Preliminary Development Of A New Method For The Analysis Of Endophytic Microorganisms And Investigation On The Microbiome Of Maize Roots Under Cadmium Stress

Although a large number of previous reports have analyzed the composition of maize rhizosphere microorganisms as well as isolation and cultivation of maize endophytes,the simultaneous analysis of microbial composition and gene function in maize rhizosphere and endophytes has not been reported due to the limitations of research and analysis techniques.In this paper,we first developed data analysis techniques to mine the composition of endophytic microorganisms from plant transcriptomes,and then we comprehensively analyzed the changes of microbial composition and their functional genes related to microbial metabolism in maize roots under Cd treatment,and finally identified the microbial functions combined with isolation and culture technology.The main results were as follows.1.The data analysis technology of mining endophytic bacteria species composition from plant transcriptome was established,which can obtain plant gene expression information and microbial composition information at the same time.2.In maize root endophytes,the average content of bacteria accounted for 19.87%,fungi77.59%,protozoa 1.98%,viruses 0.55%,and the content of fungi in the maize endophytes increased under Cd treatment.3.The average content of bacteria in maize rhizosphere microorganisms accounted for94.94%,fungi 3.8%,protozoa 0.4%,and viruses 0.7%.More than 70% of bacteria belong to the phylum Proteobacteria.After Cd stress,the microbial content of multiple proteobacteria increased significantly.4.There are 1413 genera of rhizosphere microorganisms and 600 genera of endophytes,of which 399 genera are shared by the two.After Cd treatment,the composition of the microbial communities in the rhizosphere and inside the roots of maize were affected.Among them,the contents of Burkholderia,Oxalobacter,Massilia and other proteobacteria in the maize rhizosphere has increased.The microbial changes of endophytes were related to fungi.Of them,sordariomycetes of ascomycetes has increased.5.Under Cd treatment,maize endophytes are mainly related to basic metabolism such as growth,while cytochrome P450 and phenazine biosynthesis in rhizosphere microorganisms may be related to Cd resistance.A variety of Cd resistance genes were detected in maize rhizosphere microorganisms,among which czcA,czcB,czcC,czcD,czcE,czcR,czcS,and czcP increased significantly after being stressed by Cd,while the control was almost undetectable.No Cd-related heavy metal resistance genes were detected in the microorganisms inside the corn roots.6.A total of 70 strains of bacteria were isolated from the roots and rhizosphere soil.The combined inoculation of endophytic bacteria isolated from maize roots significantly reduced the harmful effect of Cd.