Identification, expression analysis, and functional verification of three opsin genes related to the phototactic behaviour of Ostrinia furnacalis.

Ostrinia furnacalis is a disreputable herbivorous pest that poses a serious threat to corn crops. Phototaxis in nocturnal moths plays a crucial role in pest prediction and control. Insect opsins are the main component of insect visual system. However, the inherent molecular relationship between phototactic behaviour and vision of insects remains a mystery. Herein, three opsin genes were identified and cloned from O. furnacalis (OfLW, OfBL, and OfUV). Bioinformatics analysis revealed that all opsin genes had visual pigment (opsin) retinal binding sites and seven transmembrane domains. Opsin genes were distributed across different developmental stages and tissues, with the highest expression in adults and compound eyes. The photoperiod-induced assay elucidated that the expression of three opsin genes in females were higher during daytime, while their expression in males tended to increase at night. Under the sustained darkness, the expression of opsin genes increased circularly, although the increasing amplitude in males was lower when compared with females. Furthermore, the expression of OfLW, OfBL, and OfUV was upregulated under green, blue, and ultraviolet light, respectively. The results of RNA interference showed that the knockout of opsin genes decreased the phototaxis efficiency of female and male moths to green, blue, and ultraviolet light. Our results reveal that opsin genes are involved in the phototactic behaviour of moths, providing a potential target gene for pest control and a basis for further investigation on the phototactic behaviour of Lepidoptera insects.

Clinical characterization and outcomes of impulse oscillometry-defined bronchodilator response: an ECOPD cohort-based study.

BACKGROUND: The clinical significance of the impulse oscillometry-defined small airway bronchodilator response (IOS-BDR) is not well-known. Accordingly, this study investigated the clinical characteristics of IOS-BDR and explored the association between lung function decline, acute respiratory exacerbations, and IOS-BDR. METHODS: Participants were recruited from an Early Chronic Obstructive Pulmonary Disease (ECOPD) cohort subset and were followed up for two years with visits at baseline, 12 months, and 24 months. Chronic obstructive pulmonary disease (COPD) was defined as a post-bronchodilator forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) ratio < 0.70. IOS-BDR was defined as meeting any one of the following criteria: an absolute change in respiratory system resistance at 5 Hz ≤ - 0.137 kPa/L/s, an absolute change in respiratory system reactance at 5 Hz ≥ 0.055 kPa/L/s, or an absolute change in reactance area ≤ - 0.390 kPa/L. The association between IOS-BDR and a decline in lung function was explored with linear mixed-effects model. The association between IOS-BDR and the risk of acute respiratory exacerbations at the two-year follow-up was analyzed with the logistic regression model. RESULTS: This study involved 466 participants (92 participants with IOS-BDR and 374 participants without IOS-BDR). Participants with IOS-BDR had higher COPD assessment test and modified Medical Research Council dyspnea scale scores, more severe emphysema, air trapping, and rapid decline in FVC than those without IOS-BDR over 2-year follow-up. IOS-BDR was not associated with the risk of acute respiratory exacerbations at the 2-year follow-up. CONCLUSIONS: The participants with IOS-BDR had more respiratory symptoms, radiographic structural changes, and had an increase in decline in lung function than those without IOS-BDR. TRIAL REGISTRATION: Chinese Clinical Trial Registry, ChiCTR1900024643. Registered on 19 July, 2019.

Integrated transcriptomic and proteomic analyses reveal the molecular mechanism underlying the thermotolerant response of Spodoptera frugiperda.

Spodoptera frugiperda (Lepidoptera: Noctuidae) is a highly destructive invasive pest with remarkable adaptability to extreme climatic conditions, posing a substantial global threat. Although the effects of temperature stress on the biological and ecological properties of S. frugiperda have been elucidated, the molecular mechanisms underlying its responses remain unclear. Herein, we combined transcriptomic and proteomic analyses to explore the key genes and proteins involved in thermotolerance regulation in S. frugiperda larvae at 42 °C. Overall, 1528 differentially expressed genes (DEGs) and 154 differentially expressed proteins (DEPs) were identified in S. frugiperda larvae under heat stress, including antioxidant enzymes, heat shock proteins (Hsps), cytochrome P450s, starch and sucrose metabolism genes, and insulin signaling pathway genes, indicating their involvement in heat tolerance regulation. Correlation analysis of DEGs and DEPs revealed that seven and eight had the same and opposite expression profiles, respectively. After nanocarrier-mediated RNA interference knockdown of SfHsp29, SfHsp20.4, SfCAT, and SfGST, the body weight and mortality of S. frugiperda larvae significantly decreased and increased under heat stress, respectively. This indicates that SfHsp29, SfHsp20.4, SfCAT, and SfGST play a crucial role in the thermotolerance of S. frugiperda larvae. These results provide insight into the mechanism of heat tolerance in S. frugiperda.

Glycosylation of Secondary Metabolites: A Multifunctional UDP-Glycosyltransferase, CsUGT74Y1, Promotes the Growth of Plants.

Camellia sinensis contains numerous glycosylated secondary metabolites that provide various benefits to plants and humans. However, the genes that catalyze the glycosylation of multitype metabolites in tea plants remain unclear. Here, 180 uridine diphosphate-dependent glycosyltransferases that may be involved in the biosynthesis of glycosylated secondary metabolites were identified from the National Center for Biotechnology Information public databases. Subsequently, CsUGT74Y1 was screened through phylogenetic analysis and gene expression profiling. Compositional and induced expression analyses revealed that CsUGT74Y1 was highly expressed in tea tender shoots and was induced under biotic and abiotic stress conditions. In vitro enzymatic assays revealed that rCsUGT74Y1 encoded a multifunctional UGT that catalyzed the glycosylation of flavonoids, phenolic acids, lignins, and auxins. Furthermore, CsUGT74Y1-overexpressing Arabidopsis thaliana exhibited enhanced growth and accumulation of flavonol and auxin glucosides. Our findings provide insights into identifying specific UGTs and demonstrate that CsUGT74Y1 is a multifunctional UGT that promotes plant development.

Clinical features and 1-year outcomes of chronic bronchitis in participants with normal spirometry: results from the ECOPD study in China.

BACKGROUND: Evidence regarding clinical features and outcomes of individuals with non-obstructive chronic bronchitis (NOCB) remains scarce, especially in never-smokers. We aimed to investigate the clinical features and 1-year outcomes of individuals with NOCB in the Chinese population. METHODS: We obtained data on participants in the Early Chronic Obstructive Pulmonary Disease Study who had normal spirometry (post-bronchodilator forced expiratory volume in 1 s/forced vital capacity ≥0.70). NOCB was defined as chronic cough and sputum production for at least 3 months for two consecutive years or more at baseline in participants with normal spirometry. We assessed the differences in demographics, risk factors, lung function, impulse oscillometry, CT imaging and frequency of acute respiratory events between participants with and without NOCB. RESULTS: NOCB was present in 13.1% (149/1140) of participants with normal spirometry at baseline. Compared with participants without NOCB, those with NOCB had a higher proportion of men and participants with smoke exposure, occupational exposure, family history of respiratory diseases and worse respiratory symptoms (all p<0.05), but there was no significant difference in lung function. Never-smokers with NOCB had higher rates of emphysema than those without NOCB, but airway resistance was similar. Ever-smokers with NOCB had greater airway resistance than those without NOCB, but emphysema rates were similar. During 1-year follow-up, participants with NOCB had a significantly increased risk of acute respiratory events compared with participants who did not have NOCB, after adjustment for confounders (risk ratio 2.10, 95% CI 1.32 to 3.33; p=0.002). These results were robust in never-smokers and ever-smokers. CONCLUSIONS: Never-smokers and ever-smokers with NOCB had more chronic obstructive pulmonary disease-related risk factors, evidence of airway disease and greater risk of acute respiratory events than those without NOCB. Our findings support expanding the criteria defining pre-COPD to include NOCB.

Inter-relationships among neutrophilic inflammation, air trapping and future exacerbation in COPD: an analysis of ECOPD study.

BACKGROUND: The inter-relationships among neutrophilic airway inflammation, air trapping and future exacerbation in chronic obstructive pulmonary disease (COPD) remain unclear. OBJECTIVE: To evaluate the associations between sputum neutrophil proportions and future exacerbation in COPD and to determine whether these associations are modified by significant air trapping. METHODS: Participants with completed data were included and followed up to the first year in the Early Chronic Obstructive Pulmonary Disease study (n=582). Sputum neutrophil proportions and high-resolution CT-related markers were measured at baseline. Sputum neutrophil proportions were dichotomised based on their median (86.2%) to low and high levels. In addition, subjects were divided into the air trapping or non-air trapping group. Outcomes of interest included COPD exacerbation (separately any, severe and frequent exacerbation, occurring in the first year of follow-up). Multivariable logistic regressions were performed to examine the risk of severe exacerbation and frequent exacerbation with either neutrophilic airway inflammation groups or air trapping groups. RESULTS: There was no significant difference between high and low levels of sputum neutrophil proportions in the exacerbation in the preceding year. After the first year of follow-up, subjects with high sputum neutrophil proportions had increased risks of severe exacerbation (OR=1.68, 95% CI: 1.09 to 2.62, p=0.020). Subjects with high sputum neutrophil proportions and significant air trapping had increased odds of having frequent exacerbation (OR=3.29, 95% CI: 1.30 to 9.37, p=0.017) and having severe exacerbation (OR=2.72, 95% CI: 1.42 to 5.43, p=0.003) when compared with those who had low sputum neutrophil proportions and non-air trapping. CONCLUSIONS: We found that subjects with high sputum neutrophil proportions and significant air trapping are prone to future exacerbation of COPD. It may be a helpful predictor of future exacerbation.

Impaired exercise capacity in individuals with non-obstructive small airway dysfunction.

Background: Whether individuals with non-obstructive spirometry-defined small airway dysfunction (SAD) have impaired exercise capacity is unclear, particularly in never-smokers. This study clarifies the degree of impaired exercise capacity and its potential cause in individuals with non-obstructive SAD. Methods: This community-based, multiyear cross-sectional study analyzed data collected in Guangdong, China from 2012-2019 by the National Science and Technology Support Plan Program. Measurements of exercise capacity [peak work rate and peak oxygen uptake ( V ˙ O 2peak )] in participants with non-obstructive spirometry-defined SAD (n=157) were compared with those in controls (n=85) and Global Initiative for Chronic Obstructive Lung Disease (GOLD) I patients (n=239). Subgroup analyses were performed by smoking status. Results: The risk of impaired exercise capacity was significantly higher in participants with non-obstructive SAD [ V ˙ O 2peak <84%predicted, adjusted odds ratio (aOR) =2.53; 95% confidence interval (CI): 1.42-4.52] than in controls but was not significantly different from that in GOLD I patients. Results were consistent within subgroups of smoking status (ever-smokers: non-obstructive SAD vs. controls, aOR =2.44; 95% CI: 1.08-5.51; never-smokers: non-obstructive SAD vs. controls, aOR =2.38, 95% CI: 1.02-5.58). Participants with non-obstructive SAD had a significantly lower peak work rate (ß=-10.5; 95% CI: -16.3 to -4.7) and V ˙ O 2peak (%predicted, ß=-4.0; 95% CI: -7.7 to -0.2) and tended to have higher ventilatory equivalents for carbon dioxide at the ventilatory threshold ( V ˙ E / V ˙ CO 2AT , ß=1.1; 95% CI: -0.1 to 2.3) when compared with controls. Both peak work rate and V ˙ O 2peak were negatively correlated with V ˙ E / V ˙ CO 2AT . Conclusions: Although not meeting the current criteria for chronic obstructive pulmonary disease, individuals with non-obstructive SAD have impaired exercise capacity that may be associated with ventilatory inefficiency regardless of smoking status.

Identification of Six Small Heat Shock Protein Genes in Ostrinia furnacalis (Lepidoptera: Pyralidae) and Analysis of Their Expression Patterns in Response to Environmental Stressors.

Ostrinia furnacalis (Guenée) is a major insect pest in maize production that is highly adaptable to the environment. Small heat shock proteins (sHsps) are a class of chaperone proteins that play an important role in insect responses to various environmental stresses. The present study aimed to clarify the responses of six O. furnacalis sHsps to environmental stressors. In particular, we cloned six sHsp genes, namely, OfHsp24.2, OfHsp21.3, OfHsp20.7, OfHsp21.8, OfHsp29.7, and OfHsp19.9, from O. furnacalis. The putative proteins encoded by these genes contained a typical α-crystallin domain. Real-time quantitative polymerase chain reaction was used to analyze the differences in the expression of these genes at different developmental stages, in different tissues of male and female adults, and in O. furnacalis under UV-A and extreme temperature stresses. The six OfsHsp genes were expressed at significantly different levels based on the developmental stage and tissue type in male and female adults. Furthermore, all OfsHsp genes were significantly upregulated in both male and female adults under extreme temperature and UV-A stresses. Thus, O. furnacalis OfsHsp genes play important and unique regulatory roles in the developmental stages of the insect and in response to various environmental stressors.

Molecular characterization and elucidation of the function of Hap38 MAPK in the response of Helicoverpa armigera (Hübner) to UV-A stress.

The cotton bollworm Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), an important pest of cotton, is detrimental to cotton production. Light from UV-A ultraviolet lamps is regarded as a form of environmental stress for insects. In order to investigate the response of H. armigera exposed to UV-A, we explored Hap38 MAPK expression and functions. We hope that the findings of this study will lay the foundation for future investigations into the insect's phototaxis mechanism. A p38 MAPK was cloned and named Hap38 MAPK. A phylogenetic tree showed that Hap38 MAPK was highly conserved. The gene was highly expressed in the thorax and females. Under UV-A stress, the expression of the gene decreased significantly. After silencing Hap38 MAPK, the activity of the antioxidant enzymes SOD, POD, CAT, and GR decreased. This study suggested that Hap38 MAPK responds to UV-A irradiation and plays critical roles in the defense response to environmental stresses.

Molecular characterization of six heat shock protein 70 genes from Arma chinensis and their expression patterns in response to temperature stress.

Arma chinensis is an important predatory enemy of many agricultural and forest pests. Heat shock protein 70 (Hsp70) plays an essential role in insect adaptation to various stress factors. To explore the functions of Hsp70s in relation to thermal tolerance of A. chinensis, full-length cDNAs of six Hsp70 genes (AcHsp70Ba, AcHsp70-4, AcHsp68a, AcHsp68b, AcHsp70-2, and AcHsc70-4) were cloned. Their open reading frames (ORFs) were 1902, 2454, 1884, 1905, 1872, and 1947 bp, respectively. Developmental expression profiles showed that AcHsp70Ba, AcHsp70-4, and AcHsc70-4 were extremely highly expressed in adult stages. AcHsp68a and AcHsp70-2 showed the highest level of expression in nymph stages, and AcHsp68b was mainly expressed in male adults. Tissue distribution analysis demonstrated that the AcHsp70s were ubiquitously expressed but showing gene-specific and sex-driven patterns of expression. High temperature induced the expression of the six AcHsp70s. Among them, AcHsp70Ba, AcHsp70-4, AcHsp68a, and AcHsc70-4 were significantly induced at 38 °C for 6 h, while all six AcHsp70s were significantly induced at 38 °C for 24 h. There were differences in responses of the six AcHsp70s to low-temperature stress. The expressions of AcHsp70-4, AcHsp68a, and AcHsp68b in male adults were significantly repressed at 4 °C for 6 h, whereas AcHsp70Ba and AcHsp70-2 were significantly induced. The levels of AcHsp70Ba, AcHsp68b, and AcHsp70-2 in female adults were significantly repressed at 4 °C for 24 h, whereas AcHsc70-4 was significantly induced. These results suggested that AcHsp70s play important roles in various developmental stages and tissue function, and contribute to the tolerance of A. chinensis to extreme temperatures.

Induced heat shock protein 70 confers biological tolerance in UV-B stress-adapted Myzus persicae (Hemiptera).

As an environmental stress factor, ultraviolet-B (UV-B) radiation directly affects insect growth, development, and reproduction. Heat shock protein 70s kDa (Hsp70s) plays an important role in the environmental adaptation of insects. To determine the role of MpHsp70s in the UV-B tolerance of Myzus persicae (Sulzer), we identified the complete complementary DNA sequences of seven MpHsp70s. They were found to be ubiquitously expressed during different developmental stages and were highly expressed in second-instar nymphs and wingless adults. The expression levels of the MpHsp70s were significantly upregulated when exposed to different durations of UV-B stress. Nanocarrier-mediated dsMpHsp70 suppressed the expression of the MpHsp70s and reduced the body length, weight, survival rate, and fecundity of M. persicae under UV-B exposure. When the combinational RNAi approach was adopted, the effects on the survival rate and fecundity were greater under UV-B stress, except for MpHsc70-4. These results suggest that MpHsp70s are essential for the resistance of M. persicae to UV-B stress.

Two UDP-Glycosyltransferases Catalyze the Biosynthesis of Bitter Flavonoid 7-O-Neohesperidoside through Sequential Glycosylation in Tea Plants.

Flavonoid glycosides are typical bitter and astringent tasting compounds that contribute to the taste of tea beverages. However, the genes that contribute to the biosynthesis of bitter compounds (e.g., flavanone 7-O-neohesperidoside) in tea plants have yet to be identified. In this study, we identified 194 UDP-glycosyltransferases (UGTs) from the tea transcriptome database. Among them, two genes, CsUGT75L12 and CsUGT79B28, encoding flavonoid 7-O-glycosyltransferase and 7-O-glucoside(1→2)rhamnosyltransferase, respectively, were identified from Camellia sinensis. In vitro, the purified recombinant enzyme rCsUGT75L12 specifically transports the glucose unit from UDP-glucose to the 7-OH position of the flavonoid to produce the respective 7-O-glucoside. rCsUGT79B28 regiospecifically transfers a rhamnose unit from UDP-rhamnose to the 2″-OH position of flavonoid 7-O-glucosides to produce flavonoid 7-O-di-glycosides. Additionally, the expression profiles of the two CsUGTs were correlated with the accumulation patterns of 7-O-glucoside and 7-O-neohesperidoside, respectively, in tea plants. These results indicated that the two CsUGTs are involved in the biosynthesis of bitter flavonoid 7-O-neohesperidoside through the sequential glucosylation and rhamnosylation of flavonoids in C. sinensis. Taken together, our findings provided not only molecular insights into flavonoid di-glycoside metabolism in tea plants but also crucial molecular markers for controlling the bitterness and astringent taste of tea.

Expression stability of candidate RT-qPCR housekeeping genes in Spodoptera frugiperda (Lepidoptera: Noctuidae).

Reverse-transcription quantitative polymerase chain reaction (RT-qPCR) is commonly used to quantify gene expression. For normalization, the expression of each gene is compared with a reference "housekeeping" gene that is stably expressed under relevant stress. Unfortunately, there have been no reports on the stability of such reference genes under various treatments of the Spodoptera frugiperda. In this study, we used five tools (RefFinder, GeNorm, NormFinder, BestKeeper, and ΔCt methods) to evaluate the stability of 12 candidate reference genes (RPS18, ß-tubulin, GAPDH, RPS7, RPS15, RPL7, RPL32, Actin-5C, EF1-α, EF1-γ, RPL27, and ACE) in different instars, tissues, and treatments (high and low temperature, UV-A, and emamectin benzoate). Several ribosomal proteins (RPS7, RPS15, RPL32, RPS18, and RPL7), GAPDH, Actin-5C, and ß-tubulin, were relatively stable, suggesting that they are ideal housekeeping genes for various treatments. ACE was extremely unstable under various experimental treatments, rendering it unsuitable as an internal reference. This study identified the reference housekeeping genes stably expressed by S. frugiperda under different treatments, thus setting a foundation for further exploration of the physiological and biochemical mechanisms.

Controlled Synthesis of MoxW1-xTe2 Atomic Layers with Emergent Quantum States.

Recently, new states of matter like superconducting or topological quantum states were found in transition metal dichalcogenides (TMDs) and manifested themselves in a series of exotic physical behaviors. Such phenomena have been demonstrated to exist in a series of transition metal tellurides including MoTe2, WTe2, and alloyed MoxW1-xTe2. However, the behaviors in the alloy system have been rarely addressed due to their difficulty in obtaining atomic layers with controlled composition, albeit the alloy offers a great platform to tune the quantum states. Here, we report a facile CVD method to synthesize the MoxW1-xTe2 with controllable thickness and chemical composition ratios. The atomic structure of a monolayer MoxW1-xTe2 alloy was experimentally confirmed by scanning transmission electron microscopy. Importantly, two different transport behaviors including superconducting and Weyl semimetal states were observed in Mo-rich Mo0.8W0.2Te2 and W-rich Mo0.2W0.8Te2 samples, respectively. Our results show that the electrical properties of MoxW1-xTe2 can be tuned by controlling the chemical composition, demonstrating our controllable CVD growth method is an efficient strategy to manipulate the physical properties of TMDCs. Meanwhile, it provides a perspective on further comprehension and sheds light on the design of devices with topological multicomponent TMDC materials.

Transcriptome Analysis of Myzus persicae to UV-B Stress.

As an environmental stress factor, ultraviolet-B (UV-B) radiation directly affects the growth and development of Myzus persicae (Sulzer) (Homoptera: Aphididae). How M. persicae responds to UV-B stress and the molecular mechanisms underlying this adaptation remain unknown. Here, we analyzed transcriptome data for M. persicae following exposure to UV-B radiation for 30 min. We identified 758 significant differentially expressed genes (DEGs) following exposure to UV-B stress, including 423 upregulated and 335 downregulated genes. In addition, enrichment analysis using the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases illustrated that these DEGs are associated with antioxidation and detoxification, metabolic and protein turnover, immune response, and stress signal transduction. Simultaneously, these DEGs are closely related to the adaptability to UV-B stress. Our research can raise awareness of the mechanisms of insect responses to UV-B stress.

Comparative transcriptome and metabolome analysis of Ostrinia furnacalis female adults under UV-A exposure.

Ultraviolet A (UV-A) radiation is a significant environmental factor that causes photoreceptor damage, apoptosis, and oxidative stress in insects. Ostrinia furnacalis is an important pest of corn. To understand the adaptation mechanisms of insect response to UV-A exposure, this study revealed differentially expressed genes (DEGs) and differently expressed metabolites (DEMs) in O. furnacalis under UV-A exposure. Three complementary DNA libraries were constructed from O. furnacalis adult females (CK, UV1h, and UV2h), and 50,106 expressed genes were obtained through Illumina sequencing. Of these, 157 and 637 DEGs were detected in UV1h and UV2h after UV-A exposure for 1 and 2 h, respectively, compared to CK, with 103 and 444 upregulated and 54 and 193 downregulated genes, respectively. Forty four DEGs were detected in UV2h compared to UV1h. Comparative transcriptome analysis between UV-treated and control groups revealed signal transduction, detoxification and stress response, immune defense, and antioxidative system involvement. Metabolomics analysis showed that 181 (UV1h vs. CK), 111 (UV2h vs. CK), and 34 (UV2h vs. UV1h) DEMs were obtained in positive ion mode, while 135 (UV1h vs. CK), 93 (UV2h vs. CK), and 36 (UV2h vs. UV1h) DEMs were obtained in negative ion mode. Moreover, UV-A exposure disturbed amino acid, sugar, and lipid metabolism. These findings provide insight for further studies on how insects protect themselves under UV-A stress.

Identification of five small heat shock protein genes in Spodoptera frugiperda and expression analysis in response to different environmental stressors.

Spodoptera frugiperda (J. E. Smith) is a highly adaptable polyphagous migratory pest in tropical and subtropical regions. Small heat shock proteins (sHsps) are molecular chaperones that play important roles in the adaptation to various environment stressors. The present study aimed to clarify the response mechanisms of S. frugiperda to various environmental stressors. We obtained five S. furcifera sHsp genes (SfsHsp21.3, SfsHsp20, SfsHsp20.1, SfsHsp19.3, and SfsHsp29) via cloning. The putative proteins encoded by these genes contained a typical α-crystallin domain. The expression patterns of these genes during different developmental stages, in various tissues of male and female adults, as well as in response to extreme temperatures and UV-A stress were studied via real-time quantitative polymerase chain reaction. The results showed that the expression levels of all five SfsHsp genes differed among the developmental stages as well as among the different tissues of male and female adults. The expression levels of most SfsHsp genes under extreme temperatures and UV-A-induced stress were significantly upregulated in both male and female adults. In contrast, those of SfsHsp20.1 and SfsHsp19.3 were significantly downregulated under cold stress in male adults. Therefore, the different SfsHsp genes of S. frugiperda play unique regulatory roles during development as well as in response to various environmental stressors.

Magnitude and Spatial Distribution Control of the Supercurrent in Bi2O2Se-Based Josephson Junction.

Many proposals for exploring topological quantum computation are based on superconducting quantum devices constructed on materials with strong spin-orbit coupling (SOC). For these devices, full control of both the magnitude and the spatial distribution of the supercurrent is highly demanded, but has been elusive up to now. We constructed a proximity-type Josephson junction on nanoplates of Bi2O2Se, a new emerging semiconductor with strong SOC. Through electrical gating, we show that the supercurrent can be fully turned ON and OFF, and its real-space pathways can be configured either through the bulk or along the edges. Our work demonstrates Bi2O2Se as a promising platform for constructing multifunctional hybrid superconducting devices as well as for searching for topological superconductivity.

Phase Transition and Superconductivity Enhancement in Se-Substituted MoTe2 Thin Films.

Consecutively tailoring few-layer transition metal dichalcogenides MX2 from 2H to Td phase may realize the long-sought topological superconductivity in a single material system by incorporating superconductivity and the quantum spin Hall effect together. Here, this study demonstrates that a consecutive structural phase transition from Td to 1T' to 2H polytype can be realized by increasing the Se concentration in Se-substituted MoTe2 thin films. More importantly, the Se-substitution is found to dramatically enhance the superconductivity of the MoTe2 thin film, which is interpreted as the introduction of two-band superconductivity. The chemical-constituent-induced phase transition offers a new strategy to study the s+- superconductivity and the possible topological superconductivity, as well as to develop phase-sensitive devices based on MX2 materials.

Transport evidence of asymmetric spin-orbit coupling in few-layer superconducting 1Td-MoTe2.

Two-dimensional transition metal dichalcogenides MX2 (M = W, Mo, Nb, and X = Te, Se, S) with strong spin-orbit coupling possess plenty of novel physics including superconductivity. Due to the Ising spin-orbit coupling, monolayer NbSe2 and gated MoS2 of 2H structure can realize the Ising superconductivity, which manifests itself with in-plane upper critical field far exceeding Pauli paramagnetic limit. Surprisingly, we find that a few-layer 1Td structure MoTe2 also exhibits an in-plane upper critical field which goes beyond the Pauli paramagnetic limit. Importantly, the in-plane upper critical field shows an emergent two-fold symmetry which is different from the isotropic in-plane upper critical field in 2H transition metal dichalcogenides. We show that this is a result of an asymmetric spin-orbit coupling in 1Td transition metal dichalcogenides. Our work provides transport evidence of a new type of asymmetric spin-orbit coupling in transition metal dichalcogenides which may give rise to novel superconducting and spin transport properties.