气孔运动中的活性氧信号

大量研究证明活性氧(ROS)在气孔运动中起信号分子的作用。保卫细胞中ROS的产生依赖于特定的酶,其中NADPH氧化酶组分RBOH已得到深入研究,并已证实其参与生物与非生物胁迫反应。植物激素包括脱落酸(ABA)、水杨酸(SA)、乙烯、生长素及细胞分裂素等,它们均通过ROS的介导来调控气孔运动。生物胁迫(如毒性细菌和真菌)也会调控气孔运动。ROS参与这些调控过程。保卫细胞中存在多层次对ROS产生及其作用的调节,抗氧化活性物质和ROS敏感蛋白(如蛋白激酶和磷酸酶)均可传递ROS信号并调节气孔运动。ROS对离子通道调节的证据也越来越多。保卫细胞由于可通过ROS整合复杂的信号途径,已成为研究植物ROS信号转导过程的良好模式系统。     

微丝骨架和活性氧在调节气孔运动中的作用及机制

气孔运动调节植物的光合作用和蒸腾作用,对植物的生长发育和干旱等非生物胁迫的响应都起到重要的作用。保卫细胞能够通过感知胞内和胞外多种信号调节气孔开度,因此,保卫细胞已经成为植物细胞信号转导研究中广泛应用的细胞模型。该文对保卫细胞中微丝骨架和活性氧对气孔运动的调节作用、微丝骨架在调节细胞壁与质膜间联系中的作用进行了综述,最后分析了微丝骨架通过ROS(reactive oxygen species)调节保卫细胞壁–质膜联系参与气孔运动调控的可能机制。     

保卫细胞碳代谢与气孔运动

作为气孔运动渗透调节的代谢基础 ,气孔保卫细胞的碳代谢有特殊的调控机理。本文介绍了气孔保卫细胞中参与碳代谢的主要酶的特性及调控特点 ,特别是保卫细胞叶绿体中催化苹果酸形成的PEP羧化酶 ,其磷酸化和去磷酸化参与了保卫细胞信号传递。保卫细胞碳代谢调控在气孔运动调节中的作用 ,并讨论了保卫细胞碳代谢与能量代谢的关系     

保卫细胞碳代谢与气孔运动

作为气孔运动渗透调节的代谢基础,气孔保卫细胞的碳代谢有特殊的调控机理。本文介绍了气孔保卫细胞中参与碳代谢的主要酶的特性及调控特点,特别是保卫细胞叶绿体中催化苹果酸形成的PEP羧化酶,其磷酸化和去磷酸化参与了保卫细胞信号传递。保卫细胞碳代谢调控在气孔运动调节中的作用,并讨论了保卫细胞碳代谢与能量代谢的关系。     

氢气在植物抗胁迫中的作用

近年来,一些研究发现氢气作为一种新的信号分子参与植物抗胁迫网络并具有重要作用。本文综述了近年来氢气参与植物胁迫应答的研究,总结氢气主要通过调节活性氧(ROS)来参与植物抵御胁迫的过程。在植物抗干旱过程中,氢气通过促进ROS的产生来调节气孔的闭合;而在植物抗盐渍、金属离子和农药损伤过程中,氢气通过去除ROS来修复氧化损伤;氢气还对植物抗病虫害相关基因的表达有调节作用。     

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。     

植物中参与活性氧调控的基因网络

植物体内活性氧（reactive oxygen species,ROS）是氧化还原反应的必然副产物,具极高的活性和毒性,从而对细胞产生毒害。同时,活性氧作为信号分子对很多生理过程诸如植物生长发育、细胞程序化死亡及生物和非生物胁迫应答起调控作用。植物中ROS双重作用的协调机制目前尚不明确,确定的是细胞中ROS维持于稳定水平需要精细的调节。拟南芥中至少包括152个基因组成的网络参与ROS的调控,该网络具高度的灵活性和互补性。本文综述了ROS网络中鉴定的一些关键基因及细胞学定位和协同作用,ROS信号转导,尤其是叶绿体中ROS信号的调控。     

活性氧在气孔运动中的作用

水分代谢是植物基础代谢的重要组成部分,气孔开关精细地调节着植物水分散失和光合作用。气孔运动受到多种因子的调控,保卫细胞内大量的第二信使分子是响应外界刺激、调节保卫细胞代谢方式、改变保卫细胞水势进而引起气孔开关的重要功能组分。细胞内的活性氧就是其中重要的成员之一。保卫细胞中的活性氧包括过氧化氢、超氧阴离子自由基和羟自由基等,这些活性氧可以通过光合作用、呼吸作用产生或通过专门的酶催化合成,在触发下游生理反应、完成信号转导后由专门的酶将其清除。在植物激素(脱落酸、水杨酸)、一氧化氮、质外体钙调素、细胞外ATP等因子调节气孔运动的过程中,活性氧都发挥了介导作用。该文对于近年来活性氧在气孔运动过程中发挥的作用方面的研究进展进行了综述。     

保卫细胞中的微丝骨架

微丝骨架存在于多种植物的保卫细胞中,周质微丝骨架的排列和结构是动态的。越来越多的证据表明保卫细胞中的微丝骨架可作为信号调节物,对气孔的启闭运动起着重要的调控作用。本文综述了保卫细胞微丝骨架的标记方法、结构,以及其在气孔运动中的功能和作用机制的最新研究进展。     

保卫细胞中的微丝骨架

微丝骨架存在于多种植物的保卫细胞中,周质微丝骨架的排列和结构是动态的。越来越多的证据表明保卫细胞中的微丝骨架可作为信号调节物,对气孔的启闭运动起着重要的调控作用。本文综述了保卫细胞微丝骨架的标记方法、结构,以及其在气孔运动中的功能和作用机制的最新研究进展。     

The stomata frontline of plant interaction with the environment-perspectives from hormone regulation

Plants have evolved elaborate mechanisms to perceive and integrate signals from various environmental conditions.On leaf surface,stomata formed by pairs of guard cells mediate gas exchange,water transp...     

Hydrogen peroxide is involved in abscisic acid-induced stomatal closure in Vicia faba

One of the most important functions of the plant hormone abscisic acid (ABA) is to induce stomatal closure by reducing the turgor of guard cells under water deficit. Under environmental stresses, hydrogen peroxide (H(2)O(2)), an active oxygen species, is widely generated in many biological systems. Here, using an epidermal strip bioassay and laser-scanning confocal microscopy, we provide evidence that H(2)O(2) may function as an intermediate in ABA signaling in Vicia faba guard cells. H(2)O(2) inhibited induced closure of stomata, and this effect was reversed by ascorbic acid at concentrations lower than 10(-5) M. Further, ABA-induced stomatal closure also was abolished partly by addition of exogenous catalase (CAT) and diphenylene iodonium (DPI), which are an H(2)O(2) scavenger and an NADPH oxidase inhibitor, respectively. Time course experiments of single-cell assays based on the fluorescent probe dichlorofluorescein showed that the generation of H(2)O(2) was dependent on ABA concentration and an increase in the fluorescence intensity of the chloroplast occurred significantly earlier than within the other regions of guard cells. The ABA-induced change in fluorescence intensity in guard cells was abolished by the application of CAT and DPI. In addition, ABA microinjected into guard cells markedly induced H(2)O(2) production, which preceded stomatal closure. These effects were abolished by CAT or DPI micro-injection. Our results suggest that guard cells treated with ABA may close the stomata via a pathway with H(2)O(2) production involved, and H(2)O(2) may be an intermediate in ABA signaling.     

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.     

Two Arabidopsis guard cell-preferential MAPK genes,MPK9 and MPK12, function in biotic stress response

Abscisic acid (ABA) plays a major role in plant development and adaptation to severe environmental conditions. ABA evokes cellular events to regulate stomatal apertures and thus contributes to the plant’s ability to respond to abiotic stresses. Reactive oxygen species (ROS) are produced in response to ABA and mediate ABA-induced stomatal closure. We have shown that two MAP kinases, MPK9 and MPK12, are highly and preferentially expressed in guard cells and function as positive regulators of ROS-mediated ABA signaling in guard cells. Cell biological and electrophysiological analyses demonstrated that MPK9 and MPK12 act downstream of ROS and cytosolic Ca²⁺ and upstream of anion channels in the guard cell ABA signaling cascade. Plant pathogens use stomata as the primary gateway to enter into their hosts, and previous studies have indicated crosstalk between ABA and defense signaling. Here we show that mpk9-1/12-1 double mutants are highly susceptible to Pseudomonas syringae DC3000 compared to WT plants. These results suggest that the regulation of stomatal apertures by MPK9 and MPK12 contributes to the first line of defense against pathogens.     

Stomatal sensing of the environment

The effects of environmental factors on stomatal behaviour are reviewed and the questions of whether photosynthesis and transpiration eontrol stomata or whether stomata themselves control the rates of these processes is addressed. Light affects stomata directly and indirectly. Light can act directly as an energy source resulting in ATP formation within guard cells via photophosphorylation, or as a stimulus as in the case of the blue light effects which cause guard cell H⁺ extrusion. Light also acts indirectly on stomata by affecting photosynthesis which influences the intercellular leaf CO₂ concentration ( C _i). Carbon dioxide concentrations in contact with the plasma membrane of the guard cell or within the guard cell acts directly on cell processes responsible for stomatal movements. The mechanism by which CO₂ exerts its effect is not fully understood but, at least in part, it is concerned with changing the properties of guard cell plasma membranes which influence ion transport processes. The C _i may remain fairly constant for much of the day for many species which is the result of parallel responses of stomata and photosynthesis to light. Leaf water potential also influences stomatal behaviour. Since leaf water potential is a resultant of water uptake and storage by the plant and transpirational water loss, any factor which affects these processes, such as soil water availability, temperature, atmospheric humidity and air movement, may indirectly affect stomata. Some of these factors, such as temperature and possibly humidity, may affect stomata directly. These direct and indirect effects of environmental factors interact to give a net opening response upon which is superimposed a direct effect of stomatal circadian rhythmic activity.     

The coronatine-insensitive 1 mutation reveals the hormonal signaling interaction between abscisic acid and methyl jasmonate in Arabidopsis guard cells. Specific impairment of ion channel activation and second messenger production

Methyl jasmonate (MeJA) elicits stomatal closing similar to abscisic acid (ABA), but whether the two compounds use similar or different signaling mechanisms in guard cells remains to be clarified. We investigated the effects of MeJA and ABA on second messenger production and ion channel activation in guard cells of wild-type Arabidopsis (Arabidopsis thaliana) and MeJA-insensitive coronatine-insensitive 1 (coi1) mutants. The coi1 mutation impaired MeJA-induced stomatal closing but not ABA-induced stomatal closing. MeJA as well as ABA induced production of reactive oxygen species (ROS) and nitric oxide (NO) in wild-type guard cells, whereas MeJA did not induce production of ROS and NO in coi1 guard cells. The experiments using an inhibitor and scavengers demonstrated that both ROS and NO are involved in MeJA-induced stomatal closing as well as ABA-induced stomatal closing. Not only ABA but also MeJA activated slow anion channels and Ca(2+) permeable cation channels in the plasma membrane of wild-type guard cell protoplasts. However, in coi1 guard cell protoplasts, MeJA did not elicit either slow anion currents or Ca(2+) permeable cation currents, but ABA activated both types of ion channels. Furthermore, to elucidate signaling interaction between ABA and MeJA in guard cells, we examined MeJA signaling in ABA-insensitive mutant ABA-insensitive 2 (abi2-1), whose ABA signal transduction cascade has some disruption downstream of ROS production and NO production. MeJA also did not induce stomatal closing but stimulated production of ROS and NO in abi2-1. These results suggest that MeJA triggers stomatal closing via a receptor distinct from the ABA receptor and that the coi1 mutation disrupts MeJA signaling upstream of the blanch point of ABA signaling and MeJA signaling in Arabidopsis guard cells.     

Action of growth regulators on the cotyledonary stomata ofCucumis sativus L.: Structure and ontogeny

Anomocytic stomata and stomata with single subsidiary cells are commonly observed Sometimes a stoma appears anisocytic. Double cytoplasmic connections between nearby stomata and division of guard cells with persistent or degenerating nuclei are seen in GA. One or more divisions of guard cells, displaced guard cells and single guard cells with or without pore are noticed in SUC. Formation of single guard cells is a common feature in TIBA. Paracytic stomata, one and a half stomata and persistent stomatal initials are seen in SUL. COUM seems to be not inhibitory inCucumis sativus. In COL stomata with unequal guard cells, unequal stomatal cells with thickening in between but without intervening pore, stoma with double pores, persistent stomatal initials which may be solitary or in groups with varying shapes and with one or two nuclei of different shapes are noticed. The growth regulators affect the frequency of stomata, epidermal cells; stomatal index; size of guard and epidermal cells.     

NADPH oxidase AtrbohD and AtrbohF genes function in ROS-dependent ABA signaling in Arabidopsis

Reactive oxygen species (ROS) have been proposed to function as second messengers in abscisic acid (ABA) signaling in guard cells. However, the question whether ROS production is indeed required for ABA signal transduction in vivo has not yet been addressed, and the molecular mechanisms mediating ROS production during ABA signaling remain unknown. Here, we report identification of two partially redundant Arabidopsis guard cell-expressed NADPH oxidase catalytic subunit genes, AtrbohD and AtrbohF, in which gene disruption impairs ABA signaling. atrbohD/F double mutations impair ABA-induced stomatal closing, ABA promotion of ROS production, ABA-induced cytosolic Ca(2+) increases and ABA- activation of plasma membrane Ca(2+)-permeable channels in guard cells. Exogenous H(2)O(2) rescues both Ca(2+) channel activation and stomatal closing in atrbohD/F. ABA inhibition of seed germination and root elongation are impaired in atrbohD/F, suggesting more general roles for ROS and NADPH oxidases in ABA signaling. These data provide direct molecular genetic and cell biological evidence that ROS are rate-limiting second messengers in ABA signaling, and that the AtrbohD and AtrbohF NADPH oxidases function in guard cell ABA signal transduction.     

Guard-cell signalling for hydrogen peroxide and abscisic acid

Guard cells can integrate and process multiple complex signals from the environment and respond by opening and closing stomata in order to adapt to the environmental signal. Over the past several years, considerable research progress has been made in our understanding of the role of reactive oxygen species (ROS) as essential signal molecules that mediate abscisic acid (ABA)-induced stomatal closure. In this review, we discuss hydrogen peroxide (H2O2) generation and signalling, H2O2-induced gene expression, crosstalk and the specificity between ABA and H2O2 signalling, and the cellular mechanism for ROS sensing in guard cells. This review focuses especially on the points of connection between ABA and H2O2 signalling in guard cells. The fundamental progress in understanding the role of ABA and ROS in guard cells will continue to provide a rational basis for biotechnological improvements in the development of drought-tolerant crop plants with improved water-use efficiency.