Determinion Of Chromium Species And The Subsequent Upde Phway By Plant

Chromium(Cr)was classified as a carcinogen by the Environmental Protection Department of the United Stes due to its toxicity,carcinogenicity,mutagenicity,and widespread problems.In recent years,the mining and industrial production of chromium ores,such as dyestuff and leher factories,have discharged a large amount of Cr-containing residues and Cr-containing waste wer into the environment,resulting in a large number of farmland contamined with Cr.The Cr in the soil is found mainly.in the form of Cr(Ⅵ)and Cr(Ⅲ).Cr(Ⅲ)is less mobile with low toxicity,while Cr(Ⅵ)is a high mobile anion with high toxicity.Chromium caninhibit the growth of plants,and also can enter the human body through the food chain,potentially causing an adverse health effect.Therefore,it is of gre significance for agricultural production and human health to study the absorption of Cr(Ⅵ)by plants.There is no special transport channel for Cr(Ⅵ)in the plant,and therefore it is assumed th Cr(Ⅵ)entres plants as a‘hitchhiker’ through transporters of sulfe,phosphe or molybde.presents,some experiments have provide evidence th phosphe and sulfe can inhibit the uptake of Cr(Ⅵ)and reduce the toxicity of Cr(Ⅵ)to plants.However,the transporter specifically responsible for the absorption of Cr(Ⅵ)molecular level in plant is still unclear.In the current reaserch,Arbidopsis thaliana was used as the modle plant to find the specific transporter for Cr(Ⅵ)in plant by exploring the resistance and absorption of Cr(VI)of the sulfe transport mutants(sultr1;1 and sultr1;2),phosphe mutants(pht1;1 and pht1;4)and molybde mutants(mot1).Also,yeast heterologous expression was used toHere we verify Cr(Ⅵ)transport phways in plant.The specific experimental content and research results are as follows:(1)A method for simultaneously detecting both Cr(Ⅵ)and Cr(Ⅲ)in the sample by HPLC-ICP/MS was established.The mobile phase and flow re used for the HPLC-ICP/MS analyis was:2 mM TBAH+0.6 mM EDTA for mobile phase with a flow re of 1.5 mL/min.Then the optimum chromium isotope was determined based on the instrument’s response to different chromium isotopes,the baseline size and the noise strength.The detection limits of Cr(Ⅵ)and Cr(Ⅲ)were as low as 0.35 μg/L and 0.44 μg/L.the same time,we measured the accuracy and stability of the detection method,and the results showed th the established detection method were capable of meeting the requirements of the experiment.(2)The comparion of growth phenotypes of Arabidopsis thaliana mutants(pht1;1,pht1;4,sultr1;1,sultr1;2 and mot1)and wild type(Col-0)under Cr(Ⅵ)exposure shown th there was no significant difference between the growth phenotypes of sulfe transporter protein mutant(sultr1;1),phosphe mutant(pht1;1 and pht1;4)and Molybde Mutant(mot1)and wild type on the agar mediacontaining Cr(Ⅵ).The resistance of sulfe mutant sultr1;2 to Cr(Ⅵ)was significantly higher than th of wild type,suggesting th Cr(Ⅵ)might be absorbed by Arabidopsis through sulfe transporter protein Sultr1;2.(3)The growth phenotypes of Arabidopsis thaliana mutant(pht1;1,pht1;4,sultr1;1,sultr1;2 and mot1)and wild type(Col-0)under Cr(Ⅵ)stress were compared in hydroponic experiemnts.It was also found th only the deletion of sulfe transporter Sultr1;2 could enhance the resistance to Cr(Ⅵ)of Arabidopsis.the same time,we measured the short-term absorption of Cr(Ⅵ)by Sultr1;1 and Sultr1;2 mutants and wild type.The results showed th the deletion of Sultr1;2 significantly decreased the absorption of Cr(Ⅵ)by Arabidopsis thaliana,further indicing th Sultr1;2 was involved in the uptake of Cr(Ⅵ)in Arabidopsis thaliana.In addition,Real-Time quantitive PCR showed th the expression of Sultr1;1 was inhibited by Cr(Ⅵ)stress and the expression of Sultr1;2 was not affected.(4)In order to further verify the ability of sulfe transporter to transport Cr(Ⅵ),we expressed the sulfe transporter gene Sultr1;1 and Sultr1;2 in yeast.It was found th the heterologous expression of Sultr1;2 gene significantly increased the sensitiⅥty of yeast strains to Cr(Ⅵ),and increased the amount of Cr(Ⅵ)absorbed by yeast strains.In contrast,although the heterologous expression of Sultr1;1 resulted in a significant increase in the sensitiⅥty of yeast strains to Cr(Ⅵ),but the increasing magenitude was much less than th when expressing Sultr1;2.The results showed th both Sultr1;1 and Sultr1;2 was likely able to transport Cr(Ⅵ)into plants,but the transport capacity of Sultr1;2 was significantly higher than th of Sultr1;1.In conclusion,both Sultrl;1 and Sultr1;2 can transport Cr(Ⅵ).In Ⅵew of Sultr1;1 has relively lower ability to transport Cr(Ⅵ)and the expression of its coding gene was inhibited by Cr(Ⅵ)stress.The uptake of Cr(Ⅵ)in Arabidopsis thaliana was mainly medied by Sultr1;2.In the present study,we first studied the uptake of Cr(Ⅵ)by plants the molecular level and identified the transporters responsible for the uptake of Cr(Ⅵ)by Arabidopsis thaliana.The study proⅥdes a new genetic and theoretical basis for the modificion of crops by genetic engineering,the cultivion of low absorbability of Cr(Ⅵ),high tolerance of crop varieties and the improvement of Cr enrichment ability of plants and the improvement of phytoremediion potential.It has important theoretical significance and certain applicion prospect.