The Functions Of Melatonin On Cadmium Stress Resistance In Tomato

Nowadays,because of the soil polluted by heavy metals,the quality of vegetable is inevitably affected,and the safety production of vegetable has become a serious problem,waiting to be solved urgently.Issues like how to deal with heavy metal pollution and detoxify under heavy metal like cadmium stress are worth thinking today.Melatonin is a natural small molecule with the construction of indole amine compound,which is synthesized in most plants and plays an important role in stress resistance.In this paper,tomato was used as material.First,we constructed TRV-PCs(silence phytochelatin synthesis gene PCs),TRV-COMT(silence melatonin synthesis gene COMT)and TRV-COMT-PCs(both two genes)to study the function of COMT and PCs in tomato resistance under Cd stress.Then,we studied the effects of melatonin made on physiology and biochemistry in tomato under Cd stress.Finally,we studied the mechanism of miR169b targeting TDC genes under Cd stress to regulate endogenous melatonin synthesis in plants The main results are as follows:1.To study the function of COMT gene and PCs gene in tomato cadmium stress resistance and the role of melatonin in relieving tomato cadmium stress.The experiment used the TRV,TRV-PCs,TRV-COMT and TRV-COMT-PCs tomato plants as materials.The COMT gene regulates the synthesis of endogenous melatonin in tomato plants,alleviates the damage caused by Cd stress to tomato plant growth and development,maintains chlorophyll synthesis,and maintains cell stability by removing ROS and MDA,reduces the degree of lipid peroxidation of cell membranes and free radicals in plant cells and restores photochemical efficiency,thereby enhancing tomato Cd stress resistance;PCs gene can also alleviate tomato growth inhibition under Cd stress to a certain extent by regulating the synthesis of tomato plant chelating peptides.The amount is reduced and the adverse effects of chlorophyll synthesis are blocked,and it is detoxified by chelating Cd and other methods,thereby enhancing the Cd stress resistance in tomato plants.In addition,pretreatment of exogenous melatonin can partially restore the Cd resistance of COMT-silent plants,and at the same time,it can also increase the Cd resistance of PCs-silent plants,verifying the positive role of melatonin in relieving tomato Cd stress.2.To study the effect of melatonin on tomato plant physiology and biochemistry under Cd stress.Melatonin regulates the redox balance in tomato plants by affecting GSH/GSSG and AsA/DHA,enhances the antioxidant capacity of tomato plants and maintains the redox homeostasis in the body.The measurement of H~+ATPase activity and proline content showed that melatonin may play a role in regulating the osmotic balance of tomato cells under Cd stress,so as to reduce the effect of Cd on the transport channel and membrane permeability,then facilitating tomato cells absorb,transport and accumulate nutrients.At the same time,melatonin can regulate the contents of macronutrients like K,Ca,Mg and micronutrients like Fe,Cu,Zn,Mn in tomato leaves under Cd stress,maintaining nutrient balance and intracellular physiological and biochemical functions,and thus alleviate the effects of Cd stress in tomatoes.3.To study the mechanism of miR169b targeting TDC genes and regulating endogenous melatonin synthesis under Cd stress.Firstly,it was verified by HPLC-MS and qRT-PCR that Cd stress promoted the expression of endogenous melatonin and TDC genes in tomatoes,and the expression of miR169b was significantly reduced under Cd stress.Then,the sequence that miR169b complements with TDC gene was selected by sequence alignment.We constructed miR169b-OE vector,and tobacco dual luciferase was performed.In tobacco leaves,we co-expressed miR169b-OE and TDC-LUC vectors,LUC fluorescence decreased by approximately 18.3%,and when we co-expressed miR169b-OE and TDCm-LUC vectors,LUC fluorescence decreased by approximately 56.4%.After mutating the miR169b/DC pairing sequence,miR169b may not be able to bind to TDC,and then could not cut the sequence then inhibit translation.The experimental results showed that miR169b is likely to be able to directly target TDC,which would affect the transcription and translation of TDC.