In JoVE (1)

Other Publications (18)

Articles by Pengjun Xu in JoVE

 JoVE Immunology and Infection

Protocols for Investigating the Host-tissue Distribution, Transmission-mode, and Effect on the Host Fitness of a Densovirus in the Cotton Bollworm

1State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, 2Tobacco Research Institute, Chinese Academy of Agricultural Sciences, 3Crop and Environment Sciences, Harper Adams University

JoVE 55534

Other articles by Pengjun Xu on PubMed

Molecular Cloning and Characterization of Four Heat Shock Protein Genes from Macrocentrus Cingulum (Hymenoptera: Braconidae)

Molecular Biology Reports. Jun, 2010  |  Pubmed ID: 19685164

The full-length cDNA sequences of four HSPs genes were amplified from Macrocentrus cingulum, respectively named Mchsp90, Mchsc70, Mchsp70 and Mchsp23.8. These four genes were submitted to GenBank database and assigned to GenBank accession number: EU570065, EU585780, EU585779 and EU624206. Phylogenetic analysis indicated that the Mchsp90, Mchsc70 and Mchsp70 were located in cytoplasm. Moreover, the Mchsc70 was a member of heat shock cognate protein 70 while the Mchsp70 was a member of heat shock inducible 70. The expression analysis indicated that these four genes were differentially expressed at larval, pupal and adult stages. Under normal conditions, the mRNA levels of Mchsp90 and Mchsc70 were higher than Mchsp70 while Mchsp23.8 was decreased during aging. The mRNA levels of these four genes could be up-regulated by heat shock besides Mchsp70 and Mchsp23.8 could be increased more dramatically than Mchsp90 and Mchsc70. These results suggested that Mchsp90, Mchsp70 and Mchsp23.8 might have dual functions under normal and heat shock conditions while Mchsp70 and Mchsp23.8 might supply more important protection under heat shock.

Determination and Study on Dissipation of 1-naphthylacetic Acid in Garlic and Soil Using High Performance Liquid Chromatography-tandem Mass Spectrometry

Food and Chemical Toxicology : an International Journal Published for the British Industrial Biological Research Association. Nov, 2011  |  Pubmed ID: 21864633

A simple, quick and reliable analytical method for the determination of 1-naphthylacetic acid in garlic and soil has been developed in this study. The residual levels and dissipation rates of 1-naphthylacetic acid in garlic and soil were determined by high performance liquid chromatography-tandem mass spectroscopy (HPLC-MS/MS). The limit of quantification (LOQ) of the developed method was 0.005 mg/kg. The half-lives of 1-naphthylacetic acid in garlic plants and soil were 0.80-1.4 days and 0.94-2.0 days, respectively. The final residues of 1-naphthylacetic acid in garlic, garlic sprout and soil could not be detected and were all below 0.05 mg/kg (the MRL of EU). Results of the ultimate residues in garlic and soil showed that this pesticide is safe to be used under the recommended dosages.

Complete Genome Sequence of a Monosense Densovirus Infecting the Cotton Bollworm, Helicoverpa Armigera

Journal of Virology. Oct, 2012  |  Pubmed ID: 22966197

Densoviruses (DNVs) infecting arthropods are members of the family Parvoviridae. Here we report the complete genome sequence of a novel DNV with a monosense genome that infects cotton bollworms (Helicoverpa armigera), named HaDNV-1. Alignment and phylogenetic analysis revealed that HaDNV-1 showed high identity with the genus Iteravirus.

Levels, Profiles and Source Identification of PCDD/Fs in Farmland Soils of Guiyu, China

Chemosphere. May, 2013  |  Pubmed ID: 23466087

The present study finished the first comprehensive survey of polychlorinated dibenzo-p-dioxin and dibenzofurans (PCDD/Fs) in farmland soils of Guiyu, China. Guiyu was a major electronic wastes (EWs) dismantling area, but primitive and crude EWs disposal manner had led to severe PCDD/Fs pollution there. Twenty-three farmland soil samples covering the entire Guiyu region were analyzed. Toxic equivalent quantities (I-TEQs) of soils in EWs disposal areas were 5.7-57pg TEQ g(-1), and the total concentrations of tetra- to octa-homologues were 2816-17738pgg(-1). The SL district was a heavily contaminated area, and the neighboring SMP town was influenced by Guiyu. EWs disposal might be the source of PCDD/Fs. The homologue profiles were of three types, representing different disposal manner of EWs. Tetrachlorodibenzo-p-dioxins (TCDDs) and octachlorodibenzo-p-dioxin (OCDD) could be used as indicators for source identification, open thermal disposal of EWs was inclined to lead to formation of TCDDs, OCDD was a product of non-thermal processes.

The Evolution and Expression of the Moth Visual Opsin Family

PloS One. 2013  |  Pubmed ID: 24205129

Because visual genes likely evolved in response to their ambient photic environment, the dichotomy between closely related nocturnal moths and diurnal butterflies forms an ideal basis for investigating their evolution. To investigate whether the visual genes of moths are associated with nocturnal dim-light environments or not, we cloned long-wavelength (R), blue (B) and ultraviolet (UV) opsin genes from 12 species of wild-captured moths and examined their evolutionary functions. Strong purifying selection appeared to constrain the functions of the genes. Dark-treatment altered the levels of mRNA expression in Helicoverpa armigera such that R and UV opsins were up-regulated after dark-treatment, the latter faster than the former. In contrast, B opsins were not significantly up-regulated. Diel changes of opsin mRNA levels in both wild-captured and lab-reared individuals showed no significant fluctuation within the same group. However, the former group had significantly elevated levels of expression compared with the latter. Consequently, environmental conditions appeared to affect the patterns of expression. These findings and the proportional expression of opsins suggested that moths potentially possessed color vision and the visual system played a more important role in the ecology of moths than previously appreciated. This aspect did not differ much from that of diurnal butterflies.

Simple and Rapid Determination of PCDD/Fs in Flue Gases from Various Waste Incinerators in China Using DR-EcoScreen Cells

Chemosphere. May, 2014  |  Pubmed ID: 24377450

In developing countries such as China, there is a strong need for simple and rapid bioassays for the determination of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in environmental samples; i.e., flue gas and fly ash from waste incinerators. In this study, we applied the DR-EcoScreen cell (DR-cell) assay to determination of PCDD/Fs in 78 flue gas samples obtained from various waste incinerators in China between 2009 and 2011. The flue gas samples were obtained from four kinds of incinerators, classified into hazardous, medical and municipal-solid waste, and iron ore sintering, and the flue gas extracts were cleaned up using an SPD-600 automated-sample preparation device for DR-cell assay. The PCDD/Fs values obtained from the DR-cell assay were compared with those obtained from conventional high resolution gas chromatography-high resolution mass spectrometry (HRGC-HRMS) analysis. The bioanalytical equivalent (BEQ) values obtained from the DR-cell assay were very closely correlated with the international toxicity equivalent (I-TEQ) values from HRGC-HRMS analysis (r2=0.98, n=78), while the BEQ values were 5.52-fold higher than the I-TEQ values, as the PCDFs, which account for 80% of the total I-TEQ value, were overestimated by DR cell-assay. Therefore, we multiplied the BEQ values from the DR-cell assay by a conversion coefficient (0.181, the reciprocal of 5.52), and could approximate the TEQ values from the HRGC-HRMS analysis. These results suggest that the DR-cell assay combined with SPD-600 cleanup provides a promising method for the simple and rapid screening of PCDD/Fs levels in flue gas samples, such as those from various waste incinerators in China.

Densovirus is a Mutualistic Symbiont of a Global Crop Pest (Helicoverpa Armigera) and Protects Against a Baculovirus and Bt Biopesticide

PLoS Pathogens. Oct, 2014  |  Pubmed ID: 25357125

Mutualistic associations between symbiotic bacteria and their hosts are common within insect systems. However, viruses are often considered as pathogens even though some have been reported to be beneficial to their hosts. Herein, we report a novel densovirus, Helicoverpa armigera densovirus-1 (HaDNV-1) that appears to be beneficial to its host. HaDNV-1 was found to be widespread in wild populations of H. armigera adults (>67% prevalence between 2008 and 2012). In wild larval populations, there was a clear negative interaction between HaDNV-1 and H. armigera nucleopolyhedrovirus (HaNPV), a baculovirus that is widely used as a biopesticide. Laboratory bioassays revealed that larvae hosting HaDNV-1 had significantly enhanced resistance to HaNPV (and lower viral loads), and that resistance to Bacillus thuringiensis (Bt) toxin was also higher at low doses. Laboratory assays indicated that the virus was mainly distributed in the fat body, and could be both horizontally- and vertically-transmitted, though the former occurred only at large challenge doses. Densovirus-positive individuals developed more quickly and had higher fecundity than uninfected insects. We found no evidence for a negative effect of HaDNV-1 infection on H. armigera fitness-related traits, strongly suggesting a mutualistic interaction between the cotton bollworm and its densovirus.

Molecular Characterization and Expression Profiles of Polygalacturonase Genes in Apolygus Lucorum (Hemiptera: Miridae)

PloS One. 2015  |  Pubmed ID: 25955307

Polygalacturonase (PG) is an enzyme in the salivary glands of piercing-sucking mirid bugs (Hemiptera: Miridae) that plays a key role in plant feeding and injury. By constructing a full-length cDNA library, we cloned and characterized 14 PG genes from the salivary glands of Apolygus lucorum, a pestiferous mirid bug in cotton, fruit trees and other crops in China. BLAST search analysis showed that the amino acid sequences deduced from transcripts of the PG genes were closely related to PGs from other mirid bugs. Phylogenetic analysis showed that the PGs of mirid bugs had six main branches, PG1-PG6 (Genbank accession numbers: KF881899~KF881912). We investigated the mRNA expression patterns of the A. lucorum PG genes using real-time PCR. All 14 PGs were expressed significantly higher in the salivary glands than in other tissues (head, thorax, abdomen, leg and wing). For eggs and nymphs, the expression levels of these PGs were much higher in the 5th instar stage than in the egg, and 1st and 3rd instar stages. The PG expression levels in 1-day-old adults were very low, and increased in 5, 20 and 30-day-old adults. Additionally, PG expression levels were generally similar between males and females. The possible physiological functions of PGs in A. lucorum were discussed.

Simultaneous Determination of Three Alternative Flame Retardants (dechlorane Plus, 1,2-bis(2,4,6-tribromophenoxy) Ethane, and Decabromodiphenyl Ethane) in Soils by Gas Chromatography-high Resolution Mass Spectrometry

Talanta. Nov, 2015  |  Pubmed ID: 26452921

A gas chromatography-high resolution mass spectrometry (GC-HRMS) method has been developed for the simultaneous determination of three alternative flame retardants, dechlorane plus (DP), 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE), and decabromodiphenyl ethane (DBDPE) in soils. The soil samples were extracted by accelerated solvent extraction, followed by purification with concentrated sulfuric acid partitioning combined with acid-base silica gel column separation. The gas chromatography featured with a thermostable capillary column of short length and a thin stationary phase was operated in pulse injection mode. A double-focusing magnetic sector high resolution mass spectrometer with electron impact ionization was used for quantification of the analytes. The method detection limits were 0.27-0.33 pg for DPs, 0.41 pg for BTBPE, and 36 pg for DBDPE. The mean recoveries for DPs, BTBPE, and DBDPE in spiked soils were 88-107%, 78-97%, and 74-113%, respectively, with relative standard deviations ranging from 5.2% to 18%. The recoveries of (13)C-labeled standards for DPs, BTBPE, and DBDPE in soil samples were 45-110%, 67-118%, and 27-82%, respectively. These results met the acceptable range of labeled standards for analysis of polybrominated diphenyl ethers as specified by the USEPA 1614 method.

Characterization and Distribution Analysis of a Densovirus Infecting Myzus Persicae Nicotianae (Hemiptera: Aphididae)

Journal of Economic Entomology. Apr, 2016  |  Pubmed ID: 26791818

Densoviruses (DVs) are a group of viruses that contain a linear single-stranded DNA genome between 4–6 kb in length. Herein, we report a DV with a 5,480-nt genome, isolated from tobacco aphid (Myzus persicae nicotianae Blackman), named MpnDV. Unlike the genome of M. persicae densovirus (MpDV), which possesses five open reading frames (ORFs), the genome of MpnDV contains four putative ORFs—the nonstructural protein 1 (NS1) and NS2 from MpnDV are 98- and 52-amino acids longer than those of MpDV, respectively, at the N-terminus, and the capsid proteins (VP) are 102 amino acids longer at the C-terminus than those of MpDV. Mapping of the MpnDV transcripts by RACE method indicated that the ORF of NS2 started at nt 340 and the right two putative ORFs were combined together by deleting two introns, one of 95 bp located at nt 2,932–3,026 and the other of 145 bp located at nt 4,715–4,859, suggesting transcript mapping was necessary for analyzing of genome organization. Alignment analysis indicated that MpnDV shows 97% sequence identity with MpDV, and that the shortened ORFs resulted from nucleotide indels, suggesting MpnDV and MpDV were two isolates of the same virus. Thus, MpnDV and MpDV clustered together in a tree-based analysis. The prevalence of MpnDV infection in wild populations of tobacco aphids differed among 29 locations; 34% of the 622 individuals sampled were positive. The genome organization, transcript strategy, and widespread distribution in wild populations suggest that MpnDV might possess a biological function different from that of MpDV.

Occurrence and Impact of Polychlorinated Dibenzo-p-dioxins/dibenzofurans in the Air and Soil Around a Municipal Solid Waste Incinerator

Journal of Environmental Sciences (China). Jun, 2016  |  Pubmed ID: 27266321

To assess the influence of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) on the environment in the vicinity of municipal solid waste incinerators (MSWIs), we determined the levels of PCDD/Fs in air and soil samples collected around a MSWI, which is the largest in China. The International Toxicity Equivalency Quantity (I-TEQ) concentrations of PCDD/Fs in air samples were from 0.0300 to 1.03pgI-TEQ/m(3) (0.445-13.6pg/m(3)), with an average of 0.237pgI-TEQ/m(3), while in soil samples they ranged from 0.520 to 3.40pgI-TEQ/g (2.41-88.7pg/g) with an average of 1.49pgI-TEQ/g. The concentrations of PCDD/Fs in air and soil samples were comparable to other areas, and PeCDFs were the dominant contributors, which was different from stack gas homologue patterns. Multivariate statistical analysis showed that PCDD/Fs emission from the MSWI did not directly affect the profiles of PCDD/Fs in air and soils, so that vehicles and unidentified emission sources should be considered. The daily inhalation levels of PCDD/Fs for children (0.0110 to 0.392pgI-TEQ/(kg·day) and adults (0.00600 to 0.221pgI-TEQ/(kg·day) near the MSWI were lower than the tolerable daily intake of 1.00 to 4.00pg WHO-TEQ/(kg·day), but in winter the values were higher than in summer. These results can be used as basic data for assessing the risk of PCDD/Fs exposure in residents living around this MSWI, and more monitoring programs and studies should be carried out around MSWIs.

Polycyclic Aromatic Hydrocarbon Concentrations, Compositions, Sources, and Associated Carcinogenic Risks to Humans in Farmland Soils and Riverine Sediments from Guiyu, China

Journal of Environmental Sciences (China). Oct, 2016  |  Pubmed ID: 27745654

The concentrations of 16 priority polycyclic aromatic hydrocarbons (PAHs) were measured in 23 farmland soil samples and 10 riverine sediment samples from Guiyu, China, and the carcinogenic risks associated with PAHs in the samples were evaluated. Guiyu is the largest electronic waste (EW) dismantling area globally, and has been well known for the primitive and crude manner in which EWs are disposed, such as by open burning and roasting. The total PAH concentrations were 56-567 ng/g in the soils and 181-3034 ng/g in the sediments. The Shanglian and Huamei districts were found to be more contaminated with PAHs than the north of Guiyu. The soils were relatively weakly contaminated but the sediments were more contaminated, and sediments in some river sections might cause carcinogenic risks to the groundwater system. The PAHs in the soils were derived from combustion sources, but the PAHs in the sediments were derived from both combustion and petroleum sources.

Functional Opsin Retrogene in Nocturnal Moth

Mobile DNA. 2016  |  Pubmed ID: 27777631

Retrotransposed genes are different to other types of genes as they originate from a processed mRNA and are then inserted back into the genome. For a long time, the contribution of this mechanism to the origin of new genes, and hence to the evolutionary process, has been questioned as retrogenes usually lose their regulatory sequences upon insertion and generally decay into pseudogenes. In recent years, there is growing evidence, notably in mammals, that retrotransposition is an important process driving the origin of new genes, but the evidence in insects remains largely restricted to a few model species.

A Novel Single-stranded RNA Virus in Nesidiocoris Tenuis

Archives of Virology. Apr, 2017  |  Pubmed ID: 28004253

The complete genome sequence of a novel single-stranded RNA virus in Nesidiocoris tenuis was determined by RNA-seq and rapid amplification of cDNA ends (RACE) methodologies and was named N. tenuis virus 1. The genomic RNA was 3970 nucleotides (nt) in length and contained two putative open reading frames (ORFs). ORF1 encoded a polypeptide with 283 amino acids containing a viral (superfamily 1) RNA helicase (Hel) domain, and ORF2 encoded a polypeptide with 294 amino acids containing an RNA-dependent RNA polymerase (RdRP) domain. Phylogenetic analysis using the deduced amino acid sequences indicated that the N. tenuis virus 1 clustered with Blackford virus; however, the low bootstrap values and unique genomic structure suggested that the virus is a prototype of a new type of unclassified viruses. The prevalence of N. tenuis virus 1 infection in field populations of N. tenuis differed between three locations, with 28.32% of the 113 sampled individuals testing positive for the virus.

The Genome Sequence of a Novel RNA Virus in Adelphocoris Suturalis

Archives of Virology. Jan, 2017  |  Pubmed ID: 28108803

The complete genome of a novel virus found in Adelphocoris suturalis was determined by RNA-seq and named Adelphocoris suturalis-associated virus 1 (ASV1). ASV1 has a single-stranded RNA genome of 10,845 nucleotides in length and contains five putative open reading frames (ORFs). ORF1 encodes a polypeptide of 2592 amino acids (aa) and contains four conserved domains: a viral RNA methyltransferase domain, an FtsJ-like methyltransferase domain, a viral RNA helicase domain and an RNA-dependent RNA polymerase domain. ORF2, ORF3, ORF4 and ORF5 encode polypeptides of 190, 461, 103 and 159 aa, respectively, of which only ORF5 contains a conserved domain, the Tobacco mosaic virus-coat superfamily. Phylogenetic analysis with the deduced amino acid sequences indicated that ASV1 clusters with the Drosophila-related Boutonnet virus. The similar genomic structure and high bootstrap value identified in the maximum-likelihood tree suggest that ASV1 (possibly alongside Boutonnet virus) could be considered the prototype of a new taxon of unclassified insect viruses. The prevalence of ASV1 infection in wild populations of A. suturalis was at a low level (6.60%, 14 positives from 212 samples).

Characterization of a Novel Member of Genus Iflavirus in Helicoverpa Armigera

Journal of Invertebrate Pathology. Mar, 2017  |  Pubmed ID: 28163012

The cotton bollworm, Helicoverpa armigera, is one of the most important agricultural pests of many economic crops worldwide. Herein, we found a novel single-strand RNA virus by RNA-Seq and Polymerase Chain Reaction (PCR) method in H. armigera named Helicoverpa armigera iflavirus (HaIV), which possessed a genome with 10,017 nucleotides in length and contained a single large open reading frame (ORF) encoding a putative polyprotein of 3021 amino acids with a predicted molecular mass of 344.16kDa and a theoretical isoelectric point (pI) of 6.45. The deduced amino acid sequence showed highest similarity (61.0%) with the protein of Lymantria dispar Iflavirus 1. Phylogenetic analysis with putative RdRp amino acid sequences indicated that the virus clustered with members of the genus Iflavirus. The virus was mainly distributed in the fat body of its host and was found to be capable of both horizontal and vertical transmission. The efficiency of perorally horizontal transmission was dose dependent (100% infection rate with a viral dose of 10(8)copies/μl) while vertical transmission efficiency was found to be relatively low (<28.57%). These results suggest that we have found a novel member of genus Iflavirus in H. armigera.

Structure and Transcription of the Helicoverpa Armigera Densovirus (HaDV2) Genome and Its Expression Strategy in LD652 Cells

Virology Journal. Feb, 2017  |  Pubmed ID: 28173863

Densoviruses (DVs) are highly pathogenic to their hosts. However, we previously reported a mutualistic DV (HaDV2). Very little was known about the characteristics of this virus, so herein we undertook a series of experiments to explore the molecular biology of HaDV2 further.

Structural Proteins of Helicoverpa Armigera Densovirus 2 Enhance Transcription of Viral Genes Through Transactivation

Archives of Virology. Feb, 2017  |  Pubmed ID: 28210815

Herein, we report the identification of putative promoters for the non-structural proteins (NS) and capsid structural proteins (VP) of Helicoverpa armigera densovirus (HaDV2) as well as a potential mechanism for how these promoters might be regulated. For the first time, we report that VP is able to transactivate the VP promoter and, to a lesser degree, the NS promoter in densoviruses. In addition to this, another promoter-like sequence designated P2, when co-transfected with the VP gene, enhanced luciferase activity by approximately 35 times compared to a control. This suggests that there are two promoters for VP in HaDV2 and that the VP of parvoviruses might play a more important role in viral transcription than previously appreciated.

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