Screening Genes Respond To Cd Stress In Seashore Paspalum By Genomics And Transcriptomics

Soil cadmium(Cd)pollution is becoming more and more serious,which not only harms crop yield and quality,but also easily accumulates in human body through food chain and threatens human health.The key to remediation of soil pollution by plant is to select plant varieties with high Cd tolerance and high concentration.Seashore paspalum(Paspalum vaginatum Sw.),a perennial warm-season lawn grass,is a kind of grass with many kinds of resistance to adversity.Its uniform and dense grass with dark green color is an excellent grass species for green lawns and playground lawns.The roots of Seashore paspalum are highly tolerant to Cd and can accumulate a large amount of Cd.Therefore,it is important to explore the molecular mechanism of Seashore paspalum response to Cd stress in cultivating new cultivars.Phenotypic identification of 172 Seashore paspalum under Cd stress was conducted in this study.Genes responsive to Cd stress were screened by genome-wide association analysis and transcriptomics,and their molecular mechanisms were elucidated.The main contents are as follows:1.Comprehensive score of Cd tolerance(Z)of 172 Seashore paspalum germplasms were calculated and ranked according to relative leaf firing(RLF)and turf quality index(TQI).Cluster analysis was conducted based on the comprehensive score(Z)and transfer coefficient(TF),and 172 Seashore paspalum germplasms were divided into three categories:A(70),B(86)and C(16).Class A had poor Cd tolerance and low transfer coefficient.Class B and C have better Cd tolerance,but B has a lower transfer coefficient than class C.2.GWAS was performed with 4833395 high-quality SNPs and 12 Cd-stress related phenotypes(RLF2、RLF4、RLF6、RLF8、RLF11、RLF13、TQI8、TQI13、Z、SDW、RDW、TF).A total of 35 peak SNPs and 125 candidate genes were obtained from 172 Seashore paspalum germplasms.A total of 64 peak SNPs and 257 candidate genes were obtained from 86 Chinese subgroups.A total of 6 peak SNPs and 26 candidate genes were obtained from 86 foreign subgroups.emFS14.107(Nramp4)and emOS150.2(Nramp5)were selected for haplotype analysis,and superior haplotypes were obtained.3.The transcriptome sequencing was performed on the leaves and roots of four germplasms of Seashore paspalum at five different times after Cd stress.PCA analysis of the transcriptome revealed that emOS169.298 and emOS120.677 were important genes in response to Cd stress in leaves of Seashore paspalum.emOS49.401＿emOS49.402(OPR)is an important gene in roots of Seashore paspalum in response to Cd stress,which regulates the key enzyme in the metabolic pathway of jasmonic acid.Jasmonic acid can enhance the tolerance of plants to heavy metals and reduce the damage of reactive oxygen species(ROS)and methylglyoxal(MG)to plants.GO enrichment analysis showed that DEGs in leaves were mainly involved in thylakoid and membrane,etc.DEGs of roots mainly involved jasmonic acid,oxylipin biosynthetic,etc.KEGG enrichment analysis showed that roots and leaves had similar molecular functional pathways,but roots had more frequent expressions than leaves,which were mainly involved in the biosynthesis of flavonoids,phenylpropanoid zeatin biosynthesis,glutathione metabolism,MAPK signaling pathway,alpha-Linolenic acid metabolism,etc.4.The genes represented by emFS10.215(CRK10),emFS 22.212(HMA5),emFS4.920(GST),emOS150.2(Nramp5),and emOS150.3(Nramp1)were identified by GWAS and GO enrichment analysis.The genes represented by emFS22.212(HMA5),emFS4.920(GST)and emFS4.922(GST)were identified by GWAS and KEGG enrichment analysis.