Biology subjects

Guo, X.

Publications and source records attributed to Guo, X..

At least 307 records · Page 17Linked to original sources

bioRxiv2020

HTCC as a highly effective polymeric inhibitor of SARS-CoV-2 and MERS-CoV

The beginning of 2020 brought us information about the novel coronavirus emerging in China. Rapid research resulted in the characterization of the pathogen, which appeared to be a member of the SARS-like cluster, commonly seen in bats. Despite the global and local efforts, the virus escaped the healthcare measures and rapidly spread in China and later globally, officially causing a pandemic and global crisis in March 2020. At present, different scenarios are being written to contain the virus, but the development of novel anticoronavirals for all highly pathogenic coronaviruses remains the major challenge. Here, we describe the antiviral activity of previously developed by us HTCC compound (N-(2-hydroxypropyl)-3-trimethylammonium chitosan chloride), which may be used as potential inhibitor of currently circulating highly pathogenic coronaviruses - SARS-CoV-2 and MERS-CoV.

microbiology↗

bioRxiv2020

Effective Assessments of a Short-duration Poor Posture on Upper Limb Muscle Fatigue before Physical Exercise

A forward head and rounded shoulder posture is a poor posture that is widely seen in everyday life. It is known that sitting in such a poor posture with long hours will bring health issues such as muscle pain. However, it is not known whether sitting in this poor posture for a short period of time will affect human activities. This paper investigates the effects of a shortduration poor posture before some typical physical activities such as push-ups. The experiments are set up as follows. Fourteen male subjects are asked to do push-ups until fatigue with two surface electromyography (sEMG) at the upper limb. Two days later, they are asked to sit in this poor posture for 15 mins with 8 sEMG sensors located at given back muscles. Then they do the push-ups after the short-duration poor posture. The observations from the median frequency of sEMG signals at the upper limb indicate that the short-duration poor posture does affect the fatigue procedure of push-ups. A significant decreasing trend of the performance of push-ups is obtained after sitting in this poor posture. Such effects indicate that some parts of the back muscles indeed get fatigued with only 15 minutes sitting in this poor posture. By further investigating the time-frequency components of sEMG of back muscles, it is observed that the low and middle frequencies of sEMG signals from the infraspinatus muscle of the dominant side are demonstrated to be more prone to fatigue with the poor posture. Although this study focuses only on push-ups, similar experiments can be arranged for other physical exercises as well. This study provides new insights into the effect of a short-duration poor posture before physical activities. These insights can be used to guide athletes to pay attention to postures before physical activities to improve performance and reduce the risk of injury.

bioinformatics↗

bioRxiv2020

A data-driven drug repositioning framework discovered a potential therapeutic agent targeting COVID-19

The global spread of SARS-CoV-2 requires an urgent need to find effective therapeutics for the treatment of COVID-19. We developed a data-driven drug repositioning framework, which applies both machine learning and statistical analysis approaches to systematically integrate and mine large-scale knowledge graph, literature and transcriptome data to discover the potential drug candidates against SARS-CoV-2. The retrospective study using the past SARS-CoV and MERS-CoV data demonstrated that our machine learning based method can successfully predict effective drug candidates against a specific coronavirus. Our in silico screening followed by wet-lab validation indicated that a poly-ADP-ribose polymerase 1 (PARP1) inhibitor, CVL218, currently in Phase I clinical trial, may be repurposed to treat COVID-19. Our in vitro assays revealed that CVL218 can exhibit effective inhibitory activity against SARS-CoV-2 replication without obvious cytopathic effect. In addition, we showed that CVL218 is able to suppress the CpG-induced IL-6 production in peripheral blood mononuclear cells, suggesting that it may also have anti-inflammatory effect that is highly relevant to the prevention immunopathology induced by SARS-CoV-2 infection. Further pharmacokinetic and toxicokinetic evaluation in rats and monkeys showed a high concentration of CVL218 in lung and observed no apparent signs of toxicity, indicating the appealing potential of this drug for the treatment of the pneumonia caused by SARS-CoV-2 infection. Moreover, molecular docking simulation suggested that CVL218 may bind to the N-terminal domain of nucleocapsid (N) protein of SARS-CoV-2, providing a possible model to explain its antiviral action. We also proposed several possible mechanisms to explain the antiviral activities of PARP1 inhibitors against SARS-CoV-2, based on the data present in this study and previous evidences reported in the literature. In summary, the PARP1 inhibitor CVL218 discovered by our data-driven drug repositioning framework can serve as a potential therapeutic agent for the treatment of COVID-19.

systems biology↗

bioRxiv2020

A quantitative framework reveals the ecological drivers of grassland soil microbial community assembly in response to warming

Unraveling the drivers controlling community assembly is a central issue in ecology. Selection, dispersal, diversification and drift are conceptually accepted as major community assembly processes. Defining their relative importance in governing biodiversity is compellingly needed, but very challenging. Here, we present a novel framework to quantitatively infer community assembly mechanisms by phylogenetic bin-based null model analysis (iCAMP). Our results with simulated microbial communities showed that iCAMP had high accuracy (0.93 - 0.99), precision (0.80 - 0.94), sensitivity (0.82 - 0.94), and specificity (0.95 - 0.98), which were 10-160% higher than those from the entire community-based approach. Applying it to grassland microbial communities in response to experimental warming, our analysis showed that homogeneous selection (38%) and "drift" (59%) played dominant roles in controlling grassland soil microbial community assembly. Interestingly, warming enhanced homogeneous selection, but decreased "drift" over time. Warming-enhanced selection was primarily imposed on Bacillales in Firmicutes, which were strengthened by increased drought and reduced plant productivity. This general framework should also be useful for plant and animal ecology.

ecology↗

bioRxiv2020

Lower Soil Carbon Loss Due to Persistent Microbial Adaptation to Climate Warming

Soil microbial respiration is an important source of uncertainty in projecting future climate and carbon (C) cycle feedbacks. Despite intensive studies for two decades, the magnitude, direction, and duration of such feedbacks are uncertain, and their underlying microbial mechanisms are still poorly understood. Here we examined the responses of soil respiration and microbial community structure to long-term experimental warming in a temperate grassland ecosystem. Our results indicated that the temperature sensitivity of soil microbial respiration (i.e., Q10) persistently decreased by 12.0{+/-}3.7% across 7 years of warming. Integrated metagenomic and functional analyses showed that microbial community adaptation played critical roles in regulating respiratory acclimation. Incorporating microbial functional gene abundance data into a microbially-enabled ecosystem model significantly improved the modeling performance of soil microbial respiration by 5-19%, compared to the traditional non-microbial model. Model parametric uncertainty was also reduced by 55-71% when gene abundances were used. In addition, our modeling analyses suggested that decreased temperature sensitivity could lead to considerably less heterotrophic respiration (11.6{+/-}7.5%), and hence less soil C loss. If such microbially mediated dampening effects occur generally across different spatial and temporal scales, the potential positive feedback of soil microbial respiration in response to climate warming may be less than previously predicted.

ecology↗

bioRxiv2020

Genetic loci associated with prevalent and incident myocardial infarction and coronary heart disease in the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) Consortium

BackgroundGenome-wide association studies have identified multiple genomic loci associated with coronary artery disease, but most are common variants in non-coding regions that provide limited information on causal genes and etiology of the disease. To better understand etiological pathways that might lead to discovery of new treatments or prevention strategies, we focused our investigation on low-frequency and rare sequence variations primarily residing in coding regions of the genome while also exploring associations with common variants. Methods and ResultsUsing samples of individuals of European ancestry from ten cohorts within the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) consortium, both cross-sectional and prospective analyses were conducted to examine associations between genetic variants and myocardial infarction (MI), coronary heart disease (CHD), and all-cause mortality following these events. Single variant and gene-based analyses were performed separately in each cohort and then meta-analyzed for each outcome. A low-frequency intronic variant (rs988583) in PLCL1 was significantly associated with prevalent MI (OR=1.80, 95% confidence interval: 1.43, 2.27; P=7.12 x 10-7). Three common variants, rs9349379 in PHACTR1, and rs1333048 and rs4977574 in the 9p21 region, were significantly associated with prevalent CHD. Four common variants (rs4977574, rs10757278, rs1333049, and rs1333048) within the 9p21 locus were significantly associated with incident MI. We conducted gene-based burden tests for genes with a cumulative minor allele count (cMAC) [≥] 5 and variants with minor allele frequency (MAF) < 5%. TMPRSS5 and LDLRAD1 were significantly associated with prevalent MI and CHD, respectively, and RC3H2 and ANGPTL4 were significantly associated with incident MI and CHD, respectively. No loci were significantly associated with all-cause mortality following a MI or CHD event. ConclusionThis study confirmed previously reported loci influencing heart disease risk, and one single variant and three genes associated with MI and CHD were newly identified and warrant future investigation.

genetics↗

bioRxiv2020

No solid evidence of soil carbon loss under warming in tropical forests along a 3000 m elevation gradient

Soil organic carbon (SOC) decomposition is inherently sensitive to temperature. As such, a big concerning is the potential SOC loss under climatic warming, but field empirical evidences are lacking, particularly in tropical forest soils in which [~]10% of global SOC is stored. Recently Nottingham et al. (2019) assessed the data collected from a novel experiment translocating soils across a 3000 m tropical forest elevation gradient to mimic temperature changes in situ, and concluded that warming caused considerable SOC loss. However, this conclusion was based on a metric with a strong assumption that soil cores translocated to other elevations on average had the same initial SOC content to control soil cores reinstalled at their original elevation. Because of limited replicates (n =3) in the data, an approach ignoring spatial heterogeneity of SOC content may undermine the credibility of the results. Here, we used a nonparametric bootstrap approach to re-analyze the data, explicitly taking data variability into account. Contrary to Nottingham et al. (2019), we found that SOC content did not show significant differences among translocated soils from the same elevation origin. Further looking into six chemical fractions determined by 13C NMR spectroscopy shown that they had similar, insignificant response to translocation-induced temperature changes, which also does not support the conclusion of Nottingham et al (2019) that labile SOC is more sensitive to warming. We concluded that temperature changes did not significantly alter either total SOC content or its six chemical fractions after five years of shift of temperature regimes in tropical forests. This may largely due to thermal adaptation of microbial decomposition and environmental constrains (e.g., low pH) which suppress the effect of temperature changes. Longer term experiment with more sampling replicates are required to maximize the value of soil translocation experiments to address the effect of warming on SOC dynamics.

ecology↗

bioRxiv2020

Molecular Modeling Evaluation of the Binding Abilities of Ritonavir and Lopinavir to Wuhan Pneumonia Coronavirus Proteases

Three anti-HIV drugs, ritonavir, lopinavir and darunavir, might have therapeutic effect on coronavirus disease 2019 (COVID-19). In this study, the structure models of two severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) proteases, coronavirus endopeptidase C30 (CEP_C30) and papain like viral protease (PLVP), were built by homology modeling. Ritonavir, lopinavir and darunavir were then docked to the models, respectively, followed by energy minimization of the protease-drug complexes. In the simulations, ritonavir can bind to CEP_C30 most suitably, and induce significant conformation changes of CEP_C30; lopinavir can also bind to CEP_C30 suitably, and induce significant conformation changes of CEP_C30; darunavir can bind to PLVP suitably with slight conformation changes of PLVP. It is suggested that the therapeutic effect of ritonavir and lopinavir on COVID-19 may be mainly due to their inhibitory effect on CEP_C30, while ritonavir may have stronger efficacy; the inhibitory effect of darunavir on SARS-CoV-2 and its potential therapeutic effect may be mainly due to its inhibitory effect on PLVP.

biochemistry↗

bioRxiv2020

High-throughput screens of PAM-flexible Cas9 variants for gene knock-out and transcriptional modulation

A key limitation of the commonly-used CRISPR enzyme S. pyogenes Cas9 is the strict requirement of an NGG protospacer-adjacent motif (PAM) at the target site, which reduces the number of accessible genomic loci. This constraint can be limiting for genome editing applications that require precise Cas9 positioning. Recently, two Cas9 variants with a relaxed PAM requirement (NG) have been developed (xCas9 and Cas9-NG) but their activity has been measured at only a small number of endogenous sites. Here we devised a high-throughput Cas9 pooled competition screen to compare the performance of both PAM-flexible Cas9 variants and wild-type Cas9 at thousands of genomic loci and across 3 modalities (gene knock-out, transcriptional activation and suppression). We show that PAM flexibility comes at a substantial cost of decreased DNA targeting and cutting. Of the PAM-flexible variants, we found that Cas9-NG outperforms xCas9 regardless of genome engineering modality or PAM. Finally, we combined xCas9 mutations with those of Cas9-NG, creating a stronger transcriptional modulator than existing PAM-flexible Cas9 variants.

bioengineering↗

bioRxiv2020

IRESbase: a Comprehensive Database of Experimentally Validated Internal Ribosome Entry Sites

Internal Ribosome Entry Sites (IRESs) are functional RNA elements that can directly recruit ribosomes to an internal position of the mRNA in a cap-independent manner to initiate translation. Recently, IRES elements have attracted much attention for their critical roles in various processes including translation initiation of a new type of RNA, circular RNA, with no 5' cap to support classical cap-dependent translation. Thus, an integrative data resource of IRES elements with experimental evidences will be useful for further studies. In this study, we present a comprehensive database of IRESs (IRESbase) by curating the experimentally validated functional minimal IRES elements from literature and annotating their host linear and circular RNA information. The current version of IRESbase contains 1328 IRESs, including 774 eukaryotic IRESs and 554 viral IRESs from 11 eukaryotic organisms and 198 viruses. As our database collected only IRES of minimal length with functional evidences, the median length of IRESs in IRESbase is 174 nucleotides. By mapping IRESs to human circRNAs and lncRNAs, 2191 circRNAs and 168 lncRNAs were found to contain at least one entire or partial IRES sequences. The IRESbase is available at http://reprod.njmu.edu.cn/cgi-bin/iresbase/index.php.

bioinformatics↗

bioRxiv2020

The Nonequilibrium Mechanism of Noise Enhancer synergizing with Activator in HIV Latency Reactivation

Reactivating HIV latency and then simultaneously eliminating it by antiretroviral therapy has become a leading strategy in curing HIV. Recently, single-cell screening experiments have shown the drug synergy between two categories of biomolecules, Activators (AC) and Noise Enhancers (NE): NE can amplify the reactivation of latent HIV induced by AC, although NE itself cannot reactivate HIV latency. Based on an established LTR-two-state effective model, we uncover two necessary conditions for this type of drug synergy: The decreasing of the turning-on rate of LTR induced by NE is highly inhibited when presented with AC; The timescale of LTR turning off without AC/NE presented should be no slower than the timescale of Tat transactivation. Then we propose a detailed LTR-four-state mechanistic model with both AC/NE regulation kinetics and Tat transactivation circuit. We show that, in order to achieve drug synergy, the system of HIV gene state transition must operate out of thermodynamic equilibrium, which is caused by energy input. The direction of energy input determines whether the inhibition of NE upon the reactivation rate of LTR-off states (unbinding of RNAP) can be successfully prevented in the presence of AC. The drug synergy can also be significantly enhanced if the energy input is appropriately distributed to more than one reaction. Our model reveals a generic nonequilibrium mechanism underpinning the noise enhanced drug synergy, which may apply to identify the same drug synergy on reactivating a diverse class of lentivirus latency. Significance StatementThe "kick and kill" strategy has become a promising way to cure HIV by eliminating latent HIV reservoirs, the main barrier to a clinical cure. Two categories of biomolecules, Activators (AC) and Noise Enhancers (NE), have been found to have synergy on reactivating latent HIV (kick strategy). We uncover the underlying non-equilibrium mechanism of such drug synergy by developing mathematical models based on genetic regulatory kinetics. We find that controlling the magnitude and direction of energy input into genetic regulatory kinetics can prevent NE from reducing the turn-on rate of the inactivated gene state in the presence of AC, which produces the synergy. This general nonequilibrium mechanism can be useful for identifying other drug synergies on lentivirus latency reactivation.

systems biology↗

bioRxiv2020

Acquisition of Oral Microbiota is Driven by Environment, Not Host Genetics

The human oral microbiota is acquired early in an organized pattern, but the factors driving this acquisition are not well understood. Microbial "heritability" could have far-reaching consequences for health, yet no studies have specifically examined the fidelity with which the oral microbiota are passed from parents to offspring. Some previous studies comparing monozygotic (MZ) and dizygotic (DZ) twins had suggested that host genetics has a role in shaping oral microbial communities, and also identified so called "heritable" taxa. However, these findings are likely to be confounded by shared environmental factors resulting from the well-established greater behavioral similarity among MZ twins. In addition, MZ and DZ twins share an equal portion of their parents genome, and so this model is not informative for studying direct parent to offspring transmission. To specifically examine the contribution of genetics to the fidelity of transmission of bacteria from parents to offspring, we used a novel study design comparing fraction of shared species and strains between our genetically related group consisting of children and their biological mothers, with that of children and their adoptive mothers, constituting our genetically unrelated group. Fifty-five biological and 50 adoptive mother-child pairs were recruited along with 23 biological fathers and 16 siblings. Subjects were carefully selected to ensure the two groups were matched on childs age. Three distinct habitats within the oral cavity: the saliva/soft tissue surface, supragingival biofilm, and subgingival biofilm, were sampled to comprehensively profile the oral microbiome. Our recently developed strategy for subspecies level characterization of bacterial communities by targeted sequencing of the ribosomal 16-23S intergenic spacer region (ISR) was utilized in the present study to track strain sharing between subjects, in addition to 16S rRNA gene sequencing for species analysis. Results showed that oral bacterial community profiles of adoptive and biological mother-child pairs were equally similar, indicating no effect of host genetics on the fidelity of transmission. This was consistent at both species and strain level resolutions, and across all three habitats sampled. We also found that all children more closely resembled their own mother as compared to unrelated women, suggesting that contact and shared environment were the major factors shaping the oral microbiota. Individual analysis of the most abundant species also did not detect any effect of host genetics on strain sharing between mother and child. Mother-child strain similarity increased with the age of the child, ruling out early effects that are lost over time. No effect on the fidelity of mother-child strain sharing from vaginal birth or breast feeding was seen. Analysis of extended families showed that fathers and mothers were equally similar to their children. Cohabitating couples showed even greater strain similarity than mother-child pairs, further supporting the role of age, contact and shared environment as determinants of microbial similarity. Based on these findings we suggest that the genetic effects on oral microbial acquisition observed in twin studies are more likely the result of confounding environmental factors based on greater behavioral similarity among MZ twins. Our findings suggest that these host mechanisms are universal to humans, since no effect of genetic relatedness on fidelity of microbial transmission could be detected. Instead, our findings point toward contact and shared environment being the driving factors of microbial transmission, with a unique combination of these factors ultimately shaping a highly personalized human oral microbiome.

microbiology↗

bioRxiv2019

Principles for rational Cas13d guide design

Type VI CRISPR enzymes have recently been identified as programmable RNA-guided, RNA-targeting Cas proteins with nuclease activity that allow for specific and robust target gene knock-down without altering the genome. However, we currently lack information about optimal Cas13 guide RNA designs for high target RNA knock-down efficacy. To close this gap, we conducted four massively-parallel Cas13 screens targeting the mRNA of a destabilized green fluorescent protein (GFP) transgene and CD46, CD55 and CD71 cell surface proteins in human cells. In total, we measured the activity of 24,460 guide RNA including 6,469 perfect match guide RNAs and a diverse set of guide RNA variants and permutations with mismatches relative to the target sequences. We find that guide RNAs show high diversity in knock-down efficiency driven by crRNA-specific features as well as target site context. Moreover, while single mismatches generally reduce knock-down to a modest degree, we identify a critical region spanning spacer nucleotides 15 - 21 that is largely intolerant to target site mismatches. We developed a computational model to identify guide RNAs with high knock-down efficacy. We confirmed the models generalizability across a large number of endogenous target mRNAs and show that Cas13 can be used in forward genetic pooled CRISPR-screens to identify essential genes. Using this model, we provide a resource of optimized Cas13 guide RNAs to target all protein-coding transcripts in the human genome, enabling transcriptome-wide forward genetic screens.

genomics↗

bioRxiv2019

Microbial microdroplet culture system (MMC): an integrated platform for automated, high-throughput microbial cultivation and adaptive evolution

Conventional microbial cell cultivation techniques are typically labor intensive, low throughput, and poor parallelization, rendering them inefficient. The development of automated, modular microbial cell micro-cultivation systems, particularly those employing droplet microfluidics, has gained attention for their high-throughput, parallel and highly efficient cultivation capabilities. Here, we report the development of a microbial microdroplet culture system (MMC), which is an integrated platform for automated, high-throughput cultivation and adaptive evolution of microorganisms. We demonstrated that the MMC yielded both accurate and reproducible results for the manipulation and detection of droplets. The superior performance of MMC for microbial cell cultivation was validated by comparing the growth curves of six microbial strains grown in MMC, conventional shake flasks or well plates. The highest incipient growth rate for all six microbial cell lines was achieved using MMC. We also conducted an 18-day process of adaptive evolution of a methanol-essential Escherichia coli strain in MMC and obtained two strains exhibiting higher growth rates compared with the parent strain. Our study demonstrates the power of MMC to provide an efficient and reliable approach for automated, high-throughput microbial cultivation and adaptive evolution.

bioengineering↗

bioRxiv2019

A clinically and genomically annotated nerve sheath tumor biospecimen repository.

Nerve sheath tumors occur as a heterogeneous group of neoplasms in patients with neurofibromatosis type 1 (NF1). The malignant form represents the most common cause of death in people with NF1, and even when benign, these tumors can result in significant disfigurement, neurologic dysfunction, and a range of profound symptoms. Lack of human tissue across the peripheral nerve tumors common in NF1 has been a major limitation in the development of new therapies. To address this unmet need, we have created an annotated collection of patient tumor samples, patient-derived cell lines, and patient-derived xenografts, and carried out high-throughput genomic and transcriptomic characterization to serve as a resource for further biologic and preclinical therapeutic studies. In this work, we release genomic and transcriptomic datasets comprised of 55 tumor samples derived from 23 individuals, complete with clinical annotation. All data are publicly available through the NF Data Portal and at http://synapse.org/jhubiobank.

cancer biology↗

bioRxiv2019

Identification of a small molecule antagonist for the Tudor domain of SMN

Survival of motor neuron (SMN), a Tudor-domain-containing protein, plays an important role in diverse biological pathways via recognition of symmetrically dimethylated arginine (Rme2s) on proteins by its Tudor domain, and deficiency of SMN leads to the motor neuron degenerative disease spinal muscular atrophy (SMA). Here we report a potent and selective antagonist with a 4-iminopyridine scaffold targeting the Tudor domain of SMN. Our structural and mutagenesis studies indicate that the sandwich stacking interactions of SMN and compound 1 play a critical role in selective binding to SMN. Various on-target engagement assays support that compound 1 recognizes SMN specifically in a cellular context. In cell studies display that the SMN antagonist prevent the interaction of SMN with R1810me2s of DNA-directed RNA polymerase II subunit POLR2A and results in transcription termination and R-loop accumulation, mimicking depletion of SMN. Thus, in addition to the antisense, RNAi and CRISPR/Cas9 techniques, the potent SMN antagonist could be used as an efficient tool in understanding the biological functions of SMN and molecular etiology in SMA.

biochemistry↗

bioRxiv2019

Development of SSR markers related to seed storability traits in maize subjected to artificial seed aging conditions

Seed storability is an important and complex agronomic trait in maize because annual seed production considerably exceeds consumption. The viability of seeds decreases over time, even when stored at low temperature, until seeds finally lose viability. In our previous study, two inbred lines with significantly different storability, Dong156 with high storage tolerance and Dong237 with low storage tolerance, were selected over six years using a natural seed aging test. In the present study, an F2:3 population and a RIL (recombinant inbred line) population were constructed from these two inbred lines and used to map QTL (quantitative trait loci) with SSR (simple sequence repeat) markers. A phenotypic index of traits related to seed storability that includes germination rate, germination potential, a germination index, a vigor index, seedling weight, and seedling length was generated using the results of an artificial aging treatment. Two consistent regions, cQTL-7 on chromosome 7 and cQTL-10 on chromosome 10, were identified by comparing QTL analysis results from these two populations. After genotyping SSR markers in these two regions, cQTL-7 was remapped to between umc1671 and phi328175 in a 7.97-Mb region, and cQTL-10 was remapped to between umc1648 and phi050 in a 39.15-Mb region. Four SSR markers linked to cQTL-7 and cQTL-10, including umc1671, phi328175, umc1648, and phi050, were identified using a Chi-squared test. The combined selection efficiency of these four markers was 83.94% in 85 RIL lines with high storability, and marker umc1648 exhibited the highest efficiency value of 88.89%. These results indicated that the four SSR markers developed in this study could be used for selection of maize germplasm with high seed storability.

plant biology↗

bioRxiv2019

The stepwise endonuclease activity of a thermophilic Argonaute protein

Thermophilic Argonaute proteins (Agos) can function as endonucleases via specific guide-target base-pairing cleavage for host defense. The ability to cleave target DNA sequences at any arbitrary sites endows them with reprogramed DNA capacity. Here, we identify that an Ago from the hyperthermophilic archaeon Pyrococcus furiosus (PfAgo) shows a stepwise endonuclease activity, which is demonstrated by the double strand DNA cleavage directed by a single guide DNA rather than canonical one pair of guide DNAs. We reveal that the cleavage products with 5-phosphorylated ends can used as the renewed guide which is capable to induce next round of cleavage to complementary sequences of target DNA. By combining the PfAgo stepwise endonuclease activity followed by target DNA amplification, we establish a rapid and specific platform for the unambiguously multiplex gene detection, termed RADAR (Renewed-gDNA Assisted DNA-cleavage by Argonaute). In the end, RADAR was applied to distinguish of human papillomavirus of serotypes in patient samples in a single reaction, suggesting that our technique would be adopted for diagnosing application.

bioengineering↗