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The allelopathic effects of fescue (Festuca arundinacea) variety ‘Milennium’ 2 leaf aqueous extracts on 10 fescue varieties were assayed. The 50 mg·ml-1 treatment increased the biomass and physiological indices (soluble sugar content, malondialdehyde content and root activity), whereas the 100 mg·ml-1 and 150 mg·ml-1 treatments were inhibitory. There was variable response of fescue varieties to different treatments, the varieties (Aries, Millennium2, and Free star) were most sensitive to the leaf extracts, while Greenlabel, Lenge maste, and Arid3 varieties were least sensitive. The treatments most affected the physiological factor, relative electrolyte leakage, followed by the soluble sugar content, malondialdehyde content, and root activity. These results suggested that sowing an appropriate combination and proportion of grass varieties may be better to improve the lawn quality than the continuous use of a single grass variety.

Metallothionein (MT) is a cysteine-rich, low-molecular-weight protein that can bind to cadmium ions and reduce their toxicity to plants. In this study, we cloned the PaMT3-1 gene encoding an unstable protein of 63 amino acids from the cadmium hyperaccumulator Phytolacca americana. The gene was inserted into a plant expression vector and introduced into tobacco plants. The cadmium content of the transgenic plants was measured after treatment with 100 mM CdCl2 for 7 days. Transgenic and wild-type roots had similar cadmium contents, whereas the cadmium content of transgenic leaves was 66.28–78.70% of the wild type. The transport coefficient of cadmium in transgenic plants was decreased by 23.31–35.52% relative to the wild type. According to various physiological indexes, including malondialdehyde content, relative electrolyte leakage, root activity, and soluble sugar content, the transgenic plants performed better than the wild type. The PaMT3-1 gene can significantly improve plant resistance to cadmium and has potential as an important gene resource in phytoremediation. Our findings could also contribute to an understanding of complex processes and mechanisms involved in phytoremediation. Over-expressing a metallothionein gene PaMT3-1 from Phytolacca americana in tobacco plants showed enhanced cadmium tolerance that would be important gene resource for phytoremediation.

Messenger RNAs exchanged between scions and rootstocks of grafted plants seriously affect their traits performance. The study goals were to identify the long-distance mRNA transmission events in grafted willows using a transcriptome analysis and to reveal the possible effects on rooting traits. The results showed that the Salix matsudana variety 9901 has better rooting ability than YJ, which reasonably improved the rooting performance of the heterologous grafts 9901 (scion)/YJ (rootstock). A transcriptome analysis showed that 2948 differentially expressed genes (DEGs) were present in the rootstock of 9901/YJ grafted plants in comparison with YJ/YJ. Among them, 692 were identified as mRNAs moved from 9901 scion based on SNP analysis of two parents. They were mostly 1001–1500 bp, had 40–45% GC contents, or had expression abundance values less than 10. However, mRNAs over 4001 bp, having 50–55% GC contents, or having expression abundance values of 10–20 were preferentially transferred. Eight mRNAs subjected to long-distance trafficking were involved in the plant hormone pathways and may significantly promote the root growth of grafted plants. In summary, heterologous grafts of Salix matsudana could efficiently influence plant rooting of the mRNAs transport from scion to rootstock.

Solid-state fermented Omar’s was dried using microwave vacuum drying (MVD) and infrared freeze-drying (IFD). Hot air drying (AD) and traditional vacuum freeze-drying (FD) were used as controls. The...

Different drying methods (spray drying (SD), vacuum drying (VD), microwave vacuum drying (MVD), and infrared vacuum drying (IFVD)) were applied in order to compare the hygroscopicity behavior of ch...

Polyploidy is a common phenomenon among willow species. In this study, genome sequencing was conducted for Salix matsudana Koidz (also named Chinese willow), an important greening and arbor tree species, and the genome of this species was compared with those of four other tree species in Salicaceae. The total genome sequence of S. matsudana was 655.72 Mb in size, with repeated sequences accounting for 45.97% of the total length. In total, 531.43 Mb of the genome sequence could be mapped onto 38 chromosomes using the published genetic map as a reference. The genome of S. matsudana could be divided into two groups, the A and B genomes, through homology analysis with the genome of Populus trichocarpa, and the A and B genomes contained 23,985 and 25,107 genes, respectively. 4DTv combined transposon analysis predicted that allotetraploidy in S. matsudana appeared ~4 million years ago. The results from this study will help reveal the evolutionary history of S. matsudana and lay a genetic basis for its breeding.

The base composition of the chloroplast genes is of great interest because they play a highly significant role in the evolutionary development of the plants. Evaluation of the 48 chloroplast protein-coding genes of

Expansin is an indispensable cell wall protein, involved in plant growth and resistance to stress. Based on the sequencing genome data, a total of 34 expansin genes were identified on 14 chromosomes in Salix purpurea , which were grouped into 4 subfamilies. The analysis of the physicochemical properties showed that most expansin proteins were in weakly alkaline, had a higher aliphatic index and more stable protein structure. The gene sequence was more conservative among the members in the same subfamily with the amino acid identity between 34.2% and 99.4%, while that was between 15.0% and 39.8% among the members in the different subfamilies. Also, the same subfamily genes had similar exon-intron structures, but the different subfamily genes showed that much differently. The codon usage analysis revealed that there are 5 high-frequency codons in Salix purpurea expansin genes. The codon usage bias was much affected by natural selection. The synteny analysis showed that the expansin genes divided in corresponce to whole-genome duplication events in willow. The results here would help us to understand well the role and status of expansin genes in the growth and development of Salix purpurea . It will be helpful for further study on the expansins functions.

As important cell wall proteins in plants, expansins are involved in a serious of abiotic stress resistance such as drought, heat, salt, even heavy metals. To understand the role of expansins in cadmium (Cd) stress, we analyzed the expression patterns of 36 expansin genes in Populus tomentosa. A Cd-induced expansin gene, PtoEXPA12, was identified, cloned, and transformed into tobacco plants. After treatment with Cd, the transgenic plants showed stronger symptoms of Cd toxicity as to the wild-type tobacco plants. Further physiological tests showed that the transformants had higher relative electrolyte leakage and superoxide dismutase activity, more malondialdehyde and H2O2 content, and lower chlorophyll content in Cd stress. Cd content measurement showed it is 1.40-2.07-fold higher and 1.29-1.38-fold higher separately in roots and shoots of transgenic plants than those in wild-type plants, while the transfer coefficient value kept invariably even decreased. Therefore, PtoEXPA12 was really involved in Cd uptake and accumulation, and led to Cd toxicity of cells. It would be a potentially applicable part in phytoremediation system.

Agrostis stolonifera L. 'Penn A-4' is a common creeping bentgrass species that is widely used in urban landscaping and golf courses. To prolong the green stage of this grass, a dehydrin gene PicW isolated from Wilson's spruce (Picea wilsonii) was transformed into plants of 'Penn A-4' cultivar via a straightforward stolon node infection system. A putative transgenic plant was obtained and its tolerance to low-temperature stress was evaluated. When the transgenic line was subjected to a freezing (- 5 °C) treatment, it showed better viability and more robust physiology than wild type, as evidenced by higher soluble sugar and proline contents, and lower relative electrical conductivity and malondialdehyde content. The transgenic line also showed tolerance to a chilling treatment (5 °C), although its performance was not significantly different from that of wild-type plants. Overall, the research here clearly revealed the explicit role of PicW in increasing freezing tolerance of grass at the whole-plant level, and demonstrated that the straightforward stolon node transformation method could be well used to genetically modify turfgrass. The obtained transgenic line might be as genetic resource for breeding program and practiced to grow in cold temperate zones.

With the vigorous development of nuclear power and the shortage of terrestrial uranium resources, the extraction uranium from seawater is extremely attractive for human development. Herein, we first report ZIF-8 in-situ growth on amidoximerized polyacrylonitrile (PAO) porous materials. The porous material is a small sphere with certain mechanical strength synthesized by solvent-induced phase separation method. Because ZIF-8 nanocrystals are well-formed and evenly distributed within the PAO beads, ZIF-8/PAO has a high specific surface area (386 m2 g-1) and rich pore structure. At adsorption experiment, the highest adsorption capacity of ZIF-8/PAO reached 803 mg g-1 at pH = 4. Furthermore, competitive adsorption experiment and simulated seawater test was studied. The selectivity for uranium was excellent (Kd = 1.7 × 105 mL g-1) and uranium adsorption rate reached 99% at 3 ug L-1. XPS analysis shows that U(VI) is chelated by imidazole-N atoms and amidoxime groups in ZIF-8/PAO. Therefore, ZIF-8/PAO can be considered a highly promising adsorbent for uranium extraction from wastewater and seawater.

This work investigated and compared the dynamic cavitation characteristics between low and high boiling-point phase-shift nanodroplets (NDs) under physiologically relevant flow conditions during focused ultrasound (FUS) exposures at different peak rarefactional pressures. A passive cavitation detection (PCD) system was used to monitor cavitation activity during FUS exposure at various acoustic pressure levels. Root mean square (RMS) amplitudes of broadband noise, spectrograms of the passive cavitation detection signals, and normalized inertial cavitation dose (ICD) values were calculated. Cavitation activity of low-boiling-point perfluoropentane (PFP) NDs and high boiling-point perfluorohexane (PFH) NDs flowing at in vitro mean velocities of 0–15 cm/s were compared in a 4-mm diameter wall-less vessel in a transparent tissue-mimicking phantom. In the static state, both types of phase-shift NDs exhibit a sharp rise in cavitation intensity during initial FUS exposure. Under flow conditions, cavitation activity of the PFH NDs reached the steady state less rapidly compared to PFP NDs under the lower acoustic pressure (1.35 MPa); at the higher acoustic pressure (1.65 MPa), the RMS amplitude increased more sharply during the initial FUS exposure period. In particular, the RMS-time curves of the PFP NDs shifted upward as the mean flow velocity increased from 0 to 15 cm/s; the RMS amplitude of the PFH ND solution increased from 0 to 10 cm/s and decreased at 15 cm/s. Moreover, amplitudes of the echo signal for the low boiling-point PFP NDs were higher compared to the high boiling-point PFH NDs in the lower frequency range, whereas the inverse occurred in the higher frequency range. Both PFP and PFH NDs showed increased cavitation activity in the higher frequency under the flow condition compared to the static state, especially PFH NDs. At 1.65 MPa, normalized ICD values for PFH increased from 0.93 ± 0.03 to 0.96 ± 0.04 and from 0 to 10 cm/s, then decreased to 0.86 ± 0.05 at 15 cm/s. This work contributes to our further understanding of cavitation characteristics of phase-shift NDs under physiologically relevant flow conditions during FUS exposure. In addition, the results provide a reference for selecting suitable phase-shift NDs to enhance the efficiency of cavitation-mediated ultrasonic applications.

Leaf elongation rates (LER) is sensitive to salt stress and osmotic stress, and gibberellic acid (GA) may mediate stress-inhibition of leaf elongation by affecting genes controlling cell expansion. The objectives of this study were to examine the differential inhibitory effects of osmotic stress and salt stress on LER for fast- and slow-growing genotypes of tall fescue (Festuca arundinacea) and to determine whether GA could mitigate stress-induced decline in LER. Plants of fast-growing ‘K-31′ and slow-growing ‘Bonsai’ were grown hydroponically and treated with GA under either osmotic or salt stress. LER of both genotypes were inhibited by osmotic and salt stress (46–86%) due to reduced cell elongation and production rate. ‘Bonsai’ LER was reduced to a greater extent than that of ‘K-31′ due to greater reduction in cell production rate. Exogenous GA application significantly enhanced LER regardless of stress for both genotypes, which was more pronounced in ‘Bonsai’ than in ‘K-31′ caused by greater cell elongation and production rates. Quantitative PCR analysis revealed that four expansin genes (EXPA4, EXPA5, EXPA7 and EXPB7) and one XET gene (XET2) were down-regulated by osmotic stress and EXPA7 was down-regulated by salt stress in both genotypes. Three expansin genes (EXPA4, EXPA5 and EXPA7) were up-regulated by GA treatment in both genotypes under non-stress conditions, in which EXPA4 was also up-regulated by GA treatment in both genotypes under osmotic stress. The expression level of XET1 and XET3 increased in ‘K-31′ and ‘Bonsai’, respectively, with exogenous GA treatment under non-stress and salt stress. This study demonstrated the roles of GA regulation of genetic variations in leaf differential responses to osmotic and salt stress involving different expansins and XET genes.

Expansins are cell wall proteins involved in cell wall loosening and structural remodeling. In this study, we evaluated the transcript levels of 36 expansin genes in Populus tomentosa under heat stress (42 °C) and normal growth conditions (25 °C). One expansin gene, PttEXPA8, significantly up-regulated in leaves under heat stress, was cloned and transformed into tobacco (Nicotiana tobacum). The transgenic and wild-type tobacco plants were subjected to a 10-day heat treatment, and morphological and physiological parameters (relative electrolyte leakage, malondialdehyde content, chlorophyll content, and superoxide dismutase activity) were measured. The results showed that the transgenic plants were more heat-resistant than the wild-type plants. It concluded that PttEXPA8 could be a valuable gene resource conferring heat resistance. The report here contributes to our knowledge of the functions of expansins in woody plants, and also contributes to our knowledge of the molecular mechanism of heat tolerance in poplar.

In situ detection of certain specific enzyme activities in cells is deeply attached to tumor diagnosis. Conventional enzyme-responsive fluorescent probes have difficulty detecting targeted enzymes in situ in cells due to the low detection accuracy caused by the spread of fluorescence probes. In order to solve this problem, we have designed and synthesized an enzyme-responsive, water-soluble fluorescent probe with AIE characteristics, which could aggregate and precipitate to produce in situ fluorescence when reacting with the targeted enzyme in cells. The AIE fluorophore (TPEQH) was utilized to design the enzyme-responsive, fluorescent probe (TPEQHA) by introducing a phosphate group on to it, which could be specifically decomposed by the targeted enzyme, namely alkaline phosphatase (ALP). In tumor cells, TPEQH was highly produced due to the interaction of phosphate on the TPEQHA and the overexpressed ALP. Water-insoluble TPEQH then precipitated and release fluorescence in situ, thereby successfully detecting the ALP. Furthermore, the expression level of ALP could be determined by the fluorescence intensity of TPEQH with higher accuracy due to the inhibition of TPEQH leak, which demonstrated a potential application of in suit ALP detection in both clinical diagnosis and scientific research of tumor.

Expansins play a pivotal role in plant adaptation to environmental stress via cell wall loosening. To evaluate the roles of expansin in response to different environmental stress conditions, the expansin gene PttEXPA8 from Populus tomentosa was transformed into tobacco. Analysis of physiological indices demonstrated the transgenic plants with improved resistance to heat, drought, salt, cold, and cadmium stress but to different extents. In mature plants, PttEXPA8 exerted the greatest effect on heat stress, with a response index value of 137.46%, followed by drought, cadmium, cold, and salt stress with response index values of 101.04%, 70.61%, 69.95%, and 54.68%, respectively. Over-expression of PttEXPA8 resulted in differential responses in physiological indices to the stresses. Soluble sugar content showed the highest response to the stresses, with an average response index value of 29.29%, whereas the absolute response index value for malondialdehyde content, relative electrolyte leakage, chlorophyll content, and superoxide dismutase activity ranged from 11.01% to 19.21%. The present results provide insight into the roles of expansin in stress resistance in Populus.

Low temperature is a major limiting factor for plant growth and development. Dehydrin proteins are generally induced in response to low-temperature stress. In previous research, a full-length dehydrin gene,PicW2, was isolated fromPicea wilsoniiand its expression was associated with hardiness to cold. In order to gain insight into the mechanism of low-temperature tolerance by studying its three-dimensional crystal structure, prokaryotically expressed PicW2 dehydrin protein was purified using chitosan-affinity chromatography and gel filtration, and crystallized using the vapour-diffusion method. The crystal grew in a condition consisting of 0.1 MHEPES pH 8.0, 25%(w/v) PEG 3350 using 4 mg ml−1protein solution at 289 K. X-ray diffraction data were collected from a crystal at 100 K to 2.82 Å resolution. The crystal belonged to space groupC121, with unit-cell parametersa= 121.55,b= 33.26,c= 73.39 Å, α = γ = 90.00, β = 109.01°. The asymmetric unit contained one molecule of the protein, with a corresponding Matthews coefficient of 2.87 Å3 Da−1and a solvent content of 57.20%. Owing to a lack of structures of homologous dehydrin proteins, molecular-replacement trials failed. Data collection for selenium derivatization of PicW2 and crystal structure determination is currently in progress.

Expansins are essential components of plant cell wall and play an important role in plant growth, development, and stress resistance via loosening function. To understand the codon usage pattern of expansin genes, we gained the sequence data of expansin genes from eight plant species. Statistics analysis showed obvious codon characteristics between monocot and dicot plants. Comparably, expansin genes in monocot plants had really higher GC content, more high-frequency codons, and more optimal codons than that in dicot plants. Several monocot plants performed somehow as dicot plants in a few characters. Codon information of expansin genes might contribute to the understanding of the relationship and evolution clues between monocot and dicot plants. It further gained insight into the improvement of the gene expression and roles.

Phytochelatins chelate heavy metal ions to decrease their toxicity. The chelates are then transferred to, and stored in, the vacuole. Phytochelatin synthase (PCS), which is involved in phytochelatin synthesis, is thought to be a key enzyme for phytoremediation. In this study, a PCS gene encoding phytochelatin synthase was cloned from poplar (Populus tomentosa Carr.), a widely grown model woody plant that accumulates high levels of heavy metals, especially cadmium. Poplar is considered to have potential applications in phytoremediation. The full-length PtPCS cDNA (1512-bp) encoded a polypeptide of 503 amino acid residues. The PtPCS cDNA was transferred into tobacco by Agrobacterium-mediated leaf disk transformation. The transgenic and wild-type (WT) lines of tobacco were subjected to a one time Cd treatment (90 μmol Cd2+) for 30 days, and then evaluated to determine their Cd tolerance. We evaluated morphological and physiological indices including leaf relative electrolyte leakage, malondialdehyde content, total superoxide dismutase activity, chlorophyll content and root activity. Compared with WT plants, the transgenic plants expressing PtPCS grew better in the Cd treatment and showed significantly higher Cd tolerance. Compared with WT plants, the transgenic lines accumulated higher concentrations of Cd (1.7 to 3.0-fold higher Cd concentration in roots; 1.24 to 2.28-fold higher Cd concentration in leaves). However, the transfer coefficient was lower in the transgenic lines than in wild type. We concluded that PtPCS encodes a functional PCS that may be involved in Cd tolerance and accumulation, but not in Cd transport.

Heavy metal ATPase (HMA) plays an important role in phytoremediation via long-distance transportation from root to shoot. In this report, we identified a heavy metal ATPase gene, PtoHMA5, from Populus tomentosa Carr. Its encoded peptide consists of 967 amino acids and has eight trans-membrane motifs inside. Tobacco plants were transformed with this gene via Agrobacterium tumefaciens-mediated method. After exposure to 50mg/LCdCl2 for 10d, the transgenic lines displayed higher cadmium accumulation in leaves than did the wild-type plants with an absolute increase of 25.04%, while the transfer coefficient increased by 16.01%-43.25%. Physiological testing including assessment of relative electrolytic leakage (REL), malondialdehyde (MDA) content, and chlorophyll content revealed that the transgenic lines were seriously affected when compared with the wild-type plants. In summary, PtoHMA5 is really involved in cadmium transport from root to shoot but is not associated with the removal of cadmium toxicity.

Metallothioneins (MTs) are known for their heavy metal deoxidation during phytoremediation. To estimate their roles in the cadmium (Cd) hyperaccumulator Phytolacca americana L., three MT genes, PaMT3-1, PaMT3-2 and PaMT3-3, belonging to the MT3 subfamily were cloned. They separately encoded 63, 65 and 65 amino acids, containing12, 10 and 11 cysteines (Cys), respectively. Each gene was individually transformed and expressed in Escherichia coli cells. A Cd-resistance assay showed that the recombinant strains had enhanced survival rates, especially those containing PaMT3-1 and PaMT3-3. Additionally, the recombinant strains were high Cd accumulators, with the recombinant PaMT3-1's maximum accumulation being 2.16 times that of the empty vector strains. The numbers of cysteines and the structures of MT proteins were associated with the Cd enrichment and resistance capabilities. PaMT3-1 could be an effective gene resource in future plant Cd remediation-related breeding programs.

A cold-induced gene of 669 bp in length without introns, PicW, was cloned from Picea. wilsonii, a cold tolerant conifer species. Sequence analysis showed that it was a member of the dehydrin family because of its conserved amino acid constitution and protein secondary structure. The protein was rich in hydrophilic amino acids such as alanine, lysine, glutamic acid, glutamine and threonine, but devoid of two hydrophobic amino acids, cysteine and tryptophan. The PicW gene contained five repeated motifs homologous to the core K-segment in dehydrins. Protein secondary structure prediction showed that PicW comprised 29 % α-helix, mostly in the K-homologous segment, and random coils. The PicW gene was cloned into the expression vector PEZR(K)-LC under the 35S promoter and transformed into tobacco plants. After treatment at −5 °C for 3 h, all of the tobacco plants were wilting. However, the transgenic plants showed better growth performance than wild-type plants. Further tests of physiological indexes including relative electrolyte leakage and malondialdehyde content, proline and soluble sugar content also revealed significant differences between the wild-type and transgenic tobacco plants. It was concluded that the PicW gene could be an important gene resource for freezing-tolerant plant breeding.

The aim of this paper is to identify key genes in lung adenocarcinoma (LUAD) through weighted gene co-expression network analysis (WGCNA), and to further understand the molecular mechanism of LUAD. 107 gene expression profiles were downloaded from GSE10072 in the GEO database. We performed rigorous processing of the initial gene expression profile data. Subsequently, we used WGCNA to identify disease-driven modules and enforced functional enrichment analysis. The key genes were defined as the most connected genes in the driver module and were validated using the GSE75037 and TCGA database. GSE10072 removed 41 unpaired lung samples and 4 outliers. By analyzing the 62 samples using WGCNA, we obtained 26 modules and identified the brown and magenta modules as the driving modules for the LUAD. We found that the “Cell cycle”, “Oocyte meiosis” and “Progesterone-mediated oocyte maturation” pathways may be related to the occurrence of LUAD. GSE75037 removed 8 outlier and obtained 2909 differentially expressed genes (DEGs), 26 genes (9 genes in the brown module, 17 genes in the magenta module) overlap with key genes in the driver module. The results of the survival analysis suggest that 19 genes were significantly correlated with the patient’s survival time, including KPNA2, FEN1, RRM2, TOP2A, CENPF, MCM4, BIRC5, MELK, MAD2L1, CCNB1, CCNA2, KIF11, CDKN3, NUSAP1, CEP55, AURKA, NEK2, KIF14 and CDCA8, which may be potential biomarkers or therapeutic targets for LUAD. In this study, we provide a theoretical basis for further understanding the biological mechanism of LUAD through bioinformatics analysis of LUAD.

The rice blast resistance gene Pid3 encodes a nucleotide-binding-site leucine-rich repeat (NBS-LRR) protein. This gene was cloned from the rice ‘Digu’ (indica) by performing a genome-wide comparison of the NBS-LRR gene family between two genome-sequenced varieties, ‘9311’ (indica) and ‘Nipponbare’ (japonica). In this study, we performed functional analysis of Pid3-A4, an ortholog of Pid3 revealed by allele mining in the common wild rice A4 (Oryza rufipogon). The predicted protein encoded by Pid3-A4 shares 99.03% sequence identity with Pid3, with only nine amino-acid substitutions. In wild rice plants, Pid3-A4 is constitutively expressed, and its expression is not induced by Magnaporthe oryzae isolate Zhong-10-8-14 infection. Importantly, in transgenic plants, Pid3-A4, as compared with Pid3, displays a distinct resistance spectrum to a set of M. oryzae isolates, including those that prevail in the rice fields of Sichuan Province. Therefore, Pid3-A4 should be quite useful for the breeding of rice blast resistance, especially in southwestern China.

Leaf elongation rate (LER) is an important factor controlling plant growth and productivity. The objective of this study was to determine whether genetic variation in LER for a fast-growing (‘K-31’), and a dwarf cultivar (‘Bonsai’) of tall fescue (Festuca arundinacea) and gibberellic acid (GA) regulation of LER were associated with differential expression of cell-expansion genes. Plants were treated with GA3, trinexapac-ethyl (TE) (GA inhibitor), or water (untreated control) in a hydroponic system. LER of ‘K-31’ was 63% greater than that of ‘Bonsai’, which corresponded with 32% higher endogenous GA4 content in leaf and greater cell elongation and production rates under the untreated control condition. Exogenous application of GA3 significantly enhanced LER while TE treatment inhibited leaf elongation due to GA3-stimulation or TE-inhibition of cell elongation and production rate in leaves for both cultivars. Real-time quantitative polymerase chain reaction analysis revealed that three α-expansins, one β-expansin, and three xyloglucan endotransglycosylase (XET) genes were associated with GA-stimulation of leaf elongation, of which, the differential expression of EXPA4 and EXPA7 was related to the genotypic variation in LER of two cultivars. Those differentially-expressed expansin and XET genes could play major roles in genetic variation and GA-regulated leaf elongation in tall fescue.

DNA methylation is a general epigenetic mechanism for plants, animals, and fungi to adapt to environmental variation. Two biotypes of the Russian wheat aphid (Diuraphis noxia), Biotype 1 and Biotype 2, have different virulence to host plants. In this study, in addition to a high polymorphism, DNA methylation at cytosines were observed in genomic fragments of four genes in Biotype 1 and Biotype 2, after the genomic DNA was treated with sodium bisulfite. These genes presumably encode proteins and enzymes in salivary glands of aphids. The two Biotype 1 showed different methylation levels, that is, Biotype 1 showed a higher methylation on the four genes. Two thirds of methyl cytosines were in a sequence context of CHH (H = A, C, or T). Some polymorphism and methylation sites were located at important positions in terms of enzyme function, such as close to catalytic residues or inhibitor binding residues. These findings may provide clues to explore the evolutionary mode between Russian wheat aphid virulence and resistance genes of host plants.

MicroRNAs (miRNAs) are small, non-coding RNAs that regulate the expression of target mRNAs in plant growth, development, abiotic stress responses, and pathogen responses. Cold stress is one of the most common abiotic factors affecting plants, and it adversely affects plant growth, development, and spatial distribution. To understand the roles of miRNAs under cold stress in Populus tomentosa, we constructed two small RNA libraries from plantlets treated or not with cold conditions (4°C for 8 h). High-throughput sequencing of the two libraries identified 144 conserved miRNAs belonging to 33 miRNA families and 29 new miRNAs (as well as their corresponding miRNA(∗)s) belonging to 23 miRNA families. Differential expression analysis showed that 21 miRNAs were down-regulated and nine miRNAs were up-regulated in response to cold stress. Among them, 19 cold-responsive miRNAs, two new miRNAs and their corresponding miRNA(∗)s were validated by qRT-PCR. A total of 101 target genes of the new miRNAs were predicted using a bioinformatics approach. These target genes are involved in growth and resistance to various stresses. The results demonstrated that Populus miRNAs play critical roles in the cold stress response.

MicroRNAs (miRNAs) are small RNAs, generally of 20-23 nt, that down-regulate target gene expression during development, differentiation, growth, and metabolism. In Populus, extensive studies of miRNAs involved in cold, heat, dehydration, salinity, and mechanical stresses have been performed; however, there are few reports profiling the miRNA expression patterns during pathogen stress. We obtained almost 38 million raw reads through Solexa sequencing of two libraries from Populus inoculated and uninoculated with canker disease pathogen. Sequence analyses identified 74 conserved miRNA sequences belonging to 37 miRNA families from 154 loci in the Populus genome and 27 novel miRNA sequences from 35 loci, including their complementary miRNA* strands. Intriguingly, the miRNA* of three conserved miRNAs were more abundant than their corresponding miRNAs. The overall expression levels of conserved miRNAs increased when subjected to pathogen stress, and expression levels of 33 miRNA sequences markedly changed. The expression trends determined by sequencing and by qRT-PCR were similar. Finally, nine target genes for three conserved miRNAs and 63 target genes for novel miRNAs were predicted using computational analysis, and their functions were annotated. Deep sequencing provides an opportunity to identify pathogen-regulated miRNAs in trees, which will help in understanding the regulatory mechanisms of plant defense responses during pathogen infection.