Effects Of DMA From Rice Root Exudates On Rhizosphere And Endosphere Microbial Community Composition

In addition to the factors of plants themselves,the microbial populations in the rhizosphere and roots also play a key role in the activation,transport and absorption of nutrients by plants.Therefore,the microbial population in the rhizosphere and endosphere is another angle to describe the life activities of plants,which is considered the second genome of plants.The gramineous crop rice（Oryza sativa L.）,under iron-deficiency conditions,chelates the fixed ferric iron(Fe³⁺)in the soil by secreting 2’-deoxymugineic acid（DMA）into the rhizosphere.The transfer of iron into rice roots through the Fe³⁺-DMA transporter is a typical way for Strategy II plants to absorb soil iron;in addition,rice adapts to the long-term flooded growth environment,and also has a set of Strategy I ways,that is,using the ferrous iron transporter takes up reduced iron directly from flooded soils.Rice mutants of key regulators of iron uptake Strategy II,osbhlh156 and iro2,lack the key upstream regulators of Strategy II,Osb HLH156 and IRO2,respectively,cannot synthesize and secrete DMA,and are therefore more sensitive to environmental iron deficiency.In this study,wild-type rice,osbhlh156,and iro2 mutant materials were used in paddy soils of two different origins to set up two kinds of culture conditions,flooding and upland,to simulate the soil environment of rice utilization type Strategy I system to absorb ferrous iron and Strategy II system to absorb ferric iron.The rhizosphere and endosphere microorganisms treated above were sampled and DNA extracted,and the following results were obtained through 16S r RNA amplicon sequencing and data analysis::（1）The results showed that soil conditions and planting patterns had a significant impact on the composition of microbial communities in the rhi zosphere and endosphere.In contrast,the effect of DMA in rhizospher e exudates was relatively slight but still not be ignored.The relative a bundance of Betaproteobacteria,Candidatus＿Saccharibacteria,Gammapro teobacteria,and Gemmatimonadetes were higher in the rhizosphere sam ples,and Proteobacteria and Actinobacteria were higher in the endosph ere samples.（2）Microorganisms colonize from soil to roots in the interaction with plants.By comparing the differences in microbial composition between the rhizosphere and endosphere,it was found that the number and diversi ty of microorganisms decreased during the process,indicating that the microorganisms were selected by different rice genotypes and participat ed in the life activities of rice in the process of co-evolution.（3）In this study,nine microbial groups,including Bradyrhizobium and Dictyobacter,were screened as biomarkers,which can distinguish whether there is DMA secretion in the rice rhizosphere.Through functional pr ediction,it was found that the ABC（ATP-binding cassette）transporter may participate in the iron transport process and function in plants a nd microorganisms.The results clarified the effect of DMA on the composition of microbial c ommunities in the rhizosphere and rhizosphere of rice and provided a data basi s for a comprehensive analysis of the role of microorganisms in response to ir on deficiency in rice.