Analysis Of The Symbiotic Mechanism Of Arbuscular Mycorrhizal Fungi And Maize Roots Regulated By Maize MSERG3 Gene

Arbuscular mycorrhizal fungi(AMF),as an endosymbiotic fungus,have been associated with higher plants on the earth for 460 million years.Symbiotes form a symbiotic organization with the vegetative roots of higher plants.Arbuscular mycorrhizal fungi can have symbiotic relationships with more than 80% of higher terrestrial plants.Arbuscular mycorrhizal symbiotes can provide plants with inorganic phosphorus that cannot be taken up by themselves,and plants in return provide them with carbon sources such as fatty acids and sugars.Rhizophagus irregularis(R strain)arbuscular mycorrhizal fungi is a common type of endosymbiotic fungus that is widely studied at present.It is often used in symbiosis with higher plants to study the mechanism of action.At present,the symbiont of Ti-transgenic hairy root of carrot and arbuscular mycorrhizal fungi,which are then cultivated by a plate system.In order to explore the endogenous metabolic changes of the host after the symbiosis of arbuscular mycorrhizal fungi,hereby integrating the most advanced non-targeted metabolomics and Label-free lipidomics for mycorrhizal fungi and carrots under aseptic culture conditions Symbiotic mycorrhizal root formation and carrot roots cultured under aseptic conditions were analyzed for metabolome differences.This system can exclude the effects of other external factors on the symbiosis of arbuscular mycorrhizal fungi and carrot roots,so as to clearly and accurately study the symbiosis of the two.Changes in metabolites and lipids.The results showed that after the symbiosis of arbuscular mycorrhizal fungi and carrot roots,the overall carbon metabolism was enhanced,and the aspartate-mediated ABC lipid transporter cooperated with the plasma membrane signal transduction molecule phosphatidylserine(PS)and intracellular signal transduction.The molecules phosphatidylinositol(PI)and phosphatidylinositol phosphate(PIP)are up-regulated together.The specific metabolic changes of plasma membrane and intracellular signal transduction after arbuscular mycorrhizal fungi were revealed.The classic model states that the host secretes strigolactone to recruit arbuscular mycorrhizal fungi,while the arbuscular mycorrhizal fungi return to the host with mycorrhizal signal molecules.This study first proposed that after the symbiotic structure was completed,PS,PI,and PIP,which are members of the phosphatidylinositol signaling pathway,were involved in mediating symbiotic signal transduction.Earlier studies in this laboratory have shown that the arbuscular mycorrhizal fungi of the R strain can effectively improve corn biomass and stress resistance after forming a symbiotic relationship with corn.In this study,five genes MSERG1-5 related to controlling the symbiotic efficiency between maize and mycorrhiza were screened by GWAS,and the regulatory mechanism was analyzed by genetic analysis and functional verification.After the W22 wild type modified MSERG3 T-DNA insertion mutant and W22 wild type were inoculated with arbuscular mycorrhizal fungi,the symbiosis efficiency of the mutant was significantly higher than that of the wild type.This suggests that MSERG3 negatively regulates the symbiotic efficiency of corn and mycorrhiza.Meanwhile,arbuscular mycorrhizal fungi provide inorganic phosphorus to plants.Field experiments have shown that,compared with wild-type inoculations of R strains,inoculation of arbuscular mycorrhizal fungi,the inorganic phosphorus content in leaves and roots decreased significantly,and the inorganic phosphorus content in stems increased significantly.To reveal the relationship between increased symbiosis efficiency and phosphorus metabolism,transcriptome sequencing showed that a large number of genes related to phospholipid transport were significantly up-regulated.The changes of phosphatidylcholine in roots,stems and leaves were consistent with the changes of total inorganic phosphorus.Combining changes in inorganic phosphorus and phospholipids,this indicates that MSERG3 not only negatively regulates the symbiotic process of arbuscular mycorrhizal fungi and corn,but also may regulate symbiosis by affecting phosphorus transport.Because MSERG3 regulates phosphorus uptake and transport,phosphorus deficiency in MSERG3 mutants leads to host recruitment of mycorrhizas,which ultimately improves symbiosis efficiency.To sum up,this study has preliminarily constructed MSERG3 to regulate corn and arbuscular mycorrhizal fungi through genetic verification and functional analysis of the MSERG3 gene that controls the symbiosis of corn and arbuscular mycorrhizal fungi.The molecular regulation network of root fungi,through the cross-combination of omics,molecular biology,and bioinformatics,can obtain a lot of reference biological information,and then lay a solid theoretical foundation for the genetic improvement of arbuscular mycorrhizal fungi symbiosis in corn crops.