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Walnut is a popular nut tree species and usually suffers from drought stress. However, little information is available on the mechanism of walnut responding to drought stress, resulting in lack of basic understanding for its resistance. In order to excavate more functional genes that can respond to stressors, and enrich the theoretical basis for walnut resistance, in this study, 5 MYB genes with complete ORFs were identified from J. regia and the basic bio-information as well as expression patterns in different tissues and response to drought and ABA stresses were confirmed using qRT-PCR assay. The results showed that 2 JrMYB genes belong to R1-MYB subfamily and 3 JrMYBs belong to R2R3-MYB, encoding the proteins from 212 to 362 aa in length. The phylogenetic analysis categorized proteins of 5 JrMYBs and 40 Arabidopsis AtMYBs into 10 subgroups. JrMYBs in the same subgroup exhibited significant similarities in the composition of conserved domains and motifs in amino acid sequences and exon/intron organization in DNA sequences. The results of qRT-PCR analysis revealed that JrMYB genes diversely expressed in various tissues. Moreover, the expression values of JrMYBs were upregulated or downregulated significantly under drought and ABA stresses. Most attractively, in contrast with suffering from drought stress alone, the treatments with drought and additional ABA greatly enhanced the transcript levels of JrMYBs. All these results suggested that JrMYB genes play a vital role in plant biological processes and drought as well as ABA stress response, and possibly perform as ABA-dependent drought response transcription factors in plant.

The complete chloroplast genome sequence of Lupinus westianus, an endangered and endemic species to Florida, United States, has been assembled from Illumina pair-end sequencing. The chloroplast genome structure of L. westianus is a circular molecule of 154,270 bp in length, with a large single copy (LSC) region of 82,437 bp, a small single copy (SSC) region of 15,853 bp, and a pair of inverted repeats (IRs) regions of 27,990 bp. The total G+C content of chloroplast genome is 36.47%, and while it is 41.56% of IRs, which was higher than LSC and SSC regions. The genome contained 130 genes, including 85 protein coding genes, 37 tRNA genes and 8 rRNA genes, of which 18 were duplicated in the IRs region. The phylogenetic analysis indicated that L. westianus was clustered together with other two genus of Lupinus, L. luteus and L. albus. The chloroplast genome of L. westianus laid a good foundation for genetic resoures conservation. The chloroplast genome reported provided useful genomic resources not only for the exchange of information between different species, but also for the population genetics of L. westianus and its phylogenetic and evolutionary studies.

Background Vacuolar H+-ATPase (V-ATPase) is a vital protein complex involved in abiotic stress response in plants. The G subunit of Juglans regia (JrVHAG1) was previously identified as a drought tolerance-related gene involved in the ABA (abscisic acid)-signal pathway. Heavy metal stress is becoming a major detriment for plant growth, development, and production. In order to understand the role of JrVHAG1, the potential function mechanism of JrVHAG1 exposed to CdCl2 stress was confirmed in this study. Results Transcription of JrVHAG1 was induced by ABA and increased to 58.89-fold (roots) and 7.38-fold (leaves) and by CdCl2 to 2.65- (roots) and 11.42-fold (leaves) relative to control, respectively. Moreover, when treated simultaneously with ABA and CdCl2 (ABA+CdCl2), JrVHAG1 was up-regulated to 110.13- as well as 165.42-fold relative to control in the roots and leaves, accordingly. Compared to the wild type (WT) Arabidopsis plants, the transgenic plants with overexpression of JrVHAG1 (G2, G6, and G9) exhibited increased seed germination rate, biomass accumulation, proline content, and activities of superoxide dismutase (SOD) and peroxidase (POD) under ABA, CdCl2, and ABA+CdCl2 treatments. In contrast, the reactive oxygen species (ROS) staining, malondialdehyde (MDA) content, hydrogen dioxide (H2O2) content, as well as electrolyte leakage (EL) rates of transgenic seedlings were all lower than those of WT exposed to ABA, CdCl2 and ABA+CdCl2 stresses. Furthermore, a 1200 bp promoter fragment of JrVHAG1 was isolated by analyzing the genome of J. regia, in which the cis-elements were identified. This JrVHAG1 promoter fragment showed expression activity that was enhanced significantly when subjected to the above treatments. Yeast one-hybrid assay and transient expression analysis demonstrated that JrMYB2 specifically bound to the MYBCORE motif and shared similar expression patterns with JrVHAG1 under ABA, CdCl2 and ABA+CdCl2 stress conditions. Conclusions Our results suggested that the JrVHAG1 gene functions as a CdCl2 stress response regulator by participating in ABA-signal pathway and MYB transcription regulation network. JrVHAG1 gene is a useful candidate gene for heavy metal stress tolerance in plant molecular breeding. Electronic supplementary material The online version of this article (10.1186/s12870-018-1231-7) contains supplementary material, which is available to authorized users.

Genes encoding plant WRKY transcription factors are important for stress response. In the current study, two WRKY transcription factor genes (JrWRKY6 and JrWRKY53) were identified from walnut (Juglans regia L.), and their function and involvement in stress responses were characterized. Under NaCl stress, JrWRKY6 and JrWRKY53 were upregulated in a short time (within 6 h of seedling exposure to salt) except in roots, in which the highest induction occurred at 24 and 48 h of salt exposure. The gene expression patterns under polyethylene glycol stress were similar to those under NaCl stress. Under heat stress, both genes were induced in all tissues, except for JrWRKY6 in leaf tissue of seedlings treated for 24 and 48 h. Both genes were also induced in all plants exposed to cold stress, except for JrWRKY6 in root tissue of seedlings exposed for 6 h and JrWRKY53 in root tissue exposed for 48 h. JrWRKY6 and JrWRKY53 also showed varied responses to abscisic acid (ABA), with the maximum expression being for JrWRKY6 in the roots of plants treated for 1 h, and JrWRKY53 in the leaves of plants treated for 3 h. Furthermore, under NaCl, sorbitol, heat, cold, and ABA treatments, yeast cells transformed with JrWRKY6 and JrWRKY53 showed an improved growth activity and density relative to the empty-vector-containing control yeast. Moreover, JrWRKY6 or JrWRKY53 could bind to the W-box motif. These results suggest that JrWRKY6 and JrWRKY53 can response positively to abiotic stressors and improve the plant tolerance to salinity, osmotic stress, and abnormal temperatures in a mechanism that likely involves the ABA signalling pathway and W-box binding activity.

Broussonetia papyrifera is an important ecological and economic tree species. The sexual reproduction of B. papyrifera not only has a low germination rate, but also requires high environmental conditions. Therefore, asexual propagation using tissue culture can effectively improve the propagation efficiency of B. papyrifera. In this study, the leaves and budded shoots of B. papyrifera were used as explants, and different concentrations of plant growth regulators were added to Murashige and Skoog medium (MS) to establish a suitable system for explant callus formation, adventitious buds differentiation and rooting. The results showed that MS + 0.50 mg/L naphthaleneacetic acid (NAA) + 0.25 mg/L 6-benzyladenine(6-BA) and MS + 0.25 mg/L NAA + 0.50 mg/L 6-BA were the best mediums for rapid callus induction from leaf explants and shoot explants, respectively. The best medium combination for shoot differentiation and proliferation was MS + 0.05 mg/L NAA + 0.50 mg/L 6-BA, and the high propagation coefficient could also promote adventitious bud growth. The best rooting medium in the establishment of B. papyrifera tissue culture was MS + 0.25 mg/L NAA. Under this condition, the average rooting numbers of leaf explants and shoot explants were 1.71 and 13.86, respectively. In addition, the best transplanting substrate was a mixture of soil:perlite:vermiculite (20:1:1), and the survival rate was 91.1%. This study established a propagation system in vitro culture of B. papyrifera, and provided a reference for tissue culture of other woody plants.

JrVHAG1 is an important candidate gene for plant osmotic tolerance regulation. Vacuolar H+-ATPase (V-ATPase) is important for plant responses to abiotic stress; the G subunit is a vital part of V-ATPase. In this study, a G subunit of V-ATPase was cloned from Juglans regia (JrVHAG1) and functionally characterized. JrVHAG1 transcription was induced by mannitol that increasing 17.88-fold in the root at 12 h and 19.16-fold in the leaf at 96 h compared to that under control conditions. JrVHAG1 was overexpressed in Arabidopsis and three lines (G2, G6, and G9) with highest expression levels were selected for analysis. The results showed that under normal conditions, the transgenic and wild-type (WT) plants displayed similar germination, biomass accumulation, reactive oxygen species (ROS) level, and physiological index. However, when treated with mannitol, the fresh weight, root length, water-holding ability, and V-ATPase, superoxide dismutase, and peroxidase activity of G2, G6, and G9 were significantly higher than those of WT. In contrast, the ROS and cell damage levels of the transgenic seedlings were lower than those of WT. Furthermore, the transcription levels of V-ATPase subunits, ABF, DREB, and NAC transcription factors (TFs), all of which are factors of ABA signaling pathway, were much higher in JrVHAG1 transgenic plants than those in WT. The positive induction of JrVHAG1 gene under abscisic acid (ABA) treatments in root and leaf tissues indicates that overexpression of JrVHAG1 improves plant tolerance to osmotic stress relating to the ABA signaling pathway, which is transcriptionally activated by ABF, DREB, and NAC TFs, and correlated to ROS scavenging and V-ATPase activity.

WRKY transcription factors belong to a large protein family that is involved in diverse developmental processes and abiotic stress responses. Currently, there is little understanding of the role of WRKY transcription factors in regulatory mechanisms in plants, especially in the protein-protein interactions that are essential for biological regulatory functions and networks. In the present study, yeast one-hybrid, yeast two-hybrid, transient expression and quantitative RT-PCR were applied to investigate the potential characteristics of two WRKY proteins from Juglans regia, JrWRKY2 (GenBank Accession No. KU057089) and JrWRKY7 (GenBank Accession No. KP784651). JrWRKY2 and JrWRKY7 can form homodimers and interact with each other. JrWRKY2 and JrWRKY7 can bind to W-box motifs. Similarly high levels of transcription were found for JrWRKY2 and JrWRKY7 under NaCl and polyethylene glycol (PEG) stresses, as well as at different developmental stages, e.g., the pistil or terminal leaf. JrWRKY2 and JrWRKY7 were transiently overexpressed in an independent manner in the terminal leaf. Analyses of superoxide dismutase (SOD) and peroxidase (POD) activities, proline and malondialdehyde (MDA) contents, and electrolyte leakage rate showed that JrWRKY2 and JrWRKY7 overexpression improved plant tolerance to NaCl, PEG, abscisic acid, and cold stress. Additionally, JrWRKY2 and JrWRKY7 overexpression elevated transcription of SOD, POD, glutathione peroxidase (GPX), catalase (CAT), ascorbate peroxidase (APX), and MYB genes, but downregulated the expression of NAC. Overall, the results demonstrate that JrWRKY2 and JrWRKY7 are dimeric proteins that can form functional homodimers and interact with each other and that they are involved in abiotic stress responses.

Small heat shock proteins (sHSPs) are an HSP subgroup and involved in environmental stress response. In the current study, to understand the role of sHSP protein in a widely distribution nut woody tree, a sHSP gene was cloned from Juglans regia (JrsHSP17.3, GeneBank No.: KT277704). Compared with control condition, the expression of JrsHSP17.3 was induced to 58.1-fold (6 h) in the roots, 86.8-fold in the stems (9 h), 50.9-fold in the leaves (6 h) under 10°C; and was up-regulated to 2.9- ∼ 79.9-fold response to 40°C for 3∼9 h; meanwhile, it was transcribed to 5.9 - ∼39.7-fold under 9 h NaCl treatment, suggesting the potential role of JrsHSP17.3 to cold, heat and NaCl stimulus. Further, JrsHSP17.3 transgenic yeasts showed improved tolerance to freezing, heat and salt stresses compared with control yeast. JrsHSP17.3 was transient over-expressed in J. regia leaves. The leaves non-transgenic (NT) and vector prokII transgenic (empty, PT) were used as control. The expression of JrsHSP17.3 was 81.6-, 125.4-, and 54.2-fold of the control lines under normal conditions, indicating the success over-expression of JrsHSP17.3. Cell damage staining and physiological index determination showed that JrsHSP17.3 transformed lines, NT and PT displayed no obvious difference under control conditions, however, after treated with 16°C, 40°C and NaCl, JrsHSP17.3 transformed lines displayed weaker cell damage, lower level of electrolyte leakages (EL) rate, malondialdehyde (MDA) and H2O2 content, and higher activities of catalase (CAT), glutathione transferase (GST), superoxide dismutase (SOD) and peroxidase (POD) as well as more accumulation of proline than NT and PT. Meanwhile, NT and PT were similar and showed no significant difference under all conditions. All of these results indicated that JrsHSP17.3 can improve plant tolerance to abnormal temperatures and NaCl stresses, it represents a potential candidate gene for molecular breeding to enhance stress tolerance in plants.

Molecular analysis of a zeta subfamily GST gene from T. hispida involved in ABA and methyl viologen tolerance in transgenic Arabidopsis and Tamarix. Glutathione S-transferase (GST) genes are important for the improvement of plant abiotic stress tolerance, and our previous study demonstrated that the ThGSTZ1 gene from Tamarix hispida improves plant salt and drought tolerance. To further understand the role of ThGSTZ1 in the response of plants to abscisic acid (ABA) and oxidative stress, three ThGSTZ1-overexpressing transgenic Arabidopsis thaliana lines were analyzed in the current study. The results showed that the transgenic lines exhibited higher biomass accumulation, higher activities of GST and other protective enzymes, and less reactive oxygen species (ROS) and cell damage than wild-type (WT) plants under ABA and methyl viologen (MV) stress. In addition, the analysis of a transgenic T. hispida line transiently expressing ThGSTZ1 confirmed these results. The activities of GST, glutathione peroxidase, and superoxide dismutase were markedly higher in the ThGSTZ1-overexpressing lines compared with the control lines under both ABA and MV treatments, and the transgenic lines also exhibited a lower degree of electrolyte leakage (EL) and a decreased H2O2 content. All these results suggested that ThGSTZ1 can also improve plant ABA and oxidation tolerance by regulating ROS metabolism and that ThGSTZ1 represents an excellent candidate gene for molecular breeding to increase plant stress tolerance.

Ethylene response factors (ERFs) are plant-specific transcription factors that function as multiple regulators in various stress-responsive pathways. In the current study, to investigate the transcription patterns of ERFs in response to salt and drought treatments, four ERF genes were cloned and identified from Japanese white birch (Betula platyphylla). The real-time quantitative polymerase chain reaction (qPCR) results showed that these four BpERF genes all responded to NaCl and PEG stress. Most BpERF genes were significantly induced in roots and leaves, but not in stems, such as BpERF 1,4 under NaCl treatment, and exhibited tissue-specific expression profiles in response to different abiotic stress. Further, we cloned the four BpERF genes into pYES2 vector, transformed and expressed these genes in yeast Saccharomyces cerevisiae to investigate their tolerance to salt and drought stress. Compared with the control (yeast transformed with empty pYES2), yeast cells expressing BpERF genes showed improved tolerance to salt and drought stress, indicating that these BpERFs could confer salt and drought tolerance to transgenic yeast cells. These results suggested that these BpERF genes play important roles in abiotic stress tolerance in B. platyphylla.

Walnut (Juglans regia) is known as a promising woody oil crop with abundant polyunsaturated fatty acids in its kernel. However, the regulation mechanism of walnut oil accumulation and fatty acid metabolism is still poorly understood, which restricted the breeding and genetic improvement of high-quality oil-bearing walnuts. To reveal the molecular mechanism of walnut oil accumulation, considering the potential regulation of microRNA (miRNA) in seed development, in this study, the oil content of walnut kernel on the 80th, 100th and 120th day after flowering (DAF) was tested and the corresponding proportions are 11.51%, 40.40% and 53.20%. Between DAF of 80th~120th, the content of stearic acid and oleic acid tended to increase, but the proportion of other fatty acids tended to decrease. Meanwhile, comparative transcriptome and sRNA-seq analysis on three stages (80th, 100th and 120th DAF), found 204 conserved miRNAs and 554 novel miRNAs in walnut kernels, among which 104 key genes related to walnut oil accumulation were screened. The phospholipid:diacylglycerol acyltransferase metabolic pathway may contribute more to oil accumulation in walnut. 16 miRNA-mRNA regulatory modules related to walnut oil accumulation and fatty acid synthesis were constructed. 8 known miRNAs and 9 novel miRNAs regulate 28 genes involved in fatty acid (FA) metabolism and lipid synthesis. Among them, jre-miRn105, jre-miRn434, jre-miR477d and jre-miR156a.2 are key miRNAs that regulate walnut FA synthesis. Jre-miRn411 and jre-miR399a.1 are closely related to oil accumulation. These data provide new insights and lay the foundation for subsequent studies on walnut FA synthesis and oil accumulation.

Lack of complete genomic information concerning Vicia sepium (Fabaceae: Fabeae) precludes investigations of evolution and populational diversity of this perennial high-protein forage plant suitable for cultivation in extreme conditions. Here, we present the complete and annotated chloroplast genome of this important wild resource plant. V. sepium chloroplast genome includes 76 protein-coding genes, 29 tRNA genes, 4 rRNA genes, and 1 pseudogene. Its 124,095 bp sequence has a loss of one inverted repeat (IR). The GC content of the whole genome, the protein-coding, intron, tRNA, rRNA, and intergenic spacer regions was 35.0%, 36.7%, 34.6%, 52.3%, 54.2%, and 29.2%, respectively. Comparative analyses with plastids from related genera belonging to Fabeae demonstrated that the greatest variation in the V. sepium genome length occurred in protein-coding regions. In these regions, some genes and introns were lost or gained; for example, ycf4, clpP intron, and rpl16 intron deletions and rpl20 and ORF292 insertions were observed. Twelve highly divergent regions, 66 simple sequence repeats (SSRs) and 27 repeat sequences were also found in these regions. Detailed evolutionary rate analysis of protein-coding genes showed that Vicia species exhibit additional interesting characteristics including positive selection of ccsA, clpP, rpl32, rpl33, rpoC1, rps15, rps2, rps4, and rps7, and the evolutionary rates of atpA, accD, and rps2 in Vicia are significantly accelerated. These genes are important candidate genes for understanding the evolutionary strategies of Vicia and other genera in Fabeae. The phylogenetic analysis showed that Vicia and Lens are included in the same clade and that Vicia is paraphyletic. These results provide evidence regarding the evolutionary history of the chloroplast genome.

Background GRAS transcription factor (TF) family is unique and numerous in higher plants with diverse functions that involving in plant growth and development processes, such as gibberellin (GA) signal transduction, root development, root nodule formation, and mycorrhiza formation. Walnut tree is exposed to various environmental stimulus that causing concern about its resistance mechanism. In order to understand the molecular mechanism of walnut to adversity response, a GRAS TF (JrGRAS2) was cloned and characterized from Juglans regia in this study. Results A 1500 bp promoter fragment of JrGRAS2 was identified from the genome of J. regia, in which the cis-elements were screened. This JrGRAS2 promoter displayed expression activity that was enhanced significantly by high temperature (HT) stress. Yeast one-hybrid assay, transient expression and chromatin immunoprecipitation (Chip)-PCR analysis revealed that JrDof3 could specifically bind to the DOFCOREZM motif and share similar expression patterns with JrGRAS2 under HT stress. The transcription of JrGRAS2 was induced by HT stress and up-regulated to 6.73-~11.96-fold in the leaf and 2.53-~4.50-fold in the root to control, respectively. JrGRAS2 was overexpressed in Arabidopsis, three lines with much high expression level of JrGRAS2 (S3, S7, and S8) were selected for HT stress tolerance analysis. Compared to the wild type (WT) Arabidopsis, S3, S7, and S8 exhibited enhanced seed germination rate, fresh weight accumulation, and activities of catalase (CAT), peroxidase (POD), superoxide dismutase (SOD) and glutathione-S-transferase (GST) under HT stress. In contrast, the Evans blue staining, electrolyte leakage (EL) rates, hydrogen dioxide (H2O2) and malondialdehyde (MDA) content of transgenic seedlings were all lower than those of WT exposed to HT stress. Furthermore, the expression of heat shock proteins (HSPs) in S3, S7, and S8 was significant higher than those in WT plants. The similar results were obtained in JrGRAS2 transient overexpression walnut lines under normal and HT stress conditions. Conclusions Our results suggested that JrDof3 TF contributes to improve the HT stress response of JrGRAS2, which could effectively control the expression of HSPs to enhance HT stress tolerance. JrGRAS2 is an useful candidate gene for heat response in plant molecular breeding. Electronic supplementary material The online version of this article (10.1186/s12870-018-1568-y) contains supplementary material, which is available to authorized users.

Glutathione S-transferases (GSTs) are important plant proteins involved in biotic and abiotic stress responses. A gene from Juglans regia, JrGSTTau1 was previously cloned and functionally characterized as an enzyme involved in improving cold tolerance in plants. To clarify the functional mechanism of JrGSTTau1 and its role in stress response, here, the JrGSTTau1 promoter including the up-stream regulators was examined using yeast one-hybrid together with transient expression assays, and the osmotic stress response ability was confirmed by comparing with wild-type plants. The 1500 bp JrGSTTau1 promoter displayed high GUS expression activity and was enhanced by mannitol stress. The promoter is composed of abundant cis-elements, some of which were osmotic stress response-related motifs, such as ABRE, DRE and MYB, indicating that the expression of JrGSTTau1 is regulated by potential up-stream regulators under abiotic stress. The transcription factors (TFs) of JrDREB2A, JrMYC2, JrMYB44, JrDof1 and JrWRKY7 were identified, which shared a similar response with JrGSTTau1 when exposed to PEG6000 in walnut leaf and root. These results implied that JrDREB2A, JrMYC2, JrMYB44, JrDof1 and JrWRKY7 may act as up-stream regulators of JrGSTTau1 to regulate or combine functionality with JrGSTTau1 in osmotic stress response. Furthermore, compared with the WT plants, the transgenic tobacco plants that overexpress JrGSTTau1 showed improved tolerance to drought induced by osmotic stress, in which antioxidant enzymes, proline and reactive oxygen species (ROS) are involved. Our results demonstrated the positive role played by JrGSTTau1 in osmotic tolerance, which is regulated by multiple up-stream regulators.

Eukaryotic translation initiation factor 1A (eIF1A) functions as an mRNA scanner and AUG initiation codon locator. However, few studies have clarified the role of eIF1A in abiotic stress. In this study, we cloned eIF1A (TheIF1A) from Tamarix hispida and found its expression to be induced by NaCl and polyethylene glycol (PEG) in roots, stems and leaves. Compared to a control, TheIF1A root expression was increased 187.63-fold when exposed to NaCl for 6 h, suggesting a potential abiotic stress response for this gene. Furthermore, transgenic tobacco plants overexpressing TheIF1A exhibited enhanced seed germination and a higher total chlorophyll content (tcc) under salt and mannitol stresses. Increased superoxide dismutase (SOD), peroxidase (POD), glutathione transferase (GST) and glutathione peroxidase (GPX) activities, as well as decreased electrolyte leakage (EL) rates and malondialdehyde (MDA) contents, were observed in TheIF1A-transgenic tobacco and T. hispida seedlings under salt and mannitol stresses. Histochemical staining suggested that TheIF1A improves reactive oxygen species (ROS) scavenging in plants. Moreover, TheIF1A may regulate expression of stress-related genes, including TOBLTP, GST, MnSOD, NtMPK9, poxN1 and CDPK15. Moreover, a 1352-bp promoter fragment of TheIF1A was isolated, and cis-elements were identified. Yeast one-hybrid assays showed that ThDof can specifically bind to the Dof motif present in the promoter. In addition, ThDof showed expression patterns similar to those of TheIF1A under NaCl and PEG stresses. These findings suggest the potential mechanism and physiological roles of TheIF1A. ThDof may be an upstream regulator of TheIF1A, and TheIF1A may function as a stress response regulator to improve plant salt and osmotic stress tolerance via regulation of associated enzymes and ROS scavenging, thereby reducing cell damage under stress conditions.

Aspergillus egyptiacus is an important fungus during the fermentation process of dark tea. However, there is little study on genetic information about A. egyptiacus. In this study, A. egyptiacus was is isolated from dark tea and first sequenced. The annotation and analysis also have been done for the mitochondrial genome. The length of A. egyptiacus mitochondrial genome is 66,564 bp and include 41 genes. Similar to most fungus, 15 protein-coding genes (PCGs), 24 transfer RNA (tRNA) genes, 2 ribosomal RNA (rRNA) genes, and one non-coding control region (D-loop) were identified in the strand of mitochondrial genome. The GC content is 26.55% and the reconstructed phylogenetic supported the placement of A. egyptiacus in Eurotiomycetes clade. The mitochondrial genome information also may supply references for utilization of A. egyptiacus.

Chloroplast genomes are widely used in genetic engineering, molecular marker development, and phylogeny. In order to analyze the complete chloroplast genome of Dianthus caryophyllus, the complete c...

The paper mulberry, Broussonetia kazinoki × Broussonetia papyifera, is a species within the family Moraceae, also is an economic and ecological plant. Complete chloroplast genome of paper mulberry was reported in this study. The total genome size was 160,903 bp in length, which is separated by a large single copy (LSC) region and a small single copy (SSC) region (89,220 and 20,079 bp in length, respectively). There were a total of 134 predicted functional genes, including 80 protein-coding genes (PCGs), eight ribosomal RNA (rRNA) genes, and 46 transfer RNA (tRNA) genes. The overall G + C content of the paper mulberry chloroplast genome was 35.74%, while the corresponding values of the LSC, SSC, and IR regions are 33.33%, 28.50%, and 42.72%, respectively. The phylogenetic analysis between Moraceae trees showed chloroplast genome of paper mulberry was closely related to Morus multicaulis.

Dehydration-responsive element-binding (DREB) transcription factors are important abiotic stress tolerance related genes, and some reports on the roles of DREB have primarily addressed herbal plants. To explore the abiotic stress tolerance role of DREB (ThDREB) from Tamarix hispida, a ThDREB gene with a complete ORF of 783 bp that encodes a 28.74 kDa protein with 260 amino acids, was isolated and functionally annotated. ThDREB expression was highly induced by NaCl, PEG, NaHCO3 and CdCl2 treatments, and the highest expression level (369.2-fold of control) was found for the roots that were under NaCl stress for 6 h. The tobacco plants that were transformed by ThDREB were conferred with higher germination rates, fresh weights and root lengths than the wild type (WT) tobacco plants under NaCl and mannitol treatments. The total chlorophyll content (tcc), superoxide dismutase (SOD) and peroxidase (POD) activities were also higher in the transgenic lines in comparison with the WT, and the malondialdehyde (MDA) and H2O2 content, electrolyte leakage (EL) rate and ROS as tracked by staining were generated to a lesser degree in ThDREB transgenic plants than in the WT under NaCl and mannitol stress. Furthermore, the transient overexpression analysis of ThDREB in T. hispida also improved plant salt and drought tolerance in comparison with the empty vector-transformed lines. Our results indicated that ThDREB expression could effectively improve tolerance to salt and drought stress by enhancing the antioxidase activity that keeps the ROS at a low accumulation level and makes them easy to scavenge.

Ethylene responsive factors (ERFs) play important roles in the abiotic stress; however, only a few ERF genes from woody plants have been functionally characterized. In the present study, an ERF gene from Betula platyphylla (birch), BpERF11, was functionally characterized in response to abiotic stress. BpERF11 is a nuclear protein, which could specifically bind to GCC boxes and DRE motifs. BpERF11-overexpressing and BpERF11 RNA interference (RNAi) knockdown plants were generated for gain- and loss-of-function analysis. BpERF11 negatively regulates resistance to salt and severe osmotic stress, and the transgenic birch plants overexpressing BpERF11 shows increased electrolyte leakage and malondialdehyde (MDA) contents. BpERF11 inhibits the expression of an AtMYB61 homologous gene, resulting in increased stomatal aperture, which elevated the transpiration rate. Furthermore, BpERF11 downregulates the expression of P5CS, SOD and POD genes, but upregulates the expression of PRODH and P5CDH, which results in reduced proline levels and increased reactive oxygen species (ROS) accumulation. BpERF11 also significantly inhibits the expression of LEA and dehydrin genes that involve in abiotic stress tolerance. Therefore, BpERF11 serves as a transcription factor that negatively regulates salt and severe osmotic tolerance by modulating various physiological processes.

Camellia oleifera, an evergreen small tree or shrub with high medicinal and ecological values, is mainly distributed in subtropical montane regions of China. In this study, complete chloroplast genome was reported for Camellia oleifera in Hainan, China. The results showed that the whole genome was 156,996 bp in length, including a pair of inverted repeats (IRs) of 26,025 bp, a large single copy (LSC) region of 86,649 bp and a small single copy (SSC) region of 18,297 bp. The genome contained a total of 115 different genes, including 81 protein-coding genes, 30 tRNA genes, and four rRNA genes. Among these genes, eight genes contain a single intron and two genes contain two introns. The total GC content of Camellia oleifera was 37.29%. The maximum likelihood phylogenetic analysis based on 21 chloroplast genomes showed that Camellia oleifera was similar to Camellia danzaiensis.

JrGSTTau1 is an important candidate gene for plant chilling tolerance regulation. A tau subfamily glutathione S-transferase (GST) gene from Juglans regia (JrGSTTau1, GeneBank No.: KT351091) was cloned and functionally characterized. JrGSTTau1 was induced by 16, 12, 10, 8, and 6 °C stresses. The transiently transformed J. regia showed much greater GST, glutathione peroxidase (GPX), superoxide dismutase (SOD), and peroxidase (POD) activities and lower H2O2, malondialdehyde (MDA), reactive oxygen species (ROS), and electrolyte leakage (EL) rate than prokII (empty vector control) and RNAi::JrGSTTau1 under cold stress, indicating that JrGSTTau1 may be involved in chilling tolerance. To further confirm the role of JrGSTTau1, JrGSTTau1 was heterologously expressed in tobacco, transgenic Line5, Line9, and Line12 were chosen for analysis. The germinations of WT, Line5, Line9, and Line12 were similar, but the fresh weight, primary root length, and total chlorophyll content (tcc) of the transgenic lines were significantly higher than those of WT under cold stress. When cultivated in soil, the GST and SOD activities of transgenic tobacco were significantly higher than those of WT; however, the MDA and H2O2 contents of WT were on average 1.47- and 1.96-fold higher than those of Line5, Line9, and Line12 under 16 °C. The DAB, Evans blue, and PI staining further confirmed these results. Furthermore, the abundances of NtGST, MnSOD, NtMAPK9, and CDPK15 were elevated in 35S::JrGSTTau1 tobacco compared with WT. These results suggested that JrGSTTau1 improves the plant chilling tolerance involved in protecting enzymes, ROS scavenging, and stress-related genes, indicating that JrGSTTau1 is a candidate gene for the potential application in molecular breeding to enhance plant abiotic stress tolerance.

The complete nucleotide sequence of Juglans regia chloroplast genome (cpDNA) was carried out using Illumina Hiseq 2500. The genome is 160 537 bp in length, and the overall base composition of H-strand is 31.59% for A, 18.35% for C, 17.76% for G and 32.30% for T. Similar to the other higher plants, cpDNA have a large single copy (LSC) region of 90 059 bp and a small single copy(SSC) of 18 412 bp, is separated by a pair of inverted repeats (IRa and IRb) of 26 033 bp. There are 113 genes in the cpDNA, including 80 protein-coding genes, 4 ribosomal RNA genes (4 rRNA species), 36 transfer RNA genes (19 tRNA species). To further investigate the evolution status of J. regia in the level of chloroplast genome, tree constructed using MEGA 6.0 with NJ and ML methord demonstrated J. regia was clustered in Fagales, which was identical with APG III.