Large-Scale Comparative Analyses of Tick Genomes Elucidate Their Genetic Diversity and Vector Capacities.

Among arthropod vectors, ticks transmit the most diverse human and animal pathogens, leading to an increasing number of new challenges worldwide. Here we sequenced and assembled high-quality genomes of six ixodid tick species and further resequenced 678 tick specimens to understand three key aspects of ticks: genetic diversity, population structure, and pathogen distribution. We explored the genetic basis common to ticks, including heme and hemoglobin digestion, iron metabolism, and reactive oxygen species, and unveiled for the first time that genetic structure and pathogen composition in different tick species are mainly shaped by ecological and geographic factors. We further identified species-specific determinants associated with different host ranges, life cycles, and distributions. The findings of this study are an invaluable resource for research and control of ticks and tick-borne diseases.

Environmental and occupational exposure to cadmium associated with male reproductive health risk: a systematic review and meta-analysis based on epidemiological evidence.

There is an abundance of epidemiological evidence and animal experiments concerning the correlation between cadmium exposure and adverse male reproductive health outcomes. However, the evidence remains inconclusive. We conducted a literature search from PubMed, Embase, and Web of Science over the past 3 decades. Pooled r and 95% confidence intervals (CIs) were derived from Cd levels of the type of biological materials and different outcome indicators to address the large heterogeneity of existing literature. Cd was negatively correlated with semen parameters (r = - 0.122, 95% CI - 0.151 to - 0.092) and positively correlated with sera sex hormones (r = 0.104, 95% CI 0.060 to 0.147). Among them, Cd in three different biological materials (blood, semen, and urine) was negatively correlated with semen parameters, while among sex hormones, only blood and urine were statistically positively correlated. In subgroup analysis, blood Cd was negatively correlated with semen density, sperm motility, sperm morphology, and sperm count. Semen Cd was negatively correlated with semen concentration. As for serum sex hormones, blood Cd had no statistical significance with three hormones, while semen Cd was negatively correlated with testosterone. In summary, cadmium exposure might be associated with the risk of a decline in sperm quality and abnormal levels of sex hormones.

Upregulation of TRPC6 Mediated by PAX6 Hypomethylation Is Involved in the Mechanical Allodynia Induced by Chemotherapeutics in Dorsal Root Ganglion.

BACKGROUND: Although the action mechanism of antineoplastic agents is different, oxaliplatin, paclitaxel, or bortezomib as first-line antineoplastic drugs can induce painful neuropathy. In rodents, mechanical allodynia is a common phenotype of painful neuropathy for 3 chemotherapeutics. However, whether there is a common molecular involved in the different chemotherapeutics-induced painful peripheral neuropathy remains unclear. METHODS: Mechanical allodynia was tested by von Frey hairs following i.p. injection of vehicle, oxaliplatin, paclitaxel, or bortezomib in Sprague-Dawley rats. Reduced representation bisulfite sequencing and methylated DNA immunoprecipitation were used to detect the change of DNA methylation. Western blot, quantitative polymerase chain reaction, chromatin immunoprecipitation, and immunohistochemistry were employed to explore the molecular mechanisms. RESULTS: In 3 chemotherapeutic models, oxaliplatin, paclitaxel, or bortezomib accordantly upregulated the expression of transient receptor potential cation channel, subfamily C6 (TRPC6) mRNA and protein without affecting the DNA methylation level of TRPC6 gene in DRG. Inhibition of TRPC6 by using TRPC6 siRNA (i.t., 10 consecutive days) relieved mechanical allodynia significantly following application of chemotherapeutics. Furthermore, the downregulated recruitment of DNA methyltransferase 3 beta (DNMT3b) at paired box protein 6 (PAX6) gene led to the hypomethylation of PAX6 gene and increased PAX6 expression. Finally, the increased PAX6 via binding to the TPRC6 promoter contributes to the TRPC6 increase and mechanical allodynia following chemotherapeutics treatment. CONCLUSIONS: The TRPC6 upregulation through DNMT3b-mediated PAX6 gene hypomethylation participated in mechanical allodynia following application of different chemotherapeutic drugs.

In Situ Raman Monitoring and Manipulating of Interfacial Hydrogen Spillover by Precise Fabrication of Au/TiO2 /Pt Sandwich Structures.

The spillover of hydrogen species and its role in tuning the activity and selectivity in catalytic hydrogenation have been investigated in situ using surface-enhanced Raman spectroscopy (SERS) with 10 nm spatial resolution through the precise fabrication of Au/TiO2 /Pt sandwich nanostructures. In situ SERS study reveals that hydrogen species can efficiently spillover at Pt-TiO2 -Au interfaces, and the ultimate spillover distance on TiO2 is about 50 nm. Combining kinetic isotope experiments and density functional theory calculations, it is found that the hydrogen spillover proceeds via the water-assisted cleavage and formation of surface hydrogen-oxygen bond. More importantly, the selectivity in the hydrogenation of the nitro or isocyanide group is manipulated by controlling the hydrogen spillover. This work provides molecular insights to deepen the understanding of hydrogen activation and boosts the design of active and selective catalysts for hydrogenation.

Escherichia coli and Pseudomonas aeruginosa lipopolysaccharide O-antigen ligases share similar membrane topology and biochemical properties.

WaaL is an inner membrane glycosyltransferase that catalyzes the transfer of O-antigen polysaccharide from its lipid-linked intermediate to a terminal sugar of the lipid A-core oligosaccharide, a conserved step in lipopolysaccharide biosynthesis. Ligation occurs at the periplasmic side of the bacterial cell membrane, suggesting the catalytic region of WaaL faces the periplasm. Establishing the membrane topology of the WaaL protein family will enable understanding its mechanism and exploit it as a potential antimicrobial target. Applying oxidative labeling of native methionine/cysteine residues, we previously validated a topological model for Escherichia coli WaaL, which differs substantially from the reported topology of the Pseudomonas aeruginosa WaaL, derived from the analysis of truncated protein reporter fusions. Here, we examined the topology of intact E. coli and P. aeruginosa WaaL proteins by labeling engineered cysteine residues with the membrane-impermeable sulfhydryl reagent polyethylene glycol maleimide (PEG-Mal). The accessibility of PEG-Mal to targeted engineered cysteine residues in both E. coli and P. aeruginosa WaaL proteins demonstrates that both ligases share similar membrane topology. Further, we also demonstrate that P. aeruginosa WaaL shares similar functional properties with E. coli WaaL and that E. coli WaaL may adopt a functional dimer conformation.

TNF-α/STAT3 pathway epigenetically upregulates Nav1.6 expression in DRG and contributes to neuropathic pain induced by L5-VRT.

BACKGROUND: Studies showed that upregulation of Nav1.6 increased the neuronal excitability and participated in neuropathic pain in the dorsal root ganglion (DRG). However, the molecular mechanisms underlying Nav1.6 upregulation were not reported yet. METHODS: The paw withdrawal threshold was measured in the rodents following lumbar 5 ventral root transection (L5-VRT). Then qPCR, western blotting, immunoprecipitation, immunohistochemistry, and chromatin immunoprecipitation assays were performed to explore the molecular mechanisms in vivo and in vitro. RESULTS: We found that the levels of Nav1.6 and phosphorylated STAT3 were significantly increased in DRG neurons following L5-VRT, and TNF-α incubation also upregulated the Nav1.6 expression in cultured DRG neurons. Furthermore, immunoprecipitation and chromatin immunoprecipitation assays demonstrated that L5-VRT increased the binding of STAT3 to the Scn8a (encoding Nav1.6) promoter and the interaction between STAT3 and p300, which contributed to the enhanced transcription of Scn8a by increasing histone H4 acetylation in Scn8a promoter in DRG. Importantly, intraperitoneal injection of the TNF-α inhibitor thalidomide reduced the phosphorylation of STAT3 and decreased the recruitment of STAT3 and histone H4 hyperacetylation in the Scn8a promoter, thus subsequently attenuating Nav1.6 upregulation in DRG neurons and mechanical allodynia induced by L5-VRT. CONCLUSION: These results suggested a new mechanism for Nav1.6 upregulation involving TNF-α/STAT3 pathway activation and subsequent STAT3-mediated histone H4 hyperacetylation in the Scn8a promoter region in DRG, which contributed to L5-VRT-induced neuropathic pain.

Lifetime regular exercise affects the incident of different arrhythmias and improves organismal health in aging female Drosophila melanogaster.

We used Drosophila melanogaster as an animal model system to study the impact of exercise training initiated early in life on cardiac function using a well-established model of inherent myogenic properties of the heart and discussed the changes on myosin, a myocardial contractile protein. We also explored the effect of early physical exercise on organismal aging by analyzing the wake-sleep pattern using a Drosophila activity monitor system. We found that a variety of arrhythmias are part of the heart spectrum in old flies after a lifetime of physical exercise as evidenced by reducing the incidence of fibrillations and increasing the occurrence of bradycardias. Maintenance of myocardial myosin levels may be an underlying contributor to these exercise-induced improvements in cardiac function at an advanced age. Moreover, we found that exercise training resulted in improved sleep quality by ameliorating age-related sleep inefficiency, fragmentation and sleep consolidation.

Deep Boosting Learning: A Brand-New Cooperative Approach for Image-Text Matching.

Image-text matching remains a challenging task due to heterogeneous semantic diversity across modalities and insufficient distance separability within triplets. Different from previous approaches focusing on enhancing multi-modal representations or exploiting cross-modal correspondence for more accurate retrieval, in this paper we aim to leverage the knowledge transfer between peer branches in a boosting manner to seek a more powerful matching model. Specifically, we propose a brand-new Deep Boosting Learning (DBL) algorithm, where an anchor branch is first trained to provide insights into the data properties, with a target branch gaining more advanced knowledge to develop optimal features and distance metrics. Concretely, an anchor branch initially learns the absolute or relative distance between positive and negative pairs, providing a foundational understanding of the particular network and data distribution. Building upon this knowledge, a target branch is concurrently tasked with more adaptive margin constraints to further enlarge the relative distance between matched and unmatched samples. Extensive experiments validate that our DBL can achieve impressive and consistent improvements based on various recent state-of-the-art models in the image-text matching field, and outperform related popular cooperative strategies, e.g., Conventional Distillation, Mutual Learning, and Contrastive Learning. Beyond the above, we confirm that DBL can be seamlessly integrated into their training scenarios and achieve superior performance under the same computational costs, demonstrating the flexibility and broad applicability of our proposed method.

Experiences and prospects for national survey of terrestrial wildlife resources in China.

Wildlife resources are strategic resources of a country, and the investigation of which is a key task for effective management in protection and utilization. Since the 1990s, two national surveys of terrestrial wildlife resources have been carried out in China, and the situation of wildlife resources has been known to a certain extent. Due to the complexity and difficulty of national wildlife survey, we are still not able to grasp the background and dynamics of wildlife resources as a whole promptly and effectively. The results and effectiveness of wildlife resources investigation will directly affect the decision-making related in wildlife protection. According to Law of the People's Republic of China on the Protection of Wildlife and Regulations of the People's Republic of China for the Implementation of the Protection of Terrestrial Wildlife, it is imperative to carry out the third national survey of terrestrial wildlife resources, and to be integrated with the national strategy of ecological civilization construction. The aims of this review were to summarize the earlier experiences in time, to further improve the investigation scheme and technical methods, to serve the third national survey of terrestrial wildlife resources, in addition to obtain more comprehensive and reliable data of wildlife resources, grasp the development trend of domestic wildlife resources, and provide more effective supports for the wildlife conservation in China.

Comparison of the impact of team-based learning and lecture-based learning on nursing students' core competencies: A systematic review and meta-analysis.

AIM: This study aims to evaluate the effect of team-based learning on the core competence of nursing students compared with traditional teaching methods. BACKGROUND: In recent years, team-based learning has been widely used as a learning and teaching method in the world. Not only the necessary knowledge, skills and attitudes, but also the core competence is necessary to cope with various clinical situations for nursing students. However, the effect of this new teaching method on core competence of nursing students is not consistent. DESIGN: The study was designed according to the preferred reporting entries guidelines statement for systematic reviews and meta-analyses and population, intervention, comparison, outcome and study. METHODS: Data were collected from PubMed, Embase, Web of Science, ScienceDirect and Scopus. The quality of studies was assessed using "The Newcastle Ottawa scale". A random-effect model of meta-analyses was conducted to generate pooled standardized mean differences (SMD) for core competence using Rev Man 5.4.1 software and STATASE 15. Moreover, subgroup, heterogeneity, sensitivity and publication bias analyses were conducted. RESULTS: A total of 14 articles with 1942 participants were included in the meta-analysis. Compared with the traditional pedagogy among nursing students, team-based learning pedagogy significantly increased theoretical performance, professional effects (self-directed learning ability and communication ability) but did not affect practice skills. In addition, one study found that learning attitudes were not improved in students with high or low academic performance. This might mean that the teaching model should be implemented for a long time, which essentially changed students' learning attitudes to improve students' self-directed learning ability and core competence, especially for students with low scores. CONCLUSIONS: In summary, findings indicated that team-based learning pedagogical approaches might be beneficial to improve teaching quality in nursing education. However, practice skills might not be sensitive to team-based learning because of the seriation of the original course. Nursing educators need to explore teaching strategies to cultivate high-quality nursing talents to cultivate nursing students with core competence and ensure that they are successfully qualified for new employment.

Cotton plasma membrane intrinsic protein 2s (PIP2s) selectively interact to regulate their water channel activities and are required for fibre development.

Aquaporins are thought to be associated with water transport and play important roles in cotton (Gossypium hirsutum) fibre elongation. Among aquaporins, plasma membrane intrinsic proteins (PIPs) constitute a plasma-membrane-specific subfamily and are further subdivided into PIP1 and PIP2 groups. In this study, four fibre-preferential GhPIP2 genes were functionally characterized. The selective interactions among GhPIP2s and their interaction proteins were studied in detail to elucidate the molecular mechanism of cotton fibre development. GhPIP2;3 interacted with GhPIP2;4 and GhPIP2;6, but GhPIP2;6 did not interact with GhPIP2;4. Coexpression of GhPIP2;3/2;4 or GhPIP2;3/2;6 resulted in a positive cooperative effect which increased the permeability coefficient of oocytes, while GhPIP2;4/2;6 did not. GhBCP2 (a blue copper-binding protein) inhibited GhPIP2;6 water channel activity through their interaction. Overexpression of GhPIP2 genes in yeast induced longitudinal growth of the host cells. By contrast, knockdown of expression of GhPIP2 genes in cotton by RNA interference markedly hindered fibre elongation. In conclusion, GhPIP2 proteins are the primary aquaporin isoforms in fibres. They selectively form hetero-oligomers in order to regulate their activities to meet the requirements for rapid fibre elongation.

[Survey on characteristics of menopause of Chinese women with the age of 40-60 years at gynecological clinic from 14 hospitals].

OBJECTIVE: To investigate the characteristics of menopause of Chinese women with the age of 40-60 years concerning gynecologic clinics in China. METHODS: From Mar.2008 to Sept.2008, a face-to-face questionnaire was conducted in gynecological clinic in perimenopausal and postmenopausal women in 14 hospitals in China, which included general demographic data, menstrual change process, climacteric symptoms and knowledge about menopause. Modified Kupperman index were used to evaluate climacteric symptoms during the recent week and awareness of hormonal replacement therapy were studied. RESULTS: A total of 1641 women were investigated. The ages of onset of menopause transition, climacteric symptoms and natural menopause were (47 ± 4), (46 ± 4), (49 ± 3) years old respectively. Climacteric symptoms could be found in 78.43% (1287/1641) women during menopausal transition, which were mainly mild to moderate symptoms. The top 5 symptoms were fatigue and weakness (71.48%, 1173/1641), irritability (68.68%, 1127/1641), insomnia (67.65%, 1110/1641), muscle and joint pain (64.11%, 1052/1641) and hot flush (57.90%, 950/1641). The climacteric symptoms were not constant during menopausal transition, usually more severe in late transition and postmenopausal periods, during which the moderate and severe symptoms were 59.1% (189/320) and 51.1% (291/570) respectively. Although most symptoms primarily appeared along with menstruation change, there are about 17.5% (172/981) patients experienced climacteric symptoms before menstruation change occurrence. There were 56.39% (733/1300) women had ever heard (mostly from gynecologist) about hormone replacement therapy from Obstetrician and Gynecologist. CONCLUSIONS: Most of the women during menopausal transition had climacteric symptoms, usually mild and moderate ones. Although most symptoms primarily appeared along with menstruation change, there are other patients' experienced climacteric symptoms before menstruation change occurrence.

Plug-and-Play Regulators for Image-Text Matching.

Exploiting fine-grained correspondence and visual-semantic alignments has shown great potential in image-text matching. Generally, recent approaches first employ a cross-modal attention unit to capture latent region-word interactions, and then integrate all the alignments to obtain the final similarity. However, most of them adopt one-time forward association or aggregation strategies with complex architectures or additional information, while ignoring the regulation ability of network feedback. In this paper, we develop two simple but quite effective regulators which efficiently encode the message output to automatically contextualize and aggregate cross-modal representations. Specifically, we propose (i) a Recurrent Correspondence Regulator (RCR) which facilitates the cross-modal attention unit progressively with adaptive attention factors to capture more flexible correspondence, and (ii) a Recurrent Aggregation Regulator (RAR) which adjusts the aggregation weights repeatedly to increasingly emphasize important alignments and dilute unimportant ones. Besides, it is interesting that RCR and RAR are "plug-and-play": both of them can be incorporated into many frameworks based on cross-modal interaction to obtain significant benefits, and their cooperation achieves further improvements. Extensive experiments on MSCOCO and Flickr30K datasets validate that they can bring an impressive and consistent R@1 gain on multiple models, confirming the general effectiveness and generalization ability of the proposed methods.

High-Performance Transformer Tracking.

Correlation has a critical role in the tracking field, especially in recent popular Siamese-based trackers. The correlation operation is a simple fusion method that considers the similarity between the template and the search region. However, the correlation operation is a local linear matching process, losing semantic information and easily falling into a local optimum, which may be the bottleneck in designing high-accuracy tracking algorithms. In this work, to determine whether a better feature fusion method exists than correlation, a novel attention-based feature fusion network, inspired by the transformer, is presented. This network effectively combines the template and search region features using attention mechanism. Specifically, the proposed method includes an ego-context augment module based on self-attention and a cross-feature augment module based on cross-attention. First, we present a transformer tracking (named TransT) method based on the Siamese-like feature extraction backbone, the designed attention-based fusion mechanism, and the classification and regression heads. Based on the TransT baseline, we also design a segmentation branch to generate the accurate mask. Finally, we propose a stronger version of TransT by extending it with a multi-template scheme and an IoU prediction head, named TransT-M. Experiments show that our TransT and TransT-M methods achieve promising results on seven popular benchmarks. Code and models are available at https://github.com/chenxin-dlut/TransT-M.

HMGB2 upregulation promotes the progression of hepatocellular carcinoma cells through the activation of ZEB1/vimentin axis.

Background: High mobility group box 2 (HMGB2) is abnormally expressed in human cancers and participated in multiple biological behaviors, such as proliferation, invasion and prognosis. However, its role in hepatocellular carcinoma (HCC) is largely unknown. Methods: In clinical sample analysis, 62 HCC patients were enrolled in this study. The expression of HMGB2 was analyzed by quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemical method, clinical prognosis data were analyzed by Kaplan-Meier analysis. In cellular and molecular biology experiments, HMGB2 expression was analyzed in HCC cells. HMGB2 knockdown model was constructed by small interfering RNA (siRNA). Cell counting kit-8 (CCK-8) and cell migration & invasion assay were used to evaluate cell proliferative potential and motility. Recombinant human vimentin protein was used to partially restore the expression and function of vimentin. Western blot and immunochemical staining were performed to detect HMGB2 protein, zinc finger E-box binding homeobox 1 (ZEB1) and vimentin. Flow cytometry analyses were performed to determine the alteration of cell cycle in different groups. Results: HMGB2 was abnormally overexpressed in HCC. HMGB2 knockdown reduced malignant behaviors especially the proliferative potential and motility of HCC cells. The inhibition of HCC cells proliferation and mobility could be partially restored via treatment with recombinant vimentin protein. Our findings confirmed abnormal activation of HMGB2-ZEB1 vimentin axis facilitates HCC malignant proliferation and motility. The elevated HMGB2 expression in clinical samples was related to postoperative survival time of HCC patients. It indicated HMGB2 promotes the proliferation and motility potential of HCC via HMGB2-ZEB1-vimentin axis activation. Conclusions: HMGB2 is up-regulated in HCC and affects the malignant transformation by modulating HMGB2-ZEB1-vimentin signaling pathway, which may provide a research basis for evaluating the disease progression and developing clinical treatment strategies of HCC.

Effect of physical exercise on sleep quality in college students: Mediating role of smartphone use.

OBJECTIVE: To investigate the effect of physical exercise on sleep quality and the mediating effect of smartphone use behavior in college students. METHODS: A cross-sectional study design was adopted. An online survey of 5,075 college students was conducted using the Physical Activity Rating Scale-3, the Pittsburgh Sleep Quality Index, and the Mobile Phone Addiction Tendency Scale. RESULTS: The sleep quality of college students was poor, and the proportion of college students with good sleep quality was 23.567%. A significant correlation existed between sleep quality and physical exercise (r = -0.159, P < 0.001) and mobile phone addiction (r = 0.355, P < 0.001). Physical exercise can predict sleep quality in college students (ß = -0.011, P < 0.001). Smartphone use plays a part in mediating the process by which physical exercise affects sleep quality. CONCLUSION: Chinese college students have poor sleep quality. Physical exercise and smartphone use behavior are important factors affecting the sleep quality of college students. Physical exercise can directly predict the sleep quality of college students and can predict the sleep quality of college students through the mediating effect of smartphone use behavior.

Acquired Hemophilia A: A Retrospective Multicenter Analysis of 42 Patients.

INTRODUCTION: Immunosuppressive therapy (IST) for acquired hemophilia A (AHA) results in remission within days to months in 60% to 80% of patients. However, little is known regarding the predictors of response. AIM: This study aimed to identify the factors that influence response to treatment. METHODS: The data of 42 patients with AHA from three hospitals were retrospectively analyzed. RESULTS: All 42 AHA patients received IST; complete treatment data were available for 34 patients. The response rate was 60% among the 5/34 (14.7%) patients who received steroids alone, 70.8% among the 24/34 (70.6%) patients who received steroids plus cyclophosphamide, and 80% among the 5/34 (14.7%) patients who received steroids plus cyclophosphamide and rituximab. Overall, 29/34 (85.3%) patients achieved CR; 4/34 (13.8%) of them relapsed after a median time of 410 (21-1279) days. Adverse events occurred in 14/34 (41.2%) patients: 13/34 (38.2%) had infections and 1/34 (2.9%) developed pancytopenia. In univariate and multivariate Cox regression analyses, FVIII inhibitor titer ≥20 BU/mL was the only significant prognostic factor affecting time to CR. No variable had significant effect on OS. CONCLUSION: FVIII inhibitory antibody titer ≥20 BU/mL appears to be an important predictor of time to complete response in patients with acquired hemophilia A treated with immunosuppressive therapy.

Unsupervised Domain Adaptation Using Fourier Phase Enhanced Training Images for Liver Tumors Detection in Multi-phase CT Images.

Computer-aided diagnostic methods, such as automatic and precise liver tumor detection, have a significant impact on healthcare. In recent years, deep learning-based liver tumor detection methods in multi-phase computed tomography (CT) images have achieved noticeable performance. Deep learning frameworks require a substantial amount of annotated training data but obtaining enough training data with high quality annotations is a major issue in medical imaging. Additionally, deep learning frameworks experience domain shift problems when they are trained using one dataset (source domain) and applied to new test data (target domain). To address the lack of training data and domain shift issues in multiphase CT images, here, we present an adversarial learning-based strategy to mitigate the domain gap across different phases of multiphase CT scans. We introduce to use Fourier phase component of CT images in order to improve the semantic information and more reliably identify the tumor tissues. Our approach eliminates the requirement for distinct annotations for each phase of CT scans. The experiment results show that our proposed method performs noticeably better than conventional training and other methods.

Metavirome of 31 tick species provides a compendium of 1,801 RNA virus genomes.

The increasing prevalence and expanding distribution of tick-borne viruses globally have raised health concerns, but the full repertoire of the tick virome has not been assessed. We sequenced the meta-transcriptomes of 31 different tick species in the Ixodidae and Argasidae families from across mainland China, and identified 724 RNA viruses with distinctive virome compositions among genera. A total of 1,801 assembled and complete or nearly complete viral genomes revealed an extensive diversity of genome architectures of tick-associated viruses, highlighting ticks as a reservoir of RNA viruses. We examined the phylogenies of different virus families to investigate virome evolution and found that the most diverse tick-associated viruses are positive-strand RNA virus families that demonstrate more ancient divergence than other arboviruses. Tick-specific viruses are often associated with only a few tick species, whereas virus clades that can infect vertebrates are found in a wider range of tick species. We hypothesize that tick viruses can exhibit both 'specialist' and 'generalist' evolutionary trends. We hope that our virome dataset will enable much-needed research on vertebrate-pathogenic tick-associated viruses.

The WaaL O-antigen lipopolysaccharide ligase has features in common with metal ion-independent inverting glycosyltransferases.

WaaL is a membrane enzyme that catalyzes a key step in lipopolysaccharide (LPS) synthesis: the glycosidic bonding of a sugar at the proximal end of the undecaprenyl-diphosphate (Und-PP) O-antigen with a terminal sugar of the lipid A-core oligosaccharide (OS). Utilizing an in vitro assay, we demonstrate here that ligation with purified Escherichia coli WaaL occurs without adenosine-5'-triphosphate (ATP) and magnesium ions. Furthermore, E. coli and Pseudomonas aeruginosa WaaL proteins cannot catalyze ATP hydrolysis in vitro. We also show that a lysine substitution of the arginine (Arg)-215 residue renders an active protein, whereas WaaL mutants with alanine replacements in the periplasmic-exposed residues Arg-215, Arg-288 and histidine (His)-338 and also the membrane-embedded aspartic acid-389 are nonfunctional. An in silico approach, combining predicted topological information with the analysis of sequence conservation, confirms the importance of a positive charge at the small periplasmic loop of WaaL, since an Arg corresponding to Arg-215 was found at a similar position in all the WaaL homologs. Also, a universally conserved H[NSQ]X(9)GXX[GTY] motif spanning the C-terminal end of the predicted large periplasmic loop and the membrane boundary of the transmembrane helix was identified. The His residue in this motif corresponds to His-338. A survey of LPS structures in which the linkage between O-antigen and lipid A-core OS was elucidated reveals that it is always in the ß-configuration, whereas the sugars bound to Und-PP are in the α-configuration. Together, our biochemical and in silico data argue that WaaL proteins use a common reaction mechanism and share features of metal ion-independent inverting glycosyltransferases.