Human Intestinal Allografts Contain Functional Hematopoietic Stem and Progenitor Cells that Are Maintained by a Circulating Pool

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Heterologous expression of <Emphasis Type="Italic">Shigella dysenteriae</Emphasis> serotype 1 O-antigen analog in <Emphasis Type="Italic">Escherichia coli</Emphasis> K-12 W3110 by transferring a minimum number of genes involved in O-polysaccharide biosynthesis

Objective

To heterologously produce the Shigella dysenteriae serotype 1 O-polysaccharide (O-PS, O-antigen) in Escherichia coli by transferring the minimum number of genes instead of the entire O-PS gene cluster.

Results

The three glycosyltransferase genes (rfbR, rfbQ and rfp) responsible for the formation of the O-repeat unit were introduced into E. coli K-12 W3110 to synthesize S. dysenteriae 1 O-PS. The specific O-antigen ladder type with different chain lengths of O-repeat units was observed in the recombinant E. coli strain by SDS-PAGE silver staining and western blotting using S. dysenteriae 1 lipopolysaccharide antiserum. Analysis by mass spectrometry and ion chromatography suggested generation of the specific S. dysenteriae 1 O-repeat unit structure with an extra glucose residue attached.

Conclusions

Recombinant E. coli expressing specific glycosyltransferase genes can generate the O-PS of S. dysenteriae 1 and might be able to synthesize heterologous O-antigens of various pathogenic bacteria for vaccine preparation.

     

Identification and expression pattern analysis of the glucosinolate biosynthetic gene <Emphasis Type="Italic">BoCYP83B1</Emphasis> from broccoli

Glucosinolates are a branch of amino acid-derived metabolites, which are specifically found in Brassicales. In Arabidopsis, tryptophan derived indolic glucosinolates are required for plant defense against a wide range of pathogens and herbivores due to their strong antimicrobial activity and potential signaling function. An important enzyme in indolic glucosinolate biosynthesis pathway is CYP83B1, which oxidizes indole-3-acetaldoxime, a precursor of indole-3-acetic acid (IAA). In this study, we reported isolation and expression characterization of a CYP83B1 gene from Brassica oleracea L. var. italica Plenck, which we termed BoCYP83B1. Overexpression of BoCYP83B1 in Arabidopsis resulted in an altered glucosinolate profile and early flowering phenotype. By expressing the reporter gene β-glucuronidase under the control of the BoCYP83B1 promoter in Arabidopsis, we analyzed the spatial expression pattern of BoCYP83B1 under normal growth conditions as well as in response to several hormones and stresses. The BoCYP83B1 was primarily expressed in vascular tissue through the almost whole plant. It was strongly induced by methyl jasmonate, 1-amino-1-cyclopropanecarboxylic acid, salicylic acid (SA), gibberellin, and IAA, suggesting its involvement in complex signaling pathways. Mannitol, NaCl, UV, and Flagelin 22 significantly up-regulated BoCYP83B1 expression, indicating its possible role in stress response. Interestingly, the response of BoCYP83B1 to SA and NaCl showed tissue specificity. Thus, BoCYP83B1 might have different functions in different tissues.     

Development of <Emphasis Type="Italic">mazF</Emphasis>-based markerless genome editing system and metabolic pathway engineering in <Emphasis Type="Italic">Candida tropicalis</Emphasis> for producing long-chain dicarboxylic acids

Candida tropicalis can grow with alkanes or plant oils as the sole carbon source, and its industrial application thus has great potential. However, the choice of a suitable genetic operating system can effectively increase the speed of metabolic engineering. MazF functions as an mRNA interferase that preferentially cleaves single-stranded mRNAs at ACA sequences to inhibit protein synthesis, leading to cell growth arrest. Here, we constructed a suicide plasmid named pPICPJ-mazF that uses the mazF gene of Escherichia coli as a counterselectable marker for the markerless editing of C. tropicalis genes to increase the rate of conversion of oils into long-chain dicarboxylic acids. To reduce the β-oxidation of fatty acids, the carnitine acetyltransferase gene (CART) was deleted using the gene editing system, and the yield of long-chain acids from the strain was increased to 8.27 g/L. By two homologous single exchanges, the promoters of both the cytochrome P450 gene and the NADPH–cytochrome P450 reductase gene were subsequently replaced by the constitutively expressed promoter pGAP, and the production of long-chain dicarboxylic acids by the generated strain (C. tropicalis PJPP1702) reached 11.39 g/L. The results of fed-batch fermentation showed that the yield of long-chain acids from the strain was further increased to 32.84 g/L, which was 11.4 times higher than that from the original strain. The results also showed that the pPICPJ-mazF-based markerless editing system may be more suited for completing the genetic editing of C. tropicalis.     

g‐C3N4‐Based Heterostructured Photocatalysts

Photocatalysis is considered as one of the promising routes to solve the energy and environmental crises by utilizing solar energy. Graphitic carbon nitride (g‐C₃N₄) has attracted worldwide attention due to its visible‐light activity, facile synthesis from low‐cost materials, chemical stability, and unique layered structure. However, the pure g‐C₃N₄ photocatalyst still suffers from its low separation efficiency of photogenerated charge carriers, which results in unsatisfactory photocatalytic activity. Recently, g‐C₃N₄‐based heterostructures have become research hotspots for their greatly enhanced charge carrier separation efficiency and photocatalytic performance. According to the different transfer mechanisms of photogenerated charge carriers between g‐C₃N₄ and the coupled components, the g‐C₃N₄‐based heterostructured photocatalysts can be divided into the following categories: g‐C₃N₄‐based conventional type II heterojunction, g‐C₃N₄‐based Z‐scheme heterojunction, g‐C₃N₄‐based p–n heterojunction, g‐C₃N₄/metal heterostructure, and g‐C₃N₄/carbon heterostructure. This review summarizes the recent significant progress on the design of g‐C₃N₄‐based heterostructured photocatalysts and their special separation/transfer mechanisms of photogenerated charge carriers. Moreover, their applications in environmental and energy fields, e.g., water splitting, carbon dioxide reduction, and degradation of pollutants, are also reviewed. Finally, some concluding remarks and perspectives on the challenges and opportunities for exploring advanced g‐C₃N₄‐based heterostructured photocatalysts are presented.     

Orientation Regulation of Phenylethylammonium Cation Based 2D Perovskite Solar Cell with Efficiency Higher Than 11%

Increasing the power conversion efficiency (PCE) of the two‐dimensional (2D) perovskite‐based solar cells (PVSCs) is really a challenge. Vertical orientation of the 2D perovskite film is an efficient strategy to elevate the PCE. In this work, vertically orientated highly crystalline 2D (PEA)₂(MA)_n–1Pb_nI_3n+1 (PEA= phenylethylammonium, MA = methylammonium, n = 3, 4, 5) films are fabricated with the assistance of an ammonium thiocyanate (NH₄SCN) additive by a one‐step spin‐coating method. Planar‐structured PVSCs with the device structure of indium tin oxide (ITO)/poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate)/(PEA)₂(MA)_n–1Pb_nI_3n+1/[6,6]‐phenyl‐C61‐butyric acid methyl ester/bahocuproine/Ag are fabricated. The PCE of the PVSCs is boosted from the original 0.56% (without NH₄SCN) to 11.01% with the optimized NH₄SCN addition at n = 5, which is among the highest PCE values for the low‐n (n < 10) 2D perovskite‐based PVSCs. The improved performance is attributed to the vertically orientated highly crystalline 2D perovskite thin films as well as the balanced electron/hole transportation. The humidity stability of this oriented 2D perovskite thin film is also confirmed by the almost unchanged X‐ray diffraction patterns after 28 d exposed to the moisture in a humidity‐controlled cabinet (H_r = 55 ± 5%). The unsealed device retains 78.5% of its original PCE after 160 h storage in air atmosphere with humidity of 55 ± 5%. The results provide an effective approach toward a highly efficient and stable PVSC for future commercialization.     

Paleogene fossil fruits of Stephania (Menispermaceae) from North America and East Asia

Stephania Loureiro is a large genus within Menispermaceae, with approximately 60 extant species naturally distributed in tropical to subtropical areas in Asia and Africa, and a few in Oceania. This genus possesses highly characteristic endocarps that facilitate identification of extant and fossil specimens. Here, we report some well-preserved fossil fruits of Stephania from North America and East Asia. The specimens indicate the endocarps were bony or woody with an obovate to obovate-rotund outline and a horseshoe-shaped locule. The endocarp length varies from 4.7 to 8.3 mm, and width from 3.7 to 7.0 mm. The endocarp has a clear foramen in the central area and is surrounded by a keel with ribs running along the dorsal surface. Only one lateral crest develops on each side of the endocarp. Two new species are recognized: Stephania wilfii Han & Manchester sp. nov. from the Paleocene to Eocene of Wyoming (USA), and Stephania jacquesii Han & Manchester sp. nov. disjunct between the late Eocene of Oregon (USA) and the late Oligocene of Guangxi Province (China). In addition, on the basis of more detailed morphological comparative analyses, we transfer the fossils formerly treated as Diploclisia auriformis (Hollick) Manchester from the early Eocene of London Clay, and the middle Eocene of Alaska and Oregon to Stephania auriformis (Hollick) Han & Manchester comb. nov. These fossil materials indicate a broader biogeographic distribution for the ancestors of extant Stephania lineages. This finding enhances our knowledge of the taxonomic and morphological diversity of Stephania and provides new evidence concerning its phytogeographic history.