| Programmed cell death (PCD) of aleurone cells is actively controlled, genetically encoded self-destructive mechanism. After hydrolase secretion is complete, living aleurone cells are superfluous and die. Aleurone cells of cereal seeds have become a model to study programmed cell death in plants. In the present study, the effect of SO2 donor (NaHSO3/Na2SO3) on PCD of wheat aleurone layers was investigated. The results showed that SO2 donor delayed PCD of aleurone cells in a dose-dependent manner. The wheat aleurone cells treated with various concentrations of SO2 donor delayed cell death significantly and at an optimal concentration of 100μM. Moreover, SO2 donor treatment delayed the enlarged protein storage vacuoles (PSV), the degradation of DNA and the soluble protein in wheat aleurone cells. Gene expression analysis showed that the expressions of TaSultri4;la, TaSiR, TaOASTL, TaCoA, TaGHPOD were increased and TaSultril;!, TaAPR expressions were inhibited with SO2 treatment in wheat aleurone cells.The burst of reactive oxygen species (ROS) is a significant event on PCD of aleurone cells. Further investigation showed that SO2 donor treatment maintained higher activities of guaiacol peroxidase (POD), ascorbate peroxidase (APX), catalase (CAT),superoxide dismutase (SOD),and lower activities of lipoxygenase (LOX), polyphenol oxidase(PPO), relative to untreated controls. SO2 donor also reduced the content of hydrogen peroxide (H2O2) and superoxide a nion (O2) to levels below controls. We interpret that SO2 plays an antioxidative role in delaying PCD of wheat aleurone cells.Hydrogen sulfide (H2S) has been identified as a third gasotransmitter after nitro oxide (NO) and carbon monoxide (CO) in plants and SO2 donor (NaHSO3:Na2SO3) generate H2S under sulfite reductase. We investigated the relation of SO2 and H2S delaying programmed cell death in wheat aleurone cells. In this paper, the content of endogenous NO and H2S in wheat aleurone cells treated with SO2 were inverstigated. The results showed the content of endogenous H2S and NO were increased significantly in wheat aleurone cells treated with SO2 or H2S. Further studies showed the wheat aleurone cells treated with SO2 or H2S plus cPTIO maintained low endogenous H2S levels, high death cells, and low expression of TaCAT, TaAPX, TaSOD. These results showed that SO2 or H2S delay PCD by secreating endogenous H2S and NO and the regulating TaCAT, TaAPX, TaSOD gene expressions in wheat aleurone cells.The activity of β-amylase was investigated with H2S donor treatment. The results showed that H2S donor treatment maintained higher activities of total p-amylase, free β-amylase and bound β-amylase in a dose-dependent manner. The wheat seeds treated with various concentrations of H2S donor increased P-amylase activity significantly higher than the controls, and an optimal concentration of 1.5 mM. The bound β-amylase activity with SO2 donor treatment was also studied. The results showed that SO2 donor increased the bound β-amylase activity significantly.Wheat grains geminated in water for 36 h were pretreated with or without 1 mM SO2 donor for 12 h prior to exposure to Al stress for 48 h and the ameliorating effects of SO2 on wheat radicles were studied. SO2 donor pretreatment reduced the content of reactive oxygen species, protected membrane integrity and reduced Al accumulation in wheat radicles. Gene expression analysis showed that SO2 donor pretreatment decreased the expression of Al-responded genes TaWalil, TaWali2, TaWali3, TaWali5, TaWali6 and TaALMTl in radicles exposed to Al stress. These results suggest that SO2 could decrease endogenous Al content in wheat grains to alleviate the toxicity of Al-stressed wheat radicles. In total, SO2 regulated the activity of antioxidant enzymes, reduced the accumulation of ROS, enhanced sulfur metabolism related genes expression and amylase activity, delayed PCD of aleurone cells, reduced the toxicity of Al-stressed wheat radicles, thus, promoted wheat seeds to sprout and germinate. |
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