Effects Of Three Major Resistance Enzyme Gene Expressions Of Salix Roots On Pb And Cd Stress

Phytoremediation is a kind of green technology which is environmentally friendly,no secondary pollution and low cost.It can not only repair soil of heavy metals pollution,but also can beautify the environment and play a long-term effect of improving the ecological environment.Salix matsudana Koidz is a kind of Salicaceae Salix deciduous tree,which is characterized by wide distribution,strong adaptability,fast growth,high biomass and some tolerance to heavy metal stress.In order to study the resistance mechanism and resistance gene of the plant,the experiment was conducted to study the effects of different concentrations of Pb and Cd on the drought resistance of Salix psammophila seedlings,and the expression of three main resistance genes in root system of Salix psammophila seedlings.The main test conclusions are as follows:(1)The growth of Salix psammophila was gradually inhibited under Pb and Cd stress.With the increase of heavy metal concentration,the roots of Salix psammophila were obviously shrunk and the length of root was shortened.When the concentration of heavy metal reached the highest,it was found that the roots of Salix psammophila were extremely shrinking,and the stem and leaf became very fragile compared with the control group,The leaves will touch the drop,the growth of the entire plant almost stagnant.(2)Under Pb and Cd stress,the overall trend of the three main resistance enzyme activities of the root system of Salix seedlings increased first and then decreased with the increase of heavy metal concentration.SOD had the highest activity at Pb concentration of 3.0 mg/L.POD had the highest activity at Pb concentration of 0.5 mg/L.CAT had the highest activity at Pb concentration of 0.5 mg/L.SOD had the highest activity at the concentration of 1.0 mg/L under Cd stress.The activity of POD at 0.2 mg/L was the highest at Cd concentration.CAT had the highest activity at Cd concentration of 0.2 mg/L.It can be seen that low concentration of heavy metal ions against the enzyme has a certain stimulating effect,can increase the activity of resistant enzymes.(3)Real-time fluorescence quantitative PCR was used to screen the suitable internal reference genes under Pb and Cd stress.The expression of UBQ1,TUB6,Actin,EF1?,18SRNA,GAPDH,TUA8 and UBQ2 in the root of Salix seedlings were analyzed.The results showed that EF1?,GAPDH and Actin were stable under Pb and Cd stress,and the difference was that they were the most stable internal parameters in the roots of Salix under Pb stress.Gene is EF1?,and under Cd stress,the most stable internal reference gene is GAPDH.(4)Fluorescence quantitative PCR was used to determine the expression of SOD,POD and CAT.According to the results of real-time fluorescence quantitative PCR,the expression levels of SOD,POD and CAT were increased with the concentration of Pb and Cd.The overall trend of SOD gene expression in root system was Pb,Cd Concentration increased gradually.And the highest level of heavy metal concentration,gene expression also reached the maximum.These three antioxidant enzyme gene expression trends are not consistent with the trend of activity,this phenomenon is a delayed performance.Leading to this delay may be due to the antioxidant enzyme is transcribed into the mRNA by the relevant gene and then translated into peptide chain,and then some of the regulation and control to form a certain spatial structure of the protein,or because of high concentrations of heavy metal ions damage cells lead to translation efficiency As well as the reduced activity of the translational modification,or the possibility that the heavy metal ions may have an inhibitory effect on the catalytic activity of the enzyme itself.