Transcriptomic Study Of Aluminum Stress Response In Rice Affected By Rhizosphere Microorganisms Under Acidic Soil Conditions

Rice is one of the most important crops in the world,and aluminum stress in acidic soil severely limits rice growth and yield.The bacteria residing in the rhizosphere mitigate the effects of abiotic stress on plants through various mechanisms.The study of the regulation mechanism of rhizosphere microorganisms on the aluminum tolerance of rice is a necessary theoretical basis for maintaining the normal growth of rice in acidic soil and promoting grain crops by microbial regulation under the condition of acidic soil and aluminum stress the necessary.Based on soil samples from major rice-producing areas in China and rice pot experiments,this study explored the interaction between rhizosphere microorganisms and rice under different soil aluminum stress conditions.Transcriptome technology was used to analyze the effects of rhizosphere microorganisms on gene expression in rice leaves under different aluminum stress conditions,and to identify the key genes of rhizosphere microorganisms affecting the function of aluminum tolerance in rice.The main research conclusions are as follows:1.Effects of soil p H in paddy fields on the diversity and potential associations among Al-tolerant microorganismsThe analysis of the physical and chemical properties of paddy soil in the main producing areas in eastern China showed that when p H≤5.1,the exchangeable Al³⁺content increased significantly with the decrease of p H.Our study of Al-tolerant microbes in continental-scale paddy soils revealed that soil p H was the most important factor driving Al-tolerant bacterial community diversity and association patterns,and Al-tolerant microbes in acidic soils with high Al³⁺content exhibited more complex networks.2.Transcriptome analysis of rice leaf genes by bacterial colonization under aluminum toxicity stressThe results of the rice pot experiment showed that the rhizosphere inoculation of Rhodococcus and Pseudomonas aeruginosa had significant positive effects on the growth of rice plants compared with the rice plants without rhizosphere microorganisms,whether with or without aluminum stress.Transcriptomic analysis showed that the addition of rhizosphere microorganisms resulted in large changes in the transcriptome of rice leaves.Through GO（Gene Ontology）functional annotation and KEGG（Kyoto Encyclopedia of Genes and Genomes）pathway enrichment analysis of differentially expressed genes,it was found that different functions were regulated in Al+SN vs Al+CK and Al-SN vs Al-CK contrasting groups,which may represent the effects of rhizosphere microorganisms on rice under aluminum stress.3.Effects of rhizosphere microorganisms on key functions of rice under Aluminum stressThrough functional enrichment analysis,mainly focused on the changes in functions related to growth and stress resistance,such as photosynthetic respiration and carbohydrates,organic acids,cell walls,secondary metabolism,and redox.There were significant differences in each function between the Al+SN vs Al+CK and Al-SN vs Al-CK contrasting groups.In terms of growth,observed the regulation of photomorphogenesis and chloroplast-related functions of rice leaves by rhizosphere microorganisms under aluminum-free stress conditions.Among the functions related to respiration,rhizosphere microorganisms had little effect on rice.Under the condition of aluminum stress,the inhibition of photosynthesis was observed,and the transport and catabolism of carbohydrates were down-regulated.In terms of stress resistance,rice regulated the metabolism and synthesis of abscisic acid under the condition of aluminum-free stress.The general up-regulation ofβ-glucan biosynthesis,cellulose biosynthesis,cellulose synthase activity,and plant-type primary cell wall biogenesis appears to support the promotion of rice plant growth by rhizosphere microorganisms.Under conditions of aluminum toxicity,rice plants may interact with microorganisms,resulting in higher expression of abscisic acid,carboxylic acid,cinnamic acid,pyruvic acid,and alanine-related genes in rice plants.The biosynthesis of lignin,anthocyanin,and flavonoids was significantly up-regulated after rhizosphere microbial inoculation,which may be beneficial for rice to cope with oxidative stress caused by aluminum stress.4.Screening of key genes for aluminum tolerance in rice affected by rhizosphere microorganismsThrough the classification and discussion of different UP-and DOWN-regulated genes involved in growth and stress tolerance functions in Al+SN vs Al+CK and Al-SN vs Al-CK contrasting groups.This study identified several key genes that are regulated by rhizosphere microorganisms and promoted aluminum tolerance in rice.Os01g0151500,ADC1,and SAPK9 were related to antioxidant defense,suggesting that rhizosphere microorganisms may promote rice growth by reducing the accumulation of reactive oxygen species and alleviating oxidative stress.SAPK9 and Os WRKY24 are regulated by plant hormones and positively regulate plant disease resistance by activating defense gene expression.Os08g0246400 mediates oxidative phosphorylation in mitochondria and is involved in ATP synthesis.GA2ox3 has been reported to be involved in the metabolism of gibberellin and mediate plant development.DPE1 is involved in starch synthesis in rice endosperm and is critical for plant development,crop quality,and nutrition.