保卫细胞中ABA信号调控机制研究进展

脱落酸(ABA)具有调节植物快速响应逆境的重要功能。植物细胞中ABA核心信号通路由ABA受体PYR1/PYLs/RCARs、A类碱性蛋白磷酸酶PP2Cs和Snf1相关蛋白激酶SnRK2s组成。活性氧(ROS)和Ca²⁺是保卫细胞中的重要第二信使,调控ABA诱导的气孔关闭。该文对保卫细胞中核心ABA信号蛋白的调控以及ROS和Ca²⁺介导的ABA信号转导等最新研究成果进行综述,旨在阐明保卫细胞中ABA信号调控机制。     

Modeling the Calcium Signaling in Stomatal Guard Cells under the Action of Abscisic Acid

A theoretical model of calcium signaling is presented that simulates oscillations of cytoplasmic calcium concentration ([Ca²⁺]_cyt) in stomatal guard cells under the action of abscisic acid. The model is based on the kinetics of inositol 1,4,5-trisphosphate-sensitive calcium channels of endoplasmic reticulum and cyclic ADP-ribose-sensitive calcium channels of the tonoplast. The operation of two energy-dependent pumps—the Ca²⁺-ATPase of the endoplasmic reticulum and the Ca²⁺/H⁺ antiporter of the tonoplast—is also included in the model. It is shown that the removal of excessive Ca²⁺ from the cytoplasm by the tonoplast Ca²⁺/H⁺ antiporter is the main factor accounting for generation of [Ca²⁺]_cyt oscillations at a wide range of ABA concentrations (0.01–1 M). The long period of [Ca²⁺]_cyt oscillations in plant cells is explained by a slow release from inhibition of inositol 1,4,5-trisphosphate-gated calcium channels.     

Chitosan-Induced Stomatal Closure Accompanied by Peroxidase-Mediated Reactive Oxygen Species Production in Arabidopsis

Chitosan induced stomatal closure in wild type-plants and NADPH oxidase knock-out mutants (atrbohD atrbohF), and reactive oxygen species (ROS) production in wild-type guard cells. Closure and production were completely abolished by catalase and a peroxidase inhibitor. These results indicate that chitosan induces ROS production mediated by peroxidase, resulting in stomatal closure.     

保卫细胞的ABA信号转导

植物激素脱落酸(ABA)调节植物体多种生理过程,尤其在一些逆境条件下,植物体中ABA大量合成,诱导气孔关闭,从而有效地调控植物体内的水分平衡.尽管人们对ABA诱导气孔关闭作用已得到共识,但有关信号转导的细节还很不清楚.该文简要介绍了研究气孔保卫细胞信号转导途径的相关技术以及与ABA信号转导直接相关的ABA受体、第二信使、蛋白质磷酸化和离子通道调节等方面的最新妍究进展.并在前人研究工作的基础上,勾画出气孔保卫细胞ABA、H2O2的信号转导模式图.     

脱落酸与植物细胞的抗氧化防护

水分胁迫是一种影响植物生长发育、限制植物产量的重要胁迫因子.植物能够通过感知刺激、产生和传导信号、启动各种防护机制来响应与适应水分胁迫.植物激素脱落酸(ABA)作为一种胁迫信号,在调节植物对水分胁迫的反应中起着重要的作用.ABA不仅能诱导气孔关闭,而且能诱导编码耐脱水蛋白的基因表达.正在增加的证据显示,ABA增强水分胁迫的耐性与其诱导抗氧化防护系统有关.本文综述了ABA在诱导活性氧(ROS)产生、调节抗氧化酶基因表达以及增强抗氧化防护系统方面的作用,着重讨论了在ABA诱导的抗氧化防护过程中Ca2 、NADPH氧化酶与ROS之间的交谈机制.     

脱落酸与植物细胞的抗氧化防护

水分胁迫是一种影响植物生长发育、限制植物产量的重要胁迫因子。植物能够通过感知刺激、产生和传导信号、启动各种防护机制来响应与适应水分胁迫。植物激素脱落酸(ABA)作为一种胁迫信号,在调节植物对水分胁迫的反应中起着重要的作用。ABA不仅能诱导气孔关闭,而且能诱导编码耐脱水蛋白的基因表达。正在增加的证据显示,ABA增强水分胁迫的耐性与其诱导抗氧化防护系统有关。本文综述了ABA在诱导活性氧(ROS)产生、调节抗氧化酶基因表达以及增强抗氧化防护系统方面的作用,着重讨论了在ABA诱导的抗氧化防护过程中Ca2 、NADPH氧化酶与ROS之间的交谈机制。     

植物ABA-H2O2介导的气孔关闭

本文综述了脱落酸作为根源信号物质经由木质部被传递到叶片,经重新分配再与脱落酸受体结合,然后刺激气孔开放因子,调节烟酰胺腺嘌呤二核苷酸磷酸氧化酶等关键酶活性产生过氧化氢,过氧化氢可使胞质碱化并刺激钙离子通道使钙离子内流,活化阴离子通道使阴离子外流,最终导致气孔关闭的一系列过程。该过程涉及到的因子包括：脱落酸受体、气孔开放因子、磷脂酰环己六醇、分裂原激活蛋白激酶、烟酰胺腺嘌呤二核苷酸磷酸氧化酶、Ca^（2＋）、pH、一氧化氮等。     

The Involvement of Intracellular Glutathione in Methyl Jasmonate Signaling in Arabidopsis Guard Cells

We examined the involvement of intracellular glutathione (GSH) in methyl jasmonate (MeJA) signaling. The chlorina1-1 (ch1-1) mutation decreased GSH in guard cells and narrowed the stomatal aperture. GSH monoethyl ester increased intracellular GSH, diminishing this phenotype. GSH did not affect MeJA-induced reactive oxygen species production or cytosolic Ca²⁺ oscillation, suggesting that GSH modulates MeJA signaling downstream of production and oscillation.     

脱落酸抑制蓝光依赖气孔开放运动的生理机制分析

以蚕豆(Vicia fabaL.)为材料,采用表皮条生物学分析技术、远红外成像技术以及电生理膜片钳技术,研究逆境信号脱落酸(ABA)和蓝光信号对蚕豆叶片表皮气孔运动及质膜K+通道的影响,以探讨ABA调节蓝光诱导的气孔开放运动的生理机制.结果表明:(1)100μmol?m-2?s-1蓝光能显著诱导气孔开放,该效应可被ABA以浓度依赖的方式抑制,并以10μmol?L-1ABA抑制效应最为明显.(2)100μmol?m-2?s-1蓝光处理能明显促使蚕豆叶面温度下降,而10μmol?L-1ABA可显著阻止蓝光诱导的蚕豆叶面温度下降.(3)100μmol?m-2?s-1蓝光可明显激活保卫细胞质膜内向K+通道,处理5 min后内向K+电流增加58%;对于1和10μmol?L-1ABA预处理蚕豆保卫细胞原生质体,在蓝光处理5 min后其内向K+电流增加值分别被抑制25%和51%,但10μmol?L-1ABA并不明显抑制壳梭孢菌素(质膜H+-ATP酶永久性激活剂)诱导的保卫细胞内向K+电流上升.研究发现,逆境信号ABA可能主要通过抑制蓝光信号转导中质膜H+-ATP酶上游位点,阻断蓝光激活的保卫细胞质膜内向K+通道,抑制蓝光诱...     

Abscisic Acid-Induced Stomatal Closure in Vicia faba Epidermal Strips. Excretion of Solutes from Guard Cells and Increase in Elastic Modulus of Guard Cell Wall

The effects of abscisic acid (ABA) on the size of the apertureof stomata on epidermal strips of Vicia faba were studied inincubation media with different pH values. The osmotic potentialof guard cells, as determined by the limiting plasmolysis method,was higher at pH 4.0 than at pH 6.0, although the size of thestomatal apertures was almost identical at both pH values. AtpH 4.0, ABA effectively caused stomatal closure but had onlya small effect on the osmotic potential, whereas, at pH 6.0,ABA significantly increased the osmotic potential. ABA promotedthe efflux of Cl^– and malate from epidermal strips intothe incubation medium, an effect which was more marked at pH6.0, with a concomitant efflux of K⁺ to balance the charge onthe exported anions. From these results, it is suggested thatABA may cause an increase in the elastic modulus of the cellwalls of guard cells. ³ Present address: Nagano Prefectural Vegetable and OrnamentalCrops Experimental Station, 2206 Oomuro, Matsusiro-machi, Nagano381-12, Japan (Received September 30, 1986; Accepted January 9, 1987)     

Modulation of Root Signals in Relation to Stomatal Sensitivity to Root-sourced Abscisic Acid in Drought-affected Plants

Stomatal sensitivity to root signals induced by soil drying may vary between environments and plant species. This is likely to be a result of the interactions and modulations ámong root signals. As a stress signal, abscisic acid （ABA） plays a central role in root to shoot signaling, pH and hydraulic signals may interact with ABA signals and thus, jointly regulate stomatal responses to changed soil water status, pH itself can be modified by several factors, among which the chemical compositions in the xylem stream and the live cells surrounding the vessels play crucial roles. In addition to the xylem pH, more attention should be paid to the direct modulation of leaf apoplastic pH, because many chemical compositions might strongly modify the leaf apoplastic pH while having no significant effect on the xylem pH. The direct modulation of the ABA signal intensity may be more important for the regulation of stomatal responses to soil drying than the ABA signal per se. The ABA signal is also regulated by the ABA catabolism and the supply of precursors to the roots if a sustained root to shoot communication of soil drying operates at the whole plant level. More importantly, ABA catabolism could play crucial roles in the determination of the fate of the ABA signal and thereby control the stomatal behavior of the root-sourced ABA signal.     

Role of Reactive Oxygen Species and Glutathione in Inorganic Mercury-Induced Injury in Human Glioma Cells

The present study was undertaken to examine the role of reactive oxygen species (ROS) and glutathione (GSH) in glia cells using human glioma cell line A172 cells. HgCl₂ caused the loss of cell viability in a dose-dependent manner. HgCl₂-induced loss of cell viability was not affected by H₂O₂ scavengers catalase and pyruvate, a superoxide scavenger superoxide dismutase, a peroxynitrite scavenger uric acid, and an inhibitor of nitric oxide N^G-nitro-arginine Methyl ester. HgCl₂ did not cause changes in DCF fluorescence, an H₂O₂-sensitive fluorescent dye. The loss of cell viability was significantly prevented by the hydroxyl radical scavengers dimethylthiourea and thiourea, but it was not affected by antioxidants DPPD and Trlox. HgCl₂-induced loss of cell viability was accompanied by a significant reduction in GSH content. The GSH depletion was almost completely prevented by thiols dithiothreitol and GSH, whereas the loss of viability was partially prevented by these agents. Incubation of cells with 0.2 mM buthionine sulfoximine for 24 hr, a selective inhibitor of -glutamylcysteine synthetase, resulted in 56% reduction in GSH content without any change in cell viability. HgCl² resulted in 34% reduction in GSH content, which was accompanied by 59% loss of cell viability. These results suggest that HgCl₂-induced cell death is not associated with generation of H₂O₂ and ROS-induced lipid peroxidation. In addition, these data suggest that the depletion of endogenous GSH itself may not play a critical role in the HgCl₂-induced cytotoxicity in human glioma cells.     

Overexpression of Arabidopsis acyl‐CoA‐binding protein ACBP2 enhances drought tolerance

Arabidopsis thaliana acyl‐CoA‐binding protein 2 (ACBP2) is a stress‐responsive protein that is also important in embryogenesis. Here, we assign a role for ACBP2 in abscisic acid (ABA) signalling during seed germination, seedling development and the drought response. ACBP2 was induced by ABA and drought, and transgenic Arabidopsis overexpressing ACBP2 (ACBP2‐OXs) showed increased sensitivity to ABA treatment during germination and seedling development. ACBP2‐OXs also displayed improved drought tolerance and ABA‐mediated reactive oxygen species (ROS) production in guard cells, thereby promoting stomatal closure, reducing water loss and enhancing drought tolerance. In contrast, acbp2 mutant plants showed decreased sensitivity to ABA in root development and were more sensitive to drought stress. RNA analyses revealed that ACBP2 overexpression up‐regulated the expression of Respiratory Burst Oxidase Homolog D (AtrbohD) and AtrbohF, two NAD(P)H oxidases essential for ABA‐mediated ROS production, whereas the expression of Hypersensitive to ABA1 (HAB1), an important negative regulator in ABA signalling, was down‐regulated. In addition, transgenic plants expressing ACBP2pro:GUS showed beta‐glucuronidase (GUS) staining in guard cells, confirming a role for ACBP2 at the stomata. These observations support a positive role for ACBP2 in promoting ABA signalling in germination, seedling development and the drought response.     

Regulation of Water Deficit-Induced Abscisic Acid Accumulation by Apoplastic Ascorbic Acid in Maize Seedlings

Water deficit-induced abscisic acid （ABA） accumulation is one of the most important stress signaling pathways in plant cells. Redox regulation of cellular signaling has currently attracted particular attention, but much less is known about its roles and mechanisms in plant signaling. Herein, we report that water deficit-induced ABA accumulation could be regulated by ascorbic acid （AA）-controlled redox status in leave apoplast. The AA content in non-stressed leaves was approximately 3 umol/g FW, corresponding to a mean concentration of 3 mmol/L in a whole cell. Because AA is mainly localized in the cytosol and chloroplasts, the volume of which is much smaller than that of the whole cell, AA content in cytosolic and chloroplast compartments should be much higher than 3 mmol/L. Water deficit-induced ABA accumulation in both leaf and root tissues of maize seedlings was significantly inhibited by AA and reduced glutathione （GSH） at concentrations of 500 umol/L and was completely blocked by 50 mmol/L AA and GSH. These results suggest that the AA-induced inhibition of ABA accumulation should not occur at sites where AA exists in high concentrations. Although water deficit led to a small increase in the dehydroascorbic acid （DHA） content, no significant changes in AA content were observed in either leaf or root tissues. When compared with the whole leaf cell, the AA content in the apoplastic compartment was much lower （i.e. approximately 70 nmol/g FW, corresponding to 0.7 mmol/L）. Water deficit induced a significant decrease （approximately 2.5-fold） in the AA content and an increase （approximately 3.4-fold） in the DHA content in the apoplastic compartment, thus leading to a considerably decreased redox status there, which may have contributed to the relief of AA-induced inhibition of ABA accumulation, alternatively, promoting water deficit-induced ABA accumulation. Reactive oxygen species （ROS） could not mimic water deficit in inducing ABA accumulation, suggesting that the inhibition of ABA accumulation by AA or GSH was not related to their ROS-scavenging ability. The results of the present study suggest that the redox status in the apoplastic compartment, as determined by AA and DHA, may play a vital role in the regulation of the signaling process for water deficit-induced ABA accumulation.     

脱落酸对水稻抽穗开花期高温胁迫的诱抗效应

为探究脱落酸(ABA)对水稻(Oryzasativa)抽穗开花期高温胁迫的诱抗效应,以江西省主推水稻品种黄华占为材料,于孕穗期用蒸馏水、ABA溶液(10、50和100μmol·L^-1)、氟啶酮(FLU)和原花青素(PC) 6种溶液进行叶面喷施,然后移入对照(CK)和高温胁迫(HS)环境处理8天,考查籽粒活性氧(ROS)积累、抗氧化防御能力、产量构成及相关基因的表达。结果表明,高温胁迫下,水稻的穗长、穗重、结实率、千粒重和产量与超氧阴离子和过氧化氢含量呈显著负相关。高温胁迫下,喷施ABA显著上调了ABA应答和抗氧化防御基因的表达,籽粒中活性氧含量下降了8.24%–31.35%;喷施ABA显著增加了水稻的穗长、穗重、结实率和千粒重,显著上调了产量形成基因的表达,增产12.73%–20.77%。高温胁迫下,喷施FLU可抑制ABA的生物合成,导致ROS过量积累和水稻减产;喷施抗氧化剂PC则抑制ROS过量积累,使产量增加。以上结果表明,高温胁迫下,孕穗期喷施ABA不仅能够激发ABA信号通路,而且上调抗氧化防御能力和产量形成基因的表达,进而提高水稻在抽穗开花期的耐热性,达到增...     

过氧化氢在水杨酸诱导的蚕豆气孔关闭中的作用

许多植物病原菌可通过气孔进入叶片组织,因此减小气孔开度有利于提高植物的抗性。我们通过表皮条分析和激光扫描共聚显微镜得到的证据表明在保卫细胞中过氧化氢可能是水杨酸信号的中间环节。SA可以浓度依赖的方式诱导气孔关闭（图1A）,H2O2也有类似的作用（图1B）。100μmol/L的水杨酸诱导的气孔关闭作用可明显地被20U/ml的过氧化氢酶或10μmol/L的Vc逆转,但CAT和Vc单独处理时诱导气孔开放的作用很微弱。单细胞中基于荧光探针DCFH的时间进程实验表明直接外加（图版I）或显微注射100μmol/L的SA均可诱导保卫细胞中H2O2产生,但以显微注射双蒸水作为对照时对DCFH荧光无影响（图版II）。这些结果暗示了植物被病原菌感染时可能通过产生H2O2导致气孔关闭而阻止病原菌继续通过气孔侵入。     

The Roles of CATALASE2 in Abscisic Acid Signaling in Arabidopsis Guard Cells

We investigated the roles of catalase (CAT) in abscisic acid (ABA)-induced stomatal closure using a cat2 mutant and an inhibitor of CAT, 3-aminotriazole (AT). Constitutive reactive oxygen species (ROS) accumulation due to the CAT2 mutation and AT treatment did not affect stomatal aperture in the absence of ABA, whereas ABA-induced stomatal closure, ROS production, and [Ca²⁺]_cyt oscillation were enhanced.