Overexpression Of AtMGT1 And Ne-MDH Gene In Tobacco Confers Cadmium Accumlation And Tolerance

Cadmium is one of the most mobile and strongest toxic heavy metals in the environment. Phytoremediation as new technologies treat for heavy metal in contaminated soil is rise in recent years in the world.The basic idea is planting the natural growth or genetic cultivation of hyperaccumulator plants in contaminated soil,in order to absorb heavy metals,reducing or purifying the content of heavy metal in contaminated soil.Tobacco is a crops which can transfer cadmium.The mechanism of toxicity and resistantce of plants grow in contaminated soil by cadmium have been studied.Calcium and magnesium ions are necessary for plant growth nutrient,study shows that plant to improve the content of magnesium ions can effectively improve the tolerance toxicity by cadmium,enrich capabilities of cadmium, improve plant biomass.With the development of transgenic teclmology,modifying plants by transgenic technology to improve plant biomass,transport and accumulation of cadmium in the study to become a hot issue.We use the Tobacco as transgenic material,transform with AtMGT1-neMDH recombinant gene and AtMGT1 gene.In this study,to evaluate whether overexpression of AtMGT1-neMDH and AtMGT1 gene can ameliorate the absorption of calcium and magnesium ions.The variety of transfer and absorption with cadmium by transgenic Tobacco;explore the differences of toxicity and resistantce with cadmium by the transgenic Tobacco.Aim to find a better Cadmium hyperaccumulator of transgenic tobacco, the soil cadmium pollution on the restoration of great significance.The study of varieties in biomass of transgenic Tobacco shows that AtMGT1-neMDH gene and AtMGT1 gene can effectively enhance the biomass of tobacco.The gene transform into different chromosome location of tobacco induce different resistance of cadmium in transgenic tobacco,which is clue to the difference of genes functions and expression.The varieties ordinary tobacco that stress in different concentration of cadmium biomass changes was inapparent,the WT did not show the phenomenon of toxicity by the stress cadmium it also mean that the WT is better of cadmium tolerance.Stress by difference level of cadmium showed that the PA22 and PNA27 are better tolerance of toxic by cadmium,the PNA1 and PNA12 also show first promotion then inhibition,the PNA47,PNA57 show a continuing toxicity by different concentration of cadmium.The PA22 and PNA27 show better on the accumulation characteristics of Cadmium,obvious dose-response on the PNA1 and PNA12 growth in different concentration of cadmium,other species are also different degrees of increased biomass of Tobacco. The study of tolerance of cadmium in different transgenic Tobacco show that,the gene AtMGT1-neMDH and gene AtMGT1 can effectively enhance the tolerance and accumulation ability of cadmium in Tobacco.Deal with different concentration of cadmium,the concentration of cadmium in up-ground of transgenic tobacco is also different.Analyzed show that the concentration of cadmium in transgenic Tobacco significant higher than the wild type,but different in range.The over-expression of the gene recombination AtMGT1-neMDH and gene AtMGT1 have a positive role in accumulation of cadmium. Analysis by the bio-concentration factors and the uptake factor,we selected the PNA12, PNA27,PNA57 and PA22 as better accumulation of cadmium by transgenic Tobacco.The transit and absorption of calcium and magnesium in transgenic Tobacco indicate that AtMGT1-neMDH genetic recombination and gene AtMGT1 Tobacco can effectively enhance calcium and magnesium transfer and absorption.The gene AtMGT1 can effectively increase transit and absorption of Magnesium in transgenic Tobacco,and maintain at a high content, which increased tolerance of cadmium,protect the internal mechanism in transgenic Tobacco from the continuation of cadmium toxicity;the sufficient quantities of magnesium in transgenic Tobacco also promote tobacco on the absorption of calcium and cadmium stress with increased and enhanced.Abundance of calcium in tobacco is effective in control internal transshipment and storage of cadmium avoid the important organelle of tobacco toxic by cadmium.Analysis the interrelationship of calcium,magnesium and cadmium,in the stress of cadmium,there were significant differences in calcium content and the cadmium content in tobacco also the same phenomena with cadmium and magnesium.It means that the tolerance mechanism of cadmium is due to maintain adequate calcium and magnesium in tobacco.The mechanism of genetic recombination AtMGT1-neMDH and gene AtMGT1 resist the toxic of cadmium in transgenic tobacco is the absorption of magnesium from soil to promote the resistance of cadmium,protecting metabolism of tobacco,such as photosynthesis,which led the absorption of calcium in tobacco,to further strengthen Cadmium tolerance in tobacco and maintain high concentration of cadmium in the tobacco,aim to accumulate cadmium.