-2abi2-2 mutant impaired in three phosphatases that negatively regulate ABA signaling displayed an enhanced susceptibility phenotype to this fungus. Comparative transcriptomic analyses of aba1-6 and wild-type plants revealed that the ABA pathway negatively regulates defense genes, many of which are controlled by the SA, JA, or ET pathway. In line with these data, we found that aba1-6 resistance to P. cucumerina was partially compromised when the SA, JA, or ET pathway was disrupted in this mutant. Additionally, in the aba1-6 plants, some genes encoding cell wall-related proteins were misregulated. Fourier transform infrared spectroscopy and biochemical analyses of cell walls from aba1-6 and wild-type plants revealed significant differences in their Fourier transform infrared spectratypes and uronic acid and cellulose contents. All these data suggest that ABA signaling has a complex function in Arabidopsis basal resistance, negatively regulating SA/JA/ET-mediated resistance to necrotrophic fungi.

  2. The role of abscisic acid in regulating cucumber fruit development and ripening and its transcriptional regulation.

    PubMed

    Wang, Yanping; Wang, Ya; Ji, Kai; Dai, Shengjie; Hu, Ying; Sun, Liang; Li, Qian; Chen, Pei; Sun, Yufei; Duan, Chaorui; Wu, Yan; Luo, Hao; Zhang, Dian; Guo, Yangdong; Leng, Ping

    2013-03-01

    Cucumber (Cucumis sativus L.), a kind of fruit usually harvested at the immature green stage, belongs to non-climacteric fruit. To investigate the contribution of abscisic acid (ABA) to cucumber fruit development and ripening, variation in ABA level was investigated and a peak in ABA level was found in pulp before fruit get fully ripe. To clarify this point further, exogenous ABA was applied to cucumber fruits at two different development stages. Results showed that ABA application at the turning stage promotes cucumber fruit ripening, while application at the immature green stage had inconspicuous effects. In addition, with the purpose of understanding the transcriptional regulation of ABA, two partial cDNAs of CsNCED1 and CsNCED2 encoding 9-cis-epoxycarotenoid dioxygenase (NCED), a key enzyme in ABA biosynthetic pathway; one partial cDNA of CsCYP707A1 for 8'-hydroxylase, a key enzyme in the oxidative catabolism of ABA and two partial cDNAs of CsBG1 and CsBG2 for β-glucosidase (BG) that hydrolyzes ABA glucose ester (ABA-GE) to release active ABA were cloned from cucumber. The DNA and deduced amino acid sequences of these obtained genes respectively showed high similarities to their homologous genes in other plants. Real-time PCR analysis revealed that ABA content may be regulated by its biosynthesis (CsNCEDs), catabolism (CsCYP707A1) and reactivation genes (CsBGs) at the transcriptional level during cucumber fruit development and ripening, in response to ABA application, dehydration and pollination, among which CsNCED1, CsCYP707A1 and CsBG1 were highly expressed in pulp and may play more important roles in regulating ABA metabolism.

  3. Mechanisms of abscisic acid-mediated control of stomatal aperture.

    PubMed

    Munemasa, Shintaro; Hauser, Felix; Park, Jiyoung; Waadt, Rainer; Brandt, Benjamin; Schroeder, Julian I

    2015-12-01

    Drought stress triggers an increase in the level of the plant hormone abscisic acid (ABA), which initiates a signaling cascade to close stomata and reduce water loss. Recent studies have revealed that guard cells control cytosolic ABA concentration through the concerted actions of biosynthesis, catabolism as well as transport across membranes. Substantial progress has been made at understanding the molecular mechanisms of how the ABA signaling core module controls the activity of anion channels and thereby stomatal aperture. In this review, we focus on our current mechanistic understanding of ABA signaling in guard cells including the role of the second messenger Ca(2+) as well as crosstalk with biotic stress responses.

  4. Uprooting an abscisic acid paradigm: Shoots are the primary source.

    PubMed

    McAdam, Scott A M; Manzi, Matías; Ross, John J; Brodribb, Timothy J; Gómez-Cadenas, Aurelio

    2016-06-02

    In the past, a conventional wisdom has been that abscisic acid (ABA) is a xylem-transported hormone that is synthesized in the roots, while acting in the shoot to close stomata in response to a decrease in plant water status. Now, however, evidence from two studies, which we have conducted independently, challenges this root-sourced ABA paradigm. We show that foliage-derived ABA has a major influence over root development and that leaves are the predominant location for ABA biosynthesis during drought stress.

  5. Identification and functional expression of the pepper RING type E3 ligase, CaDTR1, involved in drought stress tolerance via ABA-mediated signalling

    PubMed Central

    Joo, Hyunhee; Lim, Chae Woo; Lee, Sung Chul

    2016-01-01

    Drought negatively affects plant growth and development, thereby leading to loss of crop productivity. Several plant E3 ubiquitin ligases act as positive or negative regulators of abscisic acid (ABA) and thus play important roles in the drought stress response. Here, we show that the C3HC4-type RING finger E3 ligase, CaDTR1, regulates the drought stress response via ABA-mediated signalling. CaDTR1 contains an amino-terminal RING finger motif and two carboxyl-terminal hydrophobic regions; the RING finger motif functions during attachment of ubiquitins to the target proteins, and the carboxyl-terminal hydrophobic regions function during subcellular localisation. The expression of CaDTR1 was induced by ABA, drought, and NaCl treatments. CaDTR1 localised in the nucleus and displayed in vitro E3 ubiquitin ligase activity. CaDTR1-silenced pepper plants exhibited a drought-sensitive phenotype characterised by high levels of transpirational water loss. On the other hand, CaDTR1-overexpressing (OX) Arabidopsis plants exhibited an ABA-hypersensitive phenotype during the germinative and post-germinative growth stages. Moreover, in contrast to CaDTR1-silenced pepper plants, CaDTR1-OX plants exhibited a drought-tolerant phenotype characterised by low levels of transpirational water loss via increased stomatal closure and high leaf temperatures. Our data indicate that CaDTR1 functions as a positive regulator of the drought stress response via ABA-mediated signalling. PMID:27439598

  6. From the Classroom to the Family Room: Using ABA for Best Behavior

    ERIC Educational Resources Information Center

    Smith, Dawn

    2010-01-01

    When it comes to supporting individuals with disabilities including Autism Spectrum Disorder (ASD), Applied Behavior Analysis (ABA) can be an invaluable tool in understanding and changing behavior. More than a technique or method, ABA is a disciplined approach rooted in science to teach specific skills and then reinforce them so individuals can…

  7. None of the As in ABA Stand for Autism: Dispelling the Myths

    ERIC Educational Resources Information Center

    Dillenburger, Karola; Keenan, Mickey

    2009-01-01

    Interventions that are based on scientific principles of applied behaviour analysis (ABA) are recognised as effective treatments for children with autism spectrum disorder (ASD) by many governments and professionals (Office of the Surgeon General, 2000; Ontario IBI Initiative, 2002). However, many still view ABA as one of many treatments for…

  8. Douglass Developmental Disabilities Center: An ABA Program for Children and Adults with Autism Spectrum Disorders

    ERIC Educational Resources Information Center

    Handleman, Jan S.; Harris, Sandra L.

    2005-01-01

    There is increasing evidence that Applied Behavior Analysis (ABA) is an effective, and often superior, method to teach children with Autism Spectrum Disorders ASD), than other methods. The Douglass Developmental Disabilities Center of Rutgers University (DDDC) has been using ABA for more than thirty years to teach toddlers, young children,…

  9. A novel ABA insensitive mutant of Lotus japonicus with a wilty phenotype displays unaltered nodulation regulation.

    PubMed

    Biswas, Bandana; Chan, Pick Kuen; Gresshoff, Peter M

    2009-05-01

    An ABA insensitive mutant, Beyma, was isolated in Lotus japonicus MG-20 from an EMS mutagenesis population using root growth inhibition to applied ABA as the screening criterion. (The name 'Beyma' was taken from the Australian Aboriginal language, Wagiman, beyma, meaning 'drying up'.) The stable mutant that segregates as a dominant Mendelian mutation is insensitive to ABA induced inhibition of germination, vegetative growth, stomatal opening, as well as nodulation. Tissue ABA levels were normal, suggesting a sensitivity rather than biosynthesis mutation. It is slow-growing (50-70% of wild-type MG-20) and has a near-constitutive wilty phenotype associated with its inability to regulate stomatal opening. Whilst showing a wide range of ABA insensitive phenotypes, Beyma did not show alteration of nodule number control, as, in the absence of added ABA, the number and patterning (but not size) of nodules formed in the mutant were similar to that of MG-20. Split root experiments on MG-20 showed that application of ABA on one side of the root inhibited nodulation locally but not systemically. We propose that ABA is not involved directly in systemic autoregulation of nodulation (AON).

  10. Brief Report: Comparative ABA and DIR Trials in Twin Brothers with Autism

    ERIC Educational Resources Information Center

    Hilton, Jane C.; Seal, Brenda C.

    2007-01-01

    Trial interventions in DIR and ABA with twin brothers with autism were offered to help the parents choose one of the programs for their sons. Pre- and post-test scores on the Communication and Symbolic Behavior Scales (CSBS) revealed a slight gain in the composite score of the ABA child and a slight loss in the score of the DIR child. Contrasted…

  11. Leaf gas exchange and ABA accumulation in Phaseolus vulgaris genotypes of contrasting drought tolerance

    SciTech Connect

    Bertrand, A.; Castonguay, Y.; Nadeau, P. )

    1991-05-01

    Drought tolerance mechanisms in Phaseolus vulgaris (Pv) are still largely unknown. Gas exchange responses and ABA accumulation were monitored in Pv genotypes differing in their drought adaptation. Higher rates of photosynthesis were observed under well-watered conditions in drought sensitive genotypes. Water stress caused a significant reduction in leaf water potential and photosynthetic rates regardless of drought adaptation. Higher photosynthetic rates were maintained under stress conditions in one drought tolerant genotype. Interestingly water stress caused significant ABA accumulation only in this genotype. Root ABA levels were similar among genotypes and were not modified by water stress. Endogenous levels of free ABA in leaves and roots did not correlated with gas exchange response to water stress. These results differ from previous reports on genotypic variation in ABA accumulation under water stress.

  12. PP2C-like Promoter and Its Deletion Variants Are Induced by ABA but Not by MeJA and SA in Arabidopsis thaliana.

    PubMed

    Bhalothia, Purva; Sangwan, Chetna; Alok, Anshu; Mehrotra, Sandhya; Mehrotra, Rajesh

    2016-01-01

    Gene expression is mediated through interaction between cis regulatory elements and its cognate transcription factors. Cis regulatory elements are defined as non-coding DNA sequences that provide the binding sites for transcription factors and are clustered in the upstream region of genes. ACGT cis regulatory element is one of the important cis regulatory elements found to be involved in diverse biological processes like auxin response, salicylic acid (SA) response, UV light response, ABA response and jasmonic acid (JA) response. We identified through in silico analysis that the upstream region of protein phosphatase 2C (PP2C) gene has a distinct genetic architecture of ACGT elements. In the present study, the activation of the full length promoter and its deletion constructs like 900 base pair, 500 base pair, 400 base pair and NRM (Nathji Rajesh Mehrotra) were examined by stable transformation in Arabidopsis thaliana using β-glucuronidase as the reporter gene. Evaluation of deletion constructs of PP2C-like promoter was carried out in the presence of phytohormones like abscisic acid (ABA), SA and JA. Our result indicated that the full length and 900 base pair promoter-reporter constructs of PP2C-like promoter was induced in response to ABA but not to methyl jasmonate and SA.

  13. Modification of carotenoid levels by abscission agents and expression of carotenoid biosynthetic genes in 'valencia' sweet orange.

    PubMed

    Alferez, Fernando; Pozo, Luis V; Rouseff, Russell R; Burns, Jacqueline K

    2013-03-27

    The effect of 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMNP) and ethephon on peel color, flavedo carotenoid gene expression, and carotenoid accumulation was investigated in mature 'Valencia' orange ( Citrus sinensis L. Osbeck) fruit flavedo at three maturation stages. Abscission agent application altered peel color. CMNP was more effective than ethephon in promoting green-to-red (a) and blue-to-yellow (b) color at the middle and late maturation stages and total carotenoid changes at all maturation stages. Altered flow of carotenoid precursors during maturation due to abscission agents was suggested by changes in phytoene desaturase (Pds) and ζ-carotene desaturase (Zds) gene expression. However, each abscission agent affected downstream expression differentially. Ethephon application increased β-carotene hydroxilase (β-Chx) transcript accumulation 12-fold as maturation advanced from the early to middle and late stages. CMNP markedly increased β- and ε-lycopene cyclase (Lcy) transcript accumulation 45- and 15-fold, respectively, at midmaturation. Patterns of carotenoid accumulation in flavedo were supported in part by gene expression changes. CMNP caused greater accumulation of total flavedo carotenoids at all maturation stages when compared with ethephon or controls. In general, CMNP treatment increased total red carotenoids more than ethephon or the control but decreased total yellow carotenoids at each maturation stage. In control fruit flavedo, total red carotenoids increased and yellow carotenoids decreased as maturation progressed. Trends in total red carotenoids during maturation were consistent with measured a values. Changes in carotenoid accumulation and expression patterns in flavedo suggest that regulation of carotenoid accumulation is under transcriptional, translational, and post-translational control.

  14. Effect of pollinator-inflicted ovule damage on floral abscission in the yucca-yucca moth mutualism: the role of mechanical and chemical factors.

    PubMed

    Marr, Deborah L; Pellmyr, Olle

    2003-07-01

    The long-term persistence of obligate mutualisms (over 40 Mya in both fig/fig wasps and yucca/yucca moths) raises the question of how one species limits exploitation by the other species, even though there is selection pressure on individuals to maximize fitness. In the case of yuccas, moths serve as the plant's only pollinator, but eggs laid by the moths before pollination hatch into larvae that consume seeds. Previous studies have shown that flowers with high egg loads are more likely to abscise. This suggests that yucca flowers can select against moths that lay many eggs per flower through selective abscission of flowers; however, it is not known how yucca moths trigger floral abscission. We tested how the moth Tegeticula yuccasella triggers floral abscission during oviposition in Yucca filamentosa by examining the effects of ovipositor insertion and egg laying on ovule viability and floral abscission. Eggs are not laid at the site of ovipositor insertion: we used this separation to test whether wounded ovules were more closely associated with the ovipositor site or an egg's location. Using a tetrazolium stain to detect injured ovules, we determined whether the number of ovipositions affected the number of wounded ovules in naturally pollinated flowers. Two wounding experiments were used to test the effect of mechanical damage on the probability of floral abscission. The types of wounds in these experiments mimicked two types of oviposition-superficial oviposition in the ovary wall and oviposition into the locular cavity-that have been observed in species of Tegeticula. The effect of moth eggs on ovule viability was experimentally tested by culturing ovules in vitro, placing moth eggs on the ovules, and measuring changes in ovule viability with a tetrazolium stain. We found that ovules were physically wounded during natural oviposition. Ovules showed a visible wounding response in moth-pollinated flowers collected 7-12 h after oviposition. Exact location of

  15. Enhancing tolerance of rice (Oryza sativa) to simulated acid rain by exogenous abscisic acid.

    PubMed

    Wu, Xi; Liang, Chanjuan

    2017-02-01

    Abscisic acid (ABA) regulates much important plant physiological and biochemical processes and induces tolerance to different stresses. Here, we studied the regulation of exogenous ABA on adaptation of rice seedlings to simulated acid rain (SAR) stress by measuring biomass dry weight, stomatal conductance, net photosynthesis rate, nutrient elements, and endogenous hormones. The application of 10 μM ABA alleviated the SAR-induced inhibition on growth, stomatal conductance, net photosynthesis rate, and decreases in contents of nutrient (K, Mg, N, and P) and hormone (auxin, gibberellins, and zeatin). Moreover, 10 μM ABA could stimulate the Ca content as signaling molecules under SAR stress. Contrarily, the application of 100 μM ABA aggravated the SAR-induced inhibition on growth, stomatal conductance, net photosynthesis rate, and contents of nutrient and hormone. The results got after a 5-day recovery (without SAR) show that exogenous 10 μM ABA can promote self-restoration process in rice whereas 100 μM ABA hindered the restoration by increasing deficiency of nutrients and disturbing the balance of hormones. These results confirmed that exogenous ABA at proper concentration could enhance the tolerance of rice to SAR stress.

  16. [Tissue culture of medicinal plant and abscisic acid].

    PubMed

    Fang, Hui-Yong; Zhu, Hong; Yao, Jian-Xun; Jia, Cai-Feng; Shan, Gao-Wei; Li, Min-Hui

    2013-01-01

    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.

  17. Metabolic pathways regulated by abscisic acid, salicylic acid and γ-aminobutyric acid in association with improved drought tolerance in creeping bentgrass (Agrostis stolonifera).

    PubMed

    Li, Zhou; Yu, Jingjin; Peng, Yan; Huang, Bingru

    2017-01-01

    Abscisic acid (ABA), salicylic acid (SA) and γ-aminobutyric acid (GABA) are known to play roles in regulating plant stress responses. This study was conducted to determine metabolites and associated pathways regulated by ABA, SA and GABA that could contribute to drought tolerance in creeping bentgrass (Agrostis stolonifera). Plants were foliar sprayed with ABA (5 μM), GABA (0.5 mM) and SA (10 μM) or water (untreated control) prior to 25 days drought stress in controlled growth chambers. Application of ABA, GABA or SA had similar positive effects on alleviating drought damages, as manifested by the maintenance of lower electrolyte leakage and greater relative water content in leaves of treated plants relative to the untreated control. Metabolic profiling showed that ABA, GABA and SA induced differential metabolic changes under drought stress. ABA mainly promoted the accumulation of organic acids associated with tricarboxylic acid cycle (aconitic acid, succinic acid, lactic acid and malic acid). SA strongly stimulated the accumulation of amino acids (proline, serine, threonine and alanine) and carbohydrates (glucose, mannose, fructose and cellobiose). GABA enhanced the accumulation of amino acids (GABA, glycine, valine, proline, 5-oxoproline, serine, threonine, aspartic acid and glutamic acid) and organic acids (malic acid, lactic acid, gluconic acid, malonic acid and ribonic acid). The enhanced drought tolerance could be mainly due to the enhanced respiration metabolism by ABA, amino acids and carbohydrates involved in osmotic adjustment (OA) and energy metabolism by SA, and amino acid metabolism related to OA and stress-defense secondary metabolism by GABA.

  18. Abscisic acid and aldehyde oxidase activity in maize ear leaf and grain relative to post-flowering photosynthetic capacity and grain-filling rate under different water/nitrogen treatments.

    PubMed

    Qin, Shujun; Zhang, Zongzheng; Ning, Tangyuan; Ren, Shizhong; Su, Licheng; Li, Zengjia

    2013-09-01

    This study investigated changes in leaf abscisic acid (ABA) concentrations and grain ABA concentrations in two maize cultivars and analyzed the following relationships under different water/nitrogen treatments: leaf ABA concentrations and photosynthetic parameters; leaf ABA concentrations and grain ABA concentrations; leaf/grain ABA concentrations and grain-filling parameters; and aldehyde oxidase (AO, EC 1.2.3.1) activities and ABA concentrations. The ear leaf average AO activities and ABA concentrations were lower in the controlled release urea treatments compared with the conventional urea treatments. The average AO activities in the grains were higher in the controlled release urea treatments, and the ABA concentrations were significantly increased at 11-30 DAF. The Pn and ABA concentrations in ear leaves were negatively correlated. And the Gmean were positively correlated with the grain ABA concentrations at 11-30 DAF and negatively correlated with the leaf ABA concentrations at 20 and 40-50 DAF. The grain ABA concentrations and leaf ABA concentrations were positively correlated. Thus, the Gmean were closely related to the AO activities and to the ear leaf and grain ABA concentrations. As compared to other treatments, the subsoiling and controlled release urea treatment promoted the uptake of water and nitrogen by maize, increased the photosynthetic capacity of the ear leaves, increased the grain-filling rate, and improved the movement of photosynthetic assimilates toward the developing grains. In the cultivar Z958, higher ABA concentrations in grains at 11-30 DAF and lower ABA concentrations in ear leaves during the late grain-filling stage, resulted in higher grain-filling rate and increased accumulation of photosynthetic products (relative to the cultivar D3).

  19. An Abscisic Acid-Activated and Calcium-Independent Protein Kinase from Guard Cells of Fava Bean.

    PubMed

    Li, J.; Assmann, S. M.

    1996-12-01

    Abscisic acid (ABA) regulation of stomatal aperture is known to involve both Ca2+-dependent and Ca2+-independent signal transduction pathways. Electrophysiological studies suggest that protein phosphorylation is involved in ABA action in guard cells. Using biochemical approaches, we identified an ABA-activated and Ca2+- independent protein kinase (AAPK) from guard cell protoplasts of fava bean. Autophosphorylation of AAPK was rapidly (~1 min) activated by ABA in a Ca2+- independent manner. ABA-activated autophosphorylation of AAPK occurred on serine but not on tyrosine residues and appeared to be guard cell specific. AAPK phosphorylated histone type III-S on serine and threonine residues, and its activity toward histone type III-S was markedly stimulated in ABA-treated guard cell protoplasts. Our results suggest that AAPK may play an important role in the Ca2+-independent ABA signaling pathways of guard cells.

  20. Inhibition of Abscisic Acid Biosynthesis in Cercospora rosicola by Inhibitors of Gibberellin Biosynthesis and Plant Growth Retardants

    PubMed Central

    Norman, Shirley M.; Poling, Stephen M.; Maier, Vincent P.; Orme, Edward D.

    1983-01-01

    The fungus Cercospora rosicola produces abscisic acid (ABA) as a secondary metabolite. We developed a convenient system using this fungus to determine the effects of compounds on the biosynthesis of ABA. Inasmuch as ABA and the gibberellins (GAs) both arise via the isoprenoid pathway, it was of interest to determine if inhibitors of GA biosynthesis affect ABA biosynthesis. All five putative inhibitors of GA biosynthesis tested inhibited ABA biosynthesis. Several plant growth retardants with poorly understood actions in plants were also tested; of these, six inhibited ABA biosynthesis to varying degrees and two had no effect. Effects of plant growth retardants on various branches of the isoprenoid biosynthetic pathway may help to explain some of the diverse and unexpected results reported for these compounds. Knowledge that certain inhibitors of GA biosynthesis also have the ability to inhibit ABA biosynthesis in C. rosicola indicates the need for further studies in plants on the mode of action of these compounds. PMID:16662775

  1. 40 CFR 63.1297 - Standards for slabstock flexible polyurethane foam production-HAP ABA emissions from the...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... polyurethane foam production-HAP ABA emissions from the production line. 63.1297 Section 63.1297 Protection of... foam production—HAP ABA emissions from the production line. (a) Each owner or operator of a new or... § 63.1293(a)(1) shall control HAP ABA emissions from the slabstock polyurethane foam production line...

  2. Endogenous Levels of Abscisic Acid and Decanoic Acid in Dutch Iris Bulbs and the Influence of Abscisic Acid and Decanoic Acid on Iris Meristems Cultured In Vitro1

    PubMed Central

    Doss, Robert P.; Kimura, Yosh; Christian, James K.

    1983-01-01

    Abscisic acid (ABA) and decanoic acid inhibited shoot elongation and floral development of Dutch iris (Iris hollandica Hoog. cv Ideal) meristems cultured in vitro. No synergism with respect to inhibition of leaf growth between ABA and decanoic acid was observed. With monthly harvest dates, from July 10, 1981 to October 10, 1981, there was a progressive decrease in endogenous level of free ABA in `Ideal' iris bulbs. Bulbs subjected to a full set of the usual preplanting storage conditions flowered, on average, 46 days after planting versus 194 days after planting for bulbs planted directly after harvest. ABA levels at harvest were 4- to 5-fold those after the preplanting storage treatment. In general, ABA levels did not correlate well with the length of time from planting until flowering of iris bulbs. Endogenous decanoic acid levels did not follow any pattern with respect to harvest date or postharvest treatment. After the postharvest high temperature treatment, there was about a 3-fold increase in nonscale decanoic acid concentration. Decanoic acid levels, in nonscale tissue, remained high after each of the other postharvest treatments. It is concluded that there is no good evidence to support the contention that either ABA or decanoic acid is directly involved in iris bulb dormancy. PMID:16663072

  3. An ABA-responsive DRE-binding protein gene from Setaria italica, SiARDP, the target gene of SiAREB, plays a critical role under drought stress.

    PubMed

    Li, Cong; Yue, Jing; Wu, Xiaowei; Xu, Cong; Yu, Jingjuan

    2014-10-01

    The DREB (dehydration-responsive element binding)-type transcription factors regulate the expression of stress-inducible genes by binding the DRE/CRT cis-elements in promoter regions. The upstream transcription factors that regulate the transcription of DREB transcription factors have not been clearly defined, although the function of DREB transcription factors in abiotic stress is known. In this study, an abscisic acid (ABA)-responsive DREB-binding protein gene (SiARDP) was cloned from foxtail millet (Setaria italica). The transcript level of SiARDP increased not only after drought, high salt, and low temperature stresses, but also after an ABA treatment in foxtail millet seedlings. Two ABA-responsive elements (ABRE1: ACGTGTC; ABRE2: ACGTGGC) exist in the promoter of SiARDP. Further analyses showed that two ABA-responsive element binding (AREB)-type transcription factors, SiAREB1 and SiAREB2, could physically bind to the ABRE core element in vitro and in vivo. The constitutive expression of SiARDP in Arabidopsis thaliana enhanced drought and salt tolerance during seed germination and seedling development, and overexpression of SiARDP in foxtail millet improved drought tolerance. The expression levels of target genes of SiARDP were upregulated in transgenic Arabidopsis and foxtail millet. These results reveal that SiARDP, one of the target genes of SiAREB, is involved in ABA-dependent signal pathways and plays a critical role in the abiotic stress response in plants.

  4. ABA and GA3 increase carbon allocation in different organs of grapevine plants by inducing accumulation of non-structural carbohydrates in leaves, enhancement of phloem area and expression of sugar transporters.

    PubMed

    Murcia, Germán; Pontin, Mariela; Reinoso, Herminda; Baraldi, Rita; Bertazza, Gianpaolo; Gómez-Talquenca, Sebastián; Bottini, Rubén; Piccoli, Patricia N

    2016-03-01

    Grape quality for winemaking depends on sugar accumulation and metabolism in berries. Abscisic acid (ABA) and gibberellins (GAs) have been reported to control sugar allocation in economically important crops, although the mechanisms involved are still unknown. The present study tested if ABA and gibberellin A3 (GA3) enhance carbon allocation in fruits of grapevines by modifying phloem loading, phloem area and expression of sugar transporters in leaves and berries. Pot-grown Vitis vinifera cv. Malbec plants were sprayed with ABA and GA3 solutions. The amount of soluble sugars in leaves and berries related to photosynthesis were examined at three points of berry growth: pre-veraison, full veraison and post-veraison. Starch levels and amylase activity in leaves, gene expression of sugar transporters in leaves and berries and phloem anatomy were examined at full veraison. Accumulation of glucose and fructose in berries was hastened in ABA-treated plants at the stage of full veraison, which was correlated with enhancement of Vitis vinifera HEXOSE TRANSPORTER 2 (VvHT2) and Vitis vinifera HEXOSE TRANSPORTER 6 (VvHT6) gene expression, increases of phloem area and sucrose content in leaves. On the other hand, GA3 increased the quantity of photoassimilates delivered to the stem thus increasing xylem growth. In conclusion, stimulation of sugar transport by ABA and GA3 to berries and stems, respectively, was due to build-up of non-structural carbohydrates in leaves, modifications in phloem tissue and modulation in gene expression of sugar transporters.

  5. The Magnesium-Chelatase H Subunit Binds Abscisic Acid and Functions in Abscisic Acid Signaling: New Evidence in Arabidopsis1[W][OA

    PubMed Central

    Wu, Fu-Qing; Xin, Qi; Cao, Zheng; Liu, Zhi-Qiang; Du, Shu-Yuan; Mei, Chao; Zhao, Chen-Xi; Wang, Xiao-Fang; Shang, Yi; Jiang, Tao; Zhang, Xiao-Feng; Yan, Lu; Zhao, Rui; Cui, Zi-Ning; Liu, Rui; Sun, Hai-Li; Yang, Xin-Ling; Su, Zhen; Zhang, Da-Peng

    2009-01-01

    Using a newly developed abscisic acid (ABA)-affinity chromatography technique, we showed that the magnesium-chelatase H subunit ABAR/CHLH (for putative abscisic acid receptor/chelatase H subunit) specifically binds ABA through the C-terminal half but not the N-terminal half. A set of potential agonists/antagonists to ABA, including 2-trans,4-trans-ABA, gibberellin, cytokinin-like regulator 6-benzylaminopurine, auxin indole-3-acetic acid, auxin-like substance naphthalene acetic acid, and jasmonic acid methyl ester, did not bind ABAR/CHLH. A C-terminal C370 truncated ABAR with 369 amino acid residues (631–999) was shown to bind ABA, which may be a core of the ABA-binding domain in the C-terminal half. Consistently, expression of the ABAR/CHLH C-terminal half truncated proteins fused with green fluorescent protein (GFP) in wild-type plants conferred ABA hypersensitivity in all major ABA responses, including seed germination, postgermination growth, and stomatal movement, and the expression of the same truncated proteins fused with GFP in an ABA-insensitive cch mutant of the ABAR/CHLH gene restored the ABA sensitivity of the mutant in all of the ABA responses. However, the effect of expression of the ABAR N-terminal half fused with GFP in the wild-type plants was limited to seedling growth, and the restoring effect of the ABA sensitivity of the cch mutant was limited to seed germination. In addition, we identified two new mutant alleles of ABAR/CHLH from the mutant pool in the Arabidopsis Biological Resource Center via Arabidopsis (Arabidopsis thaliana) Targeting-Induced Local Lesions in Genomes. The abar-2 mutant has a point mutation resulting in the N-terminal Leu-348→Phe, and the abar-3 mutant has a point mutation resulting in the N-terminal Ser-183→Phe. The two mutants show altered ABA-related phenotypes in seed germination and postgermination growth but not in stomatal movement. These findings support the idea that ABAR/CHLH is an ABA receptor and reveal

  6. Type B Heterotrimeric G Protein γ-Subunit Regulates Auxin and ABA Signaling in Tomato[OPEN

    PubMed Central

    Subramaniam, Gayathery; Trusov, Yuri; Hayashi, Satomi; Batley, Jacqueline

    2016-01-01

    Heterotrimeric G proteins composed of α, β, and γ subunits are central signal transducers mediating the cellular response to multiple stimuli in most eukaryotes. Gγ subunits provide proper cellular localization and functional specificity to the heterotrimer complex. Plant Gγ subunits, divided into three structurally distinct types, are more diverse than their animal counterparts. Type B Gγ subunits, lacking a carboxyl-terminal isoprenylation motif, are found only in flowering plants. We present the functional characterization of type B Gγ subunit (SlGGB1) in tomato (Solanum lycopersicum). We show that SlGGB1 is the most abundant Gγ subunit in tomato and strongly interacts with the Gβ subunit. Importantly, the green fluorescent protein-SlGGB1 fusion protein as well as the carboxyl-terminal yellow fluorescent protein-SlGGB1/amino-terminal yellow fluorescent protein-Gβ heterodimer were localized in the plasma membrane, nucleus, and cytoplasm. RNA interference-mediated silencing of SlGGB1 resulted in smaller seeds, higher number of lateral roots, and pointy fruits. The silenced lines were hypersensitive to exogenous auxin, while levels of endogenous auxins were lower or similar to those of the wild type. SlGGB1-silenced plants also showed strong hyposensitivity to abscisic acid (ABA) during seed germination but not in other related assays. Transcriptome analysis of the transgenic seeds revealed abnormal expression of genes involved in ABA sensing, signaling, and response. We conclude that the type B Gγ subunit SlGGB1 mediates auxin and ABA signaling in tomato. PMID:26668332

  7. Abscisic Acid Levels during Early Seed Development in Sechium edule Sw

    PubMed Central

    Vernieri, Paolo; Perata, Pierdomenico; Lorenzi, Roberto; Ceccarelli, Nello

    1989-01-01

    The time-course growth of single tissues in pollinated and unpollinated ovules of Sechium edule Sw. is described in relation to the endogenous levels of abscisic acid. Quantitation of abscisic acid (ABA) in the minute amounts of material obtained after ovule dissection has been performed by using a highly specific and sensitive solid-phase radioimmunoassay based on a monoclonal antibody raised against free (S)-ABA. While the absolute amount of ABA rises in both types of ovules, only in unpollinated ones does this leads to an increase in the hormone concentration. Infact in pollinated ovules the rapid growth following pollination prevents, through a dilution effect, the increase in ABA concentration. Growth patterns and endogenous ABA levels are similar for integuments and nucellus tissues either in pollinated or unpollinated ovules. It is suggested that the growth inhibition induced by the increase in ABA concentration after anthesis could be counteracted by the pollination triggered fast ovule growth. PMID:16667185

  8. Disruption of Abscisic Acid Signaling Constitutively Activates Arabidopsis Resistance to the Necrotrophic Fungus Plectosphaerella cucumerina1[W

    PubMed Central

    Sánchez-Vallet, Andrea; López, Gemma; Ramos, Brisa; Delgado-Cerezo, Magdalena; Riviere, Marie-Pierre; Llorente, Francisco; Fernández, Paula Virginia; Miedes, Eva; Estevez, José Manuel; Grant, Murray; Molina, Antonio

    2012-01-01

    Plant resistance to necrotrophic fungi is regulated by a complex set of signaling pathways that includes those mediated by the hormones salicylic acid (SA), ethylene (ET), jasmonic acid (JA), and abscisic acid (ABA). The role of ABA in plant resistance remains controversial, as positive and negative regulatory functions have been described depending on the plant-pathogen interaction analyzed. Here, we show that ABA signaling negatively regulates Arabidopsis (Arabidopsis thaliana) resistance to the necrotrophic fungus Plectosphaerella cucumerina. Arabidopsis plants impaired in ABA biosynthesis, such as the aba1-6 mutant, or in ABA signaling, like the quadruple pyr/pyl mutant (pyr1pyl1pyl2pyl4), were more resistant to P. cucumerina than wild-type plants. In contrast, the hab1-1abi1-2abi2-2 mutant impaired in three phosphatases that negatively regulate ABA signaling displayed an enhanced susceptibility phenotype to this fungus. Comparative transcriptomic analyses of aba1-6 and wild-type plants revealed that the ABA pathway negatively regulates defense genes, many of which are controlled by the SA, JA, or ET pathway. In line with these data, we found that aba1-6 resistance to P. cucumerina was partially compromised when the SA, JA, or ET pathway was disrupted in this mutant. Additionally, in the aba1-6 plants, some genes encoding cell wall-related proteins were misregulated. Fourier transform infrared spectroscopy and biochemical analyses of cell walls from aba1-6 and wild-type plants revealed significant differences in their Fourier transform infrared spectratypes and uronic acid and cellulose contents. All these data suggest that ABA signaling has a complex function in Arabidopsis basal resistance, negatively regulating SA/JA/ET-mediated resistance to necrotrophic fungi. PMID:23037505

  9. Validation of functional fetal autonomic brain age score fABAS in 5 min short recordings.

    PubMed

    Hoyer, Dirk; Schneider, Uwe; Kowalski, Eva-Maria; Schmidt, Alexander; Witte, Otto W; Schleußner, Ekkehard; Hatzmann, Wolfgang; Grönemeyer, Dietrich Hw; van Leeuwen, Peter

    2015-11-01

    With the objective of evaluating the functional maturation age and developmental disturbances we have previously introduced the fetal autonomic brain age score (fABAS) using 30 min fetal magnetocardiographic recordings (fMCG, Jena). The score is based on heart rate pattern indices that are related to universal principles of developmental biology. The present work aims at the validation of the fABAS methodology on 5 min recordings from an independent database (fMCG, Bochum).We found high agreement of fABAS obtained from Jena normal fetuses (5 min subsets, n =  364) and Bochum recordings (n =  322, normal fetuses). fABAS of 48 recordings from fetuses with intra-uterine growth restriction (IUGR, Bochum) was reduced in most of the cases, a result consistent with IUGR fetuses from Jena previously reported. fABAS calculated from 5 min snapshots only partly covers the accuracy when compared to fABAS from 30 min recordings. More precise diagnosis requires longer recordings.fABAS obtained from fMCG recordings is a strong candidate for standardized assessment of functional maturation age and developmental disturbances. Even 5 min recordings seem to be valuable for screening for maturation problems.

  10. Chemical Promotion of Endogenous Amounts of ABA in Arabidopsis thaliana by a Natural Product, Theobroxide.

    PubMed

    Yamashita, Yudai; Ota, Maremichi; Inoue, Yutaka; Hasebe, Youko; Okamoto, Masanori; Inukai, Tsuyoshi; Masuta, Chikra; Sakihama, Yasuko; Hashidoko, Yasuyuki; Kojima, Mikiko; Sakakibara, Hitoshi; Inage, Yasuyuki; Takahashi, Kosaku; Yoshihara, Teruhiko; Matsuura, Hideyuki

    2016-05-01

    Plant hormones are a group of structurally diverse small compounds that orchestrate the cellular processes governing proper plant growth and environmental adaptation. To understand the details of hormonal activity, we must study not only their inherent activities but also the cross-talk among plant hormones. In addition to their use in agriculture, plant chemical activators, such as probenazole and uniconazole, have made great contributions to understand hormonal cross-talk. However, the use of plant chemical activators is limited due to the lack of activators for certain hormones. For example, to the best of our knowledge, there are only a few chemical activators previously known to stimulate the accumulation of ABA in plants, such as absinazoles and proanthocyanidins. In many cases, antagonistic effects have been examined in experiments using exogenously applied ABA, although these studies did not account for biologically relevant concentrations. In this report, it was found that a natural product, theobroxide, had potential as a plant chemical activator for stimulating the accumulation of ABA. Using theobroxide, the antagonistic effect of ABA against GAs was proved without exogenously applying ABA or using mutant plants. Our results suggest that ABA levels could be chemically controlled to elicit ABA-dependent biological phenomena.

  11. Transcript and hormone analyses reveal the involvement of ABA-signalling, hormone crosstalk and genotype-specific biological processes in cold-shock response in wheat.

    PubMed

    Kalapos, Balázs; Dobrev, Petre; Nagy, Tibor; Vítámvás, Pavel; Györgyey, János; Kocsy, Gábor; Marincs, Ferenc; Galiba, Gábor

    2016-12-01

    The effect of one-day cold-shock on the transcriptome and phytohormones (auxin, cytokinins, abscisic, jasmonic and salicylic acids) was characterised in freezing-sensitive (Chinese Spring), highly freezing-tolerant (Cheyenne) and moderately freezing-tolerant (Chinese Spring substituted with Cheyenne's 5A chromosome) wheat genotypes. Altogether, 636 differentially expressed genes responding to cold-shock were identified. Defence genes encoding LEA proteins, dehydrins, chaperons and other temperature-stress responsive proteins were up-regulated in a genotype-independent manner. Abscisic acid was up-regulated by cold accompanied by adherent expression of its metabolic genes. Data revealed the involvement of particular routes within ABA-dependent signalling in response to cold-shock in the examined genotypes. Cold-shock affected gene expression along carbohydrate metabolic pathways. In photosynthesis, cold-shock changed the expression of a number of genes in the same way as it was previously reported for ABA. Overrepresentation analysis of the differentially expressed genes supported the ABA-signalling and carbohydrate metabolism results, and revealed some pronounced biological process GO categories associated with the cold-shock response of the genotypes. Protein network analysis indicated differences between the genotypes in the information flow along their signal perception and transduction, suggesting different biochemical and cellular strategies in their reaction to cold-shock.

  12. Environmental Nitrate Stimulates Abscisic Acid Accumulation in Arabidopsis Root Tips by Releasing It from Inactive Stores[OPEN

    PubMed Central

    2016-01-01

    Abscisic acid (ABA) signaling plays a major role in root system development, regulating growth and root architecture. However, the precise localization of ABA remains undetermined. Here, we present a mechanism in which nitrate signaling stimulates the release of bioactive ABA from the inactive storage form, ABA-glucose ester (ABA-GE). We found that ABA accumulated in the endodermis and quiescent center of Arabidopsis thaliana root tips, mimicking the pattern of SCARECROW expression, and (to lower levels) in the vascular cylinder. Nitrate treatment increased ABA levels in root tips; this stimulation requires the activity of the endoplasmic reticulum-localized, ABA-GE-deconjugating enzyme β-GLUCOSIDASE1, but not de novo ABA biosynthesis. Immunogold labeling demonstrated that ABA is associated with cytoplasmic structures near, but not within, the endoplasmic reticulum. These findings demonstrate a mechanism for nitrate-regulated root growth via regulation of ABA accumulation in the root tip, providing insight into the environmental regulation of root growth. PMID:26887919

  13. Overexpression of SlREV alters the development of the flower pedicel abscission zone and fruit formation in tomato.

    PubMed

    Hu, Guojian; Fan, Jing; Xian, Zhiqiang; Huang, Wei; Lin, Dongbo; Li, Zhengguo

    2014-12-01

    Versatile roles of REVOLUTA (REV), a Class III homeodomain-leucine zipper (HD-ZIP III) transcription factor, have been depicted mainly in Arabidopsis and Populus. In this study, we investigated the functions of its tomato homolog, namely SlREV. Overexpression of a microRNA166-resistant version of SlREV (35S::REV(Ris)) not only resulted in vegetative abnormalities such as curly leaves and fasciated stems, but also caused dramatic reproductive alterations including continuous production of flowers at the pedicel abscission zone (AZ) and ectopic fruit formation on receptacles. Microscopic analysis showed that meristem-like structures continuously emerged from the exodermises of the pedicel AZs and that ectopic carpels formed between the first and second whorl of floral buds in 35S::REV(Ris) plants. Transcriptional data suggest that SlREV may regulate genes related to meristem maintenance and cell differentiation in the development of the flower pedicel abscission zone, and modulate genes in homeodomain and MADS-box families and hormone pathways during fruit formation. Altogether, these results reveal novel roles of SlREV in tomato flower development and fruit formation.

  14. Photoprotectant improves photostability and bioactivity of abscisic acid under UV radiation.

    PubMed

    Gao, Fei; Hu, Tanglu; Tan, Weiming; Yu, Chunxin; Li, Zhaohu; Zhang, Lizhen; Duan, Liusheng

    2016-05-01

    Photosensitivity causes serious drawback for abscisic acid (ABA) application, but preferable methods to stabilize the compound were not found yet. To select an efficient photoprotectant for the improvement of photostability and bioactivity of ABA when exposed to UV light, we tested the effects of a photostabilizer bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (HS-770) and two UV absorbers 2-hydroxy-4-n-octoxy-benzophenone (UV-531) and 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (BP-4) with or without HS-770 on the photodegradation of ABA. Water soluble UV absorber BP-4 and oil soluble UV absorber UV-531 showed significant photo-stabilizing capability on ABA, possibly due to competitive energy absorption of UVB by the UV absorbers. The two absorbers showed no significant difference. Photostabilizer HS-770 accelerated the photodegradation of ABA and did not improve the photo-stabilizing capability of BP-4, likely due to no absorption in UVB region and salt formation with ABA and BP-4. Approximately 26% more ABA was kept when 280mg/l ABA aqueous solution was irradiated by UV light for 2h in the presence of 200mg/l BP-4. What's more, its left bioactivity on wheat seed (JIMAI 22) germination was greatly kept by BP-4, comparing to that of ABA alone. The 300 times diluent of 280mg/l ABA plus 200mg/l BP-4 after 2h irradiation showed more than 13% inhibition on shoot and root growth of wheat seed than that of ABA diluent alone. We concluded that water soluble UV absorber BP-4 was an efficient agent to keep ABA activity under UV radiation. The results could be used to produce photostable products of ABA compound or other water soluble agrichemicals which are sensitive to UV radiation. The frequencies and amounts of the agrichemicals application could be thereafter reduced.

  15. Rapid adjustment of guard-cell abscisic acid levels to current leaf-water status

    SciTech Connect

    Harris, M.J.; Outlaw, W.H. Jr. )

    1991-01-01

    Detached broad bean (Vicia faba L.) leaflets were water stressed; within 15 minutes, guard-cell abscisic acid (ABA) concentration increased ninefold. This result eliminates the apparent discrepancy raised by reports of no correlation between initial water-stress effects on stomata and leaf ABA concentration. Six hours after stress relief, guard-cell ABA concentration was near the prestress value, which would seem to implicate other factors in stress after-effects on stomata.

  16. Are we on the right track: Can our understanding of abscission in model systems promote or derail making improvements in less studied crops

    Technology Transfer Automated Retrieval System (TEKTRAN)

    As the world population grows and resources and climate conditions change, crop improvement continues to be one of the most important challenges for agriculturalists. The yield and quality of many crops is affected by abscission or shattering, and environmental stresses often hasten or alter the abs...

  17. ABA and GA3 regulate the synthesis of primary and secondary metabolites related to alleviation from biotic and abiotic stresses in grapevine.

    PubMed

    Murcia, Germán; Fontana, Ariel; Pontin, Mariela; Baraldi, Rita; Bertazza, Gianpaolo; Piccoli, Patricia N

    2017-03-01

    Plants are able to synthesize a large number of organic compounds. Among them, primary metabolites are known to participate in plant growth and development, whereas secondary metabolites are mostly involved in defense and other facultative processes. In grapevine, one of the major fruit crops in the world, secondary metabolites, mainly polyphenols, are of great interest for the wine industry. Even though there is an extensive literature on the content and profile of those compounds in berries, scarce or no information is available regarding polyphenols in other organs. In addition, little is known about the effect of plant growth regulators (PGRs), ABA and GA3 (extensively used in table grapes) on the synthesis of primary and secondary metabolites in wine grapes. In table grapes, cultural practices include the use of GA3 sprays shortly before veraison, to increase berry and bunch size, and sugar content in fruits. Meanwhile, ABA applications to the berries on pre-veraison improve the skin coloring and sugar accumulation, anticipating the onset of veraison. Accordingly, the aim of this study was to assess and characterize primary and secondary metabolites in leaves, berries and roots of grapevine plants cv. Malbec at veraison, and changes in compositions after ABA and GA3 aerial sprayings. Metabolic profiling was conducted using GC-MS, GC-FID and HPLC-MWD. A large set of metabolites was identified: sugars, alditols, organic acids, amino acids, polyphenols (flavonoids and non-flavonoids) and terpenes (mono-, sesqui-, di- and triterpenes). The obtained results showed that ABA applications elicited synthesis of mono- and sesquiterpenes in all assessed tissues, as well as L-proline, acidic amino acids and anthocyanins in leaves. Additionally, applications with GA3 elicited synthesis of L-proline in berries, and mono- and sesquiterpenes in all the tissues. However, treatment with GA3 seemed to block polyphenol synthesis, mainly in berries. In conclusion, ABA and GA3

  18. Abscisic Acid Flux Alterations Result in Differential Abscisic Acid Signaling Responses and Impact Assimilation Efficiency in Barley under Terminal Drought Stress1[C][W][OPEN

    PubMed Central

    Seiler, Christiane; Harshavardhan, Vokkaliga T.; Reddy, Palakolanu S.; Hensel, Götz; Kumlehn, Jochen; Eschen-Lippold, Lennart; Rajesh, Kalladan; Korzun, Viktor; Wobus, Ulrich; Lee, Justin; Selvaraj, Gopalan; Sreenivasulu, Nese

    2014-01-01

    Abscisic acid (ABA) is a central player in plant responses to drought stress. How variable levels of ABA under short-term versus long-term drought stress impact assimilation and growth in crops is unclear. We addressed this through comparative analysis, using two elite breeding lines of barley (Hordeum vulgare) that show senescence or stay-green phenotype under terminal drought stress and by making use of transgenic barley lines that express Arabidopsis (Arabidopsis thaliana) 9-cis-epoxycarotenoid dioxygenase (AtNCED6) coding sequence or an RNA interference (RNAi) sequence of ABA 8′-hydroxylase under the control of a drought-inducible barley promoter. The high levels of ABA and its catabolites in the senescing breeding line under long-term stress were detrimental for assimilate productivity, whereas these levels were not perturbed in the stay-green type that performed better. In transgenic barley, drought-inducible AtNCED expression afforded temporal control in ABA levels such that the ABA levels rose sooner than in wild-type plants but also subsided, unlike as in the wild type , to near-basal levels upon prolonged stress treatment due to down-regulation of endogenous HvNCED genes. Suppressing of ABA catabolism with the RNA interference approach of ABA 8′-hydroxylase caused ABA flux during the entire period of stress. These transgenic plants performed better than the wild type under stress to maintain a favorable instantaneous water use efficiency and better assimilation. Gene expression analysis, protein structural modeling, and protein-protein interaction analyses of the members of the PYRABACTIN RESISTANCE1/PYRABACTIN RESISTANCE1-LIKE/REGULATORY COMPONENT OF ABA RECEPTORS, TYPE 2C PROTEIN PHOSPHATASE Sucrose non-fermenting1-related protein kinase2, and ABA-INSENSITIVE5/ABA-responsive element binding factor family identified specific members that could potentially impact ABA metabolism and stress adaptation in barley. PMID:24610749

  19. Violaxanthin is an abscisic acid precursor in water-stressed dark-grown bean leaves

    SciTech Connect

    Li, Yi; Walton, D.C. )

    1990-03-01

    The leaves a dark-grown bean (Phaseolus vulgaris L.) seedlings accumulate considerably lower quantities of xanthophylls and carotenes than do leaves of light-grown seedlings, but they synthesize at least comparable amounts of abscisic acid (ABA) and its metabolites when water stressed. We observed a 1:1 relationship on a molar basis between the reduction in levels of ciolaxanthin, 9{prime}-cis-neoxanthin, and 9-cis-violaxanthin and the accumulation of ABA, phaseic acid, and dihydrophaseic acid, when leaves from dark-grown plants were stressed for 7 hours. Early in the stress period, reductions in xanthophylls were greater than the accumulation of ABA and its metabolites, suggesting the accumulation of an intermediate which was subsequently converted to ABA. Leaves which were detached, but no stressed, did not accumulate ABA nor were their xanthophyll levels reduced. Leaves from plants that had been sprayed with cycloheximido did not accumulate ABA when stressed, nor were their xanthophyll levels reduced significantly. Incubation of dark-grown stressed leaves in an {sup 18}O{sub 2}-containing atmosphere resulted in the synthesis of ABA with levels of {sup 18}O in the carboxyl group that were virtually identical to those observed in light-grown leaves. The results of these experiments indicate that violaxanthin is an ABA precursor in stressed dark-grown leaves, and they are used to suggest several possible pathways from violaxanthin to ABA.

  20. Abscisic acid substantially inhibits senescence of cucumber plants (Cucumis sativus) grown under low nitrogen conditions.

    PubMed

    Oka, Mariko; Shimoda, Yousuke; Sato, Naoko; Inoue, Junya; Yamazaki, Teru; Shimomura, Norihiro; Fujiyama, Hideyasu

    2012-05-15

    Low nitrogen (N) availability such as that found in both dry land and tropical regions limits plant growth and development. The relationship between the level of abscisic acid (ABA) in a plant and its growth under low-N conditions was investigated. The level of ABA in cucumber (Cucumis sativus) plants under low-N conditions was significantly higher at 10 and 20 d after transplantation compared with that under sufficient-N conditions. Chlorophyll was preserved in the aerial parts of cucumber plants grown under low-N conditions in the presence of ABA, while there was no significant difference between control plants and ABA-applied plants under sufficient-N conditions. ABA suppressed the reduction of chlorophyll biosynthesis under low-N conditions but not under sufficient-N conditions. On the other hand, ABA decreased the expression of the chlorophyll degradation gene in older cucumber plants grown under both conditions. In addition, transcript and protein levels of a gene encoding a chlorophyll a/b binding protein were positively correlated with ABA concentration under low-N conditions. The chloroplasts in control plants were round, and the stack of thylakoid membranes was reduced compared with that of plants treated with ABA 10(-5) M. These results strongly suggest that ABA is accumulated in cucumber plants grown under low-N conditions and that accumulated ABA promotes chlorophyll biosynthesis and inhibits its degradation in those plants.

  1. Designed abscisic acid analogs as antagonists of PYL-PP2C receptor interactions.

    PubMed

    Takeuchi, Jun; Okamoto, Masanori; Akiyama, Tomonori; Muto, Takuya; Yajima, Shunsuke; Sue, Masayuki; Seo, Mitsunori; Kanno, Yuri; Kamo, Tsunashi; Endo, Akira; Nambara, Eiji; Hirai, Nobuhiro; Ohnishi, Toshiyuki; Cutler, Sean R; Todoroki, Yasushi

    2014-06-01

    The plant stress hormone abscisic acid (ABA) is critical for several abiotic stress responses. ABA signaling is normally repressed by group-A protein phosphatases 2C (PP2Cs), but stress-induced ABA binds Arabidopsis PYR/PYL/RCAR (PYL) receptors, which then bind and inhibit PP2Cs. X-ray structures of several receptor-ABA complexes revealed a tunnel above ABA's 3' ring CH that opens at the PP2C binding interface. Here, ABA analogs with sufficiently long 3' alkyl chains were predicted to traverse this tunnel and block PYL-PP2C interactions. To test this, a series of 3'-alkylsulfanyl ABAs were synthesized with different alkyl chain lengths. Physiological, biochemical and structural analyses revealed that a six-carbon alkyl substitution produced a potent ABA antagonist that was sufficiently active to block multiple stress-induced ABA responses in vivo. This study provides a new approach for the design of ABA analogs, and the results validated structure-based design for this target class.

  2. A Nuclear Factor Regulates Abscisic Acid Responses in Arabidopsis1[W][OA

    PubMed Central

    Kim, Min Jung; Shin, Ryoung; Schachtman, Daniel P.

    2009-01-01

    Abscisic acid (ABA) is a plant hormone that regulates plant growth as well as stress responses. In this study, we identified and characterized a new Arabidopsis (Arabidopsis thaliana) protein, Nuclear Protein X1 (NPX1), which was up-regulated by stress and treatment with exogenous ABA. Stomatal closure, seed germination, and primary root growth are well-known ABA responses that were less sensitive to ABA in NPX1-overexpressing plants. NPX1-overexpressing plants were more drought sensitive, and the changes in response to drought were due to the altered guard cell sensitivity to ABA in transgenic plants and not to a lack of ABA production. The nuclear localization of NPX1 correlated with changes in the expression of genes involved in ABA biosynthesis and ABA signal transduction. To understand the function of NPX1, we searched for interacting proteins and found that an ABA-inducible NAC transcription factor, TIP, interacted with NPX1. Based on the whole plant phenotypes, we hypothesized that NPX1 acts as a transcriptional repressor, and this was demonstrated in yeast, where we showed that TIP was repressed by NPX1. Our results indicate that the previously unknown protein NPX1 acts as a negative regulator in plant response to changes in environmental conditions through the control of ABA-regulated gene expression. The characterization of this factor enhances our understanding of guard cell function and the mechanisms that plants use to modulate water loss from leaves under drought conditions. PMID:19759343

  3. A central role of abscisic acid in drought stress protection of Agrobacterium-induced tumors on Arabidopsis.

    PubMed

    Efetova, Marina; Zeier, Jürgen; Riederer, Markus; Lee, Chil-Woo; Stingl, Nadja; Mueller, Martin; Hartung, Wolfram; Hedrich, Rainer; Deeken, Rosalia

    2007-11-01

    Crown gall tumors induced by Agrobacterium tumefaciens represent a sink that has to be provided with nutrients and water by the host plant. The lack of an intact epidermis or cuticle results in uncontrolled loss of water. However, neither the tumor nor the host plant displays wilting. This phenomenon points to drought adaptation in both tumors and the crown gall host plant. To understand the underlying molecular mechanisms of protection against desiccation the gene expression pattern of Arabidopsis (Arabidopsis thaliana) tumors was integrated with the profile of stress metabolites: Arabidopsis tumors accumulated high amounts of abscisic acid (ABA), the ethylene precursor aminocyclopropyl carboxylic acid, osmoprotectants, and form a suberized periderm-like protective layer. Suberization of the outer tumor cell layers most likely is mediated by ABA since external application of ABA induced suberization of Arabidopsis roots. However, the expression level of the classical marker genes, known to respond to drought stress and/or ABA, was lower in tumors. Instead another set of drought and/or ABA-inducible genes was more highly transcribed. Elevated transcription of several ABA-dependent aquaporin genes might indicate that ABA controls the water balance of the tumor. The retarded tumor growth on abi and aba mutant plants underlined the importance of a tumor-specific ABA signaling pathway. Taken together, we propose that ABA is an important signal for protection of tumors against desiccation and thus supports tumor development.

  4. Characterization and structural analysis of wild type and a non-abscission mutant at the development funiculus (Def) locus in Pisum sativum L

    PubMed Central

    Ayeh, Kwadwo Owusu; Lee, YeonKyeong; Ambrose, Mike J; Hvoslef-Eide, Anne Kathrine

    2009-01-01

    Background In pea seeds (Pisum sativum L.), the Def locus defines an abscission event where the seed separates from the funicle through the intervening hilum region at maturity. A spontaneous mutation at this locus results in the seed failing to abscise from the funicle as occurs in wild type peas. In this work, structural differences between wild type peas that developed a distinct abscission zone (AZ) between the funicle and the seed coat and non-abscission def mutant were characterized. Results A clear abscission event was observed in wild type pea seeds that were associated with a distinct double palisade layers at the junction between the seed coat and funicle. Generally, mature seeds fully developed an AZ, which was not present in young wild type seeds. The AZ was formed exactly below the counter palisade layer. In contrast, the palisade layers at the junction of the seed coat and funicle were completely absent in the def mutant pea seeds and the cells in this region were seen to be extensions of surrounding parenchymatous cells. Conclusion The Def wild type developed a distinct AZ associated with palisade layer and counterpalisade layer at the junction of the seed coat and funicle while the def mutant pea seed showed non-abscission and an absence of the double palisade layers in the same region. We conclude that the presence of the double palisade layer in the hilum of the wild type pea seeds plays an important structural role in AZ formation by delimiting the specific region between the seed coat and the funicle and may play a structural role in the AZ formation and subsequent detachment of the seed from the funicle. PMID:19549315

  5. Change Detection of Lake Aba Samuel in Ethiopia

    NASA Astrophysics Data System (ADS)

    Kaczynski, R.; Rylko, A.

    2016-06-01

    Old topographic map published in 1975 elaborated from aerial photographs taken in 1972, Landsat TM data acquired in May 1986 and Landsat ETM+ from June 2002 have been used to assess the changes of the lake Aba Samuel in Ethiopia. First map of the lake has been done in the framework of UNDP project running in 1988-90 in the Ethiopian Mapping Authority. The second classification map has been done as M.Sc. thesis in the MUT in 2015. Supervised classification methods with the use of ground truth data have been used for elaboration of the Landsat TM data. From the year 1972 up to 1986 the area of the lake has decreased by 23%. From 1986 up to 2002 the area of the lake has decreased by 20%. Therefore, after 30 years the lake was smaller by 43%. This have had very bad influence on the lives of the local population. From other recent data in the period from 2002-2015 the lake has practically disappeared and now it is only a small part of the river Akaki. ENVI 5.2 and ERDAS IMAGINE 9.2 have been used for Radiometric Calibration, Quick Atmospheric Correction (QUAC) and supervised classification of Landsat ETM+ data. The Optimum Index Factor shows the best combination of Landsat TM and ETM+ bands for color composite as 1,4,5 in the color filters: