| Soil salinization is one of the important factors that affects the global grain yield and quality,which shows an increasing trend year by year.The development of salt-tolerant crops is an ideal way to solve the problem of using and improving salinized land.The researches on plant salt tolerance has become a hot spot in ecological agriculture science.Sugar beet(Beta vulgaris)is one of the most important sugar crops in the world.It can adapt to the high salinity in the environment to grow and harvest normally.Therefore,the research on the molecular mechanism of salt tolerance is helpful to improve the salt-tolerance of sugar beet,which is of great significance to the development and utilization of salted land and the promotion of sustainable agricultural development.In this study,the cultivated sugar beet"O68"with strong salt-tolerance was selected as the experimental material.A variety of high-throughput techniques including expression profile sequencing,whole transcriptome sequencing,smallRNA sequencing,degradome sequencing,i TRAQ proteomics and non-targeted metabonomics were performed to comprehensively study the the differences of transcriptome,proteome and metabolome under salt stress,and to explore the salt tolerant molecules(Genes/proteins/metabolites)in sugar beet.Finally,the molecular mechanism of salt stress response in sugar beet was systematically expounded by multi-omics analysis.The results are as follows:The transcriptional differences in leaves and roots of sugar beet at five time points(one control group and 4 salt treatment groups)were analyzed by using expression profile sequencing technology,and a total of 7,391 and 8,729 differentially expressed genes(DEG)were identified in leaves and roots,respectively.By comparing the distribution of DEG among samples,244 core genes involved in salt stress response were identified.The weighted correlation network analysis method was used to screen out 27 and 24 hub genes corresponding to treatment time in leaves and roots,respectively.The expression pattern of hub genes under salt stress was verified by q PCR.Hub genes,core genes and some important salt stress response genes were used to construct the salt stress response network at the transcriptional level in sugar beet.Functional analysis showed that hub gene Bv2?023810?guyf regulatedRNA processing,Bv5?099740?zpio regulated ROS signal,Bv7?172340?kzsr regulated PA signal,and Bv6?131780?uxzh regulated GABA signal,sugar beet activated the downstream salt stress response network by up-regulating the expression of these genes.The treatment condition(300 mmol·L-1 Na Cl treatment for 12 h)was selected from the most significant transcriptional difference among the expression profile sequencing,and whole transcriptome sequencing and smallRNA sequencing were used to analyze the expression differences of non-codingRNA in sugar beet under salt stress.Finally,a total of 9,076 novel lncRNAs,2,625 novel circRNAs and 329novel miRNAs were identified in sugar beet.Differential analysis showed that there were 66 and 453 DElncRNAs,13 and 30 DEcircRNAs and 73 and 64 DEmiRNAs in sugar beet leaves and roots under salt stress,respectively.A competitive endogenousRNA(ceRNA)network was constructed based on DEmRNA,DElncRNA,DEcircRNA and DEmiRNA to regulate salt stress response in sugar beet.Degradome sequencing and q PCR were used to verify the networks.Functional analysis showed that specific lncRNA and circRNA played the role of ceRNA in the salt stress response in sugar beet,and the ceRNA networks were involved beet salt stress response by regulating tocopherol synthesis,Cu2+redistribution,sucrose transport,glyoxalic acid cycle,phosphoinositol signal transduction and so on in sugar.As coding genes need to be translated into proteins to perform their biological functions,the difference at protein levels can more directly reflect the molecular mechanism of plant response to salt stress.In this study,a total of 70 and 76differential abundance protein species(DAPs)were identified in leaves and roots using i TRAQ-based proteomics,respectively,and protein-protein interaction(PPI)analysis was used to construct proteic network in sugar beet under salt stress.Functional analysis of DAPs showed that sugar beet promoted the accumulation of soluble sugar and betaine to regulate osmotic balance by up-regulating DSP4,CMO and BADH proteins.Photosynthesis was maintained by up-regulation the expression of Photosystem II Psb Q protein,plastocyanin and thioredoxin.The biosynthesis of choline was promoted by upregulation of serine decarboxylase,choline/ethanolamine kinase and phosphoethanolamine N-methyltransferase to provide sufficient substrates for phospholipid metabolism.Transcription and translation processes were regulated by up-regulation of DEAD-boxRNA helicase and An J1.The q RT-PCR experiments confirmed that the expression pattern of DAP was consistent with that of their coding gene.A total of 495 small molecule metabolites were identified in leaves using non-targeted metabolomics,of which 157 metabolites showed significant differences under salt stress.KEGG analysis showed that linoleic acid metabolism was the most enriched pathway of differential metabolites,which indicatd that the adjustment of membrane structure was important for salt tolerance of sugar beet.Multi-omics analysis revealed the differences of abscisic acid,ethylene,betaine,phosphatidylcholine and enzymes related to energy metabolism under salt stress.DEGs,DAPs and differential metabolites were used to construct the molecular network of sugar beet in response to salt stress.In general,there were significant differences between leaf and root response strategies to salt stress.The main adjustment direction of leaf metabolism is to ensure photosynthesis to supply energy for survival under salt stress.However,the adjustment directions of root metabolism under salt stress is to accumulate osmotic regulation substances,transport excess Na+to storage organs,enhance cell wall strength and enhance energy metabolism. |
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