Ionomic Analysis And Molecular Mechanism Of Rice Response To As(Ⅲ) Stress

Arsenic(As)is a strong carcinogenic metal prevalent in the environment,and rice(Oryza sativa)is easily enriched with As in the soil and enters the human body through food chain transfer,posing a great health risk.To investigate the complex mechanism of ion homeostasis regulation in plants under arsenic stress.In this study,16 main planted rice varieties in the characteristic arsenic-contaminated region were treated with As(Ⅲ),the major As form in paddy soil,and the phenotypic characteristics of different varieties of rice in response to As stress and the ionome of each tissue probe were analyzed,and further the differentially expressed gene enrichment pathways of screened As-tolerant and As-sensitive varieties in response to As(Ⅲ)stress were investigated by means of bioinformatics analysis.We further investigated the transcriptional regulation of As(Ⅲ)stress in the screened As-tolerant and As-sensitive cultivars by bioinformatics analysis,elucidated the transcriptional regulation of As(Ⅲ)stress in the two rice species,and revealed the molecular mechanism of As enrichment differences in rice by correlating ionome changes with arsenic accumulation.The main findings are as follows:1.The effect of As(Ⅲ)stress on the growth phenotype of rice seedlings.The test rice showed an overall pattern of increasing root length followed by decreasing plant height and weight inhibition under 2 mg·L-1 and 4 mg·L-1 As(Ⅲ)stress conditions,while the plant length of M1 and M8 varieties increased under 2 mg·L-1 stress conditions,indicating that As(Ⅲ)had a significant effect on the phenotypic growth of rice,indicating that As(Ⅲ)had significant effects on the phenotypic growth of rice.the L5 variety had the lowest percentage of plant length reduction under 4 mg·L-1 stress conditions and the lowest percentage of plant weight reduction under both stress conditions,and M2 variety had a greater percentage of reduction in root length,plant height and plant weight after As(Ⅲ)stress,and a greater percentage of reduction in root length than 50% was an arsenic sensitive variety.M2 not only had a reduced number of leaves and yellowing of new leaves at high concentration of stress,but also was found to produce more reactive oxygen species after As(Ⅲ)stress.2.Ionomics study of rice in response to As(Ⅲ)stress.The change characteristics of Mn,B,Cu,Zn,Mo,Sr,Al,Cr,Ni,As,Ba,Pb,Co,and Cd in the shoot and root tissues of rice seedlings in response to different As(Ⅲ)concentration stresses were found to vary significantly among different tissues after stress.The As accumulation in different varieties of rice varied significantly,and the As content in the roots was significantly higher than that in the shoots,and the As accumulation in all varieties increased with the increase of stress concentration.The transfer coefficient(TF)did not increase with increasing root arsenic uptake in all varieties,but As accumulation in rice shoot tissues was closely related to the TF value.Sr,Al,Cr,Ba,Pb,Co,and Cd had similar distribution to As and were higher in roots than in shoots,while B,Mn,and Mo had opposite distribution to As and were higher in stems and leaves.HCA and PCA analyses showed a clear separation between roots and shoots.Stress concentration and rice varieties together affected ion group distribution in each tissue.Toxic elements such as As,Al,Co,Sr,Ba,and Pb tended to be more enriched in root tissues of arsenictolerant varieties,while nutrient elements B,Mn,and Mo tended to be enriched in shoots.As had a greater effect on ion transport in roots under high concentration stress.As could alter the correlation in rice tissues.Compared with the control group,the correlations in the stress group were more variable.as showed a significant negative correlation(P<0.05)with B,Mn,and Mo,which may inhibit As uptake;and a significant positive correlation(P<0.05)with Al,Co,Ni,Sr,Ba,and Zn,indicating that these elements have a positive effect on As uptake and translocation.3.Transcriptomic study of rice in response to As(Ⅲ)stress.The number of differentially expressed genes in the Treat L5_vs._Control L5 and Treat M2_vs._Control M2 comparison groups differed significantly,and Treat L5_vs._Control L5 was mostly up-regulated expression,while Treat M2_vs._Control M2 down-regulated more differentially expressed genes than up-regulated expression.GO and KEGG enrichment analysis showed that genes related to plant growth and development and ion transport and fixation were significantly enriched.Genes related to growth and development were down-regulated in both comparison groups;indicating that plant growth and development were inhibited,while genes related to ion transport were upregulated in the Treat L5_vs._Control L5 comparison group,indicating that L5 has a stronger As transport capacity.Nutrient element-related genes were down-regulated in the Treat M2_vs._Control M2 contrast group,whose nutrient uptake was inhibited under As(Ⅲ)stress conditions.