Chromosome Doubling Enhances Biomass and Carotenoid Content in Lycium chinense.

Lycium chinense, a type of medicinal and edible plant, is rich in bioactive compounds beneficial to human health. In order to meet the market requirements for the yield and quality of L. chinense, polyploid induction is usually an effective way to increase plant biomass and improve the content of bioactive components. This study established the most effective tetraploid induction protocol by assessing various preculture durations, colchicine concentrations, and exposure times. The peak tetraploid induction efficacy, 18.2%, was achieved with a 12-day preculture and 24-h exposure to 50 mg L-1 colchicine. Compared to diploids, tetraploids exhibited potentially advantageous characteristics such as larger leaves, more robust stems, and faster growth rates. Physiologically, tetraploids demonstrated increased stomatal size and chloroplast count in stomata but reduced stomatal density. Nutrient analysis revealed a substantial increase in polysaccharides, calcium, iron, and zinc in tetraploid leaves. In addition, seventeen carotenoids were identified in the leaves of L. chinense. Compared to the diploid, lutein, ß-carotene, neoxanthin, violaxanthin, and (E/Z)-phytoene exhibited higher levels in tetraploid strains T39 and T1, with T39 demonstrating a greater accumulation than T1. The findings suggest that the generated tetraploids harbor potential for further exploitation and lay the foundation for the selection and breeding of novel genetic resources of Lycium.

Genome-wide analysis of the TIFY family in Lycium and the negative regulation of stomatal development by LrJAZ2 gene.

Stomata are ports that facilitate gas and water vapor exchange during plant photosynthesis and transpiration. Stomatal development is strictly regulated by endogenous hormone. Jasmonate, an important signal that modulates multiple physiological processes in plants, has been found to negatively regulate stomatal development in Arabidopsis thaliana, yet the molecular mechanisms underlying stomata development signaling remain to be understood. Jasmonate ZIM-domain (JAZ) proteins are the members of TIFY family and the key component of JA signaling pathway. Its function in stomatal development is unclear to data. Here, we screened out 24 TIFY family members against the genome of Lycium, and identified a JAZ member by combination analyses of evolutionary tree, cis-elements in promoter and gene expression patterns. Overexpression of this gene (LrJAZ2) in Lycium ruthenicum and Arabidopsis thaliana indicated LrJAZ2 negatively regulates stomatal development. Microscopic observations revealed that overexpression of LrJAZ2 negatively regulated stomatal development by decreasing stomatal density and index, which may lead to lower leaf transpiration rates. Transcriptome data indicated the overexpression of LrJAZ2 up-regulated the stomatal related genes such as LrERL2, LrPYL4, and down-regulated the LrSPCH. Collectively, our study found that LrJAZ2 is a key gene in stomatal development regulation in L. ruthenicum and provided new insights into the regulation of stomatal development.

Chromosomal-level genome and multi-omics dataset provides new insights into leaf pigmentation in Acer palmatum.

Acer palmatum (A. palmatum), a deciduous shrub or small arbour which belongs to Acer of Aceraceae, is an excellent greening species as well as a beautiful ornamental plant. In this study, a high-quality chromosome-level reference genome for A. palmatum was constructed using Oxford Nanopore sequencing and Hi-C technology. The assembly genome was ∼745.78 Mb long with a contig N50 length of 3.20 Mb, and 95.30 % (710.71 Mb) of the assembly was anchored into 13 pseudochromosomes. A total of 28,559 protein-coding genes were obtained, ∼90.02 % (25,710) of which could be functionally annotated. The genomic evolutionary analysis revealed that A. palmatum is most closely related to A. yangbiense and A. truncatum, and underwent only an ancient gamma whole-genome duplication event. Despite lacking a recent independent WGD, 25,795 (90.32 %) genes of A. palmatum were duplicated, and the unique/expanded gene families were linked with genes involved in plant-pathogen interaction and several metabolic pathways, which might underpin adaptability. A combined genomic, transcriptomic, and metabolomic analysis related to the biosynthesis of anthocyanin in leaves during the different season were characterized. The results indicate that the dark-purple colouration of the leaves in spring was caused by a high amount of anthocyanins, especially delphinidin and its derivatives; and the red colouration of the leaves in autumn by a high amount of cyanidin 3-O-glucoside. In conclusion, these valuable multi-omic resources offer important foundations to explore the molecular regulation mechanism in leaf colouration and also provide a platform for the scientific and efficient utilization of A. palmatum.

The JASMONATE ZIM-domain-OPEN STOMATA1 cascade integrates jasmonic acid and abscisic acid signaling to regulate drought tolerance by mediating stomatal closure in poplar.

Drought, which directly affects the yield of crops and trees, is a natural stress with a profound impact on the economy. Improving water use efficiency (WUE) and drought tolerance are relatively effective strategies to alleviate drought stress. OPEN STOMATA1 (OST1), at the core of abscisic acid (ABA) signaling, can improve WUE by regulating stomatal closure and photosynthesis. Methyl jasmonate (MeJA) and ABA crosstalk is considered to be involved in the response to drought stress, but the detailed molecular mechanism is insufficiently known. Here, Populus euphratica, which naturally grows in arid and semiarid regions, was selected as the species for studying MeJA and ABA crosstalk under drought. A yeast two-hybrid assay was performed using PeOST1 as bait and a nucleus-localized factor, JASMONATE ZIM-domain protein 2 (PeJAZ2), was found to participate in MeJA signaling by interacting with PeOST1. Overexpression of PeJAZ2 in poplar notably increased water deficit tolerance and WUE in both severe and mild drought stress by regulating ABA signaling rather than ABA synthesis. Furthermore, a PeJAZ2 overexpression line was shown to have greater ABA-induced stomatal closure and hydrogen peroxide (H2O2) production. Collectively, this evidence establishes a mechanism in which PeJAZ2 acts as a positive regulator in response to drought stress via ABA-induced stomatal closure caused by H2O2 production. Our study presents a new insight into the crosstalk of ABA and jasmonic acid signaling in regulating WUE and drought stress, providing a basis of the drought tolerance mechanism of P. euphratica.

Cell-Free DNA Promotes Inflammation in Patients With Oral Lichen Planus via the STING Pathway.

Background: Damaged and dead cells release cell-free DNA (cfDNA) that activates cyclic GMP-AMP (cGAMP) synthase (cGAS), which leads to the activation of stimulator of interferon genes (STING) via the second messenger cGAMP. STING promotes the production of inflammatory cytokines and type I interferons to induce an inflammatory response. Oral lichen planus (OLP), a chronic autoimmune disease involving oral mucosa characterized by the apoptosis of keratinocytes mediated by T-lymphocytes, is related to the activation of multiple inflammatory signaling pathways. Currently, the relationship between cfDNA and OLP has not been confirmed. We hypothesized that cfDNA may be a potential therapeutic target for OLP. Methods: cfDNA was extracted from the saliva and plasma of OLP patients; its concentration was measured using the Quanti-iT-PicoGree kit and its relationship with OLP inflammation was assessed. cfDNA of OLP patients (cfDNA-OLP) was transfected into THP-1 macrophages and the expression of inflammatory factors was investigated by performing quantitative real time PCR (qRT-PCR), western blotting, and enzyme-linked immunosorbent assay (ELISA). STING expression was analyzed in the tissues of OLP patients and healthy controls using immunohistochemical staining and western blotting. siRNA was used to knockdown STING expression in THP-1 macrophages, and the inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) secreted by cells following cfDNA-OLP transfection were detected using ELISA. Finally, the effect of the cationic polymer PAMAM-G3 was evaluated on the treatment of inflammation induced by cfDNA-OLP. Results: The concentration of cfDNA in the saliva and plasma of OLP patients was considerably higher than that of healthy controls, and it positively correlated with the levels of inflammatory cytokines and clinical characteristics. cfDNA-OLP induced an inflammatory response in THP-1 macrophages. STING expression was significantly higher in OLP tissues than in the gingival tissues of healthy controls. STING knockdown suppressed cfDNA-OLP-induced inflammation in THP-1 macrophages. PAMAM-G3 inhibited the inflammatory response caused by cfDNA-OLP. Conclusion: The cfDNA level is increased in OLP patients, and the STING pathway activated by cfDNA-OLP might play a critical role in OLP pathogenesis. Treatment with PAMAM-G3 reduced the inflammation induced by cfDNA-OLP, and therefore, may be a potential treatment strategy for OLP.

Combined Analysis of MicroRNAs and Target Genes Revealed miR156-SPLs and miR172-AP2 Are Involved in a Delayed Flowering Phenomenon After Chromosome Doubling in Black Goji (Lycium ruthencium).

Polyploidy, which is widely distributed in angiosperms, presents extremely valuable commercial applications in plant growth and reproduction. The flower development process of higher plants is essential for genetic improvement. Nevertheless, the reproduction difference between polyploidy and the polyploid florescence regulatory network from the perspective of microRNA (miRNA) remains to be elucidated. In this study, the autotetraploid of Lycium ruthenicum showed late-flowering traits compared with the progenitor. Combining the association of miRNA and next-generation transcriptome technology, the late-flowering characteristics triggered by chromosome duplication may be caused by the age pathway involved in miR156-SPLs and miR172-AP2, which inhibits the messenger RNA (mRNA) transcripts of FT in the leaves. Subsequently, FT was transferred to the shoot apical meristem (SAM) to inhibit the expression of the flowering integration factor SOC1, which can eventually result in delayed flowering time. Our exploration of the flowering regulation network and the control of the flowering time are vital to the goji producing in the late frost area, which provides a new perspective for exploring the intrinsic molecular mechanism of polyploid and the reproductive development of flowering plants.

Biosafety, Nontoxic Nanoparticles for VL-NIR Photothermal Therapy Against Oral Squamous Cell Carcinoma.

Semiconductor nanocrystals with extraordinary physicochemical and biosafety properties with unique nanostructures have shown tremendous potential as photothermal therapy (PTT) nanosensitizers. Herein, we successfully synthesized chiral molybdenum (Cys-MoO3-x ) nanoparticles (NPs) for overcoming the general limitation on electron energy bands and biotoxicity. The obtained Cys-MoO3-x NPs are selected as an ideal design for the treatment of oral squamous cell carcinoma (OSCC) cells through the decoration of cysteine molecules due to excellent initial photothermal spectral analysis of conductivity and light absorbance. Notably, NPs possess the ability to act as visible light (VL) and near-infrared (NIR) double-reactive agents to ablate cancer cells. By combining photoconductive PTT with hypotoxicity biochemotherapy, the treatment validity of OSCC cancer cells can be improved in vitro by up to 89% (808 nm) and get potential PTT effect under VL irradiation, which intuitively proved that the nontoxic NPs were lethally effective for cancer cells under laser irradiation. Hence, this work highlights a powerful and safe NP platform for NIR light-triggered PTT for use in head and neck cancer (HNC) cells, showing promising application prospects in oral tumor treatment.

Cryo-EM of mammalian PA28αß-iCP immunoproteasome reveals a distinct mechanism of proteasome activation by PA28αß.

The proteasome activator PA28αß affects MHC class I antigen presentation by associating with immunoproteasome core particles (iCPs). However, due to the lack of a mammalian PA28αß-iCP structure, how PA28αß regulates proteasome remains elusive. Here we present the complete architectures of the mammalian PA28αß-iCP immunoproteasome and free iCP at near atomic-resolution by cryo-EM, and determine the spatial arrangement between PA28αß and iCP through XL-MS. Our structures reveal a slight leaning of PA28αß towards the α3-α4 side of iCP, disturbing the allosteric network of the gatekeeper α2/3/4 subunits, resulting in a partial open iCP gate. We find that the binding and activation mechanism of iCP by PA28αß is distinct from those of constitutive CP by the homoheptameric TbPA26 or PfPA28. Our study sheds lights on the mechanism of enzymatic activity stimulation of immunoproteasome and suggests that PA28αß-iCP has experienced profound remodeling during evolution to achieve its current level of function in immune response.

Metabolic profiling and gene expression analysis provides insights into flavonoid and anthocyanin metabolism in poplar.

Poplar, a woody perennial model, is a common and widespread tree genus. We cultivated two red leaf poplar varieties from bud mutation of Populus sp. Linn. '2025' (also known as Zhonglin 2025, L2025 for shot): Populus deltoides varieties with bright red leaves (LHY) and completely red leaves (QHY). After measuring total contents of flavonoid, anthocyanin, chlorophyll and carotenoid metabolites, a liquid chromatography-electrospray ionization-tandem mass spectrometry system was used for the relative quantification of widely targeted metabolites in leaves of three poplar varieties. A total of 210 flavonoid metabolites (89 flavones, 40 flavonols, 25 flavanones, 18 anthocyanins, 16 isoflavones, 7 dihydroflavonols, 7 chalcones, 5 proanthocyanidins and 3 other flavonoid metabolites) were identified. Compared with L2025, 48 and 8 flavonoids were more and less abundant, respectively, in LHY, whereas 51 and 9 flavonoids were more and less abundant in QHY, respectively. On the basis of a comprehensive analysis of the metabolic network, gene expression levels were analyzed by deep sequencing to screen for potential reference genes for the red leaves. Most phenylpropanoid biosynthesis pathway-involved genes were differentially expressed among the examined varieties. Gene expression analysis also revealed several potential anthocyanin biosynthesis regulators including three MYB genes. The study results provide new insights into poplar flavonoid metabolites and represent the theoretical basis for future studies on leaf coloration in this model tree species.

Effects of pyrolysis temperature on soil-plant-microbe responses to Solidago canadensis L.-derived biochar in coastal saline-alkali soil.

Because salinity of coastal soils is drastically increasing, the application of biochars to saline-alkali soil amendments has attracted considerable attention. Various Solidago-canadensis-L.-derived biochars prepared through pyrolysis from 400 to 600 °C were applied to coastal saline-alkali soil samples to optimise the biochar pyrolysis temperature and investigate its actual ecological responses. All biochars reduced the soil bulk density and exchangeable sodium stress and increased soil water-holding capacity, cation exchange capacity, and organic matter content. Principal-component-analysis results showed that pyrolysis temperature played an important role in the potential application of biochars to improve the coastal saline-alkali soil, mainly contributed to ameliorating exchangeable sodium stress and decreasing biochar-soluble toxic compounds. Furthermore, soil bulk density and organic matter, as well as carboxylic acids, phenolic acids and amines of biochar were major driving factors for bacterial community composition. Compared to low-temperature biochar (pyrolyzed below 550 °C), which showed higher toxicity for Brassica chinensis L. growth due to the higher content of carboxylic acids, phenols and amines, high-temperature biochar (pyrolyzed at or above 550 °C) possessed less amounts of these toxic functional groups, more beneficial soil bacteria and healthier for plant growth. Therefore, high-temperature biochar could be applied as an effective soil amendment to ameliorate the coastal saline-alkali soil with acceptable environmental risk.

Chromosome doubling mediates superior drought tolerance in Lycium ruthenicum via abscisic acid signaling.

Plants are continuously affected by unfavorable external stimuli, which influences their productivity and growth. Differences in gene composition and expression patterns lead homologous polyploid plants to exhibit different physiological phenomena, among which enhanced environmental adaptability is a powerful phenotype conferred by polyploidization. The mechanisms underlying the differences in stress tolerance between diploids and autotetraploids at the molecular level remain unclear. In this research, a full-length transcription profile obtained via the single-molecule real-time (SMRT) sequencing of high-quality single RNA molecules for use as background was combined with next-generation transcriptome and proteome technologies to probe the variation in the molecular mechanisms of autotetraploids. Tetraploids exhibited an increase in ABA content of 78.4% under natural conditions and a superior stress-resistance phenotype under severe drought stress compared with diploids. The substantial differences in the transcriptome profiles observed between diploids and autotetraploids under normal growth conditions were mainly related to ABA biosynthesis and signal transduction pathways, and 9-cis-epoxycarotenoid dioxygenase 1 (NCED1) and NCED2, which encode key synthetic enzymes, were significantly upregulated. The increased expression of the ABRE-binding factor 5-like (ABF5-like) gene was a pivotal factor in promoting the activation of the ABA signaling pathway and downstream target genes. In addition, ABA strongly induced the expression of osmotic proteins to increase the stress tolerance of the plants at the translational level. We consider the intrinsic mechanisms by which ABA affects drought resistance in tetraploids and diploids to understand the physiological and molecular mechanisms that enhance abiotic stress tolerance in polyploid plants.

Remediation of cadmium-contaminated soil with biochar simultaneously improves biochar's recalcitrance.

Biochar sequesters cadmium (Cd) by immobilisation, but the process is often less effective in field trials than in the laboratory. Therefore, the involvement of soil components should be considered for predicting field conditions that could potentially improve this process. Here, we used biochar derived from Spartina alterniflora as the amendment for Cd-contaminated soil. In simulation trials, a mixture of kaolin, a representative soil model component, and S. alterniflora-derived biochar immobilised Cd by forming silicon-aluminium-Cd-containing complexes. Interestingly, the biochar recalcitrance index value increased from 48% to 53%-56% because of the formation of physical barriers consisting of kaolinite minerals and Cd complexes. Pot trials were performed using Brassica chinensis for evaluating the effect of S. alterniflora-derived biochar on plant growth in Cd-contaminated soil. The bio-concentration factor values in B. chinensis were 24%-31% after soil remediation with biochar than in control plants. In summary, these results indicated that soil minerals facilitated Cd sequestration by biochar, which reduced Cd bioavailability and improved the recalcitrance of this soil amendment. Thus, mechanisms for effective Cd remediation should include biochar-soil interactions.

Potassium Transporter LrKUP8 Is Essential for K+ Preservation in Lycium ruthenicum, A Salt-Resistant Desert Shrub.

Salt stress is a major constraint for many crops and trees. A wild species of Goji named Lycium ruthenicum is an important economic halophyte in China and has an extremely high tolerance to salinity. L. ruthenicum grows in saline soil and is known as a potash-rich species. However, its salt adaptation strategies and ion balance mechanism remains poorly understood. Potassium (K+) is one of the essential macronutrients for plant growth and development. In this study, a putative salt stress-responsive gene encoding a HAK (high-affinity K+)/KUP (K+ uptake)/KT (K+ transporter) transporter was cloned and designated as LrKUP8. This gene belongs to the cluster II group of the KT/HAK/KUP family. The expression of LrKUP8 was strongly induced under high NaCl concentrations. The OE-LrKUP8 calli grew significantly better than the vector control calli under salt stress conditions. Further estimation by ion content and micro-electrode ion flux indicated a relative weaker K+ efflux in the OE-LrKUP8 calli than in the control. Thus, a key gene involved in K+ uptake under salt condition was functionally characterized using a newly established L. ruthenicum callus transformation system. The importance of K+ regulation in L. ruthenicum under salt tolerance was highlighted.

Quantitative Structure-Toxicity Relationship analysis of combined toxic effects of lignocellulose-derived inhibitors on bioethanol production.

This study performed a Quantitative Structure-Toxicity Relationship (QSTR) model to evaluate the combined toxicity of lignocellulose-derived inhibitors on bioethanol production. Compared with all the control groups, the combined systems exhibited lower conductivity values, higher oxidation-reduction potential values, as well as maximum inhibition rates. These results indicated that the presence of combined inhibitors had a negative effect on the bioethanol fermentation process. Meanwhile, QSTR model was excellent for evaluating the combined toxic effects at lower ferulic acid concentration (([1:4] × IC50)) and (([1:1] × IC50)), due to higher R2 values (0.994 and 0.762), lower P values (0.000 and 0.023) and relative error values (less than 30%). The obtained results also showed that the combined toxic effects of ferulic acid and representative lignocellulose-derived inhibitors were relevant to different molecular descriptors. Meanwhile, the interactions of combined inhibitors were weaker when ferulic acid was at low concentration ([1:4] × IC50).

Induction, identification and characterization of tetraploidy in Lycium ruthenicum.

Lycium ruthenicum of Solanaceae was widely used as healthy vegetables and natural medicine foods for containing numerous functional components in leaves, roots and fruits. In the present study, tetraploid plants of L. ruthenicum were obtained efficiently by treating their leaves with colchicine in vitro. The highest induction frequency of the tetraploids was 31.4%, which was obtained by preculturing the leaves for 10 days and then treating them with 100 mg/L of colchicine concentration for 48 h. The ploidy levels of the regenerated plants were determined by flow cytometry and chromosome counting methods. Cytological, morphological, and histological characterization validated the results of flow cytometry, revealing the differences between the two kinds of ploidy plants in their tissue culture stage and field production stages. Morphological indexes also provide a simple and intuitionistic method for distinguishing tetraploid from diploid plants. As the chromosome number increased, the stomatal size and number of the chloroplasts in the stomata also increased, but the stomatal density decreased. The results indicate that the chromosome number is correlated with the stomatal index. The generated tetraploid is a potentially useful cultivated variety and will be beneficial for producing triploid progeny in the future.

Recombinant virus-like particle presenting a newly identified coxsackievirus A10 neutralization epitope induces protective immunity in mice.

Coxsackievirus A10 (CVA10) has emerged as one of the major pathogens of hand, foot, and mouth disease in recent years. However, there are no approved vaccines or effective drugs against CVA10. Several experimental CVA10 vaccines have been shown to elicit neutralizing antibodies that could confer protection against viral infection. However, neutralizing antigenic sites on CVA10 capsid have not been well characterized. Here, we report the characterization of linear neutralization epitopes of CVA10 and the development of a CVA10 vaccine based on the identified epitopes. We showed that peptide VP2-P28, corresponding to residues 136 to 150 of VP2, were recognized by anti-inactivated CVA10 sera and effectively inhibited anti-CVA10 sera-mediated neutralization, suggesting that this peptide contains neutralizing epitopes. Insertion of VP2-P28 into hepatitis B core antigen (HBc) resulted in a chimeric virus-like particle (VLP; designated HBc-P28) with the CVA10 epitope exposed on the particle surface. HBc-P28 VLP elicited strong antibody responses against VP2-P28 in mice. Anti-HBc-P28 sera could neutralize both CVA10 clinical isolates and prototype strain, consistent with the fact that the VP2-P28 sequence is highly conserved among CVA10 strains. In addition, anti-HBc-P28 sera failed to cross-neutralize other HFMD-causing enteroviruses, indicating that neutralizing antibodies elicited by HBc-P28 VLP were CVA10-specific. Importantly, anti-HBc-P28 sera were able to provide efficient protection against lethal CVA10 infection in recipient mice. Collectively, these data show that peptide VP2-P28 represents a CVA10-specific linear neutralizing antigenic site and chimeric VLP displaying this peptide is a promising epitope-based CVA10 vaccine candidate.

Coxsackievirus A10 atomic structure facilitating the discovery of a broad-spectrum inhibitor against human enteroviruses.

Coxsackievirus A10 (CV-A10) belongs to the Enterovirus species A and is a causative agent of hand, foot, and mouth disease. Here we present cryo-EM structures of CV-A10 mature virion and native empty particle (NEP) at 2.84 and 3.12 Å, respectively. Our CV-A10 mature virion structure reveals a density corresponding to a lipidic pocket factor of 18 carbon atoms in the hydrophobic pocket formed within viral protein 1. By structure-guided high-throughput drug screening and subsequent verification in cell-based infection-inhibition assays, we identified four compounds that inhibited CV-A10 infection in vitro. These compounds represent a new class of anti-enteroviral drug leads. Notably, one of the compounds, ICA135, also exerted broad-spectrum inhibitory effects on a number of representative viruses from all four species (A-D) of human enteroviruses. Our findings should facilitate the development of broadly effective drugs and vaccines for enterovirus infections.

A study of cadmium remediation and mechanisms: Improvements in the stability of walnut shell-derived biochar.

Biochar has been recognized as an efficient soil amendment for cadmium remediation in recent years. In the present study, biochar was prepared using walnut shell, and it was incubated in Cd(NO3)2 and kaolin for 15 days. Different chemical forms of cadmium in kaolin and biochar were determined, and the stability of biochar was evaluated by R50 using TGA analysis. It was found that walnut shell derived biochar could reduce the mobility of cadmium. After incubation, the R50, biochar value increased from 61.31% to 69.57%-72.24%, indicating that the stability of biochar was improved. The mechanisms that initiated improvements in biochar stability were investigated by XPS, XRD and SEM-EDS analysis. The result showed that the enhanced biochar stability is likely due to physical isolation and the formation of precipitates and complexes, formed on the surface or interior of the biochar. The results suggested that walnut shell-derived biochar can be used as a cadmium sorbent for soil remediation.

Structure, Immunogenicity, and Protective Mechanism of an Engineered Enterovirus 71-Like Particle Vaccine Mimicking 80S Empty Capsid.

Enterovirus 71 (EV71) is the major causative agent of severe hand, foot, and mouth disease, which affects millions of young children in the Asia-Pacific region annually. In this study, we engineered a novel EV71 virus-like particle (VLP) that lacks VP4 (therefore designated VLPΔVP4) and investigated its structure, antigenicity, and vaccine potential. The cryo-electron microscopy (cryo-EM) structure of VLPΔVP4 was reconstructed to 3.71-Å resolution. Results from structural and biochemical analyses revealed that VLPΔVP4 resembles the end product of the viral uncoating process, the 80S empty capsid. VLPΔVP4 is able to elicit high-titer neutralizing antibodies and to fully protect mice against lethal viral challenge. Mechanistic studies showed that, at the cellular level, the anti-VLPΔVP4 sera exert neutralization effects at both pre- and postattachment stages by inhibiting both virus attachment and internalization, and at the molecular level, the antisera can block multiple interactions between EV71 and its key receptors. Our study gives a better understanding of EV71 capsid assembly and provides important information for the design and development of new-generation vaccines for EV71, and perhaps for other enteroviruses, as well.IMPORTANCE Enterovirus 71 (EV71) infection may lead to severe hand, foot, and mouth disease, with significant morbidity and mortality. Knowledge regarding EV71 particle assembly remains limited. Here, we report the generation and characterization of a novel EV71 virus-like particle that lacks the VP4 capsid subunit protein. This particle, termed VLPΔVP4, structurally mimics the 80S empty capsid, which is the end stage of EV71 uncoating. We further show that VLPΔVP4 exhibits desirable immunogenicity and protective efficacy in proof-of-concept studies. In addition, the inhibitory mechanisms of the VLPΔVP4-induced antibodies are unraveled at both the cellular and molecular levels. Our work provides the first evidence of picornaviral particle assembly in the complete absence of VP4 and identifies VLPΔVP4 as an improved EV71 vaccine candidate with desirable traits. These findings not only enhance our understanding of particle assembly and uncoating of picornaviruses, but also provide important information for structure-guided vaccine design for EV71 and other enteroviruses.