Tissue-specific Transcriptome Analysis Reveals Multiple Responses To Salt Stress In Populus Euphratica Seedlings

Salt stress is one of the most crucial factors impacting plant growth,development and reproduction,and has far-reaching implications for economic sustainability,food security and the irreplaceable biodiversity of the affected areas.Therefore,a comprehensive understanding of the molecular and physiological mechanisms of salt tolerance in plants will not only help us uncover plant adaptive molecular mechanisms but also contribute to the cultivation of plants/crops that can tolerate high salt stress.Here,we investigated the gene expression patterns in four tissues of Populus euphratica seedlings using RNA sequencing(RNA-Seq)technology under salt stress.The major results were shown as bellows:A total of 109.3 million,125bp paired-end clean reads were generated,and 6428,4797,2335 and 3358 differentially expressed genes(DEGs)were identified in leaf,phloem,xylem and root tissues,respectively.While the tissue-specific DEGs under salt stress had diverse functions,“catalytic activity”,“sodium ion transmembrane transporter activity”and“secondary active transmembrane transporter activity”was the most significant function of the leaf-specific DEGs,whereas“structural molecule activity”,“macromolecular complex”and“phosphate-containing compound metabolic process”were the most significant functions of the phloem-specific DEGs;“nitrogen compound transport”,“oligopeptide transport”and“peptide transport”were the most significant functions of the xylem-specific DEGs;and“oxidoreductase activity”,“electron carrier activity”and“oxidation-reduction process”were the most significant functions of the root-specific DEGs.Further analysis of the tissue-specific DEGs showed that the expression patterns or functions of gene families,such as SOS,NHX,GolS,GPX,APX,RBOHF and CBL,were diverse,suggesting that calcium signaling,reactive oxygen species(ROS)and salt overly sensitive(SOS)pathways are all involved in ionic homeostasis in tissues from P.euphratica seedlings.The DEGs,for example the up-regulated antioxidant genes,contribute to ROS-scavenging induced by salt stress but result in decreased Na~+concentrations in root vasculature cells and in xylem sap,while the down-regulated genes,such as rbohF,lead to the reverse results.These results suggest that the divergence of DEGs expression patterns contribute to maintenance of ionic and ROS homeostasis in tissues and improve plant salinity tolerance.Additionally,numerous transcription factors,including 98 MYBs,96 ERFs and 60 NACs,which are key regulators of plant responses to abiotic stresses,were identified as differentially expressed in this study which the differential expression of transcription factors promoted complex crosstalk between response pathways among tissues under salt stress.In conclusion,we comprehensively analyzed the response of P.euphratica seedlings to salt stress and provide helpful genetic resources for studying plant-abiotic stress interactions.