| Nicotiana tabacum is the main economic annual crop in China.In recent years,the tobacco planting environment varies according to the climate changes,such as water loss,aggravating soilborne diseases which seriously affected tobacco production.As an important microbial resource of tobacco,endophytic fungi shown significant effects on drought resistance,salt resistance and promoting tobacco growth.In our previous result,two endophytic fungi Bjerkandera sp.(MR-8)and Schizophyllum commune(X-5)could assist tobacco in coping with drought stress.In this study,the root and leaf transcriptome and metabolome of the infected tobacco K326 seedlings were jointly analyzed to explore the molecular mechanism of Bjerkandera sp.and Schizophyllum commune to assist tobacco seedlings against drought stress.The results showed that the drought-resistant endophytes in tobacco roots regulated plant via plant hormone signal transduction,carbon metabolism,starch and sucrose metabolism,phenylalanine metabolism,nitrogen metabolism pathways.Drought-resistant endophytes in tobacco leaves resist environmental stress mainly through cysteine and methionine metabolism,starch and sucrose metabolism,phenylalanine metabolism and plant hormone signal transduction.Specific results are listed as follows:(1)In this study,the roots and leaves of K326 seedlings were sequenced by highthroughput sequencing technology after 10 days of drought treatment to infect tobacco seedlings by Bjerkandera sp.MR-8 and Schizophyllum commune X-5.A total of190,118 Unigenes were obtained by assembling and removing redundancy.These Unigenes were annotated into GO,KEGG,NR,PFAM,STRING and SWISSPROT functional databases to locate the function of each gene.The number of annotated genes in each database was 36254,21553,58779,35965,662 and 36905,respectively.Compared with the control group,the number of upper(lower)modulator genes in the root and leaf of Bjerkandera sp infected group K326 was 3494(2239)and3198(4854),respectively.The number of upper and lower regulated genes was1475(2325)and 5684(6640)after infecting K326 roots and leaves.In Schizophyllum commune treatment.In Bjerkandera sp treated roots and leaves,the differentially expressed genes in the root were mainly concentrated in starch and sucrose metabolism,keratin,suberin,wax biosynthesis,pyruvate metabolism and tryptophan metabolism compared with the control group.The differentially expressed genes in leaves were mainly distributed in MAPK signaling pathways,plant hormone signal transduction,cysteine and methionine metabolism,phenylalanine metabolism,starch and sucrose metabolism,nitrogen metabolism,sulfur metabolism and other pathways.In the Schizophyllum commune treatment,the differential gene expression in root was mainly concentrated in hormone signal transduction,phenylalanine metabolism,cysteine and methionine metabolism,starch and sucrose metabolism,glycine,serine and threonine metabolism,tryptophan metabolism and carbon metabolism compared with the control group.The differential genes in leaves were mainly found in plant hormone signal transduction,starch and sucrose metabolism,cysteine and methionine metabolism,phenylalanine metabolism,phenylalanine,tyrosine and tryptophan biosynthesis and carbon metabolism.(2)In order to elucidate the effects of two different drought-resistant endophytes on metabolite accumulation in K326 tobacco seedlings,liquid chromatography and tandem mass spectrometry were used to study the responses of different tobacco parts to different drought-resistant endophytes at metabolic level.According to the metabolome data,different metabolites of different parts of tobacco were different under different treatments.Compared with the control group,the differential metabolites in the upper and lower levels of root and leaf were 16(7)and 24(6),respectively.Schizophyllum commune were treated in the roots and leaves,and the upper(lower)parameters were 16(7),24(6).In Bjerkandera sp treatment,compared with the control,the differential metabolites were mainly concentrated in tryptophan metabolism and diterpene biosynthesis.Leaf differential metabolites were mainly concentrated in diterpene biosynthesis,arginine biosynthesis,zetin biosynthesis,arginine and proline metabolism and tryptophan metabolism.In the Schizophyllum commune treatment,compared with the control,the root differential metabolites were mainly concentrated in arginine biosynthesis,diterpene biosynthesis,arginine and proline metabolism.Leaf differential metabolites were mainly concentrated in diterpene biosynthesis,cyano-amino acid metabolism,secondary metabolites biosynthesis,aminoyl biosynthesis.(3)The integrated analysis of transcriptome and metabolites were performed.The results showed Bjerkandera sp regulated hormone pathways of gibberellin 3(GA3),indole acetamide 3(IAM),abscisate glucose ester(ABA-GE),tryptamine(TRA)and indole propionic acid 3(IPA)to help K326 for resistance drought stress;Schizophyllum commune could regulate the hormone pathways of gibellin 3(GA3),ABscisate glucose ester(ABA-GE)and tryptamine(TRA)to resistant drought stress.The results showed that both Bjerkandera sp and Schizophyllum commune could help K326 to resistant drought through the regulation of plant hormones. |
