Hydrogen sulphide suppresses human atrial fibroblast proliferation and transformation to myofibroblasts

Cardiac fibroblasts are crucial in pathophysiology of the myocardium whereby their aberrant proliferation has significant impact on cardiac function. Hydrogen sulphide (H₂S) is a gaseous modulator of potassium channels on cardiomyocytes and has been reported to attenuate cardiac fibrosis. Yet, the mechanism of H₂S in modulating proliferation of cardiac fibroblasts remains poorly understood. We hypothesized that H₂S inhibits proliferative response of atrial fibroblasts through modulation of potassium channels. Biophysical property of potassium channels in human atrial fibroblasts was examined by whole‐cell patch clamp technique and their cellular proliferation in response to H₂S was assessed by BrdU assay. Large conductance Ca²⁺‐activated K⁺ current (BK_Ca), transient outward K⁺ current (I_to) and inwardly rectifying K⁺ current (IK_ir) were found in human atrial fibroblasts. Current density of BK_Ca (IC₅₀ = 69.4 μM; n = 6), I_to (IC₅₀ = 55.1 μM; n = 6) and IK_ir (IC₅₀ = 78.9 μM; n = 6) was significantly decreased (P < 0.05) by acute exposure to NaHS (a H₂S donor) in atrial fibroblasts. Furthermore, NaHS (100–500 μM) inhibited fibroblast proliferation induced by transforming growth factor‐β1 (TGF‐β1; 1 ng/ml), Ang II (100 nM) or 20% FBS. Pre‐conditioning of fibroblasts with NaHS decreased basal expression of Kv4.3 (encode I_to), but not KCa1.1 (encode BK_Ca) and Kir2.1 (encode IK_ir). Furthermore, H₂S significantly attenuated TGF‐β1–stimulated Kv4.3 and α‐smooth muscle actin expression, which coincided with its inhibition of TGF‐β–induced myofibroblast transformation. Our results show that H₂S attenuates atrial fibroblast proliferation via suppression of K⁺ channel activity and moderates their differentiation towards myofibroblasts.     

Effect of Hydrogen Sulfide on Cyclic AMP Production in Isolated Bovine and Porcine Neural Retinae

Hydrogen sulfide (H₂S) has been reported to exert pharmacological effects on neural and non-neural tissues from several mammalian species. In the present study, we examined the role of the intracellular messenger, cyclic AMP in retinal response to H₂S donors, sodium hydrosulfide (NaHS) and sodium sulfide (Na₂S) in cows and pigs. Isolated bovine and porcine neural retinae were incubated in oxygenated Krebs buffer solution prior to exposure to varying concentrations of NaHS, Na₂S or the diterpene activator of adenylate cyclase, forskolin. After incubation at different time intervals, tissue homogenates were prepared for cyclic AMP assay using a well established methodology. In isolated bovine and porcine retinae, the combination of both phosphodiesterase inhibitor, IBMX (2 mM) and forskolin (10 μM) produced a synergistic increase (P < 0.001) in cyclic AMP concentrations over basal levels. NaHS (10 nM–100 μM) produced a time-dependent increase in cyclic AMP concentrations over basal levels which reached a maximum at 20 min in both bovine and porcine retinae. At this time point, both NaHS and Na₂S (10 nM–100 μM) caused a significant (P < 0.05) dose-dependent increase in cyclic AMP levels in bovine and porcine retinae. For instance, NaHS (100 nM) elicited a four-fold and three-fold increase in cyclic AMP concentrations in bovine and porcine retinae respectively whilst higher concentrations of Na₂S (100 μM) produced a much lesser effect in both species. In bovine and porcine retinae, the effects caused by forskolin (10 μM) on cyclic AMP production were not potentiated by addition of low or high concentrations of both NaHS and Na₂S. We conclude that H₂S donors can increase cyclic AMP production in isolated neural retinae from cows and pigs. Bovine retina appears to be more sensitive to the stimulatory effect of H₂S donors on cyclic nucleotide production than its porcine counterpart indicating that species differences exist in the magnitude of this response. Furthermore, effects produced by forskolin on cyclic AMP formation were not additive with those elicited by H₂S donors suggesting that these agents may share a common mechanism in their action on the adenylyl cyclase pathway.     

Hydrogen Sulfide Selectively Inhibits γ-Secretase Activity and Decreases Mitochondrial Aβ Production in Neurons from APP/PS1 Transgenic Mice

Hydrogen sulfide (H₂S) is now considered to be a gasotransmitter and may be involved in the pathological process of Alzheimer’s disease (AD). A majority of APP is associated with mitochondria and is a substrate for the mitochondrial γ-secretase. The mitochondria-associated APP metabolism where APP intracellular domains (AICD) and Aβ are generated locally and may contribute to mitochondrial dysfunction in AD. Here, we aimed to investigate the ability of H₂S to mediate APP processing in mitochondria and assessed the possible mechanisms underlying H₂S-mediated AD development. We treated neurons from APP/PS1 transgenic mice with a range of sodium hydrosulfide (NaHS) concentrations. NaHS attenuated APP processing and decreased Aβ production in mitochondria. Meanwhile, NaHS did not changed BACE-1 and ADAM10 (a disintegrin and metalloprotease 10) protein levels, but NaHS (30 μM) significantly increased the levels of presenilin 1(PS1), PEN-2, and NCT, as well as improved the γ-secretase activity, while NaHS (50 μM) exhibits the opposing effects. Furthermore, the intracellular ATP and the COX IV activity of APP/PS1 neurons were increased after 30 μM NaHS treatment, while the ROS level was decreased and the MMP was stabilized. The effect of NaHS differs from DAPT (a non-selective γ-secretase inhibitor), and it selectively inhibited γ-secretase in vitro, without interacting with Notch and modulating its cleavage. The results indicated that NaHS decreases Aβ accumulation in mitochondria by selectively inhibiting γ-secretase. Thus, we provide a mechanistic view of NaHS is a potential anti-AD drug candidate and it may decrease Aβ deposition in mitochondria by selectively inhibiting γ-secretase activity and therefore protecting the mitochondrial function during AD conditions.

     

Endogenous production of hydrogen sulfide in isolated bovine eye

Hydrogen sulfide (H₂S) is a novel gasotransmitter with physiological and pathological functions in vascular homeostasis, cardiovascular system and central nervous system. In the present study, we determined the endogenous levels of H₂S in various tissues of the bovine eye. We also examined the basal levels of H₂S in response to donors (sodium hydrosulfide, NaHS and sodium sulfide, Na₂S), substrate (l-cysteine), inhibitors (propargylglycine, PAG and aminooxyacetic acid, AOA) and activator (S-adenosyl-l-methionine, SAM) of this gas in the bovine retina. H₂S was measured using a well established spectrophotometric method. The highest concentration of endogenous H₂S was detected in cornea (19 ± 2.85 nmoles/mg protein, n = 6) and retina (17 ± 2.1 nmoles/mg protein, n = 6). Interestingly, H₂S was not present in vitreous humor. The inhibitors of CSE and CBS; PAG (1 mM) and AOA (1 mM), significantly attenuated the production of H₂S in the bovine retina by 56.8 and 42%, respectively. On the other hand the activator of CBS; SAM (100 μM), H₂S donors; NaHS (1 μM) and Na₂S (100 μM), significantly increased endogenous levels of H₂S in bovine retina. l-cysteine (10–300 μM) produced a significant (P < 0.05) concentration-dependent increase in H₂S levels reaching a maximal at 300 μM. We conclude that H₂S is endogenously produced in various tissues of the isolated bovine eye. Moreover, endogenous levels of H₂S are enhanced in the presence of substrate (l-cysteine), an activator of CBS (SAM) and H₂S donors but are blocked by inhibitors of enzymes that synthesize this gas in neural retina.     

Changes in Abscisic Acid During Leaf Yellowing of Cut Stock Flowers

Leaf pigments, such as chlorophyll and carotenoids, are essential plant molecules. They provide carbohydrates and energy during all plant life. Leaf pigments are also important parameters of decorative plants, such as floriculture items, cut foliage and flowers. Leaf yellowing is a form of senescence caused by an internal hormone imbalance, such as a lack of cytokinins. The aim of this study was to investigate the changes in total carotenoids and endogenous ABA in cut flower stock leaves during post-harvest life. The effect of pulse treatment with 5 or 10 M thidiazuron (TDZ), 150 mg l^–1 8-hydroxyquinoline sulphate (8-HQS) and combinations of TDZ with 8-HQS on total carotenoids and ABA concentration was also investigated. Results showed that total carotenoids drastically decreased from 1548 g cm^–2, until reaching 565 g cm_–2 at the end of vase life. Endogenous ABA strongly increased at the same time, going from 167 ng g^–1 DW at the beginning of the experiment to 1322 ng g^–1 DW at the end of vase life. The TDZ inhibited carotenoid degradation, but did not affect the ABA concentration, while the 8-HQS did not prevent carotenoid degradation and the ABA concentration was only slightly affected. ABA seems to be a secondary senescence bio-product that may have a synergic effect with other senescence inducers dramatically accelerating leaf senescence.     

Hydrogen sulfide promotes calcium signals and migration in tumor-derived endothelial cells

Hydrogen sulfide (H₂S) is a gasotransmitter that plays several roles in various tissues, including the cardiovascular system. Because it has been recently proposed to act as a mediator of angiogenesis progression, here we investigate the effects of H₂S in a well-established model of tumor angiogenesis: endothelial cells obtained from human breast carcinoma (B-TECs). Ca²⁺ imaging and patch-clamp experiments reveal that acute perfusion with NaHS, a widely employed H₂S donor, activates cytosolic calcium (Ca_c) increase, as well as potassium and nonselective cationic currents, in B-TECs. Stimulation with NaHS in the same concentration range (1 nM-200 μM) evoked Ca_c signals also in “normal” human microvascular endothelial cells (HMVECs), but the amplitude was significantly lower. Moreover, although NaHS failed to promote either migration or proliferation on HMVECs, B-TEC migration was enhanced at low-micromolar NaHS concentrations (1-10 μM). Remarkably H₂S mediates tumor proangiogenic signaling triggered by vascular endothelial growth factor (VEGF). B-TECs pretreated with dl-propargylglycine (5 mM, 30 min), an inhibitor of the H₂S-producing enzyme cystathionine γ-lyase, showed drastically reduced migration and Ca_c signals induced by VEGF (20 ng/ml). We conclude that H₂S plays a role in proangiogenic signaling of tumor-derived but not normal human ECs. Furthermore the ability of this gasotransmitter to interfere with B-TEC responsiveness to VEGF suggests that it could be an interesting target for antiangiogenic strategies in tumor treatment.     

Influence of plant species and plant growth stage on Frankliniella occidentalis pupation behaviour in greenhouse ornamentals

The influence of plant stage and plant species on the pupation behaviour of western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), was investigated in flowering and non‐flowering potted chrysanthemums and mini roses. On non‐flowering chrysanthemums and roses, 92–93% of the F. occidentalis pupated in the soil. On flowering roses, 87% pupated in the soil, and on flowering chrysanthemums only 60% chose the soil as a pupation site and 40% stayed on the plant. This means that, in the presence of flowers, especially complex inflorescences like chrysanthemums, a large proportion of F. occidentalis chooses stay on the plant to pupate.     

Nitric oxide retards xanthine oxidase-mediated superoxide anion generation in Phalaenopsis flower: an implication of NO in the senescence and oxidative stress regulation

Senescence is a developmentally regulated and highly ordered sequence of events. Senescence leads to abscission of plant organs and eventually leads to death of a plant or part of it. Present study revealed that Phalaenopsis flower undergo senescence due to over activation of O₂ ^·−generating xanthine oxidase (XO), which consequently increases the concentrations of O₂ ^·− leading to enhanced oxidative damage and disturbed cellular redox environment as indicated by increased lipid peroxidation and DHA/AsA + DHA ratio, respectively. While activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), and non-specific peroxidase (POD) were enhanced in sepals and petals of old flower, activities of catalase (CAT) and glutathione reductase (GR) were decreased. Exogenous application of nitric oxide (NO) retarded H₂O₂-induced senescence of Phalaenopsis flower by downregulating activity of XO and concentrations of O₂ ^·−, H₂O₂ and malondialdehyde (MDA, an index of lipid peroxidation). Exogenous application of NO also downregulated SOD activity and upregulated antioxidant enzymes involved in the detoxification of H₂O₂ (CAT and APX), and in the regulation of redox couples viz, monodehydroascorbate reductase (MDHAR) and GR, together with the modulation in non-protein thiol status and DHA/AsA + DHA ratio.     

Vase life of cut rose cultivars ‘Avalanche’ and ‘Fiesta’ as affected by Nano-Silver and S-carvone treatments

Rosa hybrida L. is an important commercial cut flower. The vase life of this flower is usually short due to vascular occlusion. We assessed the effect of Nano-Silver (NS) and S-carvone in prolonging the vase life of R. hybrida L. cv. ‘Avalanche’ and ‘Fiesta’. Hence, an experiment involving the treatment with NS at 0, 50, 100, and 200 mgL^− 1 and S-carvone at 0, 0.25, 0.5, and 0.75 mgL^− 1 with 10 replicates was conducted. Applying NS pulse treatments increased vase life, water uptake rate, and fresh weight and reduced the number of bacteria, water loss, stomatal conductance and transpiration rate. However, S-carvone treatments did not have a positive effect on the vase-life parameters of cut rose flowers. NS pulse treatments increased relative fresh weight (RFW), and water uptake rate (WUR) and decreased water loss (WL) (%) by 10, 89 and 31% for cultivar ‘Avalanche’, compared to the controls, respectively. Application of 200 mgL^− 1 NS led to the highest vase life (18 days) for roses. The results show that NS increased vase life by suppressing stomatal opening, decreasing transpiration from leaves and inhibiting bacterial proliferation.     

Photoperiod and elicitors increase steviol glycosides,phenolics, and flavonoid contents in root cultures of Stevia rebaudiana

The establishment of green root cultures of Stevia rebaudiana Bertoni, and the effect of elicitors such as hydrogen peroxide (H₂O₂) and methyl jasmonate (MeJA), is shown in the present study. Stevioside, rebaudioside A, and the isomers steviol/isosteviol were identified through DFI-ESI-IT-MSⁿ and UPLC-TOFMS spectrometric systems, in combination with solid-phase extraction. The accumulation of steviol glycosides increased by 2.4 times (compared to the control value of 22.35 μgSG per gDW), with the addition of 250 μM H₂O₂. The non-enzymatic antioxidant response, which resulted from production of phenolic and flavonoid compounds, was modified based on the elicitor and the dose used. The maximum accumulation of flavonoids was induced on the third day with the addition of H₂O₂ (250 or 500 μM), and with MeJA (250 or 500 μM); the increase was observed on the fifth day. The enzymatic antioxidant response of the catalase and peroxidase from the roots under elicitation confirmed the stress conditions.

     

Flower colour and cytochromes P450

Flavonoids are major constituents of flower colour. Plants accumulate specific flavonoids and thus every species often exhibits a limited flower colour range. Three cytochromes P450 play critical roles in the flavonoid biosynthetic pathway. Flavonoid 3′-hydroxylase (F3′H, CYP75B) and flavonoid 3′,5′-hydroxylase (F3′5′H, CYP75A) catalyze the hydroxylation of the B-ring of flavonoids and are necessary to biosynthesize cyanidin-(red to magenta) and delphinidin-(violet to blue) based anthocyanins, respectively. Pelargonidin-based anthocyanins (orange to red) are synthesized in their absence. Some species such as roses, carnations and chrysanthemums do not have violet/blue flower colour due to deficiency of F3′5′H. Successful expression of heterologous F3′5′H genes in roses and carnations results in delphinidin production, causing a novel blue/violet flower colour. Down-regulation of F3′H and F3′5′H genes has yielded orange petunia and pink torenia colour that accumulate pelargonidin-based anthocyanins. Flavone synthase II (CYP93B) catalyzes the synthesis of flavones that contribute to the bluing of flower colour, and modulation of FNSII gene expression in petunia and tobacco changes their flower colour. Extensive engineering of the anthocyanin pathway is therefore now possible, and can be expected to enhance the range of flower colours.     

Hydrogen sulfide promotes wheat seed germination under osmotic stress

Effects of NaHS, H₂S donor, on germination and antioxidant metabolism in wheat (Triticum aestivum L.) seeds under osmotic stress were investigated. With the enhancement of osmotic stress, which was mimicked by PEG-6000, the seed germination dropped gradually. NaHS treatment could promote wheat seed germination against osmotic stress in a dose-dependent manner; while Na⁺ and other sulfur-containing components, such as S²⁻, SO₄²⁻, SO₃²⁻, HSO₄⁻ and HSO₃⁻, were not able to improve seed germination as NaHS did, confirming H₂S or HS⁻ derived from NaHS contribute to the protective roles. Further experiments showed that NaHS treatment combined with PEG enhanced the activities of amylase and esterase in comparison to PEG treatment alone. Alternatively, NaHS treatment significantly reduced malondialdehyde and hydrogen peroxide accumulation in seeds. Significant enhancement of catalase and ascorbate peroxidase activities and decrease in lipoxygenase activity were observed in NaHS treated seeds, while peroxidase and superoxide dismutase activities were not affected as compared with the control. Furthermore, the H₂S donor treatment could retain higher levels of endogenous H₂S in wheat seeds under osmotic stress. These data indicated that H₂S played a protective role in wheat seed against osmotic stress.     

H2S protects from oxidative stress-driven ACE2 expression and cardiac aging

Cystathionine gamma-lyase (CSE)-derived hydrogen sulfide (H₂S) plays an essential role in preserving cardiac functions. Angiotensin-converting enzyme 2 (ACE2) acts as the negative regulator of the renin-angiotensin system, exerting anti-oxidative stress and anti-inflammatory properties within the body. The interplays of CSE/H₂S signaling and ACE2 in cardiac aging are unclear. In this study, the regulatory roles of H₂S on ACE2 expression in mouse heart tissue and rat cardiomyocytes under different stress conditions were investigated. It was found that ACE2 protein level was lower in heart tissues from old mice (56-week-old) than young mice (8-week-old), and the knockout of CSE (CSE KO) induced moderate oxidative stress and further inhibited ACE2 protein level in mouse hearts at both young and old age. Incubation of rat cardiac cells (H9C2) with a low dose of H₂O₂ (50 µM) suppressed ACE2 protein level and induced cellular senescence, which was completely reversed by co-incubation with 30 µM NaHS (a H₂S donor). Prolonged nutrient excess is an increased risk of heart disorders by causing metabolic dysfunction and cardiac remodeling. We further found high-fat diet feeding stimulated ACE2 expression and induced severe oxidative stress in CSE KO heart in comparison with wild-type heart. Lipid overload in H9C2 cells to mimic a status of nutrient excess also enhanced the expression of ACE2 protein and induced severe oxidative stress and cell senescence, which were significantly attenuated by the supplementation of exogenous H₂S. Furthermore, the manipulation of ACE2 expression partially abolished the protective role of H₂S against cellular senescence. These results demonstrate the dynamic roles of H₂S in the maintenance of ACE2 levels under different levels of oxidative stress, pointing to the potential implications in targeting the CSE/H₂S system for the interruption of aging and diabetes-related heart disorders.

     

Hydrogen sulphide reduced the accumulation of lipid droplets in cardiac tissues of db/db mice via Hrd1 S-sulfhydration

Accumulation of lipid droplets (LDs) induces cardiac dysfunctions in type 2 diabetes patients. Recent studies have shown that hydrogen sulphide (H₂S) ameliorates cardiac functions in db/db mice, but its regulation on the formation of LDs in cardiac tissues is unclear. Db/db mice were injected with NaHS (40 μmol·kg^-1) for twelve weeks. H9c2 cells were treated with high glucose (40 mmol/L), oleate (200 µmol/L), palmitate (200 µmol/L) and NaHS (100 µmol/L) for 48 hours. Plasmids for the overexpression of wild-type Hrd1 and Hrd1 mutated at Cys115 were constructed. The interaction between Hrd1 and DGAT1 and DGAT2, the ubiquitylation level of DGAT1 and 2, the S-sulfhydration of Hrd1 were measured. Exogenous H₂S ameliorated the cardiac functions, decreased ER stress and reduced the number of LDs in db/db mice. Exogenous H₂S could elevate the ubiquitination level of DGAT 1 and 2 and increased the expression of Hrd1 in cardiac tissues of db/db mice. The S-sulfhydration of Hrd1 by NaHS enhanced the interaction between Hrd1 and DGAT1 and 2 to inhibit the formation of LD. Our findings suggested that H₂S modified Hrd1 S-sulfhydration at Cys115 to reduce the accumulation of LDs in cardiac tissues of db/db mice.     

Effects of plant growth regulators and sucrose on post harvest physiology,membrane stability and vase life of cut spikes of gladiolus

Effects of post-harvest application of two plant growth regulators viz., gibberellic acid (GA₃) and benzyl adenine (BA) with sucrose in the vase solution on cell membrane stability and vase life of gladiolus were investigated. The vase solution treatment combinations of GA₃ and BA with sucrose significantly increased the membrane stability index and enhanced the vase life as compared to the sucrose alone treatments or the controls. Vase solution treatment of GA₃ (50 mg l⁻¹), followed by BA (50 mg l⁻¹) with sucrose (50 g l⁻¹) significantly increased solution uptake, fresh weight and dry weight of cut spikes. The same treatments also enhanced the concentration of reducing and non-reducing sugars in gladioli petals 4 days after treatment (DAT). Cut spikes in vase solution enriched with 50 mg l⁻¹ GA₃ + 50 g l⁻¹ sucrose showed higher antioxidative enzyme activities of superoxide dismutase (SOD) and glutathione reductase (GR), lower lipoxygenase (LOX) activity and lipid peroxidation (measured as TBARS). Petal membrane stability index was also highest in cut spikes 6 DAT with 50 mg l⁻¹ GA₃ + 50 g l⁻¹ sucrose vase solution. Treatment of gladiolus cut spikes with 50 mg l⁻¹ GA₃ + 50 g l⁻¹ sucrose vase solution showed two fold increase in vase life and improved flower quality with a higher number of open flower per spike at any one time. These results suggest that post-harvest application of GA₃ (50 mg l⁻¹) with sucrose (50 g l⁻¹) maintains higher spike fresh and dry weight, improves anti-oxidative defence, stabilizes membrane integrity leading to a delay in petal cell death.     

外源H_2S对NO_3~-胁迫下番茄幼苗生理生化特性的影响

采用营养液水培方法,通过外源施加H2S供体NaHS(100μmol/L),研究了信号分子H2S对100mmol/L NO3-胁迫下番茄幼苗生理生化特性的影响。结果表明:(1)NO3-胁迫下,随着处理时间的延长,番茄幼苗的株高、根长、鲜重和干重显著降低,叶绿素(a、b)含量、净光合速率、气孔导度、蒸腾速率均显著降低,而胞间CO2浓度以及丙二醛(MDA)、H2O2含量增加,超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性显著降低,抗坏血酸(AsA)和还原性谷胱甘肽(GSH)含量显著降低。(2)与NO3-胁迫处理相比,外源NaHS处理1、3、5d后,番茄幼苗的株高、根长、鲜重和干重显著增加,叶绿素(a、b)含量、净光合速率、气孔导度、蒸腾速率均显著升高,而胞间CO2浓度显著降低;MDA和H2O2含量降低,SOD、POD、CAT和APX活性显著增强,AsA和GSH含量显著增加,而且幼苗的硝酸还原酶、谷氨酰胺合成酶、谷氨酸合酶的活性显著增强;L-半胱氨酸脱巯基酶活性和内源H2S含量增加。研究认为,外源H2S可能通过提高抗氧化物酶的活性和增加抗氧化物质含量来缓解NO3-对番茄幼苗造成的伤害,从而增强其对NO3-胁迫耐性。     

Reducing fertilization: a management tactic against western flower thrips on roses

Fertilization reduction could be a useful pest management tactic for floriculture crops if it reduced pest populations with minimal impact on crop yield and quality. We evaluated the response of the western flower thrips, Frankliniella occidentalis Pergande (Thysanoptera: Thripidae), to different fertilization levels for cut roses, Rosa hybrida L. cv. ‘Tropicana’, and quantified fertilization effects on (i) abundance of F. occidentalis on cut roses, (ii) biological control of F. occidentalis on cut roses and (iii) nutritional quality of the cut flower crop. We tested a commercially available fertilizer (Peters Excel 15‐5‐15 Cal‐Mag; The Scotts Company, Marysville, OH) at 100% and 33% of the recommended nitrogen level (150 ppm N) for rose production using liquid‐feeding and two control measures: no thrips control measure; release of a predatory mite, Amblyseius swirskii (Athias‐Henriot). To maintain equivalent ratios of macro‐ and micronutrients for all our fertilizer treatments, we varied only the concentration of the fertilizer to the levels specified in our experiments. Lowering fertilization rate from 100% to 33% of the recommended level reduced mean F. occidentalis abundance on cut roses by 30%. Combinations of both bottom‐up (fertilization) and top‐down (biological control) tactics provided better F. occidentalis control than either tactic alone. Flower production was not compromised on plants fertilized with 33% of the recommended level. Nitrogen, phosphorous and potassium content of the leaf tissue decreased at 33% of the recommended fertilization level, but all values were within optimal ranges for cut roses. We propose that fertility management may be an effective means of reducing thrips numbers on cut roses.     

Exogenous Melatonin Modulates Endogenous H2S Homeostasis and L-Cysteine Desulfhydrase Activity in Salt-Stressed Tomato (Solanum lycopersicum L. var. cherry) Seedling Cotyledons

Although melatonin has been reported to function as a stress signaling molecule, not much information is available on the biochemical and molecular events associated with probable melatonin-hydrogen sulfide crosstalk in plants. Present work provides evidence on the role of melatonin in the modulation of H₂S homoeostasis during NaCl stress in dark-grown tomato (Solanum lycopersicum L. var. cherry) seedlings. NaCl stress (120 mM) inhibits hypocotyl elongation, promotes primary root growth and enhances electrolytic leakage from tomato seedlings. Treatment with H₂S donor (100 µM; NaHS) tends to reverse these effects, all the more so (additive effect) in the presence of melatonin. NaCl stress and exogenous melatonin (30 µM) treatments modulate endogenous H₂S accumulation and positively upregulate the activity of L-cysteine desulfhydrase (L-DES; EC 4.4.1.15; cytosolic). Melatonin has been observed to temporally modulate the activity of specific isoforms of H₂S biosynthesizing enzyme, L-DES in seedling cotyledons. Zymographic analysis of L-DES isoforms in tomato seedling cotyledons has provided novel findings in plant system. Melatonin treatment decreases H₂S accumulation in NaCl-stressed seedling cotyledons which is accompanied by a contrasting increase in L-DES activity. Melatonin, therefore, regulates endogenous H₂S concentration in seedling cotyledons (NaCl treated), thus indicating the role of H₂S catabolism pathways in H₂S homoeostasis. Present findings thus reveal that exogenous melatonin modulates early H₂S signaling in cotyledons of tomato seedlings subjected to NaCl stress. Furthermore, exogenous melatonin and H₂S in combination (additive effect) ameliorate NaCl stress-induced growth changes in tomato seedlings.

     

Responses of nitric oxide and hydrogen sulfide in regulating oxidative defence system in wheat plants grown under cadmium stress

We conducted a study to evaluate the interactive effect of NO and H₂S on the cadmium (Cd) tolerance of wheat. Cadmium stress considerably reduced total dry weight, chlorophyll a and b content and ratio of Fv/Fm by 36.7, 48.6, 26.7 and 19.5%, respectively, but significantly enhanced the levels of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA), endogenous H₂S and NO, and the activities of antioxidant enzymes. Exogenously applied sodium nitroprusside (SNP) and sodium hydrosulfide (NaHS), donors of NO and H₂S, respectively, enhanced total plant dry matter by 47.8 and 39.1%, chlorophyll a by 92.3 and 61.5%, chlorophyll b content by 29.1 and 27.2%, Fv/Fm ratio by 19.7 and 15.2%, respectively, and the activities of antioxidant enzymes, but lowered oxidative stress and proline content in Cd-stressed wheat plants. NaHS and SNP also considerably limited both the uptake and translocation of Cd, thereby improving the levels of some key mineral nutrients in the plants. Enhanced levels of NO and H₂S induced by NaHS were reversed by hypotuarine application, but they were substantially reduced almost to 50% by cPTIO (a NO scavenger) application. Hypotuarine was not effective, but cPTIO was highly effective in reducing the levels of NO and H₂S produced by SNP in the roots of Cd-stressed plants. The results showed that interactive effect of NO and H₂S can considerably improve plant resistance against Cd toxicity by reducing oxidative stress and uptake of Cd in plants as well as by enhancing antioxidative defence system and uptake of some essential mineral nutrients.     

Anti-apoptotic action of hydrogen sulfide is associated with early JNK inhibition

The mechanism of action of Hydrogen sulfide (H₂S) as a novel endogenous gaseous messenger and potential cardioprotectant is not fully understood. We therefore investigated the prevention of cardiomyocyte apoptosis by exogenous H₂S and the signaling pathways leading to cardioprotection. Using a simulated ischemia–reperfusion (I/Re) model with primary cultured rat neonatal cardiomyocytes, I/Re induced a rapid, time-dependent phosphorylation of c-Jun N-terminal kinase (JNK), with significant elevation at 0.25 h and a peak at 0.5 h during reperfusion. NaHS (H₂S donor) significantly inhibited the early phosphorylation of JNK, especially at 0.5 h. Both NaHS and SP600125 (specific JNK inhibitor) decreased the number of apoptotic cells, lowered cytochrome C release and enhanced Bcl-2 expression. When NaHS application was delayed 1 h after reperfusion, the inhibition of apoptosis by H₂S was negated. In conclusion, this is novel evidence that early JNK inhibition during reperfusion is associated with H₂S-mediated protection against cardiomyocyte apoptosis.