RESUMO
Plant hormones are signalling compounds that regulate crucial aspects of growth, development and environmental stress responses. Abiotic stresses, such as drought, salinity, heat, cold and flooding, have profound effects on plant growth and survival. Adaptation and tolerance to such stresses require sophisticated sensing, signalling and stress response mechanisms. In this Review, we discuss recent advances in understanding how diverse plant hormones control abiotic stress responses in plants and highlight points of hormonal crosstalk during abiotic stress signalling. Control mechanisms and stress responses mediated by plant hormones including abscisic acid, auxin, brassinosteroids, cytokinins, ethylene and gibberellins are discussed. We discuss new insights into osmotic stress sensing and signalling mechanisms, hormonal control of gene regulation and plant development during stress, hormone-regulated submergence tolerance and stomatal movements. We further explore how innovative imaging approaches are providing insights into single-cell and tissue hormone dynamics. Understanding stress tolerance mechanisms opens new opportunities for agricultural applications.
Assuntos
Ácido Abscísico , Reguladores de Crescimento de Plantas , Brassinosteroides , Citocininas , Etilenos , Regulação da Expressão Gênica de Plantas , Giberelinas , Hormônios , Ácidos Indolacéticos , Plantas/genética , Estresse Fisiológico/fisiologiaRESUMO
Plants respond to increased CO2 concentrations through stomatal closure, which can contribute to increased water use efficiency. Grasses display faster stomatal responses than eudicots due to dumbbell-shaped guard cells flanked by subsidiary cells working in opposition. However, forward genetic screening for stomatal CO2 signal transduction mutants in grasses has yet to be reported. The grass model Brachypodium distachyon is closely related to agronomically important cereal crops, sharing largely collinear genomes. To gain insights into CO2 control mechanisms of stomatal movements in grasses, we developed an unbiased forward genetic screen with an EMS-mutagenized Brachypodium distachyon M5 generation population using infrared imaging to identify plants with altered leaf temperatures at elevated CO2. Among isolated mutants, a "chill1" mutant exhibited cooler leaf temperatures than wildtype Bd21-3 parent control plants after exposure to increased [CO2]. chill1 plants showed strongly impaired high CO2-induced stomatal closure despite retaining a robust abscisic acid-induced stomatal closing response. Through bulked segregant whole-genome-sequencing analyses followed by analyses of further backcrossed F4 generation plants and generation and characterization of sodium-azide and CRISPR-cas9 mutants, chill1 was mapped to a protein kinase, Mitogen-Activated Protein Kinase 5 (BdMPK5). The chill1 mutation impaired BdMPK5 protein-mediated CO2/HCO3- sensing together with the High Temperature 1 (HT1) Raf-like kinase in vitro. Furthermore, AlphaFold2-directed structural modeling predicted that the identified BdMPK5-D90N chill1 mutant residue is located at the interface of BdMPK5 with the BdHT1 Raf-like kinase. BdMPK5 is a key signaling component that mediates CO2-induced stomatal movements and is proposed to function as a component of the primary CO2 sensor in grasses.
RESUMO
Stomatal pores close rapidly in response to low-air-humidity-induced leaf-to-air vapor pressure difference (VPD) increases, thereby reducing excessive water loss. The hydroactive signal-transduction mechanisms mediating high VPD-induced stomatal closure remain largely unknown. The kinetics of stomatal high-VPD responses were investigated by using time-resolved gas-exchange analyses of higher-order mutants in guard-cell signal-transduction branches. We show that the slow-type anion channel SLAC1 plays a relatively more substantial role than the rapid-type anion channel ALMT12/QUAC1 in stomatal VPD signaling. VPD-induced stomatal closure is not affected in mpk12/mpk4GC double mutants that completely disrupt stomatal CO2 signaling, indicating that VPD signaling is independent of the early CO2 signal-transduction pathway. Calcium imaging shows that osmotic stress causes cytoplasmic Ca2+ transients in guard cells. Nevertheless, osca1-2/1.3/2.2/2.3/3.1 Ca2+-permeable channel quintuple, osca1.3/1.7-channel double, cngc5/6-channel double, cngc20-channel single, cngc19/20crispr-channel double, glr3.2/3.3-channel double, cpk-kinase quintuple, cbl1/4/5/8/9 quintuple, and cbl2/3rf double mutants showed wild-type-like stomatal VPD responses. A B3-family Raf-like mitogen-activated protein (MAP)-kinase kinase kinase, M3Kδ5/RAF6, activates the OST1/SnRK2.6 kinase in plant cells. Interestingly, B3 Raf-kinase m3kδ5 and m3kδ1/δ5/δ6/δ7 (raf3/6/5/4) quadruple mutants, but not a 14-gene raf-kinase mutant including osmotic stress-linked B4-family Raf-kinases, exhibited slowed high-VPD responses, suggesting that B3-family Raf-kinases play an important role in stomatal VPD signaling. Moreover, high VPD-induced stomatal closure was impaired in receptor-like pseudokinase GUARD CELL HYDROGEN PEROXIDE-RESISTANT1 (GHR1) mutant alleles. Notably, the classical transient "wrong-way" VPD response was absent in ghr1 mutant alleles. These findings reveal genes and signaling mechanisms in the elusive high VPD-induced stomatal closing response pathway.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Estômatos de Plantas/metabolismo , Proteínas Quinases/metabolismo , Pressão de Vapor , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Cálcio , Dióxido de Carbono/metabolismo , Umidade , Proteínas de Membrana/metabolismo , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Folhas de Planta/metabolismo , Proteínas Quinases/genética , Transdução de Sinais/fisiologiaRESUMO
OBJECTIVE: This study aimed to elucidate postoperative outcomes in patients with spinal metastases of prostate cancer, with a focus on patient-oriented assessments. METHODS: This was a prospective multicenter registry study involving 35 centers. A total of 413 patients enrolled in the Japanese Association for Spine Surgery and Oncology Multicenter Prospective Study of Surgery for Metastatic Spinal Tumors were evaluated for inclusion. The eligible patients were followed for at least 1 year after surgery. The Frankel Classification, Eastern Cooperative Oncology Group Performance Status, visual analog scale for pain, face scale, Barthel Index, vitality index, indications for oral pain medication, and the EQ-5D-5L questionnaire were used for evaluating functional status, activities of daily living, and patient motivation. RESULTS: Of the 413 eligible patients, 41 with primary prostate cancer were included in the study. The patient-oriented assessments indicated that the patients experienced postoperative improvements in quality of life and motivation in most items, with the improvements extending for up to 6 months. More than half of the patients with Frankel classifications B or C showed improved neurological function at 1 month after surgery, and most patients presented maintained or improved their classification at 6 months. CONCLUSION: Surgical intervention for spinal metastases of prostate cancer significantly improved neurological function, quality of life, and motivation of the patients. Consequently, our results support the validity of surgical intervention for improving the neurological function and overall well-being of patients with spinal metastases of prostate cancer.
RESUMO
Epidural and subdural hematomas are commonly associated with traumatic brain injury. While surgical removal is the primary intervention for these hematomas, it is also critical to prevent and reduce complications such as post-traumatic epilepsy, which may result from inflammatory responses in the injured brain areas. In the present study, we observed that high mobility group box-1 (HMGB1) decreased in the injured brain area beneath the epidural hematoma (EDH) in rats, concurrent with elevated plasma levels of HMGB1. Anti-HMGB1 monoclonal antibody therapy strongly inhibited both HMGB1 release and the subsequent increase in plasma levels. Moreover, this treatment suppressed the up-regulation of inflammatory cytokines and related molecules such as interleukin-1-beta (IL-1ß), tumor necrosis factor-alpha (TNF-α), and inducible nitric oxide synthase (iNOS) in the injured areas. Our in vitro experiments using SH-SY5Y demonstrated that hematoma components-thrombin, heme, and ferrous ion- prompted HMGB1 translocation from the nuclei to the cytoplasm, a process inhibited by the addition of the anti-HMGB1 mAb. These findings suggest that anti-HMGB1 mAb treatment not only inhibits HMGB1 translocation but also curtails inflammation in injured areas, thereby protecting the neural tissue. Thus, anti-HMGB1 mAb therapy could serve as a complementary therapy for an EDH before/after surgery.
Assuntos
Anticorpos Monoclonais , Proteína HMGB1 , Hematoma Epidural Craniano , Proteína HMGB1/metabolismo , Animais , Ratos , Anticorpos Monoclonais/farmacologia , Anticorpos Monoclonais/uso terapêutico , Hematoma Epidural Craniano/tratamento farmacológico , Masculino , Humanos , Ratos Sprague-Dawley , Interleucina-1beta/metabolismo , Fator de Necrose Tumoral alfa/metabolismo , Citocinas/metabolismo , Óxido Nítrico Sintase Tipo II/metabolismo , Linhagem Celular TumoralRESUMO
Protein phosphorylation is a major molecular switch involved in the regulation of stomatal opening and closure. Previous research defined interaction between MAP kinase 12 and Raf-like kinase HT1 as a required step for stomatal movements caused by changes in CO2 concentration. However, whether MPK12 kinase activity is required for regulation of CO2 -induced stomatal responses warrants in-depth investigation. We apply genetic, biochemical, and structural modeling approaches to examining the noncatalytic role of MPK12 in guard cell CO2 signaling that relies on allosteric inhibition of HT1. We show that CO2 /HCO3 - -enhanced MPK12 interaction with HT1 is independent of its kinase activity. By analyzing gas exchange of plant lines expressing various kinase-dead and constitutively active versions of MPK12 in a plant line where MPK12 is deleted, we confirmed that CO2 -dependent stomatal responses rely on MPK12's ability to bind to HT1, but not its kinase activity. We also demonstrate that purified MPK12 and HT1 proteins form a heterodimer in the presence of CO2 /HCO3 - and present structural modeling that explains the MPK12:HT1 interaction interface. These data add to the model that MPK12 kinase-activity-independent interaction with HT1 functions as a molecular switch by which guard cells sense changes in atmospheric CO2 concentration.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Fosforilação , Proteínas de Arabidopsis/metabolismo , Arabidopsis/genética , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Dióxido de Carbono/metabolismo , Mutação , Estômatos de Plantas/fisiologiaRESUMO
Plasma membrane (PM) H+-ATPase in guard cells is activated by phosphorylation of the penultimate residue, threonine (Thr), in response to blue and red light, promoting stomatal opening. Previous in vitro biochemical investigation suggested that Mg2+- and Mn2+-dependent membrane-localized type 2C protein phosphatase (PP2C)-like activity mediates the dephosphorylation of PM H+-ATPase in guard cells. PP2C clade D (PP2C.D) was later demonstrated to be involved in PM H+-ATPase dephosphorylation during auxin-induced cell expansion in Arabidopsis (Arabidopsis thaliana). However, it is unclear whether PP2C.D phosphatases are involved in PM H+-ATPase dephosphorylation in guard cells. Transient expression experiments using Arabidopsis mesophyll cell protoplasts revealed that all PP2C.D isoforms dephosphorylate the endogenous PM H+-ATPase. We further analyzed PP2C.D6/8/9, which display higher expression levels than other isoforms in guard cells, observing that pp2c.d6, pp2c.d8, and pp2c.d9 single mutants showed similar light-induced stomatal opening and phosphorylation status of PM H+-ATPase in guard cells as Col-0. In contrast, the pp2c.d6/9 double mutant displayed wider stomatal apertures and greater PM H+-ATPase phosphorylation in response to blue light, but delayed dephosphorylation of PM H+-ATPase in guard cells; the pp2c.d6/8/9 triple mutant showed similar phenotypes to those of the pp2c.d6/9 double mutant. Taken together, these results indicate that PP2C.D6 and PP2C.D9 redundantly mediate PM H+-ATPase dephosphorylation in guard cells. Curiously, unlike auxin-induced cell expansion in seedlings, auxin had no effect on the phosphorylation status of PM H+-ATPase in guard cells.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Membrana Celular/metabolismo , Luz , Fosfoproteínas Fosfatases/genética , Fosfoproteínas Fosfatases/metabolismo , Fosforilação , Proteína Fosfatase 2C/metabolismo , ATPases Translocadoras de Prótons/genética , ATPases Translocadoras de Prótons/metabolismoRESUMO
Histidine-rich glycoprotein (HRG) is a multifunctional plasma protein and maintains the homeostasis of blood cells and vascular endothelial cells. In the current study, we demonstrate that HRG and recombinant HRG concentration dependently induced the phagocytic activity of isolated human neutrophils against fluorescence-labeled Escherichia coli and Staphylococcus aureus through the stimulation of CLEC1A receptors, maintaining their spherical round shape. The phagocytosis-inducing effects of HRG were inhibited by a specific anti-HRG Ab and enhanced by opsonization of bacteria with diluted serum. HRG and C5a prolonged the survival time of isolated human neutrophils, in association with a reduction in the spontaneous production of extracellular ROS. In contrast, HRG maintained the responsiveness of neutrophils to TNF-α, zymosan, and E. coli with regard to reactive oxygen species production. The blocking Ab for CLEC1A and recombinant CLEC1A-Fc fusion protein significantly inhibited the HRG-induced neutrophil rounding, phagocytic activity, and prolongation of survival time, suggesting the involvement of the CLEC1A receptor in the action of HRG on human neutrophils. These results as a whole indicated that HRG facilitated the clearance of E. coli and S. aureus by maintaining the neutrophil morphology and phagocytosis, contributing to the antiseptic effects of HRG in vivo.
Assuntos
Escherichia coli/imunologia , Lectinas Tipo C/imunologia , Neutrófilos/imunologia , Fagocitose , Proteínas/imunologia , Staphylococcus aureus/imunologia , HumanosRESUMO
STUDY DESIGN: Retrospective multicenter study. OBJECTIVES: Although surgery is frequently selected for the treatment of idiopathic spinal cord herniation (ISCH), its impact on functional outcomes has yet to be fully understood given the limited number of patients in previous studies. This study aims to evaluate the symptomatic history and surgical outcomes of ISCH. SETTING: Three institutions in Japan. METHODS: A total of 34 subjects with ISCH were retrospectively enrolled and followed up for at least 2 years. Demographic information, imaging findings, and clinical outcomes were collected. Functional status was assessed using the JOA score. RESULTS: The types of neurologic deficit were monoparesis, Brown-Sequard, and paraparesis in 5, 17, and 12 cases, with their mean disease duration being 1.2, 4.2, and 5.8 years, respectively. Significant differences in disease duration were observed between the monoparesis and Brown-Sequard groups (p < 0.01) and between the monoparesis and paraparesis groups (p = 0.04). Surgery promoted significantly better recovery rates from baseline. Correlations were observed between age at surgery and recovery rate (p < 0.01) and between disease duration and recovery rate (p = 0.04). The mean recovery rates were 82.6%, 51.6%, and 29.1% in the monoparesis, Brown-Sequard, and paraparesis groups, respectively. The monoparesis group had a significantly higher recovery rate than did the Brown-Sequard (p = 0.045) and paraparesis groups (p < 0.01). CONCLUSIONS: Longer disease duration was correlated with the progression of neurologic deficit. Older age, and worse preoperative neurologic status hindered postoperative functional recovery. These results highlight the need to consider surgical timing before neurologic symptoms deteriorate.
Assuntos
Síndrome de Brown-Séquard , Doenças da Medula Espinal , Traumatismos da Medula Espinal , Humanos , Doenças da Medula Espinal/diagnóstico por imagem , Doenças da Medula Espinal/cirurgia , Estudos Retrospectivos , Imageamento por Ressonância Magnética/métodos , Hérnia/etiologia , Hérnia/diagnóstico , Medula Espinal , Paresia , Paraparesia/etiologia , Paraparesia/cirurgia , Resultado do TratamentoRESUMO
BACKGROUND: Since osteopenia has been reported to potentially associated with the progression of scoliosis, bone mineral density (BMD) might have some influences on adolescent idiopathic scoliosis (AIS). However, little is known about longitudinal BMD changes in AIS patients. This study aimed to investigate whether osteopenia in preoperative AIS patients persist at bone maturity, and to evaluate the association between BMD and AIS severity. METHODS: We reviewed 61 AIS patients who underwent surgery when they were Risser grade 4 or below and less than 20 years old (16.6 ± 1.9 years), were followed until they were at least 18 years old and had a Risser grade of 5, and followed at least 2 years after the surgery (mean follow-up 4.9 ± 1.7 years). We evaluated radiographical parameters and proximal femur BMD before surgery and at the final follow-up. A BMD of less than the mean minus 1SD was considered as low BMD. Based on preoperative BMD, 37 patients were assigned to normal BMD (N) group (1.02 ± 0.08 g/cm2) and 24 patients to low BMD (L) group (0.82 ± 0.06 g/cm2). RESULTS: All patients in the N-group had normal BMD at the final follow-up. In the L group, 15 patients (62.5%) had low BMD at the final follow-up (L-L group; preoperative 0.79 ± 0.05 g/cm2 and final follow-up 0.78 ± 0.05 g/cm2). The mean preoperative Cobb angle was significantly larger in the L-L group (67.8 ± 11.2°) than in those with normal BMD at the final follow-up (L-N group, 55.6 ± 11.8°) or the N-N group (50.8 ± 7.6°). Preoperative BMD was significantly negative correlated with the preoperative Cobb angle. The age at surgery and mean preoperative BMI were similar in the L-N and L-L groups. CONCLUSIONS: Of AIS patients with low preoperative BMD, 62.5% still had low BMD after reaching bone maturity, and low BMD was associated with the severity of scoliosis.
Assuntos
Doenças Ósseas Metabólicas , Cifose , Escoliose , Adolescente , Humanos , Densidade Óssea , Doenças Ósseas Metabólicas/complicações , Doenças Ósseas Metabólicas/diagnóstico por imagem , Estudos Longitudinais , Radiografia , Escoliose/diagnóstico por imagem , Escoliose/cirurgiaRESUMO
The plant hormone abscisic acid (ABA) plays a central role in the regulation of stomatal movements under water-deficit conditions. The identification of ABA receptors and the ABA signaling core consisting of PYR/PYL/RCAR ABA receptors, PP2C protein phosphatases and SnRK2 protein kinases has led to studies that have greatly advanced our knowledge of the molecular mechanisms mediating ABA-induced stomatal closure in the past decade. This review focuses on recent progress in illuminating the regulatory mechanisms of ABA signal transduction, and the physiological importance of basal ABA signaling in stomatal regulation by CO2 and, as hypothesized here, vapor-pressure deficit. Furthermore, advances in understanding the interactions of ABA and other stomatal signaling pathways are reviewed here. We also review recent studies investigating the use of ABA signaling mechanisms for the manipulation of stomatal conductance and the enhancement of drought tolerance and water-use efficiency of plants.
Assuntos
Ácido Abscísico/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Estômatos de Plantas/metabolismo , Transdução de Sinais , Reguladores de Crescimento de Plantas/fisiologia , Estômatos de Plantas/fisiologia , Plantas/metabolismo , Transdução de Sinais/fisiologiaRESUMO
Protein kinase dynamics play key roles in regulation of cell differentiation, growth, development and in diverse cell signaling networks. Protein kinase sensors enable visualization of protein kinase activity in living cells and tissues in time and space. These sensors have therefore become important and powerful molecular tools for investigation of diverse kinase activities and can resolve long-standing and challenging biological questions. In the present Update, we review new advanced approaches for genetically encoded protein kinase biosensor designs developed in animal systems together with the basis of each biosensor's working principle and components. In addition, we review recent first examples of real time plant protein kinase activity biosensor development and application. We discuss how these sensors have helped to resolve how stomatal signal transduction in response to elevated CO2 merges with abscisic acid signaling downstream of a resolved basal SnRK2 kinase activity in guard cells. Furthermore, recent advances, combined with the new strategies described in this Update, can help deepen the understanding of how signaling networks regulate unique functions and responses in distinct plant cell types and tissues and how different stimuli and signaling pathways can interact.
Assuntos
Técnicas Biossensoriais/instrumentação , Células Vegetais/metabolismo , Proteínas Quinases/metabolismo , Análise de Célula Única/métodos , Análise de Célula Única/instrumentaçãoRESUMO
STUDY DESIGN: Retrospective multicenter study. OBJECTIVE: To compare the surgical outcomes and complications of posterior decompression between individuals with cervical spondylotic myelopathy (CSM) and those with ossification of the posterior longitudinal ligament (OPLL). SETTING: Seventeen medical institutions in Japan. METHODS: This study included 814 individuals with CSM (n = 636) and OPLL (n = 178) who underwent posterior decompression. Propensity score matching of the baseline characteristics was performed to compare surgical outcomes and perioperative complications between the CSM and OPLL groups. RESULTS: Before propensity score matching, the OPLL group had higher percentage of male individuals, body mass index, and number of stenosis levels and longer duration of symptoms (P < 0.01, P < 0.01, P < 0.01, and P < 0.01, respectively). After matching, the baseline characteristics were comparable between the CSM (n = 98) and OPLL (n = 98) groups. The postoperative Japanese Orthopaedic Association (JOA) scores, preoperative-to-postoperative changes in the JOA scores, and JOA score recovery rates were not significantly different between the groups (P = 0.42, P = 0.47, and P = 0.09, respectively). The postoperative visual analog scale (VAS) score for neck pain and preoperative-to-postoperative changes in the VAS score for neck pain were not significantly different between the groups (P = 0.25 and P = 0.50, respectively). The incidence of perioperative complications was comparable between groups. CONCLUSION: Neurological improvement and complication rates after surgery were comparable between individuals with CSM and those with OPLL, suggesting similar effectiveness and safety of posterior decompression for both conditions.
Assuntos
Ossificação do Ligamento Longitudinal Posterior , Doenças da Medula Espinal , Traumatismos da Medula Espinal , Espondilose , Vértebras Cervicais/cirurgia , Descompressão Cirúrgica/efeitos adversos , Humanos , Ligamentos Longitudinais/cirurgia , Masculino , Cervicalgia , Ossificação do Ligamento Longitudinal Posterior/complicações , Ossificação do Ligamento Longitudinal Posterior/cirurgia , Osteogênese , Estudos Retrospectivos , Doenças da Medula Espinal/complicações , Doenças da Medula Espinal/cirurgia , Traumatismos da Medula Espinal/complicações , Espondilose/complicações , Espondilose/cirurgia , Resultado do TratamentoRESUMO
BACKGROUND: Reoperation is usually associated with poor results and increased morbidity and hospital costs. However, the rates, causes, and risk factors for reoperation in patients undergoing lumbar spinal fusion surgery remain controversial. This study aimed to identify the risk factors for early reoperation after posterior lumbar interbody fusion surgery and to compare the clinical outcomes between patients who underwent reoperation and those who did not. METHODS: We investigated a multicenter medical record database of 1263 patients who underwent posterior lumbar interbody fusion surgery between 2012 and 2015. A total of 72 (5.7%) reoperations within two years after surgery were identified and were propensity-matched for age, sex, number of fusion segments, and surgeon's experience. RESULTS: We analyzed a total of 114 patients (57 who underwent reoperation (R group) and 57 who did not (C group)). The mean age was 62.6 ± 13.4 years, with 78 men and 36 women. The mean number of fused segments was 1.2 ± 0.5. Surgical site infection was the most common cause of reoperation. There were significant differences in the incidence of diabetes mellitus (p = 0.024), preoperative ambulation status (p = 0.046), and ASA grade (p < 0.001) between the C and R groups. The recovery rate of the Japanese Orthopaedic Association score was significantly lower in the R group compared to the C group (R: 50.5 ± 28.8%, C: 63.9 ± 33.7%, p = 0.024). There were significant differences in the bone fusion rate (R: 63.2%, C: 96.5%, p < 0.001) and incidence of screw loosening (R: 31.6%; C: 10.5%; p = 0.006). CONCLUSION: Diabetes mellitus, preoperative ambulation status, and ASA grade were significant risk factors for early reoperation following posterior lumbar interbody fusion surgery. The patients who underwent early reoperation had worse clinical outcomes than those who did not.
RESUMO
Vapour pressure deficit (VPD), the difference between the saturation and actual air vapour pressures, indicates the level of atmospheric drought and evaporative pressure on plants. VPD increases during climate change due to changes in air temperature and relative humidity. Rising VPD induces stomatal closure to counteract the VPD-mediated evaporative water loss from plants. There are important gaps in our understanding of the molecular VPD-sensing and signalling mechanisms in stomatal guard cells. Here, we discuss recent advances, research directions and open questions with respect to the three components that participate in VPD-induced stomatal closure in Arabidopsis, including: (1) abscisic acid (ABA)-dependent and (2) ABA-independent regulation of the protein kinase OPEN STOMATA 1 (OST1), and (3) the passive hydraulic stomatal response. In the ABA-dependent component, two models are proposed: ABA may be rapidly synthesised or its basal levels may be involved in the stomatal VPD response. Further studies on stomatal VPD signalling should clarify: (1) whether OST1 activation above basal activity is needed for VPD responses, (2) which components are involved in ABA-independent regulation of OST1, (3) the role of other potential OST1 targets in VPD signalling, and (4) to which extent OST1 contributes to stomatal VPD sensitivity in other plant species.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Ácido Abscísico , Estômatos de Plantas , Pressão de VaporRESUMO
Abscisic acid (ABA) plays essential roles in plant development and responses to environmental stress. ABA induces subcellular translocation and degradation of the guanine nucleotide exchange factor RopGEF1, thus facilitating ABA core signal transduction. However, the underlying mechanisms for ABA-triggered RopGEF1 trafficking/degradation remain unknown. Studies have revealed that RopGEFs associate with receptor-like kinases to convey developmental signals to small ROP GTPases. However, how the activities of RopGEFs are modulated is not well understood. Type 2C protein phosphatases stabilize the RopGEF1 protein, indicating that phosphorylation may trigger RopGEF1 trafficking and degradation. We have screened inhibitors followed by several protein kinase mutants and find that quadruple-mutant plants in the Arabidopsis calcium-dependent protein kinases (CPKs) cpk3/4/6/11 disrupt ABA-induced trafficking and degradation of RopGEF1. Moreover, cpk3/4/6/11 partially impairs ABA inhibition of cotyledon emergence. Several CPKs interact with RopGEF1. CPK4 binds to and phosphorylates RopGEF1 and promotes the degradation of RopGEF1. CPK-mediated phosphorylation of RopGEF1 at specific N-terminal serine residues causes the degradation of RopGEF1 and mutation of these sites also compromises the RopGEF1 overexpression phenotype in root hair development in Arabidopsis Our findings establish the physiological and molecular functions and relevance of CPKs in regulation of RopGEF1 and illuminate physiological roles of a CPK-GEF-ROP module in ABA signaling and plant development. We further discuss that CPK-dependent RopGEF degradation during abiotic stress could provide a mechanism for down-regulation of RopGEF-dependent growth responses.
Assuntos
Ácido Abscísico/farmacologia , Proteínas de Arabidopsis/metabolismo , Arabidopsis/crescimento & desenvolvimento , Proteínas Quinases Dependentes de Cálcio-Calmodulina/metabolismo , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Raízes de Plantas/crescimento & desenvolvimento , Proteólise/efeitos dos fármacos , Arabidopsis/efeitos dos fármacos , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas Quinases Dependentes de Cálcio-Calmodulina/genética , Fatores de Troca do Nucleotídeo Guanina/genética , Fosforilação/efeitos dos fármacos , Reguladores de Crescimento de Plantas/farmacologia , Raízes de Plantas/genética , Raízes de Plantas/metabolismo , Transporte Proteico , Transdução de Sinais/efeitos dos fármacosRESUMO
Stomatal pore apertures are narrowing globally due to the continuing rise in atmospheric [CO2]. CO2 elevation and the plant hormone abscisic acid (ABA) both induce rapid stomatal closure. However, the underlying signal transduction mechanisms for CO2/ABA interaction remain unclear. Two models have been considered: (i) CO2 elevation enhances ABA concentrations and/or early ABA signaling in guard cells to induce stomatal closure and (ii) CO2 signaling merges with ABA at OST1/SnRK2.6 protein kinase activation. Here we use genetics, ABA-reporter imaging, stomatal conductance, patch clamp, and biochemical analyses to investigate these models. The strong ABA biosynthesis mutants nced3/nced5 and aba2-1 remain responsive to CO2 elevation. Rapid CO2-triggered stomatal closure in PYR/RCAR ABA receptor quadruple and hextuple mutants is not disrupted but delayed. Time-resolved ABA concentration monitoring in guard cells using a FRET-based ABA-reporter, ABAleon2.15, and ABA reporter gene assays suggest that CO2 elevation does not trigger [ABA] increases in guard cells, in contrast to control ABA exposures. Moreover, CO2 activates guard cell S-type anion channels in nced3/nced5 and ABA receptor hextuple mutants. Unexpectedly, in-gel protein kinase assays show that unlike ABA, elevated CO2 does not activate OST1/SnRK2 kinases in guard cells. The present study points to a model in which rapid CO2 signal transduction leading to stomatal closure occurs via an ABA-independent pathway downstream of OST1/SnRK2.6. Basal ABA signaling and OST1/SnRK2 activity are required to facilitate the stomatal response to elevated CO2 These findings provide insights into the interaction between CO2/ABA signal transduction in light of the continuing rise in atmospheric [CO2].
Assuntos
Ácido Abscísico/farmacologia , Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Dióxido de Carbono/farmacologia , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Estômatos de Plantas/metabolismo , Proteínas Quinases/metabolismo , Transdução de Sinais/efeitos dos fármacos , Arabidopsis/efeitos dos fármacos , Arabidopsis/crescimento & desenvolvimento , Proteínas de Arabidopsis/genética , Mutação , Reguladores de Crescimento de Plantas/farmacologia , Estômatos de Plantas/efeitos dos fármacos , Estômatos de Plantas/crescimento & desenvolvimento , Proteínas Quinases/genética , Espécies Reativas de Oxigênio/metabolismoRESUMO
Insight into how plants simultaneously cope with multiple stresses, for example, when challenged with biotic stress from pathogen infection and abiotic stress from drought, is important both for understanding evolutionary trade-offs and optimizing crop responses to these stresses. Mechanisms by which initial plant immune signaling antagonizes abscisic acid (ABA) signal transduction require further investigation. Using a chemical genetics approach, the small molecule [5-(3,4-dichlorophenyl)furan-2-yl]-piperidine-1-ylmethanethione (DFPM) has previously been identified due to its ability to suppress ABA signaling via plant immune signaling components. Here, we have used forward chemical genetics screening to identify DFPM-insensitive loci by monitoring the activity of ABA-inducible pRAB18::GFP in the presence of DFPM and ABA. The ability of DFPM to attenuate ABA signaling was reduced in rda mutants (resistant to DFPM inhibition of ABA signaling). One of the mutants, rda2, was mapped and is defective in a gene encoding a lectin receptor kinase. RDA2 functions in DFPM-mediated inhibition of ABA-mediated reporter expression. RDA2 is required for DFPM-mediated activation of immune signaling, including phosphorylation of mitogen-activated protein kinase (MAPK) 3 (MPK3) and MPK6, and induction of immunity marker genes. Our study identifies a previously uncharacterized receptor kinase gene that is important for DFPM-mediated immune signaling and inhibition of ABA signaling. We demonstrate that the lectin receptor kinase RDA2 is essential for perceiving the DFPM signal and activating MAPKs, and that MKK4 and MKK5 are required for DFPM interference with ABA signal transduction.
Assuntos
Ácido Abscísico/metabolismo , Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Regulação da Expressão Gênica de Plantas/genética , Regulação da Expressão Gênica de Plantas/fisiologia , Transdução de Sinais/genética , Transdução de Sinais/fisiologiaRESUMO
Environmental sensing is crucial for bacterial survival and pathogenicity. Bacteria sense environmental chemicals using chemoreceptor proteins, such as Methyl-accepting Chemotaxis Proteins (MCPs). Vibrio cholerae, the etiological agent of cholera, has at least 44 chemoreceptor proteins homologous to MCP-Like Proteins (MLPs). Mlp24 and Mlp37 are dCACHE type chemoreceptors that senses various amino acids. Mlp24 is important for cholera toxin production, whereas Mlp37 is related to biofilm formation. The periplasmic ligand binding regions of Mlp24 and Mlp37 (Mlp24p and Mlp37p, respectively) share similar amino acid sequences, tertiary and quaternary structures, and a common mechanism for the ligand amino acid backbone recognition. However, Mlp37p recognizes various l-amino acids and taurine with similar affinity whereas Mlp24p shows different binding affinities for various l-amino acids and does not bind taurine. Here we solved the crystal structure of Mlp37p in complex with l-arginine and compared it with previously determined structures of Mlp37p, Mlp24p and their ligand complexes. We found that Mlp37p changes the conformation of the loop that forms the upper wall of the ligand binding pocket according to size and shape of the ligand, and thereby show similar affinity for various ligands.