Mechanisms Of Cadmium Effects On Oryza Sativa L. And Rhizosphere Microenvironment Based On Metabolomics And High-throughput Sequencing

Cadmium(Cd)is the most prevalent and toxic metal contaminant.Rice(Oryza sativa L.)is one of the most important grains in the world and has a strong absorption capacity for Cd.Cd not only causes disruptions in the physiological state of rice leading to quality decline,but also enters the human body through the food chain enrichment,seriously endangering health.Metabolomics platforms and high-throughput sequencing technology are powerful tools for studying the changes of in metabolite composition and content,and structural succession of microbial communities.Exploring the changes and response patterns of metabolites and microbial communities in certain spatial and temporal environments can provide a theoretical basis for further research on plant growth and regulatory mechanisms in response to environmental stresses.Through non-targeted metabolomics technology and high-throughput sequencing technology,this project explores the mechanisms of heavy metal abiotic stress on plants and inter-root microenvironment by focusing on the interaction of heavy metal-plantinter-root environment,and reveals the potential impact of heavy metal Cd on crops and environment.This will provide a better understands of the characteristics,extent and impact mechanisms of Cd contamination,so as to provide a scientific basis and technical support for protecting the safe of crop production and ecological environment security.The main contents and results are as follows:(1)A non-targeted metabolomics approach was used to study the effects of Cd on growth status and metabolism of rice in order to elucidate the response mechanisms of rice to resist the stress.For different tissue samples of rice,the results showed that the surface microstructure and plant physiological activity of root,stem and leaf tissues were significantly affected by different concentrations of Cd treatment by means of scanning electron microscopy(SEM)and enzyme marker.In addition,to further investigate the metabolic response of stress,non-targeted metabolomics was used to study the changes of metabolites in rice.It was found that the contents of alkaloids,flavonoids,organic acids,lipids,terpenoids,sugars and glycosides in root,stem and leaf changed significantly.In particular,especially in root and stem tissues,the contents of flavonoids,sugars and glycosides were positively correlated with Cd concentration.KEGG analysis showed that Cd stress significantly affected the biosynthesis and metabolic pathways of amino acids,flavonoids,etc.in rice.(2)A liquid chromatography-mass spectrometry instrument(LC-QTOF/MS)was used to study the mechanistic response of rice root secretions under Cd stress,and to understand the external detoxification strategy of plant adaptation to the environment.Metabolic analysis showed that Cd stress significantly altered the metabolic characteristics of rice root secretions.Most of the alkaloids,lipids,flavonoids,phenolics and organic acids showed positive responses under different concentrations of Cd treatment.The results of metabolic pathways showed that the metabolic pathways of tyrosine metabolism,purine metabolism,and isoquinoline alkaloid biosynthesis were significantly affected in rice root secretions.(3)A 16 S rRNA high-throughput sequencing technology was used to investigate the effects of inter-root/root surface soil microbial communities on rice growth and explore the interactions between plant and root soil microbial communities.By studying the microbial community structure on inter-root/root surface soil of rice to reveal the effect of Cd and rice secretions on soil microbial communities.The results indicate that there has been a significant change in soil enzyme activity,proving that the soil microbial system has been affected.The abundance and diversity of soil microbial communities showed that Cd stress altered the structure of soil microbial communities in the rice root system(p < 0.05).Proteobacteria and Planctomycetota were the dominant phyla in the inter-root/root surface soil.And some beneficial rice microbial communities such as Bacillus,Pir4＿lineage,Cyanobacteria and Roseobacter＿clade＿CHAB-I-5＿lineage were identified.Functional predictions showed that Cd significantly affected the inter-root/root surface microbial community functions and developed different metabolic strategies to adapt to environmental stresses.