Effects Of Nitrogen And Phosphorus On Gene Expression Of Poplar Under Cadmium Stress And Genetic Transformation Of Hma3 Overexpression Vector

Forests are the ecosystem on which humans depend and have important ecological benefits.The situation of heavy metal pollution in soil is severe,which seriously imperil the stability and health of forest ecosystems.Previous studies on heavy metal pollution have focused on farmland and have paid less attention to forests.Populus is a candidate for repairing heavy metal contaminated soil.The upper part of poplar can accumulate large biomass in a growing season,so that makes the total accumulation of cadmium in poplar far exceeds that of herbaceous hyperaccumulators,and has great potential for phytoremediation of heavy metal pollution.Appropriate nitrogen and phosphorus nutrition can improve the resistance of plants to stresses heavy metal stress.However,previous studies have focused on the physiological indicators of crops.In this paper,84K poplar?Populus alba×Populus glandulosa?was used as experimental material to study the alleviation of nitrogen and phosphorus nutrients on cadmium stress at gene expression level.According to the results,the addition of nitrogen and phosphorus nutrients changed the expression of antioxidant,cadmium uptake and transport,and nitrogen metabolism related genes of 84K poplar.The use of nitrogen nutrition increased the expression of most genes,enhanced the resistance of plants to Cd stress,and alleviated the toxic effects of Cd on plants,however the effects of different nitrogen forms were also different.The effect of ammonium nitrogen was better than that of nitrate-nitrogen.The use of phosphorus also affects the expression of genes to varying degrees.Phosphorus might affect the absorption of cadmium by changing the soil pH and Cd activity,to some extent also showed a certain alleviation effect on plant Cd toxicity.Previously,in the research of poplar genetic engineering,mainly improved traits were insect resistance,disease resistance,lignin content reduction,herbicide resistance,salt and alkali resistance,etc.,but little research on heavy metal stress.Heavy metal ATPases?HMAs?are heavy metal transporters that transport excess metal ions by consuming ATP.The HMA3 gene is localized on the tonoplast membrane,it can transport Cd²⁺,Zn²⁺,and Pb²⁺to the vacuole to isolate and participate in the transport and detoxification of heavy metal ions.However,there were few reports on HMA3 gene.Therefore,this study uses84K poplar as the target,clone the HMA3 protein coding sequence of 84K poplar,and complete the construction of HMA3 overexpression vector.There are many factors affecting the efficiency of genetic transformation of poplar,such as medium type,hormone,agrobacterium concentration,infection time and explant.In this experiment,the leaf scratching method,leaf inoculation method,differentiation medium,rooting medium,etc.were screened.According to the result,vertical main vein of the leaf surface was better than the leaf block,and the blade face down was better than the back of the blade.The best leaf differentiation medium was MS+0.5 mg.L^-1 6-BA+0.05mg.L^-1 NAA,and the rooting medium was 1/2MS+0.5 mg.L^-1 IBA.In this experiment,4strains were normally rooted by antibiotic screening.