Morphological And Physiological Indicators And Transcriptome Analyses Reveal The Mechanism Of Selenium Multilevel Mitigation Of Cadmium Damage In Brassica Juncea

Cadmium(Cd)is a common agricultural soil pollutant and a highly hazardous heavy metal.Cadmium is enriched through plants,disrupting the homeostasis of plant cells,and entering the human body through the food chain,posing a threat to human health.Selenium(Se)is an essential trace element for animals and humans,and has a biological strengthening function on plants.Se has a antagonism effect on heavy metals,and can inhibit the absorption and transport of cadmium when interacting with cadmium.Brassica juncea L.is an important oilseed crop that accumulates cadmium and is commonly used to study the principles of cadmium enrichment.This study used different concentrations of cadmium chloride and Na2 Se O3 to treat mustard.Then the physiological indexes,root morphology and transcriptome analysis were determined to reveal the mechanism of Se reducing the inhibition and toxicity of Cd on mustard.The results are as follows:1.Cd to some extent inhibited the growth of mustard seedlings,while Se alleviated the inhibitory effects of Cd on seedling biomass,root length,and chlorophyll.2.Se can also alleviate Cd induced oxidative stress,reduce intracellular MDA content,increase Vc content,increase GPX activity,reduce APX and CAT enzyme activity,and alleviate Cd induced oxidative damage to mustard by regulating antioxidant content and antioxidant enzyme activity.3.Optical and laser confocal microscopy observations of root morphology indicate that Cd stress causes damage to the root cells of mustard seedlings,disrupting the integrity of cell membranes.The addition of Se alleviates the toxic effects caused by Cd,promotes root development to a certain extent,restores root hair growth,and promotes nutrient absorption and utilization,thereby promoting aboveground growth.4.The content distribution and transport coefficient of Se and Cd in the upper and lower parts of the ground showed that the content of Se and Cd in the upper parts of the ground decreased when treated together with selenium and cadmium compared with that when treated alone.Both of them had antagonism,preventing the transport of two elements from the ground to the upper parts of the ground;The main forms of organic selenium in the aboveground and underground parts are Se Me Cys and Se Met.It is speculated that there is a formation of selenium cadmium complexes to inhibit the upward transport of Cd,and different selenium forms have different effects and mechanisms on alleviating Cd stress.5.According to the transcriptome data and the correlation analysis of selenium and cadmium content,it can be inferred that the divalent cation transporter DCT1 is involved in the separation of Cd in vacuoles,CAL1 is related to the chelation of Cd in the cytoplasm,and the ZIP4 transporter reduces the transport of Cd from underground to above ground.These results indicate that selenium improves the antioxidant system,slows down root tip damage caused by Cd,increases the biomass of Indian mustard under Cd stress,enhances the absorption capacity of root cells for Cd,and reduces the activity of Cd transporters,thereby reducing the damage of Cd to plants and reducing its transport from underground to aboveground.