The Mechanism Of Arbuscular Mycorrhizal Fungi Inoculation On Selenium Uptake Andaccumulation In Rice

Selenium(Se)is an essential micronutrient for human.Biofortification of Se in rice is considered to be a safe and effective way to increase Se intake of humans.Arbuscular mycorrhizal fungi(AMF)can form a reciprocal symbiosis with rice and has an important impact on rice mineral nutrient absorption.The purpose of this study is to investigate the effects of different AMF inoculation and Se fertilization on accumulation and speciation of Se in rice.A pot experiment was conducted to investigate the effects of three AMF,including Funneliformis mosseae(Fm),Claroideoglomus etunicatum(Ce)and Glomus versiforryme(Gv)on the absorption and transport of rice Se.In addition,to release the mechanism of Fm inoculation on growth,uptake and transport of Se in rice,comparative transcriptomics of rice inoculated with Fm under Se condition was analyzed using RNA-Seq technology.The main findings are as follows:1.The considerable variation amongst the inoculation in their effects on plant growth,uptake and accumulation of Se in rice.Among three selected AMF,inoculation with Fm and Gv significantly promoted rice growth and uptake and transport of Se,and inoculation with Fm had highest Se concentration in rice grain.While Ce had no effect on rice biomass and Se uptake.2.Inoculation with three strains of AMF and different forms of Se fertilization significantly affected soil Se fraction.Compared with non-inoculation,Fm inoculation can significantly increased the content and proportion of soluble and exchangeable and carbonate-bound Se in soil.3.Fm and Gv inoculation significantly increased the diversity and abundance of soil bacterial communities;it also affected the distribution ratio of various bacteria.Compared with the treatments without Se,selenate and selenite significantly increased the relative abundance of Firmicutes;the relative abundance of Proteobacteria and Firmicutes was significantly increased when Fm inoculation compared to non-inoculated treatment.4.The Se speciation in grains of rice is mainly SeMet,accounting for 72.63-87.43%of total Se,while SeCys2 only occurs when selenate and selenite treatments are not AMF inoculated,accounting for 9.36%and 8.28%,respectively.These results indicated that inoculation with AM fungi can change the proportion of Se speciation in rice grains.5.By transcriptome sequencing analysis,compared with CK,after inoculated with Fm,two sulfur transporters SULTR1.2 and SULTR3.5,three phosphate transporters OsPT2,OsPPT3 and OsPHO1.3,and two aquaporins(NIP2.1,NIP3.2)were identified significantly up-regulated expression;in addition,it also identified a sulfur metabolism related enzyme of the cysteine gamma synthase significant up-regulation;revealing that they may be related to the uptake and assimilation of selenium in rice inoculated with Fm.Through metabolic pathway analysis of significantly up-regulated expression genes,the results indicate that a-linolenic acid metabolism,phenylpropanoid biosynthesis,carbon fixation in photosynthetic organisms,glutathione metabolism,sulfur metabolism and other metabolic pathways are closely related to rice response to Fm inoculation.6.Compared with CK,after treated with selenite,three sulfur transporters SULTR3.1,SULTR3.4 and SULTR4.1,two phosphate transporters(OsPPT3,MPT3)and 6 ABC transporters were identified significantly up-regulated expression in rice root.In addition,it also identified a significant up-regulation of the enzymes associated with sulfur metabolism,APS1,Cysteine synthase,revealing that they may interact with rice selenium uptake and assimilation related.Metabolic pathway analysis of significantly up-regulated expression genes showed that glutathione metabolism,alpha-linolenic acid metabolism,indole alkaloid biosynthesis,plant-pathogen interaction,plant hormone signal transduction and other metabolic pathways and rice response Se is closely related.