基于密度泛函理论下H_(2)S在单原子催化剂V/Ti_(2)CO_(2)上的分解机理研究

解析工业脱硫气中硫化氢与催化剂的相互作用机制及其分解机理对于开发处理H_(2)S气体的催化剂具有重要意义。本研究采用密度泛函理论计算方法研究了H_(2)S分子在单原子催化剂(SACs,Ti和V原子负载的单层MXene-Ti_(2)CO_(2))表面上的吸附和催化解离行为。分波态密度(PDOS)、电荷分析以及差分电荷密度的结果表明:单原子Ti和V的负载导致了Ti_(2)CO_(2)表面上的电荷进行重新分配,并且显著改善了H_(2)S分子与Ti_(2)CO_(2)之间的相互作用,从而提高SACs的催化活性。为了深入理解硫化氢分子的催化处理过程及其分解机理(H_(2)S→HS^(*)+H^(*)→H2+S^(*)),本研究对硫化氢分子在Ti/Ti_(2)CO_(2)和V/Ti_(2)CO_(2)表面上的分解反应路径进行了对比分析。结果表明:硫化氢分子在被Ti和V负载的Ti_(2)CO_(2)表面上都能够自动解离形成-HS基团和一个质子(HS^(*)/H^(*)),而且在V负载的Ti_(2)CO_(2)的SACs上,整条路径的速率限制步骤所要跨越的能垒低至0.28 eV,该结果表明H_(2)S分子可在室温下能容易地被单原子催化剂V/Ti_(2)CO_(2)解离成H2分子和S原子,而且S原子能够在该催化剂表面团聚形成稳定的单质硫,从而完成催化循环。此外,使用该SACs催化剂分解H_(2)S,相比于已经报道过的其它体系的催化剂,无论是在可持续经济角度还是处理能力方面都有较好的应用前景。综上所述,我们发现V负载的Ti_(2)CO_(2)催化剂能够高效催化分解硫化氢气体。

Density functional theory calculations on single atomic catalysis:Ti-decorated Ti3C2O2 monolayer(MXene)for HCHO oxidation

Formaldehyde(HCHO) is a common indoor pollutant, long-term exposure to HCHO may harm human health. Its efficient removal at mild conditions is still challenging. The catalytic oxidation of HCHO molecules on a single atomic catalyst, Ti-decorated Ti3C2O2(Ti/Ti3C2O2) monolayer, is investigated by performing the first principles calculations in this work. It demonstrates that Ti atoms can be easily well dispersed at the form of single atom on Ti3C2O2 monolayer without aggregation. For HCHO catalytic oxidation, both Langmuir-Hinshelwood(LH) and Eley-Rideal(ER) mechanisms are considered. The results show that the step of HCHO dissociative adsorption on Ti/Ti3C2O2 with activated O2 can release high energy of 4.05 e V based on the ER mechanism, which can help to overcome the energy barrier(1.04 e V) of the subsequent reaction steps. The charge transfer from *OH group to CO molecule(dissociated from HCHO) not only promotes *OH group activation but also plays an important role in the H2 O generation along the ER mechanism. Therefore, HCHO can be oxidized easily on Ti/Ti3C2O2 monolayer, this work could provide significant guidance to develop effective non-noble metal catalysts for HCHO oxidation and broaden the applications of MXene-based materials.

The VAMP-associated protein VAP27-1 plays a crucial role in plant resistance to ER stress by modulating ER–PM contact architecture in Arabidopsis

The endoplasmic reticulum(ER)and the plasma membrane(PM)form ER–PM contact sites(EPCSs)that allow the ER and PM to exchange materials and information.Stress-induced disruption of protein folding triggers ER stress,and the cell initiates the unfolded protein response(UPR)to resist the stress.However,whether EPCSs play a role in ER stress in plants remains unclear.VESICLE-ASSOCIATED MEMBRANE PROTEIN(VAMP)-ASSOCIATED PROTEIN 27-1(VAP27-1)functions in EPCS tethering and is encoded by a family of 10 genes(VAP27-1–10)in Arabidopsis thaliana.Here,we used CRISPR-Cas9-mediated genome editing to obtain a homozygous vap27-1 vap27-3 vap27-4(vap27-1/3/4)triple mutant lacking three of the key VAP27 family members in Arabidopsis.The vap27-1/3/4 mutant exhibits defects in ER–PM connectivity and EPCS architecture,as well as excessive UPR signaling.We further showed that relocation of VAP27-1 to the PM mediates specific VAP27-1-related EPCS remodeling and expansion under ER stress.Moreover,the spatiotemporal dynamics of VAP27-1 at the PM increase ER–PM connectivity and enhance Arabidopsis resistance to ER stress.In addition,we revealed an important role for intracellular calcium homeostasis in the regulation of UPR signaling.Taken together,these results broaden our understanding of the molecular and cellular mechanisms of ER stress and UPR signaling in plants,providing additional clues for improving plant broad-spectrum resistance to different stresses.

An inducible CRISPR activation tool for accelerating plant regeneration

The inducible CRISPR activation(CRISPR-a)system offers unparalleled precision and versatility for regu-lating endogenous genes,making it highly sought after in plant research.In this study,we developed a chem-ically inducible CRISPR-a tool for plants called ER-Tag by combining the LexA-VP16-ER inducible system with the SunTag CRISPR-a system.We systematically compared different induction strategies and achieved high efficiency in target gene activation.We demonstrated that guide RNAs can be multiplexed and pooled for large-scale screening of effective morphogenic genes and gene pairs involved in plant regeneration.Further experiments showed that induced activation of these morphogenic genes can accelerate regenera-tion and improve regeneration efficiency in both eudicot and monocot plants,including alfalfa,woodland strawberry,and sheepgrass.Our study expands the CRISPR toolset in plants and provides a powerful new strategy for studying gene function when constitutive expression is not feasible or ideal.

Applications of CRISPR/Cas genome editing in economically important fruit crops:recent advances and future directions

Fruit crops,consist of climacteric and non-climacteric fruits,are the major sources of nutrients and fiber for human diet.Since 2013,CRISPR/Cas(Clustered Regularly Interspersed Short Palindromic Repeats and CRISPR-Associated Protein)genome editing system has been widely employed in different plants,leading to unprecedented progress in the genetic improvement of many agronomically important fruit crops.Here,we summarize latest advancements in CRISPR/Cas genome editing of fruit crops,including efforts to decipher the mechanisms behind plant development and plant immunity,We also highlight the potential challenges and improvements in the application of genome editing tools to fruit crops,including optimizing the expression of CRISPR/Cas cassette,improving the delivery efficiency of CRISPR/Cas reagents,increasing the specificity of genome editing,and optimizing the transformation and regeneration system.In addition,we propose the perspectives on the application of genome editing in crop breeding especially in fruit crops and highlight the potential challenges.It is worth noting that efforts to manipulate fruit crops with genome editing systems are urgently needed for fruit crops breeding and demonstration.

Density functional theory calculations on 2H-MoS_(2) monolayer for HCHO degradation:Piezoelectric-photocatalytic synergy

Formaldehyde(HCHO)is a common indoor gaseous pollutant,and long-term exposure to it may cause serious damage to the human immune system.Photocatalytic degradation of HCHO is a promising technique.However,most photocatalysts have the disadvantage of rapid recombination of photo-generated electron-hole pairs.In this work,the recombination of photogenerated electron holes was proposed to inhibit through the piezoelectric effect.A two-dimensional(2D)piezoelectric material,2H-MoS_(2),was selected to investigate the catalytic performance for HCHO degradation by the synergy of the piezoelectric and photocatalysis properties.The results show that the piezoelectric effect can induce the polarization in 2H-MoS_(2) and inhibit the recombination of photogenerated electron-hole pairs,thus improving the photogeneration of hydroxyl radicals for HCHO degradation.Therefore,the piezoelectric-photo-catalysis synergistic effect based on density functional theory(DFT)calculation was proposed to elucidate the HCHO degradation performance.This work could provide important guidance for the development of effective catalysts for HCHO degradation and the application of 2D piezoelectric materials.

Designer TAL Effectors Induce Disease Susceptibility and Resistance to Xanthomonas oryzae pv. Oryzae in Rice

TAL （transcription activator-like） effectors from Xanthomonas bacteria activate the cognate host genes, leading to disease susceptibility or resistance dependent on the genetic context of host target genes. The modular nature and DNA recognition code of TAL effectors enable custom-engineering of designer TAL effectors （dTALE） for gene activation. However, the feasibility of dTALEs as transcription activators for gene functional analysis has not been demonstrated. Here, we report the use of dTALEs, as expressed and delivered by the pathogenic Xanthomonas oryzae pv. oryzae （Xoo）, in revealing the new function of two previously identified disease-related genes and the potential of one developmental gene for disease susceptibility in rice/Xoo interactions. The dTALE gene dTALE-xa27, designed to target the susceptible allele of the resistance gene Xa27, elicited a resistant reaction in the otherwise susceptible rice cultivar IR24. Four dTALE genes were made to induce the four annotated Xa27 homologous genes in rice cultivar Nipponbare, but none of the four induced Xa27-1ike genes conferred resistance to the dTALE-containing Xoo strains. A dTALE gene was also generated to activate the recessive resistance gene xa13, an allele of the disease-susceptibility gene Os8N3 （also named Xa13 or OsSWEETll, a member of sucrose efflux transporter SWEET gene family）. The induction of xa13 by the dTALE rendered the resistant rice IRBB13 （xa13/xa13） susceptible to Xoo. Finally, OsSWEET12, an as-yet uncharacterized SWEET gene with no corresponding naturally occurring TAL effector identified, conferred susceptibility to the Xoo strains expressing the corresponding dTALE genes. Our results demonstrate that dTALEs can be delivered through the bacterial secretion system to activate genes of interest for functional analysis in plants.

IiWRKY34 positively regulates yield, lignan biosynthesis and stress tolerance in Isatis indigotica

Yield potential,pharmaceutical compounds production and stress tolerance capacity are 3 classes of traits that determine the quality of medicinal plants.The autotetraploid Isatis indigotica has greater yield,higher bioactive lignan accumulation and enhanced stress tolerance compared with its diploid progenitor.Here we show that the transcription factor IiWRKY34,with higher expression levels in tetraploid than in diploid I.indigotica,has large pleiotropic effects on an array of traits,including biomass growth rates,lignan biosynthesis,as well as salt and drought stress tolerance.Integrated analysis of transcriptome and metabolome profiling demonstrated that IiWRKY34 expression had far-reaching consequences on both primary and secondary metabolism,reprograming carbon flux towards phenylpropanoids,such as lignans and flavonoids.Transcript-metabolite correlation analysis was applied to construct the regulatory network of IiWRKY34 for lignan biosynthesis.One candidate target Ii4CL3,a key rate-limiting enzyme of lignan biosynthesis as indicated in our previous study,has been demonstrated to indeed be activated by IiWRKY34.Collectively,the results indicate that the differentially expressed IiWRKY34 has contributed significantly to the polyploidy vigor of I.indigotica,and manipulation of this gene will facilitate comprehensive improvements of I.indigotica herb.

Application and future perspective of CRISPR/Cas9 genome editing in fruit crops

Fruit crops, including apple, orange, grape,banana, strawberry, watermelon, kiwifruit and tomato, not only provide essential nutrients for human life but also contribute to the major agricultural output and economic growth of many countries and regions in the world. Recent advancements in genome editing provides an unprecedented opportunity for the genetic improvement of these agronomically important fruit crops. Here, we summarize recent reports of applying CRISPR/Cas9 to fruit crops,including efforts to reduce disease susceptibility, change plant architecture or flower morphology, improve fruit quality traits, and increase fruit yield. We discuss challenges facing fruit crops as well as new improvements and platforms that could be used to facilitate genome editing in fruit crops, including d Cas9-base-editing to introduce desirable alleles and heat treatment to increase editing efficiency. In addition, we highlight what we see as potentially revolutionary development ranging from transgene-free genome editing to de novo domestication of wild relatives. Without doubt, we now see only the beginning of what will eventually be possible with the use of the CRISPR/Cas9 toolkit. Efforts to communicate with the public and an emphasis on the manipulation of consumerfriendly traits will be critical to facilitate public acceptance of genetically engineered fruits with this new technology.

Self-assembled PEG-b-PDPA-b-PGEM copolymer nanoparticles as protein antigen delivery vehicles to dendritic cells:preparation,characterization and cellular uptake

Antigen uptake by dendritic cells(DCs)is a key step for initiating antigen-specific T cell immunity.In the present study,novel synthetic polymeric nanoparticles were prepared as antigen delivery vehicles to improve the antigen uptake by DCs.Well-defined cationic and acid-responsive copolymers,monomethoxy poly(ethylene glycol)-block-poly(2-(diisopropyl amino)ethyl methacrylate)-block-poly(2-(guanidyl)ethyl methacrylate)(mPEG-b-PDPA-b-PGEM,PEDG)were synthesized by reversible addition-fragmentation chain transfer polymerization of 2-(diisopropylamino)ethyl methacrylate and N-(tert-butoxycarbonyl)amino ethyl methacrylate monomers,followed by deprotection of tert-butyl protective groups and guanidinylation of obtained primary amines.1H NMR,13C NMR and GPC results indicated the successful synthesis of well-defined PEDG copolymers.PEDG copolymers could self-assemble into nanoparticles in aqueous solution,which were of cationic surface charges and showed acid-triggered disassembly contributed by PGEM and PDPA moieties,respectively.Significantly,PEDG nanoparticles could effectively condense with negatively charged model antigen ovalbumin(OVA)to form OVA/PEDG nanoparticle formulations with no influence on its secondary and tertiary structures demonstrating by far-UV circular dichroism and UV-vis spectra.In vitro antigen cellular uptake by bone marrow DCs(BMDCs)indicated using PEDG nanoparticles as antigen delivery vehicles could significantly improve the antigen uptake efficiency of OVA compared with free OVA or the commercialized Alum adjuvant.Moreover,as the surface cationic charges of OVA/PEDG nanoparticle formulations reduced,the uptake efficiency decreased correspondingly.Collectively,our work suggests that guanidinylated,cationic and acid-responsive PEDG nanoparticles represent a new kind of promising antigen delivery vehicle to DCs and hold great potential to serve as immunoadjuvants in the development of vaccines.

Increased pathogenicity and aerosol transmission for one SARS-CoV-2 B.1.617.2 Delta variant over the wild-type strain in hamsters

During the two-year pandemic of coronavirus disease 2019(COVID-19), its causative agent, severe acute respiratory syndrome coronavirus 2(SARS-CoV-2), has been evolving. SARS-CoV-2 Delta, a variant of concern, has become the dominant circulating strain worldwide within just a few months. Here, we performed a comprehensive analysis of a new B.1.617.2 Delta strain(Delta630) compared with the early WIV04 strain(WIV04) in vitro and in vivo, in terms of replication, infectivity, pathogenicity, and transmission in hamsters. When inoculated intranasally, Delta630 led to more pronounced weight loss and more severe disease in hamsters. Moreover, 40%mortality occurred about one week after infection with 10^(4)PFU of Delta630, whereas no deaths occurred even after infection with 10^(5)PFU of WIV04 or other strains belonging to the Delta variant. Moreover, Delta630outgrew over WIV04 in the competitive aerosol transmission experiment. Taken together, the Delta630 strain showed increased replication ability, pathogenicity, and transmissibility over WIV04 in hamsters. To our knowledge, this is the first SARS-CoV-2 strain that causes death in a hamster model, which could be an asset for the efficacy evaluation of vaccines and antivirals against infections of SARS-CoV-2 Delta strains. The underlying molecular mechanisms of increased virulence and transmission await further analysis.

A potent neutralizing antibody provides protection against SARS-CoV-2 Omicron and Delta variants via nasal delivery

Severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)is still rapidly spreading worldwide.Many drugs and vaccines have been approved for clinical use show efficacy in the treatment and prevention of SARS-CoV-2 infections.However,the emergence of SARS-CoV-2 variants of concern(VOCs),such as Delta(B.1.617.2)and the recently emerged Omicron(B.1.1.529),has seriously challenged the application of current therapeutics.Therefore,there is still a pressing need for identification of new broad-spectrum antivirals.Here,we further characterized a human antibody(58G6),which we previously isolated from a patient,with a broadly authentic virus-neutralizing activity that inhibits the Delta and Omicron variants with half-maximal inhibitory concentrations(ICso)of 1.69 ng/ml and 54.31 ng/ml,respectively.58G6 shows prophylactic and therapeutic effcacy in hamsters challenged with the Delta and Omicron variants through nasal delivery.Notably,a very low dosage(2 mg/kg daily)of 58G6 efficiently prevented Omicron variant replication in the lungs.These advantages may overcome the efficacy limitation of currently approved neutralizing antibodies that can be administered only by intravenous injection.In general,58G6 is a promising prophylactic and therapeutic candidate against current circulating VOCs and even future emerging mutants.To the best of our knowledge,58G6 is one of the most potent neutralizing antibodies against Omicron,with a broader spectrum than those approved for clinical use.58G6 could be developed as a nebulized therapy,which would be more cost effective and user friendly and enhance the clinical outcome comparedto thatobtainedwithdirect nasaldelivery.

Impacts of de-icing salt pollution on urban road greenspace： a case study of Beijing

De-icing salt contamination of urban soil and greenspace has been a common issue of concern in many countries for years. In the 2009/2010 winter, Beijing experienced a contamination accident resulting from the overuse of deicing salt, reported as almost 30000 tons, which severely damaged urban vegetation alongside roadways. The methods of sampling and rating for both soil contamination and response of the plant populations were developed to rapidly assess this emergency environmental event. Results showed that the shrubs were more severely damaged than the arbors in terms of both degree and extent, as almost all of the surveyed shrubs were severely damaged from the salt contamination, while only about 1/4 of the recorded arbors were rated as ＂severely injured＂ according to the integral plant injury index. The rating of the injury level showed that the trees like Pinus bungeana, Sophora japonica, and the shrubs like Euonymus japonicus, Sabina vulgaris showed less tolerance to de-icing salt pollution. The patterns of vegetation damage demonstrated that the ever-green shrubs alongside roads and the deciduous arbors in the center of roads were most vulnerable to the salt damage.