Synergistic enhancement of plant growth and cadmium stress defense by Azospirillum brasilense and plant heme: Modulating the growth-defense relationship.

Plant growth-promoting rhizobacteria (PGPR) play important roles in plant growth and defense under heavy metal (HM) stress. The direct integration of microbial and plant signals is key to the regulation of plant growth and HM stress defense, but the underlying mechanisms are still limited. Herein, we reveal a novel mechanism by which PGPR regulates plant growth-regulating substances in plant tissues and coordinates plant growth and defense in pak choi under cadmium (Cd) stress. This might be an efficient strategy and an extension of the mechanism by which plant-microbe interactions improve plant stress resistance. Azospirillum brasilense and heme synergistically reduced the shoot Cd content and promoted the growth of pak choi. The interaction between abscisic acid of microbial origin and heme improved Cd stress tolerance through enhancing Cd accumulation in the root cell wall. The interaction between A. brasilense and heme induced the growth-defense shift in plants under Cd stress. Plants sacrifice growth to enhance Cd stress defense, which then transforms into a dual promotion of both growth and defense. This study deepens our understanding of plant-microbe interactions and provides a novel strategy to improve plant growth and defense under HM stress, ensuring future food production and security.

Arbuscular mycorrhizal fungal interactions bridge the support of root-associated microbiota for slope multifunctionality in an erosion-prone ecosystem.

The role of diverse soil microbiota in restoring erosion-induced degraded lands is well recognized. Yet, the facilitative interactions among symbiotic arbuscular mycorrhizal (AM) fungi, rhizobia, and heterotrophic bacteria, which underpin multiple functions in eroded ecosystems, remain unclear. Here, we utilized quantitative microbiota profiling and ecological network analyses to explore the interplay between the diversity and biotic associations of root-associated microbiota and multifunctionality across an eroded slope of a Robinia pseudoacacia plantation on the Loess Plateau. We found explicit variations in slope multifunctionality across different slope positions, associated with shifts in limiting resources, including soil phosphorus (P) and moisture. To cope with P limitation, AM fungi were recruited by R. pseudoacacia, assuming pivotal roles as keystones and connectors within cross-kingdom networks. Furthermore, AM fungi facilitated the assembly and composition of bacterial and rhizobial communities, collectively driving slope multifunctionality. The symbiotic association among R. pseudoacacia, AM fungi, and rhizobia promoted slope multifunctionality through enhanced decomposition of recalcitrant compounds, improved P mineralization potential, and optimized microbial metabolism. Overall, our findings highlight the crucial role of AM fungal-centered microbiota associated with R. pseudoacacia in functional delivery within eroded landscapes, providing valuable insights for the sustainable restoration of degraded ecosystems in erosion-prone regions.

A meta-analysis on crop growth and heavy metals accumulation with PGPB inoculation in contaminated soils.

Plant growth-promoting bacteria (PGPB) offer a promising solution for mitigating heavy metals (HMs) stress in crops, yet the mechanisms underlying the way they operate in the soil-plant system are not fully understood. We therefore conducted a meta-analysis with 2037 observations to quantitatively evaluate the effects and determinants of PGPB inoculation on crop growth and HMs accumulation in contaminated soils. We found that inoculation increased shoot and root biomass of all five crops (rice, maize, wheat, soybean, and sorghum) and decreased metal accumulation in rice and wheat shoots together with wheat roots. Key factors driving inoculation efficiency included soil organic matter (SOM) and the addition of exogenous fertilizers (N, P, and K). The phylum Proteobacteria was identified as the keystone taxa in effectively alleviating HMs stress in crops. More antioxidant enzyme activity, photosynthetic pigment, and nutrient absorption were induced by it. Overall, using PGPB inoculation improved the growth performance of all five crops, significantly increasing crop biomass in shoots, roots, and grains by 33 %, 35 %, and 20 %, respectively, while concurrently significantly decreasing heavy metal accumulation by 16 %, 9 %, and 37 %, respectively. These results are vital to grasping the benefits of PGPB and its future application in enhancing crop resistance to HMs.

Meta-analysis of impacts of microplastics on plant heavy metal(loid) accumulation.

The co-occurrence of microplastics (MPs) and heavy metal(loid)s (HMs) has attracted growing scientific interest because of their wide distribution and environmental toxicity. Nevertheless, the interactions between MPs and HMs in soil-plant systems remain unclear. We conducted a meta-analysis with 3226 observations from 87 independent studies to quantify the impact of MPs addition on the plant biomass and HMS accumulation. Co-occurrence of MPs and HMs (except for As) induced synergistic toxicity to plant growth. MPs promoted their uptake in the shoot by 11.0% for Cd, 30.0% for Pb, and 47.1% for Cu, respectively. In contrast, MPs caused a significant decrease (22.6%, 17.9-26.9%) in the shoot As accumulation. The type and dose of MPs were correlated with the accumulation of HMs. MPs increased available concentrations of Cd, Pb, and Cu, but decreased available As concentration in soils. Meanwhile, MPs addition significantly lowered soil pH. These findings may provide explanations for MPs-mediated effects on influencing the accumulation of HMs in plants. Using a machine learning approach, we revealed that soil pH and total HMs concentration are the major contributors affecting their accumulation in shoot. Overall, our study indicated that MPs may increase the environmental risks of HMs in agroecosystems, especially metal cations.

Interaction of microplastics with heavy metals in soil: Mechanisms, influencing factors and biological effects.

Microplastics (MPs) and heavy metals (HMs) in soil contamination are considered an emerging global problem that poses environmental and health risks. However, their interaction and potential biological effects remain unclear. Here, we reviewed the interaction of MPs with HMs in soil, including its mechanisms, influencing factors and biological effects. Specifically, the interactions between HMs and MPs mainly involve sorption and desorption. The type, aging, concentration, size of MPs, and the physicochemical properties of HMs and soil have significant impacts on the interaction. In particular, MP aging affects specific surface areas and functional groups. Due to the small size and resistance to decomposition characteristics of MPs, they are easily transported through the food chain and exhibit combined biological effects with HMs on soil organisms, thus accumulating in the human body. To comprehensively understand the effect of MPs and HMs in soil, we propose combining traditional experiments with emerging technologies and encouraging more coordinated efforts.

Synergistic interplay between Azospirillum brasilense and exogenous signaling molecule H2S promotes Cd stress resistance and growth in pak choi (Brassica chinensis L.).

Inoculation with growth-promoting rhizobacteria inoculation and the addition of exogenous signaling molecules are two distinct strategies for improving heavy metal resistance and promoting growth in crops through several mechanisms. However, whether rhizobacteria and phyllosphere signaling molecules can act synergistically alleviate heavy metal stress and promote growth and the mechanisms underlying these effects remain unclear. Here, a novel strategy involving the co-application of growth-promoting rhizobacteria and an exogenous signaling molecule was developed to reduce cadmium (Cd) phytotoxicity and promote pak choi growth in Cd-contaminated soil. We found that the co-application of Azospirillum brasilense and hydrogen sulfide (H2S) resulted in significant improvements in shoot biomass and antioxidant enzyme content and a decline in the levels of Cd translocation factors. In addition, this co-application significantly improved pak choi Cd resistance. Furthermore, we observed a significant negative correlation between abscisic acid concentration and Cd content of pak choi and a positive correlation between H2S concentration and biomass. These findings revealed that the co-application of rhizobacteria and exogenous signaling molecules synergistically promoted the growth of vegetable crops subjected to heavy metal stress. Our results may serve as a guide for improving the food safety of crops grown in soil contaminated with heavy metals.

Microplastics addition reduced the toxicity and uptake of cadmium to Brassica chinensis L.

The coexistence of microplastics (MPs) and toxic metal contaminants in soils is becoming increasingly common, thereby posing serious threat to soil-plant systems. Cadmium (Cd) is the most common metal contaminant in soil and can easily combine with MPs, thereby altering its bioavailability. However, few studies have focused on the co-pollution of MPs and Cd, particularly the complex phytotoxicity caused by their interaction and the effect of co-exposure on Cd uptake in plants. We conducted pot experiments to compare the effects of exposure to polystyrene (PS) and Cd, as well as the effects of co-exposure (PS + Cd), on the physiological characteristics of Brassica chinensis L. and explored the regulatory factors of MPs on Cd uptake in plant tissues. The results showed that plant biomass, photosynthetic parameters, and chlorophyll content significantly decreased (p < 0.05) with increasing PS doses under treatment with MPs alone. Although the negative effects of PS and Cd co-exposure on plants were higher than those of PS alone, however, the addition of MPs reduced the toxicity effects of Cd on plants and decreased the uptake and accumulation of Cd by plants compared with the Cd treatment alone. Furthermore, plants can resist the increased malondialdehyde content and oxidative stress induced by PS and Cd exposure by increasing the activities of superoxide dismutase and peroxidase. Under the PS + Cd treatment, linear models showed that soil organic carbon and sucrase activity were the key variables affecting Cd uptake by plant shoots and roots, respectively. The results of the partial least squares path modeling further showed that PS indirectly affected Cd uptake by B. chinensis by significantly affecting the physicochemical properties of soil, Cd concentration, and enzyme activity. Our results provide a new perspective and an important reference for further understanding the effects of MPs on the bioavailability and fate of heavy metals.

A review of microplastics in soil: Occurrence, analytical methods, combined contamination and risks.

Microplastics (MPs) pollution is becoming a serious environmental issue of global concern. Currently, the effects of MPs on aquatic ecosystems have been studied in detail and in depth from species to communities. However, soils, the largest reservoir of MPs, have been less studied, and little is known about the occurrence, environmental fate and ecological impacts of MPs. Therefore, based on the existing knowledge, this paper firstly focused specifically on the main sources of soil MPs pollution and explored the main reasons for their strong heterogeneity in spatial distribution. Secondly, as a primary prerequisite for evaluating MPs contamination, we systematically summarized the analytical methods for soil MPs and critically compared the advantages and disadvantages of the different methods in the various operational steps. Furthermore, this review highlighted the combined contamination of MPs with complex chemical contaminants, the sorption mechanisms and the associated factors in the soil. Finally, the risks posed by MPs to soil, plants, the food chain and even humans were outlined, and future directions for soil MPs research were proposed, while the urgent need for a unified approach to MPs extraction and identification was emphasized. This study provides a theoretical reference for a comprehensive understanding of the separation of soil MPs and their ecological risk as carriers of pollution.

A global meta-analysis of heavy metal(loid)s pollution in soils near copper mines: Evaluation of pollution level and probabilistic health risks.

With the rapid development of the mining industry, the pollution of heavy metal(loid)s in soils near copper (Cu) mining sites is a significant concern worldwide. However, the pollution status and probabilistic health risks of heavy metal(loid)s of soils associated with Cu mines, have rarely been studied on a global scale. In this study, eight heavy metal(loid) concentrations in soil samples taken near 102 Cu mining sites worldwide were obtained through a literature review. Based on this database, the heavy metal(loid) pollution and ecological risk in soils near Cu mines were evaluated. Most of the study sites exceeded the moderately to heavily polluted levels of Cu and Cd; compared to other regions, higher pollution levels were observed at sites in Oman, China, Australia, and the United Kingdom. Soil pollution by Cd, Pb, and Zn at agricultural sites was higher than that in non-agricultural sites. In addition, these heavy metal(loid)s produced a high ecological risk to soils around Cu mining sites in which the contribution of Cd, Cu, and As reached up to 46.5%, 21.7%, and 18.4%, respectively. The mean hazard indices of the eight heavy metal(loid)s were 0.209 and 0.979 for adults and children, respectively. The Monte Carlo simulation further predicted that 1.40% and 29.9% of non-carcinogenic risk values for adults and children, respectively, exceeded the safe level of 1.0. Moreover, 84.5% and 91.0% of the total cancer risk values for adults and children, respectively, exceeded the threshold of 1E-04. Arsenic was the main contributor to non-carcinogenic risk, while Cu had the highest exceedance of carcinogenic risk. Our findings indicate that the control of Cu, Cd, and As should be prioritized because of their high incidence and significant risks in soils near Cu mines. These results provide valuable inputs for policymakers in designing effective strategies for reducing the exposure of heavy metal(loid)s in this area worldwide.

Heat shock cognate protein 70 is required for rice stripe tenuivirus accumulation and transmission in small brown planthopper.

Rice stripe tenuivirus (RSV) is mainly transmitted by the insect vector small brown planthopper (SBPH, Laodelphax striatellus) in a persistent-propagative manner. Virus transmission is dependent on the interplay between viral proteins and vector factors. Pc2, a nonstructural protein of RSV, plays an important role in virus transmission. However, the vector proteins that interact with Pc2 are unknown. In this study, we identified three SBPH proteins that interact with the N-terminal 381 amino acids of Pc2 (Pc2N) by using a yeast two-hybrid system (Y2H). The interaction of Pc2N with heat shock protein cognate 70 (HSC70) was studied further. HSC70 was verified to interact with RSV Pc2N by biomolecular fluorescence complementation and co-immunoprecipitation assays. HSC70 colocalized with RSV Pc2N in both Sf9 cells and the hemocytes of SBPHs. Inhibition of HSC70 expression via RNA interference reduced virus levels in hemolymph and salivary glands of SBPHs and resulted in decreased virus transmission efficiency. These data provide evidence that a vector protein, HSC70, is employed by RSV to facilitate virus accumulation in the hemolymph and thereby promote virus transmission. These findings are important for a better understanding of the interactions between plant viruses and insect vectors.

A critical review of microplastics in the soil-plant system: Distribution, uptake, phytotoxicity and prevention.

Microplastics (MPs) are creating an emerging threat on the soil ecosystems and are of great global concern. However, the distribution in soil-plant system, as well as the phytotoxicity and impact mechanisms of MPs remain largely unexplored so far. This study introduced the diverse sources of MPs and showed the significant spatial variation in the global geographic distribution of MPs contamination based on data collected from 116 studies (1003 sampling sites). We systematically discussed MPs phytotoxicity, such as plant uptake and migration to stems and leaves, delaying seed germination, impeding plant growth, inhibiting photosynthesis, interfering with nutrient metabolism, causing oxidative damage, and producing genotoxicity. We further highlighted the alterations of soil structure and function by MPs, as well as their self and load toxicity, as potential mechanisms that threaten plants. Finally, this paper provided several preventive strategies to mitigate soil MPs pollution and presented research gaps in the biogeochemical behavior of MPs in soil-plant systems. Meanwhile, we recommended that methods for the quantitative detection of MPs accumulated in plant tissues should be explored and established as soon as possible. This review will improve the understanding of the environmental behavior of MPs in soil-plant systems and provide a theoretical reference to better assess the ecological risk of MPs.

Corosolic acid inhibits colorectal cancer cells growth as a novel HER2/HER3 heterodimerization inhibitor.

BACKGROUND AND PURPOSE: Colorectal cancer is the third most common cancer worldwide. HER2 and HER3 are two members of human epidermal receptor family of tyrosine kinase receptors (RTKs) and associated with poor survival in colorectal cancer. They have been observed as important therapeutic targets in various types of cancer. Corosolic acid, a natural pentacyclic triterpene, has been demonstrated to have a significant anti-cancer activity. However, the target of corosolic acid has not yet been explored. This study aimed to reveal the direct targets of corosolic acid underlying its anti-cancer activities. EXPERIMENTAL APPROACH: The targets of corosolic acid were revealed by the phospho-RTK array, bio-layer interferometry, co-immunoprecipitation, and proximity ligation assay. The inhibitory action of corosolic acid on HER2/HER3 heterodimerization and related downstream signalling were investigated in HCT116 and SW480 cells. In addition, the chemo-preventive effects of corosolic acid were validated in both HCT116 xenograft model and AOM/DSS model. KEY RESULTS: Our results demonstrated that corosolic acid could prevent NRG1-induced HER2/HER3 heterodimerization and suppress the phosphorylation of both HER2 and HER3. Furthermore, HER2 and HER3 could regulate the downstream signalling pathways of RalA/RalBP1/CDK1 and PI3K/Akt/PKA, respectively, resulting in the changes in phosphorylation of Drp1 and mitochondrial dynamics. corosolic acid exhibited anti-cancer activity in both HCT116 xenograft model and AOM/DSS model. CONCLUSIONS AND IMPLICATIONS: Collectively, our results demonstrated corosolic acid directly targeted HER2 and HER3 heterodimerization and inhibited mitochondrial fission via regulating RalA/RalBP1/CDK1 and PI3K/Akt/PKA pathways, revealing a novel mechanism underlying the beneficial effects of corosolic acid on colorectal cancer.

The N-terminal cysteine protease domain of rice stripe tenuivirus Pc1 possesses deubiquitinating enzyme activity.

Virus encoded deubiquitinating enzyme (DUB) plays important roles in viral replication and the regulation of host innate immunity. Bioinformatics-based analysis revealed the presence of an ovarian tumor (OTU) protease domain in the N terminus of rice stripe tenuivirus (RSV) Pc1. Many viral OTU domains have been reported to possess DUB activity, which suggests that RSV OTU probably also have DUB activity. To confirm this prediction, we first expressed and purified RSV OTU domain (the N-terminal 200 amino acids of Pc1) and its three mutants (D42A, C45A and H148A) from Escherichia coli and analyzed its DUB activity in vitro. The purified RSV OTU hydrolyzed both K48-linked and K63-linked polyubiquitin chains, indicating RSV OTU domain has DUB enzyme activity in vitro. The mutations of the predicted catalytic sites (Asp42, Cys45 and His148) resulted in the loss of DUB activity, demonstrating these three residues were required for enzyme activity. Then, RSV OTU and its mutants were expressed in insect cells and assayed their DUB activities in vivo by co-transfection with HA-tagged ubiquitin. RSV OTU dramatically reduced ubiquitin-conjugated cellular proteins compared to control and the mutants, showing that RSV OTU also displays DUB activity in vivo. Characterization of RSV OTU DUB enzyme activity and its key catalytic residues will facilitate the development of novel antiviral reagents against RSV.

Study on the hepatobiliary behavior of Ermiao wan formula by microdialysis- LC-qTOF-MS.

An improved bile microdialysis sampling technique was established and coupled with liquid chromatography quadrupole time-of-flight mass spectrometry (LC-qTOF-MS) analysis. This method was successfully applied to investigate the metabolic profiles of Ermiao wan (EMW) formula in the bile of Sprague-Dawley (SD) rats. Based on accurate mass information and fragment patterns, 23 alkaloids and lactones metabolites were tentatively identified. Their metabolic pathway involved in glucuronidation, sulfation, hydroxylation and hydrolysis. Because of the high time resolution of microdialysis, the metabolic profiles of EMW were also investigated. Jatrorrhizine, columbamine and other components showed a "double-peak" profiles, suggesting the existence of enterohepatic circulation. The developed microdialysis sampling/ LC-qTOF-MS method provides a simple and efficient research tool for understanding and clarifying the mechanism of hepatobiliary excretion of complex components.

Ergosterol ameliorates renal inflammatory responses in mice model of diabetic nephropathy.

Ergosterol (ERG) was reported to exhibit anti-inflammatory and anti-oxidative activities. Besides, ERG was found to attenuate kidney injury in the diabetic mouse. However, the protective effect of ERG in diabetic nephropathy-induced inflammation remains unclear. We aimed to study whether ERG could alleviate diabetic nephropathy-induced inflammation and explore the underlying mechanisms. The diabetic nephropathy mice model was induced by intraperitoneal injection of 30 mg/kg Streptozotocin (STZ). The inflammatory cytokines levels, and insulin concentration in the serum of both diabetic nephropathy patients and mouse model were determined by ELISA. mRNA and protein expression were analyzed by RT-PCR and Western blot, respectively. Fasting blood glucose levels were detected using a commercial kit. Blood biochemistry levels were determined by an automatic analyzer. Mesangium proliferation was detected by PAS staining. It was found that serum levels of IL-6, TNF-α, and MCP-1 dramatically increased in the diabetic nephropathy patients. In mice, ERG treatment greatly decreased fasting blood glucose levels, inflammatory cytokine levels, and renal injury, while it enhanced the insulin level. Mechanically, ERG treatment dramatically decreased NF-κB signaling pathway. Our findings highlight the potential of ERG as an effective agent to treat diabetic nephropathy.

Lycium barbarum polysaccharide alleviates oxygen glucose deprivation-induced PC-12 cells damage by up-regulating miR-24.

Objective: This research was aimed to detect the functions of Lycium barbarum polysaccharides (LBPs) on oxygen and glucose deprivation (OGD) injury and potential mechanisms at PC-12 cells. Methods: CCK-8, flow cytometry and reactive oxygen species (ROS) assays were used to detect OGD, LBPs and miR-24 effects on cell viability, apoptosis, and oxidative stress. MiR-24 was transfected and texted by transfection and qRT-PCR. Moreover, the related-protein levels of apoptosis, autophagy and pathways were tested by Western blotting. Results: LBPs significantly enhanced cell viability , inhibited cell apoptosis, autophagy and ROS level in OGD injury. In addition, miR-24 expression was declined in OGD-treated cells, while it was elevated when added LBPs. The preventive effects of LBPs on PC-12 cell damage induced by OGD were reversed by down-regulating miR-24. Furthermore, miR-24 inhibitor declined LBPs-induced change in Wnt/ß-catenin and JAK1/STAT3 pathways in OGD-injuried cells. Conclusions: LBPs exhibited preventive effects via up-regulating miR-122 and activating Wnt/ß-catenin and JAK1/STAT3 pathways in OGD-induced PC-12 cells.

Nucleocapsid Assembly of Baculoviruses.

The baculovirus nucleocapsid is formed through a rod-like capsid encapsulating a genomic DNA molecule of 80~180 kbp. The viral capsid is a large oligomer composed of many copies of various protein subunits. The assembly of viral capsids is a complex oligomerization process. The timing of expression of nucleocapsid-related proteins, transport pathways, and their interactions can affect the assembly process of preformed capsids. In addition, the selection of viral DNA and the injection of the viral genome into empty capsids are the critical steps in nucleocapsid assembly. This paper reviews the replication and recombination of baculovirus DNA, expression and transport of capsid proteins, formation of preformed capsids, DNA encapsulation, and nucleocapsid formation. This review will provide a basis for further study of the nucleocapsid assembly mechanism of baculovirus.

Organized cryogel composites with 3D hierarchical porosity as an extraction adsorbent for nucleosides.

Macroscopic monoliths are highly desirable in many fields of application. Herein, well organized organic-inorganic cryogel composite with a three-dimensional hierarchical meso- and macroporous structure are presented, which were produced by in situ copolymerization of mesoporous multifunctional silica (size: 1-20 µm; pore: 2-20 nm mostly) and monomers (hydroxyethyl methacrylate and diallyldimethylammonium chloride) in water below the freezing point. This copolymerization method effectively adjusted the macropores of the basic cryogel, and the nanosilica was more homogeneously dispersed in the basic cryogel. The specific surface area of the cryogel composite was increased 17 times versus than that of the basic cryogel. The abundant meso- and macroporous pores on the cryogel composite provided sufficient reactive sites favorable for the efficient mass transport of target compounds. When the cryogel composite, as solid phase extraction adsorbent, was coupled with high-performance liquid chromatography, an analytical tool, the nucleosides were quantified with good selectivity, lower detection limits (0.9-1.3 ng/mL) and satisfactory recoveries of greater than 80% from spiked human serum.

3D cryogel composites as adsorbent for isolation of protein and small molecules.

A green and promising sample pretreatment method was successfully established, which efficiently isolated proteins and small molecules in human serum. This method was achieved based on the multifunctional polymer, cryogel, as a solid phase extraction (SPE) monolith easily equipped in a syringe. The cryogel (pDC/GO-DE) was composed of diallyldimethyl ammonium chloride (DC) and 2-hydroxyethyl methacrylate (HE), which was further modified with graphene oxide (GO) and N-diethylethanamine hydrobromide (DE). Various proteins, including bovine serum albumin (BSA), lysozyme (Lys), γ-globulins, immunoglobulin G (IgG), transferrin, small molecules (ribavirin, adenosine, ofloxacin, estriol, rutin, amoxicillin, ibuprofen, 1-methyl-3-phenyl-propylamine, and benzylamine) and their mixtures were successively studied as model analytes to evaluate the new material and demonstrate the isolation mechanism, which was mainly dependent on mixed-mode ion-exchange and the hybrid hydrophobicity-hydrophilicity property of pDC/GO-DE cryogel. Moreover, the three-dimensional macroporous structure contributed to the underlying size-selective isolation. When 10 times diluted human serum was used as the sample, more than 95% of proteins were adsorbed within 10 min under physiological conditions, and the interference matrix in serum was also efficiently reduced. After recycling three times, the extraction ratio of proteins in human serum was still higher than 90%. When four small molecules (camptothecin, ribavirin, 1-methyl-3-phenylpropylamine and ofloxacin) were added to blank human serum, their recoveries were within 65.6-81.8%, and were comparable to those obtained by protein precipitation method (63.7-83.2%).

Characterization of an endonuclease in rice stripe tenuivirus Pc1 in vitro.

Rice stripe tenuivirus (RSV) initiates its mRNA transcription by using the cap-snatching mechanism during which an endonuclease activity is required for the cleavage of host mRNA. In this study, we aim to characterize the endonuclease in RSV. Sequence alignment revealed the presence of a cap-snatching endonuclease domain in RSV Pc1. Expression and in vitro enzymatic activity assay demonstrated that this domain indeed had a manganese-dependent endonuclease activity. The enzyme could efficiently degrade ssRNA with preference for unstructured ssRNA, but not DNA. Mutations in the endonuclease domain allowed the identification of four key residues (D547, D567, E585 and K604). The endonuclease of RSV was similar but not identical to other known viral endonucleases, suggesting that RSV endonuclease may have some distinct catalytic characteristics.