Comparative Transcriptome Analysis Of Maize Responses To Salt Stress And The Investigation Of Mechanism Of Plant Salt Tolerance

Soil salinity is one of the most important environmental stresses that severely limit crop production worldwide.Improving crop salt tolerance has become an urgent issue.Deep understanding of the mechanism of plant salt tolerance,and identification and exploration of critical genes involved in plant stress response contributes to the development of salt-tolerant crop cultivars.A comprehensive understanding on plant response to salt stress at the transcriptome level is of great significance.Tianta5 is a high-yield and stress-resistance maize hybrid.The physiological and biochemical analysis showed that Tianta5 was a clutivar with extreme salt tolerance and its salt-tolerant ability was much better than its parent inbred lines: salt-tolerant “HOO-108” and salt-sensitive “825”.To investigate the heterosis mechanism for salinity tolerance,comparative transcriptome analysis among Tianta5 and its parent inbred lines were carried out.A total of 5,084 genes out of 26,112 were differentially expressed in Tianta5 as compared with its parent inbred lines.Gene ontology analysis suggested genes involved in cytoplasmic vesicle,organic acid biosynthetic and metabolic process,ion binding and anion transmembrane transporter,and oxidoreductase activity were significantly enriched.The significantly enriched pathways of diferentially expressed genes included phenylpropanoid biosynthesis,flavonoid biosynthesis,alpha-Linolenic acid metabolism,plant-pathogen interaction,etc.Further,the transcriptome analysis of all transcription factor(TF)families in Tianta5 and 825 was performed.A set of TF families were differentially expressed in response to salt stress,including NAC,WRKY,ERF,bZIP,HSF,bHLH and MYB superfamily,and the expression patterns of these TFs clearly demonstrated their essential roles in maize salt tolerance.In addition,phylogenetic analysis and qRT-PCR analysis of the response of HSF genes to salt stress revealed that most of these TFs were induced by salt stress,but different classes/subclasses showed different response to salt stress.The results contribute to the elucidation of the roles of different TF families in plant salinity response and tolerance.Overall,the genes identified in this study provide new insights into the regulatory mechanism involved in salt response and tolerance,and can help explore novel candidate genes and crucial pathways for plant salt stress response and tolerance.Chinese wolfberry(Lycium chinense Mill.)is an important traditional Chinese herbal medicine with strong salt-tolerant capacity and rich in carotenoids.The characterization of leaf transcriptome of L.chinense under soil salinity conditions was investigated.61,595 unigenes were obtained from the de novo assembly.NCBI non-redundant protein(NR),Swiss-Prot,Kyoto Encyclopedia of Genes and Genomes(KEGG)database,Gene Ontology and the Cluster of Orthologous Group were used for unigene annotation respectively.A large number of genes potentially involved in plant response to salt stress,including genes related to ion transporters,antioxidases,Hsps,and TFs were identified,which could improve our understanding of the mechanisms of L.chinense stress adaptation.Furthermore,a set of key genes encoding the enzymes in carotenoid biosynthesis pathway were identified in the unigene datasets.The expression levels of these genes and their biological functions involved in carotenoid biosynthesis in the leaf and the ripening fruit were further confirmed by qPCR and high performance liquid chromatography(HPLC).This research is the first application of Illumina RNA-Seq technology to investigate the transcriptome of L.chinense.The datasets will serve as an important public information platform for further research of the biosynthesis of nutritional components and functional genomics studies on L.chinense.