Novel MEI1 mutations cause chromosomal and DNA methylation abnormalities leading to embryonic arrest and implantation failure.

This study presents a case of a female infertile patient suffering from embryonic arrest and recurrent implantation failure. The primary objective was to assess the copy number variations (CNVs) and DNA methylation of her embryos. Genetic diagnosis was conducted by whole-exome sequencing and validated through Sanger sequencing. CNV evaluation of two cleavage stage embryos was performed using whole-genome sequencing, while DNA methylation and CNV assessment of two blastocysts were carried out using whole-genome bisulfite sequencing. We identified two novel pathogenic frameshift variants in the MEI1 gene (NM_152513.3, c.3002delC, c.2264_2268 + 11delGTGAGGTATGGACCAC) in the proband. These two variants were inherited from her heterozygous parents, consistent with autosomal recessive genetic transmission. Notably, two Day 3 embryos and two Day 6 blastocysts were all aneuploid, with numerous monosomy and trisomy events. Moreover, global methylation levels greatly deviated from the optimized window of 0.25-0.27, measuring 0.344 and 0.168 for the respective blastocysts. This study expands the mutational spectrum of MEI1 and is the first to document both aneuploidy and abnormal methylation levels in embryos from a MEI1-affected female patient presenting with embryonic arrest. Given that females affected by MEI1 mutations might experience either embryonic arrest or monospermic androgenetic hydatidiform moles due to the extrusion of all maternal chromosomes, the genetic makeup of the arrested embryos of MEI1 patients provides important clues for understanding the different disease mechanisms of the two phenotypes.

Association of the TyG index with prognosis in surgical intensive care patients: data from the MIMIC-IV.

BACKGROUND: The triglyceride-glucose (TyG) index, a tool for assessing insulin resistance, is increasingly recognized for its ability to predict cardiovascular and metabolic risks. However, its relationship with trauma and surgical patient prognosis is understudied. This study investigated the correlation between the TyG index and mortality risk in surgical/trauma ICU patients to identify high-risk individuals and improve prognostic strategies. METHODS: This study identified patients requiring trauma/surgical ICU admission from the Medical Information Mart for Intensive Care (MIMIC-IV) database, and divided them into tertiles based on the TyG index. The outcomes included 28-day mortality and 180-day mortality for short-term and long-term prognosis. The associations between the TyG index and clinical outcomes in patients were elucidated using Cox proportional hazards regression analysis and RCS models. RESULTS: A total of 2103 patients were enrolled. The 28-day mortality and 180-day mortality rates reached 18% and 24%, respectively. Multivariate Cox proportional hazards analysis revealed that an elevated TyG index was significantly related to 28-day and 180-day mortality after covariates adjusting. An elevated TyG index was significantly associated with 28-day mortality (adjusted hazard ratio, 1.19; 95% confidence interval 1.04-1.37) and 180-day mortality (adjusted hazard ratio, 1.24; 95% confidence interval 1.11-1.39). RCS models revealed that a progressively increasing risk of mortality was related to an elevated TyG index. According to our subgroup analysis, an elevated TyG index is associated with increased risk of 28-day and 180-day mortality in critically ill patients younger than 60 years old, as well as those with concomitant stroke or cardiovascular diseases. Additionally, in nondiabetic patients, an elevated TyG index is associated with 180-day mortality. CONCLUSION: An increasing risk of mortality was related to an elevated TyG index. In critically ill patients younger than 60 years old, as well as those with concomitant stroke or cardiovascular diseases, an elevated TyG index is associated with adverse short-term and long-term outcomes. Furthermore, in non-diabetic patients, an elevated TyG index is associated with adverse long-term prognosis.

Ultra-High-Efficiency Corrosion Protection of Metallic Surface Based on Thin and Dense Hexagonal Boron Nitride Coating Films.

Quest for ultrathin and highly effective anticorrosion coating films is critical for both fundamental community of materials science and industrial economics. A two-dimensional hexagonal boron nitride (h-BN) film is a newly developed effective anticorrosion material due to its superior impermeability, thermal stability, and chemical stability. However, research in growth and anticorrosion properties of large-area dense h-BN coating films still lies in its infancy. Here, we report on the synthesis of a large-area and continuous dense few-layer (∼4) h-BN coating film onto a metal surface by chemical vapor deposition (CVD) and its anticorrosion properties both in air and seawater environments. Cu coated in h-BN, which functions as an anticorrosive coating, exhibits an impressively reduced corrosion rate (CR) in a 3.5% NaCl solution (which mimics a seawater environment) when compared to bare Cu (approximately 27 times). At 200 °C, the h-BN coating can prevent Cu foil's surface from oxidizing, although doing so will cause a significant amount of oxide particles to simultaneously form on the bare Cu surface. In the meantime, the performance of the h-BN film remains unaltered after 100 days in an atmospheric environment, demonstrating the ultrahigh stability and corrosion resistance of the as-grown h-BN film.

Co-expression of a pair of interdependent regulators coding genes ovmZ and ovmW awakens the production of angucyclinones antibiotics in Streptomyces neyagawaensis.

BACKGROUND: Microbial genome sequencing and analysis revealed the presence of abundant silent secondary metabolites biosynthetic gene clusters (BGCs) in streptomycetes. Activating these BGCs has great significance for discovering new compounds and novel biosynthetic pathways. RESULTS: In this study, we found that ovmZ and ovmW homologs, a pair of interdependent transcriptional regulators coding genes, are widespread in actinobacteria and closely associated with the biosynthesis of secondary metabolites. Through co-overexpression of native ovmZ and ovmW in Streptomyces neyagawaensis NRRL B-3092, a silent type II polyketide synthase (PKS) gene cluster was activated to produce gephyromycin A, tetrangomycin and fridamycin E with the yields of 22.3 ± 8.0 mg/L, 4.8 ± 0.5 mg/L and 20.3 ± 4.1 mg/L respectively in the recombinant strain of S.ne/pZnWn. However, expression of either ovmZ or ovmW failed to activate this gene cluster. Interestingly, overexpression of the heterologous ovmZ and ovmW pair from oviedomycin BGC of S. ansochromogenes 7100 also led to awakening of this silent angucyclinone BGC in S. neyagawaensis. CONCLUSION: A silent angucyclinone BGC was activated by overexpressing both ovmZ and ovmW in S. neyagawaensis. Due to the wide distribution of ovmZ and ovmW in the BGCs of actinobacteria, co-overexpression of ovmZ and ovmW could be a strategy for activating silent BGCs, thus stimulating the biosynthesis of secondary metabolites.

Sodium, potassium intake, and all-cause mortality: confusion and new findings.

BACKGROUND: The World Health Organization (WHO) has established recommended daily intakes for sodium and potassium. However, there is currently some controversy regarding the association between sodium intake, potassium intake, the sodium-to-potassium ratio, and overall mortality. To assess the correlations between sodium intake, potassium intake, the sodium-to-potassium ratio, and overall mortality, as well as the potential differences in sodium and potassium intake thresholds among different population groups, we analyzed data from NHANES 2003-2018. METHODS: NHANES is an observational cohort study that estimates sodium and potassium intake through one or two 24-h dietary recalls. Hazard ratios (HR) for overall mortality were calculated using multivariable adjusted Cox models accounting for sampling design. A total of 13855 out of 26288 participants were included in the final analysis. Restricted cubic spline analyses were used to examine the relationship between sodium intake, potassium intake, and overall mortality. If non-linearity was detected, we employed a recursive algorithm to calculate inflection points. RESULTS: Based on one or two 24-h dietary recalls, the sample consisted of 13,855 participants, representing a non-institutionalized population aged 40-80 years, totaling 11,348,771 person-months of mean follow-up 99.395 months. Daily sodium intake and daily potassium intake were inversely associated with all-cause mortality. Restrictive cubic spline analysis showed non-linear relationships between daily sodium intake, potassium intake, sodium-potassium ratio, and total mortality. The inflection point for daily sodium intake was 3133 mg/d, and the inflection point for daily potassium intake was 3501 mg/d, and the inflection point for daily sodium-potassium ratio intake was 1.203 mg/mg/d. In subgroup analyses, a significant interaction was found between age and high sodium intake, which was further confirmed by the smooth curves that showed a U-shaped relationship between sodium intake and all-cause mortality in the elderly population, with a inflection point of 3634 mg/d. CONCLUSION: Nonlinear associations of daily sodium intake, daily potassium intake and daily sodium-potassium ratio intake with all-cause mortality were observed in American individuals. The inflection point for daily sodium intake was 3133 mg/d. And the inflection point for daily sodium intake was 3634 mg/d in elderly population. The inflection point for daily potassium intake was 3501 mg/d. The inflection point for daily sodium-potassium ratio intake was 1.203 mg/mg/d, respectively, A healthy diet should be based on reasonable sodium intake and include an appropriate sodium-to-potassium ratio.

[Effects of fine particulate matter on bone mass and osteogenic differentiation of bone marrow mesenchymal stem cells in mice].

OBJECTIVE: To observe the effects of exposure to fine particulate matter(PM_(2.5)) on bone mass, microstructure, biomechanical properties, and osteogenic differentiation ability of bone marrow mesenchymal stem cells(BMSCs) in mice. METHODS: A total of 16 C57BL/6J mice aged 8 weeks were randomly divided into control group(NS group) and PM_(2.5) exposure group(PM group). NS group was given normal saline, PM group was given 14 mg/kg PM_(2.5) suspension, 50 µL, poisoning every 3 day. After 10 weeks, the lungs of mice were taken for HE staining, and the left tibia was taken for Micro CT detection to analyze parameters related to cancellous and cortical bone. The right tibia was taken for HE staining to observe changes in bone trabeculae. Immunohistochemical staining was used to detect type I collagen(Col I), osteoprotegerin(OPG), and nuclear factor-κB receptor activating factor ligand(RANKL) protein expression, tartrate resistant acid phosphatase(TRAP) staining for detection of osteoclasts. Extract primary BMSCs from bilateral femurs, induce osteogenesis, and then perform alkaline phosphatase(ALP) staining to detect ALP activity, alizarin red staining to detect bone mineralization ability, real-time PCR to detect osteocalcin(OCN), ALP, OPG, and RANKL mRNA expression, and biomechanical testing to test the mechanical properties of the femur. RESULTS: Compared with the NS group, the pulmonary alveolar structure of the PM group mice was disrupted and a large number of inflammatory cells gathered. Prompt for successful PM_(2.5) poisoning operation. Micro CT result showed that the bone mineral density(BMD) and bone volume fraction(BV/TV) of the PM group mice were 276.959±15.152 mg/cm~3 and 0.208%±0.009%, respectively. The NS group had 316.709±28.205 mg/cm~3 and 0.236%±0.019%, respectively. The PM group was lower than the NS group(P<0.05), but the trabecular number(Tb. N) There was no statistically significant difference in parameters such as trabecular thickness(Tb. Th) and trabecular separation(Tb. SP)(P>0.05). The HE staining result of the tibia showed that the trabeculae in the NS group were thick, dense, and uniform. The bone trabeculae in the PM group were slender, with a decrease in number, widened spacing, and sparse arrangement. The expression of Col I(0.023±0.009) and OPG(0.036±0.010) in the PM group increased compared to the NS group(0.079±0.007, 0.059±0.012), while the expression of RANKL(0.036±0.006) decreased compared to the NS group(0.022±0.002)(P<0.05); The number of TRAP positive particles increased in the PM group. The experimental result after osteoinduction of BMSCs in mice showed that compared with the NS group, the PM group had a decrease in the number of ALP positive cells and a decrease in the number of calcium nodules. The relative expression of ALP, OCN, and OPG mRNA in the PM group(0.375±0.021, 0.585±0.088, 0.768±0.112) was significantly reduced compared to the NS group(1.001±0.043, 1.006±0.132, 1.002±0.086), while the relative expression of RANKL mRNA(1.278±0.118) was increased compared to the NS group(1.001±0.057)(P<0.05). The biomechanical experimental result showed that the maximum deflection of the NS group was 0.337±0.031 mm, while the maximum deflection of the PM group was 0.258±0.041 mm. Compared with the NS group, the maximum deflection of the PM group decreased significantly(P<0.05), and the maximum stress and maximum load showed a decreasing trend, but the difference was not statistically significant(P>0.05). CONCLUSION: After 10 weeks of exposure to PM_(2.5), it can affect the bone health of mice, and its mechanism may be related to increased osteoclast activity and inhibition of the osteogenic differentiation ability of BMSCs.

Pregnant outcomes of patients with positive anticentromere antibodies receiving in vitro fertilization-embryo transfer. / æŠ—ç€ä¸ç‚¹æŠ—ä½“é˜³æ€§æ‚£è€ ä½“å¤–å—ç²¾ç»“å±€åˆ†æž.

OBJECTIVES: To analyze the pregnant outcomes in patients with positive anti-centromere antibody (ACA) receiving in vitro fertilization (IVF) -embryo transfer (ET) and natural conception. METHODS: A case-control study was used to retrospectively analyze the clinical data of 3955 patients who received in vitro fertilization-embryo transfer therapy and had the results of antinuclear antibody (ANA) spectrum at Zhejiang Provincial People's Hospital from June 2016 to June 2023. Patients with positive ACA and negative ACA were matched at a ratio of 1∶3 using propensity score matching. Embryo outcomes of IVF were compared between the two groups, and the impact of different fertilization methods and the use of immunosuppressants on pregnant outcomes were analyzed using self-matching analysis. The natural conception and disease progress were followed up for ACA-positive patients after IVF failure. RESULTS: The ACA-positive patients accounted for 0.86% of all IVF patients (34/3955) and 2.51% of total ANA-positive IVF patients. Regardless of whether patients received conventional IVF (c-IVF) or intracytoplasmic sperm injection (ICSI), the ACA-positive group exhibited significant differences in oocyte maturity and fertilization compared to the ACA-negative group (both P<0.01). Moreover, the ACA-positive group had a decreased number of D3 suboptimal embryos and D3 optimal embryos (both P<0.05). In 5 cases of ACA-positive patients who underwent ICSI cycles, the double pronuclei rate did not increase compared to c-IVF cycles (P>0.05), and there was a decrease in the number of D3 high-quality embryos and D3 suboptimal embryos (both P<0.05). After 1-2 months of immunosuppressant treatment, 12 ACA-positive patients underwent c-IVF/ICSI again, and there were no changes in egg retrieval and fertilization before and after medication (both P>0.05), but there was an improvement in the 2PN embryo cleavage rate (P<0.05). The number of embryos transferred was similar between the ACA-positive and negative groups, but the ACA-positive group had significantly lower embryo implantation rate and clinical pregnancy rate compared to the ACA-negative group (both P<0.05), with no significant difference in miscarriage rate between the two groups (P>0.05). Twenty-seven ACA-positive patients attempted natural conception or artificial insemination after IVF failure, resulting in a total of 7 cases of clinical pregnancy. CONCLUSIONS: Serum ACA positivity may disrupt oocyte maturation and normal fertilization processes, with no improvement observed with ICSI and immunosuppressant use. However, ACA-positive patients may still achieve natural pregnancy.

Structure-based interface engineering methodology in designing a thermostable amylose-forming transglucosylase.

Many drugs and prebiotics derive their activities from sugar substituents. Due to the prevalence and complexity of these biologically active compounds, enzymatic glycodiversification that facilitates easier access to these compounds can make profound contributions to the pharmaceutical, food, and feed industries. Amylosucrases (ASases) are attractive tools for glycodiversification because of their broad acceptor substrate specificity, but the lack of structural information and their poor thermostability limit their industrial applications. Herein, we reported the crystal structure of ASase from Calidithermus timidus, which displays a homotetrameric quaternary organization not previously observed for other ASases. We employed a workflow composed of five common strategies, including interface engineering, folding energy calculations, consensus sequence, hydrophobic effects enhancement, and B-factor analysis, to enhance the thermostability of C. timidus ASase. As a result, we obtained a quadruple-point mutant M31 ASase with a half-life at 65 °C increased from 22.91 h to 52.93 h, which could facilitate biosynthesis of glucans with a degree of polymerization of more than 20 using sucrose as a substrate at 50 °C. In conclusion, this study provides a structural basis for understanding the multifunctional biocatalyst ASase and presents a powerful methodology to effectively and systematically enhance protein thermostability.

Glycosylation of flavonoids by sucrose- and starch-utilizing glycoside hydrolases: A practical approach to enhance glycodiversification.

Flavonoids are ubiquitous and diverse in plants and inseparable from the human diet. However, in terms of human health, their further research and application in functional food and pharmaceutical industries are hindered by their low water solubility. Therefore, flavonoid glycosylation has recently attracted research attention because it can modulate the physicochemical and biochemical properties of flavonoids. This review represents a comprehensive overview of the O-glycosylation of flavonoids catalyzed by sucrose- and starch-utilizing glycoside hydrolases (GHs). The characteristics of this feasible biosynthesis approach are systematically summarized, including catalytic mechanism, specificity, reaction conditions, and yields of the enzymatic reaction, as well as the physicochemical properties and bioactivities of the product flavonoid glycosides. The cheap glycosyl donor substrates and high yields undoubtedly make it a practical flavonoid modification approach to enhance glycodiversification.

Intertemporal Decision-making and Risk Decision-making Among Habitual Nappers Under Nap Sleep Restriction: A Study from ERP and Time-frequency.

Sleep restriction affects people's decision-making behavior. Nap restriction is a vital subtopic within sleep restriction research. In this study, we used EEG to investigate the impact of nap sleep restriction on intertemporal decision-making (Study 1) and decision-making across risky outcomes (Study 2) from ERP and time-frequency perspectives. Study 1 found that habitual nappers restricting their naps felt more inclined to choose immediate, small rewards over delayed, large rewards in an intertemporal decision-making task. P200s, P300s, and LPP in our nap-restriction group were significantly higher than those in the normal nap group. Time-frequency results showed that the delta band (1 ~ 4 Hz) power of the restricted nap group was significantly higher than that of the normal nap group. In Study 2, the nap-restriction group was more likely to choose risky options. P200s, N2s, and P300s in the nap deprivation group were significantly higher than in the normal nap group. Time-frequency results also found that the beta band (11 ~ 15 Hz) power of the restricted nap group was significantly lower than that of the normal nap group. The habitual nappers became more impulsive after nap restriction and evinced altered perceptions of time. The time cost of the LL (larger-later) option was perceived to be too high when making intertemporal decisions, and their expectation of reward heightened when making risky decisions-believing that they had a higher probability of receiving a reward. This study provided electrophysiological evidence for the dynamic processing of intertemporal decision-making, risky decision-making, and the characteristics of nerve concussions for habitual nappers.

An efficient method for targeted cloning of large DNA fragments from Streptomyces.

Cloning of large DNA fragments from microorganisms becomes increasingly important but remains seriously challenging due to the complexity and diversity of genetic background. In particular, the methods with high precision and efficiency are in great need for obtaining intact biosynthetic gene clusters (BGCs) of microbial natural products. Here, we report a new strategy for targeted cloning of large DNA fragments (TCLD) from different bacteria. Using this method, precise cloning of desired E. coli chromosomal fragments up to 201 kb was achieved with 53% positive rate. Moreover, its application in cloning of large BGCs with high G + C content and multiple repetitive sequences was also demonstrated, including the 98 kb tylosin BGC (tyl), 128 kb daptomycin BGC (dpt), and 127 kb salinomycin BGC (sal). Subsequently, heterologous expression of the cloned tyl BGC in Streptomyces coelicolor M1146 led to the production of tylosins in the resulting recombinant strains. And also, its introduction into Streptomyces fradiae ATCC 19609, a native producer of tylosin, effectively increased tylosin yield to 230%. Hence, TCLD is a powerful tool for cloning large BGCs and would facilitate the discovery of bioactive substances from microbial resources. KEY POINTS: • TCLD is an efficient method for cloning large DNA fragments. • Repeat sequence-mediated intra-molecular cyclization improves the cloning efficiency. • TCLD combined with scarless editing allows unlimited modifications on BGCs.

Rheological properties and dewaterability of anaerobic co-digestion with sewage sludge and food waste: effect of thermal hydrolysis pretreatment and mixing ratios.

Anaerobic co-digestion (co-AD) of sewage sludge (SS) and food waste (FW) converts municipal organic waste into renewable energy, which plays an important role in achieving carbon emissions reduction. The existing anaerobic digestion (AD) treatment projects often have problems such as low organic conversion and unstable performance. SS and FW were used as raw materials to explore the effects of thermal hydrolysis pretreatment (THP) and mixing ratios on the dewaterability and rheological properties of the digestate. The results showed that co-digestion of FW and SS in a ratio of 1:1 obtained the highest biogas production (255.14 mL/g VS), which was 1.53 times and 14.5 times higher than that of mono-digestion of FW and thermal hydrolysis pretreatment sewage sludge (THSS), respectively. However, the dewaterability of this ratio deteriorated sharply after co-digestion, with a decrease of 54.92%. The groups containing a higher proportion of THSS had improved dewaterability after AD. The apparent viscosity and shear stress were reduced by co-digestion compared with mono-digestion of THSS and FW, indicating a higher flow property of the co-digestion matrix. After the Herschel-Bulkley model fitting, there were linear correlations between rheological indices and soluble chemical oxygen demand (SCOD), and digestate dewaterability.

A butenolide signaling system synergized with biosynthetic gene modules led to effective activation and enhancement of silent oviedomycin production in Streptomyces.

Secondary metabolic gene clusters widely exist in the genomes of Streptomyces but mostly remain silent. To awaken this hidden reservoir of natural products, various strategies concerning secondary metabolic pathways are applied. Here, we describe that butenolide signaling molecule deficiency and glucose addition can interdependently activate the expression of silent oviedomycin biosynthetic gene clusters in Streptomyces ansochromogenes and Streptomyces antibioticus. Since oviedomycin is a promising anti-tumor lead compound, in order to improve its yield, we use the cluster-situated genes (ovmF, ovmG, ovmI and ovmH) encoding the enzymes for acyl carrier protein modification and precursor biosynthesis, and the discrete precursor biosynthetic genes (pyk2, gap1 and accA2) involved in glycolysis to assemble two gene modules (pFGIH and pPGA). Their co-overexpression in ΔsabA (a disruption mutant of sabA encoding SAB synthase) has superimposed effect on the yield of oviedomycin, which can be further increased to 59-fold in the presence of galactose as optimal carbon source. This is the most unambiguous evidence that butenolide signaling system can synergize with the optimization of primary metabolism to regulate the expression of secondary metabolic gene clusters, providing efficient strategies for mining natural products of Streptomyces.

Correction to: Sucrose isomers as alternative sweeteners: properties, production, and applications.

There is an error in the original publication of this paper. Figures 1 and 2 have been interchanged. The corrected version of these figures is shown below.

Perceptions of ecosystem services, disservices and willingness-to-pay for urban green space conservation.

While planning and management of urban green space (UGS) remain primarily driven by policymakers and expert knowledge, increasing attention has been paid to the general public's perception of and demand for UGS. This study was conducted to provide price-related outcomes to support UGS-related decision making and achieve an improved understanding of the causal relationships underpinning the residents' willingness-to-pay (WTP) for UGS conservation. An extensive survey with 3000 urban residents from three provincial capital cities in central China (i.e., Wuhan, Changsha and Nanchang) was conducted. We applied structural equation modelling to examine a range of hypothetical causal relationships among residents' perceptions about ecosystem services/disservices provided by UGS, frequency of UGS visits, socioeconomic status (SES) and WTP for the conservation of five different types of UGS. We found that residents had an average WTP of 202.4 CNY or 30.6 USD per year cross UGS types, with the attached green space having the greatest WTP (223.0 CNY or 33.7 USD per year), followed by park (215.4 CNY or 32.6 USD year), square (201.7 CNY or 30.5 USD year), suburban ecological (190.1 CNY or 28.7 USD year) and protective (182.0 CNY or 27.5 USD year) green spaces. Perceptions of UGS's ecosystem services had a positive causal impact on WTP, while perceptions of ecosystem disservices would have a negative impact. The frequency of UGS visits was found to amplify WTP at a limited level. It could further heighten and diminish the perceptions of ecosystem services and disservices. Participants with higher SES typically had greater perceptions of UGS's ecosystem services and WTP. Finally, we found that the structure of the causal relationships on WTP varied between cities, highlighting the importance of considering the fine-level impacts of biophysical environment jointly. Our results could help urban planners to understand better the ways urban green space was perceived and anticipate the likely effects of changing spatial patterns of UGS on the benefits and nuisances experienced by the general public.

Identification of a butenolide signaling system that regulates nikkomycin biosynthesis in Streptomyces.

Butenolides are an emerging family of signaling molecules in Streptomyces. They control complex physiological traits, such as morphological differentiation and antibiotic production. However, how butenolides regulate these processes is poorly investigated because of obstacles in obtaining these signaling molecules. This study reports the identification of a butenolide-type signaling system for nikkomycin biosynthesis in Streptomyces ansochromogenes with distinct features. We identified a gene cluster, sab, consisting of three genes, sabAPD, for butenolide biosynthesis and two regulator genes, sabR1 and sabR2, and characterized three butenolides (SAB1, -2, and -3) by heterologous expression of sabAPD. sabA disruption abolished nikkomycin production, which could be restored by the addition of SABs or by deletion of sabR1 in ΔsabA. Electrophoretic mobility-shift assays and transcriptional analyses indicated that SabR1 indirectly represses the transcription of nikkomycin biosynthetic genes, but directly represses sabA and sabR1 In the presence of SABs, the SabR1 transcriptional regulator dissociated from its target genes, verifying that SabR1 is the cognate receptor of SABs. Genome-wide scanning with the conserved SabR1-binding sequence revealed another SabR1 target gene, cprC, whose transcription was strongly repressed by SabR1. Intriguingly, CprC positively regulated the pleiotropic regulatory gene adpA by binding to its promoter and, in turn, activated nikkomycin biosynthesis. This is the first report that butenolide-type signaling molecules and their cognate receptor SabR1 can regulate adpA via a newly identified activator, CprC, to control nikkomycin production. These findings pave the way for further studies seeking to unravel the regulatory mechanism and functions of the butenolide signaling system in Streptomyces.

A neglected alliance in battles against parasitic plants: arbuscular mycorrhizal and rhizobial symbioses alleviate damage to a legume host by root hemiparasitic Pedicularis species.

Despite their ubiquitous distribution and significant ecological roles, soil microorganisms have long been neglected in investigations addressing parasitic plant-host interactions. Because nutrient deprivation is a primary cause of host damage by parasitic plants, we hypothesized that beneficial soil microorganisms conferring nutrient benefits to parasitized hosts may play important roles in alleviating damage. We conducted a pot cultivation experiment to test the inoculation effect of an arbuscular mycorrhizal fungus (Glomus mosseae), a rhizobium (Rhizobium leguminosarum) and their interactive effects, on alleviation of damage to a legume host (Trifolium repens) by two root hemiparasitic plants with different nutrient requirements (N-demanding Pedicularis rex and P-demanding P. tricolor). Strong interactive effects between inoculation regimes and hemiparasite identity were observed. The relative benefits of microbial inoculation were related to hemiparasite nutrient requirements. Dual inoculation with the rhizobium strongly enhanced promotional arbuscular mycorrhizal effects on hosts parasitized by P. rex, but reduced the arbuscular mycorrhizal promotion on hosts parasitized by P. tricolor. Our results demonstrate substantial contribution of arbuscular mycorrhizal and rhizobial symbioses to alleviating damage to the legume host by root hemiparasites, and suggest that soil microorganisms are critical factors regulating host-parasite interactions and should be taken into account in future studies.

Sucrose isomers as alternative sweeteners: properties, production, and applications.

In the daily diet, sweeteners play an indispensable role. Among them, sucrose, a widely occurring disaccharide in nature, is a commonly used sweetener. However, the intake of sucrose can cause a rapid increase in blood glucose, which leads to a number of health problems. Therefore, there is an urgent need for possible alternatives to sucrose. Currently, four naturally occurring sucrose isomers, trehalulose, turanose, leucrose, and isomaltulose are considered to be possible alternatives to sucrose due to their suitable sweetness, potential physiological benefits, and feasible production processes. This review covers the properties of these alternative sweeteners, including their structure, sweetness, hydrolysis rate, toxicology, and cariogenicity, and exhibits their potential applications in chronic diseases management, anti-inflammatory supplement, prebiotic dietary supplement, and stabilizing agent. The biosynthesis of these sucrose isomers using carbohydrate-active enzymes and their industrial production processes are also systematically summarized.

Activation and mechanism of a cryptic oviedomycin gene cluster via the disruption of a global regulatory gene, adpA, in Streptomyces ansochromogenes.

Genome sequencing analysis has revealed at least 35 clusters of likely biosynthetic genes for secondary metabolites in Streptomyces ansochromogenes. Disruption of adpA encoding a global regulator (AdpA) resulted in the failure of nikkomycin production, whereas other antibacterial activities against Staphylococcus aureus, Bacillus cereus, and Bacillus subtilis were observed with the fermentation broth of ΔadpA but not with that of the wild-type strain. Transcriptional analysis showed that a cryptic gene cluster (pks7), which shows high identity with an oviedomycin biosynthetic gene cluster (ovm), was activated in ΔadpA. The corresponding product of pks7 was characterized as oviedomycin by MS and NMR spectroscopy. To understand the molecular mechanism of ovm activation, the roles of six regulatory genes situated in the ovm cluster were investigated. Among them, proteins encoded by co-transcribed genes ovmZ and ovmW are positive regulators of ovm AdpA directly represses the transcription of ovmZ and ovmW Co-overexpression of ovmZ and ovmW can relieve the repression of AdpA on ovm transcription and effectively activate oviedomycin biosynthesis. The promoter of ovmOI-ovmH is identified as the direct target of OvmZ and OvmW. This is the first report that AdpA can simultaneously activate nikkomycin biosynthesis but repress oviedomycin biosynthesis in one strain. Our findings provide an effective strategy that is able to activate cryptic secondary metabolite gene clusters by genetic manipulation of global regulatory genes.