Function Of Dopamine In Regulating Apple Heavy Metal Cadmium And Copper Stress

With its crisp taste and rich nutritional content,apple has become the best-selling healthy fruit on the market today.Shaanxi is the largest province for apple cultivation in China.In 2020,the apple planting area of Shaanxi orchards will reach 11 million acrers,and the output will be as high as 11.8521 million tons.However,at present,the problem of heavy metal pollution in farmland and orchard soil in Shaanxi is becoming more and more serious,especially cadmium pollution and copper pollution,which have buried hidden dangers for apple production.Dopamine is a kind of catecholamines.It is not only the precursor of melanin synthesis,but also participates in the scavenging of reactive oxygen species（ROS）as an antioxidant,and is also involved in adjustment functions of various physiological and metabolic activities of plant cells as a signaling molecule.The biological function of dopamine in plants has many similarities with the detoxification mechanism of plants under heavy metal stress,but there are few reports on the function of dopamine in regulating apple heavy metal copper（Cu）and cadmium（Cd）stress.Therefore,in this study,Malus hupehensis Rehd and’Gala’（Malus×domestica Borkh.cv.Gala,GL-3）with over-expressed tyrosine decarboxylase（MdTyDC）apple plants were used as test materials,and were treated with Cu and Cd stress respectively.From the two aspects of dopamine’s exogenous regulation and endogenous anabolism,the effect of dopamine on apple’s resistance to heavy metal poisoning and the reduction of heavy metal accumulation in apple plants were studied,and its possible mechanism of action was discussed,which is a scientific and effective method for orchard management and production.The prevention and control of heavy metal poisoning has laid a theoretical foundation.The main findings are as follows:1.Malus hupehensis Rehd,wild-type‘GL-3’and MdTyDC transgenic‘GL-3’apple plants were used as experimental materials to study the function of dopamine in regulating apple’s response to Cd stress.The results showed that dopamine can reduce the toxicity of Cd stress to apple plants and increase the biomass of apple plants under Cd stress.As a strong antioxidant,dopamine directly participates in ROS scavenging,while increasing the enzymatic activities of superoxide dismutase,peroxidase,and catalase.Dopamine can also enhance the root vitality,photosynthesis and other physiological activities of apple plants by regulating changes in amino acids and hormones content.Dopamine also reduces the transportation of Cd to the shoot by regulating the expression of genes related to Cd²⁺metabolism,and promotes Cd efflux and detoxification.2.Malus hupehensis Rehd,wild-type‘GL-3’and MdTyDC transgenic‘GL-3’apple plants were used as experimental materials to study the function of dopamine in regulating apple’s response to Cu stress.The results showed that dopamine positively responded to Cu stress,significantly reduce the damage of high concentrations of Cu²⁺/Cu⁺to the roots and leaves of apple plants,and appropriately increasing the biomass under Cu stress.Dopamine can improve the ROS scavenging ability of the antioxidant system of apple plants,and can also regulate the content of amino acid and hormones in the body.In addition,dopamine can strictly control the metabolic processes of Cu²⁺/Cu⁺absorption,transport and detoxification by regulating the expression of genes related to Cu metabolism in apple plants.