Cucumber STACHYOSE SYNTHASE is regulated by its cis-antisense RNA asCsSTS to balance source-sink carbon partitioning.

Photosynthate partitioning between source and sink is a key determinant of crop yield. In contrast to sucrose-transporting plants, cucumber (Cucumis sativus) plants mainly transport stachyose and stachyose synthase (CsSTS) synthesizes stachyose in the vasculature for loading. Therefore, CsSTS is considered a key regulator of carbon partitioning. We found that CsSTS expression and CsSTS enzyme activity were upregulated in the vasculature and downregulated in mesophyll tissues at fruiting. In situ hybridization and tissue enrichment experiments revealed that a cis-natural antisense noncoding transcript of CsSTS, named asCsSTS, is mainly expressed in mesophyll tissues. In vitro overexpression (OE), RNA interference (RNAi), and dual luciferase reporter experiments indicated that CsSTSs are negatively regulated by asCsSTS. Fluorescence in situ hybridization revealed that asCsSTS transcript localized in leaf cytoplasm, indicating that the regulation of CsSTS by asCsSTS is a posttranscriptional process. Further investigation revealed that this regulation occurred by reducing CsSTS transcript stability through a DICER-like protein-mediated pathway. Chemically induced OE and RNAi of asCsSTS led to promotion or inhibition, respectively, of assimilate export from leaves and altered fruit growth rates. Our results suggest that the regulation of CsSTSs between the mesophyll and vasculature reduces sugar storage in mesophyll tissue and promotes assimilate export from the leaf when the plant carries fruit.

Establishment of replication-competent vesicular stomatitis virus recapitulating SADS-CoV entry.

Zoonotic coronaviruses pose a continuous threat to human health, with newly identified bat-borne viruses like swine acute diarrhea syndrome coronavirus (SADS-CoV) causing high mortality in piglets. In vitro studies indicate that SADS-CoV can infect cell lines from diverse species, including humans, highlighting its potential risk to human health. However, the lack of tools to study viral entry, along with the absence of vaccines or antiviral therapies, perpetuates this threat. To address this, we engineered an infectious molecular clone of Vesicular Stomatitis Virus (VSV), replacing its native glycoprotein (G) with SADS-CoV spike (S) and inserting a Venus reporter at the 3' leader region to generate a replication-competent rVSV-Venus-SADS S virus. Serial passages of rVSV-Venus-SADS S led to the identification of an 11-amino-acid truncation in the cytoplasmic tail of the S protein, which allowed more efficient viral propagation due to increased cell membrane anchoring of the S protein. The S protein was integrated into rVSV-Venus-SADS SΔ11 particles, susceptible to neutralization by sera from SADS-CoV S1 protein-immunized rabbits. Additionally, we found that TMPRSS2 promotes SADS-CoV spike-mediated cell entry. Furthermore, we assessed the serum-neutralizing ability of mice vaccinated with rVSV-Venus-SADS SΔ11 using a prime-boost immunization strategy, revealing effective neutralizing antibodies against SADS-CoV infection. In conclusion, we have developed a safe and practical tool for studying SADS-CoV entry and exploring the potential of a recombinant VSV-vectored SADS-CoV vaccine.IMPORTANCEZoonotic coronaviruses, like swine acute diarrhea syndrome coronavirus (SADS-CoV), pose a continual threat to human and animal health. To combat this, we engineered a safe and efficient tool by modifying the Vesicular Stomatitis Virus (VSV), creating a replication-competent rVSV-Venus-SADS S virus. Through serial passages, we optimized the virus for enhanced membrane anchoring, a key factor in viral propagation. This modified virus, rVSV-Venus-SADS SΔ11, proved susceptible to neutralization, opening avenues for potential vaccines. Additionally, our study revealed the role of TMPRSS2 in SADS-CoV entry. Mice vaccinated with rVSV-Venus-SADS SΔ11 developed potent neutralizing antibodies against SADS-CoV. In conclusion, our work presents a secure and practical tool for studying SADS-CoV entry and explores the promise of a recombinant VSV-vectored SADS-CoV vaccine.

Functional and genetic analysis of viral receptor ACE2 orthologs reveals a broad potential host range of SARS-CoV-2.

The pandemic of COVID-19, caused by SARS-CoV-2, is a major global health threat. Epidemiological studies suggest that bats (Rhinolophus affinis) are the natural zoonotic reservoir for SARS-CoV-2. However, the host range of SARS-CoV-2 and intermediate hosts that facilitate its transmission to humans remain unknown. The interaction of coronavirus with its host receptor is a key genetic determinant of host range and cross-species transmission. SARS-CoV-2 uses angiotensin-converting enzyme 2 (ACE2) as the receptor to enter host cells in a species-dependent manner. In this study, we characterized the ability of ACE2 from diverse species to support viral entry. By analyzing the conservation of five residues in two virus-binding hotspots of ACE2 (hotspot 31Lys and hotspot 353Lys), we predicted 80 ACE2 proteins from mammals that could potentially mediate SARS-CoV-2 entry. We chose 48 ACE2 orthologs among them for functional analysis, and showed that 44 of these orthologs-including domestic animals, pets, livestock, and animals commonly found in zoos and aquaria-could bind the SARS-CoV-2 spike protein and support viral entry. In contrast, New World monkey ACE2 orthologs could not bind the SARS-CoV-2 spike protein and support viral entry. We further identified the genetic determinant of New World monkey ACE2 that restricts viral entry using genetic and functional analyses. These findings highlight a potentially broad host tropism of SARS-CoV-2 and suggest that SARS-CoV-2 might be distributed much more widely than previously recognized, underscoring the necessity to monitor susceptible hosts to prevent future outbreaks.

Mutation Y453F in the spike protein of SARS-CoV-2 enhances interaction with the mink ACE2 receptor for host adaption.

COVID-19 patients transmitted SARS-CoV-2 to minks in the Netherlands in April 2020. Subsequently, the mink-associated virus (miSARS-CoV-2) spilled back over into humans. Genetic sequences of the miSARS-CoV-2 identified a new genetic variant known as "Cluster 5" that contained mutations in the spike protein. However, the functional properties of these "Cluster 5" mutations have not been well established. In this study, we found that the Y453F mutation located in the RBD domain of miSARS-CoV-2 is an adaptive mutation that enhances binding to mink ACE2 and other orthologs of Mustela species without compromising, and even enhancing, its ability to utilize human ACE2 as a receptor for entry. Structural analysis suggested that despite the similarity in the overall binding mode of SARS-CoV-2 RBD to human and mink ACE2, Y34 of mink ACE2 was better suited to interact with a Phe rather than a Tyr at position 453 of the viral RBD due to less steric clash and tighter hydrophobic-driven interaction. Additionally, the Y453F spike exhibited resistance to convalescent serum, posing a risk for vaccine development. Thus, our study suggests that since the initial transmission from humans, SARS-CoV-2 evolved to adapt to the mink host, leading to widespread circulation among minks while still retaining its ability to efficiently utilize human ACE2 for entry, thus allowing for transmission of the miSARS-CoV-2 back into humans. These findings underscore the importance of active surveillance of SARS-CoV-2 evolution in Mustela species and other susceptible hosts in order to prevent future outbreaks.

Chromatic confocal sensor-based on-machine measurement for microstructured optical surfaces featuring a self-aligned spiral center.

Chromatic confocal sensor-based on-machine measurement is effective for identifying and compensating for form errors of the ultra-precisely machined components. In this study, an on-machine measurement system was developed for an ultra-precision diamond turning machine to generate microstructured optical surfaces, for which the sensor probe adopts a uniform spiral scanning motion. To avoid the tedious spiral center alignment, a self-alignment method was proposed without additional equipment or artefact, which identified the deviation of the optical axis to the spindle axis by matching the measured surface points and the designed surface. The feasibility of the proposed method was demonstrated by numerical simulation with full consideration of noises and system dynamics. Practically, taking a typical microstructured surface as an example, the on-machine measured points were reconstructed after calibrating the alignment deviation, which was then verified by off-machine white light interferometry measurement. Avoiding tedious operations and special artefacts may significantly simplify the on-machine measurement process, thereby greatly improving the efficiency and flexibility for the measurement.

Evaluation of structural integrity effect on adhesion strength of root dentin with a multi-functional irrigation strategy.

OBJECTIVES: To evaluate effects of a novel auxiliary irrigation strategy, proanthocyanidin (PA) + carboxymethyl chitosan/amorphous calcium phosphate (CMC/ACP) nanocomplexes, on maintaining the organic-inorganic structural integrity and hence optimizing the adhesion strength of root dentin. MATERIALS AND METHODS: Dentin specimens (n = 150) were prepared and subjected to the classical irrigating strategy with or without PA and CMC/ACP. The ultrastructure and biomechanical behaviour of dentin were characterized by scanning electron microscopy and atomic force microscope, respectively. Forty single root-canal premolars were employed for push-out bond strength testing. Besides, the antibacterial effects against Enterococcus faecalis were evaluated with confocal laser scanning microscopy. Statistical differences were verified with one-way ANOVA and Tukey's post-tests. RESULTS: The organic-inorganic structural integrity of root dentin was repaired with the synergetic use of PA and CMC/ACP. Correspondingly, the bond stability between the root canal wall and the AH-Plus sealer was significantly reinforced (P < 0.05). Meanwhile, the tissue biomechanical properties and antibacterial behaviour were enhanced compared to that of control group (P < 0.05). CONCLUSIONS: The synergistic utilization of PA and CMC/ACP can preserve the structural integrity of root dentin, contributing to optimizing the sealing effects of root canal. Moreover, the novel irrigation strategy demonstrated a favourable antimicrobial activity. CLINICAL RELEVANCE: The combination of PA and CMC/ACP can serve as a promising auxiliary irrigation strategy to optimize the outcomes of chemical preparation, enhance the sealing effects of root canal and hence improve the success rate of treatment.

A tight cold-inducible switch built by coupling thermosensitive transcriptional and proteolytic regulatory parts.

Natural organisms have evolved intricate regulatory mechanisms that sense and respond to fluctuating environmental temperatures in a heat- or cold-inducible fashion. Unlike dominant heat-inducible switches, very few cold-inducible genetic switches are available in either natural or engineered systems. Moreover, the available cold-inducible switches still have many shortcomings, including high leaky gene expression, small dynamic range (<10-fold) or broad transition temperature (>10°C). To address these problems, a high-performance cold-inducible switch that can tightly control target gene expression is highly desired. Here, we introduce a tight and fast cold-inducible switch that couples two evolved thermosensitive variants, TFts and TEVts, as well as an additional Mycoplasma florum Lon protease (mf-Lon) to effectively turn-off target gene expression via transcriptional and proteolytic mechanisms. We validated the function of the switch in different culture media and various Escherichia coli strains and demonstrated its tightness by regulating two morphogenetic bacterial genes and expressing three heat-unstable recombinant proteins, respectively. Moreover, the additional protease module enabled the cold-inducible switch to actively remove the pre-existing proteins in slow-growing cells. This work establishes a high-performance cold-inducible system for tight and fast control of gene expression which has great potential for basic research, as well as industrial and biomedical applications.

Contamination characteristics, source analysis and health risk assessment of heavy metals in the soil in Shi River Basin in China based on high density sampling.

To explore the contamination of heavy metals in the Shi River Basin soil in China, a high density sampling of surface soil was conducted. In this study, an absolute principal component scores multiple linear regression model (APCS-MLR) was used to identify the sources of heavy metals in the soil and quantify their amounts. The methods to assess the heavy metals included a fuzzy synthetic evaluation, index and health risk assessment. The results show that heavy metals are relatively rich southwest of the study area. Their levels may be affected by natural sources, such as parent materials. The pollution caused by human factors cannot be ignored, and it is primarily influenced by traffic emissions and processing sources, which contribute 62.6%, followed by agricultural sources, such as pesticides and fertilizers, that contribute 21.1%. The risk assessment indicated that the study area was slightly to moderately polluted. All heavy metals pose higher carcinogenic and other health risks to children than adults, and ingestion is the main way that these pollutants enter the body. The carcinogenic risk of children owing to Cr from natural sources merits further study, while the carcinogenic risk to adults and the non-carcinogenic risk to both adults and children are at acceptable levels. Transportation and industrial processing sources are the main cause of the non-carcinogenic risk. The results could provide reference for reducing heavy metal pollution in the soil.

Galactinol synthase 1 improves cucumber performance under cold stress by enhancing assimilate translocation.

Cucumber (Cucumis sativus L.) predominately translocates raffinose family oligosaccharides (RFOs) in the phloem and accumulates RFOs in leaves. Galactinol synthase (GolS) catalyzes the critical step of RFO biosynthesis, and determining the functional diversity of multiple GolS isoforms in cucumber is of scientific significance. In this study, we found that all four isoforms of CsGolS in the cucumber genome were upregulated by different abiotic stresses. ß-glucuronidase staining and tissue separation experiments suggested that CsGolS1 is expressed in vascular tissues, whereas the other three CsGolSs are located in mesophyll cells. Further investigation indicates that CsGolS1 plays double roles in both assimilate loading and stress response in minor veins, which could increase the RFO concentration in the phloem sap and then improve assimilate transport under adverse conditions. Cold-induced minor vein-specific overexpression of CsGolS1 enhanced the assimilate translocation efficiency and accelerated the growth rates of sink leaves, fruits and whole plants under cold stress. Finally, our results demonstrate a previously unknown response to adverse environments and provide a potential biotechnological strategy to improve the stress resistance of cucumber.