Search

Background Envelope stress responses (ESRs) are critical for adaptive resistance of Gram-negative bacteria to envelope-targeting antimicrobial agents. However, ESRs are poorly defined in a large number of well-known plant and human pathogens. Dickeya oryzae can withstand a high level of self-produced envelope-targeting antimicrobial agents zeamines through a zeamine-stimulated RND efflux pump DesABC. Here, we unraveled the mechanism of D. oryzae response to zeamines and determined the distribution and function of this novel ESR in a variety of important plant and human pathogens. Results In this study, we documented that a two-component system regulator DzrR of D. oryzae EC1 mediates ESR in the presence of envelope-targeting antimicrobial agents. DzrR was found modulating bacterial response and resistance to zeamines through inducing the expression of RND efflux pump DesABC, which is likely independent on DzrR phosphorylation. In addition, DzrR could also mediate bacterial responses to structurally divergent envelope-targeting antimicrobial agents, including chlorhexidine and chlorpromazine. Significantly, the DzrR-mediated response was independent on the five canonical ESRs. We further presented evidence that the DzrR-mediated response is conserved in the bacterial species of Dickeya, Ralstonia, and Burkholderia, showing that a distantly located DzrR homolog is the previously undetermined regulator of RND-8 efflux pump for chlorhexidine resistance in B. cenocepacia. Conclusions Taken together, the findings from this study depict a new widely distributed Gram-negative ESR mechanism and present a valid target and useful clues to combat antimicrobial resistance.

This study focuses on configuration and dimension optimization of cutter disassembly mechanism. Firstly, a cutter disassembly mechanism configuration is proposed with four components and simple actions, based on the theory of inventive problem solving (TRIZ) contradiction solutions. Furthermore, a comprehensive dimension optimization strategy was developed, including non-dimensional normalization model, kinematic performance atlases and fuzzy comprehensive evaluation method. Then, the optimal relative dimension of crucial parameters was obtained. Combined with the assembly relationship between components, dimension of all parameters was designed for cutter disassembly mechanism. The locking and disassembling process simulation was provided to illustrate the feasibility of the mechanism. The results show that the angular velocity is very smooth and the locking and disassembling actions are realizable without interference for optimized cutter disassembly mechanism. The effectiveness of the configuration and dimension optimization method is validated.

Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is the primary vector of Candidatus Liberibacter asiaticus (Las), which causes the devastating disease Huanglongbing (HLB) in Asian citrus. To examine the effects of pathogens on the diversity and structure of insect-associated bacterial communities, we carried out a molecular analysis using healthy D.citri and Las-infected D.citri as a vector-pathogen model. 16S rRNA Illumina sequencing analysis of D.citri revealed shifts in its microbial diversity in response to pathogen infection. The phylum Proteobacteria predominated in D.citri representing 89.40 and 91.73% of the bacterial communities, while remaining bacterial sequences were mainly assigned to the phyla Actinobacteria, Firmicutes, Bacteroidetes and Acidobacteria. The relative proportions of different groups of bacteria changed significantly after pathogen infection. The relative abundance of bacterial communities between healthy D.citri and Las-infected D.citri were different, and the relative abundance of most dominant bacteria decreased, such as Oscillospira, Lactobacillus and Rubrobacter. However, the relative abundance of Wolbachia increased from 1.81 to 2.14%, and there was no difference in the abundance of Carsonella. In pairwise comparisons, the clone library from healthy D.citri contained greater 16S rRNA gene diversity, as reflected by the higher Shannon index at 2.937 versus 2.756 for the healthy and Las-infected clone libraries, respectively. These data indicated that Las infection has a profound effect on the structure and composition of the bacterial community associated with D.citri.

Tai Chi has been shown to have significant benefits in improving muscle strength, balance, and quality of life. The purpose of this study was to design a sitting or lying Tai Chi model with a better playing posture that is easier to play, and with greater exercise efficiency for stroke patients. Eighteen stroke patients were recruited (> 6 months post-stroke; modified Rankin Scale: 2–4). The Direction-Oriented Motion and Short-Sitting and Lying Tai Chi (DOM-SSLTC) model was composed of nine typical Yang-style Tai Chi forms. All the subjects received 12 practice sessions (90 min per session) led by a Tai Chi master, and performed the DOM-SSLTC for 60 min per day for 3 months at home. The characteristics of the exercise patterns were quantified using a Tai Chi master’s motions. National Institutes of Health Stroke Scale, Modified Ashworth Scale, Modified Rankin Scale, Barthel Index, muscle endurance, and psychological evaluations were used to evaluate the effect of the Tai Chi exercise program on the stroke patients. The results showed that the rectus femoris and sternocleidomastoid muscles had larger contractions and also had larger trunk flexion in the deep breath with one leg stretched Tai Chi pattern. The 18 stroke patients had significantly decreased Depression Questionnaire scores and improvements in muscle power of knee stretching and sitting up after training. This newly developed Tai Chi model with one leg stretched allowed the stroke patients to practice with more intensive exercise, and resulted in improvements in muscle power and depression scale after 3 months exercise.

The purpose of our study was to investigate an underlying mechanism that hydrogen peroxide-induced mitophagy contributed to laryngeal cancer cells survivals under oxidative stress condition. Tumor tissue and serum samples were collected from patients with laryngeal cancer. The Hep2 cell, a human laryngeal carcinoma cell, was used in in vitro experiments. The levels of lipid peroxidation were analyzed by ELISA. Knockdown of FUNDC1 was performed by RNAi. The changes of target proteins were determined by qRT-PCR and western blot. The cells were analyzed for changes in proliferation using cell counting kit-8 and mitophagy by the mitochondrial membrane potential assay and transmission electron microscopy. FUNDC1 in laryngeal cancer tissues were relative to the levels of lipid peroxidation in laryngeal cancer patients, which suggested that FUNDC1 was associated with the status of oxidative stress in the laryngeal cancer patients. Hydrogen peroxide significantly induced the elevation of FUNDC1, a mitophagic factor, in a time- and dose-dependent manner in laryngeal cancer cells, which was dependent on ERK signal activation. Knockdown of FUNDC1 by the siRNA attenuated the survival of laryngeal cancer cells under hydrogen peroxide stimulation. Moreover, the elevated FUNDC1 was required for the occurrence of mitophagy under hydrogen peroxide stimulation, which was identified by transmission electron microscopy, the alterations of mitochondrial permeability transition and the specific mitochondrial protein, hsp60. Inhibition of mitophagy with cyclosporine A could also effectively attenuate the laryngeal cancer cells survival under hydrogen peroxide stimulation. Hydrogen peroxide upregulated the expression of FUNDC1 through the activation of ERK1/2 signal to trigger a mitophagic response, giving laryngeal cancer cells a befit for survival. These findings suggested that FUNDC1 might be a potential target for the treatment of laryngeal cancer accompanied with high lipid peroxidation status.

Geological adaptability matching design of a disc cutter is the prerequisite of cutter head design for tunnel boring machines (TBMs) and plays an important role in improving the tunneling efficiency of TBMs. The main purpose of the cutter matching design is to evaluate the cutter performance and select the appropriate cutter size. In this paper, a novel evaluation method based on multicriteria decision making (MCDM) techniques was developed to help TBM designers in the process of determining the cutter size. The analytic hierarchy process (AHP) and matter element analysis were applied to obtaining the weights of the cutter evaluation criteria, and the fuzzy comprehensive evaluation and technique for order performance by similarity to ideal solution (TOPSIS) approaches were employed to determine the ranking of the cutters. A case application was offered to illustrate and validate the proposed method. The results of the project case demonstrate that this method is reasonable and feasible for disc cutter size selection in cutter head design.

Hosted by volcaniclastics of the Carboniferous Dahalajunshan Formation, the Songhu iron deposit is located in the central segment of the Awulale metallogenic belt, Chinese Western Tianshan. Mineralization and alteration are structurally controlled by orogen-parallel NWW-striking faults. Integrating with mineralogical and stable isotopic analyses based on paragenetic relationships, two types of iron mineralization have been identified. The deuteric mineralization (Type I) represented by brecciated, banded, and disseminated-vein ores juxtaposed with potassic–calcic alteration in the inner zone, which was formed from a magmatic fluid generated during the late stages of regional volcanism. In contrast, the volcanic-hydrothermal mineralization (Type II) is characterized by hydrothermal features occurring in massive and agglomerated ores with abundant sulfides, and was generated from the magmatic fluid with seawater contamination. Two volcaniclastic samples from the hanging and footwall of the main orebody yield zircon U–Pb ages of 327.8 ± 3.1 and 332.0 ± 2.0 Ma, respectively, which indicate Middle Carboniferous volcanism. Timing for iron mineralization can be broadly placed in the same epoch. By reviewing geological, mineralogical, and geochemical features of the primary iron deposits in the Awulale metallogenic belt, we propose that the two types of iron mineralization in the Songhu iron deposit are representative regionally. A summary of available geochronological data reveals Middle–Late Carboniferous polycyclic ore-related volcanism, and nearly contemporaneous iron mineralization along the belt. Furthermore, petro-geochemistry of volcanic–volcaniclastic host rocks indicates that partial melting of a metasomatized mantle wedge under a continental arc setting could have triggered the continuous volcanic activities and associated metallogenesis.

Zeamines are family of potent antibiotics and virulence determinants produced by the rice foot rot bacterial pathogen Dickeya zeae. So zeamines are important for the pathogenesis of D. zeae and development of new strategies against this devastating disease. In this study, we show that production of zeamines is positively modulated by ZmsO, which is a conserved Sfp-type phosphopantetheinyl thransferase (PPTase) associated with post-translational activation of fatty acid synthases and polyketide synthases. Deletion of zmsO significantly abolished zeamines production and attenuated the virulence of D. zeae without affect the growth rate. The zmsO gene is located at the upstream of zmsA and zmsK in the same gene cluster. Consistent with its role in post-translational modification, deletion of zmsO did not affect the transcriptional expression of zmsA and zmsK. In trans expression of the pcpS gene from Pseudomonas aeruginosa, which encodes a Sfp-type PPTase, in the zmsO deletion mutant could also fully restore the zeamines production and bacterial virulence, establishing the important role of Sfp-type PPTase in the zeamines biosynthesis and pathogenicity of D. zeae.

Background Dickeya zeae is the causal agent of maize and rice foot rot diseases, but recently it was also found to infect banana and cause severe losses in China. Strains from different sources showed significant diversity in nature, implying complicated evolution history and pathogenic mechanisms. Results D. zeae strains were isolated from soft rot banana plants and ornamental monocotyledonous Clivia miniata. Compared with D. zeae strain EC1 isolated from rice, clivia isolates did not show any antimicrobial activity, produced less extracellular enzymes, had a much narrow host ranges, but released higher amount of extracellular polysaccharides (EPS). In contrast, the banana isolates in general produced more extracellular enzymes and EPS than strain EC1. Furthermore, we provided evidence that the banana D. zeae isolate MS2 produces a new antibiotic/phytotoxin(s), which differs from the zeamine toxins produced by rice pathogen D. zeae strain EC1 genetically and in its antimicrobial potency. Conclusions The findings from this study expanded the natural host range of D. zeae and highlighted the genetic and phenotypic divergence of D. zeae strains. Conclusions can be drawn from a series of tests that at least two types of D. zeae strains could cause the soft rot disease of banana, with one producing antimicrobial compound while the other producing none, and the D. zeae clivia strains could only infect monocot hosts. D. zeae strains isolated from different sources have diverse virulence characteristics. Electronic supplementary material The online version of this article (10.1186/s12866-018-1300-y) contains supplementary material, which is available to authorized users.

To develop a new strategy that controls vascular pathogen infections in economic crops, we examined a possible enhancer of the vascular activity of XYLOGEN PROTEIN 1 promoter (Px). This protein is specifically expressed in the vascular tissues of Arabidopsis thaliana and plays an important role in xylem development. Although Px is predicted as vascular-specific, its activity is hard to detect and highly susceptible to plant and environmental conditions. The cauliflower mosaic virus 35S promoter (35S) is highly active in directing transgene expression. To test if 35S could enhance Px activity, while vascular specificity of the promoter is retained, we examined the expression of the uidA reporter gene, which encodes β-glucuronidase (GUS), under the control of a chimeric promoter (35S-Px) or Px by generating 35S-Px-GUS and Px-GUS constructs, which were transformed into tobacco seedlings. Both 35S-Px and Px regulated gene expression in vascular tissues. However, GUS expression driven by 35S-Px was not detected in 30- and 60-day-old plants. Quantitative real-time PCR analysis showed that GUS gene expression regulated by 35S-Px was 6.2–14.9-fold higher in vascular tissues than in leaves. Histochemical GUS staining demonstrated that 35S-Px was strongly active in the xylem and phloem. Thus, fusion of 35S and Px might considerably enhance the strength of Px and increase its vascular specificity. In addition to confirming that 35S enhances the activity of a low-level tissue-specific promoter, these findings provide information for further improving the activity of such promoters, which might be useful for engineering new types of resistant genes against vascular infections. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s13205-018-1379-8) contains supplementary material, which is available to authorized users.

RNAs are well-suited to act as cellular sensors that detect and respond to metabolite changes in the environment, due to their ability to fold into complex structures. Here, we introduce a genome-wide strategy called PARCEL that experimentally identifies RNA aptamers in vitro, in a high-throughput manner. By applying PARCEL to a collection of prokaryotic and eukaryotic organisms, we have revealed 58 new RNA aptamers to three key metabolites, greatly expanding the list of natural RNA aptamers. The newly identified RNA aptamers exhibit significant sequence conservation, are highly structured and show an unexpected prevalence in coding regions. We identified a prokaryotic precursor tmRNA that binds vitamin B2 (FMN) to facilitate its maturation, as well as eukaryotic mRNAs that bind and respond to FMN, suggesting FMN as the second RNA-binding ligand to affect eukaryotic expression. PARCEL results show that RNA-based sensing and gene regulation is more widespread than previously appreciated in different organisms., Riboswitches recognize and respond to specific metabolites by altering gene expression. Here, the authors developed a high-throughput method (PARCEL) to experimentally identify RNA aptamers across transcriptomes.

SOX2 is a high-mobility group box containing transcription factor essential for the maintenance of embryonic stem cells. Recent evidence indicates that SOX2 overexpression correlates with metastasis and poor prognosis in patients with laryngeal squamous cell cancer. To investigate how SOX2 contributes to this aggressive phenotype, we introduced the human SOX2 gene into a low SOX2-expressing human laryngeal cancer cell line Hep-2. Cell migration and invasion were determined by the Transwell assay with or without Matrigel coating. The epithelial-mesenchymal transition (EMT)-related markers were assayed by Western blot analysis or immunofluorescence. Our results showed that exogenous expression of SOX2 in Hep-2 cells substantially promoted their migratory and invasive capabilities in culture. Moreover, Hep-2 cells stably overexpressing SOX2 underwent EMT phenotype, as evidenced by mesenchymal morphology, decreased expression of epithelial marker (E-cadherin), and increased expression of mesenchymal markers (N-cadherin, vimentin, fibronectin, and α-smooth muscle actin). Strikingly, Western blot analysis and immunofluorescence also showed that overexpression of SOX2 resulted in substantial increase and nuclear accumulation of β-catenin in Hep-2 cells. However, small interfering RNA targeting β-catenin significantly attenuated the reduced expression of E-cadherin and increased cell migration and invasion abilities in SOX2-overexpressing cells, suggesting that SOX2-induced EMT process, migration, and invasion are dependent on β-catenin activation. Taken together, our findings underscore a novel role for SOX2 in laryngeal cancer migration and invasion.

A rice protein homologous to eukaryotic translation elongation factor 1A (eEF-1A) was found to interact with the Pns6 of rice ragged stunt virus (RRSV), the type member of the genus Oryzavirus, family Reoviridae, in yeast two-hybrid screening. The interaction between the rice protein, designated OseEF-1A, and RRSV Pns6 was confirmed by bimolecular fluorescence complementation. Besides Pns6, OseEF-1A also interacted with the viroplasm matrix protein, Pns10, of RRSV. When expressed together, OseEF-1A co-localized with RRSV Pns10 in epidermal cells of Nicotiana benthamiana. Pns6 of southern rice black-streaked dwarf virus (SRBSDV), a newly reported member of the genus Fijivirus, family Reoviridae, was the only non-structural SRBSDV protein studied here that also interacted with OseEF-1A. Like Pns6 of rice black-streaked dwarf virus (RBSDV), SRBSDV Pns6 interacted with itself and co-localized with Pns9-1 in N. benthamiana. In the presence of Pns6, OseEF-1A co-localized with Pns9-1, the putative viroplasm matrix protein of SRBSDV.

Pseudomonas aeruginosa uses a hierarchical quorum sensing (QS) network consisting of las, pqs and rhl regulatory elements to coordinate the expression of bacterial virulence genes. However, clinical isolates frequently contain loss-of-function mutations in the central las system. This motivated us to search for a mechanism that may functionally substitute las. Here we report identification of a new QS signal, IQS. Disruption of IQS biosynthesis paralyzes the pqs and rhl QS systems and attenuates bacterial virulence. Production of IQS is tightly controlled by las under normal culture conditions but is also activated by phosphate limitation, a common stressor that bacteria encounter during infections. Thus, these results have established an integrated QS system that connects the central las system and phosphate-stress response mechanism to the downstream pqs and rhl regulatory systems. Our discovery highlights the complexity of QS signaling systems and extends the gamut of QS and stress-response mechanisms.

The type III secretion system (TTSS) of Pseudomonas aeruginosa is a key virulence determinant for infection of eukaryotic hosts. Based on the findings that spermidine-mediated host-pathogen signalling is important for activation of type III secretion systems (TTSS), in this study, we designed, synthesized and evaluated a series of polyamine derivatives for their potentials in inhibiting the expression TTSS in P. aeruginosa. In vitro assay of 15 compounds synthesized in this study unveiled stringent structural requirements for TTSS-inhibitory activity. Among them, R101SPM, a conjugate between rhodamine 101 and spermine, showed a potent activity in inhibition of the TTSS gene expression and in attenuation of the TTSS-mediated cytotoxicity on human cells. In vivo analysis demonstrated that R101SPM could rescue mice from the lethal infection by P. aeruginosa. Moreover, genetic analysis showed that the full TTSS-inhibitory activity of R101SPM required a functional spermidine transporter. Taken together, our results present a new class of lead molecules for developing anti-virulence drugs and demonstrate that the spermidine transporter SpuDEGHF of P. aeruginosa is a promising drug target.

Bacterial cells sense their population density through a sophisticated cell-cell communication system and trigger expression of particular genes when the density reaches a threshold. This type of gene regulation, which controls diverse biological functions including virulence, is known as quorum sensing. Quorum-sensing signals, such as acyl-homoserine lactones (AHLs), are the essential components of the communication system. AHLs regulate virulence gene expression in a range of plant and animal (including human) bacterial pathogens. AHL-producing tobacco restored the pathogenicity of an AHL-negative mutant of Erwinia carotovora. Different bacterial species may produce different AHLs, which vary in the length and substitution of the acyl chain but contain the same homoserine lactone moiety. Here we show that the acyl-homoserine lactonase (AHL-lactonase), a new enzyme from Bacillus sp., inactivates AHL activity by hydrolysing the lactone bond of AHLs. Plants expressing AHL-lactonase quenched pathogen quorum-sensing signalling and showed significantly enhanced resistance to E. carotovora infection. Our results highlight a promising potential to use quorum-sensing signals as molecular targets for disease control, thereby broadening current approaches for prevention of bacterial infections.

A caspase gene in Plutella xylostella (DBM) was identified firstly and named Px-caspase-1. It had a full-length of 1172 bp and contained 900 bp open reading frame that encoded 300 amino acids with 33.6 kDa. The deduced amino acid of Px-caspase-1 had two domain profile including caspase_p20 (position 61-184) and caspase_p10 (position 203-298) (i.e. the big and small catalytic domains), and the highly conserved pentapeptide QACQG in caspase_p20 domain (the recognized catalytic site of caspases). Being highly homologous to effector caspase genes in other insect and mammalian species, Px-caspase-1 was thought to be an effector caspase gene. Heat stress could result in significant mortality increase on adult DBM. Px-caspase-1 mRNA expression and caspase-3 enzyme activity (a effector caspase) were elevated with age and heat treatment. And, heat stress facilitated the procession of Px-caspase-1 expression. Significantly higher mRNA transcription levels were found in a chlorpyrifos-resistant DBM strain, as compared to those in insecticide-susceptible DBM. The results indicated that high temperature could significantly promote apoptosis process resulting in an the increased DBM mortality rate, and that insecticide-susceptible DBM had a significantly higher physiological fitness at high temperatures than insecticide-resistant DBM.

To improve transgene expression level, we synthesized a truncated insecticidal gene m-cry1Ac by increasing its GC content from 37.4 to 54.8%, based on the codon usage pattern of sugarcane genes, and transferred it into two sugarcane cultivars (ROC16 and YT79-177) by microprojectile bombardment. The integration sites and expression pattern of the transgene were determined, respectively, by Southern, northern and western blot analyses. The transgenic sugarcane lines produced up to 50 ng Cry1Ac protein per mg soluble proteins, which was about fivefold higher than that produced by the partially modified s-cry1Ac (GC% = 47.5%). In greenhouse plant assay, about 62% of the transgenic lines exhibited excellent resistance to heavy infestation by stem borers. In field trials, the m-cry1Ac transgenic sugarcane lines expressing high levels of Cry1Ac were immune from insect attack. In contrast, expression of s-cry1Ac in transgenic sugarcane plants resulted in moderately decreased damages in internodes (0.4-1.7%) and stalks (13.3-26.7%) in comparison with the untransformed sugarcane controls, which showed about 4 and 26-40% damaged internodes and stalks, respectively. Significantly, these transgenic sugarcane lines with high levels of insect resistance showed similar agronomic and industrial traits as untransformed control plants. Taken together, the findings from this study indicate a promising potential of engineering an insect-resistant gene to tailor its protein expression levels in transgenic sugarcane to combat insect infestations.