| Cadmium(Cd)is one of the most harmful heavy metals in nature.The accumulation of excess Cd in animals and plants will lead to the obstruction of growth and development,and the abnormal physiological metabolism and so on.Hydrogen Peroxidized(H2O2)as an endogenous signal molecule in plants,participates in various physiological responses of plants and plays an important regulatory role in the process of plant resistance.In this paper,rice Zhongyou 169 was used to elucidate the mechanism of H2O2 poisoning on rice Cd from the effects of H2O2 on oxidative damage,cell membrane damage,Cd accumulation and distribution in plant subcellular and response to differential protein expression under the Cd stress.The aim is to provide a theoretical basis for elucidating the mitigation mechanism of H2O2 on Cd toxicity in rice.The major results are as follow:1.Exogenous H2O2 treatment could alleviate the poisoning effect of Cd on the growth of the rice seedlings,but there is a concentration effect.In the range of 5-50 ?mol/L H2O2 treatment,the50 ?mol/L H2O2 treatment exerts the most obvious effect on alleviating the Cd poisoning,which had greatly promoted of the height of the rice plants and increased the biomass growth,Based on this,50 ?mol/L H2O2 concentration will be used for the subsequent tests.2.Cd treatment significantly reduced CAT,APX activity and soluble protein content in vivo,increased POD activity,and resulted in over-accumulation of MDA content in the body.The ability to scavenge free radicals ABTS·,DPPH·,and super oxide anion weakened,reducing the total antioxidant power and total reducing power of the rice.The exogenous H2O2 treatment could increase the activity of antioxidant enzymes,enhance the scavenging ability of free radicals,increase the total antioxidant power and reducing power.3.Under Cd stress,the Cd content in rice seedlings increased significantly,especially the Cd accumulation in roots increased significantly,and the plant height biomass decreased significantly.Compared with the subcellular distribution of Cd in rice,Cd was mostly distributed in the cell walls and the soluble fraction of the cells of rice.H2O2 treatment could reduce the uptake ofcadmium by plants and decrease the Cd content in roots,leaves and subcells of rice seedlings,indicating that H2O2 treatment could reduce the uptake of Cd by rice plants,enhanced the binding of cell walls to Cd,and reduced the chelation of the Cd with the organics and fix it in the vacuole,reducing the transport of Cd to the shoots and preventing Cd from poisoning cells.4.Under Cd stress treatment,differential protein spots were identified by tandem mass spectrometry.The functions of the identified proteins are classified to obtain carbon metabolism-related proteins,stress-responsive proteins,proteins related to protein metabolism,and proteins related to gene expression or other metabolism.After the sole Cd treatment and the H2O2 treatment respectively,the differential proteins were glutathione reductase,L-ascorbate peroxidase 1,ATP synthase ? subunit,ATP synthase ? subunit,70 k Da heat shock protein,S-adenosylmethionine synthase 1,and UDP-glucose 6-dehydrogenase.5.Compared with the sole Cd treatment,the expression levels of Os SHP 70,Os APX 4,and Os GPX 1 genes in roots were significantly increased by H2O2+Cd treatment,which were 1.19,1.42,and 3.30 times more than that of the sole Cd treatment,while the expression of Os IRT 2 gene was decreased.Compared with the Cd stress,the H2O2+Cd treatment increased Os HSP 70,Os APX4,and Os GPX 1 by 1.23,1.94,and 1.65 times,respectively,while Os ABCG 43 was decreased by0.61 times less than that of roots. |
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