Weak Pathogen Research Articles

Phylogenomic analyses and comparative genomics of Pseudomonas syringae associated with almond (Prunus dulcis) in California.

We sequenced and comprehensively analysed the genomic architecture of 98 fluorescent pseudomonads isolated from different symptomatic and asymptomatic tissues of almond and a few other Prunus spp. Phylogenomic analyses, genome mining, field pathogenicity tests, and in vitro ice nucleation and antibiotic sensitivity tests were integrated to improve knowledge of the biology and management of bacterial blast and bacterial canker of almond. We identified Pseudomonas syringae pv. syringae, P. cerasi, and P. viridiflava as almond canker pathogens. P. syringae pv. syringae caused both canker and foliar (blast) symptoms. In contrast, P. cerasi and P. viridiflava only caused cankers, and P. viridiflava appeared to be a weak pathogen of almond. Isolates belonging to P. syringae pv. syringae were the most frequently isolated among the pathogenic species/pathovars, composing 75% of all pathogenic isolates. P. cerasi and P. viridiflava isolates composed 8.3 and 16.7% of the pathogenic isolates, respectively. Laboratory leaf infiltration bioassays produced results distinct from experiments in the field with both P. cerasi and P. syringae pv. syringae, causing significant necrosis and browning of detached leaves, whereas P. viridiflava conferred moderate effects. Genome mining revealed the absence of key epiphytic fitness-related genes in P. cerasi and P. viridiflava genomic sequences, which could explain the contrasting field and laboratory bioassay results. P. syringae pv. syringae and P. cerasi isolates harboured the ice nucleation protein, which correlated with the ice nucleation phenotype. Results of sensitivity tests to copper and kasugamycin showed a strong linkage to putative resistance genes. Isolates harbouring the ctpV gene showed resistance to copper up to 600 μg/ml. In contrast, isolates without the ctpV gene could not grow on nutrient agar amended with 200 μg/ml copper, suggesting ctpV can be used to phenotype copper resistance. All isolates were sensitive to kasugamycin at the label-recommended rate of 100μg/ml.

Genetic and Functional Diversity Help Explain Pathogenic, Weakly Pathogenic, and Commensal Lifestyles in the Genus Xanthomonas.

The genus Xanthomonas has been primarily studied for pathogenic interactions with plants. However, besides host and tissue-specific pathogenic strains, this genus also comprises nonpathogenic strains isolated from a broad range of hosts, sometimes in association with pathogenic strains, and other environments, including rainwater. Based on their incapacity or limited capacity to cause symptoms on the host of isolation, nonpathogenic xanthomonads can be further characterized as commensal and weakly pathogenic. This study aimed to understand the diversity and evolution of nonpathogenic xanthomonads compared to their pathogenic counterparts based on their cooccurrence and phylogenetic relationship and to identify genomic traits that form the basis of a life history framework that groups xanthomonads by ecological strategies. We sequenced genomes of 83 strains spanning the genus phylogeny and identified eight novel species, indicating unexplored diversity. While some nonpathogenic species have experienced a recent loss of a type III secretion system, specifically the hrp2 cluster, we observed an apparent lack of association of the hrp2 cluster with lifestyles of diverse species. We performed association analysis on a large data set of 337 Xanthomonas strains to explain how xanthomonads may have established association with the plants across the continuum of lifestyles from commensals to weak pathogens to pathogens. Presence of distinct transcriptional regulators, distinct nutrient utilization and assimilation genes, transcriptional regulators, and chemotaxis genes may explain lifestyle-specific adaptations of xanthomonads.

Biological characteristics of a precocious line of Eimeria tenella.

The Eimeria tenella Yulin strain (EtYL), which is sensitive to most anti-coccidial drugs, was isolated in the Yulin area of Guangxi, China. Then, Eimeria tenella Yulin precocious line (pEtYL), a precocious line with a prepatent period of 108h, was obtained through early selection. The biological characteristics of pEtYL, including its morphology, purity, oocyst excretion curve, reproductive capacity, pathogenicity, immunogenicity, and preservation time, were comprehensively analyzed. The results showed that the isolated precocious line of E. tenella exhibited high purity, relatively weak pathogenicity, and good immunogenicity and can be used as a live vaccine line for chicken coccidiosis.

Construction and characterization of a full-length infectious clone of an emerging senecavirus A strain.

Senecavirus A (SVA) is an emerging virus that causes vesicular disease in pigs. Construction of a full-length SVA cDNA clone is crucial for understanding its replication and pathogenesis. Here, we successfully constructed a CMV-promoter-driven infectious cDNA clone of the SVA isolate SVA/GX/CH/2018, which we named rSVA GX01. Sequence comparison between the pSVA GX01 and the parental isolate (SVA/GX/CH/2018) revealed three single-nucleotide differences. Four-week-old piglets were experimentally infected with either the parental virus or the cloned virus. The results showed that the cloned rSVA GX01 displayed weak pathogenicity in 4-week-old pigs compared to the parental virus SVA CH-GX-01-2018. The infectious clone of SVA will serve as a valuable tool for studying the viral replication cycle and for functional analysis of the viral genome.

Influence of Co-occurring Weakly Pathogenic Bacterial Species on Bacterial Spot Disease Dynamics on Tomato.

Mixed infections caused by multiple pathogenic and weakly pathogenic strains inhabiting the same host plants are common in nature and may modify pathogen dynamics. However, traditional plant pathogen studies have mostly focused on the binary interaction between a single host and a single pathogen. In this study, we have looked beyond this binary interaction and evaluated the impact of coinfection on disease dynamics on tomato using the bacterial spot pathogen Xanthomonas perforans (Xp), the co-occurring weakly pathogenic strain of X. arboricola (Xa), and the co-occurring potential weak pathogenic strain of Pseudomonas capsici (Pc). Time-series coinfection experiments monitoring disease severity and within-host population dynamics revealed higher disease severity in coinfection by three species compared with infection by Xp alone. However, coinfection by dual species, Xp and Pc, or Xa resulted in lower disease severity compared with Xp alone. Thus, coinfection outcomes depend on interacting species. Weak pathogens could exploit Xp to colonize the host plant as indicated by their higher populations in coinfection. However, Xp population dynamics were dependent on the coinfecting partner. While resource competition might be a possible explanation for lower Xp population in dual coinfection, interaction of Pc with the host was found to influence Xp population. Interestingly, Xp population was higher in the presence of three-species interaction compared with Xp and Xa coinfection, suggesting potential modulation of cooperative interactions among Xp and Xa in three-species coinfection rather than competitive interactions. Humidity played a significant role in population dynamics of the three species. Overall, this study highlighted the importance of coinfection dynamics in studying plant disease outbreaks.

The Complete Genome Sequence of Pseudomonas syringae pv. actinidifoliorum ICMP 18803

The genome of Pseudomonas syringae pv. actinidifoliorum ICMP18803 (Pfm) was sequenced using the Oxford Nanopore MinION platform to an average read depth of 123-fold. The genome assembled into a single chromosome of 6,353,853 bp after error correction with Illumina short reads using Pilon. No plasmids were detected. Despite Pfm only being a relatively weak pathogen of kiwifruit, a set of 31 effectors, 26 of which were full length, was identified by mapping the comprehensive effector library generated by previous researchers to the assembled chromosome. A revised Pfm genome with the effector complement correctly named and annotated was resubmitted to GenBank (CP081457). [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

BdCV1-Encoded P3 Silencing Suppressor Identification and Its Roles in Botryosphaeria dothidea, Causing Pear Ring Rot Disease.

Pear ring rot disease is an important branch disease, caused by Botryosphaeria dothidea. With the discovery of fungal viruses, the use of their attenuated properties for biological control provides a new strategy for the biological control of fungal disease. RNA silencing is a major antiviral defense mechanism in plants, insects, and fungi. Viruses encode and utilize RNA silencing suppressors to suppress host defenses. Previous studies revealed that Botryosphaeria dothidea chrysovirus 1 (BdCV1) exhibited weak pathogenicity and could activate host gene silencing by infecting B. dothidea. The aim of our study was to investigate whether BdCV1 can encode a silencing suppressor and what effect it has on the host. In this study, the capability of silencing inhibitory activity of four BdCV1-encoded proteins was analyzed, and the P3 protein was identified as a BdCV1 RNA silencing suppressor in the exotic host Nicotiana benthamiana line 16c. In addition, we demonstrated that P3 could inhibit local silencing, block systemic RNA silencing, and induce the necrosis reaction of tobacco leaves. Furthermore, overexpression of P3 could slow down the growth rate and reduce the pathogenicity of B. dothidea, and to some extent affect the expression level of RNA silencing components and virus-derived siRNAs (vsiRNAs). Combined with transcriptomic analysis, P3 had an effect on the gene expression and biological process of B. dothidea. The obtained results provide new theoretical information for further study of interaction between BdCV1 P3 as a potential silencing suppressor and B. dothidea.

Identification of SARS-CoV-2 m6A modification sites correlate with viral pathogenicity

It has recently been found that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) m6A modifications can affect viral replication and function. However, no studies to date have shown a correlation between SARS-CoV-2 m6A modifications and viral pathogenicity. In this study, we analyzed m6A modification in 2,190,667 SARS-CoV-2 genomic RNAs. m6A modifications of SARS-CoV-2 from different lineages, causing mild or severe COVID-19 and showing breakthrough for different vaccines were analyzed to explore correlations with viral pathogenicity. The results suggested that the presence of more m6A modifications in the SARS-CoV-2 N region (positive strand) correlates with weaker pathogenicity. In addition, we identified three m6A modification sites correlating with weak pathogenicity (924 in ORF1ab, 15,659 in ORF1ab, 28,288 in N, 28,633 in N and 29,385 in N, 29,707 in 3′UTR) and one with strong pathogenicity (74 in 5′UTR). These results provide new information for understanding the prevalence of SARS-CoV-2 and controlling the virus.

Mathematical analysis on a diffusion model describing the compatibility between two types of tumor cells

Cancer caused by malignant tumor is a very common and serious disease which can lead to people towards death. However, sometimes, cancer may be controlled if the cancer cells can be infected and split by particular virus with weak pathogenicity. To give a better understanding on tumor dynamics, in this paper, we deal with a reaction–diffusion tumor model, which comes from the process of tumor therapy with oncolytic virus. Our main objective is to analyze the biological compatibility of uninfected and infected tumor cells. In addition, we are concerned with the long‐time behavior, stability, and a priori estimates for the model. The compatibility conditions show that under certain range of parameters control, the infected tumor cells can coexist with normal tumor cells or be eliminated by oncolytic virus as time goes on; in the elimination case, it implies that the organism's complete recovery is highly possible as a result of the attack of oncolytic virus. An indirect idea in calculating fixed point index is proposed; correspondingly, a new condition on coexistence is presented.

Miscanthus sinensis contributes to the survival of Pinus densiflora seedlings at a mining site via providing a possible functional endophyte and maintaining symbiotic relationship between P. densiflora and endophytes from high soil temperature stress.

At a sedimentary site in an old mine site, Miscanthus sinensis formed patches, where Pinus densiflora seedlings could grow better compared with those outside the patches, indicating that M. sinensis would improve P. densiflora seedling establishment. The purpose of this study was to understand the mechanisms by which M. sinensis facilitates the survival of P. densiflora seedlings by considering the soil properties, heavy metal tolerance, and root endophytes in P. densiflora seedlings at the sedimentary site. The sedimentary site, which is a bare ground, contained high concentrations of Fe, indicating that plants should be exposed to Fe and high soil temperature stresses. Measurement of soil temperature revealed that M. sinensis suppressed sharp increases and alternation of soil temperature, resulting in reducing high soil temperature stress in P. densiflora seedlings. To adapt to the Fe stress environment, P. densiflora outside and inside the patches produced Fe detoxicants, including catechin, condensed tannin, and malic acid. Ceratobasidium bicorne and Aquapteridospora sp. were commonly isolated from P. densiflora seedlings outside and inside the patches as root endophytes, which might enhance Fe tolerance in the seedlings. Aquapteridospora sp., which is considered as a dark-septate endophyte (DSE), was also isolated from the roots of M. sinensis, suggesting that M. sinensis might play a source of a root endophyte to P. densiflora seedlings. Ceratobasidium bicorne could be classified into root endophytes showing symbiosis and weak pathogenicity to host plants. Therefore, high soil temperature stress would weaken P. densiflora seedlings, causing root endophytic C. bicorne to appear pathogenic. We suggested that P. densiflora could adapt to the Fe stress environment via producing Fe detoxicants, and M. sinensis would facilitate the establishment of P. densiflora seedlings in the sedimentary site by providing a DSE, Aquapteridospora sp., and maintaining symbiosis of C. bicorne from high soil temperature stress.

Biological characterization of isolated pigeon Paramyxovirus-1 and its pathogenicity analysis in SPF chickens

Pigeon paramyxovirus type 1 (PPMV-1) is considered as an antigenic variant of Newcastle Disease leading to high mortality and significant economic losses to the poultry industry. However, the pathogenicity of PPMV-1 to chickens is still unclear. Herein, we reported the biological characterization of the isolated PPMV-1 from the diseased pigeons suspected to Newcastle Disease and studied its pathogenicity in SPF chickens. The phylogenetic tree and evolution distances revealed that the new isolate belonged to a VI.2.1.1.2.2 sub-genotype of NDV. Despite the cleavage motif of the F protein containing the 112RRQKR↓F117 sequence associated with virulent NDV strains, and the value of MDT and ICPI of the isolate showing mesogenic characteristics, the challenge trial showed that the isolate had weak pathogenicity to chickens while causing lesions in multiple tissues and organs in pigeons.

Contrasting effector profiles between bacterial colonisers of kiwifruit reveal redundant roles converging on PTI-suppression and RIN4.

Testing effector knockout strains of the Pseudomonas syringae pv. actinidiae biovar 3 (Psa3) for reduced in planta growth in their native kiwifruit host revealed a number of nonredundant effectors that contribute to Psa3 virulence. Conversely, complementation in the weak kiwifruit pathogen P.syringae pv. actinidifoliorum (Pfm) for increased growth identified redundant Psa3 effectors. Psa3 effectors hopAZ1a and HopS2b and the entire exchangeable effector locus (ΔEEL; 10 effectors) were significant contributors to bacterial colonisation of the host and were additive in their effects on virulence. Four of the EEL effectors (HopD1a, AvrB2b, HopAW1a and HopD2a) redundantly contribute to virulence through suppression of pattern-triggered immunity (PTI). Important Psa3 effectors include several redundantly required effectors early in the infection process (HopZ5a, HopH1a, AvrPto1b, AvrRpm1a and HopF1e). These largely target the plant immunity hub, RIN4. This comprehensive effector profiling revealed that Psa3 carries robust effector redundancy for a large portion of its effectors, covering a few functions critical to disease.

Characterization of an H7N9 Influenza Virus Isolated from Camels in Inner Mongolia, China.

The H7N9 subtype of influenza virus can infect birds and humans, causing great losses in the poultry industry and threatening public health worldwide. However, H7N9 infection in other mammals has not been reported yet. In the present study, one H7N9 subtype influenza virus, A/camel/Inner Mongolia/XL/2020 (XL), was isolated from the nasal swabs of camels in Inner Mongolia, China, in 2020. Sequence analyses revealed that the hemagglutinin cleavage site of the XL virus was ELPKGR/GLF, which is a low-pathogenicity molecular characteristic. The XL virus had similar mammalian adaptations to human-originated H7N9 viruses, such as the polymerase basic protein 2 (PB2) Glu-to-Lys mutation at position 627 (E627K) mutation, but differed from avian-originated H7N9 viruses. The XL virus showed a higher SA-α2,6-Gal receptor-binding affinity and better mammalian cell replication than the avian H7N9 virus. Moreover, the XL virus had weak pathogenicity in chickens, with an intravenous pathogenicity index of 0.01, and intermediate virulence in mice, with a median lethal dose of 4.8. The XL virus replicated well and caused clear infiltration of inflammatory cells and increased inflammatory cytokines in the lungs of mice. Our data constitute the first evidence that the low-pathogenicity H7N9 influenza virus can infect camels and therefore poses a high risk to public health. IMPORTANCE H5 subtype avian influenza viruses can cause serious diseases in poultry and wild birds. On rare occasions, viruses can cause cross-species transmission to mammalian species, including humans, pigs, horses, canines, seals, and minks. The H7N9 subtype of the influenza virus can also infect both birds and humans. However, viral infection in other mammalian species has not been reported yet. In this study, we found that the H7N9 virus could infect camels. Notably, the H7N9 virus from camels had mammalian adaption molecular markers, including altered receptor-binding activity on the hemagglutinin protein and an E627K mutation on the polymerase basic protein 2 protein. Our findings indicated that the potential risk of camel-origin H7N9 virus to public health is of great concern.

Identification, genome sequencing, and virulence variation analysis of MCRV-NH, an epidemic reovirus strain in cultured mud crab, Scylla paramamosain

Mud Crab Reovirus (MCRV) is a major pathogen of cultured mud crab Scylla paramamosain. Early studies showed that the mortality rate caused by MCRV was high. However, current studies show that MCRV has been widely present in cultured mud crab ponds, and the mortality rate has dramatically decreased, suggesting that it has become more infectious but less virulent. In this study, an epidemic MCRV strain named MCRV-NH was isolated from a representative farming areas of mud crabs to reveal the intrinsic molecular mechanism of the virulence variation of MCRV. Electron microscopy results showed that MCRV-NH was similar to the early reported MCRV or Scylla serrata reovirus (SsRV) in terms of morphology and structure. Viral infection experiments showed that no mud crab was dead during the infection period of 11 days even though MCRV-NH could rapidly proliferate in mud crabs at 21–23 °C, demonstrating that the mortality rate caused by MCRV-NH significantly decreased. Sequencing results of the MCRV-NH genome showed that eleven nucleotides were deleted in the sequencing region, and its nucleotide sequence identities with those of MCRV and SsRV were 99.43% and 99.33%, and the numbers of corresponding nucleotide mutations were 150 and 126, respectively. Evolutionary analysis showed that MCRV-NH belonged to the same species as MCRV and SsRV, and MCRV-NH should be a variant. In comparison with the open reading frames (ORFs) of MCRV and SsRV, the ORFs of MCRV-NH had no nucleotide deletions, but the numbers of nucleotide mutations were 100 and 123, and the numbers of amino acid mutations were 32 and 35, respectively. Eight mutated amino acids compared with the two reoviruses were located at the predicted active sites of the viral proteins. Among them, three mutations resulted in the generation of new phosphorylation sites, and two mutations led to the loss of the original phosphorylation sites. Meanwhile, a heptapeptide repeat sequence in VP9 disappeared, and a streptococcal histidine triad protein in VP6 and a Big-1 (bacterial Ig-like domain 1) domain in VP11 were generated due to key amino acid mutations in these viral proteins, which are involved in the infection and replication of MCRV. These changes in the active sites of the viral proteins may be responsible for the MCRV virulence variation. This study provided essential evidence to support the conclusion that MCRV-NH was a variant of MCRV with weaker pathogenicity and revealed the underlying possible molecular mechanism of the virulence variation of MCRV-NH.

Conversion of B.0 Lineage of Human Corona Virus (Covid-19) Into Notoriously Infecting Less Pathogenic and Immune Escape Omicron B.1.1.529.2.75.2 or BA.2.75.2 Variant

Human corona viruses appeared in December, 2019 at China and then within a span of 2 years such viruses (COVID-19) have gone deletions and mutations generating more infectious and death promoting variants like B.1.1.7 (Alpha) and B.1.617.2 (Delta) which were claimed half million deaths worldwide. The D614G and N501Y point mutations in spike protein appeared important for higher transmission and P4715L mutation in RdRP enzyme of ORF1ab polyprotein was also significant. However, since end of November 2021, an Omicron variant with 29 mutations on RBD domain of spike protein appeared in Africa which known as B.1.1.529 lineage which successively generated BA.1 and BA.2 variants. Omicron virus was highly infectious with immune escape properties but caused mild diseases. BA.2 omicron virus changed into BA.2.75.2 with more immune-escape and evasion properties. All omicron viruses had important 31ERS deletion on N-protein and 3675SGF deletion on nsp6 domain of ORF1ab which likely borrowed from B.1.1.7 by recombination. However, 69HV immune-escape deletion in B.1.1.7 and 157FR deletion in B.1.617.2 were not found in BA.2 variants. Its journey from BA.2.3, BA.2.9, BA.2.12, BA.2.48 etc and finally BA.2.75 variant was happened within a span of 10 months and BA.2.75.2 was highly spreading in India and USA recently. Although BA.2.75.2 variant has unique T607I and D1119N mutations in spike protein, other common N440K, G446S and L452R mutations were necessary for higher immune-escape and transmission including D614G and N501Y mutations. A G44R mutation in ORF3a protein also appeared specific for BA.2.75.2 and a 26 bases deletion in the 3’-UTR (5’-gag gcc acg cgg agt acg atc gag tg-3’) found in omicron viruses may be responsible for weak viral load and pathogenicity as such deletion was not found in deadly B.1.1.7 and B.1.617.2 variants. The genetic changes in BA.2.75 sub-variants as well as other emerging omicron variants like BA.4.6, BA.5.2.1, BE.1.1, BQ.1 and BF.7 also have been discussed.

SARS-CoV-2 ORF8 gene CAA=TAA and AAA=TAA Termination Codon Mutations found mostly in B.1.1.7 Variants was Independent of Popular L84S Point Mutations

Five VOCs of SARS-CoV-2 mainly caused million deaths worldwide and named as B.1.1.7 (U.K.), B.1.351 (South Africa), P.1 (Brazil), B.1.617.2 (India), and B.1.1.529 (Africa). In HIV mediated pathogenesis, small trans activator proteins (TAT, NEF, REV) modulate transcription of cellular genes. Similarly, preliminary reports indicated that corona virus ORF8 protein acts as histone mimics disrupting chromatic structure with many epigenetic changes and immune modulator functions. ORF8 protein had also some similarities to immunoglobulin domains and inhibited HMC-1 and IFN-beta functions. During evolution a 382-nucleotide deletion (∆382) in the ORF8 region of the corona virus genome leads to weak virus load and weak pathogenicity (accession no.MT374101). We BLAST searched deletion boundary and was selected few ORF8 protein truncated mutants. The C>T base change at 27972nt and another A>T base change at 28095nt created two termination codons (CAA=TAA and AAA=TAA) to produce 26AA and 67AA long ORF8 truncated proteins. Similar Blast-N search with oligonucleotides selected at the mutation boundaries gave many ORF8 mutants with distinct S24L, V32L, P38S, R52I, A65V, Y73C, L84S, K92E and V100L mutations with or without TAA termination mutations. Major mutations found in B.1.1.7 lineage which had spike 69HV and 145Y mutations and ORF1ab polyprotein 3675KSF deletion. However, one ORF8 mutant (accession no. OW221449) belongs to Omicron BA.2 variant with 24LPP spike deletion and others to Omicron BA.5 variants (accession nos. OP733645 and OP671680) with 24LPP and 69HV deletion in the spike protein. One termination codon mutant (accession no. OP711842) has also 63nt ORF7a/b deletions. Mutation did not change the hairpin structure in the ORF8 gene and ORF8 protein formed dimeric stable globular 3-D structure to interact with many host proteins. Clearly, generation of such abundant B.1.1.7 lineage ORF8 protein truncated mutants may be one of the causes for the extinction of Alpha variant of corona virus in 2021. Roles of ORF8 mutants as host proteins modulator were explained in light of other deletions and mutations in corona virus genome.

VmPma1 contributes to virulence via regulation of the acidification process during host infection in Valsa mali

Valsa mali is a destructive phytopathogenic fungus that mainly infects apple and pear trees. Infection with V. mali results in host tissue acidification via the generation of citric acid, which promote invasion. Here, two plasma membrane H+-ATPases, VmPma1 and VmPma2, were identified in V. mali. The VmPma1 deletion mutant (∆VmPma1) displayed higher intracellular acid accumulation and a lower growth rate compared to the wild type. In contrast, the VmPma2 deletion mutant (∆VmPma2) showed no obvious phenotypic differences. Meanwhile, loss of VmPma1, but not VmPma2, in V. mali led to a significant decrease in growth under acidic or alkaline conditions compared with WT. More importantly, ∆VmPma1 showed a greater reduction in ATPase hydrolase activity and acidification of the external environment, more sensitivity to abiotic stress, and weaker pathogenicity than ∆VmPma2. This evidence indicates that VmPma1 is the main gene of the two plasma membrane H+-ATPases. Transcriptomic analysis indicated that many metabolic processes regulated by VmPma1 are strictly pH-regulated. Besides, we identified two genes (named VmAgn1p and Vmap1) that contribute to the pathogenicity of V. mali by differentially regulating external acidification capacity. Overall, our findings show that VmPma1 plays a pivotal role in pathogenicity by affecting the acidification of V. mali.

The key amino acid sites 199–205, 269, 319, 321 and 324 of ALV-K env contribute to the weaker replication capacity of ALV-K than ALV-A

BackgroundAvian leukosis virus (ALV) is an infectious retrovirus, that mainly causes various forms of tumours, immunosuppression, a decreased egg production rate and slow weight gain in poultry. ALV consists of 11 subgroups, A–K, among which ALV-K is an emerging subgroup that has become prevalent in the past 10 years. Most ALV-K isolates showed weak replication ability and pathogenicity. In this study, the weak replication ability of ALV-K was explored from the perspective of the interaction between ALV-K gp85 and the Tva receptor.MethodsFourteen soluble recombinant ALV-A/K gp85 chimeric proteins were constructed by substituting the sequence difference regions (hr1, hr2 and vr3) of the ALV-A gp85 protein with the skeleton ALV-K gp85 protein for co-IP and competitive blocking tests.ResultsThe binding capacity of ALV-K gp85 to Tva was significantly weaker than that of ALV-A gp85 (P < 0.05) and the key amino acid sites 199–205, 269, 319, 321 and 324 of ALV-K env contributed to the weaker replication capacity of ALV-K than ALV-A.ConclusionsThis is the first study to reveal the molecular factors of the weak replication ability of ALV-K from the perspective of the interaction of ALV-K gp85 to Tva, providing a basis for further elucidation of the infection mechanism of ALV-K.

Non-hepatotropic viral hepatitis and its causative pathogens: The ongoing need for monitoring in children with severe acute hepatitis of unknown etiology.

Non-hepatotropic viral hepatitis and its causative pathogens: The ongoing need for monitoring in children with severe acute hepatitis of unknown etiology.

Identification and Characterization of Fungal Pathogens Associated with Boxwood Diseases in the Republic of Korea.

Boxwood is a representative ornamental shrub that is widely used in landscaping horticulture. After pruning, damaged leaves or stems of boxwoods are unavoidably vulnerable to infection by various plant pathogens. Several boxwood diseases caused by fungi, such as Volutella blight and Macrophoma leaf spot, have been reported worldwide including Republic of Korea. In this study, we isolated and identified fungal pathogens of boxwood diseases that occurred in Korea and characterized their morphological and taxonomic characteristics. Boxwood samples showing blight symptoms were collected in Seoul, Republic of Korea, and the putative fungal pathogens Pseudonectria buxi, P. foliicola, and Neofusicoccum buxi were successfully identified. Investigation of the morphological features of the field isolates, including mycelial growth and conidial morphology, and phylogenetic analysis of multiple DNA barcode loci revealed that there were some morphological and genetic variations among isolates, but all of the analyzed isolates were closely related to the corresponding reference strains. We also found that P. foliicola strains were more virulent than P. buxi, and the N. buxi strains isolated in this study were weak pathogens or saprophytes. The results of our study will contribute to the development of control strategies for boxwood diseases caused by fungi and accelerate research on the complex ecology of boxwood diseases.