Phosphates with Two Types of Isolated P-O Groups: Noncentrosymmetric Na6Sr2Bi3(PO4)(P2O7)4 and Centrosymmetric Cs2CaBi2(PO4)2(P2O7).

Inorganic phosphates are of great interest, because of their rich structural chemistry and multiple functional properties. Compared with the phosphates that only contain the solely condensed P-O groups, the phosphates with various condensed P-O groups are less reported, especially for the noncentrosymmetric (NCS) ones. Here, two new bismuth phosphates, Na6Sr2Bi3(PO4)(P2O7)4 and Cs2CaBi2(PO4)2(P2O7), were synthesized by the solid-state reaction and both structures contain two types of isolated P-O groups. Remarkably, Na6Sr2Bi3(PO4)(P2O7)4 crystallizes in the tetragonal space group P4̅21c, which represents the first NCS bismuth phosphate with PO4 and P2O7 groups. Detailed structural comparisons among Bi3+-containing alkali/alkaline-earth metal phosphates show that the ratios of cations/phosphorus profoundly influence the condensed degree of P-O groups. Ultraviolet-visible-near-infrared (UV-vis-NIR) diffusion spectra show that both compounds have the relatively short UV cutoff edges. And Na6Sr2Bi3(PO4)(P2O7)4 has a second-harmonic generation response of 1.1 × KDP. The first-principles calculations are carried out to understand the structure-performance relationship.

Transcriptome Sequencing and WGCNA Reveal Key Genes in Response to Leaf Blight in Poplar.

Leaf blight is a fungal disease that mainly affects the growth and development of leaves in plants. To investigate the molecular mechanisms of leaf blight defense in poplar, we performed RNA-Seq and enzyme activity assays on the Populus simonii × Populus nigra leaves inoculated with Alternaria alternate fungus. Through weighted gene co-expression network analysis (WGCNA), we obtained co-expression gene modules significantly associated with SOD and POD activities, containing 183 and 275 genes, respectively. We then constructed a co-expression network of poplar genes related to leaf blight resistance based on weight values. Additionally, we identified hub transcription factors (TFs) and structural genes in the network. The network was dominated by 15 TFs, and four out of them, including ATWRKY75, ANAC062, ATMYB23 and ATEBP, had high connectivity in the network, which might play important functions in leaf blight defense. In addition, GO enrichment analysis revealed a total of 44 structural genes involved in biotic stress, resistance, cell wall and immune-related biological processes in the network. Among them, there were 16 highly linked structural genes in the central part, which may be directly involved in poplar resistance to leaf blight. The study explores key genes associated with leaf blight defense in poplar, which further gains an understanding of the molecular mechanisms of biotic stress response in plants.

Ectopic Expression of PsnNAC090 Enhances Salt and Osmotic Tolerance in Transgenic Tobacco.

The NAC transcription factor family is well known to play vital roles in plant development and stress responses. For this research, a salt-inducible NAC gene, PsnNAC090 (Po-tri.016G076100.1), was successfully isolated from Populus simonii × Populus nigra. PsnNAC090 contains the same motifs at the N-terminal end of the highly conserved NAM structural domain. The promoter region of this gene is rich in phytohormone-related and stress response elements. Transient transformation of the gene in the epidermal cells of both tobacco and onion showed that the protein was targeted to the whole cell including the cell membrane, cytoplasm and nucleus. A yeast two-hybrid assay demonstrated that PsnNAC090 has transcriptional activation activity with the activation structural domain located at 167-256aa. A yeast one-hybrid experiment showed that PsnNAC090 protein can bind to ABA-responsive elements (ABREs). The spatial and temporal expression patterns of PsnNAC090 under salt and osmotic stresses indicated that the gene was tissue-specific, with the highest expression level in the roots of Populus simonii × Populus nigra. We successfully obtained a total of six transgenic tobacco lines overexpressing PsnNAC090. The physiological indicators including peroxidase (POD) activity, superoxide dismutase (SOD) activity, chlorophyll content, proline content, malondialdehyde (MDA) content and hydrogen peroxide (H2O2) content were measured in three transgenic tobacco lines under NaCl and polyethylene glycol (PEG) 6000 stresses. The findings reveal that PsnNAC090 improves salt and osmotic tolerance by enhancing reactive oxygen species (ROS) scavenging and reducing membrane lipid peroxide content in transgenic tobacco. All the results suggest that the PsnNAC090 gene is a potential candidate gene playing an important role in stress response.

Genome-Wide Identification and Expression Patterns of the F-box Family in Poplar under Salt Stress.

The F-box family exists in a wide variety of plants and plays an extremely important role in plant growth, development and stress responses. However, systematic studies of F-box family have not been reported in populus trichocarpa. In the present study, 245 PtrFBX proteins in total were identified, and a phylogenetic tree was constructed on the basis of their C-terminal conserved domains, which was divided into 16 groups (A-P). F-box proteins were located in 19 chromosomes and six scaffolds, and segmental duplication was main force for the evolution of the F-box family in poplar. Collinearity analysis was conducted between poplar and other species including Arabidopsis thaliana, Glycine max, Anemone vitifolia Buch, Oryza sativa and Zea mays, which indicated that poplar has a relatively close relationship with G. max. The promoter regions of PtrFBX genes mainly contain two kinds of cis-elements, including hormone-responsive elements and stress-related elements. Transcriptome analysis indicated that there were 82 differentially expressed PtrFBX genes (DEGs), among which 64 DEGs were in the roots, 17 in the leaves and 26 in the stems. In addition, a co-expression network analysis of four representative PtrFBX genes indicated that their co-expression gene sets were mainly involved in abiotic stress responses and complex physiological processes. Using bioinformatic methods, we explored the structure, evolution and expression pattern of F-box genes in poplar, which provided clues to the molecular function of F-box family members and the screening of salt-tolerant PtrFBX genes.

Overexpression of PagERF072 from Poplar Improves Salt Tolerance.

Extreme environments, especially drought and high salt conditions, seriously affect plant growth and development. Ethylene-responsive factor (ERF) transcription factors play an important role in salt stress response. In this study, a significantly upregulated ERF gene was identified in 84K (Populus alba × P. glandulosa), which was named PagERF072. PagERF072 was confirmed to be a nuclear-localized protein. The results of yeast two-hybrid (Y2H) assay showed that PagERF072 protein exhibited no self-activating activity, and yeast one-hybrid (Y1H) demonstrated that PagERF072 could specifically bind to GCC-box element. Under salt stress, the transgenic poplar lines overexpressing PagERF072 showed improved salt tolerance. The activities of peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) in transgenic poplars were significantly increased relative to those of wild-type (WT) plants, whereas malondialdehyde (MDA) content showed an opposite trend. In addition, reactive oxygen species (ROS) was significantly reduced, and the expression levels of POD- and SOD-related genes were significantly increased in transgenic poplars under salt stress compared with WT. All results indicate that overexpression of the PagERF072 gene can improve the salt tolerance of transgenic poplars.

Genome-wide identification and expression analysis of the xyloglucan endotransglucosylase/hydrolase gene family in poplar.

BACKGROUND: Xyloglucan endotransglucosylase/hydrolase (XTH) family plays an important role in cell wall reconstruction and stress resistance in plants. However, the detailed characteristics of XTH family genes and their expression pattern under salt stress have not been reported in poplar. RESULTS: In this study, a total of 43 PtrXTH genes were identified from Populus simonii × Populus nigra, and most of them contain two conserved structures (Glyco_hydro_16 and XET_C domain). The promoters of the PtrXTH genes contain mutiple cis-acting elements related to growth and development and stress responses. Collinearity analysis revealed that the XTH genes from poplar has an evolutionary relationship with other six species, including Eucalyptus robusta, Solanum lycopersicum, Glycine max, Arabidopsis, Zea mays and Oryza sativa. Based on RNA-Seq analysis, the PtrXTH genes have different expression patterns in the roots, stems and leaves, and many of them are highly expressed in the roots. In addition, there are11 differentially expressed PtrXTH genes in the roots, 9 in the stems, and 7 in the leaves under salt stress. In addition, the accuracy of RNA-Seq results was verified by RT-qPCR. CONCLUSION: All the results indicated that XTH family genes may play an important role in tissue specificity and salt stress response. This study will lay a theoretical foundation for further study on molecular function of XTH genes in poplar.

Genome-wide analysis and expression profile of the bZIP gene family in poplar.

BACKGROUND: The bZIP gene family, which is widely present in plants, participates in varied biological processes including growth and development and stress responses. How do the genes regulate such biological processes? Systems biology is powerful for mechanistic understanding of gene functions. However, such studies have not yet been reported in poplar. RESULTS: In this study, we identified 86 poplar bZIP transcription factors and described their conserved domains. According to the results of phylogenetic tree, we divided these members into 12 groups with specific gene structures and motif compositions. The corresponding genes that harbor a large number of segmental duplication events are unevenly distributed on the 17 poplar chromosomes. In addition, we further examined collinearity between these genes and the related genes from six other species. Evidence from transcriptomic data indicated that the bZIP genes in poplar displayed different expression patterns in roots, stems, and leaves. Furthermore, we identified 45 bZIP genes that respond to salt stress in the three tissues. We performed co-expression analysis on the representative genes, followed by gene set enrichment analysis. The results demonstrated that tissue differentially expressed genes, especially the co-expressing genes, are mainly involved in secondary metabolic and secondary metabolite biosynthetic processes. However, salt stress responsive genes and their co-expressing genes mainly participate in the regulation of metal ion transport, and methionine biosynthetic. CONCLUSIONS: Using comparative genomics and systems biology approaches, we, for the first time, systematically explore the structures and functions of the bZIP gene family in poplar. It appears that the bZIP gene family plays significant roles in regulation of poplar development and growth and salt stress responses through differential gene networks or biological processes. These findings provide the foundation for genetic breeding by engineering target regulators and corresponding gene networks into poplar lines.

Genome-wide search and structural and functional analyses for late embryogenesis-abundant (LEA) gene family in poplar.

BACKGROUND: The Late Embryogenesis-Abundant (LEA) gene families, which play significant roles in regulation of tolerance to abiotic stresses, widely exist in higher plants. Poplar is a tree species that has important ecological and economic values. But systematic studies on the gene family have not been reported yet in poplar. RESULTS: On the basis of genome-wide search, we identified 88 LEA genes from Populus trichocarpa and renamed them as PtrLEA. The PtrLEA genes have fewer introns, and their promoters contain more cis-regulatory elements related to abiotic stress tolerance. Our results from comparative genomics indicated that the PtrLEA genes are conserved and homologous to related genes in other species, such as Eucalyptus robusta, Solanum lycopersicum and Arabidopsis. Using RNA-Seq data collected from poplar under two conditions (with and without salt treatment), we detected 24, 22 and 19 differentially expressed genes (DEGs) in roots, stems and leaves, respectively. Then we performed spatiotemporal expression analysis of the four up-regulated DEGs shared by the tissues, constructed gene co-expression-based networks, and investigated gene function annotations. CONCLUSION: Lines of evidence indicated that the PtrLEA genes play significant roles in poplar growth and development, as well as in responses to salt stress.

Over-expression of poplar NAC15 gene enhances wood formation in transgenic tobacco.

BACKGROUND: NAC (NAM/ATAF/CUC) is one of the largest plant-specific transcription factor (TF) families known to play significant roles in wood formation. Acting as master gene regulators, a few NAC genes can activate secondary wall biosynthesis during wood formation in woody plants. RESULTS: In the present study, firstly, we screened 110 differentially expressed NAC genes in the leaves, stems, and roots of di-haploid Populus simonii×P. nigra by RNA-Seq. Then we identified a nucleus-targeted gene, NAC15 gene, which was one of the highly expressed genes in the stem among 110 NAC family members. Thirdly, we conducted expression pattern analysis of NAC15 gene, and observed NAC15 gene was most highly expressed in the xylem by RT-qPCR. Moreover, we transferred NAC15 gene into tobacco and obtained 12 transgenic lines overexpressing NAC15 gene (TLs). And the relative higher content of hemicellulose, cellulose and lignin was observed in the TLs compared to the control lines containing empty vector (CLs). It also showed darker staining in the culms of the TLs with phloroglucinol staining, compared to the CLs. Furthermore, the relative expression level of a few lignin- and cellulose-related genes was significantly higher in the TLs than that in the CLs. CONCLUSIONS: The overall results indicated that NAC15 gene is highly expressed in the xylem of poplar and may be a potential candidate gene playing an important role in wood formation in transgenic tobacco.

Transcriptome analysis of salt-responsive and wood-associated NACs in Populus simonii × Populus nigra.

BACKGROUND: NAC (NAM, ATAF1-2, and CUC2) family is one of the largest plant-specific transcription factor families known to play significant roles in plant development processes and stress responses. RESULTS: In the study, a total of 112 NACs were identified to be differentially expressed in the comparisons of leaves and stems, leaves and roots, roots and stems of Populus simonii×P. nigra among 289 members by RNA-Seq. And 148, 144 and 134 NACs were detected to be salt-responsive in the roots, stems and leaves under 150 mM NaCl stress, respectively. Among them, a total of 53 salt-responsive NACs were shared across the three tissues. Under salt stress, 41/37 NACs were identified to be up/down-regulated in the leaves of Populus simonii × P.nigra among 170 non-redundant NACs by RT-qPCR, which was similar with RNA-Seq results. The expression pattern analysis of 6 NACs including four randomly up-regulated genes (NAC86, NAC105, NAC139 and NAC163) and two down-regulated genes (NAC15 and NAC149) indicated a few NACs showed specific temporal and spatial expression patterns in the three tissues of Populus simonii×P.nigra. Based on transcriptome screening and phylogenic analysis of differentially expressed NACs in different tissues under salt stress, 18 potential NACs associated with wood formation and 20 involved in stress responses were identified in Populus simonii×P.nigra. CONCLUSIONS: The study further gains an understanding of the connection of tissue specificity and gene function in poplar, and lays the foundation of functional analysis of poplar NACs in stress responses.

Ectopic expression of a poplar gene NAC13 confers enhanced tolerance to salinity stress in transgenic Nicotiana tabacum.

NACs are one of the major transcription factor families in plants which play an important role in plant growth and development, as well as in adverse stress responses. In this study, we cloned a salt-inducible NAC transcription factor gene (NAC13) from a poplar variety 84K, followed by transforming it into both Nicotiana tabacum and Arabidopsis thaliana. Stable expression analysis of 35S::NAC13-GFP fusion protein in Arabidopsis indicated that NAC13 protein was localized to the nucleus. We also obtained five transgenic tobacco lines. Evidence from morphological and physiological characterization and salt treatment analyses indicated that in the transgenic tobacco the salt tolerance was enhanced, suggesting that NAC13 gene may function as a positive regulator in tobacco responses to salt stress.

Expression patterns of WRKY genes in di-haploid Populus simonii × P. nigra in response to salinity stress revealed by quantitative real-time PCR and RNA sequencing.

KEY MESSAGE: Spatio-temporal expression patterns of 13 out of 119 poplar WRKY genes indicated dynamic and tissue-specific roles of WRKY family proteins in salinity stress tolerance. To understand the expression patterns of poplar WRKY genes under salinity stress, 51 of the 119 WRKY genes were selected from di-haploid Populus simonii × P. nigra by quantitative real-time PCR (qRT-PCR). We used qRT-PCR to profile the expression of the top 13 genes under salinity stress across seven time points, and employed RNA-Seq platforms to cross-validate it. Results demonstrated that all the 13 WRKY genes were expressed in root, stem, and leaf tissues, but their expression levels and overall patterns varied notably in these tissues. Regarding overall gene expression in roots, the 13 genes were significantly highly expressed at all six time points after the treatment, reaching the plateau of expression at hour 9. In leaves, the 13 genes were similarly up-regulated from 3 to 12 h in response to NaCl treatment. In stems, however, expression levels of the 13 genes did not show significant changes after the NaCl treatment. Regarding individual gene expression across the time points and the three tissues, the 13 genes can be classified into three clusters: the lowly expressed Cluster 1 containing PthWRKY28, 45 and 105; intermediately expressed Clusters 2 including PthWRKY56, 88 and 116; and highly expressed Cluster 3 consisting of PthWRKY41, 44, 51, 61, 62, 75 and 106. In general, genes in Cluster 2 and 3 displayed a dynamic pattern of "induced amplification-recovering", suggesting that these WRKY genes and corresponding pathways may play a critical role in mediating salt response and tolerance in a dynamic and tissue-specific manner.

Expression patterns of ERF genes underlying abiotic stresses in di-haploid Populus simonii × P. nigra.

176 ERF genes from Populus were identified by bioinformatics analysis, 13 of these in di-haploid Populus simonii × P. nigra were investigate by real-time RT-PCR, the results demonstrated that 13 ERF genes were highly responsive to salt stress, drought stress and ABA treatment, and all were expressed in root, stem, and leaf tissues, whereas their expression levels were markedly different in the various tissues. In roots, PthERF99, 110, 119, and 168 were primarily downregulated under drought and ABA treatment but were specifically upregulated under high salt condition. Interestingly, in poplar stems, all ERF genes showed the similar trends in expression in response to NaCl stress, drought stress, and ABA treatment, indicating that they may not play either specific or unique roles in stems in abiotic stress responses. In poplar leaves, PthERF168 was highly induced by ABA treatment, but was suppressed by high salinity and drought stresses, implying that PthERF168 participated in the ABA signaling pathway. The results of this study indicated that ERF genes could play essential but distinct roles in various plant tissues in response to different environment cues and hormonal treatment.

The metallothionein gene, TaMT3, from Tamarix androssowii confers Cd2+ tolerance in tobacco.

Cadmium (Cd) is a nonessential microelement and low concentration Cd2+ has strong toxicity to plant growth. Plant metallothioneins, a class of low molecular, cystein(Cys)-rich and heavy-metal binding proteins, play an important role in both metal chaperoning and scavenging of reactive oxygen species (ROS) with their large number of cysteine residues and therefore, protect plants from oxidative damage. In this study, a metallothionein gene, TaMT3, isolated from Tamarix androssowii was transformed into tobacco (Nicotiana tobacum) through Agrobacterium-mediated leaf disc method, and correctly expressed under the control of 35S promoter. Under Cd2+ stress, the transgenic tobacco showed significant increases of superoxide dismutase (SOD) activity and chlorophyll concentration, but decreases of peroxidase (POD) activity and malondialdehyde (MDA) accumulation when compared to the non-transgenic tobacco. Vigorous growth of transgenic tobacco was observed at the early development stages, resulting in plant height and fresh weight were significantly larger than those of the non-transgenic tobacco under Cd2+ stress. These results demonstrated that the expression of the exogenous TaMT3 gene increased the ability of ROS cleaning-up, indicating a stronger tolerance to Cd2+ stress.

Multi-omics analysis of Populus simonii × P. nigra leaves under Hyphantria cunea stress.

Poplar is an important greening and timber tree species in China, which has great economic and ecological values. However, the spread of Hyphantria cunea has become increasingly serious in recent years, resulting in huge economic loss of poplar production. Exploring the molecular mechanism of poplar reponse to H. cunea stress has significant implications for future development of new insect-resistant poplar varieties using genetic engineering technology. In this study, a total of 1039 differentially expressed genes (DEGs), 106 differentially expressed proteins (DEPs) and 212 differentially expressed metabolites (DEMs) were screened from Populus simonii × P. nigra leaves under H. cunea stress by transcriptome, proteomics and metabolomics analysis, respectively. GO and KEGG analysis showed that the DEGs and DEPs are associated with endopeptidase inhibitor activity, stress response, α-linolenic acid metabolism, phenylpropanoid biosynthesis and metabolic pathways, cysteine and methionine metabolism pathways and MAKP signaling pathway. Metabolomics analysis showed the most of DEMs were lipids and lipid molecules, and the pathways associated with transcriptome mainly include plant hormone signal transduction, α-linolenic acid metabolic pathway, amino sugar and nucleotide sugar metabolism, and phenylpropanoid biosynthesis. In particular, multi-omics analysis showed that several pathways such as α-linolenic acid metabolic, phenylpropanoid biosynthesis and metabolic pathway and cysteine and methionine metabolic pathway were significantly enriched in the three omics, which may play an important role in the resistance to pests in poplar.

Solanum nigrum L. berries extract ameliorated the alcoholic liver injury by regulating gut microbiota, lipid metabolism, inflammation, and oxidative stress.

Solanum nigrum L. (SN) berry is an edible berry containing abundant polyphenols and bioactive compounds, which possess antioxidant and antiinflammatory properties. However, the effects of SN on alcohol-induced biochemical changes in the enterohepatic axis remain unclear. In the current study, a chronic ethanol-fed mice ALD model was used to test the protective mechanisms of SN berries. Microbiota composition was determined via 16S rRNA sequencing, we found that SN berries extract (SNE) improved intestinal imbalance by reducing the Firmicutes to Bacteroides ratio, restoring the abundance of Akkermansia microbiota, and reducing the abundance of Allobaculum and Shigella. SNE restored the intestinal short-chain fatty acids content. In addition, liver transcriptome data analysis revealed that SNE primarily affected the genes involved in lipid metabolism and inflammatory responses. Furthermore, SNE ameliorated hepatic steatosis in alcohol-fed mice by activating AMP-activated protein kinase (AMPK), acetyl-CoA carboxylase (ACC), peroxisome proliferator-activated receptor α (PPAR-α). SNE reduced the expression of toll-like receptor 4 (TLR4), myeloid differentiation factor-88 (MyD88) nuclear factor kappa-B (NF-κB), which can indicate that SNE mainly adjusted LPS/TLR4/MyD88/NF-κB pathway to reduce liver inflammation. SNE enhanced hepatic antioxidant capacity by regulating NRF2-related protein expression. SNE alleviates alcoholic liver injury by regulating of gut microbiota, lipid metabolism, inflammation, and oxidative stress. This study may provide a reference for the development and utilization of SN resources.

An overview of the mechanisms and potential roles of extracellular vesicles in septic shock.

Septic shock, a subset of sepsis, is a fatal condition associated with high morbidity and mortality. However, the pathophysiology of septic shock is not fully understood. Moreover, the diagnostic markers employed for identifying septic shock lack optimal sensitivity and specificity. Current treatment protocols for septic shock have not been effective in lowering the mortality rate of patients. Most cells exhibit the capability to release extracellular vesicles (EVs), nanoscale vesicles that play a vital role in intercellular communication. In recent years, researchers have investigated the potential role of EVs in the pathogenesis, diagnosis, and treatment of different diseases, such as oncological, neurological, and cardiovascular diseases, as well as diabetes and septic shock. In this article, we present an overview of the inhibitory and facilitative roles that EVs play in the process of septic shock, the potential role of EVs in the diagnosis of septic shock, and the potential therapeutic applications of both native and engineered EVs in the management of septic shock.

A non-centrosymmetric chalcohalide synthesized through the combination of chemical tailoring with aliovalent substitution.

A new non-centrosymmetric (NCS) chalcohalide, [Sr4Cl2][Ge3S9], was successfully designed and synthesized through combining chemical tailoring with aliovalent substitution strategies from the maternal [NaSr4Cl][Ge3S10]. It can exhibit a large SHG effect (0.97 × AgGaS2), a wide band gap of 3.71 eV, and a high LDT (∼16 × AgGaS2). These results indicate that [Sr4Cl2][Ge3S9] may be a potential infrared nonlinear optical crystal.

Rapid crystallization from acoustically levitated droplets.

This paper reports on an ultrasonic levitation system developed for crystallization from solution in a containerless condition. The system has been proven to be able to levitate droplets stably and grow crystals rapidly and freely from a levitated droplet. Crystals of four samples, including NaCl, NH(4)Cl, lysozyme, and proteinase K, were obtained successfully utilizing the system. The studies showed that the crystals obtained from the acoustically levitated droplets all exhibited higher growth rates, larger sizes, better shapes, fewer crystals, as well as fewer twins and shards, compared with the control on a vessel wall. The results indicated that containerless ultrasonic levitation could play a key role in improving the crystallization of both inorganic salts and proteins. The ultrasonic levitation system could be used as a ground-based microgravity simulation platform, which could swiftly perform crystallization and screening of crystallization conditions for space crystallization and other ground-based containerless techniques. Moreover, the approach could also be conveniently applied to researching the dynamics and mechanism of crystallization. In addition, the device could be used for the preparation of high-purity materials, analysis of minute or poisonous samples, study of living cells, environmental monitoring, and so on.

Genome-wide analysis of poplar HD-Zip family and over-expression of PsnHDZ63 confers salt tolerance in transgenic Populus simonii × P.nigra.

HD-Zip is a plant-specific HB transcription factor, which participates in plant development and stress response. In this study, we identified 63 poplar HD-Zip transcription factors, which were randomly distributed on 19 chromosomes of poplar. Based on the gene structure and phylogenetic relationship, these members are divided into four groups, which have a variety of collinear evolutionary relationships. They also have rich segmental replication events and experienced strong purification selection. Based on RNA-seq analysis, we profiled the expression pattern of the 63 HD-Zip members under salt stress. Subsequently, we carried out in-depth study on the significantly up-regulated PsnHDZ63 in the stems and leaves. The transgenic Populus simonii × P.nigra plants over-expressing PsnHDZ63 displayed better morphological and physiological indexes than WT under salt stress. In addition, PsnHDZ63 enhanced salt stress tolerance of transgenic lines by combining effective stress-resistant elements to improve reactive oxygen species scavenging ability. These studies laid a foundation for a comprehensive understanding of poplar HD-Zip family members, and revealed the important role of PsnHDZ63 in plant salt tolerance.