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Protective effect of quercetin against acetaldehyde was evaluated using the cultured hepatocyte models with aldehyde dehydrogenase (ALDH) isozyme deficiency (aldh2-kdand aldh1a1-kd). The quercetin-induced cytoprotection against acetaldehyde in the ALDH1A1-deficient mutant (aldh1a1-kd) was weaker than that in the wild type. Furthermore, quercetin did not enhance the ALDH activity in aldh1a1-kdcells, suggesting that ALDH1A1 is involved in quercetin-induced cytoprotection.

Chitosan (CHT) is a deacylated derivative of chitin and improves growth and yield performance, activates defensive genes, and also induces stomatal closure in plants. Glutathione (GSH) has significant functions in the growth, development, defense systems, signaling, and gene expression. GSH negatively regulates abscisic acid-, methyl jasmonate-, and salicylic acid-induced stomatal closure. However, the negative regulation by GSH of CHT-induced stomatal closure is still unknown. Regulation of CHT-induced stomatal closure by GSH in guard cells was investigated using two GSH-deficient mutants, cad2-1and chlorina 1-1(ch1-1), and a GSH-decreasing chemical, 1-chloro-2,4-dinitrobenzene (CDNB). The cad2-1and ch1-1mutations and CDNB treatment enhanced CHT-induced stomatal closure. Treatment with glutathione monoethyl ester restored the GSH level in the guard cells of cad2-1and ch1-1and complemented the stomatal phenotype of the mutants. These results indicate that GSH negatively regulates CHT-induced stomatal closure in Arabidopsis thaliana.Graphical AbstractNegative regulation of chitosan-induced stomatal closure by glutathione in Arabidopsis thaliana

Dihydroxyacetone (DHA) occurs in wide-ranging organisms, including plants, and can undergo spontaneous conversion to methylglyoxal (MG). While the toxicity of MG to plants is well-known, the toxicity of DHA to plants remains to be elucidated. We investigated the effects of DHA and MG on Arabidopsis. Exogenous DHA at up to 10 mmdid not affect the radicle emergence, the expansion of green cotyledons, the seedling growth, or the activity of glyoxalase II, while DHA at 10 mminhibited the root elongation and increased the activity of glyoxalase I. Exogenous MG at 1.0 mminhibited these physiological responses and increased both activities. Dihydroxyacetone at 10 mmincreased the MG content in the roots. These results indicate that DHA is not so toxic as MG in Arabidopsis seeds and seedlings and suggest that the toxic effect of DHA at high concentrations is attributed to MG accumulation by the conversion to MG.Graphical AbstractIs dihydroxyacetone toxic in Arabidopsis?

The objective of the current study was to examine the potential ameliorating effect of exogenous melatonin (MT) on cadmium (Cd)-mediated injury in chickpea seedlings and to optimize the MT application approach. To mitigate Cd phytotoxicity, exogenous MT (10 μM) was added to the germination medium of chickpea (Cicer arietinumL.) seeds contaminated with 200 μM CdCl2following two experimental approaches. The first set of seeds was treated simultaneously with Cd and MT at the start of the germination, while the second set was exposed to Cd stress for 3 days before being treated with a combination of Cd and MT. The current results revealed that exogenous MT significantly mitigated the deleterious effect of Cd on seedling growth in terms of root and shoot dry weight. Besides, MT alleviated the Cd-imposed disruption of cellular redox homeostasis. This effect was manifested by reduced cell death and hydrogen peroxide content. Moreover, MT may protect cell membrane integrity by lowering lipoxygenase activity and downregulating its gene expression. Melatonin ameliorated the Cd-induced oxidative stress by promoting key antioxidative enzymes, including ascorbate peroxidase, catalase, and Cu/Zn-superoxide dismutase. This stimulating effect was accompanied by the upregulation of related gene expressions. In contrast, MT downregulated glutathione peroxidase activity and its corresponding gene expression. Seedlings exposed to exogenous MT simultaneously with Cd showed more pronounced beneficial effects than those receiving MT as a late supplementation. Overall, the current results state that exogenous MT, when added simultaneously with the metal, is efficient at enhancing chickpea tolerance to Cd contamination. This favorable effect is mostly mediated by the improvement of antioxidant activities and gene expression.

Crop production is continuously threatened by various environmental stresses. Modern and efficient tactics are required to boost agricultural output beyond facing stresses. Recently, many studies reported that nanotechnology can enhance plant growth and development under stress and non-stress conditions, contributing to agricultural sustainability. Seed priming with nanoparticles (NPs) is a modern and effective approach that increases germination, plant growth progression, productivity, and postharvest physiology of plants by regulating morphological and physio-biochemical characteristics. Different plant studies showed that seed priming with NPs enhances germination, improves nutrient uptake, regulates antioxidant defense, and reduces oxidative damage under stress and non-stress conditions. Recently, several reviews on the regulatory role of nanotechnology on plant growth progressions have been published. However, the regulatory roles of nano-seed priming have not been reviewed adequately and systematically. The present review assembles the current literature on nano-priming and discusses the potentiality of nano-priming in the growth progression of plants under stress and normal conditions and future directions for sustainable agriculture.

The objective of the present study was to elucidate the mechanism by which oxalic acid (OA) alleviates cadmium (Cd) stress. Chickpea (Cicer arietinumL.) seeds were treated with 200 µM CdCl2for 6 days or 3 days followed by the combination 200 µM Cd + 100 µM OA for three additional days. Exogenous OA mitigated the growth inhibition by Cd of both roots and shoots. This positive effect can be attributed to the increased OA exudation from roots and the alleviation of the Cd-induced depletion of endogenous OA in shoots (80% increase versus Cd-stressed). The combination Cd + OA proved to be effective in protecting cell membrane integrity. This beneficial effect was reflected by 36 and 24% decrease in lipoxygenase (LOX) activity in roots and shoots, respectively, and 60% decrease in the accumulation of the harmful aldehyde, 4-hydroxy-2-nonenal (4-HNE) in roots when compared to Cd-treated samples. Besides, OA restored the Cd-imposed disruption of the plasma membrane function. This effect was depicted by an optimal H+-ATPase activity and proton exudation rate. Oxalic acid counteracted the Cd-induced overproduction of hydroxyl radical (OH•) and NADPH-oxidase activity increase, leading to restore a steady cellular redox state. Furthermore, OA modulated the impact of Cd on Cu/Zn-superoxide dismutase (Cu/Zn-SOD), ascorbate peroxidase (APX), and catalase (CAT) activities in chickpea seedlings. Present results indicate that OA is able to alleviate Cd toxicity by protecting plasma membrane integrity and modulating antioxidant activities. Moreover, our findings shed light on the interplay between plasma membrane H+-ATPase and the accumulation and root exudation of OA.

Arsenic is toxic for plants. Our previous results showed that the application of proline enhanced the sensitivity of tobacco BY-2 cells to arsenate. In order to clarify the enhancement mechanism, we investigated the effects of other amino acids on the arsenate-stressed BY-2 cells. Glutamate at up to 10 m mdid not affect the cell growth in the absence or presence of arsenate. Arginine at up to 10 m mdid not affect the growth in the absence of arsenate but arginine at 10 m menhanced the inhibition of the cell growth by arsenate. Alanine at up to 10 m mdid not affect the cell growth under nonstressed condition but alanine at 10 m msignificantly improved the cell growth under arsenate stress. These results suggest that alanine mitigates arsenate stress in BY-2 cells and that arginine like proline enhances the sensitivity of BY-2 cells to arsenate.Graphical AbstractA hypothetical flow diagram of arsenate-inhibited catabolic process of P5C-based amino acids.

Cytosolic calcium ([Ca2+]cyt) elevation activates plasma membrane anion channels in guard cells, which is required for stomatal closure. However, involvement of the anion channels in the [Ca2+]cytelevation remains unclear. We investigated the involvement using Arabidopsis thalianaanion channel mutants, slac1-4 slah3-3and slac1-4 almt12-1. Extracellular calcium induced stomatal closure in the wild-type plants but not in the anion channel mutant plants whereas extracellular calcium induced [Ca2+]cytelevation both in the wild-type guard cells and in the mutant guard cells. The peak height and the number of the [Ca2+]cytspike were lower and larger in the slac1-4 slah3-3than in the wild type and the height and the number in the slac1-4 almt12-1were much lower and much larger than in the wild type. These results suggest that the anion channels are involved in the regulation of [Ca2+]cytelevation in guard cells.Graphical AbstractIn guard cells, anion channels regulate the height and number of cytosolic calcium spikes elicited by extracellular calcium.

The purpose of this study is to compare the potentials to exhibit biologically active antioxidant actions between white rice (WR) and brown rice (BR) in in vitroassays and a cellular model. The Trolox equivalent (TE) per 1 mg ethanol extract of WR for the 1,1-diphenyl-2-picrylhydrazyl assay was slightly higher than that of BR, whereas the TE per 1 g whole WR was much lower than that for BR. This tendency was very comparable to those for the oxygen radical absorbance capacity and total polyphenol content. Both of the ethanol extracts also similarly suppressed the hydrogen peroxide-induced cytotoxicity and enhanced the gene expression of drug-metabolizing enzymes. Based on the α-tocopherol quantity, its contribution to the cytoprotective effect of the rice extracts is very limited. Taken together, the ethanol extract of WR might be a qualitatively, but not quantitatively, equivalent source of antioxidative phytochemicals to that of BR.Graphical AbstractEthanol extracts of white rice and brown rice showed the equivalent antioxidative potentials not only in the in vitroassays but also the cellular assay.

ABSTRACTSelenium (Se) causes oxidative damage to plants. Proline is accumulated as a compatible solute in plants under stress conditions and mitigates stresses. Selenate at 250 µM increased cell death and inhibited the growth of tobacco BY-2 cells while exogenous proline at 10 mM did not mitigate the inhibition by selenate. Selenate increased accumulation of Se and ROS and activities of antioxidant enzymes but not lipid peroxidation in the BY-2 cells. Proline increased Se accumulation and antioxidant enzyme activities but not either ROS accumulation or lipid peroxidation in the selenate-stressed cells. Glutathione (GSH) rather than ascorbic acid (AsA) mitigated the growth inhibition although both reduced the accumulation of ROS induced by selenate. These results indicate that proline increases both antioxidant enzyme activities and Se accumulation, which overall fails to ameliorate the growth inhibition by selenate and that the growth inhibition is not accounted for only by ROS accumulation.Abbreviations:APX: ascorbate peroxidase; AsA: ascorbic acid; BY-2: Bright Yellow-2; CAT: catalase; DAI: days after inoculation; DW: dry weight; FW: fresh weight; GSH: glutathione; ROS: reactive oxygen species

ABSTRACTReactive oxygen species and nitric oxide (NO•) concomitantly play essential roles in guard cell signaling. Studies using catalase mutants have revealed that the inducible and constitutive elevations of intracellular hydrogen peroxide (H2O2) have different roles: only the inducible H2O2production transduces the abscisic acid (ABA) signal leading stomatal closure. However, the involvement of inducible or constitutive NO• productions, if exists, in this process remains unknown. We studied H2O2and NO• mobilization in guard cells of catalase mutants. Constitutive H2O2level was higher in the mutants than that in wild type, but constitutive NO• level was not different among lines. Induced NO• and H2O2levels elicited by ABA showed a high correlation with each other in all lines. Furthermore, NO• levels increased by exogenous H2O2also showed a high correlation with stomatal aperture size. Our results demonstrate that ABA-induced intracellular H2O2accumulation triggers NO• production leading stomatal closure.AbbreviationsABA: abscisic acid; CAT: catalase; cGMP: cyclic guanosine monophosphate; DAF-2DA: 4,5-diaminofluorescein-2 diacetate; H2DCF-DA: 2ʹ,7ʹ-dichlorodihydrofluorescein diacetate; MeJA: methyljasmonate; NOS: nitric oxide synthetase; NR: nitrate reductase; POX: peroxidase; ROS: reactive oxygen species; SNAP: S-nitroso-N-acetyl-DL-penicillamine; SNP: sodium nitroprusside; NOX: NADP(H) oxidase.

ABSTRACTChitosan (CHT) induces stomatal closure and thus plays a crucial role in plants to adapt to the adverse environments. Our previous results of a SA-deficient mutant nahGsuggest that endogenous salicylic acid (SA) is involved in the CHT signaling in guard cells. Here in order to make the involvement definite, we examined stomatal responses to CHT of another SA-deficient mutant, sid2, and an SA receptor mutant, npr1-3. The sid2mutation impaired CHT-induced stomatal closure and reactive oxygen species production and both impairments were complemented with exogenous SA application. Moreover, the CHT-induced stomatal closure is disrupted in the npr1-3mutant. These results suggest that endogenous SA is involved in the CHT-induced stomatal closure viathe SA receptor, NPR1.AbbreviationsSA: salicylic acid; ABA: abscisic acid; ROS: reactive oxygen species; NPR1: nonexpresser of pathogenesis-related genes1; CHT: chitosan; DAB: 3,3′-diaminobenzidine

•Salt stress significantly decreased maize seed germination and seedling growth.•Stomatal size and K+/Na+ratios were significantly decreased under salt stress.•Under salt stress, MDA and H2O2increased, whereas antioxidant enzymes decreased.•Proline and glycine-betaine increased germination, stomatal size, and K+/Na+ratios.•Proline and glycine-betaine reduced salt-induced H2O2and MDA by boosting antioxidants.

ABSTRACTMethyl-β-cyclodextrin (MβCD) is an effective agent for the removal of plasma membrane cholesterol. In this study, we investigated the modulating effects of MβCD on the antiproliferation induced by benzyl isothiocyanate (BITC), an ITC compound mainly derived from papaya seeds. We confirmed that MβCD dose-dependently increased the cholesterol level in the medium, possibly through its removal from the plasma membrane of human colorectal cancer cells. The pretreatment with a non-toxic concentration (2.5 mM) of MβCD significantly enhanced the BITC-induced cytotoxicity and apoptosis induction, which was counteracted by the cholesterol supplementation. Although BITC activated the phosphoinositide 3-kinase (PI3K)/Akt pathway, MβCD dose-dependently inhibited the phosphorylation level of Akt. On the contrary, the treatment of MβCD enhanced the phosphorylation of mitogen activated protein kinases, but did not potentiate their BITC-induced phosphorylation. These results suggested that MβCD might potentiate the BITC-induced anti-cancer by cholesterol depletion and thus inhibition of the PI3K/Akt-dependent survival pathway.Abbreviations: CDs: cyclodextrins; MβCD: methyl-β-cyclodextrin; ITCs: isothiocyanates; BITC: benzyl isothiocyanate; PI3K: phosphoinositide 3-kinase; PDK1: phosphoinositide-dependent kinase-1; MAPK: mitogen activated protein kinase; ERK1/2: extracellular signal-regulated kinase1/2; JNK: c-Jun N-terminal kinase; PI: propidium iodide; FBS: fatal bovine serum; TLC: thin-layer chromatography; PBS(-): phosphate-buffered saline without calcium and magnesium; MEK: MAPK/ERK kinase; PIP2: phosphatidylinositol-4,5-bisphosphate; PIP3: phosphatidylinositol-3,4,5-trisphosphate

ABSTRACTBenzyl isothiocyanate (BITC) is an organosulfur compound derived from cruciferous vegetables and papaya seeds. In this study, we investigated the effect of BITC on the lipid accumulation in 3T3-L1 preadipocytes during adipocyte differentiation. The treatment of BITC during the differentiation-inducing stage significantly ameliorated the lipid accumulation, whereas it had no inhibitory effect during the differentiation-maintaining stage. BITC also significantly suppressed the mRNA expression of the adipocyte-specific markers, such as CCAAT/enhancer-binding protein α (C/EBPα), C/EBPβ, C/EBPδ and peroxisome proliferator-activated receptor γ. BITC significantly inhibited the phosphorylation of extracellular signal-regulated kinase phosphorylation, whereas it enhanced that of AMP-activated protein kinase. Furthermore, BITC significantly suppressed the intracellular 2-deoxyglucose uptake as well as glucose transporter 4 expression. These results suggest that inhibition of the adipocyte differentiation and glucose uptake may mainly contribute to the inhibitory effect of BITC on the lipid accumulation in 3T3-L1 preadipocytes.Abbreviations:PPARγ: peroxisome proliferator-activated receptor γ; CEBP: CCAAT/enhancer-binding protein; GLUT4: glucose transporter 4; AMPK: AMP-activated protein kinase; ERK1/2: extracellular signal-regulated kinase 1/2; MAPK: a mitogen-activated protein kinase; ITCs: isothiocyanates; BITC: benzyl isothiocyanate; FBS: fetal bovine serum; CS: calf serum; AITC: allyl ITC; IBMX: 3-isobutyl-1-methylxanthine; LDH: lactate dehydrogenase; KRH: Krebs-Ringer-Hepes-bicarbonate; 2-DG: 2-deoxy-d-glucose

ABSTRACTLycii Fructus is the dried ripe fruits of Lycium chinenseand L. barbarum, which has long been used as a traditional food material in East Asia. The purpose of this study was to investigate the role of the indirect antioxidative action in the Lycii fructus extract (LFE)-induced cytoprotective effect in vitro. LFE significantly enhanced the expression of the drug-metabolizing enzyme genes and intracellular glutathione level in mouse hepatoma Hepa1c1c7 cells. LFE stimulated the nuclear translocation of aryl hydrocarbon receptor as well as nuclear factor (erythroid-derived 2)-like 2. The pretreatment of LFE for 24 h, but not for 30 min, completely inhibited the cytotoxic effect of hydrogen peroxide. Furthermore, chlorogenic acid, one of the main constituents of LFE, showed cytoprotection against hydrogen peroxide with the enhanced phase 2 enzyme gene expression. These results suggested that LFE exhibits a cytoprotective effect, possibly through the enhancement of the antioxidant gene expression.abbreviations: LFE: Lycii Fructus extract; GSH: glutathione; NQO1: NAD(P)H:quinone oxidoreductase 1; HO-1: heme oxygenase-1; GCLC: glutamate-cysteine ligase, catalytic subunit; xCT: a component of cysteine/glutamate antiporter (cystine/glutamate exchanger); CYP1A1: cytochrome P450 1A1; GSH: glutathione; AhR: aryl hydrocarbon receptor; Nrf2: nuclear factor (erythroid-derived 2)-like 2; CGA: chlorogenic acid; RT-PCR: reverse transcription-polymerase chain reaction; DTT: dithiothreitol; PMSF: phenylmethylsulfonyl fluoride; ARE: antioxidant response element; XRE: xenobiotic responsive element.

The regulating role of phosphatidylinositide 3-kinase (PI3K) in benzyl isothiocyanate (BITC)-induced Nrf2 activation, contributing to the inducible expression of cytoprotective genes, was investigated. BITC significantly enhanced the accumulation of Nrf2 as well as autophagic molecules in human colorectal cancer HCT-116 cells. Experiments using a PI3K-specific inhibitor suggested that PI3K plays the key role in the non-canonical Nrf2 activation by BITC.

3,4-Dihydroxyphenylacetic acid (DOPAC) is one of the major colonic microflora-produced catabolites of quercetin glycosides, such as quercetin 4′-glucoside derived from onion. Here, we investigated whether DOPAC modulates the aldehyde dehydrogenase (ALDH) activity and protects the cells from the acetaldehyde-induced cytotoxicity in vitro. DOPAC was shown to enhance not only the total ALDH activity, but also the gene expression of ALDH1A1, ALDH2 and ALDH3A1 in a concentration-dependent manner. DOPAC simultaneously stimulated the nuclear translocation of NFE2-related factor 2 and aryl hydrocarbon receptor. The pretreatment of DOPAC completely protected the cells from the acetaldehyde-induced cytotoxicity. The present study suggested that DOPAC acts as a potential ALDH inducer to prevent the alcohol-induced abnormal reaction.

Arsenic causes physiological and structural disorders in plants. Proline is accumulated as a compatible solute in plants under various stress conditions and mitigates stresses. Here, we investigated the effects of exogenous proline on tobacco Bright Yellow-2 (BY-2) cultured cells under stress. Arsenate did not inhibit BY-2 cell growth at 40 and 50 μM but did it at 60 μM. Proline at 0.5 to 10 mM did not affect the cell growth but delayed it at 20 mM. At 40 μM , neither 0.5 mM nor 1 mM proline affected the cell growth but 10 mM proline inhibited it. In the presence of , 10 mM proline increased the number of Evans Blue-stained (dead) cells and decreased the number of total cells. Together, our results suggest that exogenous proline does not alleviate arsenate toxicity but enhances the sensitivity of BY-2 cells to arsenate.

An elicitor chitosan (CHT) induces stomatal closure but the mechanism remains to be clarified. A phytohormone salicylic acid (SA) is crucial for elicitor-induced defense signaling in plants. Here we investigated whether endogenous SA is required for CHT signaling in guard cells. In the SA-deficient nahGmutant, treatment of CHT did not induce either apoplastic reactive oxygen species (ROS) production or stomatal closure but co-treatment of CHT and SA induced both apoplastic ROS production and stomatal closure, indicating the involvement of endogenous SA in CHT-induced apoplastic ROS production and CHT-induced stomatal closure. Furthermore, CHT induced transient cytosolic free calcium concentration increments in the nahGmutant in the presence of exogenous SA but not in the absence of exogenous SA. These results provide evidence that endogenous SA is a crucial element in CHT-induced stomatal closure.

Salicylic acid (SA) induces stomatal closure sharing several components with abscisic acid (ABA) and methyl jasmonate (MeJA) signaling. We have previously shown that two guard cell-preferential mitogen-activated protein kinases (MAPKs), MPK9 and MPK12, positively regulate ABA signaling and MeJA signaling in Arabidopsis thaliana. In this study, we examined whether these two MAPKs are involved in SA-induced stomatal closure using genetic mutants and a pharmacological, MAPKK inhibitor. Salicylic acid induced stomatal closure in mpk9and mpk12single mutants but not in mpk9 mpk12double mutants. The MAPKK inhibitor PD98059 inhibited SA-induced stomatal closure in wild-type plants. Salicylic acid induced extracellular reactive oxygen species (ROS) production, intracellular ROS accumulation, and cytosolic alkalization in the mpk9, mpk12, and mpk9 mpk12mutants. Moreover, SA-activated S-type anion channels in guard cells of wild-type plants but not in guard cells of mpk9 mpk12double mutants. These results imply that MPK9 and MPK12 are positive regulators of SA signaling in Arabidopsis guard cells.

Plant glutamate receptor homologs (GLRs) have long been proposed to function as ligand-gated Ca2+channels, but no in planta evidence has been provided. Here, we present genetic evidence that ArabidopsisGLR3.1 and GLR3.5 form Ca2+channels activated by L-methionine (L-Met) at physiological concentrations and regulate stomatal apertures and plant growth. The glr3.1/3.5mutations resulted in a lower cytosolic Ca2+level, defective Ca2+-induced stomatal closure, and Ca2+-deficient growth disorder, all of which involved L-Met. Patch-clamp analyses of guard cells showed that GLR3.1/3.5 Ca2+channels are activated specifically by L-Met, with the activation abolished in glr3.1/3.5. Moreover, GLR3.1/3.5 Ca2+channels are distinct from previously characterized ROS-activated Ca2+channels and act upstream of ROS, providing Ca2+transients necessary for the activation of NADPH oxidases. Our data indicate that GLR3.1/3.5 constitute L-Met-activated Ca2+channels responsible for maintaining basal [Ca2+]cyt, play a pivotal role in plant growth, and act upstream of ROS, thereby regulating stomatal aperture.

•Salinity and waterlogging (S-WL) retarded growth strongly than S or WL stress•Photosynthesis and ionic homeostasis are more susceptible to S-WL stress•Tolerance to S-WL stress is mostly determined by salinity tolerance•Halophytes showed better performance than hydrophytes under S-WL stress•There has been minimal study on C4 plants subjected to S-WL stress

3,4-Dihydroxyphenylacetic acid (DOPAC) is one of the colonic microflora-produced catabolites of quercetin 4′-glucoside (Q4′G). Although the interaction of DOPAC with cellular proteins might be involved in its biological activity, the actual proteins have not yet been identified. In this study, we developed a novel tag-free DOPAC probe to label the targeted proteins by the copper(I)-catalyzed azide alkyne cycloaddition (CuAAC) and verified its efficacy. Various labeled proteins were detected by the DOPAC probe with the azide labeled biotin and a horseradish peroxidase (HRP)-streptavidin complex. Furthermore, a pulldown assay identified Keap1 and aryl hydrocarbon receptor (AhR) as the target proteins for the phase 2 enzyme up-regulation.

Isothiocyanates are enzymatically produced from glucosinolates in plants, and allyl isothiocyanate (AITC) induces stomatal closure in Arabidopsis thaliana. In this study, we investigated stomatal responses to AITC in Vicia faba. AITC-induced stomatal closure accompanied by reactive oxygen species (ROS) and NO production, cytosolic alkalization and glutathione (GSH) depletion in V. faba. GSH monoethyl ester induced stomatal reopening and suppressed AITC-induced GSH depletion in guard cells. Exogenous catalase and a peroxidase inhibitor, salicylhydroxamic acid, inhibited AITC-induced stomatal closure, unlike an NAD(P)H oxidase inhibitor, diphenylene iodonium chloride. The peroxidase inhibitor also abolished the AITC-induced ROS production, NO production, and cytosolic alkalization. AITC-induced stomatal closure was suppressed by an NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, and an agent to acidify cytosol, butyrate. These results indicate that AITC-induced stomatal closure in V. fabaas well as in A. thalianaand suggest that AITC signaling in guard cells is conserved in both plants.

An allergen-stimulating cytokine, interleukin-13 (IL-13), plays a significant role in allergic inflammation. Benzyl isothiocyanate (BITC), derived from several cruciferous vegetables, significantly suppressed the IL-13 expression in the calcium ionophore-stimulated human basophilic KU812 cells. Down-regulation of phosphorylated mitogen-activated protein kinases as well as nuclear transcriptional factors might be involved in the underlying mechanism.

Acrolein is a reactive α,β-unsaturated aldehyde derived from lipid peroxides, which are produced in plants under a variety of stress. We investigated effects of acrolein on light-induced stomatal opening using Arabidopsis thaliana. Acrolein inhibited light-induced stomatal opening in a dose-dependent manner. Acrolein at 100 μM inhibited plasma membrane inward-rectifying potassium (Kin) channels in guard cells. Acrolein at 100 μM inhibited Kinchannel KAT1 expressed in a heterologous system using Xenopus leavesoocytes. These results suggest that acrolein inhibits light-induced stomatal opening through inhibition of Kinchannels in guard cells.