International Journal of Molecular Sciences

Editorial

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4 pages, 208 KiB

Open AccessEditorial

Advances in the Molecular Mechanisms of Abscisic Acid and Gibberellins Functions in Plants

by Víctor Quesada

Int. J. Mol. Sci. 2021, 22(11), 6080; https://doi.org/10.3390/ijms22116080 - 4 Jun 2021

Cited by 3 | Viewed by 2665

Abstract

In this special issue entitled, “Advances in the Molecular Mechanisms of Abscisic Acid and Gibberellins Functions in Plants”, eight articles are collected, with five reviews and three original research papers, which broadly cover different topics on the abscisic acid (ABA) field [...] Read more.

In this special issue entitled, “Advances in the Molecular Mechanisms of Abscisic Acid and Gibberellins Functions in Plants”, eight articles are collected, with five reviews and three original research papers, which broadly cover different topics on the abscisic acid (ABA) field and, to a lesser extent, on gibberellins (GAs) research [...] Full article

(This article belongs to the Special Issue Advances in the Molecular Mechanisms of Abscisic Acid and Gibberellins Functions in Plants)

Research

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20 pages, 3713 KiB

Open AccessArticle

The Arabidopsis RLCK VI_A2 Kinase Controls Seedling and Plant Growth in Parallel with Gibberellin

by Ildikó Valkai, Erzsébet Kénesi, Ildikó Domonkos, Ferhan Ayaydin, Danuše Tarkowská, Miroslav Strnad, Anikó Faragó, László Bodai and Attila Fehér

Int. J. Mol. Sci. 2020, 21(19), 7266; https://doi.org/10.3390/ijms21197266 - 1 Oct 2020

Cited by 3 | Viewed by 3909

Abstract

The plant-specific receptor-like cytoplasmic kinases (RLCKs) form a large, poorly characterized family. Members of the RLCK VI_A class of dicots have a unique characteristic: their activity is regulated by Rho-of-plants (ROP) GTPases. The biological function of one of these kinases was investigated using [...] Read more.

The plant-specific receptor-like cytoplasmic kinases (RLCKs) form a large, poorly characterized family. Members of the RLCK VI_A class of dicots have a unique characteristic: their activity is regulated by Rho-of-plants (ROP) GTPases. The biological function of one of these kinases was investigated using a T-DNA insertion mutant and RNA interference. Loss of RLCK VI_A2 function resulted in restricted cell expansion and seedling growth. Although these phenotypes could be rescued by exogenous gibberellin, the mutant did not exhibit lower levels of active gibberellins nor decreased gibberellin sensitivity. Transcriptome analysis confirmed that gibberellin is not the direct target of the kinase; its absence rather affected the metabolism and signalling of other hormones such as auxin. It is hypothesized that gibberellins and the RLCK VI_A2 kinase act in parallel to regulate cell expansion and plant growth. Gene expression studies also indicated that the kinase might have an overlapping role with the transcription factor circuit (PIF4-BZR1-ARF6) controlling skotomorphogenesis-related hypocotyl/cotyledon elongation. Furthermore, the transcriptomic changes revealed that the loss of RLCK VI_A2 function alters cellular processes that are associated with cell membranes, take place at the cell periphery or in the apoplast, and are related to cellular transport and/or cell wall reorganisation. Full article

(This article belongs to the Special Issue Advances in the Molecular Mechanisms of Abscisic Acid and Gibberellins Functions in Plants)

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Full article ">Figure 1
Expression of the receptor-like cytoplasmic kinase (RLCK) VI_A2 gene in various Arabidopsis lines used in the study. (a) RT-PCR results using RLCK VI_A2 (upper row) and GAPC-2 specific (lower row) primers in wild type (1), T-DNA insertion line GABI_435H03 (2), T-DNA insertion line GABI_676D12 (3), and the GABI_435H03 line expressing the RLCK VI_A2 cDNA transgene under the control of the 35S promoter (complemented mutant) (4). (b) Site of the T-DNA insertion in the third exon of the At2G18890 gene coding for the AtRLCK VI_A2 kinase in the GABI_435H03 line. Full article ">Figure 2
The rlck vi_a2 mutation affects hypocotyl and cotyledon elongation. Hypocotyl (a,d) and cotyledon (b,e) length were measured for 5-days-old short-day (SD; 8/16h light/dark cycle) and 16-days-old dark-grown (cDark; continuous dark) seedlings. WT—wild type; MUT—T-DNA insertion mutant line; CO—complemented mutant line. Three biological replicates were made with 15–25 plants per line. Averages and standard errors are shown. Corresponding representative images are displayed on (c,f). ** p < 0.005 (Student’s t-test; comparison to WT). Full article ">Figure 3
Greenhouse-grown mutant (MUT) plants exhibited smaller plant size, as evidenced by measuring the rosette diameter. Normal size of the wild type (WT) plants was restored by expressing the kinase cDNA in the mutant background (complemented, CO line). Rosette diameters in mm are shown in (a), and representative images of the measured 4-weeks-old plants in (b). The plants were grown in short day conditions (SD). Averages and standard errors were calculated and are shown on (a). n = 15–25, ** p < 0.005 (Student’s t-test; comparison to WT). Full article ">Figure 4
The sizes of hypocotyl (a,b) and cotyledon (c,d) cells are significantly smaller in the mutant (MUT) than in the wild type (WT) plants. Fluorescent (a) and scanning electron microscopic (c) images are shown for the epidermal cells of the hypocotyl (a) and the cotyledon (c), respectively, of 5-day-old seedlings. The white bars indicate 100 μm (a), and 10 μm (b), respectively. For the quantitative comparison of cell size (b,d), 150–200 cells were measured for each of three randomly selected seedlings per line. Averages and standard errors are shown on the histograms. * p < 0.05; ** p < 0.005 (Student’s t-test; comparison to WT). Full article ">Figure 5
Exogenous gibberellin treatments complemented the mutant phenotypes. Wild type (WT) or rlck vi_a2 mutant (MUT) seedlings grown in vitro in short days (SD; 8 h/16 h light/dark) for 6 days (a) or in continuous dark (cDark) for 17 days (b,c) and plants grown at short days in greenhouse (d) were or were not treated with 20 μM gibberellic acid (GA3). Hypocotyl length (a,b), cotyledon length (c) or rosette diameter (d) were measured in 15–25 seedlings or plants, respectively, in three repetitions. Averages and standard errors are shown. ** p < 0.05 (Student’s t-test; comparison to WT). Full article ">Figure 6
Gibberellin content and gibberellin sensitivity of the mutant and the wild type. (a) Endogenous content of active gibberellins was measured in 9-days-old seedlings of wild type (WT), rlck vi_a2 mutant (MUT), and complemented mutant (CO) lines. Seedlings were grown in vitro under short day (SD; 8 h/16 h light/dark) conditions in a growth chamber. Samples were collected from three independent experiments. Averaged data are shown with the standard deviations. No statistically significant differences could be observed among the tested Arabidopsis lines (p < 0.05 Student’s t-test; comparison to WT). (b) Relative hypocotyl length was determined in response to a range of GA3 concentrations (0–100 μM), in the case of wild type and mutant seedlings (9-days-old; grown under low intensity continuous white light). Full article ">Figure 7
Overlaps of the DEGs of the rlck vi_a2 mutant with the DEGs of the ga1-3 gibberellin synthesis mutant [<a href="#B28-ijms-21-07266" class="html-bibr">28</a>,<a href="#B29-ijms-21-07266" class="html-bibr">29</a>] (a) and with those genes for which the promoters are direct targets of the cell/hypocotyl elongation regulatory transcription factors PIF4, BZR1, and/or ARF6 [<a href="#B31-ijms-21-07266" class="html-bibr">31</a>] (b). Full article ">

22 pages, 3231 KiB

Open AccessArticle

The Role of ABA in Plant Immunity is Mediated through the PYR1 Receptor

by Javier García-Andrade, Beatriz González, Miguel Gonzalez-Guzman, Pedro L. Rodriguez and Pablo Vera

Int. J. Mol. Sci. 2020, 21(16), 5852; https://doi.org/10.3390/ijms21165852 - 14 Aug 2020

Cited by 48 | Viewed by 5361

Abstract

ABA is involved in plant responses to a broad range of pathogens and exhibits complex antagonistic and synergistic relationships with salicylic acid (SA) and ethylene (ET) signaling pathways, respectively. However, the specific receptor of ABA that triggers the positive and negative responses of [...] Read more.

ABA is involved in plant responses to a broad range of pathogens and exhibits complex antagonistic and synergistic relationships with salicylic acid (SA) and ethylene (ET) signaling pathways, respectively. However, the specific receptor of ABA that triggers the positive and negative responses of ABA during immune responses remains unknown. Through a reverse genetic analysis, we identified that PYR1, a member of the family of PYR/PYL/RCAR ABA receptors, is transcriptionally upregulated and specifically perceives ABA during biotic stress, initiating downstream signaling mediated by ABA-activated SnRK2 protein kinases. This exerts a damping effect on SA-mediated signaling, required for resistance to biotrophic pathogens, and simultaneously a positive control over the resistance to necrotrophic pathogens controlled by ET. We demonstrated that PYR1-mediated signaling exerted control on a priori established hormonal cross-talk between SA and ET, thereby redirecting defense outputs. Defects in ABA/PYR1 signaling activated SA biosynthesis and sensitized plants for immune priming by poising SA-responsive genes for enhanced expression. As a trade-off effect, pyr1-mediated activation of the SA pathway blunted ET perception, which is pivotal for the activation of resistance towards fungal necrotrophs. The specific perception of ABA by PYR1 represented a regulatory node, modulating different outcomes in disease resistance. Full article

(This article belongs to the Special Issue Advances in the Molecular Mechanisms of Abscisic Acid and Gibberellins Functions in Plants)

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15 pages, 1366 KiB

Open AccessArticle

Kaolin Reduces ABA Biosynthesis through the Inhibition of Neoxanthin Synthesis in Grapevines under Water Deficit

by Tommaso Frioni, Sergio Tombesi, Paolo Sabbatini, Cecilia Squeri, Nieves Lavado Rodas, Alberto Palliotti and Stefano Poni

Int. J. Mol. Sci. 2020, 21(14), 4950; https://doi.org/10.3390/ijms21144950 - 13 Jul 2020

Cited by 23 | Viewed by 3683

Abstract

In many viticulture regions, multiple summer stresses are occurring with increased frequency and severity because of warming trends. Kaolin-based particle film technology is a technique that can mitigate the negative effects of intense and/or prolonged drought on grapevine physiology. Although a primary mechanism [...] Read more.

In many viticulture regions, multiple summer stresses are occurring with increased frequency and severity because of warming trends. Kaolin-based particle film technology is a technique that can mitigate the negative effects of intense and/or prolonged drought on grapevine physiology. Although a primary mechanism of action of kaolin is the increase of radiation reflection, some indirect effects are the protection of canopy functionality and faster stress recovery by abscisic acid (ABA) regulation. The physiological mechanism underlying the kaolin regulation of canopy functionality under water deficit is still poorly understood. In a dry-down experiment carried out on grapevines, at the peak of stress and when control vines zeroed whole-canopy net CO₂ exchange rates/leaf area (NCER/LA), kaolin-treated vines maintained positive NCER/LA (~2 µmol m⁻² s⁻¹) and canopy transpiration (E) (0.57 µmol m⁻² s⁻¹). Kaolin-coated leaves had a higher violaxanthin (Vx) + antheraxanthin (Ax) + zeaxanthin (Zx) pool and a significantly lower neoxanthin (Nx) content (VAZ) when water deficit became severe. At the peak of water shortage, leaf ABA suddenly increased by 4-fold in control vines, whereas in kaolin-coated leaves the variation of ABA content was limited. Overall, kaolin prevented the biosynthesis of ABA by avoiding the deviation of the VAZ epoxidation/de-epoxidation cycle into the ABA precursor (i.e., Nx) biosynthetic direction. The preservation of the active VAZ cycle and transpiration led to an improved dissipation of exceeding electrons, explaining the higher resilience of canopy functionality expressed by canopies sprayed by kaolin. These results point out the interaction of kaolin with the regulation of the VAZ cycle and the active mechanism of stomatal conductance regulation. Full article

(This article belongs to the Special Issue Advances in the Molecular Mechanisms of Abscisic Acid and Gibberellins Functions in Plants)

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Figure 1
(A)Trends for air (Tamb) and leaf (Tleaf) temperature; (B)midday stem water potential (ΨMD); (C) whole-canopy transpiration (E/LA) and (D) specific whole-canopy net CO2 exchange rate/leaf area (NCER/LA), according to a progressive water shortage (DOY 209–217) and subsequent re-watering (at DOY 218), in vines subjected to the kaolin treatment and in controls. Bars represents standard error (SE), n = 3. Asterisks indicate dates within which differences among treatment were significant (p < 0.05). DOY: day of the year. Full article ">Figure 2
Correlation between whole-canopy transpiration rate/leaf area (E/LA) and midday stem water potential (ΨMD). Full article ">Figure 3
(A) Trends for leaf violaxanthin (Vx) + antheraxanthin (Ax) + zeaxanthin (Zx) content, (B) de-epoxidation state, (C) neoxanthin (Nx) content and (D) abscisic acid (ABA) concentration, according to a progressive water shortage (DOY 209–217) and subsequent re-watering (at DOY 218), in vines subjected to the kaolin treatment and in controls. Bars represents standard error, n = 3. Asterisks indicate dates within which differences among treatment were significant (p < 0.05). DOY: day of the year. Full article ">Figure 4
(A) Course of leaf violaxanthin (Vx) content at dawn; (B) midday to dawn Vx differences and (C) zeaxanthin (Zx) content at midday over the experiment, according to a progressive water shortage (DOY 209–217) and subsequent re-watering (at DOY 218), in vines subjected to the kaolin treatment and in controls. Bars represents standard error, n = 3. Asterisks indicate dates within which differences among treatment were significant (p < 0.05). DOY: day of the year. Full article ">Figure 5
Correlation between whole-canopy transpiration rate/leaf area (E/LA) and leaf abscisic acid (ABA) content. Full article ">Figure 6
Correlation between leaf abscisic acid (ABA) content and leaf temperature (Tleaf). Full article ">

Review

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10 pages, 849 KiB

Open AccessReview

Interplay between Abscisic Acid and Gibberellins, as Related to Ethylene and Sugars, in Regulating Maturation of Non-Climacteric Fruit

by Fernando Alferez, Deived Uilian de Carvalho and Daniel Boakye

Int. J. Mol. Sci. 2021, 22(2), 669; https://doi.org/10.3390/ijms22020669 - 12 Jan 2021

Cited by 38 | Viewed by 5005

Abstract

In this review, we address the interaction between abscisic acid (ABA) and gibberellins (GAs) in regulating non-climacteric fruit development and maturation at the molecular level. We review the interplay of both plant growth regulators in regulating these processes in several fruit of economic [...] Read more.

In this review, we address the interaction between abscisic acid (ABA) and gibberellins (GAs) in regulating non-climacteric fruit development and maturation at the molecular level. We review the interplay of both plant growth regulators in regulating these processes in several fruit of economic importance such as grape berries, strawberry, and citrus, and show how understanding this interaction has resulted in useful agronomic management techniques. We then relate the interplay of both hormones with ethylene and other endogenous factors, such as sugar signaling. We finally review the growing knowledge related to abscisic acid, gibberellins, and the genus Citrus. We illustrate why this woody genus can be considered as an emerging model plant for understanding hormonal circuits in regulating different processes, as most of the finest work on this matter in recent years has been performed by using different Citrus species. Full article

(This article belongs to the Special Issue Advances in the Molecular Mechanisms of Abscisic Acid and Gibberellins Functions in Plants)

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14 pages, 750 KiB

Open AccessReview

Abscisic Acid and Flowering Regulation: Many Targets, Different Places

by Damiano Martignago, Beata Siemiatkowska, Alessandra Lombardi and Lucio Conti

Int. J. Mol. Sci. 2020, 21(24), 9700; https://doi.org/10.3390/ijms21249700 - 18 Dec 2020

Cited by 44 | Viewed by 6074

Abstract

Plants can react to drought stress by anticipating flowering, an adaptive strategy for plant survival in dry climates known as drought escape (DE). In Arabidopsis, the study of DE brought to surface the involvement of abscisic acid (ABA) in controlling the floral transition. [...] Read more.

Plants can react to drought stress by anticipating flowering, an adaptive strategy for plant survival in dry climates known as drought escape (DE). In Arabidopsis, the study of DE brought to surface the involvement of abscisic acid (ABA) in controlling the floral transition. A central question concerns how and in what spatial context can ABA signals affect the floral network. In the leaf, ABA signaling affects flowering genes responsible for the production of the main florigen FLOWERING LOCUS T (FT). At the shoot apex, FD and FD-like transcription factors interact with FT and FT-like proteins to regulate ABA responses. This knowledge will help separate general and specific roles of ABA signaling with potential benefits to both biology and agriculture. Full article

(This article belongs to the Special Issue Advances in the Molecular Mechanisms of Abscisic Acid and Gibberellins Functions in Plants)

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18 pages, 4112 KiB

Open AccessReview

Transcriptional Regulation of Protein Phosphatase 2C Genes to Modulate Abscisic Acid Signaling

by Choonkyun Jung, Nguyen Hoai Nguyen and Jong-Joo Cheong

Int. J. Mol. Sci. 2020, 21(24), 9517; https://doi.org/10.3390/ijms21249517 - 14 Dec 2020

Cited by 56 | Viewed by 6359

Abstract

The plant hormone abscisic acid (ABA) triggers cellular tolerance responses to osmotic stress caused by drought and salinity. ABA controls the turgor pressure of guard cells in the plant epidermis, leading to stomatal closure to minimize water loss. However, stomatal apertures open to [...] Read more.

The plant hormone abscisic acid (ABA) triggers cellular tolerance responses to osmotic stress caused by drought and salinity. ABA controls the turgor pressure of guard cells in the plant epidermis, leading to stomatal closure to minimize water loss. However, stomatal apertures open to uptake CO₂ for photosynthesis even under stress conditions. ABA modulates its signaling pathway via negative feedback regulation to maintain plant homeostasis. In the nuclei of guard cells, the clade A type 2C protein phosphatases (PP2Cs) counteract SnRK2 kinases by physical interaction, and thereby inhibit activation of the transcription factors that mediate ABA-responsive gene expression. Under osmotic stress conditions, PP2Cs bind to soluble ABA receptors to capture ABA and release active SnRK2s. Thus, PP2Cs function as a switch at the center of the ABA signaling network. ABA induces the expression of genes encoding repressors or activators of PP2C gene transcription. These regulators mediate the conversion of PP2C chromatins from a repressive to an active state for gene transcription. The stress-induced chromatin remodeling states of ABA-responsive genes could be memorized and transmitted to plant progeny; i.e., transgenerational epigenetic inheritance. This review focuses on the mechanism by which PP2C gene transcription modulates ABA signaling. Full article

(This article belongs to the Special Issue Advances in the Molecular Mechanisms of Abscisic Acid and Gibberellins Functions in Plants)

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Full article ">Figure 1
Abscisic acid (ABA) signaling pathway in the nuclei of guard cells. (A) Repression of ABA-responsive gene expression. In the absence, the clade A protein phosphatases (PP2Cs) physically interact with the sucrose non-fermenting 1-related protein kinases (SnRK2s) to reduce kinase activity via dephosphorylation. This inhibits the activity of ABRE-binding (AREB)/ABRE-binding factor (ABF) transcription factors and suppression of ABA-responsive gene transcription. (B) Activation of ABA-responsive gene expression. Under osmotic stress conditions, the interaction with ABA leads to conformational changes in the ABA receptors [PYR (pyrabactin resistance)/PYL (PYR-related)/RCAR (regulatory component of the ABA receptor)], allowing them to interact with PP2Cs. PP2Cs act as a coreceptor to capture ABA, thereby suppressing its phosphatase activity. This sequestrates PP2Cs from SnRK2s, and free SnRK2s phosphorylate the downstream transcription factors AREB/ABFs. The phosphorylated AREB/ABFs trigger the transcription of numerous ABA-responsive genes. Full article ">Figure 2
A working model of chromatin remodeling for regulation of PP2C gene transcription. (A) Repression of PP2C gene transcription. Under normal conditions, enhancer of ABA coreceptor (EAR) motif-containing MYB repressors (AtMYB44 and AtMYB20) interact with a TOPLESS-related corepressor (TPR), which recruits histone deacetylase (HDA) to suppress PP2C gene transcription. The chromatin remodeler, BRM-containing SWI/SNF complex, occupies the promoter and contributes to the repression of PP2C gene transcription. (B) Activation of PP2C gene transcription. Under osmotic stress conditions, the repressor is released from the promoter, and histone acetyltransferases (HATs) that acetylate the histones and relax DNA–histone binding in chromatin. Activator (AREB/ABFs) binds to the open promoter region, and RNA polymerase II (RNAPII) accesses and starts gene transcription. Full article ">

16 pages, 2138 KiB

Open AccessReview

Abscisic Acid Mediates Drought and Salt Stress Responses in Vitis vinifera—A Review

by Daniel Marusig and Sergio Tombesi

Int. J. Mol. Sci. 2020, 21(22), 8648; https://doi.org/10.3390/ijms21228648 - 17 Nov 2020

Cited by 50 | Viewed by 5230

Abstract

The foreseen increase in evaporative demand and reduction in rainfall occurrence are expected to stress the abiotic constrains of drought and salt concentration in soil. The intensification of abiotic stresses coupled with the progressive depletion in water pools is a major concern especially [...] Read more.

The foreseen increase in evaporative demand and reduction in rainfall occurrence are expected to stress the abiotic constrains of drought and salt concentration in soil. The intensification of abiotic stresses coupled with the progressive depletion in water pools is a major concern especially in viticulture, as most vineyards rely on water provided by rainfall. Because its economical relevance and its use as a model species for the study of abiotic stress effect on perennial plants, a significant amount of literature has focused on Vitis vinifera, assessing the physiological mechanisms occurring under stress. Despite the complexity of the stress-resistance strategy of grapevine, the ensemble of phenomena involved seems to be regulated by the key hormone abscisic acid (ABA). This review aims at summarizing our knowledge on the role of ABA in mediating mechanisms whereby grapevine copes with abiotic stresses and to highlight aspects that deserve more attention in future research. Full article

(This article belongs to the Special Issue Advances in the Molecular Mechanisms of Abscisic Acid and Gibberellins Functions in Plants)

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Figure 1
Abscisic acid biosynthesis and metabolism. In the first step, β-carotene is di-hydroxylated by β-carotene hydroxilase (BCH) proteins to produce the transisomer zeaxanthin. Hence, zeaxanthin is epoxidated by zeaxanthin oxidase (ZEP) to antheraxanthin and, then, to violaxanthin. ZEP-mediated reactions can be reversed by violaxanthin de-epoxidase (VDE). Violaxanthin can be transformed into neoxanthin by neoxanthin synthase (NSY) and both violaxanthin and neoxanthin are converted in the respective 9-cis-isomer by isomerase catalysts. The 15-carbons apocarotenoid sesquiterpenoid xanthoxin is then produced by cis-xanthophylls cleavage, whose reaction is catalyzed by 9-cis-epoxycarotenoid dioxygenase (NCED). Subsequently, xanthoxin is oxidized to abscisic aldehyde by short-chain alcohol dehydrogenase (SCAD), and finally abscisic acid (ABA) is produced by oxidation of abscisic aldehyde through the combined action of ABA-aldehyde oxidase (AAO) and a molybdenum cofactor sulfurase (MOCOSU). ABA can be inactivated by oxidation or by conjugation with monosaccharides. In the first way, ABA is oxidized (Ox) at first to phaseic acid and then to 4′-dihydrophaseic acid. In the second one, ABA is conjugated with glucose to produce ABA-β-D-glucose ester. Based on [<a href="#B9-ijms-21-08648" class="html-bibr">9</a>]. Full article ">Figure 2
Abscisic acid (ABA) signaling in guard cells. (a) ABA inducing stomatal closure. ABA binds to PYR/PYL/RCAR receptors on the guard cells membrane and triggers the accumulation in cytosol of Ca2+ by activation of Ca2+ channels (ICa). Under elevated Ca2+ concentration ([Ca2+]), the cell-efflux of Cl− is enhanced. This efflux is mediated by rapid transient (R-type) and slow-activating sustained (S-type) Cl− channels, and it causes plasma membrane depolarization. Thence, the K+ uptake is downregulated by inward-rectifying K+ channels (Ik-in) activity, while the K+ efflux is promoted through outward-rectifying K+ channels (Ik-out). The overall reduction in ions content triggers water efflux through aquaporins by osmosis, causing loss of turgor in guard cells and stomatal closure. (b) Stomatal reopening by ABA inactivation. As ABA does not bind further to PYR/PYL/RCAR receptors, Ca2+ accumulation ceases. The osmotic balance is restored by K+ uptake through Ik-in, promoting water uptake and reacquiring turgidity. Based on [<a href="#B56-ijms-21-08648" class="html-bibr">56</a>]. Full article ">Figure 3
Number of publications dealing with iso-/anisohydry from 1990 to 2019, for all plant species (white bars) and Vitis vinifera (black bars) only. Data collected from the Scopus database (<a href="https://www.scopus.com/" target="_blank">https://www.scopus.com/</a>), according to the method of [<a href="#B60-ijms-21-08648" class="html-bibr">60</a>]. Full article ">Figure 4
Modelled dynamic of stomatal conductance (gs) and foliar ABA concentration in a near-isohydric cv (Montepulciano) and an anisohydric cv (Sangiovese). Elaboration on data by [<a href="#B19-ijms-21-08648" class="html-bibr">19</a>]. Full article ">

11 pages, 883 KiB

Open AccessReview

Mediator Complex: A Pivotal Regulator of ABA Signaling Pathway and Abiotic Stress Response in Plants

by Leelyn Chong, Pengcheng Guo and Yingfang Zhu

Int. J. Mol. Sci. 2020, 21(20), 7755; https://doi.org/10.3390/ijms21207755 - 20 Oct 2020

Cited by 36 | Viewed by 5988

Abstract

As an evolutionarily conserved multi-protein complex, the Mediator complex modulates the association between transcription factors and RNA polymerase II to precisely regulate gene transcription. Although numerous studies have shown the diverse functions of Mediator complex in plant development, flowering, hormone signaling, and biotic [...] Read more.

As an evolutionarily conserved multi-protein complex, the Mediator complex modulates the association between transcription factors and RNA polymerase II to precisely regulate gene transcription. Although numerous studies have shown the diverse functions of Mediator complex in plant development, flowering, hormone signaling, and biotic stress response, its roles in the Abscisic acid (ABA) signaling pathway and abiotic stress response remain largely unclear. It has been recognized that the phytohormone, ABA, plays a predominant role in regulating plant adaption to various abiotic stresses as ABA can trigger extensive changes in the transcriptome to help the plants respond to environmental stimuli. Over the past decade, the Mediator complex has been revealed to play key roles in not only regulating the ABA signaling transduction but also in the abiotic stress responses. In this review, we will summarize current knowledge of the Mediator complex in regulating the plants’ response to ABA as well as to the abiotic stresses of cold, drought and high salinity. We will particularly emphasize the involvement of multi-functional subunits of MED25, MED18, MED16, and CDK8 in response to ABA and environmental perturbation. Additionally, we will discuss potential research directions available for further deciphering the role of Mediator complex in regulating ABA and other abiotic stress responses. Full article

(This article belongs to the Special Issue Advances in the Molecular Mechanisms of Abscisic Acid and Gibberellins Functions in Plants)

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