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    昆虫和植物互作合辑Insect and Plant Interact

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    The influence of Tetranychus cinnabarinus-induced plant defense responses on Aphis gossypii development
    MA Guang-min, SHI Xue-yan, KANG Zhi-jiao, GAO Xi-wu
    2018, 17 (01): 164-172.   DOI: 10.1016/S2095-3119(17)61666-6
    Abstract585)      PDF in ScienceDirect      
    Carmine spider mites (Tetranychus cinnabarinus) and cotton aphids (Aphis gossypii) are both serious pests of cotton, and cause reductions in yields of this key agricultural crop.  In order to gain insights into how plant defense responses induced by one herbivore species affect the behavior and performance of another, we examined how infestation with T. cinnabarinus influences the development of A. gossypii using cotton as a model.  In this study, we measured the activities of several important biochemical markers and secondary metabolites in the leaves of cotton seedlings responding to infestation by T. cinnabarinus. Furthermore, the influences of T. cinnabarinus infestation on the development of A. gossypii in cotton were also examined.  Our data showed that the activities of several key defense enzymes, including phenylalanine ammonia-lyase (PAL), peroxidase (POD), lipoxygenase (LOX), and polyphenol oxidase (PPO), were substantially increased in cotton seedlings responding to spider mite infestation.  Further, the contents of gossypol and condensed tannins, key defensive compounds, were significantly enhanced in leaves of cotton seedlings following T. cinnabarinus infestation.  Moreover, the T. cinnabarinus-induced production of defense enzymes and secondary metabolites was correlated with infestation density.  The developmental periods of A. gossypii on cotton seedling leaves infested with T. cinnabarinus at densities of 10 and 15 individuals cm–2 were 1.16 and 1.18 times that of control, respectively.  Meanwhile, the mean relative growth rates of A. gossypii on cotton leaves infested with T. cinnabarinus at densities of 8, 10 and 15 individuals cm–2 were significantly reduced.  Therefore, these data suggested that the developmental periods of A. gossypii were significantly lengthened and the mean relative growth rates were markedly reduced when cotton aphids were reared on plants infested with high densities of spider mites.  This research sheds light on the role that inducible defense responses played in plant-mediated interspecific interactions between T. cinnabarinus and A. gossypii.
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    The impact of allelochemicals on the differential expression of symbiotic bacteria in cotton aphids
    LIU Ying, LIANG Ping-zhuo, LI Fen, MA Kang-sheng, CHEN Xue-wei, CHEN An-qi, LIANG Pei, GAO Xi-wu
    2018, 17 (08): 1815-1821.   DOI: 10.1016/S2095-3119(17)61838-0
    Abstract302)      PDF in ScienceDirect      
    Insects have developed a good adaptive mechanism in response to environmental stresses in the long-term evolution.
    They have developed a helpful metabolism system to resist plant allelochemicals. Insects also harbor different kinds of
    symbiotic bacteria, which provide them a competitive advantage. Here, using cotton aphid as an example, we investigated
    the effects of four plant allelochemicals on the differential expression of symbiotic bacteria based on transcriptome data.
    We also studied the composition of symbiotic bacteria and function on pathway level in three kinds of aphids. We found that
    the bacteria have a significant role in resisting the plant allelochemicals stress and host plant selection by aphids. These
    results should be useful to investigate the environmental adaption mechanism of aphids in the view of symbiotic bacteria.
    These results would offer a new insight for improving strategy of aphids and developing new pest control systems.
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    Selection and evaluation of potential reference genes for gene expression analysis in greenbug (Schizaphis graminum Rondani)
    ZHANG Bai-zhong, LIU Jun-jie, YUAN Guo-hui, CHEN Xi-ling, GAO Xi-wu
    2018, 17 (09): 2054-2065.   DOI: 10.1016/S2095-3119(18)61903-3
    Abstract414)      PDF in ScienceDirect      
    In order to precisely assess gene expression level, a suitable internal reference gene must be chosen to quantify real-time reverse transcription polymerase chain reaction (RT-qPCR) data.  For greenbug, Schizaphis graminum, a suitable reference gene for assessing the level of transcriptional expression of target genes has yet to be explored.  In our study, eight reference genes, elongation fator 1 beta (Ef1β), TATA box binding protein (TBP), alpha-tubulin (α-TUB), 18S ribosomal (18S), 28S ribosomal (28S), glyceraldehyde-3-phosphate (GAPDH), actin (ACT), and ribosomal protein L18 (RPL18) were evaluated in S. graminum at different developmental stages, tissues, and insecticide treatments.  To further explore whether these genes are suitable to serve as internal control, three software-based approaches (geNorm, BestKeeper, and NormFinder), ?Ct method, and one web-based comprehensive tool (RefFinder) were employed to analyze and rank the tested genes.  The optimal number of reference genes was determined using the geNorm program, and the suitability of particular reference genes was empirically validated according to normalized gene expression data of three target genes, heat shock protein gene (HSP70), cytocrome P450 gene (SgraCYP18A1), and glutathione S-transferase (GST).  We found that the most suitable reference genes varied considerably under different experimental conditions.  For developmental stages, α-TUB and 28S were the optimal reference genes; for different tissues, 18S and ACT were suitable reference genes; for insecticide treatments, 28S and α-TUB were suitable for normalizations of expression data.  In addition, 28S and α-TUB were the suitable reference gene as they had the most stable expression among different developmental stages, tissues and insecticide treatments.  This should be useful for the selection of the suitable reference genes to obtain reliable RT-qPCR data in the gene expression of S. graminum.
     
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    The biotypes and host shifts of cotton-melon aphids Aphis gossypii in northern China
    ZHANG Shuai, LUO Jun-yu, WANG Li, WANG Chun-yi, Lü Li-min, ZHANG Li-juan, ZHU Xiang-zhen, CUI Jin-jie
    2018, 17 (09): 2066-2073.   DOI: 10.1016/S2095-3119(17)61817-3
    Abstract462)      PDF in ScienceDirect      
    Aphis gossypii is a globally distributed species and therefore has a highly variable life cycle.  Populations of A. gossypii in northern China exhibit greater genotypic diversity and a broader host range, yet the details of life cycles of different biotypes is still unclear.  In this study, the Cytb and 16S gene regions of A. gossypii collected from 5 common summer hosts and 4 primary hosts were analyzed.  A total of 57 haplotypes were obtained from 1 046 individual A. gossypii sequences.  The sequence included 44 variable sites, 27 of which were parsimony informative sites and 17 of which were singleton variable sites.  The most frequent 3 haplotypes were found in 896 individuals, representing a total of 85.7% of all individuals and 36 haplotypes were found in 1 individual.  A neighbor-joining tree was constructed using 21 haplotypes that were found in more than 2 individuals.  Considering the individual host plant, 5 biotypes were identified.  Type 1 corresponded exactly to the cucurbit host-race and the other 4 biotypes were found as cotton host-races.  Type 3 was the most abundant biotype in cotton fields in northern China.
     
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    Molecular identification and enzymatic properties of laccase2 from the diamondback moth Plutella xylostella (Lepidoptera: Plutellidae)
    LIU Zhen-gang, WANG Huan-huan, XUE Chao-bin
    2018, 17 (10): 2310-2319.   DOI: 10.1016/S2095-3119(17)61764-7
    Abstract295)      PDF in ScienceDirect      
    Laccase (EC 1.10.3.2) is known to oxidize various aromatic and nonaromatic compounds via a radical-catalyzed reaction, which generally includes two types of laccase, Lac1 and Lac2. Lac1 oxidizes toxic compounds in the diet, and Lac2 is known to play an important role in melanizing the insect exoskeleton. In this study, we cloned and sequenced the cDNA of the diamondback moth, Plutella xylostella Lac2 (PxLac2), from the third instar larvae using polymerase chain reaction (PCR) and rapid amplification of cDNA ends techniques. The results showed that the full-length PxLac2 cDNA was 1 944 bp long and had an open reading frame of 1 794 bp. PxLac2 encoded a protein with 597 amino acids and had a molecular weight of 66.09 kDa. Moreover, we determined the expression levels of PxLac2 in different stages by quantitative PCR (qPCR). The results indicated that PxLac2 was expressed differently in different stages. We observed the highest expression level in pupae and the lowest expression level in fourth instar larvae. We also investigated the enzymatic properties of laccase, which had optimal activity at pH 3.0 and at 35°C. Under these optimal conditions, laccase had a Michaelis constant (Km) of 0.97 mmol L−1, maximal reaction speed (Vm) of 56.82 U mL−1, and activation energy (Ea) of 17.36 kJ mol−1 to oxidize 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid ammonium salt). Type II copper enhanced laccase activity below 0.8 mmol L−1 and reduced enzyme activity above 0.8 mmol L−1 with an IC50 concentration of 1.26 mmol L−1. This study provides insights into the biological function of laccase.
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    Transcriptome approach to understand the potential mechanisms of resistant and susceptible alfalfa (Medicago sativa L.) cultivars in response to aphid feeding
    TU Xiong-bing, ZHAO Hai-long, ZHANG Ze-hua
    2018, 17 (11): 2518-2527.   DOI: 10.1016/S2095-3119(17)61843-4
    Abstract367)      PDF in ScienceDirect      
    Plant breeding for resistance to agricultural pests is an essential element in the development of integrated crop management systems, however, the molecular and genetic mechanisms underlying resistance are poorly understood.  In this pilot study, we conducted a transcriptomic analysis of a resistant (R) and susceptible (S) variety of alfalfa, with (+A) or without (–A) aphids (totally four treatments).  We used the resistant cultivar Zhongmu 1 and the susceptible cultivar Soca.  A total of 3 549 mRNAs were differentially expressed, of which 1 738 up-regulated and 1 307 down-regulated genes were identified in S+A/S–A plants, while 543 up-regulated and 331 down-regulated genes were identified in the R+A/R–A plants.  KEGG analysis mapped 112 and 546 differentially expressed genes to 8 and 17 substantially enriched pathways for Zhongmu 1 and Soca, respectively.  Six shared pathways were linked to plant resistance traits, including phenylpropanoid biosynthesis associated with salicylic acid synthesis, and linoleic acid metabolism associated with both jasmonic acid and flavonoid biosynthesis.  Ultimately, we proposed a preliminary regulatory mechanism of alfalfa cultivar resistance response to aphids feeding based on transcriptome analyses and published documents.
     
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    Assessment of suitable reference genes for qRT-PCR analysis in Adelphocoris suturalis
    LUO Jing, MA Chao, LI Zhe, ZHU Bang-qin, ZHANG Jiang, LEI Chao-liang, JIN Shuang-xia, J. Joe Hull, CHEN Li-zhen
    2018, 17 (12): 2745-2757.   DOI: 10.1016/S2095-3119(18)61926-4
    Abstract239)      PDF (1312KB)(288)      
    Quantitative reverse transcription polymerase chain reaction (qRT-PCR) is the most commonly-used tool for measurement of gene expression, but its accuracy and reliability depend on appropriate data normalization with the use of one or more stable reference genes.  Adelphocoris suturalis is one of the most destructive pests of cotton, but until recently knowledge of its underlying molecular physiology had been hindered by a lack of molecular resources.  To facilitate research on this pest, we evaluated 12 common housekeeping genes studied in insects (GAPDH, ACT, βACT, TBP, SDH, βTUB, EF1γ, EF1α, EF1δ, RPL32, RPS15, and RPL27) for their expression stability in A. suturalis when subjected to various experimental treatments, including three biotic (developmental stage and sex, tissue type, and metathoracic scent gland for varying developmental stages and sexes) and one abiotic (RNA interference injection) conditions.  Four dedicated algorithms (ΔCt method, geNorm, BestKeeper and NormFinder) were used to analyze gene expression stability.  In addition, RefFinder provided an overall ranking of the stability/suitability of these candidates.  This study is the first to provide a comprehensive list of suitable reference genes for gene expression analyses in A. suturalis, which can serve to facilitate transcript expression study of related biological processes in this and related species.
     
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    Species-specific COI primers for rapid identification of a globally significant invasive pest, the cassava mealybug Phenacoccus manihoti Matile-Ferrero
    WANG Yu-sheng, TIAN Hu, WAN Fang-hao, ZHANG Gui-fen
    2019, 18 (5): 1042-1049.   DOI: 10.1016/S2095-3119(18)62043-X
    Abstract152)      PDF in ScienceDirect      
    The globally invasive cassava mealybug Phenacoccus manihoti Matile-Ferrero is a pernicious pest of cassava, and its recent introduction into Asia has raised considerable alarm.  To slow or prevent further invasion, an accurate, simple, and developmental-stage-independent detection method for P. manihoti is required.  In the present study, a PCR method based on a species-specific mitochondrial DNA cytochrome oxidase I (SS-COI) marker was developed for rapid identification of P. manihoti.  One pair of SS-COI primers (PMSSZW-1F and PMSSZW-1R) was designed based on sequence variations in the COI gene among P. manihoti and related mealybug species.  Specificity of the primer pair was validated on 21 closely related species.  Sensitivity tests were performed on four immature developmental stages and female adults.  Efficacy tests demonstrated that at the relatively low concentration of (135.2±14.7) pg μL–1 resuspended DNA, the specific fragment was detected in all replicates.  Furthermore, the SS-COI primer pair was assayed on three populations of P. manihoti from major exporting countries of cassava.  The PCR assay was proved to be a rapid, simple, and reliable molecular measure for the identification of P. manihoti.  This tool will be useful for quarantine, monitoring, and management of this invasive pest.
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    No evidence for an effect of Wolbachia on mtDNA variation and evolution in natural populations of Sesamia inferens (Lepidoptera: Noctuidae)
    TANG Xiao-tian, XU Jing, LU Ming-xing, DU Yu-zhou
    2019, 18 (5): 1050-1063.   DOI: 10.1016/S2095–3119(18)62019–2
    Abstract130)      PDF in ScienceDirect      
    Wolbachia are widespread maternally-inherited endosymbiotic bacteria that infect numerous arthropods.  This study represents a thorough survey of the Wolbachia infection patterns in the pink stem borer, Sesamia inferens (Walker), an important rice pest in China, based on nucleotide comparisons for the surface protein (wsp) and cell division protein (ftsZ) genes.  The effects of Wolbachia on mtDNA variation and evolution of S. inferens were also investigated.  Although we identified six genetically diverse strains, we found infections to be infrequent, with only 7.8% of hosts infected, and identified geographical differences in infection rates between southern and northern populations.  Nucleotide indexes (haplotype diversity (Hd), nucleotide diversity (π) and number of variable sites (S) of mtDNA in infected populations were not significantly lower or higher than that in the uninfected populations.  Furthermore, there was no association between Wolbachia infection status and phylogeny of mtDNA haplotypes.  Analysis of molecular variance (AMOVA) showed that significant differentiation mainly existed within groups rather than among the groups.  Additionally, using Tajima’s D and Fu’s F values, the mtDNA genes did not deviate significantly from neutral evolution.  Taken together these results indicate that currently there were no effects of Wolbachia infection on host mtDNA variation and evolution in S. inferens.
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    Identification and developmental expression of putative gene encoding juvenile hormone esterase (CpJHE-like) in codling moth, Cydia pomonella (L.)
    HUANG Cong, WU Qiang, JIANG Chun-yan, XING Long-sheng, SHI Guo-liang, ZHANG Bin, QIAN Wan-qiang, LI You-zhi, XI Yu, YANG Nian-wan, WAN Fang-hao
    2019, 18 (7): 1624-1633.   DOI: 10.1016/S2095-3119(19)62682-1
    Abstract172)      PDF in ScienceDirect      
    Juvenile hormone esterase (JHE) is a key enzyme for insects, playing an important role in the regulation of insect growth, development, diapause and reproduction.  We identified a complete putative JHE of Cydia pomonella (CpJHE-like) which is comprised of a 1 761 bp coding sequence (CDS) encoding 587 amino acid residues from the transcriptome data.  The deduced protein sequence of CpJHE-like showed the highest identity of 60.44% with the Adoxophyes honmai JHE (AhJHE) and the minimal identity of 25.81% with Aedes aegypti JHE (AaJHE).  CpJHE-like exhibited all the seven typical motifs of the functional JHEs and had the highly consistent tertiary structure with Manduca sexta JHE (MsJHE).  Phylogenetic analysis showed that the CpJHE-like was close to two JHEs from the family Tortricidae.  The CpJHE-like transcript level take a leap in the 3-day-old fifth instar larva, increased about 300-fold compared to the basal level.  Tissue-specific expression profile showed that the CpJHE-like transcript was expressed mainly in the fat body.  This study indicates that the CpJHE-like is the functional JHE, which may play vital roles in the development and reproduction of C. pomonella.
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    Transmission characteristics of Tomato chlorosis virus (ToCV) by Bemisia tabaci MED and its effects on host preference of vector whitefly
    WEI Ke-ke, LI Jie, DING Tian-bo, LIU Tong-xian, CHU Dong
    2019, 18 (9): 2107-2114.   DOI: 10.1016/S2095-3119(18)62080-5
    Abstract98)      PDF in ScienceDirect      
    The epidemiology of Tomato chlorosis virus (ToCV) in China is closely associated with its vector whitefly, Bemisia tabaci (Gennadius) MED.  However, the transmission characteristics of ToCV by B. tabaci MED remain poorly understood.  In this study, we analyzed: 1) the horizontal and vertical transmission of ToCV by B. tabaci MED whiteflies; 2) the acquisition of ToCV by male and female B. tabaci MED whiteflies after different feeding durations; 3) the transmission efficacy of viruliferous male and female B. tabaci MED whiteflies after different inoculation access periods (IAPs); 4) the retention of ToCV by viruliferous male and female B. tabaci MED whiteflies after a 48 h acquisition access period (AAP); and 5) the effects of ToCV on host choice of healthy or ToCV-infected tomato plant of viruliferous and non-viruliferous B. tabaci MED at different time points.  Our results showed that: 1) viruliferous males could not transfer ToCV to non-viruliferous females, and vice versa, viruliferous females could not pass on ToCV to non-viruliferous males.  ToCV could not be detected in the F1 generation adults; 2) ToCV could be detected within 4.0% of females or males after a 20 min AAP; 3) ToCV could be detected in 33.3% of tomato plants inoculated by 10 viruliferous males or females with IAPs of 20 or 30 min; 4) the maximum retention time in females was 7 and 5 days in males; and 5) non-viruliferous B. tabaci MED did not show a preference for ToCV-infected tomato plants or healthy tomato plants.  However, viruliferous B. tabaci MED whiteflies did prefer to settle on healthy tomato plants over ToCV-infected tomato plants.  These findings will be helpful to better understand the epidemiology of the recently emerged plant virus, ToCV, in tomato fields in China.
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    Molecular cloning, expression profiling and RNA interference of a vitellogenin gene from Harmonia axyridis (Coleoptera: Coccinellidae)
    LIANG Chao, LIU Ting-hui, HAN Shi-peng, HE Yun-zhuan
    2019, 18 (10): 2311-2320.   DOI: 10.1016/S2095-3119(18)62103-3
    Abstract67)      PDF in ScienceDirect      
    In this study, the Harmonia axyridis vitellogenin gene 2 (HmVg2) sequence was identified from transcriptomic databases of female adult H. axyridis and cloned into pMD18-T vector.  The HmVg2 gene was 5 460 bp in length, and formed with an open reading frame (ORF) of 5 361 nucleotides (GenBank accession no. KY794939).  The putative molecular weight of the primary HmVg2 protein was 203.459 kDa and the predicted isoelectric point (pI) was 8.59.  HmVg2 contained a signal peptide, vitellogenin N-terminal (vitellogenin-N) domain, domain of unknown function 1943 (DUF1934) domain and von Willebrand factor type D (VWD) domain.  The developmental expression profiling showed that HmVg2 was extremely highly expressed in female insects, but was expressed at lower levels in male insects.  In female insects, HmVg2 was mainly expressed in the wing and fat body.  The double-stranded RNA-HmVg2/-GFP was injected into H. axyridis, and qRT-PCR results showed that the HmVg2 gene was specifically silenced.  The eggs laid during the first five days and the hatching rate of eggs was lower than controls after dsHmVg2 injection.  This investigation demonstrated that the HmVg2 gene plays an important role in H. axyridis reproduction and enriches the function of the insect vitellogenin gene.
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    LncRNAs are potentially involved in the immune interaction between small brown planthopper and rice stripe virus
    CHEN Meng-yao, YE Wan-yi, XIAO Hua-mei, LI Mei-zhen, CAO Zheng-hong, YE Xin-hai, ZHAO Xian-xin, HE Kang, LI Fei
    2019, 18 (12): 2814-2822.   DOI: 10.1016/S2095-3119(19)62569-4
    Abstract82)      PDF in ScienceDirect      
    Small brown planthopper (SBPH, Laodelphax striatellus Fallén) is an important vector of major crop pathogen rice stripe virus (RSV).  Controlling SBPH population is an efficient approach to control RSV.  Long non-coding RNAs (lncRNA) have been reported to block virus replication in hosts.  However, the function of lncRNAs in RSV infection and replication is still unknown.  Here, we aimed to study regulatory mechanisms of lncRNA in an immune system during RSV infection.  First, lncRNA genes were predicted from SBPH transcriptomes using a bioinformatics pipeline based on characteristics of lncRNA.  We identified 4 786 lncRNA genes corresponding to 5 790 transcripts in SBPH from an RNA-Seq dataset of 15 transcriptomes.  Differential expression analysis indicated that 3, 11, and 25 lncRNA genes were highly expressed in gut, salivary gland, and ovary, respectively, of viruliferous SBPH (Student’s t-test, P<0.05).  We randomly selected eight lncRNAs for expression validation using quantitative real-time PCR, confirming the differential expression of these lncRNAs between viruliferous and non-viruliferous SBPH.  In summary, we present evidence that the expression of lncRNA genes was induced by RSV infection, suggesting that RSV might be involved in the antivirus immune system in SBPH and participate in regulating the RSV replication mechanism.  These data provide helpful information for future investigations of the interaction between lncRNA and RSV. 
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    Identification and characterization of a TLR13 gene homologue from Laodelphax striatellus involved in the immune response induced by rice stripe virus
    ZHOU Xue, HU Jia, FU Mei-li, JIN Ping, ZHANG Yun-ye, XIANG Ying, LI Yao, MA Fei
    2020, 19 (1): 183-192.   DOI: 10.1016/S2095-3119(19)62795-4
    Abstract163)      PDF in ScienceDirect      
    Toll-like receptors (TLRs) are the critical superfamily homologues that initiate sensing of the invasion of pathogens by the Toll pathway.  As one of several intracellular nucleic acid-sensing TLRs, TLR13 is activated by an unmethylated motif present in the large ribosomal subunit of bacterial RNA.  However, little attention has been paid to the function of TLR13 gene homologue from Laodelphax striatellus (designated as LsToll-13) in the immune response to rice stripe virus (RSV).  Herein, LsToll-13 was cloned and characterized using RACE-PCR.  Phylogenetic analysis showed that LsToll-13 was clustered with the TLR13 from six insects.  Real-time PCR analysis demonstrated that the expression level of LsToll-13 was significantly reduced in L.?striatellus with RSV infection compared with that in the naive strain.  When the expression of LsToll-13 was significantly up-regulated at 6 h after bacterial infection, the expression of ribonucleoprotein (RNP) indicated that the RSV titer in the host insect was significantly suppressed.  Upon knockdown of LsToll-13, using RNA interference (RNAi) in L.?striatellus, the expression level of RNP was significantly increased with enhanced RSV accumulation, suggesting that LsToll-13 potentially protects L.?striatellus from RSV infection.  Taken together, our results indicated that LsToll-13 might be involved in the immune response of L.?striatellus to RSV infection, and provided a new insight into further elucidating the molecular mechanisms of complex pathogen-host interactions and integrative pest management.
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    Exploiting push-pull strategy to combat the tea green leafhopper based on volatiles of Lavandula angustifolia and Flemingia macrophylla
    HAN Shan-jie, WANG Meng-xin, WANG Yan-su, WANG Yun-gang, CUI Lin, HAN Bao-yu
    2020, 19 (1): 193-203.   DOI: 10.1016/S2095-3119(19)62778-4
    Abstract134)      PDF in ScienceDirect      
    Thirteen volatile compounds were identified from Flemingia macrophylla plants.  Eight major components significantly attracted the tea green leafhoppers, Empoasca flavescens F.  Based on their relative abundances, following synthetic blends were made for field experiments: 1) eight-component-attractant blend included Z-3-hexen-1-ol, Z-3-hexenyl acetate, Z-ocimene, MeSA, Z-3-hexenyl butyrate, dodecane, hexadecane and nonanal at 10, 10, 1, 11, 2, 6, 2 and 4 mg mL–1 in n-hexane, respectively; 2) four-component-attractant blend #1 contained hexadecane, Z-3-hexenyl acetate, Z-3-hexen-1-ol and nonanal at 2, 10, 10 and 4 mg mL–1 in n-hexane, respectively; 3) four-component-attractant blend #2 contained hexadecane, Z-3-hexenyl acetate, Z-3-hexen-1-ol and MeSA at 2, 10, 10 and 11 mg mL–1 in n-hexane, respectively.  Thymol and 1-methoxy-4-methyl-2-(1-methylethyl)-benzene, identified from Lavandula angustifolia aeration samples, significantly repelled the leafhopper as strong repellents when tested alone or in combination at 10 mg mL–1.  For field bioassays, each attractant lure was attached to a bud green sticky board hung from a bamboo stick at above tea plant level for catching the leafhoppers, whereas the repellent dispenser was tied to a tea branch inside tea clump for pushing the leafhoppers away from tea clumps.  The results showed that the eight-component-attractant blend caught similar numbers of the leafhopper as did the four-component-attractant blend #1 at about 53–79 leafhoppers/trap/day, which were significantly higher than those on the hexane-control bud green sticky boards.  Average leafhopper catches from un-baited sticky boards were about 51–73 leafhoppers/trap/day when pushed by the repellents placed inside tea plants, with the two-component-repellent blend being more effective than their single components.  When the two-component-repellent blend was further tested with the three attractant blends in a push-pull fashion, average trap catches ranged from 62 to 92 leafhoppers/trap/day.  Control efficacy on the leafhoppers within the push-pull zones increased progressively from day 1 (43%) to day 5 (73%).  This push-pull approach might have a great potential as a green control strategy for combating the tea green leafhoppers. 
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    Two farnesyl pyrophosphate synthases, GhFPS1–2, in Gossypium hirsutum are involved in the biosynthesis of farnesol to attract parasitoid wasps
    ZHANG Hong, HUANG Xin-zheng, JING Wei-xia, LIU Dan-feng, Khalid Hussain DHILOO, HAO Zhi-min, ZHANG Yong-jun
    2020, 19 (9): 2274-2285.   DOI: 10.1016/S2095-3119(20)63203-8
    Abstract131)      PDF in ScienceDirect      
    Sesquiterpenoids play an import role in the direct or indirect defense of plants.  Farnesyl pyrophosphate synthases (FPSs) catalyze the biosynthesis of farnesyl pyrophosphate, which is a key precursor of farnesol and (E)-β-farnesene.  In the current study, two FPS genes in Gossypium hirsutum, GhFPS1 and GhFPS2, were heterologously cloned and functionally characterized in a greenhouse setting.  The open reading frames for full-length GhFPS1 and GhFPS2 were each 1 029 nucleotides, and encoded two proteins of 342 amino acids with molecular weights of 39.4 kDa.  The deduced amino acid sequences of GhFPS1–2 showed high identity to FPSs of other plants.  Quantitative real-time PCR analysis revealed that GhFPS1 and GhFPS2 were highly expressed in G. hirsutum leaves, and were upregulated in methyl jasmonate (MeJA)-, methyl salicylate (MeSA)- and aphid infestation-treated cotton plants.  The recombinant proteins of either GhFPS1 or GhFPS2 plus calf intestinal alkaline phosphatase could convert geranyl diphosphate (GPP) or isopentenyl diphosphate (IPP) to one major product, farnesol.  Moreover, in electrophysiological response and Y-tube olfactometer assays, farnesol showed obvious attractiveness to female Aphidius gifuensis, which is an important parasitic wasp of aphids.  Our findings suggest that two GhFPSs are involved in farnesol biosynthesis and they play a crucial role in indirect defense of cotton against aphid infestation.
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    Molecular characteristics and temperature tolerance function of the transient receptor potential in the native Bemisia tabaci AsiaII3 cryptic species
    JI Shun-xia, SHEN Xiao-na, LIANG Lin, WANG Xiao-di, LIU Wan-xue, WAN Fang-hao, Lü Zhi-chuang
    2020, 19 (11): 2746-2757.   DOI: 10.1016/S2095-3119(20)63226-9
    Abstract85)      PDF in ScienceDirect      
    Insects are poikilothermic animals, and temperature is one of the most important abiotic factors affecting their spread and distribution.  For example, differences in thermal tolerance may underlie the significant differences in geographical distributions between the native AsiaII3 and invasive MED (Mediterranean) cryptic Bemisia tabaci species in China.  Transient receptor potential (TRP) channels are key components of the insect temperature perception system and act as molecular thermometers since they can be activated by specific changes in temperature.  In this study, we cloned and characterized the AsiaII3 BtTRP gene and revealed its functions in the response to thermal stress.  The full-length cDNA of BtTRP was 3 821 bp, with a 3 501-bp open reading frame encoding a 132.05-kDa protein.  Comparing the deduced amino acid sequences of AsiaII3 BtTRP and MED TRP revealed five amino acid differences.  In situ hybridization indicated that BtTRP might be widely expressed throughout the AsiaII3 adult body.  BtTRP mRNA expression reached the highest levels after exposure to mild thermal stimuli (12 and 35°C), showing that BtTRP expression can be induced by temperature stress.  Furthermore, the thermal tolerance of AsiaII3 after BtTRP dsRNA feeding was significantly lower than that of the control.  Taken together, the present study highlights the importance of TRP channels for B.?tabaci thermal resistance, and allows us to infer that the differences in amino acids between AsiaII3 and MED might cause the differences in thermal tolerance of these two cryptic species.  This study provides a new direction for investigating geographic distribution differences between invasive and native insects.
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    Pancreatic triglyceride lipase is involved in the virulence of the brown planthopper to rice plants
    YUAN Long-yu, HAO Yuan-hao, CHEN Qiao-kui, PANG Rui, ZHANG Wen-qing
    2020, 19 (11): 2758-2766.   DOI: 10.1016/S2095-3119(20)63188-4
    Abstract79)      PDF in ScienceDirect      
    The brown planthopper (BPH), Nilaparvata lugens, an important rice insect pest, can enhance its virulence to BPH-resistant rice within as short a span as several generations.  Here, we cloned a pancreatic triglyceride lipase (PTL) gene (NlPTL) in N. lugens, and found that its mRNA level was higher in the high virulence population (fed on variety Rathu Heenati, P-RH) than in the low virulence population (fed on variety Taichung Native 1, P-TN1).  Knocking down NlPTL caused BPH individuals to spend more time in non-penetration and the pathway phases and less time feeding on the phloem of rice plants; these changes consequently decreased food intake, lipid content, survival rate, and fecundity in the insects.  These findings reveal for the first time that PTL in BPH is involved in its virulence to rice plants.
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    Cloning and functional characterization of two peptidoglycan recognition protein isoforms (PGRP-LC) in Bactrocera dorsalis (Diptera: Tephritidae)
    WEI Dong, WANG Zhe, XU Hui-qian, NIU Jin-zhi, WANG Jin-jun
    2020, 19 (12): 3025-3034.   DOI: 10.1016/S2095-3119(20)63202-6
    Abstract61)      PDF in ScienceDirect      
    The innate immune system of insects is the front line of self-defense against pathogen invasion.  Peptidoglycan recognition proteins (PGRPs) are important components and play key roles in insect immune systems by recognizing peptidoglycan (PGN) in bacterial cell walls.  We characterized two isoforms of the PGRP-LC gene, BdPGRP-LCa and BdPGRP-LCb, from Bactrocera dorsalis (Hendel), an important fruit and vegetable pest worldwide.  These two isoforms contain an open reading frames of 1 668 bp and 1 731 bp, encoding a protein of 555 and 576 amino acids, respectively.  Quantitative real-time PCR results showed that both transcripts were prominently expressed in midgut and fat body of B. dorsalis adult.  Inoculation of pathogens showed that both isoforms actively responded to Escherichia coli PGN.  We also observed a light response to Staphylococcus aureus PGN.  Upon Beauveria bassiana inoculation, the expression of BdPGRP-LCa was enhanced, but the expression of BdPGRP-LCb was suppressed.  Suppression of both transcripts by RNA interference led to increased mortality of flies challenged by E. coli, indicating that the two isoforms are involved in sensing Gram-negative bacterial infections.
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