Actinidia chlorotic ringspot‐associated virus: a novel emaravirus infecting kiwifruit plants

By integrating next‐generation sequencing (NGS), bioinformatics, electron microscopy and conventional molecular biology tools, a new virus infecting kiwifruit vines has been identified and characterized. Being associated with double‐membrane‐bound bodies in infected tissues and having a genome composed of RNA segments, each one containing a single open reading frame in negative polarity, this virus shows the typical features of members of the genus Emaravirus. Five genomic RNA segments were identified. Additional molecular signatures in the viral RNAs and in the proteins they encode, together with data from phylogenetic analyses, support the proposal of creating a new species in the genus Emaravirus to classify the novel virus, which is tentatively named Actinidia chlorotic ringspot‐associated virus (AcCRaV). Bioassays showed that AcCRaV is mechanically transmissible to Nicotiana benthamiana plants which, in turn, may develop chlorotic spots and ringspots. Field surveys disclosed the presence of AcCRaV in four different species of kiwifruit vines in five different provinces of central and western China, and support the association of the novel virus with symptoms of leaf chlorotic ringspots in Actinidia. Data on the molecular features of small RNAs of 21–24 nucleotides, derived from AcCRaV RNAs targeted by host RNA silencing mechanisms, are also reported, and possible molecular pathways involved in their biogenesis are discussed.     

NKG2D ligand RAE1ε induces generation and enhances the inhibitor function of myeloid‐derived suppressor cells in mice

Expression of surface NKG2D ligands on tumour cells, which activates nature killer (NK) cells and CD8⁺ T cells, is crucial in antitumour immunity. Some types of tumours have evolved mechanisms to suppress NKG2D‐mediated immune cell activation, such as tumour‐derived soluble NKG2D ligands or sustained NKG2D ligands produced by tumours down‐regulate the expression of NKG2D on NK cells and CD8⁺ T cells. Here, we report that surface NKG2D ligand RAE1ε on tumour cells induces CD11b⁺Gr‐1⁺ myeloid‐derived suppressor cell (MDSC) via NKG2D in vitro and in vivo. MDSCs induced by RAE1ε display a robust induction of IL‐10 and arginase, and these MDSCs show greater suppressive activity by inhibiting antigen‐non‐specific CD8⁺ T‐cell proliferation. Consistently, upon adoptive transfer, MDSCs induced by RAE1ε significantly promote CT26 tumour growth in IL‐10‐ and arginase‐dependent manners. RAE1ε moves cytokine balance towards Th2 but not Th1 in vivo. Furthermore, RAE1ε enhances inhibitory function of CT26‐derived MDSCs and promotes IL‐4 rather than IFN‐γ production from CT26‐derived MDSCs through NKG2D in vitro. Our study has demonstrated a novel mechanism for NKG2D ligand⁺ tumour cells escaping from immunosurveillance by facilitating the proliferation and the inhibitory function of MDSCs.     

The EF‐1α promoter maintains high‐level transgene expression from episomal vectors in transfected CHO‐K1 cells

In our previous study, we demonstrated that episomal vectors based on the characteristic sequence of matrix attachment regions (MARs) and containing the cytomegalovirus (CMV) promoter allow transgenes to be maintained episomally in Chinese hamster ovary (CHO) cells. However, the transgene expression was unstable and the number of copies was low. In this study, we focused on enhancers, various promoters and promoter variants that could improve the transgene expression stability, expression magnitude (level) and the copy number of a MAR‐based episomal vector in CHO‐K1 cells. In comparison with the CMV promoter, the eukaryotic translation elongation factor 1 α (EF‐1α, gene symbol EEF1A1) promoter increased the transfection efficiency, the transgene expression, the proportion of expression‐positive clones and the copy number of the episomal vector in long‐term culture. By contrast, no significant positive effects were observed with an enhancer, CMV promoter variants or CAG promoter in the episomal vector in long‐term culture. Moreover, the high‐expression clones harbouring the EF‐1α promoter tended to be more stable in long‐term culture, even in the absence of selection pressure. According to these findings, we concluded that the EF‐1α promoter is a potent regulatory sequence for episomal vectors because it maintains high transgene expression, transgene stability and copy number. These results provide valuable information on improvement of transgene stability and the copy number of episomal vectors.     

Theoretical insights into the effects of molar ratios on stabilities,mechanical properties,and detonation performance of CL-20/HMX cocrystal explosives by molecular dynamics simulation

To research and estimate the effects of molar ratios on structures, stabilities, mechanical properties, and detonation properties of CL-20/HMX cocrystal explosive, the CL-20/HMX cocrystal explosive models with different molar ratios were established in Materials Studio (MS). The crystal parameters, structures, stabilities, mechanical properties, and some detonation parameters of different cocrystal explosives were obtained and compared. The molecular dynamics (MD) simulation results illustrate that the molar ratios of CL-20/HMX have a direct influence on the comprehensive performance of cocrystal explosive. The hardness and rigidity of the 1:1 cocrystal explosive was the poorest, while the plastic property and ductibility were the best, thus implying that the explosive has the best mechanical properties. Besides, it has the highest binding energy, so the stability and compatibility is the best. The cocrystal explosive has better detonation performance than HMX. In a word, the 1:1 cocrystal explosive is worth more attention and further research. This paper could offer some theoretical instructions and technological support, which could help in the design of the CL-20 cocrystal explosive.     

Comparative analysis of complete chloroplast genome sequences of two subtropical trees, <Emphasis Type="Italic">Phoebe sheareri</Emphasis> and <Emphasis Type="Italic">Phoebe omeiensis</Emphasis> (Lauraceae)

Phoebe is an economically important genus from the family Lauraceae. It is widely distributed in tropical and subtropical Asia, but systematics of the genus is unclear, and currently there is no species-level phylogeny. Here, we determined the complete chloroplast genome sequences of two species with long-range PCR and next genome sequencing technologies, and identified mutation sites and highly variable regions. These highly variable sites were used to reconstruct the phylogeny. The plastomes of Phoebe sheareri and P. omeiensis were 152, 876, and 152, 855 bp, respectively. Comparative genomic analysis indicated that there are 222 mutation sites including 146 substitutions, 73 indels, and 3 microinversions in both plastomes. Fifty-six single-nucleotide changes were identified in gene-coding regions, and 45 microsatellite sites were found for use in species identification. Fourteen divergence hotspots of 38 variable regions were located. Phylogeny was reconstructed using a Bayesian and maximum likelihood approach for 12 Phoebe species and other five related Lauraceae based on 15 of the highly variable regions including accD-psaI, atpB-rbcL, ndhC-trnV, ndhF-rpl32, petA-psbJ, psaA, psbA-trnH, rbcL, rps8-rpl14, rps16-trnQ, rpl32-trnL, trnC-petN, trnL-trnF, trnS-trnG, and ycf1 indicated that variability in the chloroplast regions proposed as variable is enough to detect divergence events among 12 taxa of Phoebe, and that maybe also useful to help to elucidate further relationships among other taxa of the genus.     

Advanced Electro-active Dry Adhesive Actuated by an Artificial Muscle Constructed from an Ionic Polymer Metal Composite Reinforced with Nitrogen-doped Carbon Nanocages

An advanced electro-active dry adhesive,which was composed of a mushroom-shaped fibrillar dry adhesive array actuated by an Ionic Polymer Metal Composite (IPMC) artificial muscle reinforced with nitrogen-doped carbon nanocages (NCNCs),was developed to imitate the actuation of a gecko's toe.The properties of the NCNC-reinforced Nafion membrane,the electromechanical properties of the NCNC-reinforced IPMC,and the related electro-active adhesion ability were investigated.The NCNCs were uniformly dispersed in the 0.1 wt％ NCNC/Nafion membrane,and there was a seamless connection with no clear interface between the dry adhesive and the IPMC.Our 0.1 wt％ NCNC/Nafion-IPMC actuator shows a displacement and force that are 1.6-2 times higher than those of the recast Nafion-IPMC.This is due to the increased water uptake (25.39％) and tensile strength (24.5 MPa) of the specific 3D hollow NCNC-reinforced Nafion membrane,as well as interactions between the NCNCs and the sulfonated groups of the Nafion.The NCNC/Nafion-IPMC was used to effectively actuate the mushroom-shaped dry adhesive.The normal adhesion forces were 7.85 mN,12.1 mN,and 51.7 mN at sinusoidal voltages of 1.5 V,2.5 V,and 3.5 V,respectively,at 0.1 Hz.Under the bionic leg trail,the normal and shear forces were approximately 713.5 mN (159 mN·cm-2) and 1256.6 mN (279 mN·cm-2),respectively,which satisfy the required adhesion.This new electro-active dry adhesive can be applied for active,distributed actuation and flexible grip in robots.