Jianping Luo

Hydrogen Sulfide Alleviates Aluminum Toxicity in Germinating Wheat Seedlings

Protective role of hydrogen sulfide (H(2)S) on seed germination and seedling growth was studied in wheat (Triticum) seeds subjected to aluminum (Al(3+)) stress. We show that germination and seedling growth of wheat is inhibited by high concentrations of AlCl(3). At 30 mmol/L AlCl(3) germination is reduced by about 50% and seedling growth is more dramatically inhibited by this treatment. Pre-incubation of wheat seeds in the H(2)S donor NaHS alleviates AlCl(3)-induced stress in a dose-dependant manner at an optimal concentration of 0.3 mmol/L. We verified that the role of NaHS in alleviating Al(3+) stress could be attributed to H(2)S/HS(-) by showing that the level of endogenous H(2)S increased following NaHS treatment. Furthermore, other sodium salts containing sulfur were ineffective in alleviating Al(3+) stress. NaHS pretreatment significantly increased the activities of amylases and esterases and sustained much lower levels of MDA and H(2)O(2) in germinating seeds under Al(3+) stress. Moreover, NaHS pretreatment increased the activities of guaiacol peroxidase, ascorbate peroxidase, superoxide dismutase and catalase and decreased that of lipoxygenase. NaHS pretreatment also decreased the uptake of Al(3+) in AlCl(3)-treated seed. Taken together these results suggest that H(2)S could increase antioxidant capability in wheat seeds leading to the alleviation of Al(3+) stress.We recently reported that H 2S could significantly promote the germination of wheat grains subjected to aluminum (Al(3+)) stress.1 In these experiments seeds were pretreated with the H 2S donor NaHS for 12 h prior to Al(3+) stress. During this pre-incubation period we observed that H2S increased the activity of grain amylase in the absence of Al(3+). Using embryoless half grains of wheat we now show that H2S preferentially affects the activity of endosperm β-amylase and that α-amylase synthesis and activity is unaffected by this treatment.

Hydrogen sulfide counteracts chlorophyll loss in sweetpotato seedling leaves and alleviates oxidative damage against osmotic stress.

In this paper, effect of NaHS, a hydrogen sulfide (H2S) donor on chlorophyll and antioxidant metabolism in seedling leaves of sweetpotato under osmotic stress was investigated. With the enhancement of osmotic stress, which was mimicked by PEG-6000, chlorophyll in seedling leaves of sweetpotato (Ipomoea batatas) decreased dramatically. At 15% PEG (w/v), chlorophyll concentration reached only 50% compared with that of the controls. The osmotic-induced decrease in chlorophyll concentration could be alleviated by spraying exogenous H2S donor, NaHS in a dose-dependent manner, while little visible symptoms were observed in leaves sprayed with NaHS under control conditions. It was also shown that H2S or HS− rather than other sulfur-containing components derived from NaHS contributed to the protective role against chlorophyll degradation during osmotic stress. Further studies showed that NaHS spraying dramatically promoted the activities of superoxide dismutase, catalase, ascorbate peroxidase and decreased that of lipoxygenase and the concentrations of hydrogen peroxide (H2O2) and malondialdehyde. In addition, concentrations of endogenous H2S in NaHS-sprayed seedlings were higher than that in water-spraying control under osmotic stress. These data indicated that H2S plays a protective role in sweetpotato seedlings during osmotic stress.

Hydrogen sulfide alleviated chromium toxicity in wheat

Effects of H2S on seed germination under chromium (Cr) stress were investigated in wheat (Triticum aestivum L.). Under Cr stress, the percentage of germination of wheat seeds decreased, but this decrease could be alleviated by pretreatment with NaHS, an H2S donor, in a dose-dependent manner. Furthermore, NaHS significantly enhanced the activities of amylase, esterase, superoxide dismutase, catalase, ascorbate peroxidase, and guaiacol peroxidase in Cr-stressed germinating seeds, whereas reduced the Cr-induced increase in lipoxygenase activity and over-production of malondialdehyde (MDA) and H2O2, and sustained slightly higher content of endogenous H2S.

Hydrogen sulfide protects soybean seedlings against drought-induced oxidative stress

Increasing evidence indicates that hydrogen sulfide (H2S) is the third “gas signal molecule” after NO and CO in animal. In the present study, we found that soybean (Glycine max L.) seedlings sprayed with exogenous H2S donor NaHS prolonged the longer survival time of life, and enlarged higher biomass of both leaf and root than in non-sprayed controls under continuous drought stress. With the continuous drought stress, the content of chlorophyll in the leaves of both Xu-1 and Xu-6 cultivar of soybean decreased dramatically. The drought-induced decrease in chlorophyll could be alleviated by spraying H2S donor. It was also shown that spraying with H2S donor dramatically retained higher activities of superoxide dismutase (SOD, EC 1.1.5.1.1), catalase (CAT, EC1.11.1.6) and lower activity of lipoxygenases (LOX, EC 1.13.11.12), delayed excessive accumulation of malondialdehyde, hydrogen peroxide, and superoxide anion (O2·−) compared with the control. These results suggest that H2S can increase drought tolerance in soybean seedlings by acting as an antioxidant signal molecule for the response.

Enhanced somatic embryogenesis by salicylic acid of Astragalus adsurgens pall. : relationship with H2O2 production and H2O2-metabolizing enzyme activities

Abstract Salicylic acid (SA), when added to the differentiation medium below 200 μmol/l, significantly enhanced somatic embryogenesis in callus culture of Astragalus adsurgens Pall. The highest frequency of somatic embryogenesis occurred at 150 μmol/l SA. Enhanced somatic embryogenesis by SA was accompanied by an increase in the endogenous H 2 O 2 level as compared with controls. This increased endogenous H 2 O 2 level was related to the inhibition of the activities of ascorbate peroxidase (APX) and catalase (CAT). Although the promoting effect of exogenous H 2 O 2 was significantly lower than that of exogenous SA on the development of somatic embryos, the pre-treatment of callus with dimethylthiourea (a trap for H 2 O 2 ) significantly inhibited somatic embryogenesis, even if callus was cultured on the differentiation medium supplemented with 150 μmol/l SA, suggesting that the endogenous H 2 O 2 was required for SA-enhanced somatic embryogenesis. The significance of the interaction of SA, H 2 O 2 and H 2 O 2 -metabolizing enzymes during somatic embryogenesis is discussed, and the possible relationship between SA-enhanced somatic embryogenesis and SA-induced pathogenesis-related proteins is proposed.

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.

Cold-enhanced somatic embryogenesis in cell suspension cultures of Astragalus adsurgens Pall.: relationship with exogenous calcium during cold pretreatment

The inter-relationship between exogenous calcium (Ca2+) during cold pretreatment and cold-enhanced somatic embryogenesis was investigated using cell suspension cultures of Astragalus adsurgens Pall. Cell suspension was obtained from embryogenic callus and could be induced to form somatic embryos in the differentiation medium. Suspension cells, after cold-treatment at 8 °C for 2 to 3 wk, displayed an enhanced capacity for somatic embryogenesis as compared to those without cold pretreatment. Longer cold pretreatment (> 4 wk) resulted in the inhibition of somatic embryogenesis. The enhanced embryogenic response of cells to cold pretreatment was dependent on the Ca2+ level in the pretreatment medium. Ca2+ levels below 1 mM suppressed the cold-enhanced response. Addition of lanthanum into the pretreatment medium completely abolished the cold induced enhancement of somatic embryogenesis. These results suggest that embryogenic cells require a minimal concentration of Ca2+ during pretreatment for the expression of this cold-enhanced capacity for somatic embryogenesis in A.adsurgens and the influx of exogenous Ca2+ during pretreatment might also be involved.