Evaluation Of Insect Resistance And Transcriptome Analysis Of Maize And Teosinte

During the long domestication process of maize,the stress resistance of maize decreased with the increase of yield,especially the ability to defense diseases and pests.Therefore,reducing the harm of insect pests to maize with increased yield is one of the maize breeding aims.Teosinte(Zea mays ssp.parviglumis)has been confirmed wild ancestor of maize which shows certain insect resistance in field.We found that the growth and development of armyworm fed on teosinte were much inhibited compared with those on maize.To explore the underlying mechanism,we performed transcriptome sequencing(RNA-Seq)responding to armyworm damage.Herein the leaves from maize and teosinte that damaged by armyworm at 0 h and 12 h,respectively were adopted,the responding transcriptomes were analyzed and the candidate insect-resistant genes were screened out.At the same time,the reliability of transcriptome data was verified by real-time PCR.The conclusions are as follows:1.There were significant differences in the nutrient effect indexes and the body length of armyworm that fed with teosinte and maize leaves.The armyworm development was much inhibited when fed with teosinte.2.The difference and correlation between maize and teosinte transcriptome were analyzed.It was found that the number of DEGs including up-regulated and down-regulated genes in maize were higher than those of teosinte.3.GO and KEGG analysis exhibited that the up-regulated genes in maize were enriched in photosynthesis,oxidative metabolism,secondary metabolism and so on.The up-regulated genes in teosinte were enriched in plant hormone signal transduction,secondary metabolism and MAPK kinase pathway.The down-regulated genes in maize and teosinte are both mainly related to RNA synthesis.4.Functional analysis of differently expressed genes responding to armyworm feeding revealed that:On the whole,types of up-regulated gene enrichment were scattered after feeding on maize and teosinte,while those of down-regulated gene enrichment were more concentrated.For example,up-regulated genes in maize and teosinte involve plant hormone pathways like flavonoids,cytochrome oxidase and jasmonic acid.The down-regulated genes of maize and teosinte are almost related to transcription and translation.The up-regulated genes in maize enriched in primary metabolism,flavonoid metabolism,peroxide metabolism,glycosyl transferase,inositol oxygenase,inorganic phosphate transporter,tryptamine benzoyl transferase,NADH dehydrogenase and transcription factor bHLH family.The above gene family may be the protein family of maize resist armyworm.For the down-regulated genes of maize,they are mainly amino acid ligases related to ribosome synthesis in,include that glycine-tRNA ligase,proline-tRNA ligase and leucine-tRNA ligase,H/ACA nucleoprotein complex,transcription initiation factor 4E,IF family.Glucose transporters,TIR-NBS family proteins,glucose-6-phosphate 1-Dehydrogenase and other resistance genes were also found.As for the up-regulated genes of teosinte,there are many protein families that showed resistance varied stresses,they are cytochrome oxidase P450,1-aminocyclopropane-1-carboxylate oxidase,glutamate dehydrogenase,flavone monooxygenase,lipoxygenase,acryloxygenase,ketoglutarate dioxygenase,glutamate decarboxylase,phenylalanine ammonia lyase,etc.The down-regulated genes of teosinte have the same gene family as those of maize as H/ACA riboprotein complex,rRNA biosynthetic protein,60 S ribosomal protein L18 a rRNA methyltransferase,nucleolar protein 56,25 s rRNA methyltransferase.There are also protein genes like dihydroflavonol-4-reductase,dehydration protein,tRNA-methyltransferase,zinc finger domain protein.Proteasome transporters,RNA connexins,translation initiation factor family proteins,cyclic tryptophan 2 are also identified.5.Based on transcriptome data,we identified candidate insect-resistantgenes from teosinte and their functions were analyzed.In this study,from the nutritional effect aspect,it was verified that teosinte was more resistant to armyworm than maize,and a large number of functional groups and genes were obtained by transcriptome sequencing,which could be used for cloning,transformation and verification in later study.The study might provide basic understanding for molecular mechnisms of maize and its wid ancestor to armyworm.