Dynamic Monitoring And Research Of Tobacco Cytoskeleton And Viscoelasticity Under Cadmium Stress

Heavy metal pollution in soil had affected the growth and development of plants seriously,resulting in a decline in yield and quality.Heavy metal ions can also enter the human body through the food chain and affect human health.The cell wall is the first barrier for plant cells to deal with heavy metal stress.The hindrance of heavy metals to plant growth is initially manifested as cell wall hardening and limited stretch ability,that is,heavy metals change the mechanical properties of plant cell walls.In addition,heavy metals can also affect the cytoskeleton through the plant cell wall-plasma membrane-cytoskeleton continuum or directly enter the protoplast.However,due to the lack of appropriate technology,there is still a lack of understanding of the mechanical properties of plant living cell wall and cytoskeleton under heavy metal stress.Comprehensive use of real-time fluorescence microscopic observation,cell viscoelasticity determination and cell enzyme activity index determination and other technical methods,this study explored the microscopic fluorescence changes and viscoelastic changes of tobacco suspension cells under cadmium stress:We first constructed a fluorescent protein-labeled microfilament transgenic tobacco(overexpressing Lifeact-EGFP)by genetic transformation,and established a stable microfilament-labeled suspension cell culture system based on the transgenic plant.The real-time fluorescence microscopy observation results of suspension cells under cadmium stress showed that the fluorescence signal of tobacco suspension cells was quenched rapidly within a range of 10-7 ~ 10-4 mol / L cadmium ion concentration gradient.When the cadmium ion concentration was at 10-8 mol / L,the fluorescence signal was temporarily increased in the early stage of stress(within 2 h),that is,the phenomenon of enhanced microfilament assembly.Based on the plant cell mechanics methods established by our lab based on the quartz crystal microbalance technology(QCM),this article explored the changes in the viscoelastic index(CVI)of tobacco suspension cells under different concentration gradients of cadmium ion stress.The research results show that the cells under the stress of 10-8 mol /L cadmium ion showed a rapid softening,and the phenomenon of stiffening in the later stage,and the suspension cells under the treatments of other concentrations of cadmium appeared softening.The changes in catalase(CAT)and peroxidase(POD)activities of tobacco suspension cells under cadmium ion stress were also measured.The results showed that: compared with the control,both the activities of CAT and POD of the tobacco suspension cells exposed to different concentrations of cadmium ion stress increased in the initial stage,Under higher cadmium concentration,with the extension of time,the enzyme activity decreased rapidly,indicating that the high cadmium toxicity caused the death of the suspension cells.Finally,based on the three levels of tobacco suspension cells corresponding to cadmium stress,the physiological phenomena of viscoelastic changes in tobacco suspension cells in response to cadmium stress are described,as well as the similarities and differences of cell viscoelastic changes under different concentrations of cadmium.