Metabolome and Transcriptome Analyses Reveal Flower Color Differentiation Mechanisms in Various Sophora japonica L. Petal Types.

Sophora japonica L. is an important landscaping and ornamental tree species throughout southern and northern parts of China. The most common color of S. japonica petals is yellow and white. In this study, S. japonica flower color mutants with yellow and white flag petals and light purple-red wing and keel petals were used for transcriptomics and metabolomics analyses. To investigate the underlying mechanisms of flower color variation in S. japonica 'AM' mutant, 36 anthocyanin metabolites were screened in the anthocyanin-targeting metabolome. The results demonstrated that cyanidins such as cyanidin-3-O-glucoside and cyanidin-3-O-rutinoside in the 'AM' mutant were the key metabolites responsible for the red color of the wing and keel petals. Transcriptome sequencing and differentially expressed gene (DEG) analysis identified the key structural genes and transcription factors related to anthocyanin biosynthesis. Among these, F3'5'H, ANS, UFGT79B1, bHLH, and WRKY expression was significantly correlated with the cyanidin-type anthocyanins (key regulatory factors affecting anthocyanin biosynthesis) in the flag, wing, and keel petals in S. japonica at various flower development stages.

Genome-wide analysis of the heat shock transcription factor family reveals saline-alkali stress responses in Xanthoceras sorbifolium.

The heat shock transcription factor (HSF) family is involved in regulating growth, development, and abiotic stress. The characteristics and biological functions of HSF family member in X. sorbifolium, an important oil and ornamental plant, have never been reported. In this study, 21 XsHSF genes were identified from the genome of X. sorbifolium and named XsHSF1-XsHSF21 based on their chromosomal positions. Those genes were divided into three groups, A, B, and C, containing 12, one, and eight genes, respectively. Among them, 20 XsHSF genes are located on 11 chromosomes. Protein structure analysis suggested that XsHSF proteins were conserved, displaying typical DNA binding domains (DBD) and oligomerization domains (OD). Moreover, HSF proteins within the same group contain specific motifs, such as motif 5 in the HSFC group. All XsHSF genes have one intron in the CDS region, except XsHSF1 which has two introns. Promoter analysis revealed that in addition to defense and stress responsiveness elements, some promoters also contained a MYB binding site and elements involved in multiple hormones responsiveness and anaerobic induction. Duplication analysis revealed that XsHSF1 and XsHSF4 genes were segmentally duplicated while XsHSF2, XsHSF9, and XsHSF13 genes might have arisen from transposition. Expression pattern analysis of leaves and roots following salt-alkali treatment using qRT-PCR indicated that five XsHSF genes were upregulated and one XsHSF gene was downregulated in leaves upon NaCl treatment suggesting these genes may play important roles in salt response. Additionally, the expression levels of most XsHSFs were decreased in leaves and roots following alkali-induced stress, indicating that those XsHSFs may function as negative regulators in alkali tolerance. MicroRNA target site prediction indicated that 16 of the XsHSF genes may be regulated by multiple microRNAs, for example XsHSF2 might be regulated by miR156, miR394, miR395, miR408, miR7129, and miR854. And miR164 may effect the mRNA levels of XsHSF3 and XsHSF17, XsHSF9 gene may be regulated by miR172. The expression trends of miR172 and miR164 in leaves and roots on salt treatments were opposite to the expression trend of XsHSF9 and XsHSF3 genes, respectively. Promoter analysis showed that XsHSFs might be involved in light and hormone responses, plant development, as well as abiotic stress responses. Our results thus provide an overview of the HSF family in X. sorbifolium and lay a foundation for future functional studies to reveal its roles in saline-alkali response.

Genome-wide characterization of the inositol transporters gene family in Populus and functional characterization of PtINT1b in response to salt stress.

Inositol transporters (INTs) can mediate the transmembrane transport of inositol, and play crucial roles in plant growth, development and stress resistance. However, the INT gene family in Populus has not been reported. Herein, nine INT genes were identified in the Populus trichocarpa genome and divided into three clades. Tandem duplication and whole-genome duplication events could induce the expansion of PtINT gene family. It was worth noting that PtINT1c* and 1d* formed by twice tandem gene duplication events of PtINT1b, but both had undergone partial structural loss during evolution. PtINT2_p1* and PtINT2_p2* might be originated from one INT2 gene by stop codon- and start codon-gain variants. Different members of PtINTs were localized to the plasma membrane or vacuolar membrane. PtINTs had diversified tissue expression profiles, and many members were significantly induced or suppressed after salt and drought treatments. PtINT1b was induced by drought and salinity stresses, and encoded a vacuolar inositol transporter. Overexpression of PtINT1b rendered the transgenic Arabidopsis plants more resistant to salt stress. In conclusion, this study provides valuable clues for future research on the function of PtINTs, and PtINT1b was identified as a candidate gene for genetic engineering to enhance salinity tolerance in plants.

Genome-Wide Identification and Expression Profiling of Heat Shock Protein 20 Gene Family in Sorbus pohuashanensis (Hance) Hedl under Abiotic Stress.

Small heat shock proteins (HSP20s) are a significant factor in plant growth and development in response to abiotic stress. In this study, we investigated the role of HSP20s' response to the heat stress of Sorbus pohuashanensis introduced into low-altitude areas. The HSP20 gene family was identified based on the genome-wide data of S. pohuashanensis, and the expression patterns of tissue specificity and the response to abiotic stresses were evaluated. Finally, we identified 38 HSP20 genes that were distributed on 16 chromosomes. Phylogenetic analysis of HSP20s showed that the closest genetic relationship to S. pohuashanensis (SpHSP20s) is Malus domestica, followed by Populus trichocarpa and Arabidopsis thaliana. According to phylogenetic analysis and subcellular localization prediction, the 38 SpHSP20s belonged to 10 subfamilies. Analysis of the gene structure and conserved motifs indicated that HSP20 gene family members are relatively conserved. Synteny analysis showed that the expansion of the SpHSP20 gene family was mainly caused by segmental duplication. In addition, many cis-acting elements connected with growth and development, hormones, and stress responsiveness were found in the SpHSP20 promoter region. Analysis of expression patterns showed that these genes were closely related to high temperature, drought, salt, growth, and developmental processes. These results provide information and a theoretical basis for the exploration of HSP20 gene family resources, as well as the domestication and genetic improvement of S. pohuashanensis.

Spatial variations and pools of non-structural carbohydrates in young Catalpa bungei undergoing different fertilization regimes.

Despite the importance of non-structural carbohydrates (NSC) for growth and survival in woody plants, we know little about whole-tree NSC storage. Here, Catalpa bungei trees fertilized using different schedules, including water and fertilizer integration, hole application, and no fertilization, were used to measure the spatial variations of sugar, starch, and NSC concentrations in the leaf, branch, stem, bark, and root. By calculating the volume of whole-tree NSC pools and the contribution of distinct organs, we were also able to compare the storage under various fertilization regimes. We found that the spatial distribution patterns of each organ undergoing different fertilization regimes were remarkably similar. Height-related increases in the sugar and NSC concentrations of the leaf and bark were observed. The concentrations of sugar and NSC in the branch did not appear to vary longitudinally or horizontally. The sugar and NSC concentrations in the stem fluctuated with height, first falling and then rising. The coarse root contained larger amounts of NSC components in comparison to fine root. Contrary to no fertilization, fertilization enhanced the distribution ratio of the leaf, branch, and stem NSC pools while decreasing the distribution ratio of the root NSC pool. Particularly, the addition of fertilizer and water significantly increased the biomass of the organs, enhancing the carbon sink of each organ and whole-tree in comparison to other fertilization regimes. Our main goal was to strengthen the empirical groundwork for comprehending the functional significance of NSC allocation and stock variations at the organ-level of C. bungei trees.

Soil microbial communities response to different fertilization regimes in young Catalpa bungei plantation.

Fertilization is a fundamental aspect of global forest management that enhances forest productivity and drastically affects soil microbial communities. However, few studies have investigated the differences and similarities in the responses of below-ground microbial communities to different fertilization schemes. The effects of fertilization regimes on the composition and diversity of soil fungal and bacterial communities were investigated in a young Catalpa bungei plantation in Shandong Province, Eastern China. Soil microbial communities were assessed undergoing three types of fertilization: (i) no fertilization (CK), (ii) hole fertilization (HF), and (iii) the integration of water and fertilizer (WF). We further analyzed the effects of soil depth (i.e., 0-20 and 20-40 cm) on the structure of soil microbial communities. Our results indicated that the diversity of bacteria (e.g., Chao1 and Shannon indices) reduced undergoing fertilization, and WF had a higher negative impact on bacterial diversity than HF. A lower bacterial diversity was observed in the subsoil compared to the topsoil. In contrast to bacterial diversity, fungal diversity had a slightly increasing trend in the fertilized environments. The primary bacterial function was metabolism, which was independent of fertilization or soil depth. Among fungal functional guilds, symbiotic soil fungi decreased obviously in the fertilized stand, whereas saprotrophic fungi increased slowly. According to the structural equation models (SEM), the diversity and composition of bacterial and fungal communities were jointly regulated by soil nutrients (including N and P contents) directly affected by fertilization and soil layer. These findings could be used to develop management practices in temperate forests and help sustain soil microbial diversity to maintain long-term ecosystem function and services.

Characterization of Silver Nanoparticles Synthesized by Leaves of Lonicera japonica Thunb.

Background: The leaves of L. japonica (LLJ) are widely used as medicine in China. It is rich in caffeoylquinic acids, flavonoids and iridoid glycosides and has strong reducing capacities. Therefore, it can be used as a green material to synthesize silver nanoparticles. Methods: LLJ was used as a reducing agent to produce the LLJ-mediated silver nanoparticles (LLJ-AgNPs). The structure and physicochemical properties of LLJ-AgNPs were characterized by ultraviolet spectroscopy (UV-Vis), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and x-ray powder diffraction (XRD). Antioxidant activity of LLJ-AgNPs was determined by 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging. Antibacterial activity was determined by 96 well plates (AGAR) gradient dilution, while the anticancer potential was determined by MTT assay. Results: The results showed LLJ-AgNPs had a spherical structure with the maximum UV-Vis absorption at 400 nm. In addition, LLJ-AgNPs exhibited excellent antioxidant properties, where the free radical scavenging rate of LLJ-AgNPs was increased from 39% to 92% at concentrations from 0.25 to 1.0 mg/mL. Moreover, LLJ-AgNPs displayed excellent antibacterial properties against E. coli and Salmonella at room temperature, with minimum inhibitory values of 10-6 and 10-5 g/L, respectively. In addition, the synthetic LLJ-AgNPs exhibited a better inhibition effect in the proliferation of cancer cells (HepG2, MDA-MB -231, and Hela cells). Conclusion: The present study provides a green approach to synthesize LLJ-AgNPs. All those findings illustrated that the produced LLJ-AgNPs can be used as an economical and efficient functional material for further applications in food and pharmaceutical fields.

Genome-wide analysis of the heat shock transcription factor gene family in Sorbus pohuashanensis (Hance) Hedl identifies potential candidates for resistance to abiotic stresses.

Heat shock transcription factors (Hsfs) are essential regulators of plant responses to abiotic stresses, growth, and development. However, all the Hsf family members have not been identified in Sorbus pohuashanensis. Therefore, the aim of this study was to identify the Hsf family members in S. pohuashanensis and examine their expression under abiotic stress conditions through the integration of gene structure, phylogenetic relationships, chromosome location, and expression patterns. Bioinformatics-based methods, identified 33 Hsfs in S. pohuashanensis. Phylogenetic analysis of Hsfs from S. pohuashanensis and other species revealed that they were more closely related to apples and white pears, followed by Populus trichocarpa, and most distantly related to Arabidopsis. Moreover, the Hsfs were clustered into three major groups: A, B, and C. Gene structure and conserved motif analysis revealed a high degree of conservation among members of the same class. Collinearity analysis revealed that segmental duplication played an essential role in increasing the size of the SpHsfs gene family in S. pohuashanensis. Additionally, several cis-acting elements associated with growth and development, hormone response, and stress were found in the promoter region of SpHsfs genes. Furthermore, expression analysis in various tissues of S. pohuashanensis showed that the genes were closely associated with heat, drought, salt stress, growth, and developmental processes. Overall, these results provide valuable information on the evolutionary relationships of the Hsf gene family. These genes stand as strong functional candidates for further studies on the resistance of S. pohuashanensis to abiotic stresses.

Genome sequence and transcriptome of Sorbus pohuashanensis provide insights into population evolution and leaf sunburn response.

Sorbus pohuashanensis (Hance) Hedl. is a potential horticulture and medicinal plant, but its genomic and genetic backgrounds remain unknown. Here, we sequence and assemble the S. pohuashanensis reference genome using PacBio long reads. Based on the new reference genome, we resequence a core collection of 22 Sorbus spp. samples, which are divided into 2 groups (G1 and G2) based on phylogenetic and PCA analyses. These phylogenetic clusters are highly consistent with their classification based on leaf shape. Natural hybridization between the G1 and G2 groups is evidenced by a sample (R21) with a highly heterozygous genotype. Nucleotide diversity (π) analysis shows that G1 has a higher diversity than G2 and that G2 originated from G1. During the evolution process, the gene families involved in photosynthesis pathways expanded and the gene families involved in energy consumption contracted. RNA-seq data suggests that flavonoid biosynthesis and heat-shock protein (HSP)-heat-shock factor (HSF) pathways play important roles in protection against sunburn. This study provides new insights into the evolution of Sorbus spp. genomes. In addition, the genomic resources, and the identified genetic variations, especially those related to stress resistance, will help future efforts to produce and breed Sorbus spp.

The first complete chloroplast genome of Tetradium daniellii (Benn.) T. G. Hartley.

Tetradium daniellii (Benn.) T. G. Hartley is an important medicinal, ornamental, and timber tree species and belongs to genus Tetradium in family of Rutaceae. It is widely distributed in warm temperate deciduous broad-leaved forest areas in northern China, Korean Peninsula and Japan. In this study, we sequenced its sample and determined complete chloroplast genome. The CP genome of T. daniellii has a circle structure with the length 158,446 bp, includes a small single copy region (17, 972 bp), a large single copy (86, 478 bp) and two inverted repeats (26,998 bp). There were 131 genes, which included 86 protein-coding genes, 8 rRNA and 37 tRNA, and overall GC content covered by 38.3%. The gene trnK-UUU, rps16, trnG-UCC, atpF, rpoC1, trnL-UAA, trnV-UAC, petB, petD, rpl16, rpl2, ndhB, trnI-GAU, trnA-UGC and ndhA contained an intron; gene clpP, ycf3 contained 2 introns. The phylogenetic result showed that T. daniellii had the closest relationship with Tetradium ruticarpum (NC_052830).

Genome-wide analysis of BURP genes and identification of a BURP-V gene RcBURP4 in Rosa chinensis.

KEY MESSAGE: Nine RcBURPs have been identified in Rosa chinensis, and overexpression of RcBURP4 increased ABA, NaCl sensitivity, and drought tolerance in transgenic Arabidopsis. BURP proteins are unique to plants and may contribute greatly to growth, development, and stress responses of plants. Despite the vital role of BURP proteins, little is known about these proteins in rose (Rosa spp.). In the present study, nine genes belonging to the BURP family in R. chinensis were identified using multiple bioinformatic approaches against the rose genome database. The nine RcBURPs, with diverse structures, were located on all chromosomes of the rose genome, except for Chr2 and Chr3. Phylogenic analysis revealed that these RcBURPs can be classified into eight subfamilies, including BNM2-like, PG1ß-like, USP-like, RD22-like, BURP-V, BURP-VI, BURP-VII, and BURP-VIII. Conserved motif and exon-intron analyses indicated a conserved pattern within the same subfamily. The presumed cis-regulatory elements (CREs) within the promoter region of each RcBURP were analyzed and the results showed that all RcBURPs contained different types of CREs, including abiotic stress-, light response-, phytohormones response-, and plant growth and development-related CREs. Transcriptomic analysis revealed that a BURP-V member, RcBURP4, was induced in rose leaves and roots under mild and severe drought treatments. We then overexpressed RcBURP4 in Arabidopsis and examined its role under abscisic acid (ABA), NaCl, polyethylene glycol (PEG), and drought treatments. Nine stress-responsive genes expression were changed in RcBURP4-overexpressing leaves and roots. Furthermore, RcBURP4-silenced rose plants exhibited decreased tolerance to dehydration. The results obtained from this study provide the first comprehensive overview of RcBURPs and highlight the importance of RcBURP4 in rose plant.

Analysis of the thaumatin-like genes of Rosa chinensis and functional analysis of the role of RcTLP6 in salt stress tolerance.

MAIN CONCLUSION: A total of 27 rose thaumatin-like protein (TLP) genes were identified from the rose genome through bioinformatics analyses. RcTLP6 was found to confer salinity stress tolerance in rose. Thaumatin-like proteins (TLPs) play critical roles in regulating many biological processes, including abiotic and biotic stress responses in plants. Here, we conducted a genome-wide screen of TLPs in rose (Rosa chinensis) and identified 27 RcTLPs. The identified RcTLPs, as well as other TLPs from six different plant species, were placed into nine groups based on a phylogenetic analysis. An analysis of the intron-exon structures of the TLPs revealed a high degree of similarity. RcTLP genes were found on all chromosomes except for chromosome four. Cis-regulatory elements (CEs) were identified in the promoters of all RcTLPs, including CEs associated with growth, development and hormone-responsiveness, as well as abiotic and biotic responses, indicating they play diverse roles in rose. Transcriptomics analysis revealed that RcTLPs had tissue-specific expression patterns, and several root-preferential RcTLPs were responsive to drought and salinity stress. Quantitative PCR analysis of six RcTLPs under ABA, PEG and NaCl treatment confirmed the differentially expressed genes identified in the transcriptomics experiment. In addition, silencing RcTLP6 in rose leaves led to decreased tolerance to salinity stress. We also screened proteins which may interact with RcTLP6 to understand its biological roles. This study represents the first report of the TLP gene family in rose and expands the current understanding of the role that RcTLP6 plays in salt tolerance. These findings lay a foundation for future utilization of RcTLPs to improve rose abiotic stress tolerance.

The complete chloroplast genome of Waldheimia glabra.

Waldheimia glabra (Decne.) Rgl. 1879 (family Asteraceae) is a perennial herb with high economic and medicinal values. In this study, we sequenced the complete chloroplast (cp) genome of W. glabra by high-throughput Illumina sequencing. The size of the W. glabra cp genome is 151,499 bp, with overall GC content of 37.3%. It contains a large single copy and a small single copy region of 83,078 bp and 18,457 bp, respectively, separated by a pair of inverted repeats regions of 24,982 bp. We also discovered 131 genes, including 86 protein-coding genes, 37 transfer RNA genes, and 8 ribosomal RNA genes in the genome. The maximum-likelihood phylogenetic tree demonstrated that W. glabra is closely related to Leucanthemella linearis.

Physiological and transcriptomic analyses characterized high temperature stress response mechanisms in Sorbus pohuashanensis.

Sorbus pohuashanensis (Hance) Hedl. is a Chinese native alpine tree species, but the problem of introducing S. pohuashanensis to low altitude areas has not been solved. In this study, we aimed to explore the molecular regulatory network of S. pohuashanensis in response to high-temperature stress using RNA-Sequencing technology and physiological and biochemical determination. Based on transcriptomic data, we obtained 1221 genes (752 up-regulated and 469 down-regulated) that were differentially expressed during 8 h 43℃ treatment and candidate genes were related to calcium signaling pathway, plant hormone signal transduction, heat shock factors, chaperones, ubiquitin mediated proteolysis, cell wall modification, ROS scavenging enzymes, detoxification and energy metabolism. The analysis of high temperature response at the physiological level and biochemical level were performed. The chlorophyll fluorescence parameters of leaf cells decreased, the content of osmotic regulators increased, and the activity of ROS scavenging enzymes decreased. The molecular regulatory network of S. pohuashanensis in response to high-temperature stress was preliminarily revealed in this study, which provides fundamental information improving introducing methods and discovering heat-tolerant genes involved in high-temperature stress in this species and provides a reference for other plants of the genus Sorbus.

Characterization of the complete chloroplast genome of Quercus virginiana Mill. (Fagaceae).

The complete chloroplast genome of Quercus virginiana was sequenced with Illumina HiSeq 2000 platform. It was a typical quadruple structure as other plants of Quercus with 161,221 bp in length, including a large single-copy (LSC: 90,553 bp) region and a small single-copy (SSC: 19,016 bp) which were separated by a pair of inverted repeats (IRa, b: 25,826 bp) region. The overall GC content is 36.9%. A total of 131 genes was annotated which contained 86 protein-coding genes including the Trans splicing gene of rps12, 37 tRNA genes, and 8 rRNA genes. ML phylogenetic analysis compared with 17 expressed chloroplast genomes revealed that Q. virginiana was a sister to other species of Quercus, which were grouped together with five species of Section Quercus and another 12 species of Quercus were divided into another group.

The first complete chloroplast genome of Hovenia dulcis Thunb. (Rhamnaceae).

The complete chloroplast genome of Hovenia dulcis was sequenced with Illumina HiSeq 2000 platform. It was a typical quadruple structure as other plants of Hovenia with 162,962 bp in length, including a large single-copy (LSC: 90,900 bp) region and a small single-copy (SSC: 18,920 bp) which were separated by a pair of inverted repeats (IRa, b: 26,571 bp) region. The overall GC content is 36.6%. A total of 130 genes was annotated which contained 85 protein-coding genes including the Trans splicing gene of rps12, 37 tRNA genes, and 8 rRNA genes. ML phylogenetic analysis compared with 6 expressed chloroplast genomes of Rhamnaceae revealed that H. dulcis was closely related to the species of Zizyphus, and which were clustered into a group with Z. jujuba, Z. mauritiana and Z. spina-christi. Hovenia dulcis was relatively distant to other species of Berchemiella and Rhamnus, which were clustered into another group.

Chloroplast genome features and phylogenomic placement of Sorbus hupehensis var. paucijuga (Rosaceae).

The complete chloroplast genome of Sorbus hupehensis var. paucijuga was sequenced with Illumina HiSeq 2000 platform. It was a typical quadruple structure as other plants of Sorbus with 160,050 bp in length, including a large single-copy (LSC: 87,905 bp) region and a small single-copy (SSC: 19,325 bp) which were separated by a pair of inverted repeats (IRa, b: 26,410 bp) region. The overall GC content is 36.5%. A total of 130 genes was annotated which contained 85 protein-coding genes including the Trans splicing gene of rps12, 37 tRNA genes, and 8 rRNA genes. ML phylogenetic analysis compared with 7 expressed chloroplast genomes of Rosaceae revealed that S. hupehensis var. paucijuga was a sister to other Sorbus species. Six species of Sorbus were divided into two groups, the species of group one is distributed in Asia and the species of group two distributed in Europe. Among group one, S. hupehensis var. paucijuga had the closest genetic relationship with S. ulleungensis which is a New Endemic Species on Ulleung Island of Korea, and followed by S. setschwanensis which is only distributed in Sichuan and Guizhou of China. Sorbus hupehensis var. paucijuga has a relatively close relationship with the other three species of Sorbus in the group two. And, it has a relatively distant from other genera of Prunus mongolica and Rosa rugosa.

The complete chloroplast genome sequence of Stephanandra incisa.

Stephanandra incisa is a typical discontinuous distribution species in the eastern part of the subspecies with a high economic and ecological value. In this study, we have obtained the complete chloroplast genome of S. incisa using high-throughput sequencing. The chloroplast genome length was 159,583 bp, the AT content was 63.7%, while the large single copy and a small single copy area were 88,018 bp and 18,817 bp, respectively. It contains 131 genes, including 86 protein-coding genes, 37 transfer RNA genes, and eight ribosomal RNA genes. A maximum-likelihood phylogenetic tree supported the fact that S. incisa is closely related to Pyracantha fortuneana and Amelanchier sinica, which is consistent with the taxonomic view.

De novo transcriptomic analysis and identification of EST-SSR markers in Stephanandra incisa.

Stephanandra incisa is a wild-type shrub with beautiful leaves and white flowers and is commonly used as a garden decoration accessory. However, the limited availability of genomic data of S. incisa has restricted its breeding process. Here, we identified EST-SSR markers using de novo transcriptome sequencing. In this study, a transcriptome database containing 35,251 unigenes, having an average length of 985 bp, was obtained from S. incisa. From these unigene sequences, we identified 5,555 EST-SSRs, with a distribution density of one SSR per 1.60 kb. Dinucleotides (52.96%) were the most detected SSRs, followed by trinucleotides (34.64%). From the EST-SSR loci, we randomly selected 100 sites for designing primer and used the DNA of 60 samples to verify the polymorphism. The average value of the effective number of alleles (Ne), Shannon's information index (I), and expective heterozygosity (He) was 1.969, 0.728, and 0.434, respectively. The polymorphism information content (PIC) value was in the range of 0.108 to 0.669, averaging 0.406, which represented a middle polymorphism level. Cluster analysis of S. incisa were also performed based on the obtained EST-SSR data in our work. As shown by structure analysis, 60 individuals could be classified into two groups. Thus, the identification of these novel EST-SSR markers provided valuable sequence information for analyzing the population structure, genetic diversity, and genetic resource assessment of S. incisa and other related species.

Molecular characterization and expression analysis of small heat shock protein 17.3 gene from Sorbus pohuashanensis (Hance) Hedl. in response to abiotic stress.

Sorbus pohuashanensis, a native tree species in China that is distributed at high altitudes. However, the problem of adaptability when introducing S. pohuashanensis to low altitude areas has not been solved. sHSPs can respond and play an essential role when exposing to abiotic stresses for plants. In this study, we aimed to investigate the expression patterns underlying the abiotic stress response of the small heat shock protein 17.3 gene from S. pohuashanensis (SpHSP17.3) at growing low altitude. 1 to 4 years old seedlings of S. pohuashanensis were used as materials for the gene cloning, the tissue-specific expression and the expression analysis underlying the response to abiotic stress using the transgentic methods and qPCR. We identified the open reading frame (ORF) sequence of SpHSP17.3 of 471 bp, which encodes a 17.3 kD protein of 156 amino acids that is located in cytoplasmic. We found that SpHSP17.3 had the highest expression in the stem, followed sequentially by fruit, root, and flower. The expression level of SpHSP17.3 in the leaves was significantly induced by the high temperature (42 °C), NaCl salt and drought stress of S. pohuashanensis. Notably, the same SpHSP17.3 expression trend was detected in the SpHSP17.3-overexpressing homozygous transgenic Arabidopsis underlying the high temperature, NaCl salt and drought stress, and the SpHSP17.3-overexpressing homozygous transgenic Arabidopsis also showed higher seed germination rates under the NaCl salt stress conditions. Our results suggested that SpHSP17.3 is involved in the response to high temperature, Nacl salt, and drought stress which would play a certain effect in the adaptability of introduction and domestication of S. pohuashanensis.