Preliminary Study On Over-expression Of TaGSTF3 In Arabidopsis Under Heavy Metal Lead And Nickel Stresses

Heavy metals gradually are discharged into sorroundings from minerals and other sources with the development of modern industry and the steadily growing world population.It brings serious contamination to soil,water and air.Heavy metal pollution affects plant especially crops growth directly and reduce the grain crop.The mechanism of plants responsing to saline-alkaline gets more attention for now.However,the mechanism of heavy metal toxicity stresses deserves more attention.In consideration of damage for plants caused by heavy metals,mechanisms of plants responsing to heavy metals have been an emergent task to study.In our previous study a new germplasm-the introgression line Shanrong no.4(named SR4),which generated from asymmetric somatic hybridization between common wheat Jinan 177(named JN177,2n=42)and tall wheat grass(Elytrigia elongata(Host)Nevski,EE,2n=14).Experiments in both the field and the lab confirmed that the SR4 displayed strong tolerance to saline-alkalinity.Thus,the alkali-treated transcriptome of SR4 was sequenced using the second generation high-throughput sequencing technologies.The gene TaGSTF3 was cloned and selected for further studies as it was up-regulated under salt and alkali stresses.However,TaGSTF3 transgenic over-expression of Arabidopsis thaliana didn't display tolerance towards saline-alkalinity.On the contrary,TaGSTF3 transgenic A.thaliana responsed to stresses of lead nitrate and nickel sulfate.In view of the above,we make a preliminary exploration the mechanisms of TaGSTF3 responsing to lead and nickel by studying the phenotypes and functions of TaGSTF3 transgenic Arabidopsis.The ORF of TaGSTF3 was about with a length of 669 bp from SR4.Agrobacterium-mediatd floral dip method was applied to generate TaGSTF3 over-expression(OE)lines in wild type A.thaliana,and finally,two TaGSTF3 homozygous OE lines were generated.1.Lead tolerance analysis of over-expression of TaGSTF3 in A.thaliana On the culture medium,TaGSTF3 OE lines had larger leaf area and more numerous roots than wild type A.thaliana under Pb2+ stress.Similarly,OE lines had more leaves and legumes compared with the wild type growing in the soil after treated with lead nitrate.Biochemical parameters analysis showed that OE lines had a significantly higher tolerance to Pb2+ with a higher fresh weight,chlorophyll content,total glutathione values,lower MDA content and the more activities of ROS scavening enzymes in OE lines than in that wild type.DAB and NBT staining and ROS related marker genes analysis implied that OE lines had accumulated a higher level of ROS under Pb2+ stress.Lead related genes analysis displayed that AtATM3 and AtGSHl might played an important role in TaGSTF3 responsing to lead.In addition,it showed that tolerance to Pb2+ of OE lines was dependent on GSH.In conclusion,GSH related metabolic pathway and ROS related metabolic pathways might play an important role in TaGSTF3 transgenic A.thaliana responsing to Pb2+ stress.2.Nickel tolerance on over-expression of TaGSTF3 in A.thalianaOn the culture medium,TaGSTF3 transgenic OE lines had larger leaf area and more numerous roots than wild type A.thaliana under Ni2+ stress.Similarly,OE lines showed a growth advantage compared with the wild type growing in the soil after treated with lead nitrate.Biochemical parameters analysis showed that OE lines had a higher tolerance to Ni2+ with a higher fresh weight,chlorophyll content,total glutathione values,lower MDA content and the activities of ROS scavening enzymes in OE lines were significantly increased than wild type.In addition,it showed that tolerance to Ni2+ of OE lines was dependent on GSH.In conclusion,GSH related metabolic pathway and ROS related metabolic pathways might play an important role in TaGSTF3 transgenic A.thaliana responsing to Ni2+ stress.