| With the development of greenhouse vegetables large-scale planting,soil-borne rootknot nematode disease caused by Meloidogyne spp.has become a significant problem in vegetable production,which seriously affects the healthy development of the vegetable industry.Eggplant(Solanum melongena L.),grown worldwide,is an important vegetable crop belonging to Solanaceae.Solanum torvum is a wild relative of eggplant and has good resistance to root-knot nematode infection.However,since the reproductive isolation between S.melongena and S.torvum,S.torvum can’t be used for cross-breeding and only be widely applied as the stock to prevent and control nematode diseases.The resistance mechanism to the nematode disease is still little known.Therefore,the discovery and utilization of resistance genes from S.torvum are significant for improving the resistance of cultivated eggplant.In this present study,we analyzed the differential gene expression and regulation pathway between two species of S.melongena and S.torvum.In addition,the differences of the endophytic microbe were also investigated in the roots of two eggplant species.The main results are as follows:The molecular mechanism of resistant and susceptible eggplant varieties(S.torvum vs Smzao)to root-knot nematode(RKN)infection was systematically analyzed.The transcriptomes at 7 dpi,14 dpi,and 28 dpi were analyzed,comparison to 0 dpi.5360 differentially expressed genes(DEGs)in the susceptible eggplant,4761 DEGs in the resistant material were identified,and 2711 DEGs were specifically found in the resistant material,among which 741 genes were differentially expressed in both materials.Twentyfour NBS-LRR resistant genes were identified.KEGG enrichment revealed that 741 DEGs were mainly involved in plant hormone signal transduction,plant-pathogen interaction,transcription factors,and phenylpropane biosynthesis.Nine WRKY transcription factors,four SA genes,and eleven GA-related DEGs were identified.Several DEGs encoding calcium-dependent protein kinases(CDPKs)were determined to be highly expressed in the resistant material.DEGs and metabolic pathway analysis indicated that ABA was involved in the defense response of eggplant defense RNKs.The expression patterns of genes related to ABA metabolic pathway under RNKs infection were analyzed.GO and KEGG enrichment showed that genes related to the cell wall,resistance protein genes,and some WRKY transcription factors were significantly upregulated in the resistant material,which enhanced the defense ability of the eggplant against RKNs.These studies laid a theoretical foundation for in-depth analysis of the resistance mechanism of eggplant and the excavation of eggplant resistant genes.S.torvum(resistant)and Smzao(susceptible)cultivated eggplants were used to analyze the microbiome in the roots at the different RNK infection stages.Based on ITS and 16 S r DNA high-throughput sequencing technologies,the microbial diversity were analyzed under RKNs stress.In RKNs early infection stage,the number of endophytic bacteria in the susceptible eggplant was significantly rich than that in the resistant eggplant,indicating that more bacteria in the susceptible eggplant were easy to colonize in roots.The dominant endophytic fungi were quite different at the early stage of RKNs infection,but were not different at the colonization stage and the late stage of RKNs infection,which indicated a specific relationship between the species of endophytic fungi and the resistance at the early stage of RKNs infection.The endophytic fungi in the susceptible eggplant were mainly saprophytic fungi belonging to Basidiomycota at the colonization and the early stage,and the abundance of some plant pathogenic fungi(such as Mortierella,Ustilago,Penicillium,and cladosporium,etc.)increased at later stage of nematode infection.The endophytic fungi in the resistant eggplant were mainly saprophytic fungi during colonization,similar to susceptible eggplant.However,at the early stage of RKNs infection,the abundance of Alternaria,Emericellopsis,and Trichoderma increased significantly.In addition,the abundance of the potential biocontrol fungi(Curvularia,Chaetomium,and Sarocladium,etc.)increased significantly.At the later stage of infection,Rhizobia,Sphingobium,Brucella,Agaricicola,and Streptomyces were enriched in the roots of the susceptible eggplant.The abundance of endophytic bacteria species was lower than in resistant eggplant,which indicated that more bacteria were colonizing and enriching in the susceptible eggplant.The study explored the response of resistant varieties to root-knot nematodes from the perspective of the microbiome,providing a reference for the planting of eggplant and adding soil microbial fertilizer in the future.Sixty-five strains of endophytic bacteria were isolated,including thirty-eight strains from the resistant eggplant and twenty-seven strains from susceptible eggplant.Among endophytic bacteria in the resistant eggplant,Bacillus sp.were dominant,accounting for63.16%.Bacillus sp.and Bacterium sp.were dominant in the susceptible eggplant,accounting for 70.37%.Thirty-six strains of endophytic fungi were isolated,including two genera and four species in the susceptible eggplant and one genus and four species in the resistant eggplant.Alternaria alternata and A.tenuissima were dominant in the resistant eggplant,accounting for 83.33%,while most were Fusarium oxysporum in the susceptible eggplant,which may cause root rot and promote the occurrence and aggravation of RKN disease,accounting for 55.56%.The results showed significant differences in the endophytic bacteria enriched among different resistant eggplant materials.The present study analyzed the molecular mechanism of the infection of RKNs,and many of the resistance genes and its related transcription factors were identified.The defense of the eggplant to RKNs infection mainly involves plant hormone signal transduction,plant-pathogen interaction,transcription factors,and other related metabolic pathways.Analysis indicated that ABA was involved in the response of eggplant defense RNKs.A study of the endophytic microbiome revealed that the resistance of eggplant to RKNs was also correlated with the endophytic microbiome.These studies will provide new strategies for screening suitable biocontrol bacteria and for integrated control and disease resistance breeding of eggplant RNKs. |
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