| Flooding can obstruct the oxygen exchange between air and plants’ roots and leaves,thus reduce the supply of oxygen in plant cells.As a final electron acceptor on the mitochondrial electron transport chain,oxygen plays an significance role in respiratory process.Oxygen deficiency caused by flooding can affect aerobic respiration and reduce energy supply in plants,which will affect photosynthesis and result in oxidative stress and cell death.Researches showed that a variety of biotic and abiotic stresses can increase H2 S concentration,which will enhance survival of plants under various stresses.However,weather H2 S is involved in the process of response to hypoxia caused by flooding is not fully understood.This project aims to determine functions of H2 S in plants response to flooding stress,by using wild-type Col-0,H2 S synthesis defective mutant desl-l and overexpression line（35S::DES1）as experimental materials.The techniques of phenotypic statistics,histochemical staining,physiological and biochemical index measurements as well as Quantitative Real-time PCR were used to detect the survival rate,changes of ROS contents,H2 S concentration,enzyme activities of both antioxidant system and H2 S metabolism,and the expressions of genes involved in antioxidant system,H2 S metabolism and hypoxia perception and response caused by submergence.The results are as follows:1.According to the phenotypes after submergence for 4 days and followed by reoxygenation for another 4 days,des1-1 mutant was more seneitive to submergence and showed a lower survival rate compared to wild-type,while 35S::DES1 was more healthy than wild type.Interestingly,H2 S pretreatment can increase the survival rate of des1-1 mutant,demonstrating that H2 S played an important role in hypoxia response process.2.The Evans Blue and DAB staining results showed that less leaves death and lower H2O2 concentration were observed in Arabidopsis plants pertreated with H2 S compared to the plants pretreated with dH2 O.In addition,compared to wild-type,des1-1 showed a higher level of cell death in its leaves and had a higher ROS accumulation.In terms of gene expression,ROS production-related genes also had a higher level in des1-1.Based on the result of cell conductivity,H2 S can also reduce the penetration of intracellar electrolyte under flooding condition,while des1-1 showed a high level of the penetration of intracellar electrolyte,which suggested that H2 S can not only reduce the production of ROS and also the damage of ROS to cell membrane under flooding condition.3.The plants pretreated with H2 S showed higher activities of SOD,CAT and APX.Besides,a high APX gene expression was also observed in this group.Thus,H2 S pretreatment can help to remove the reactive oxygen species in time,and reduce the damage caused by reactive oxygen and improve the tolerance of plants to flooding.4.Compared to wild-type,des1-1 showed a lower H2 S concentration,and H2 S pretreament reduced H2 S synthase activity slightly and increased endogenous H2 S concentration,gene expressions involved in H2 S synthetic and catabolic pathway and the enzyme activity responsible for synthesizing H2 S.5.Quantitative Real-time PCR results of N-end rule pathway genes and hypoxiaresponse genes showed that H2 S pretreatment can stimulate the expression of hypoxiaresponse genes ADH1 and PDC1 by up-regulating PAP2.12 gene.In summary,des1-1 had a lower tolerance compared to wild type,while H2 S pretreatment can improve the tolerance of waterlogging and increase the endogenous H2 S concentration,indicating that H2 S is involved in response to waterlogging.More specially,H2 S can enhance the waterlogging tolerance of plant by reducing the ROS concentration,maintaining cell membrane integrity,improving the antioxidant system,alleviating cell death,affecting H2 S metabolism and improving hypoxia-related genes expressions. |
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