Investigation Of AMF Symbiosis Induced Changes And Mechanisms Of Changes In Root Exudates Of Maize Based On Multi Omics Approaches

Maize(Zea mays L.)is an important food crop and plays an important role in agricultural production.The demand for output makes people focus more on the above ground part,ignoring the in-depth study of the underground part.Root system plays a great role in the growth of maize,which will have an important impact on the yield and quality of maize.During the growth of maize,root exudates and other metabolites will be released into the soil through the root tip.Root exudates interact with the changes of maize growth environment.It is the medium for material exchange,energy conversion and information communication between plants and soil,and plays the role of communication bridge between maize and soil.Arbuscular mycorrhizal fungi(AMF)are important soil microorganisms in the ecosystem.They can establish a symbiotic system with plants and affect plant growth and development.Inducing the change of plant root exudates is an important reason for AMF symbiosis to affect plant physiology and biochemistry and rhizosphere soil microecology.In this research,"Zhengda 619" maize was used as the host,colonizationed with Claroidoglomus etunicatum as the experimental treatment and not colonizationed with AMF as the control treatment.The physiological and biochemical changes,root exudates and microecological changes of maize rhizosphere soil after colonizationed of C.etunicatum were researched by pot method;At the same time,the molecular mechanism of AMF symbiosis induced changes in maize root exudates was studied.The main results are as follows:1.After AMF colonization,the plant height,stem diameter,leaf area,dry matter accumulation and other biomass of maize were significantly improved,as well as photosynthesis,root activity and nutrient accumulation.AMF colonization significantly affected the root morphology of maize.After AMF colonization,the total root length,root tip number and root surface area of maize increased significantly,and the root diameter decreased significantly.The content of endogenous hormones in maize roots also changed significantly after AMF colonization.After AMF colonization,the contents of abscisic acid(ABA),methyl jasmonate(Me-Ja)and brassinosterol(BR)in maize roots decreased significantly,and the contents of zeatin(ZR),indoleacetic acid(IAA)and gibberellin(GA3)increased significantly;The difference of endogenous hormone content was the most significant in the filling stage of maize growth.The results of correlation analysis showed that there was a significant correlation between the content of endogenous hormones in maize roots and the morphological changes of maize roots.2.Maize root exudates are mainly organic nitrogen compounds,organic heterocyclic compounds,organic acids and their derivatives;After AMF colonization,there was no specific difference in the components of maize root exudates,but there were differences in the content of each component,among which there were significant differences in the relative content of 35 compounds.AMF colonization significantly affected the content of organic acids in maize root exudates.After AMF colonization,the contents of p-hydroxybenzoic acid,vanillic acid,syringic acid,citric acid,p-coumaric acid,ferulic acid and chlorogenic acid increased significantly,and the contents of succinic acid,maleic acid and tartaric acid decreased significantly;The difference of organic acid content was the most significant in the filling stage of maize growth.AMF colonization reduced the allelopathic effect of maize root exudates on the seed germination and growth of recipient plants,and improved the inhibitory effect of maize root exudates on the mycelial growth of soil borne diseases.3.After AMF colonization,the enzyme activity of maize rhizosphere soil increased significantly,and AMF colonization improved the diversity of bacteria and fungi in maize rhizosphere soil.AMF colonization increased or decreased the species distribution and species abundance of soil microorganisms in maize rhizosphere,affected the interaction of soil microorganisms,and promoted the balanced development of soil bacterial community in maize rhizosphere.Syringic acid,citric acid and p-coumaric acid in maize root exudates significantly affected the bacterial abundance of maize rhizosphere soil;Butyric acid and p-coumaric acid significantly affected the fungal abundance in maize rhizosphere soil.Cellulase,polyphenol oxidase and neutral protease in maize rhizosphere soil were significantly correlated with the abundance of bacteria in maize rhizosphere;Dehydrogenase and sucrase were significantly correlated with the abundance of rhizosphere fungi in maize.4.AMF colonization significantly affected the expression of genes and proteins in maize roots,resulting in significant differences in metabolite content in maize roots.After AMF colonization,4416 genes were differentially expressed in maize roots,of which 1026 genes were up-regulated and 3390 genes were down regulated;211 proteins were differentially expressed,of which 118 proteins were up-regulated and 93 proteins were down regulated;The contents of 261 metabolites were significantly different,of which 213 metabolites increased and48 decreased after C.etunicatum colonization.It mainly involves amino acid metabolism,endogenous hormone and organic acid synthesis,biosynthesis of secondary metabolites,energy metabolism,nucleotide metabolism α-Linolenic acid metabolism and other metabolic processes.5.After AMF colonization,there are 14 common metabolic pathways associated with transcriptome,proteome and metabolome,including 8 metabolic pathways highly related to the change of organic acid content in root exudates,mainly including purine metabolism,pyrimidine metabolism,multiple amino acid metabolism,glycerophosphate metabolism,linoleic acid metabolism and α-Linolenic acid metabolism.137 key genes,8 key proteins and 12 key metabolites were highly correlated with the change of organic acid content in root exudates;Among them,14 key genes(apy1＿2,CTPs,CDA,urh1,Cpa1,acox3,lox2 s,OPR,mpao,P5 CS,spe3,hibch,e2.3.3.10 and aldh7a1),3 key proteins(tidp3667,grmzm6g781015＿p02 and grmzm2g103546＿p01)and 6 key metabolites(uridine,13(s)-hotre,12-opda,L-isoleucine,ferroloylputrescine and L-rginine)can be fully annotated in "transcriptome-proteome-metabolome".In conclusion,AMF post symbiosis affected the root morphology,contents of root endogenous hormones,maize root exudates,enzymatic activities of Rhizosphere Soil and rhizosphere microbial diversity,and promoted maize growth and nutrient accumulation.The differential expression of genetic information in maize roots after AMF symbiosis is an important contributor to the changes in root exudates.