Flux regulation through glycolysis and respiration is balanced by inositol pyrophosphates in yeast.

Although many prokaryotes have glycolysis alternatives, it's considered as the only energy-generating glucose catabolic pathway in eukaryotes. Here, we managed to create a hybrid-glycolysis yeast. Subsequently, we identified an inositol pyrophosphatase encoded by OCA5 that could regulate glycolysis and respiration by adjusting 5-diphosphoinositol 1,2,3,4,6-pentakisphosphate (5-InsP7) levels. 5-InsP7 levels could regulate the expression of genes involved in glycolysis and respiration, representing a global mechanism that could sense ATP levels and regulate central carbon metabolism. The hybrid-glycolysis yeast did not produce ethanol during growth under excess glucose and could produce 2.68 g/L free fatty acids, which is the highest reported production in shake flask of Saccharomyces cerevisiae. This study demonstrated the significance of hybrid-glycolysis yeast and determined Oca5 as an inositol pyrophosphatase controlling the balance between glycolysis and respiration, which may shed light on the role of inositol pyrophosphates in regulating eukaryotic metabolism.

Cas1 mediates the interference stage in a phage-encoded CRISPR-Cas system.

Clustered regularly interspaced short palindromic repeats (CRISPR)-Cas systems are prokaryotic adaptive immune systems against invading phages and other mobile genetic elements. Notably, some phages, including the Vibrio cholerae-infecting ICP1 (International Center for Diarrheal Disease Research, Bangladesh cholera phage 1), harbor CRISPR-Cas systems to counteract host defenses. Nevertheless, ICP1 Cas8f lacks the helical bundle domain essential for recruitment of helicase-nuclease Cas2/3 during target DNA cleavage and how this system accomplishes the interference stage remains unknown. Here, we found that Cas1, a highly conserved component known to exclusively work in the adaptation stage, also mediates the interference stage through connecting Cas2/3 to the DNA-bound CRISPR-associated complex for antiviral defense (Cascade; CRISPR system yersinia, Csy) of the ICP1 CRISPR-Cas system. A series of structures of Csy, Csy-dsDNA (double-stranded DNA), Cas1-Cas2/3 and Csy-dsDNA-Cas1-Cas2/3 complexes reveal the whole process of Cas1-mediated target DNA cleavage by the ICP1 CRISPR-Cas system. Together, these data support an unprecedented model in which Cas1 mediates the interference stage in a phage-encoded CRISPR-Cas system and the study also sheds light on a unique model of primed adaptation.

Structural and functional insights into the chloroplast division site regulators PARC6 and PDV1 in the intermembrane space.

Chloroplast division involves the coordination of protein complexes from the stroma to the cytosol. The Min system of chloroplasts includes multiple stromal proteins that regulate the positioning of the division site. The outer envelope protein PLASTID DIVISION1 (PDV1) was previously reported to recruit the cytosolic chloroplast division protein ACCUMULATION AND REPLICATION OF CHLOROPLAST5 (ARC5). However, we show here that PDV1 is also important for the stability of the inner envelope chloroplast division protein PARALOG OF ARC6 (PARC6), a component of the Min system. We solved the structure of both the C-terminal domain of PARC6 and its complex with the C terminus of PDV1. The formation of an intramolecular disulfide bond within PARC6 under oxidized conditions prevents its interaction with PDV1. Interestingly, this disulfide bond can be reduced by light in planta, thus promoting PDV1-PARC6 interaction and chloroplast division. Interaction with PDV1 can induce the dimerization of PARC6, which is important for chloroplast division. Magnesium ions, whose concentration in chloroplasts increases upon light exposure, also promote the PARC6 dimerization. This study highlights the multilayer regulation of the PDV1-PARC6 interaction as well as chloroplast division.

Imparting Chemiresistor with Humidity-Independent Sensitivity toward Trace-Level Formaldehyde via Substitutional Doping Platinum Single Atom.

The modification of metal oxides with noble metals is one of the most effective means of improving gas-sensing performance of chemiresistors, but it is often accompanied by unintended side effects such as sensor resistance increases up to unmeasurable levels. Herein, a carbonization-oxidation method is demonstrated using ultrasonic spray pyrolysis technique to realize platinum (Pt) single atom (SA) substitutional doping into SnO2 (named PtSA-SnO2). The substitutional doping strategy can obviously enhance gas-sensing properties, and meanwhile decrease sensor resistance by two orders of magnitude (decreased from ≈850 to ≈2 MΩ), which are attributed to the tuning of band gap and fermi-level position, efficient single atom catalysis, and the raising of adsorption capability of formaldehyde, as validated by the state-of-the-art characterizations, such as spherical aberration-corrected scanning transmission electron microscopy (Cs-corrected STEM), in situ diffuse reflectance infrared Fourier transformed spectra (in situ DRIFT), CO temperature-programmed reduction (CO-TPR), and theoretical calculations. As a proof of concept, the developed PtSA-SnO2 sensor shows humidity-independent (30-70% relative humidity) gas-sensing performance in the selective detection of formaldehyde with high response, distinguishable selectivity (8< Sformaldehyde/Sinterferant <14), and ultra-low detection limit (10 ppb). This work presents a generalized and facile method to design high-performance metal oxides for chemical sensing of volatile organic compounds (VOCs).

Integrated analysis of miRNA-mRNA expression of newly emerging swine H3N2 influenza virus cross-species infection with tree shrews.

BACKGROUND: Cross-species transmission of zoonotic IAVs to humans is potentially widespread and lethal, posing a great threat to human health, and their cross-species transmission mechanism has attracted much attention. miRNAs have been shown to be involved in the regulation of IAVs infection and immunity, however, few studies have focused on the molecular mechanisms underlying miRNAs and mRNAs expression after IAVs cross-species infection. METHODS: We used tree shrews, a close relative of primates, as a model and used RNA-Seq and bioinformatics tools to analyze the expression profiles of DEMs and DEGs in the nasal turbinate tissue at different time points after the newly emerged swine influenza A virus SW2783 cross-species infection with tree shrews, and miRNA-mRNA interaction maps were constructed and verified by RT-qPCR, miRNA transfection and luciferase reporter assay. RESULTS: 14 DEMs were screened based on functional analysis and interaction map, miR-760-3p, miR-449b-2, miR-30e-3p, and miR-429 were involved in the signal transduction process of replication and proliferation after infection, miR-324-3p, miR-1301-1, miR-103-1, miR-134-5p, miR-29a, miR-31, miR-16b, miR-34a, and miR-125b participate in negative feedback regulation of genes related to the immune function of the body to activate the antiviral immune response, and miR-106b-3p may be related to the cross-species infection potential of SW2783, and the expression level of these miRNAs varies in different days after infection. CONCLUSIONS: The miRNA regulatory networks were constructed and 14 DEMs were identified, some of them can affect the replication and proliferation of viruses by regulating signal transduction, while others can play an antiviral role by regulating the immune response. It indicates that abnormal expression of miRNAs plays a crucial role in the regulation of cross-species IAVs infection, which lays a solid foundation for further exploration of the molecular regulatory mechanism of miRNAs in IAVs cross-species infection and anti-influenza virus targets.

Structural basis of ubiquitin modification by the Legionella effector SdeA.

Protein ubiquitination is a multifaceted post-translational modification that controls almost every process in eukaryotic cells. Recently, the Legionella effector SdeA was reported to mediate a unique phosphoribosyl-linked ubiquitination through successive modifications of the Arg42 of ubiquitin (Ub) by its mono-ADP-ribosyltransferase (mART) and phosphodiesterase (PDE) domains. However, the mechanisms of SdeA-mediated Ub modification and phosphoribosyl-linked ubiquitination remain unknown. Here we report the structures of SdeA in its ligand-free, Ub-bound and Ub-NADH-bound states. The structures reveal that the mART and PDE domains of SdeA form a catalytic domain over its C-terminal region. Upon Ub binding, the canonical ADP-ribosyltransferase toxin turn-turn (ARTT) and phosphate-nicotinamide (PN) loops in the mART domain of SdeA undergo marked conformational changes. The Ub Arg72 might act as a 'probe' that interacts with the mART domain first, and then movements may occur in the side chains of Arg72 and Arg42 during the ADP-ribosylation of Ub. Our study reveals the mechanism of SdeA-mediated Ub modification and provides a framework for further investigations into the phosphoribosyl-linked ubiquitination process.

Multiplexed CRISPR-Based Nucleic Acid Detection Using a Single Cas Protein.

Thanks to its ease, speed, and sensitivity, CRISPR-based nucleic acid detection has been increasingly explored for molecular diagnostics. However, one of its major limitations is lack of multiplexing capability because the detection relies on the trans-cleavage activity of the Cas protein, which necessitates the use of multiple orthogonal Cas proteins for multiplex detection. Here we report the development of a multiplexed CRISPR-based nucleic acid detection system with single-nucleotide resolution using a single Cas protein (Cas12a). This method, termed as CRISPR-TMSD, integrates the toehold-mediated strand displacement (TMSD) reaction, and the cis-cleavage activity of the Cas protein and multiplexed detection are achieved using a single Cas protein owing to the use of target-specific reporters. A set of computational simulation toolkits was used to design the TMSD reporter, allowing for highly sensitive and specific identification of target sequences. In combination with the recombinase polymerase amplification (RPA), the detection limit can reach as low as 1 copy/µL. As proof of concept, CRISPR-TMSD was subsequently used to detect an oncogenic gene and SARS-CoV-2 RNA with a single-nucleotide resolution. This work represents a conceptually new strategy for designing a CRISPR-based diagnostic system and has great potential to expand the application of CRISPR-based diagnostics.

Simultaneous Regulation of Solvation Shell and Oriented Deposition toward a Highly Reversible Fe Anode for All-Iron Flow Batteries.

Developing low-cost all-iron hybrid redox flow batteries (RFBs) presents a practical alternative to the high-cost all-vanadium RFBs and is deemed vital for grid-scale energy storage applications. However, the intrinsically poor Fe anode reversibility associated with the deposition and dissolution of metallic iron greatly limits the cycling performance and long-term stability of all-iron hybrid RFBs. Herein, a highly reversible and dendrite-free Fe anode is reported for all-iron RFBs through regulation of polar solvent dimethyl sulfoxide (DMSO) on FeCl2 anolyte, which simultaneously reshapes Fe2+ solvation structure and induces controllable oriented Fe deposition. Combining both experimental and theoretical analyses, the polar DMSO additives prove effective in replacing H2 O molecule from the primary solvation shell of Fe2+ cation via the Fe2+ -O (DMSO) bond and meanwhile induces a fine-grained Fe nucleation on the preferred Fe (110) plane, which are responsible for the minimized hydrogen evolution and dendrite-free Fe deposition that significantly enhance Fe anode reversibility. The all-iron RFB based on the proposed FeCl2 -DMSO anolyte demonstrates an excellent combination of peak power density of 134 mW cm-2 , high energy efficiency of 75% at 30 mA cm-2 , and high capacity retention of 98.6% over 200 cycles, which presents the best performance of all-iron RFBs among previously reported research.

Concise Biosynthesis of Tropone-Containing Spiromaterpenes by a Sesquiterpene Cyclase and a Multifunctional P450 from a Deep-Sea-Derived Spiromastix sp. Fungus.

Spiromaterpenes are a group of rare tropone-containing sesquiterpenes with antineuroinflammatory activity. Herein, we elucidate their biosynthetic pathway in a deep-sea-derived Spiromastix sp. fungus by heterologous expression, biochemical characterization, and incubation experiments. The sesquiterpene cyclase SptA was first characterized to catalyze the production of guaia-1(5),6-diene, and a multifunctional cytochrome P450 catalyzed the tropone ring formation. These results provide important clues for the rational mining of bioactive guaiane-type sesquiterpenes and expand the repertoire of P450 activities to synthesize unique building blocks of natural products.

Versatile biomanufacturing through stimulus-responsive cell-material feedback.

Small-scale production of biologics has great potential for enhancing the accessibility of biomanufacturing. By exploiting cell-material feedback, we have designed a concise platform to achieve versatile production, analysis and purification of diverse proteins and protein complexes. The core of our technology is a microbial swarmbot, which consists of a stimulus-sensitive polymeric microcapsule encapsulating engineered bacteria. By sensing the confinement, the bacteria undergo programmed partial lysis at a high local density. Conversely, the encapsulating material shrinks responding to the changing chemical environment caused by cell growth, squeezing out the protein products released by bacterial lysis. This platform is then integrated with downstream modules to enable quantification of enzymatic kinetics, purification of diverse proteins, quantitative control of protein interactions and assembly of functional protein complexes and multienzyme metabolic pathways. Our work demonstrates the use of the cell-material feedback to engineer a modular and flexible platform with sophisticated yet well-defined programmed functions.

Production of ß-carotene in Saccharomyces cerevisiae through altering yeast lipid metabolism.

Saccharomyces cerevisiae is a widely used cell factory for the production of fuels and chemicals. However, as a non-oleaginous yeast, S. cerevisiae has a limited production capacity for lipophilic compounds, such as ß-carotene. To increase its accumulation of ß-carotene, we engineered different lipid metabolic pathways in a ß-carotene producing strain and investigated the relationship between lipid components and the accumulation of ß-carotene. We found that overexpression of sterol ester synthesis genes ARE1 and ARE2 increased ß-carotene yield by 1.5-fold. Deletion of phosphatidate phosphatase (PAP) genes (PAH1, DPP1, and LPP1) also increased ß-carotene yield by twofold. Combining these two strategies resulted in a 2.4-fold improvement in ß-carotene production compared with the starting strain. These results demonstrated that regulating lipid metabolism pathways is important for ß-carotene accumulation in S. cerevisiae, and may also shed insights to the accumulation of other lipophilic compounds in yeast.

Characterization of cross-species transcription and splicing from Penicillium to Saccharomyces cerevisiae.

Heterologous expression of eukaryotic gene clusters in yeast has been widely used for producing high-value chemicals and bioactive secondary metabolites. However, eukaryotic transcription cis-elements are still undercharacterized, and the cross-species expression mechanism remains poorly understood. Here we used the whole expression unit (including original promoter, terminator, and open reading frame with introns) of orotidine 5'-monophosphate decarboxylases from 14 Penicillium species as a showcase, and analyzed their cross-species expression in Saccharomyces cerevisiae. We found that pyrG promoters from the Penicillium species could drive URA3 expression in yeast, and that inefficient cross-species splicing of Penicillium introns might result in weak cross-species expression. Thus, this study demonstrates cross-species expression from Penicillium to yeast, and sheds light on the opportunities and challenges of cross-species expression of fungi expression units and gene clusters in yeast without refactoring for novel natural product discovery.

Expressing a cytosolic pyruvate dehydrogenase complex to increase free fatty acid production in Saccharomyces cerevisiae.

BACKGROUND: Saccharomyces cerevisiae is being exploited as a cell factory to produce fatty acids and their derivatives as biofuels. Previous studies found that both precursor supply and fatty acid metabolism deregulation are essential for enhanced fatty acid synthesis. A bacterial pyruvate dehydrogenase (PDH) complex expressed in the yeast cytosol was reported to enable production of cytosolic acetyl-CoA with lower energy cost and no toxic intermediate. RESULTS: Overexpression of the PDH complex significantly increased cell growth, ethanol consumption and reduced glycerol accumulation. Furthermore, to optimize the redox imbalance in production of fatty acids from glucose, two endogenous NAD+-dependent glycerol-3-phosphate dehydrogenases were deleted, and a heterologous NADP+-dependent glyceraldehyde-3-phosphate dehydrogenase was introduced. The best fatty acid producing strain PDH7 with engineering of precursor and co-factor metabolism could produce 840.5 mg/L free fatty acids (FFAs) in shake flask, which was 83.2% higher than the control strain YJZ08. Profile analysis of free fatty acid suggested the cytosolic PDH complex mainly resulted in the increases of unsaturated fatty acids (C16:1 and C18:1). CONCLUSIONS: We demonstrated that cytosolic PDH pathway enabled more efficient acetyl-CoA provision with the lower ATP cost, and improved FFA production. Together with engineering of the redox factor rebalance, the cytosolic PDH pathway could achieve high level of FFA production at similar levels of other best acetyl-CoA producing pathways.

Simultaneous separation and determination of seven chelating agents using high-performance liquid chromatography based on statistics design.

We describe an optimization approach to determine simultaneously occurring chelating agents (glycine, malonic acid, citric acid, glycolic acid, lactic acid, DL-malic acid, and ethylenediaminetetraacetic acid) in an electroplating effluent using high-performance liquid chromatography. With chromatography signal area and overall resolution considered as responses, detection conditions were optimized via multiple functions combined with response surface methodology and Plackett-Burman design. Optimized detection conditions were as follows: 15 mmol/L ammonium phosphate buffer (pH 2.5), a 94:6 v/v ratio of ammonium phosphate buffer/acetonitrile, a column temperature of 23.3°C, and a mobile phase flow rate of 1 mL/min. The experimental values conformed to the predicted values and were repeatable (relative standard deviation < 6.4%) and linear (r2  > 0.991) over concentration ranges of 1-100 µmol/L. Moreover, the quantification limit (signal-to-noise ratio = 10) and the detection limit (signal-to-noise ratio = 3) ranged from 0.03 to 0.15 µmol/L and from 0.01 to 0.04 µmol/L, respectively. These results indicate that high-performance liquid chromatography coupled with statistical design may be a simple and rapid method for simultaneously determining multiple chelating agents in electroplating wastewater effectively.

Synthetic Biology of Yeast.

With the rapid development of DNA synthesis and next-generation sequencing, synthetic biology that aims to standardize, modularize, and innovate cellular functions, has achieved vast progress. Here we review key advances in synthetic biology of the yeast Saccharomyces cerevisiae, which serves as an important eukaryal model organism and widely applied cell factory. This covers the development of new building blocks, i.e., promoters, terminators and enzymes, pathway engineering, tools developments, and gene circuits utilization. We will also summarize impacts of synthetic biology on both basic and applied biology, and end with further directions for advancing synthetic biology in yeast.

Crystal structure of the multifunctional SAM-dependent enzyme LepI provides insights into its catalytic mechanism.

Pericyclic reactions are among the most powerful synthetic transformations widely applied in the synthesis of multiple regioselective and stereoselective carbon-carbon bonds. LepI is a recently identified S-adenosyl-l-methionine (SAM)-dependent enzyme, which could catalyze dehydration, Diels-Alder reaction, and the retro-Claisen rearrangement reactions. However, the mechanism underlying these reactions by LepI remains elusive. Here we report the structure of LepI in complex with SAM as its co-factor, which adopts a typical class I methyltransferase fold. Docking studies are performed to investigate the binding modes of various substrates/products and provide insights into the catalytic mechanism of the multiple reactions catalyzed by LepI. Our study suggests that the dehydration reaction may start from the deprotonation of the hydroxyl group on the pyridone ring of the substrate by LepIH133, during which R295 and D296 play important roles in substrate binding and stabilizing the reaction intermediate. The stereoselective dehydration is accomplished through the trans-conformer of the leaving alcohol group which is trapped by nearby residues. The pericyclic reactions following dehydration are facilitated by the hydrophobic and hydrophilic interactions in the binding pocket. H133 and R295, two residues not conserved in other methyltransferases, might account for the unique activity of LepI among the SAM-dependent methyltransferase family. Together, this study provides important structural insights into the unique reactions catalyzed by LepI and will shed light on the knowledge of mechanisms of pericyclic reactions.

Hydrogen Alleviates Necroptosis and Cognitive Deficits in Lithium-Pilocarpine Model of Status Epilepticus.

Status epilepticus without prompt seizure control always leads to neuronal death and long-term cognitive deficits, but effective intervention is still absent. Here, we found that hydrogen could alleviate the hippocampus-dependent spatial learning and memory deficit in lithium-pilocarpine model of status epilepticus in rats, as evidenced by the results in Morris water maze test. Hydrogen treatment downregulated the expression of necroptosis-related proteins, such as MLKL, phosphorylated-MLKL, and RIPK3 in hippocampus, and further protected neurons and astrocytes from necroptosis which was here first verified to occur in status epilepticus. Hydrogen also protected cells from apoptosis, which was indicated by the decreased cleaved-Caspase 3 expression. Meanwhile, Iba1+ microglial activation by status epilepticus was reduced by hydrogen treatment. These findings confirm the utility of hydrogen treatment in averting cell death including necroptosis and alleviating cognitive deficits caused by status epilepticus. Therefore, hydrogen may provide a potential and powerful clinical treatment for status epilepticus-related cognitive deficits.

Twin-primer non-enzymatic DNA assembly: an efficient and accurate multi-part DNA assembly method.

DNA assembly forms the cornerstone of modern synthetic biology. Despite the numerous available methods, scarless multi-fragment assembly of large plasmids remains challenging. Furthermore, the upcoming wave in molecular biological automation demands a rethinking of how we perform DNA assembly. To streamline automation workflow and minimize operator intervention, a non-enzymatic assembly method is highly desirable. Here, we report the optimization and operationalization of a process called Twin-Primer Assembly (TPA), which is a method to assemble polymerase chain reaction-amplified fragments into a plasmid without the use of enzymes. TPA is capable of assembling a 7 kb plasmid from 10 fragments at ∼80% fidelity and a 31 kb plasmid from five fragments at ∼50% fidelity. TPA cloning is scarless and sequence independent. Even without the use of enzymes, the performance of TPA is on par with some of the best in vitro assembly methods currently available. TPA should be an invaluable addition to a synthetic biologist's toolbox.

Metabolic engineering of Saccharomyces cerevisiae for production of fatty acid-derived hydrocarbons.

Fatty acid-derived hydrocarbons attract increasing attention as biofuels due to their immiscibility with water, high-energy content, low freezing point, and high compatibility with existing refineries and end-user infrastructures. Yeast Saccharomyces cerevisiae has advantages for production of fatty acid-derived hydrocarbons as its native routes toward fatty acid synthesis involve only a few reactions that allow more efficient conversion of carbon substrates. Here we describe major biosynthetic pathways of fatty acid-derived hydrocarbons in yeast, and summarize key metabolic engineering strategies, including enhancing precursor supply, eliminating competing pathways, and expressing heterologous pathways. With recent advances in yeast production of fatty acid-derived hydrocarbons, our review identifies key research challenges and opportunities for future optimization, and concludes with perspectives and outlooks for further research directions.

Microfluidic screening and whole-genome sequencing identifies mutations associated with improved protein secretion by yeast.

There is an increasing demand for biotech-based production of recombinant proteins for use as pharmaceuticals in the food and feed industry and in industrial applications. Yeast Saccharomyces cerevisiae is among preferred cell factories for recombinant protein production, and there is increasing interest in improving its protein secretion capacity. Due to the complexity of the secretory machinery in eukaryotic cells, it is difficult to apply rational engineering for construction of improved strains. Here we used high-throughput microfluidics for the screening of yeast libraries, generated by UV mutagenesis. Several screening and sorting rounds resulted in the selection of eight yeast clones with significantly improved secretion of recombinant α-amylase. Efficient secretion was genetically stable in the selected clones. We performed whole-genome sequencing of the eight clones and identified 330 mutations in total. Gene ontology analysis of mutated genes revealed many biological processes, including some that have not been identified before in the context of protein secretion. Mutated genes identified in this study can be potentially used for reverse metabolic engineering, with the objective to construct efficient cell factories for protein secretion. The combined use of microfluidics screening and whole-genome sequencing to map the mutations associated with the improved phenotype can easily be adapted for other products and cell types to identify novel engineering targets, and this approach could broadly facilitate design of novel cell factories.