Investigation On Microbial Composition And Response Mechanism In The Rhizosphere And Roots Of Maize Under Different Phosphorus Levels

Although there are a large number of reports on maize rhizosphere microbes,there are no reports about the analysis of microbe composition and gene function in maize rhizosphere and inside roots at the same time.In this paper,on the basis of mining the composition of endophytes from plant transcriptome data established by our lab,I further established the endophytes' functional gene analysis technology to systematically study the changes in the microbial composition in the rhizosphere and roots of maize under different phosphorus levels.The functional genes related to the phosphorus cycle are analyzed,and the microbial function is identified in combination with the isolation and culture technology.The main results are as follows:1.The analysis of maize rhizosphere microorganisms under different phosphorus levels shows that the bacterial content is the highest,reaching 95%,of which the Proteobacteria and Actinobacteria account for ?70%;the fungal content is more than 3%,of which the Ascomycota and Basidiomycota account for 60-97%;viruses and protozoa each accounts for about 0.5%.The symbolic microorganisms in the rhizosphere with high phosphorus levels are Acidobacteriales,and the symbolic microorganisms in the rhizosphere with low phosphorus levels are Nitrososphaerales.2.Maize root endophytes are mainly fungi,accounting for more than 60%,and the two most abundant are Exserohilum turcicum and Rhizophagus irregularis.A total of 5470 species of rhizosphere microorganisms were detected,and 819 species of rhizophytes were detected,of which 756 species were shared by the two.At medium phosphorus level,some probiotics in maize root may have inhibitory effect on pathogens,resulting in low content of pathogens such as Exserohilum turcicum.3.The metabolic pathway analysis showed that the low phosphorus treatment was mainly associated with the synthesis of antibiotics;the metabolic pathways under high phosphorus treatment were related to amino acid synthesis or metabolism.The analysis of the phosphorus cycle function gene of three types,including phosphorus activation,phosphorus uptake and phosphorus starvation response regulation of phosphorus nutrients,showed that the content of phosphorus activation-related genes increased significantly at high and medium phosphorus levels.4.A technique to analyze endophytes' functional genes from plant transcriptome data was established,and the method for analyzing plant endophytes' functions was perfected.Metabolic pathway analysis showed that endophytes in root were mainly related to peptidoglycan biosynthesis at middle phosphorus level;Under low phosphorus level,inhibition of carbon metabolism pathway leads to growth retardation,inhibition of isoquinoline alkaloid synthesis and other metabolic pathways,leading to infection of some pathogens.5.408 strains of bacteria were isolated from the maize rhizosphere and roots.After planting maize inoculated according to the source classification,it was found that the dry weight of maize roots which was inoculated with rhizosphere bacteria from medium phosphorus treatment increased significantly under medium phosphorus treatment.