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1.
Nat Commun ; 13(1): 2511, 2022 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-35523967

RESUMO

Stomata play a critical role in the regulation of gas exchange and photosynthesis in plants. Stomatal closure participates in multiple stress responses, and is regulated by a complex network including abscisic acid (ABA) signaling and ion-flux-induced turgor changes. The slow-type anion channel SLAC1 has been identified to be a central controller of stomatal closure and phosphoactivated by several kinases. Here, we report the structure of SLAC1 in Arabidopsis thaliana (AtSLAC1) in an inactivated, closed state. The cytosolic amino (N)-terminus and carboxyl (C)-terminus of AtSLAC1 are partially resolved and form a plug-like structure which packs against the transmembrane domain (TMD). Breaking the interactions between the cytosolic plug and transmembrane domain triggers channel activation. An inhibition-release model is proposed for SLAC1 activation by phosphorylation that the cytosolic plug dissociates from the transmembrane domain upon phosphorylation, and induces conformational changes to open the pore. These findings facilitate our understanding of the regulation of SLAC1 activity and stomatal aperture in plants.


Assuntos
Proteínas de Arabidopsis , Arabidopsis , Ácido Abscísico/farmacologia , Ânions , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Proteínas de Membrana/metabolismo , Fosforilação , Estômatos de Plantas/metabolismo
2.
J Agric Food Chem ; 70(14): 4267-4278, 2022 Apr 13.
Artigo em Inglês | MEDLINE | ID: mdl-35362318

RESUMO

Seven Arabidopsis thaliana mutants with differences in cuticle thickness and stomatal density were foliar exposed to 50 mg L-1 Cu3(PO4)2 nanosheets (NS), CuO NS, CuO nanoparticles, and CuSO4. Three separate fractions of Cu (surface-attached, cuticle, interior leaf) were isolated from the leaf at 0.25, 2, 4, and 8 h. Cu transfer from the surface through the cuticle and into the leaf varied with mutant and particle type. The Cu content on the surface decreased significantly over 8 h but increased in the cuticle. Cu derived from the ionic form had the greatest cuticle concentration, suggesting greater difficulty in moving across this barrier and into the leaf. Leaf Cu in the increased-stomatal mutants was 8.5-44.9% greater than the decreased stomatal mutants, and abscisic acid to close the stomata decreased Cu in the leaf. This demonstrates the importance of nanomaterial entry through the stomata and enables the optimization of materials for nanoenabled agriculture.


Assuntos
Proteínas de Arabidopsis , Arabidopsis , Nanopartículas , Ácido Abscísico , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Nanopartículas/química , Folhas de Planta/genética , Estômatos de Plantas
3.
Cells ; 11(7)2022 Mar 29.
Artigo em Inglês | MEDLINE | ID: mdl-35406719

RESUMO

Plants deploy molecular, physiological, and anatomical adaptations to cope with long-term water-deficit exposure, and some of these processes are controlled by circadian clocks. Circadian clocks are endogenous timekeepers that autonomously modulate biological systems over the course of the day-night cycle. Plants' responses to water deficiency vary with the time of the day. Opening and closing of stomata, which control water loss from plants, have diurnal responses based on the humidity level in the rhizosphere and the air surrounding the leaves. Abscisic acid (ABA), the main phytohormone modulating the stomatal response to water availability, is regulated by circadian clocks. The molecular mechanism of the plant's circadian clock for regulating stress responses is composed not only of transcriptional but also posttranscriptional regulatory networks. Despite the importance of regulatory impact of circadian clock systems on ABA production and signaling, which is reflected in stomatal responses and as a consequence influences the drought tolerance response of the plants, the interrelationship between circadian clock, ABA homeostasis, and signaling and water-deficit responses has to date not been clearly described. In this review, we hypothesized that the circadian clock through ABA directs plants to modulate their responses and feedback mechanisms to ensure survival and to enhance their fitness under drought conditions. Different regulatory pathways and challenges in circadian-based rhythms and the possible adaptive advantage through them are also discussed.


Assuntos
Ácido Abscísico , Relógios Circadianos , Ácido Abscísico/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Estômatos de Plantas/fisiologia , Plantas/metabolismo , Água/metabolismo
4.
Glob Chang Biol ; 28(11): 3484-3485, 2022 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-35366341

RESUMO

The main responsibility of stomata is controlling the exchange of water and carbon dioxide between plants and the surrounding air. Stomata open or close accordingly to environmental conditions. For example, stomata are closed in the dark but gradually open as light levels increase. New aspects of stomata functioning are still surfacing enabling a better representation of the relationship between vegetation and the atmosphere, which is of great importance for global change research. photo credit: João M. Rosa/Nitro Imagens/AmazonFACE. This article is a Commentary on Lamour et al., https://doi.org/10.1111/gcb.16103.


Assuntos
Dióxido de Carbono , Estômatos de Plantas , Atmosfera , Folhas de Planta , Plantas , Água
5.
Methods Mol Biol ; 2494: 217-227, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35467210

RESUMO

Plants live in highly dynamic surroundings and need to cope with constant environmental challenges. In order to do so, they developed quick reactions to stress that allow them to gain time while mounting a major response. This first line of defense includes the stomata, leaf epidermal pores in charge of regulating water loss and photosynthesis. Stomatal movements are controlled by the stress phytohormone abscisic acid (ABA), which induces fast closure of the stomata upon perception of stress conditions. By modulating plasma membrane ion channels, ABA leads to loss of water from the guard cells surrounding the stomatal pore and a consequent reduction of its aperture. Here, we provide a microscopy-based method to assess the plant's response to ABA through measurements of the stomatal aperture. This protocol describes a simple, quick, and unexpensive method to prepare high-quality impressions of leaves from Arabidopsis thaliana seedlings from long-lasting silicone-based casts, allowing detailed imaging and accurate determination of the aperture of stomatal pores.


Assuntos
Ácido Abscísico , Arabidopsis , Ácido Abscísico/metabolismo , Arabidopsis/metabolismo , Folhas de Planta/metabolismo , Estômatos de Plantas/metabolismo , Água/metabolismo
6.
Cell Host Microbe ; 30(4): 489-501.e4, 2022 04 13.
Artigo em Inglês | MEDLINE | ID: mdl-35247330

RESUMO

High atmospheric humidity levels profoundly impact host-pathogen interactions in plants by enabling the establishment of an aqueous living space that benefits pathogens. The effectors HopM1 and AvrE1 of the bacterial pathogen Pseudomonas syringae have been shown to induce an aqueous apoplast under such conditions. However, the mechanisms by which this happens remain unknown. Here, we show that HopM1 and AvrE1 work redundantly to establish an aqueous living space by inducing a major reprogramming of the Arabidopsis thaliana transcriptome landscape. These effectors induce a strong abscisic acid (ABA) signature, which promotes stomatal closure, resulting in reduced leaf transpiration and water-soaking lesions. Furthermore, these effectors preferentially increase ABA accumulation in guard cells, which control stomatal aperture. Notably, a guard-cell-specific ABA transporter, ABCG40, is necessary for HopM1 induction of water-soaking lesions. This study provides molecular insights into a chain of events of stomatal manipulation that create an ideal microenvironment to facilitate infection.


Assuntos
Proteínas de Arabidopsis , Arabidopsis , Ácido Abscísico/farmacologia , Arabidopsis/microbiologia , Proteínas de Arabidopsis/genética , Estômatos de Plantas/microbiologia , Pseudomonas syringae , Água
7.
Genes (Basel) ; 13(3)2022 03 16.
Artigo em Inglês | MEDLINE | ID: mdl-35328077

RESUMO

Calcium acts as a universal secondary messenger that transfers developmental cues and stress signals for gene expression and adaptive growth. A prior study showed that abiotic stresses induce mutually independent cytosolic Ca2+ ([Ca2+]cyt) and nucleosolic Ca2+ ([Ca2+]nuc) increases in Arabidopsis thaliana root cells. However, gene expression networks deciphering [Ca2+]cyt and [Ca2+]nuc signalling pathways remain elusive. Here, using transgenic A. thaliana to selectively impair abscisic acid (ABA)- or methyl jasmonate (MeJA)-induced [Ca2+]cyt and [Ca2+]nuc increases, we identified [Ca2+]cyt- and [Ca2+]nuc-regulated ABA- or MeJA-responsive genes with a genome oligo-array. Gene co-expression network analysis revealed four Ca2+ signal-decoding genes, CAM1, CIPK8, GAD1, and CPN20, as hub genes co-expressed with Ca2+-regulated hormone-responsive genes and hormone signalling genes. Luciferase complementation imaging assays showed interactions among CAM1, CIPK8, and GAD1; they also showed interactions with several proteins encoded by Ca2+-regulated hormone-responsive genes. Furthermore, CAM1 and CIPK8 were required for MeJA-induced stomatal closure; they were associated with ABA-inhibited seed germination. Quantitative reverse transcription polymerase chain reaction analysis showed the unique expression pattern of [Ca2+]-regulated hormone-responsive genes in cam1, cipk8, and gad1. This comprehensive understanding of distinct Ca2+ and hormonal signalling will allow the application of approaches to uncover novel molecular foundations for responses to developmental and stress signals in plants.


Assuntos
Ácido Abscísico , Arabidopsis , Ácido Abscísico/metabolismo , Ácido Abscísico/farmacologia , Acetatos , Arabidopsis/metabolismo , Cálcio/metabolismo , Ciclopentanos , Hormônios , Oxilipinas , Estômatos de Plantas/genética , Estômatos de Plantas/metabolismo
9.
Physiol Plant ; 174(2): e13665, 2022 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-35279848

RESUMO

Plants are inevitably exposed to drought stress limiting their growth and causing yield loss, thus inciting food crises across the world. Nanoparticles (NPs) are regarded as effective and promising tools for modulation of crop yield to overcome current and future constraints in sustainable agricultural production by upgrading the plant tolerance mechanism under abiotic stress conditions, including drought. NPs exhibit alleviating effects against drought stress via induction of physiological and biochemical readjustments accompanied by modulation of gene expression involved in drought response/tolerance. NPs ameliorate drought-induced reduction in carbon assimilation via increasing the photosynthetic activity. The improved root growth, upregulation of aquaporins, modification of intracellular water metabolism, accumulation of compatible solutes and ion homeostasis are the major mechanisms used by NPs to mitigate the osmotic stress caused by water deficit. NPs reduce water loss from leaves through stomatal closure due to fostered abscisic acid (ABA) accumulation and ameliorate oxidative stress damage by reducing reactive oxygen species and activating the antioxidant defense system. This review provides an evolutionary foundation regarding drought stress in plant life and summarizes the interactions between NPs and plants under drought. The subsequent impact of NPs on plant development and productivity and recent nanobiotechnological approaches to improve drought stress resilience are presented. On the whole, this review highlights the significance of NPs in dealing with the global problem of water scarcity faced by farmers.


Assuntos
Secas , Nanopartículas , Regulação da Expressão Gênica de Plantas , Estômatos de Plantas/fisiologia , Plantas/genética , Plantas/metabolismo , Estresse Fisiológico/genética , Água/metabolismo
12.
Plant Cell Environ ; 45(4): 1146-1156, 2022 04.
Artigo em Inglês | MEDLINE | ID: mdl-35112729

RESUMO

Increasing stomatal movement is beneficial to improve plant water use efficiency and drought resilience. Contradictory results indicate that aquaporins might regulate stomatal movement. Here, we tested whether the maize plasma membrane PIP2;5 aquaporin affects stomatal closure under water deficit, abscisic acid (ABA) or vapour pressure deficit (VPD) treatment in intact plants, detached leaves or peeled epidermis. Transpiration, stomatal conductance (gs ) and aperture and reactive oxygen species (ROS) in stomatal complexes were studied in maize lines with increased or knocked down (KD) PIP2;5 gene expression. In well-watered conditions, the PIP2;5 overexpressing (OE) plants transpired more than wild types (WTs), while no significant difference in transpiration was observed between pip2;5 KD and WT. Upon mild water deficit or low ABA concentration treatments, transpiration and gs decreased more in PIP2;5 OE lines and less in pip2;5 KD lines, in comparison with WTs. In the detached epidermis, ABA treatment induced faster stomatal closing in PIP2;5 OE lines compared to WTs, while pip2;5 KD stomata were ABA insensitive. These phenotypes were associated with guard cell ROS accumulation. Additionally, PIP2;5 is involved in the transpiration decrease observed under high VPD. These data indicate that maize PIP2;5 is a key actor increasing the sensitivity of stomatal closure to water deficit.


Assuntos
Aquaporinas , Estômatos de Plantas , Ácido Abscísico/metabolismo , Ácido Abscísico/farmacologia , Aquaporinas/genética , Aquaporinas/metabolismo , Membrana Celular/metabolismo , Estômatos de Plantas/fisiologia , Transpiração Vegetal/fisiologia , Espécies Reativas de Oxigênio/metabolismo , Água/metabolismo , Zea mays/genética , Zea mays/metabolismo
13.
Plant Physiol ; 188(4): 2085-2100, 2022 03 28.
Artigo em Inglês | MEDLINE | ID: mdl-35134219

RESUMO

Stomatal movement is essential for plants to optimize transpiration and therefore photosynthesis. Rapid changes in the stomatal aperture are accompanied by adjustment of vacuole volume and morphology in guard cells (GCs). In Arabidopsis (Arabidopsis thaliana) leaf epidermis, stomatal development undergoes a cell-fate transition including four stomatal lineage cells: meristemoid, guard mother cell, young GC, and GC. Little is known about the mechanism underlying vacuole dynamics and vacuole formation during stomatal development. Here, we utilized whole-cell electron tomography (ET) analysis to elucidate vacuole morphology, formation, and development in different stages of stomatal lineage cells at nanometer resolution. The whole-cell ET models demonstrated that large vacuoles were generated from small vacuole stepwise fusion/maturation along stomatal development stages. Further ET analyses verified the existence of swollen intraluminal vesicles inside distinct vacuoles at certain developmental stages of stomatal lineage cells, implying a role of multivesicular body fusion in stomatal vacuole formation. Collectively, our findings demonstrate a mechanism mediating vacuole formation in Arabidopsis stomatal development and may shed light on the role of vacuoles in stomatal movement.


Assuntos
Proteínas de Arabidopsis , Arabidopsis , Proteínas de Arabidopsis/genética , Tomografia com Microscopia Eletrônica , Estômatos de Plantas , Vacúolos
14.
Dev Cell ; 57(5): 569-582.e6, 2022 03 14.
Artigo em Inglês | MEDLINE | ID: mdl-35148836

RESUMO

Differentiation of specialized cell types requires precise cell-cycle control. Plant stomata are generated through asymmetric divisions of a stem-cell-like precursor followed by a single symmetric division that creates paired guard cells surrounding a pore. The stomatal-lineage-specific transcription factor MUTE terminates the asymmetric divisions and commits to differentiation. However, the role of cell-cycle machineries in this transition remains unknown. We discover that the symmetric division is slower than the asymmetric division in Arabidopsis. We identify a plant-specific cyclin-dependent kinase inhibitor, SIAMESE-RELATED4 (SMR4), as a MUTE-induced molecular brake that decelerates the cell cycle. SMR4 physically and functionally associates with CYCD3;1 and extends the G1 phase of asymmetric divisions. By contrast, SMR4 fails to interact with CYCD5;1, a MUTE-induced G1 cyclin, and permits the symmetric division. Our work unravels a molecular framework of the proliferation-to-differentiation switch within the stomatal lineage and suggests that a timely proliferative cell cycle is critical for stomatal-lineage identity.


Assuntos
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Ciclo Celular , Diferenciação Celular , Linhagem da Célula , Desaceleração , Regulação da Expressão Gênica de Plantas , Estômatos de Plantas
15.
Plant Cell ; 34(5): 2019-2037, 2022 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-35157082

RESUMO

Stomata optimize land plants' photosynthetic requirements and limit water vapor loss. So far, all of the molecular and electrical components identified as regulating stomatal aperture are produced, and operate, directly within the guard cells. However, a completely autonomous function of guard cells is inconsistent with anatomical and biophysical observations hinting at mechanical contributions of epidermal origins. Here, potassium (K+) assays, membrane potential measurements, microindentation, and plasmolysis experiments provide evidence that disruption of the Arabidopsis thaliana K+ channel subunit gene AtKC1 reduces pavement cell turgor, due to decreased K+ accumulation, without affecting guard cell turgor. This results in an impaired back pressure of pavement cells onto guard cells, leading to larger stomatal apertures. Poorly rectifying membrane conductances to K+ were consistently observed in pavement cells. This plasmalemma property is likely to play an essential role in K+ shuttling within the epidermis. Functional complementation reveals that restoration of the wild-type stomatal functioning requires the expression of the transgenic AtKC1 at least in the pavement cells and trichomes. Altogether, the data suggest that AtKC1 activity contributes to the building of the back pressure that pavement cells exert onto guard cells by tuning K+ distribution throughout the leaf epidermis.


Assuntos
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Fotossíntese , Folhas de Planta/metabolismo , Estômatos de Plantas/metabolismo
16.
Plant Cell ; 34(5): 1890-1911, 2022 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-35166333

RESUMO

The unique morphology of grass stomata enables rapid responses to environmental changes. Deciphering the basis for these responses is critical for improving food security. We have developed a planta platform of single-nucleus RNA-sequencing by combined fluorescence-activated nuclei flow sorting, and used it to identify cell types in mature and developing stomata from 33,098 nuclei of the maize epidermis-enriched tissues. Guard cells (GCs) and subsidiary cells (SCs) displayed differential expression of genes, besides those encoding transporters, involved in the abscisic acid, CO2, Ca2+, starch metabolism, and blue light signaling pathways, implicating coordinated signal integration in speedy stomatal responses, and of genes affecting cell wall plasticity, implying a more sophisticated relationship between GCs and SCs in stomatal development and dumbbell-shaped guard cell formation. The trajectory of stomatal development identified in young tissues, and by comparison to the bulk RNA-seq data of the MUTE defective mutant in stomatal development, confirmed known features, and shed light on key participants in stomatal development. Our study provides a valuable, comprehensive, and fundamental foundation for further insights into grass stomatal function.


Assuntos
Estômatos de Plantas , Zea mays , Humanos , Folhas de Planta/metabolismo , Estômatos de Plantas/metabolismo , Poaceae/genética , Transcriptoma/genética , Zea mays/genética
18.
Methods Mol Biol ; 2462: 111-123, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35152384

RESUMO

Different parts of a plant can be simultaneously exposed to very different conditions, for example a leaf moving in and out of shadow. In addition to local responses, transmission of information between different tissues and organs is thought to affect the coordination of overall responses to changing environmental conditions. An important adaptive role is played by the stomata, which regulate the evaporation of water vapor and supply of CO2 for photosynthesis. Here, we describe a method to study the effect of distally triggered systemic signals on stomatal conductance. The experimental set up, consisting of a growth chamber and a leaf gas exchange measuring system, enables time-resolved measurements on an intact leaf while maintaining a full control over the environmental conditions of the measured leaf and the whole seedling. The method can be used as a powerful tool to study short- and long-term stomatal responses to changes in different environmental variables, such as light.


Assuntos
Fotossíntese , Estômatos de Plantas , Dióxido de Carbono , Fotossíntese/fisiologia , Folhas de Planta/fisiologia , Estômatos de Plantas/fisiologia , Plantas
19.
Proc Natl Acad Sci U S A ; 119(9)2022 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-35173013

RESUMO

Multicellular organisms develop specialized cell types to achieve complex functions of tissues and organs. The basic helix-loop-helix (bHLH) proteins act as master regulatory transcription factors of such specialized cell types. Plant stomata are cellular valves in the aerial epidermis for efficient gas exchange and water control. Stomatal differentiation is governed by sequential actions of three lineage-specific bHLH proteins, SPEECHLESS (SPCH), MUTE, and FAMA, specifying initiation and proliferation, commitment, and terminal differentiation, respectively. A broadly expressed bHLH, SCREAM (SCRM), heterodimerizes with SPCH/MUTE/FAMA and drives stomatal differentiation via switching its partners. Yet nothing is known about its heterodimerization properties or partner preference. Here, we report the role of the SCRM C-terminal ACT-like (ACTL) domain for heterodimerization selectivity. Our intragenic suppressor screen of a dominant scrm-D mutant identified the ACTL domain as a mutation hotspot. Removal of this domain or loss of its structural integrity abolishes heterodimerization with MUTE, but not with SPCH or FAMA, and selectively abrogates the MUTE direct target gene expression. Consequently, the scrm-D ACTL mutants confer massive clusters of arrested stomatal precursor cells that cannot commit to differentiation when redundancy is removed. Structural and biophysical studies further show that SPCH, MUTE, and FAMA also possess the C-terminal ACTL domain, and that ACTL•ACTL heterodimerization is sufficient for partner selectivity. Our work elucidates a role for the SCRM ACTL domain in the MUTE-governed proliferation-differentiation switch and suggests mechanistic insight into the biological function of the ACTL domain, a module uniquely associated with plant bHLH proteins, as a heterodimeric partner selectivity interface.


Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Proteínas de Plantas/metabolismo , Estômatos de Plantas/metabolismo , Dimerização
20.
Nat Commun ; 13(1): 652, 2022 02 03.
Artigo em Inglês | MEDLINE | ID: mdl-35115512

RESUMO

Stomatal opening requires the provision of energy in the form of ATP for proton pumping across the guard cell (GC) plasma membrane and for associated metabolic rearrangements. The source of ATP for GCs is a matter of ongoing debate that is mainly fuelled by controversies around the ability of GC chloroplasts (GCCs) to perform photosynthesis. By imaging compartment-specific fluorescent ATP and NADPH sensor proteins in Arabidopsis, we show that GC photosynthesis is limited and mitochondria are the main source of ATP. Unlike mature mesophyll cell (MC) chloroplasts, which are impermeable to cytosolic ATP, GCCs import cytosolic ATP through NUCLEOTIDE TRANSPORTER (NTT) proteins. GCs from ntt mutants exhibit impaired abilities for starch biosynthesis and stomatal opening. Our work shows that GCs obtain ATP and carbohydrates via different routes from MCs, likely to compensate for the lower chlorophyll contents and limited photosynthesis of GCCs.


Assuntos
Trifosfato de Adenosina/metabolismo , Arabidopsis/metabolismo , Cloroplastos/metabolismo , Estômatos de Plantas/metabolismo , Amido/metabolismo , Arabidopsis/citologia , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Transporte Biológico , Cloroplastos/efeitos dos fármacos , Cloroplastos/efeitos da radiação , Citosol/metabolismo , Peróxido de Hidrogênio/farmacologia , Luz , Células do Mesofilo/citologia , Células do Mesofilo/metabolismo , Células do Mesofilo/efeitos da radiação , Microscopia Confocal , NADP/metabolismo , Proteínas de Transporte de Nucleotídeos/genética , Proteínas de Transporte de Nucleotídeos/metabolismo , Oxidantes/farmacologia , Epiderme Vegetal/citologia , Epiderme Vegetal/metabolismo , Folhas de Planta/citologia , Folhas de Planta/metabolismo , Estômatos de Plantas/citologia , Estômatos de Plantas/fisiologia , Plantas Geneticamente Modificadas
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