Genome-Wide Identification And Analysis Of The Tobacco Late Embryogenesis Abundant Proteins （LEA Proteins） Gene Family In Response To Abiotic Stresses

Nicotiana tabacum is an important model plant for scientific research and is of economic importance worldwide.Late embryogenesis abundant proteins（LEA proteins）are a group of hydrophilic proteins that appear highly disordered in aqueous solution.However,under abiotic stress conditions such as drought,high salinity and low temperature,they can perform a variety of functions to improve plant tolerance to abiotic stresses.Screening for key resistanceLEA genes in common tobacco is important for resistance breeding in tobacco.In this study,we identified a family of Late embryogenesis abundant proteins genes in the genome of common tobacco and analysed the physicochemical properties and subcellular localisation ofLEA proteins.Phylogenetic analysis and grouping,gene structure and conserved motif analysis,cis-acting element analysis,protein-protein interaction network analysis,transcription factor regulatory network analysis,and environmental selection pressure analysis were performed on common tobaccoLEA genes.The transcriptome data were used to screen for differentially expressed common tobaccoLEA genes under abscisic acid stress,salt stress,low temperature stress and alkaline stress,among other abiotic stresses,and the results of the transcriptome analysis were validated using q RT-PCR.The results of theLEA gene analysis in common tobacco were as follows.1.123 NtLEA genes were identified in the genome of common tobacco.Phylogenetic analyses ofLEA genes in common tobacco,Arabidopsis thaliana and tea were performed and evolutionary trees were constructed.Based on the results of the phylogenetic analysis,we classified the NtLEA genes into eight subgroups,includingLEA₁,LEA₂,LEA₃,LEA₄,LEA₅,LEA₆,dehydratin（DHN）,and Seed Maturation Protein（SMP）.2.The results of the physicochemical analysis of theLEA protein of common tabacco showed that most of the NtLEA proteins were hydrophilic;the results of subcellular localization analysis showed that the NtLEA protein existed in the membranes of the Golgi,nucleus,cytoplasm,chloroplast and mitochondria.The cellular membranes system is important for maintaining cellular integrity and organelle integrity under abiotic stress conditions.3.Structural analysis of theLEA genes of common tobacco showed that most homologous genes in the same subgroup exhibited similar exon-intron structure,number of exons and gene length.Most members contain 1-2 exons,with the NtLEA116 gene having the highest number of exons（5）.The phase-0 intron is present in each NtLEA gene and each NtLEA gene contains at least one phase-0 intron.Each member of theLEA₃ subgroup of common tobacco contains one phase-0 intron and one phase-1 intron,and each member of theLEA₅ subgroup contains one phase-0 intron and one phase-2 intron.The length and distribution of the untranslated region（UTR）showed a diversity of features and low sequence similarity.The motif analysis showed that at least 10 different motifs were present in the sequences of common tobaccoLEA proteins,and that the sequences of the proteins within the same subgroup had similar motif distribution patterns.The results of the gene structure and motif analysis also supported the results of the phylogenetic analysis.4.The results of cis-acting element analysis showed that a total of 19 types of cis-acting elements were identified in the common tobaccoLEA gene family,including sequence elements such as MBS,ABRE,DRE,G-box,CAAT-box and TATA-box.5.Analysis of the protein-protein interaction network showed that NtLEA99,NtLEA101 and NtLEA102 were the most complex nodes in the protein-protein interaction network of common tobacco.Analysis of the transcription factor regulatory network showed that a total of 21 transcription factors were involved in the regulation of the common tobaccoLEA gene.6.Transcriptomic data were used to analyse the differentially expressed genes in theLEA gene family of common tobacco under abscisic acid,salt,low temperature and alkali stress conditions.The results showed that 35 NtLEA genes responded to abscisic acid stress,3 NtLEA genes responded to salt stress,37 NtLEA genes responded to low temperature stress and 43 NtLEA genes responded to alkali stress.NtLEA63 was the only common tobaccoLEA gene that could respond to the four abiotic stresses.