Regulating the Selectivity of Nitrate Photoreduction for Purification or Ammonia Production by Cooperating Oxidative Half-Reactions.

The removal and conversion of nitrate (NO3-) from wastewater has become an important environmental and health topic. The NO3- can be reduced to nontoxic nitrogen (N2) for environmental remediation or ammonia (NH3) for recovery, in which the tailoring of the selectivity is greatly challenging. Here, by construction of the CuOx@TiO2 photocatalyst, the NO3- conversion efficiency is enhanced to ∼100%. Moreover, the precise regulation of selectivity to NH3 (∼100%) or N2 (92.67%) is accomplished by the synergy of cooperative redox reactions. It is identified that the selectivity of the NO3- photoreduction is determined by the combination of different oxidative reactions. The key roles of intermediates and reactive radicals are revealed by comprehensive in situ characterizations, providing direct evidence for the regulated selectivity of the NO3- photoreduction. Different active radicals are produced by the interaction of oxidative reactants and light-generated holes. Specifically, the introduction of CH3CHO as the oxidative reactant results in the generation of formate radicals, which drives selective NO3- reduction into N2 for its remediation. The alkyl radicals, contributed to by the (CH2OH)2 oxidation, facilitate the deep reduction of NO3- to NH3 for its upcycling. This work provides a technological basis for radical-directed NO3- reduction for its purification and resource recovery.

Mechanically tough, adhesive, self-healing hydrogel promotes annulus fibrosus repair via autologous cell recruitment and microenvironment regulation.

Annulus fibrosus (AF) defect is an important cause of disc re-herniation after discectomy. The self-regeneration ability of the AF is limited, and AF repair is always hindered by the inflammatory microenvironment after injury. Hydrogels represent one of the most promising materials for AF tissue engineering strategies. However, currently available commercial hydrogels cannot withstand the harsh mechanical load within intervertebral disc. In the present study, an innovative triple cross-linked oxidized hyaluronic acid (OHA)-dopamine (DA)- polyacrylamide (PAM) composite hydrogel, modified with collagen mimetic peptide (CMP) and supplied with transforming growth factor beta 1 (TGF-ß1) (OHA-DA-PAM/CMP/TGF-ß1 hydrogel) was developed for AF regeneration. The hydrogel exhibited robust mechanical strength, strong bioadhesion, and significant self-healing capabilities. Modified with collagen mimetic peptide, the hydrogel exhibited extracellular-matrix-mimicking properties and sustained the AF cell phenotype. The sustained release of TGF-ß1 from the hydrogel was pivotal in recruiting AF cells and promoting extracellular matrix production. Furthermore, the composite hydrogel attenuated LPS-induced inflammatory response and promote ECM synthesis in AF cells via suppressing NFκB/NLRP3 pathway. In vivo, the composite hydrogel successfully sealed AF defects and alleviated intervertebral disk degeneration in a rat tail AF defect model. Histological evaluation showed that the hydrogel integrated well with host tissue and facilitated AF repair. The strategy of recruiting endogenous cells and providing an extracellular-matrix-mimicking and anti-inflammatory microenvironment using the mechanically tough composite OHA-DA-PAM/CMP/TGF-ß1 hydrogel may be applicable for AF defect repair in the clinic. STATEMENT OF SIGNIFICANCE: Annulus fibrosus (AF) repair is challenging due to its limited self-regenerative capacity and post-injury inflammation. In this study, a mechanically tough and highly bioadhesive triple cross-linked composite hydrogel, modified with collagen mimetic peptide (CMP) and supplemented with transforming growth factor beta 1 (TGF-ß1), was developed to facilitate AF regeneration. The sustained release of TGF-ß1 enhanced AF cell recruitment, while both TGF-ß1 and CMP could modulate the microenvironment to promote AF cell proliferation and ECM synthesis. In vivo, this composite hydrogel effectively promoted the AF repair and mitigated the intervertebral disc degeneration. This research indicates the clinical potential of the OHA-DA-PAM/CMP/TGF-ß1 composite hydrogel for repairing AF defects.

Role and Mechanism of Epigenetic Regulation in the Aging of Germ Cells: Prospects for Targeted Interventions.

In modern times, a notable trend toward delayed childbearing has been observed in most developed countries. As a result, sperm aging and quality loss, as well as premature ovarian failure (POF), have emerged as major causes of infertility. The pathogenesis of sperm aging and POF is complex and has not been clearly elucidated. However, evidence from some studies has linked germ cell aging to epigenetic modifications. Epigenetics refers to the heritable changes in gene expression that occur in the absence of any alterations to the gene's nucleotide sequence. This paper systematically reviewed and analyzed the relevant literature to describe the relationship of DNA methylation, non-coding RNA regulation, histone modifications, chromatin remodeling, and RNA modifications with sperm aging and POF. In addition, we analyzed how sperm aging and POF can be mitigated via epigenetic interventions. This review could provide new therapeutic insights and guide strategies for improving sperm quality and ovarian function.

Determination for KIR genotype and allele copy number via real-time quantitative PCR method.

Killer cell immunoglobulin-like receptor (KIR) and human leukocyte antigen (HLA) play crucial roles in regulating NK cell activity. Here, we report a real-time quantitative PCR (qPCR) to genotype all KIR genes and their copy numbers simultaneously. With 18 pairs of locus-specific primers, we identified KIR genes by Ct values and determined KIR copy number using the 2-∆Ct method. Haplotypes were assigned based on KIR gene copy numbers. The real-time qPCR results were consistent with the NGS method, except for one sample with KIR2DL5 discrepancy. qPCR is a multiplex method that can identify KIR copy number, which helps obtain a relatively accurate haplotype structure, facilitating increased KIR research in laboratories where NGS or other high-resolution methods are not available.

Root branching under high salinity requires auxin-independent modulation of LATERAL ORGAN BOUNDARY DOMAIN 16 function.

Salinity stress constrains lateral root (LR) growth and severely affects plant growth. Auxin signaling regulates LR formation, but the molecular mechanism by which salinity affects root auxin signaling and whether salt induces other pathways that regulate LR development remains unknown. In Arabidopsis thaliana, the auxin-regulated transcription factor LATERAL ORGAN BOUNDARY DOMAIN 16 (LBD16) is an essential player in LR development under control conditions. Here, we show that under high-salt conditions, an alternative pathway regulates LBD16 expression. Salt represses auxin signaling but, in parallel, activates ZINC FINGER OF ARABIDOPSIS THALIANA 6 (ZAT6), a transcriptional activator of LBD16. ZAT6 activates LBD16 expression, thus contributing to downstream cell wall remodeling and promoting LR development under high-salt conditions. Our study thus shows that the integration of auxin-dependent repressive and salt-activated auxin-independent pathways converging on LBD16 modulates root branching under high-salt conditions.

Dynamic in situ Formation of Cu2 O Sub-Nanoclusters through Photoinduced pseudo-Fehling's Reaction for Selective and Efficient Nitrate-to-Ammonia Photosynthesis.

Copper (Cu) is evidenced to be effective for constructing advanced catalysts. In particular, Cu2 O is identified to be active for general catalytic reactions. However, conflicting results regarding the true structure-activity correlations between Cu2 O-based active sites and efficiencies are usually reported. The structure of Cu2 O undergoes dynamic evolution rather than remaining stable under working conditions, in which the actual reaction cannot proceed over the prefabricated Cu2 O sites. Therefore, the dynamic construction of Cu2 O active sites can be developed to promote catalytic efficiency and reveal the true structure-activity correlations. Herein, by introducing the redox pairs of Cu2+ and reducing sugar into a photocatalysis system, it is clarified that the Cu2 O sub-nanoclusters (NCs), working as novel active sites, are on-site constructed on the substrate via a photoinduced pseudo-Fehling's route. The realistic interfacial charge separation and transformation capacities are remarkably promoted by the dynamic Cu2 O NCs under the actual catalysis condition, which achieves a milestone efficiency for nitrate-to-ammonia photosynthesis, including the targets of production rate (1.98±0.04 mol gCu -1 h-1 ), conversion ratio (94.2±0.91 %), and selectivity (98.6 %±0.55 %). The current work develops an effective strategy for integrating the active site construction into realistic reactions, providing new opportunities for Cu-based chemistry and catalysis sciences research.

Promoting the efficiency and selectivity of NO3--to-NH3 reduction on Cu-O-Ti active sites via preferential glycol oxidation with holes.

The combined reductive and oxidative reaction is the essence of a solar-driven photoredox system. Unfortunately, most of these efforts focus on the specific half-reactions, and the key roles of complete photoredox reactions have been overlooked. Taking the nitrate reduction reaction (NO3-RR) as a typical multiple-electrons involved process, the selective reduction of the NO3- into ammonia (NH3) synthesis with high efficiency is still a grand challenge. Herein, a rational oxidative half-reaction is tailored to achieve the selective conversion of NO3- to NH3 on Cu-O-Ti active sites. Through the coupled NO3-RR with glycol oxidation reaction system, a superior NH3 photosynthesis rate of 16.04 ± 0.40 mmol gcat-1 h-1 with NO3- conversion ratio of 100% and almost 100% of NH3 selectivity is reached on Cu-O-Ti bimetallic oxide cluster-anchored TiO2 nanosheets (CuOx@TNS) catalyst. A combination of comprehensive in situ characterizations and theoretical calculations reveals the molecular mechanism of the synergistic interaction between NO3-RR and glycol oxidation pair on CuOx@TNS. The introduction of glycol accelerates the h+ consumption for the formation of alkoxy (•R) radicals to avoid the production of •OH radicals. The construction of Cu-O-Ti sites facilitates the preferential oxidation of glycol with h+ and enhances the production of e- to participate in NO3-RR. The efficiency and selectivity of NO3--to-NH3 synthesis are thus highly promoted on Cu-O-Ti active sites with the accelerated glycol oxidative half-reaction. This work upgrades the conventional half photocatalysis into a complete photoredox system, demonstrating the tremendous potential for the precise regulation of reaction pathway and product selectivity.

Pyroptosis and inflammasomes in cancer and inflammation.

Nonprogrammed cell death (NPCD) and programmed cell death (PCD) are two types of cell death. Cell death is significantly linked to tumor development, medication resistance, cancer recurrence, and metastatic dissemination. Therefore, a comprehensive understanding of cell death is essential for the treatment of cancer. Pyroptosis is a kind of PCD distinct from autophagy and apoptosis in terms of the structure and function of cells. The defining features of pyroptosis include the release of an inflammatory cascade reaction and the expulsion of lysosomes, inflammatory mediators, and other cellular substances from within the cell. Additionally, it displays variations in osmotic pressure both within and outside the cell. Pyroptosis, as evidenced by a growing body of research, is critical for controlling the development of inflammatory diseases and cancer. In this paper, we reviewed the current level of knowledge on the mechanism of pyroptosis and inflammasomes and their connection to cancer and inflammatory diseases. This article presents a theoretical framework for investigating the potential of therapeutic targets in cancer and inflammatory diseases, overcoming medication resistance, establishing nanomedicines associated with pyroptosis, and developing risk prediction models in refractory cancer. Given the link between pyroptosis and the emergence of cancer and inflammatory diseases, pyroptosis-targeted treatments may be a cutting-edge treatment strategy.

Continuous NO Upcycling into Ammonia Promoted by SO2 in Flue Gas: Poison Can Be a Gift.

Although ammonia (NH3) synthesis efficiency from the NO reduction reaction (NORR) is significantly promoted in recent years, one should note that NO is one of the major air pollutants in the flue gas. The limited NO conversion ratio is still the key challenge for the sustainable development of the NORR route, which potentially contributes more to contaminant emissions rather than its upcycling. Herein, we provide a simple but effective approach for continuous NO reduction into NH3, promoted by coexisting SO2 poison as a gift in the flue gas. It is significant to discover that SO2 plays a decisive role in elevating the capacity of NO absorption and reduction. A unique redox pair of SO2-NO is constructed, which contributes to the exceptionally high conversion ratio for both NO (97.59 ± 1.42%) and SO2 (99.24 ± 0.49%) in a continuous flow. The ultrahigh selectivity for both NO-to-NH3 upcycling (97.14 ± 0.55%) and SO2-to-SO42- purification (92.44 ± 0.71%) is achieved synchronously, demonstrating strong practicability for the value-added conversion of air contaminants. The molecular mechanism is revealed by comprehensive in situ technologies to identify the essential contribution of SO2 to NO upcycling. Besides, realistic practicality is realized by the efficient product recovery and resistance ability against various poisoning effects. The proposed strategy in this work not only achieves a milestone efficiency for NH3 synthesis from the NORR but also raises great concerns about contaminant resourcing in realistic conditions.

Biological roles of A-to-I editing: implications in innate immunity, cell death, and cancer immunotherapy.

Adenosine-to-inosine (A-to-I) editing, a key RNA modification widely found in eukaryotes, is catalyzed by adenosine deaminases acting on RNA (ADARs). Such RNA editing destabilizes endogenous dsRNAs, which are subsequently recognized by the sensors of innate immune and other proteins as autologous dsRNAs. This prevents the activation of innate immunity and type I interferon-mediated responses, thereby reducing the downstream cell death induced by the activation of the innate immune sensing system. ADARs-mediated editing can also occur in mRNAs and non-coding RNAs (ncRNAs) in different species. In mRNAs, A-to-I editing may lead to missense mutations and the selective splicing of coding regions. Meanwhile, in ncRNAs, A-to-I editing may affect targeting and disrupt ncRNAs maturation, leading to anomalous cell proliferation, invasion, and responses to immunotherapy. This review highlights the biological functions of A-to-I editing, its role in regulating innate immunity and cell death, and its potential molecular significance in tumorigenesis and cancer targeted therapy and immunotherapy.

Prevalence, serotype, and antimicrobial resistance profiles of children infected with Salmonella in Guangzhou, southern China, 2016-2021.

Purpose: Salmonella infection is a key global public health concern and has lead to an increased economic burden on society. We investigated the epidemiological characteristics and antimicrobial resistance profiles of clinically isolated Salmonella strains in Guangzhou Women and Children's Medical Center. Patients and methods: This was a retrospective study of 1,338 Salmonella strains collected from children in Guangzhou Women and Children's Medical Center during 2016 to 2021. Results: The results revealed that 1,338 cases of Salmonella were mainly isolated from feces and blood samples. The age distribution was dominated by infants under 3 years old. The seasonal distribution was high in summer and autumn. 48 serotypes were detected, and S. typhimurium (78.7%) was the predominant serogroup. The results of antimicrobial susceptibility showed that the highest resistance was observed in ampicillin (84.5%), while lower resistance was observed in piperacillin/tazobactam, cefoperazone/sulbactam and ciprofloxacin. The antimicrobial resistance rate of fecal isolates was higher than that of blood isolates. The five-year average detection rate of multi-drug resistant Salmonella was 8.5% (114/1338) and the MDR rate of S. typhimurium was the lowest (6.9%; 73/1053). Conclusion: We concluded that antibacterial treatment should be carefully selected according to serotype and antimicrobial sensitivity results in children. Antimicrobial resistance monitoring for multi-drug resistant Salmonella is still required.

Combined Photoredox Catalysis for Value-Added Conversion of Contaminants at Spatially Separated Dual Active Sites.

As 2 indispensable counterparts in one catalysis system, the independent reduction and oxidation reactions require synergetic regulation for cooperatively promoting redox efficiency. Despite the current success in promoting the catalytic efficiency of half reduction or oxidation reactions, the lack of redox integration leads to low energy efficiency and unsatisfied catalytic performance. Here, we exploit an emerging photoredox catalysis system by combining the reactions of nitrate reduction for ammonia synthesis and formaldehyde oxidation for formic acid production, in which superior photoredox efficiency is achieved on the spatially separated dual active sites of Ba single atoms and Ti3+. High catalytic redox rates are accomplished for respective ammonia synthesis (31.99 ± 0.79 mmol gcat -1 h-1) and formic acid production (54.11 ± 1.12 mmol gcat -1 h-1), reaching a photoredox apparent quantum efficiency of 10.3%. Then, the critical roles of the spatially separated dual active sites are revealed, where Ba single atoms as the oxidation site using h+ and Ti3+ as the reduction site using e- are identified, respectively. The efficient photoredox conversion of contaminants is accomplished with environmental importance and competitive economic value. This study also represents a new opportunity to upgrade the conventional half photocatalysis into the complete paradigm for sustainable solar energy utilization.

Beyond Purification: Highly Efficient and Selective Conversion of NO into Ammonia by Coupling Continuous Absorption and Photoreduction under Ambient Conditions.

Although the selective catalytic reduction technology has been confirmed to be effective for nitrogen oxide (NOx) removal, green and sustainable NOx re-utilization under ambient conditions is still a great challenge. Herein, we develop an on-site system by coupling the continuous chemical absorption and photocatalytic reduction of NO in simulated flue gas (CNO = 500 ppm, GHSV = 18,000 h-1), which accomplishes an exceptional NO conversion into value-added ammonia with competitive conversion efficiency (89.05 ± 0.71%), ammonia production selectivity (95.58 ± 0.95%), and ammonia recovery efficiency (>90%) under ambient conditions. The anti-poisoning capacities, including the resistance against factors of H2O, SO2, and alkali/alkaline/heavy metals, are also achieved, which presents strong environmental practicability for treating NOx in flue gas. In addition, the critical roles of corresponding chemical absorption and catalytic reduction components are also revealed by in situ characterizations. The emerging strategy herein not only achieves a milestone efficiency for sustainable NO purification but also opens a new route for contaminant resourcing in the near future of carbon neutrality.

Molecular Characterization and Epidemiology of Carbapenem-Resistant Enterobacteriaceae Isolated from Pediatric Patients in Guangzhou, Southern China.

Background: Carbapenem-resistant Enterobacteriaceae (CRE) are spreading worldwide, posing a serious public health concern. However, the data on CRE strains that cause infections in children in Guangzhou remain limited. Therefore, this study aimed to investigate the epidemiology of CRE, drug resistance, and resistance mechanisms in children in Guangzhou, Southern China. Methods: In total, 54 nonrepetitive CRE strains were collected in pediatric patients at three centers in Guangzhou, Southern China, from January 2016 to August 2018. CRE isolates were used for further studies on antimicrobial susceptibility, the modified Hodge test (MHT), the modified carbapenem inactivation method (mCIM), and drug resistance genes. Multilocus sequence typing (MLST) was used to elucidate the molecular epidemiology of K. pneumoniae. Results: The isolated CRE strains include 34 K. pneumoniae (63.0%), 10 E. coli (18.5%), 4 Enterobacter cloacae (7.4%), and 6 Proteus mirabilis (11.1%) strains. The strains were isolated mainly from the blood (31.5%, n = 17), sputum (31.5%, n = 17), and urine (16.7%, n = 9). All CRE isolates were highly resistant to the third- or fourth-generation cephalosporins, carbapenems, and ß-lactam + ß-lactamase inhibitors (94.4%-96.3%). In addition, the resistance rates to amikacin, ciprofloxacin, levofloxacin, tigecycline, and colistin were 5.6%, 14.8%, 16.7%, 9.3%, and 0%, respectively. Carbapenemase was detected in 35 (64.8%) of the CRE isolates. The most dominant carbapenemase gene was bla NDM (n = 17, 48.6%), followed by bla IMP (n = 13, 37.1%) and bla OXA-23 (n = 4, 11.4%). Other carbapenemase genes (bla KPC, bla sim, bla Aim, bla GES, bla Gim, bla OXA-2 , and bla OXA-48 ) and the mcr-1 gene were not detected. MLST analysis showed high diversity among the K. pneumoniae, and ST45 (11.7%, 4/34) was the dominant sequence type. Conclusion: This study revealed bla NDM was the most dominant carbapenemase gene in children in Guangzhou. Infection control measures need to be taken for the prevention and treatment of CRE infections.

Diagnostic Value of IGFBP-2 in Predicting Preeclampsia before 20 Weeks of Pregnancy: A Prospective Nested Case-Control Study.

Purpose: To identify novel biomarker insulin-like growth factor binding protein-2 (IGFBP-2) associated with preeclampsia (PE) before 20 weeks of gestation and to explore the predictive value of plasma IGFBP-2 in PE. Methods: A prospective nested case-control investigation involving 122 PE patients and 122 normal controls (NC) that were matched 1 : 1 in terms of age and week of pregnancy was carried out in Guangzhou Women and Children's Medical Center (Guangzhou, China, 2018030306) from April 2016 to December 2019. At 8 to 20 weeks, blood samples from the mother were taken. To calculate the correlations, univariate conditional logistic regression was employed. Results: Herein, 12 clinical indices were significantly different between the PE and NC groups (uric acid (UA), cystatin C (Cys C), aspartate aminotransferase (AST), glutamyl transpeptidase (γ-GT), total bilirubin (TB), prothrombin time (PT), red blood cell (RBC), hematocrit (HCT), red cell distribution width (RDW), platelets (PLT), mean platelet volume (MPV), and thrombocytocrit (PCT)). Compared with the NC group (36.79 ± 19.91 pg/mL), the expression level of IGFBP2 in the PE group (19.76 ± 19.40 pg/mL) before 20 weeks of pregnancy was significantly decreased (P < 0.01). Two high-risk factors were found to be significantly associated with PE independently of confounders: anemia 4.35 (2.20-8.45) (P < 0.01) and cesarean section history 8.25 (2.67-26.67) (P < 0.01). As a result of the univariate logistic regression analysis, the following three variables were included in the final logistic regression model.: Y = -18.841 - 0.085 × (IGFBP-2) + 0.630 × (RDW) + 0.165 × (AST) + 0.863 × (MPV). In comparison to IGFBP-2 alone as an independent predictor of PE (AUC = 0.897, 95% CI 0.830-0.964), the model's discriminatory power was considerably higher (AUC = 0.953, 95% CI 0.911-0.995). Conclusion: Plasma IGFBP-2 before 20 weeks of pregnancy combined with high-risk factors and routine blood indexes has a high early predictive value for PE.

Instrument Pointer Recognition Scheme Based on Improved CSL Algorithm.

The traditional pointer instrument recognition scheme is implemented in three steps, which is cumbersome and inefficient. So it is difficult to apply to the industrial production of real-time monitoring. Based on the improvement of the CSL coding method and the setting of the pre-cache mechanism, an intelligent reading recognition technology of the YOLOv5 pointer instrument is proposed in this paper, which realizes the rapid positioning and reading recognition of the pointer instrument. The problem of angle interaction in rotating target detection is eliminated, the complexity of image preprocessing is avoided, and the problems of poor adaptability of Hough detection are solved in this strategy. The experimental results show that compared with the traditional algorithm, the algorithm in this paper can effectively identify the angle of the pointer instrument, has high detection efficiency and strong adaptability, and has broad application prospects.

Simultaneous genotyping for human platelet antigen systems and HLA-A and HLA-B loci by targeted next-generation sequencing.

In order to treat the alloimmunization platelet transfusion refractoriness (PTR), human leukocyte antigen (HLA)-type and/or human platelet antigen (HPA)-type matched platelets between donors and patients are usually used. Therefore, genotyping of HLA-A and HLA-B loci, as well as HPA systems, for donors and patients, is of great significance. However, there is a rare report of genotyping for HLA-A and HLA-B loci as well as HPA systems at the same time. In this study, a high-throughput method for simultaneous genotyping of HLA-A and HLA-B loci, as well as HPA genotyping, was developed. A RNA capture probe panel was designed covering all exon sequences of the GP1BA, GP1BB, ITGA2, CD109, ITGB3, and ITGA2B genes and HLA-A and HLA-B loci. The HLA-A, HLA-B, and 34 HPA systems were genotyped using a targeted next-generation sequencing (NGS) method. The genotypes of the HLA-A and HLA-B loci, as well as the HPA, were assigned based on the nucleotides in the polymorphism sites. Using the NGS method, 204 unrelated blood specimens were successfully genotyped for all 34 HPA systems as well as HLA-A and HLA-B loci. The accuracy of the NGS method was 100%. Only HPA-2, HPA-3, HPA-5, HPA-6w, HPA-15, and HPA-21w showed polymorphism with frequencies of 0.9412, 0.6863, 0.9853, 0.9779, 0.4314, and 0.9951 for a allele, respectively. Thirty-two single nucleotide variants (SNVs) were detected. Of them, 12 SNVs can lead to amino acid change. HLA-A*11:01 and HLA-B*46:01 are the most common alleles for HLA-A and HLA-B loci. A targeted next-generation sequencing method for simultaneously genotyping HPA systems and HLA-A and HLA-B loci was first established, which could be used to create a database of HLA-typed and/or HPA-typed unrelated donors.

Description of two novel HLA alleles: HLA-C*01:02:73 and HLA-C*01:02:75.

Compared with HLA-C*01:02:01:01, the alleles HLA-C*01:02:73 and HLA-C*01:02:75 each show one single nucleotide substitution respectively.

Engineering an oilseed crop for hyper-accumulation of carotenoids in the seeds without using a traditional marker gene.

KEY MESSAGE: Ketocarotenoids were synthesized successfully in Camelina sativa seeds by genetic modification without using a traditional selection marker genes. This method provided an interesting tool for metabolic engineering of seed crops. Camelina sativa (L.) Crantz is an important oil crop with many excellent agronomic traits. This model oil plant has been exploited to accumulate value-added bioproducts using genetic manipulation that depends on antibiotic- or herbicide-based selection marker genes (SMG), one of the major concerns for genetically modified foods. Here we reported metabolic engineering of C. sativa to synthesize red ketocarotenoids that could serve as a reporter to visualize transgenic events without using a traditional SMG. Overexpression of a non-native ß-carotene ketolase gene coupled with three other carotenogenous genes (phytoene synthase, ß-carotene hydroxylase, and Orange) in C. sativa resulted in production of red seeds that were visibly distinguishable from the normal yellow ones. Constitutive expression of the transgenes led to delayed plant development and seed germination. In contrast, seed-specific transformants demonstrated normal growth and seed germination despite the accumulation of up to 70-fold the level of carotenoids in the seeds compared to the controls, including significant amounts of astaxanthin and keto-lutein. As a result, the transgenic seed oils exhibited much higher antioxidant activity. No significant changes were found in the profiles of fatty acids between transgenic and control seeds. This study provided an interesting tool for metabolic engineering of seed crops without using a disputed SMG.

Genomic Basis of Occurrence of Cryptic Resistance among Oxacillin- and Cefoxitin-Susceptible mecA-Positive Staphylococcus aureus.

The oxacillin- and cefoxitin-susceptible mecA-positive Staphylococcus aureus is a novel "stealth" methicillin-resistant S. aureus (MRSA) type. Here, we sequenced the whole genome of two oxacillin- and cefoxitin-susceptible mecA-positive MRSA isolates from breast abscesses in a lactating woman and a nasal swab of a healthy student in Guangzhou for investigating the mechanism underlying its occurrence. The reversion of these isolates was selected by exposure to sub-MICs of cefoxitin with or without mupirocin. The mecA expression of both parental strains and their revertants was determined, and the whole genome of the revertants was sequenced. Comparative whole-genome analyses performed for both strains revealed that mecA of the clinical strain was mutated by a single-bp insertion at the 262nd position in the tandem repeat region of the gene, and this mutation that led to the formation of a premature stop codon. The colonizing strain was mutated by a novel G-to-A base substitution in the second promoter region (-35 bp) of mecA. The mecA expression level of strain 697 revertant was 37 times higher than that of the parental strain. Although the mecA expression level was even higher for parental strain 199 compared with that for its revertant, its cDNA sequence contained a single-bp insertion. Collectively, both the missense and single substitution mutations of the second promoter of mecA could render MRSA isolates as "stealth" MRSA, thereby emphasizing the importance of combining phenotype tests with mecA or penicillin-binding protein 2a detection for the identification of MRSA. IMPORTANCE The oxacillin- and cefoxitin-susceptible mecA-positive Staphylococcus aureus is a novel type of "stealth" methicillin-resistant S. aureus (MRSA), which is difficult to be detected using conventional methods. To investigate the genomic basis of their occurrence, we sequenced the whole genome of two previously recovered oxacillin- and cefoxitin-susceptible mecA-positive MRSA isolates from breast abscesses in a lactating woman and a nasal swab of a healthy student in Guangzhou. Complete SCCmec structure was absent except for mecA in clinical isolate 199. Additionally, a novel single-base pair insertion was observed in the clinical strain, which resulted in premature termination and a frameshift mutation. The colonizing isolate 697 had a Scc-mec-type IVa, and the second promoter region (-35 bp) of mecA was mutated by a novel G-to-A base substitution. The reversion of oxacillin- and cefoxitin-susceptible mecA-positive S. aureus to resistant MRSA isolates was selected by exposure to subminimum inhibitory cefoxitin with or without mupirocin.