FIA functions as an early signal component of abscisic acid signal cascade in Vicia faba guard cells

An abscisic acid (ABA)-insensitive Vicia faba mutant, fia (fava bean impaired in ABA-induced stomatal closure) had previously been isolated. In this study, it was investigated how FIA functions in ABA signalling in guard cells of Vicia faba. Unlike ABA, methyl jasmonate (MeJA), H(2)O(2), and nitric oxide (NO) induced stomatal closure in the fia mutant. ABA did not induce production of either reactive oxygen species or NO in the mutant. Moreover, ABA did not suppress inward-rectifying K(+) (K(in)) currents or activate ABA-activated protein kinase (AAPK) in mutant guard cells. These results suggest that FIA functions as an early signal component upstream of AAPK activation in ABA signalling but does not function in MeJA signalling in guard cells of Vicia faba.     

cGMP-dependent ABA-induced stomatal closure in the ABA-insensitive Arabidopsis mutant abi1-1

? The drought hormone abscisic acid (ABA) is widely known to produce reductions in stomatal aperture in guard cells. The second messenger cyclic guanosine 3', 5'-monophosphate (cGMP) is thought to form part of the signalling pathway by which ABA induces stomatal closure. ? We have examined the signalling events during cGMP-dependent ABA-induced stomatal closure in wild-type Arabidopsis plants and plants of the ABA-insensitive Arabidopsis mutant abi1-1. ? We show that cGMP acts downstream of hydrogen peroxide (H(2) O(2) ) and nitric oxide (NO) in the signalling pathway by which ABA induces stomatal closure. H(2) O(2) - and NO-induced increases in the cytosolic free calcium concentration ([Ca(2+) ](cyt) ) were cGMP-dependent, positioning cGMP upstream of [Ca(2+) ](cyt) , and involved the action of the type 2C protein phosphatase ABI1. Increases in cGMP were mediated through the stimulation of guanylyl cyclase by H(2) O(2) and NO. We identify nucleoside diphosphate kinase as a new cGMP target protein in Arabidopsis. ? This study positions cGMP downstream of ABA-induced changes in H(2) O(2) and NO, and upstream of increases in [Ca(2+) ](cyt) in the signalling pathway leading to stomatal closure.     

ABA-induced NO generation and stomatal closure in Arabidopsis are dependent on H2O2 synthesis

Nitric oxide (NO) and hydrogen peroxide (H(2)O(2)) are key signalling molecules produced in response to various stimuli and involved in a diverse range of plant signal transduction processes. Nitric oxide and H(2)O(2) have been identified as essential components of the complex signalling network inducing stomatal closure in response to the phytohormone abscisic acid (ABA). A close inter-relationship exists between ABA and the spatial and temporal production and action of both NO and H(2)O(2) in guard cells. This study shows that, in Arabidopsis thaliana guard cells, ABA-mediated NO generation is in fact dependent on ABA-induced H(2)O(2) production. Stomatal closure induced by H(2)O(2) is inhibited by the removal of NO with NO scavenger, and both ABA and H(2)O(2) stimulate guard cell NO synthesis. Conversely, NO-induced stomatal closure does not require H(2)O(2) synthesis nor does NO treatment induce H(2)O(2) production in guard cells. Tungstate inhibition of the NO-generating enzyme nitrate reductase (NR) attenuates NO production in response to nitrite in vitro and in response to H(2)O(2) and ABA in vivo. Genetic data demonstrate that NR is the major source of NO in guard cells in response to ABA-mediated H(2)O(2) synthesis. In the NR double mutant nia1, nia2 both ABA and H(2)O(2) fail to induce NO production or stomatal closure, but in the nitric oxide synthase deficient Atnos1 mutant, responses to H(2)O(2) are not impaired. Importantly, we show that in the NADPH oxidase deficient double mutant atrbohD/F, NO synthesis and stomatal closure to ABA are severely reduced, indicating that endogenous H(2)O(2) production induced by ABA is required for NO synthesis. In summary, our physiological and genetic data demonstrate a strong inter-relationship between ABA, endogenous H(2)O(2) and NO-induced stomatal closure.     

ABA, hydrogen peroxide and nitric oxide signalling in stomatal guard cells

Increased synthesis and redistribution of the phytohormone abscisic acid (ABA) in response to water deficit stress initiates an intricate network of signalling pathways in guard cells leading to stomatal closure. Despite the large number of ABA signalling intermediates that are known in guard cells, new discoveries are still being made. Recently, the reactive oxygen species hydrogen peroxide (H2O2) and the reactive nitrogen species nitric oxide (NO) have been identified as key molecules regulating ABA-induced stomatal closure in various species. As with many other physiological responses in which H2O2 and NO are involved, stomatal closure in response to ABA also appears to require the tandem synthesis and action of both these signalling molecules. Recent pharmacological and genetic data have identified NADPH oxidase as a source of H2O2, whilst nitrate reductase has been identified as a source of NO in Arabidopsis guard cells. Some signalling components positioned downstream of H2O2 and NO are calcium, protein kinases and cyclic GMP. However, the exact interaction between the various signalling components in response to H2O2 and NO in guard cells remains to be established.     

NO可能作为H2O2的下游信号介导ABA诱导的蚕豆气孔关闭

ABA、H2O2和硝普钠(SNP)均能诱导蚕豆气孔关闭.NO的清除剂c-PTIO可以减轻由ABA或H2O2所诱导的蚕豆气孔关闭的程度,而过氧化氢酶(CAT)则不能减轻NO诱导的气孔关闭程度.激光共聚焦显微检测结果显示,10μmo1/L的ABA处理后,胞内H2O2的产生速率明显高于NO的产生速率;CAT几乎可完全抑制ABA所诱导的DAF的荧光增加;外源H2O2能显著诱导胞内DAF的荧光增加;c-PTIO对ABA诱导的DCF荧光略有促进作用,但外源SNP不能诱导胞内DCF荧光增加.这些结果表明,在ABA诱导气孔关闭过程中,H2O2可能在NO的上游起作用并受NO的负反馈调节.     

Nitric oxide inhibits blue light-specific stomatal opening via abscisic acid signaling pathways in Vicia guard cells

Recent evidence suggests that nitric oxide (NO) acts as an intermediate of ABA signal transduction for stomatal closure. However, NO's effect on stomatal opening is poorly understood even though both opening and closing activities determine stomatal aperture. Here we show that NO inhibits stomatal opening specific to blue light, thereby stimulating stomatal closure. NO inhibited blue light-specific stomatal opening but not red light-induced opening. NO inhibited both blue light-induced H(+) pumping and H(+)-ATPase phosphorylation. The NO scavenger 2-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (c-PTIO) restored all these inhibitory effects. ABA and hydrogen peroxide (H(2)O(2)) inhibited all of these blue light-specific responses in a manner similar to NO. c-PTIO partially restored the ABA-induced inhibition of all of these opening responses but did not restore inhibition of the responses by H(2)O(2). ABA, H(2)O(2) and NO had slight inhibitory effects on the phosphorylation of phototropins, which are blue light receptors in guard cells. NO inhibited neither fusicoccin-induced H(+) pumping in guard cells nor H(+) transport by H(+)-ATPase in the isolated membranes. From these results, we conclude that both NO and H(2)O(2) inhibit blue light-induced activation of H(+)-ATPase by inhibiting the component(s) between phototropins and H(+)-ATPase in guard cells and stimulate stomatal closure by ABA.     

Differential requirement for NO during ABA-induced stomatal closure in turgid and wilted leaves

Abscisic acid (ABA)-induced stomatal closure is mediated by a complex, guard cell signalling network involving nitric oxide (NO) as a key intermediate. However, there is a lack of information concerning the role of NO in the ABA-enhanced stomatal closure seen in dehydrated plants. The data herein demonstrate that, while nitrate reductase (NR)1-mediated NO generation is required for the ABA-induced closure of stomata in turgid leaves, it is not required for ABA-enhanced stomatal closure under conditions leading to rapid dehydration. The results also show that NO signalling in the guard cells of turgid leaves requires the ABA-signalling pathway to be both capable of function and active. The alignment of this NO signalling with guard cell Ca²⁺-dependent/independent ABA signalling is discussed. The data also highlight a physiological role for NO signalling in turgid leaves and show that stomatal closure during the light-to-dark transition requires NR1-mediated NO generation and signalling.     

Ethylene-induced stomatal closure in Arabidopsis occurs via AtrbohF-mediated hydrogen peroxide synthesis

Ethylene is a plant hormone that regulates many aspects of growth and development. Despite the well-known association between ethylene and stress signalling, its effects on stomatal movements are largely unexplored. Here, genetic and physiological data are provided that position ethylene into the Arabidopsis guard cell signalling network, and demonstrate a functional link between ethylene and hydrogen peroxide (H(2)O(2)). In wild-type leaves, ethylene induces stomatal closure that is dependent on H(2)O(2) production in guard cells, generated by the nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) oxidase AtrbohF. Ethylene-induced closure is inhibited by the ethylene antagonists 1-MCP and silver. The ethylene receptor mutants etr1-1 and etr1-3 are insensitive to ethylene in terms of stomatal closure and H(2)O(2) production. Stomata of the ethylene signalling ein2-1 and arr2 mutants do not close in response to either ethylene or H(2)O(2) but do generate H(2)O(2) following ethylene challenge. Thus, the data indicate that ethylene and H(2)O(2) signalling in guard cells are mediated by ETR1 via EIN2 and ARR2-dependent pathway(s), and identify AtrbohF as a key mediator of stomatal responses to ethylene.     

Heterotrimeric G-protein regulation of ROS signalling and calcium currents in Arabidopsis guard cells

Heterotrimeric G proteins composed of Gα, Gβ, and Gγ subunits are important signalling agents in both animals and plants. In plants, G proteins modulate numerous responses, including abscisic acid (ABA) and pathogen-associated molecular pattern (PAMP) regulation of guard cell ion channels and stomatal apertures. Previous analyses of mutants deficient in the sole canonical Arabidopsis Gα subunit, GPA1, have shown that Gα-deficient guard cells are impaired in ABA inhibition of K(+) influx channels, and in pH-independent activation of anion efflux channels. ABA-induced Ca(2+) uptake through ROS-activated Ca(2+)-permeable channels in the plasma membrane is another key component of ABA signal transduction in guard cells, but the question of whether these channels are also dependent on Gα for their ABA response has not been evaluated previously. We used two independent Arabidopsis T-DNA null mutant lines, gpa1-3 and gpa1-4, to investigate this issue. We observed that gpa1 mutants are disrupted both in ABA-induced Ca(2+)-channel activation, and in production of reactive oxygen species (ROS) in response to ABA. However, in response to exogenous H(2)O(2) application, I(Ca) channels are activated normally in gpa1 guard cells. In addition, H(2)O(2) inhibition of stomatal opening and promotion of stomatal closure are not disrupted in gpa1 mutant guard cells. These data indicate that absence of GPA1 interrupts ABA signalling between ABA reception and ROS production, with a consequent impairment in Ca(2+)-channel activation.     

Evidence for chloroplast control of external Ca2+-induced cytosolic Ca2+ transients and stomatal closure

The role of guard cell chloroplasts in stomatal function is controversial. It is usually assumed that stomatal closure is preceded by a transient increase in cytosolic free Ca(2+) concentration ([Ca(2+)](cyt)) in the guard cells. Here, we provide the evidence that chloroplasts play a critical role in the generation of extracellular Ca(2+) ([Ca(2+)](ext))-induced [Ca(2+)](cyt) transients and stomatal closure in Arabidopsis. CAS (Ca(2+) sensing receptor) is a plant-specific putative Ca(2+)-binding protein that was originally proposed to be a plasma membrane-localized external Ca(2+) sensor. In the present study, we characterized the intracellular localization of CAS in Arabidopsis with a combination of techniques, including (i) in vivo localization of green fluorescent protein (GFP) fused gene expression, (ii) subcellular fractionation and fractional analysis of CAS with Western blots, and (iii) database analysis of thylakoid membrane proteomes. Each technique produced consistent results. CAS was localized mainly to chloroplasts. It is an integral thylakoid membrane protein, and the N-terminus acidic Ca(2+)-binding region is likely exposed to the stromal side of the membrane. The phenotype of T-DNA insertion CAS knockout mutants and cDNA mutant-complemented plants revealed that CAS is essential for stomatal closure induced by external Ca(2+). In contrast, overexpression of CAS promoted stomatal closure in the absence of externally applied Ca(2+). Furthermore, using the transgenic aequorin system, we showed that [Ca(2+)](ext)-induced [Ca(2+)](cyt) transients were significantly reduced in CAS knockout mutants. Our results suggest that thylakoid membrane-localized CAS is essential for [Ca(2+)](ext)-induced [Ca(2+)](cyt) transients and stomatal closure.     

The role of calcium in ABA-induced gene expression and stomatal movements

There is much interest in the transduction pathways by which abscisic acid (ABA) regulates stomatal movements (ABA-turgor signalling) and by which this phytohormone regulates the pattern of gene expression in plant cells (ABA-nuclear signalling). A number of second messengers have been identified in both the ABA-turgor and ABA-nuclear signalling pathways. A major challenge is to understand the architecture of ABA-signalling pathways and to determine how the ABA signal is coupled to the appropriate response. We have investigated whether separate Ca2+-dependent and -independent ABA-signalling pathways are present in guard cells. Our data suggest that increases in [Ca2+]i are a common component of the guard cell ABA-turgor and ABA-nuclear signalling pathways. The effects of Ca2+ antagonists on ABA-induced stomatal closure and the ABA-responsive CDeT6-19 gene promoter suggest that Ca2+ is involved in both ABA-turgor signalling and ABA-nuclear signalling in guard cells. However, the sensitivity of these pathways to alterations in the external calcium concentration differ, suggesting that the ABA-nuclear and ABA-turgor signalling pathways are not completely convergent. Our data suggest that whilst Ca2+-independent signalling elements are present in the guard cell, they do not form a completely separate Ca2+-independent ABA-signalling pathway.     

Guard cell-specific inhibition of Arabidopsis MPK3 expression causes abnormal stomatal responses to abscisic acid and hydrogen peroxide

MAP kinases have been linked to guard cell signalling. Arabidopsis thaliana MAP Kinase 3 (MPK3) is known to be activated by abscisic acid (ABA) and hydrogen peroxide (H(2)O(2)), which also control stomatal movements. We therefore studied the possible role of MPK3 in guard cell signalling through guard cell-specific antisense inhibition of MPK3 expression. Such transgenic plants contained reduced levels of MPK3 mRNA in the guard cells and displayed partial insensitivity to ABA in inhibition of stomatal opening, but responded normally to this hormone in stomatal closure. However, ABA-induced stomatal closure was reduced compared with controls when cytoplasmic alkalinization was prevented with sodium butyrate. MPK3 antisense plants were less sensitive to exogenous H(2)O(2), both in inhibition of stomatal opening and in promotion of stomatal closure, thus MPK3 is required for the signalling of this compound. ABA-induced H(2)O(2) synthesis was normal in these plants, indicating that MPK3 probably acts in signalling downstream of H(2)O(2). These results provide clear evidence for the important role of MPK3 in the perception of ABA and H(2)O(2) in guard cells.     

Ca2+signalling in stomatal guard cells

Ca(2+) is a ubiquitous second messenger in the signal transduction pathway(s) by which stomatal guard cells respond to external stimuli. Increases in guard-cell cytosolic free Ca(2+) concentration ([Ca(2+)](cyt)) have been observed in response to stimuli that cause both stomatal opening and closure. In addition, several important components of Ca(2+)-based signalling pathways have been identified in guard cells, including the cADP-ribose and phospholipase C/Ins(1, 4,5)P(3)-mediated Ca(2+)-mobilizing pathways. The central role of stimulus-induced increases in [Ca(2+)](cyt) in guard-cell signal transduction has been clearly demonstrated in experiments examining the effects of modulating increases in [Ca(2+)](cyt) on alterations in guard-cell turgor or the activity of ion channels that act as effectors in the guard-cell turgor response. In addition, the paradox that Ca(2+) is involved in the transduction of signals that result in opposite end responses (stomatal opening and closure) might be accounted for by the generation of stimulus-specific Ca(2+) signatures, such that increases in [Ca(2+)](cyt) exhibit unique spatial and temporal characteristics.     

Ethylene mediates UV-B-induced stomatal closure via peroxidase-dependent hydrogen peroxide synthesis in Vicia faba L

Ultraviolet B (UV-B) radiation is an important environmental signal for plant growth and development, but its signal transduction mechanism is unclear. UV-B is known to induce stomatal closure via hydrogen peroxide (H(2)O(2)), and to affect ethylene biosynthesis. As ethylene is also known to induce stomatal closure via H(2)O(2) generation, the possibility of UV-B-induced stomatal closure via ethylene-mediated H(2)O(2) generation was investigated in Vicia faba by epidermal strip bioassay, laser-scanning confocal microscopy, and assays of ethylene production. It was found that H(2)O(2) production in guard cells and subsequent stomatal closure induced by UV-B radiation were inhibited by interfering with ethylene biosynthesis as well as ethylene signalling, suggesting that ethylene is epistatic to UV-B radiation in stomatal movement. Ethylene production preceded H(2)O(2) production upon UV-B radiation, while exogenous ethylene induced H(2)O(2) production in guard cells and subsequent stomatal closure, further supporting the conclusion. Inhibitors for peroxidase but not for NADPH oxidase abolished H(2)O(2) production upon UV-B radiation in guard cells, suggesting that peroxidase is the source of UV-B-induced H(2)O(2) production. Taken together, our results strongly support the idea that ethylene mediates UV-B-induced stomatal closure via peroxidase-dependent H(2)O(2) generation.     

Extracellular calmodulin-induced stomatal closure is mediated by heterotrimeric G protein and H2O2

Extracellular calmodulin (ExtCaM) exerts multiple functions in animals and plants, but the mode of ExtCaM action is not well understood. In this paper, we provide evidence that ExtCaM stimulates a cascade of intracellular signaling events to regulate stomatal movement. Analysis of the changes of cytosolic free Ca2+ ([Ca2+]cyt) and H2O2 in Vicia faba guard cells combined with epidermal strip bioassay suggests that ExtCaM induces an increase in both H2O2 levels and [Ca2+]cyt, leading to a reduction in stomatal aperture. Pharmacological studies implicate heterotrimeric G protein in transmitting the ExtCaM signal, acting upstream of [Ca2+]cyt elevation, and generating H2O2 in guard cell responses. To further test the role of heterotrimeric G protein in ExtCaM signaling in stomatal closure, we checked guard cell responses in the Arabidopsis (Arabidopsis thaliana) Galpha-subunit-null gpa1 mutants and cGalpha overexpression lines. We found that gpa1 mutants were insensitive to ExtCaM stimulation of stomatal closure, whereas cGalpha overexpression enhanced the guard cell response to ExtCaM. Furthermore, gpa1 mutants are impaired in ExtCaM induction of H2O2 generation in guard cells. Taken together, our results strongly suggest that ExtCaM activates an intracellular signaling pathway involving activation of a heterotrimeric G protein, H2O2 generation, and changes in [Ca2+]cyt in the regulation of stomatal movements.     

Involvement of endogenous abscisic acid in methyl jasmonate-induced stomatal closure in Arabidopsis

In this study, we examined the involvement of endogenous abscisic acid (ABA) in methyl jasmonate (MeJA)-induced stomatal closure using an inhibitor of ABA biosynthesis, fluridon (FLU), and an ABA-deficient Arabidopsis (Arabidopsis thaliana) mutant, aba2-2. We found that pretreatment with FLU inhibited MeJA-induced stomatal closure but not ABA-induced stomatal closure in wild-type plants. The aba2-2 mutation impaired MeJA-induced stomatal closure but not ABA-induced stomatal closure. We also investigated the effects of FLU and the aba2-2 mutation on cytosolic free calcium concentration ([Ca(2+)](cyt)) in guard cells using a Ca(2+)-reporter fluorescent protein, Yellow Cameleon 3.6. In wild-type guard cells, FLU inhibited MeJA-induced [Ca(2+)](cyt) elevation but not ABA-induced [Ca(2+)](cyt) elevation. The aba2-2 mutation did not affect ABA-elicited [Ca(2+)](cyt) elevation but suppressed MeJA-induced [Ca(2+)](cyt) elevation. We also tested the effects of the aba2-2 mutation and FLU on the expression of MeJA-inducible VEGETATIVE STORAGE PROTEIN1 (VSP1). In the aba2-2 mutant, MeJA did not induce VSP1 expression. In wild-type leaves, FLU inhibited MeJA-induced VSP1 expression. Pretreatment with ABA at 0.1 μm, which is not enough concentration to evoke ABA responses in the wild type, rescued the observed phenotypes of the aba2-2 mutant. Finally, we found that in wild-type leaves, MeJA stimulates the expression of 9-CIS-EPOXYCAROTENOID DIOXYGENASE3, which encodes a crucial enzyme in ABA biosynthesis. These results suggest that endogenous ABA could be involved in MeJA signal transduction and lead to stomatal closure in Arabidopsis guard cells.     

Cytoplasmic alkalization precedes reactive oxygen species production during methyl jasmonate- and abscisic acid-induced stomatal closure

Signaling events during abscisic acid (ABA) or methyl jasmonate (MJ)-induced stomatal closure were examined in Arabidopsis wild type, ABA-insensitive (ost1-2), and MJ-insensitive mutants (jar1-1) in order to examine a crosstalk between ABA and MJ signal transduction. Some of the experiments were performed on epidermal strips of Pisum sativum. Stomata of jar1-1 mutant plants are insensitive to MJ but are able to close in response to ABA. However, their sensitivity to ABA is less than that of wild-type plants. Reciprocally, the stomata of ost1-2 are insensitive to ABA but are able to close in response to MJ to a lesser extent compared to wild-type plants. Both MJ and ABA promote H(2)O(2) production in wild-type guard cells, while exogenous application of diphenylene iodonium (DPI) chloride, an inhibitor of NAD(P)H oxidases, results in the suppression of ABA- and MJ-induced stomatal closure. ABA elevates H(2)O(2) production in wild-type and jar1-1 guard cells but not in ost1-2, whereas MJ induces H(2)O(2) production in both wild-type and ost1-2 guard cells, but not in jar1-1. MJ-induced stomatal closing is suppressed in the NAD(P)H oxidase double mutant atrbohD/F and in the outward potassium channel mutant gork1. Furthermore, MJ induces alkalization in guard cell cytosol, and MJ-induced stomatal closing is inhibited by butyrate. Analyses of the kinetics of cytosolic pH changes and reactive oxygen species (ROS) production show that the alkalization of cytoplasm precedes ROS production during the stomatal response to both ABA and MJ. Our results further indicate that JAR1, as OST1, functions upstream of ROS produced by NAD(P)H oxidases and that the cytoplasmic alkalization precedes ROS production during MJ or ABA signal transduction in guard cells.     

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.     

星型孢菌素(STS)对蚕豆气孔运动的调控效应

用激光扫描共聚焦显微技术,初步研究广谱性蛋白激酶抑制剂星型孢菌素(STS)对蚕豆气孔运动的调控效应.结果表明:(1)光下STS对气孔开度无影响但暗中显著促进气孔开放,表明蛋白激酶参与光/暗对气孔运动的调控,光下蛋白激酶活性低而暗中高;(2)与H2O2清除剂抗坏血酸(ASA)和NO清除剂羧基-2-苯-4,4,5,5-四甲基咪唑-1-氧-3-氧化物(cPTIO)一样,STS既降低暗处理和光下外源H2O2、硝普钠(SNP)处理保卫细胞H2O2、NO水平,也促进气孔开放,表明暗中蛋白激酶通过抑制H2O2、NO清除机制提高保卫细胞内源H2O2、NO水平并促进气孔关闭.