ABA signalling

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Genetic interactions between ABA signalling and the Arg/N-end rule pathway during Arabidopsis seedling establishment

Genetic interactions between ABA signalling and the Arg/N-end rule pathway during Arabidopsis seedling establishment

In this study, we examined further the relationship between ERFVIIs, ABA signalling and PRT6 action in Arabidopsis seedlings. ABI4 as well as ABI3 and ABI5 was found to contribute to ABA sensitivity of germination and sugar sensitivity of establishment in prt6, both of which are ERFVII dependent. Unexpectedly, we found that ABI4 transcript levels were increased in etiolated prt6 seedlings in an ERFVII-dependent manner, but ABI4 did not underpin the ERFVII-dependent delayed greening of prt6 upon exposure to light. Although the oil body phenotype of prt6 seedlings was controlled by RAP-type ERFVII transcription factors, it was not dependent on canonical ABA signalling. We propose that the N-end rule serves to control the seed to seedling transition through both ABA-dependent and independent signalling pathways.

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Continuous root xylem formation and vascular acclimation to water deficit involves endodermal ABA signalling via miR165

Continuous root xylem formation and vascular acclimation to water deficit involves endodermal ABA signalling via miR165

The plant root xylem comprises a specialized tissue for water distribution to the shoot. Despite its importance, its potential morphological plasticity in response to environmental conditions such as limited water availability has not been thoroughly studied. Here, we identify a role for the phytohormone abscisic acid (ABA) for proper xylem development and describe how ABA signalling- mediated effects on core developmental regulators are employed to alter xylem morphology under limited water availability in Arabidopsis. Plants with impaired ABA biosynthesis and reduced ABA signalling in the cell layer surrounding the vasculature displayed defects in xylem continuity, suggesting that non-cell autonomous ABA signalling is required for proper xylem development. Conversely, upon external ABA application or under limited water availability, extra xylem strands were formed. The observed xylem developmental alterations were dependent on adequate endodermal ABA signalling, which activated MIR165A. This resulted in increased miR165 levels that repress class III HD-ZIP transcription factors in the stele. We conclude that a pathway known to control core developmental features is employed as a means of modifying plant xylem morphology under conditions of environmental stress.

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Investigations of ABA Signalling Pathways in Stomatal Guard Cells

Investigations of ABA Signalling Pathways in Stomatal Guard Cells

The discovery that (-)-ABA is more effective in the stomatal system (in terms o f turgor regulation) than previously believed, may affect the hypothesis that there are two types o f ABA “receptor” depending on whether the response is classified as “fast” or “slow” (Milborrow, 1980). This model was based on the fact (-)-ABA affected plant processes such as growth (slow response) but had no effect on stomatal aperture (fast response) (Milborrow, 1980). The model may not be valid for species such as V. fab a and N. tabacum because the present study has shown that (-)-ABA does inhibit stomatal opening and in some cases was as biologically active as (+)-ABA in this system (Figure 2.4.B and C). This suggests that for the guard cells o f these species (-)- ABA can fit into the active site of the putative ABA “receptor” (associated with bringing about changes in stomatal aperture) normally occupied by (+)-ABA. This may be achieved in a similar manner to that put forward by Milborrow (1978) for the putative ABA growth “receptor” (see Section 1.7.2). The fact that (-)-ABA was needed at over a tenfold higher concentration than (+)-ABA in order to affect stomatal aperture in detached epidermis from C. communis to the same degree (Figure 2.4.A) suggests that the two receptor model idea may still hold true for this species if “slow” plant processes such as growth are equally affected by the two enantiomers. Further work is needed to confirm this. However, the biological activity o f (-)-ABA reported in the present study does suggest that there may not be such a sharp distinction between the receptors for the “fast” and “slow” responses to ABA (see Section 1.5) in C. communis as Milborrow’s (1980) general model proposed.

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Transcription factor interactions at the promoter of the Arabidopsis circadian clock gene LHY

Transcription factor interactions at the promoter of the Arabidopsis circadian clock gene LHY

As described in the section above, TOC1 was found through the modified-Y1H assay to enable binding of ABI5 to the -957/-754 region of the LHY promoter, and to inhibit the binding of ABF3 to this promoter region. TOC1 is also known to directly interact with ABI3 protein in yeast (Kurup et al., 2000). These interactions suggested that TOC1 has a role in regulating the action of ABA signalling factors at the LHY promoter. Alternatively, ABA-responsive transcription factors may modulate binding of TOC1 to the LHY promoter. It is therefore reasonable to speculate that TOC1’s presence at the promoter may be regulated or modified by ABA signalling. Therefore, in order to determine whether the normal presence of TOC1 at the LHY promoter (as established by the TMG ChIP in Chapter 4) could be altered by exposure to ABA, and whether this might translate into a measurable effect on LHY expression, an anti-GFP TOC1 ChIP was performed on TMG plants treated with ABA. Simultaneously, the effect of ABA exposure on LHY expression was investigated in these same plants by extracting LHY RNA before and for several hours after ABA treatment.

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Modelling dynamics of Abscisic Acid (ABA) signalling network in plant guard cells to induce stomatal closure in response to drought stress

Modelling dynamics of Abscisic Acid (ABA) signalling network in plant guard cells to induce stomatal closure in response to drought stress

The production of the phytohormone abscisic acid (ABA), which is triggered in guard cells by drought causes rapid stomatal closure and induces the expression of stress-related genes to further activate long term drought responses. ABA levels in plants fluctuate widely in response to environmental changes, especially drought and salt stresses, activating a complex web of signalling components through a family of ABA receptors that alter ion homeostasis and the structure of guard cells. ABA induced stomatal closing is mediated by a reduction in the turgor pressure of guard cells, which predominantly requires an efflux of potassium and chloride ions and removal and/or metabolism of organic acid malate to osmotically inactive starch. ABA recognition by its receptor activates the protein kinase SnRK2 through inactivation of a central negative regulator, type 2C protein phosphatases (PP2Cs), facilitating the downstream targets of the network to regulate the ion channel activities to close the stomata through reduction of guard cell turgor (stiffness). This turgor reduction is facilitated by various types of plant lipids, protein kinases, protein phosphatases, ion channel proteins, reactive molecules such as ROS (reactive oxygen species), cytosolic pH, cytosolic calcium and several other molecules causing guard cells to shrink. Guard cell shrinkage accompanied by turgor reduction is further supported by structural rearrangements that facilitate the cell to acquire the required shape for stomatal closure. Changes in structural rearrangements are also a result of various actin binding proteins that disassemble the radially arranged actin filaments in the open stomata into a random orientation. The ABA signalling network coordinates both osmoregulation and structural rearrangements in parallel in a way that ultimately leads to stomatal closure.

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Defective ABA-mediated sugar signalling pathway in an established Arabidopsis thaliana cell suspension culture explains its stay-green phenotype at high sugar concentrations

Defective ABA-mediated sugar signalling pathway in an established Arabidopsis thaliana cell suspension culture explains its stay-green phenotype at high sugar concentrations

abi5 were insensitive to 7% w/v glucose (Arenas-Huertero et al., 2000). The abi3 mutants differed slightly in their response to sugar, as they were only insensitive to glucose at high ABA concentrations (1 μM) (Nambara et al., 2002). The abi8 mutants also had a green sugar insensitive phenotype at 6% w/v glucose, as well as severely stunted growth in low glucose media (Brocard-Gifford et al., 2004). Overexpression of bZIP transcription factors ABF2 and ABI5 caused hypersensitivity to sugar (Brocard et al., 2002; Kang et al., 2010). The armadillo (arm) repeat protein encoded by ARIA is a positive regulator of the ABA responsive transcription factor ABF2.The aria mutant had a sugar insensitive phenotype at 5% w/v glucose (Kim et al., 2004a). Knockout of other ABA effectors, abi1-1, and abi2-1 did not cause glucose insensitivity, suggesting that there is a distinct ABA signalling pathway for sugars (Arenas-Huertero et al., 2000). In addition to the PYL/RCAR ABA receptors, there is also a secondary ABA signalling pathway in Arabidopsis that is mediated by the chloroplast-localized ABA receptor ABAR (Fig. 1.12) (Leon et al., 2013). In response to ABA, ABAR recruits WRKY transcription factors from the nucleus to the cytoplasm (Rushton et al., 2012; Shen et al., 2006). WRK18, WRK40 and WRKY60 repress the transcription of ABI3, ABI4, ABF4 and other transcription factors in the nucleus (Fig. 1.12), and this repression is alleviated when WRKY transcription factors are recruited to the cytoplasm, in response to ABA (Rushton et al., 2012).

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Common transcriptional regulation of ABA and ethylene

Common transcriptional regulation of ABA and ethylene

A class 1 HD-Zip TF of tomato, LeHB1, which plays an important role in loral organogenesis and ripening, can transcriptionally activate the expression of tomato LeACO1, a biosynthetic gene of ethylene [24]. LeHB1 binds to LeACO1 promoter sequence with dyad symmetry. Down-regulating LeHB1 via virus-induced gene silencing signi icantly reduced LeACO1 expression, suggesting LeHB1 transcriptionally activate LeACO1 and thus promote ethylene responses [24]. Any ABA interference in LeHB1 overexpressing lines is unknown, however, a Medicago truncatula HD-Zip, MtHB1, acts as a positive regulator of ABA signalling in lateral root emergence [26]. When MtHB1 was overexpressed in the roots, it suppressed LOB-binding domain 1 (LBD1) resulting in longer primary root while reduced lateral root (LR) emergence, which involved MtHB1 repression of auxin-induced ABI3, a ABA-responsive TF, that is important for LR primordia [27] suggesting ABA sensitivity can override auxin response mediated by MtHB1. Interestingly, when ectopically overexpressed, AtHB1 overrides the etiolation response of dark-grown Arabidopsis seedlings [28]. Considering the fact that AtHB1 shares 69% and its HD-Zip domains share 92% similarity to LeHB1 [24] and the triple response is typical to ethylene [29], it is possible that HB1 can act as a positive regulator of ABA response and a negative regulator of ethylene signalling. However, this needs to be experimentally tested.

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An In Silico Comparative and Pathway Analysis of Targeted Genes of Diabetic Retinopathy: A Prognostic Approach towards Diabetic Retinopathy

An In Silico Comparative and Pathway Analysis of Targeted Genes of Diabetic Retinopathy: A Prognostic Approach towards Diabetic Retinopathy

miRNA – target pathway interactions were performed for miRNA 21 and their targeted gene IL1B by using mirwalk database, their interaction was found in apoptosis and MAPK signalling pathway which are previously link with DR. furthermore for the identification of their link with diabetic retinopathy KEGG disease pathway analysis was performed.Which shows MAPK signalling and apoptosis both pathways are affected in case of diabetic retinopathy. 8. A comparative miRNA target prediction

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Increase of DNA Methylation at the HvCKX2.1 Promoter by Terminal Drought Stress in Barley

Increase of DNA Methylation at the HvCKX2.1 Promoter by Terminal Drought Stress in Barley

detailed analysis. The identified 24mer has homology to the promoter region of HvCKX2.1. As the barley genome sequence is not completely known and the gaps are particularly spanning repetitive elements, the origin of the 24mer could not be identified. The identified region of the promoter contained several features of heterochromatic DNA, namely LTR fragments and loci of viral origin. Using the MSRE qPCR, we could detect substantial methylation in the upstream region of the HvCKX2.1 promoter. In the region homologous to the 24mers, a drought stress specific increase of methylation was detected. This indicates a spreading of methylation towards the regulatory promoter region of the gene. This drought stress specific increase of DNA methylation correlates with reduced HvCKX2.1 expression at early germination and an increase of its substrate in germinating seedlings derived from plants grown under terminal drought stress conditions. The expression of HvCKX2.1 might be affected by the amount of methylation in its promoter region. Thus, HvCKX2.1 represents a natural target gene influenced by promoter DNA methylation regulated by the RdDM pathway. Although the drought stress is applied to the mother plant, and the physiological state is mediated as ABA response of the mother plant, the detectable effect can be sensed in the offspring. Therefore, it is tempting to call this effect transgenerational, although the developing grain was already present at the time of stress condition. Whether the increase in CK is the major signal leading to faster germination, or the faster ABA degradation is the main trigger, remains to be resolved. Interestingly, RNAi mediated silencing of HvCKX2 [34] resulted in one transgenic line with a defect in germination that was not further investigated.

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Effects of abscisic acid and brassinolide on photosynthetic characteristics of Leymus chinensis from Songnen Plain grassland in Northeast China

Effects of abscisic acid and brassinolide on photosynthetic characteristics of Leymus chinensis from Songnen Plain grassland in Northeast China

Background: It has been well demonstrated that plant growth regulators have important functions in multiple physiological processes. ABA and BR play crucial roles in response of crops to stresses. Photosynthetic capacity of Leymus. chinensis treated by various concentrations of ABA and BR in combination was determined. Further more, the mechanisms of ABA and BR treatments and potential for recovery of saline-alkali grasslands were discussed. Results: Abscisic acid (ABA) and brassinolide (BR) affected leaf gas exchange, growth and biomass of L. chinensis. The application of ABA and BR mixtures, especially that of 0.01 mM ABA and 2 × 10 -4 mM BR, increased the net photosynthetic rate, stomatal conductance, water use efficiency, the maximum net photosynthetic rate, light- saturated rate, leaf respiration rate, the maximum RUBP carboxylation rate, the maximum electron transport rate, the maximum triose-phosphate utilization, carboxylation efficiency and the quantum efficiency of PSII and subsequently enhanced density, height and biomass in L. chinensis. We also observed reduction in the light compensation and saturation points following the application of ABA and BR treatments.

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Transcriptome profiling identifies ABA mediated regulatory changes towards storage filling in developing seeds of castor bean (Ricinus communis L.)

Transcriptome profiling identifies ABA mediated regulatory changes towards storage filling in developing seeds of castor bean (Ricinus communis L.)

Seeds of castor bean var. ZB306 (kindly provided by Zibo Academy of Agricultural Sciences, Shandong, China) were germinated in Xishuangbanna Tropical Botanical Garden (21°560 N, 101°150 E, 600 m asl) under natural conditions. Mature female flowers were hand pollinated and tagged as 0 days after pollination (DAP). Developing seeds with capsulate at ca. 21 DAP were collected from the field. Young seeds were separated from capsulates and were stored at room temperature (18-25°C) for several hours. Decapsulated seeds were inoculated in MS media (Murashige and Skoog) supplemented with exogenous ABA (Sigma, China), as described previously [24], at 1, 10, 50 and 100 μM concentrations to sort out the optimal ABA concentration for further test. Same treatments without ABA in MS media were used as control. Once the optimal ABA concentration was determined, two decap- sulated seeds from the same capsulate were considered as a pair for in vitro seed culture, one was cultured with ABA in MS media, and other as control (without ABA). At least five individual experiments were replicated. Tested seeds were dried overnight in Eppendorf tubes under vacuum centrifugation. The dried seeds were weighted (DW, dry weight). The contents of storage ma- terials including total lipids, proteins and total sugars were measured for each cultured seed after 96 h incuba- tion in dark at 25-28°C as well as in developing seeds. For the preparation of RNA samples, three seeds cul- tured with ABA for 24 h and the other three seeds from same capsulate cultured without ABA were collected as tissues for extracting RNA.

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Joining technologies for a temperature-stable integration of a LTCC-based pressure sensor

Joining technologies for a temperature-stable integration of a LTCC-based pressure sensor

which may also be a reason for the stronger phase forma- tion. This reaction captures at least a fraction of the active- phase titanium from the brazing alloy which is necessary to enable a wetting process on ceramic surfaces. Thus due to insufficient brazing results no further experiments were per- formed with this brazing alloy containing a high percentage of indium. The presented results showed that brazing of Ko- var with indium-containing active braze filler metals leads to considerable destruction of the Kovar microstructure. An op- timization of the brazing cycle could help to minimize this behaviour. However this was beyond the scope of the present study and will be addressed in the future. As explained in the next section, the indium-free Cusil-ABA braze filler metal leaves the microstructure of the Kovar nearly intact.

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PLANT U-BOX PROTEIN 10 negatively regulates abscisic acid response in Arabidopsis

PLANT U-BOX PROTEIN 10 negatively regulates abscisic acid response in Arabidopsis

MYC2 is well known as a positive regulator for abscisic acid (ABA) signaling but whether PLANT U‑BOX PROTEIN 10 (PUB10) is involved in ABA responses has not been reported. Here, we show that the E3 ubiquitin ligase PUB10 modu‑ lates ABA signaling in Arabidopsis. PUB10ox (35S:PUB10‑myc) and myc2 loss‑of‑function mutants were hyposensitive to ABA during germination, whereas pub10 loss‑of‑function and MYC2ox (35S:MYC2‑GFP) mutants were hypersensitive. In addition, pub10 mutants showed hypersensitivity to high salt and osmotic stress during germination; by contrast, PUB10ox line displayed the opposite phenotype. ABA‑induced expression of KIN2 (Cold‑ and ABA‑Inducible Protein), RD22 (Responsive to Dehydration 22), ANAC019 (NAC Domain‑Containing Protein 19), and ANAC055 (NAC Domain‑ Containing Protein 55) was enhanced in both pub10 and MYC2ox plants. Taken together, pub10 plants phenocopied MYC2ox plants, whereas PUB10ox plants phenocopied myc2 in ABA response. Our results provide evidence that PUB10 negatively regulates ABA signaling in Arabidopsis.

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The Features Of Urban Storm Drainage In Aba, Nigeria

The Features Of Urban Storm Drainage In Aba, Nigeria

materials resulting to urban flooding (Owuama et al., 2014). Urban drainage in Aba is essentially roadway drainage, with sealed or open concrete drains on both sides of the major roads. The city does not have urban drainage master plan, and there has never been a specific integrated urban drainage project. Aba has a relatively flat coastal terrain, with the average relief of about 54m above sea level (Njoku, Amangabara, and Duru, 2013). The city also has higher mean volumes of precipitation, and great number of rainy days leading to more complex management of storm drainage, since greater volumes of runoff must be routed somewhere. The mean transported load of solids is larger (because runoffs go on for a longer time); there is less time for urban cleaning (more sediment and refuse remain on the streets) and to maintain drainage structures; and more time to develop waterborne diseases like malaria and typhoid. Urban drainage in Aba is equally adversely impacted by uncontrolled urban spread and its clandestine concentration, increased rates of soil imperviousness, and encroachment on floodplains and natural water courses (Njoku et al., 2013). On the other hand, urban slums with very dense land occupancy practically eliminate empty spaces which could become part of a storm drainage system in the city.

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Gender & Sexuality in the ABA Standards on the Treatment of Prisoners

Gender & Sexuality in the ABA Standards on the Treatment of Prisoners

Part I describes the road to revision of the ABA standards on prisons and prisoners. Part II deals with the provisions of the 2010 Standards that are particularly relevant to women prisoners, including provisions on screening and classification, pregnant prisoners and new mothers, and co-corrections and equal protection. Part III discusses specific standards that are an outgrowth of the movement to address prison sexual violence, including those dealing with custodial sexual abuse and protection of vulnerable prisoners, as well as cross-gender supervision and privacy. Part III also describes standards affecting lesbian and gay prisoners, and transgender prisoners, reflecting heightened awareness of the special needs of these groups. The Article concludes with a comment on the role of the Bar in establishing correctional policy and practice.

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Salt acclimation induced salt tolerance in wild-type and abscisic acid-deficient mutant barley

Salt acclimation induced salt tolerance in wild-type and abscisic acid-deficient mutant barley

As expected, the ABA concentration in leaf was significantly increased by salt stress and the combina- tion of salt acclimation and salt stress in WT, while it was not affected by both treatments in ABA-deficient mutant Az34 (Figure 1). The remarkable increases in endogenous ABA concentration have been found in various plant species when exposed to salt stress (Jakab et al. 2005). ABA has been demonstrated to function as crucial cellular signaling of salt acclima- tion, probably regulating carbohydrate metabolism (Garcia de la Garma et al. 2015).

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A Bayesian Belief Updating Model of Phonetic Recalibration and Selective Adaptation

A Bayesian Belief Updating Model of Phonetic Recalibration and Selective Adaptation

The acoustic stimuli used in exposure and test were drawn from a nine-item continuum (denoted x = 1, . . . , 9) from /aba/ to /ada/, formed by ma- nipulating the second formant frequency before and after the stop consonant (Vroomen et al., 2004). The most /aba/-like item x = 1 was synthesized us- ing the formant values from a normal /aba/ pro- duction, and the most /ada/-like item x = 9 was derived from an /ada/ production. The maximally ambiguous item was determined for each subject via a labeling function (percent-/aba/ classification for each token) derived from pre-test classification data (98 trials from across the entire continuum). All subjects’ maximally ambiguous tokens were one of x = 4, 5 or 6.

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Long distance ABA transport can mediate distal tissue responses by affecting local ABA concentrations

Long distance ABA transport can mediate distal tissue responses by affecting local ABA concentrations

completely expanded leaf from the shoot apex was frozen in liquid nitrogen and stored at -20°C. The shoot was then severed at the stem base (below the graft union), the cut surface rinsed 2–3 times with distilled water to remove any contaminating cell debris, and then blotted dry with filter paper. Root water potential was investigated using a pressure chamber, and was determined to be the pressure at which there was no spontaneous sap exudation from the cut surface. Root xylem sap was collected into pre-weighed Eppendorf tubes. Sufficient overpressure was applied to ensure the xylem sap flow rate closely matched the whole plant transpiration rate. The collected root xylem sap was immediately stored at -20°C for ABA analysis. Roots were quickly (<1 minute) and carefully removed from the pot and washed, and 1 g fresh root tissue was frozen using liquid nitrogen and stored at -20°C.

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Elevated CO2 Induced Responses in Stomata Require ABA and ABA Signaling

Elevated CO2-Induced Responses in Stomata Require ABA and ABA Signaling.

closure in NADPH respiratory burst oxidase mutants. Previous work has revealed that these enzymes play roles in guard cell ABA signaling, the rbohD rbohF double mutant being compro- mised in guard cell ABA signaling [35]. The results of our experi- ments (Figure 1C) show that while there was a statistically signif- icant reduction in stomatal aperture elicited by elevated [CO 2 ] in

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Elevated CO2 Induced Responses in Stomata Require ABA and ABA Signaling

Elevated CO2 Induced Responses in Stomata Require ABA and ABA Signaling

contrast to wild-type, which showed a 14% increase in fluores- cence, there was no evidence for increased ROS production in either the triple or quadruple ABA receptor mutants (Figure 2B). Taken together, these results suggest that there is a requirement for at least one or more of the PYR1, PYL1, PYL2, and PYL4 gene products in the [CO 2 ]-stimulated increase in ROS that occurs

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