Neuropeptides are crucial in regulation of a rich variety of developmental,physiological,and behavioral functions throughout the life cycle of insects.Using an integrated approach of multiomics,we identified neuropept...Neuropeptides are crucial in regulation of a rich variety of developmental,physiological,and behavioral functions throughout the life cycle of insects.Using an integrated approach of multiomics,we identified neuropeptide precursors in the greater wax moth Galleria mellonella,which is a harmful pest of honeybee hives with a worldwide distribution.Here,a total of 63 and 67 neuropeptide precursors were predicted and annotated in the G.mellonella genome and transcriptome,in which 40 neuropeptide precursors were confirmed in the G.mellonella peptidome.Interestingly,we identified 12 neuropeptide precursor genes present in G.mellonella but absent in honeybees,which may be potential novel pesticide target sites.Honeybee hives were contaminated with heavy metals such as lead,enabling its bioaccumulation in G.mellonella bodies through the food chain,we performed transcriptome sequencing to analyze the effects of Pb stress on the mRNA expression level of G.mellonella neuropeptide precursors.After treatment by Pb,the expression of neuropeptide F1 was found to be significantly downregulated,implying that this neuropeptide might be associated with responding to the heavy metal stress in G.mellonella.This study comprehensively identified neuropeptide precursors in G.mellonella,and discussed the effects of heavy metals on insect neuropeptides,with the example of G.mellonella.The results are valuable for future elucidation of how neuropeptides regulate physiological functions in G.mellonella and contribute to our understanding of the insect's environmental plasticity and identify potential new biomarkers to assess heavy metal toxicity in insects.展开更多
Lipid and sugar homeostasis is critical for insect development and survival.In this study,we characterized an acetyl coenzyme A carboxylase gene in Blattella germanica(BgACC)that is involved in both lipogenesis and su...Lipid and sugar homeostasis is critical for insect development and survival.In this study,we characterized an acetyl coenzyme A carboxylase gene in Blattella germanica(BgACC)that is involved in both lipogenesis and sugar homeostasis.We found that BgACC was dominantly expressed in the fat body and integument,and was significantly upregulated after molting.Knockdown of BgACC in 5th-instar nymphs did not affect their normal molting to the next nymphal stage,but it caused a lethal phenotype during adult emergence.BgACC-RNA interference(RNAi)significantly downregulated total free fatty acid(FFA)and triacylglycerol(TAG)levels,and also caused a significant decrease of cuticular hydrocarbons(CHCs).Repression of BgACC in adult females affected the development of oocytes and resulted in sterile females,but BgACC-RNAi did not affect the reproductive ability of males.Interestingly,knockdown of BgACC also changed the expression of insulin-like peptide genes(BglLPs),which mimicked a physiological state of high sugar uptake.In addition,BgACC was upregulated when B.germanica were fed on a high sucrose diet,and repression of BgACC upregulated the expression of the glycogen synthase gene(BgGlyS).Moreover,BgACC-RNAi increased the circulating sugar levels and glycogen storage,and a longevity assay suggested that BgACC was important for the survival of B.germanica under conditions of high sucrose uptake.Our results confirm that BgACC is involved in multiple lipid biogenesis and sugar homeostasis processes,which further modulates insect reproduction and sugar tolerance.This study benefits our understanding of the crosstalk between lipid and sugar metabolism.展开更多
In a tritrophic context of plant-insect-entomopathogen,plants play important roles in modulating the interaction of insects and their pathogenic viruses.Currently,the influence of plants on the transmission of insect ...In a tritrophic context of plant-insect-entomopathogen,plants play important roles in modulating the interaction of insects and their pathogenic viruses.Currently,the influence of plants on the transmission of insect viruses has been mainly studied on baculoviruses and some RNA viruses,whereas the impact of plants on other insect viruses is largely unknown.Here,we identified a new densovirus infecting the green peach aphid Myzus persicae and tested whether and how host plants influence the transmission of the aphid densovirus.The complete single-stranded DNA genome of the virus,M.persicae densovirus 2,is 5727 nt and contains inverted terminal repeats.Transcription and phylogenetic analysis indicated that the virus was distinct from other a few identified aphid densoviruses.The virus abundance was detected highly in the intestinal tract of aphids,compared with the lower level of it in other tissues including head,embryo,and epidermis.Cabbage and pepper plants had no obvious effect on the vertical transmission and saliva-mediated horizontal transmission of the virus.However,the honeydew-mediated horizontal transmission among aphids highly depended on host plants(65%on cabbages versus 17%on peppers).Although the virus concentration in the honeydew produced by aphids between 2 plants was similar,the honeydew production of the infected aphids reared on peppers was dramatically reduced.Taken together,our results provide evidence that plants influence the horizontal transmission of a new densovirus in an aphid population by modulating honeydew secretion of aphids,suggesting plants may manipulate the spread of an aphid-pathogenic densovirus in nature.展开更多
The parasitoids in the genera of Encarsia and Eretmocerus （Hymenoptera： Aphelinidae） are important biological control agents of whiteflies, and some of them not only parasitize hosts but also kill them with strong ...The parasitoids in the genera of Encarsia and Eretmocerus （Hymenoptera： Aphelinidae） are important biological control agents of whiteflies, and some of them not only parasitize hosts but also kill them with strong host-feeding capacity. Two whitefly parasitoid species, Encarsia sophia and Eretmocerus melanoscutus were examined to determine if mating and host density affected their host feeding and parasitism. The whitefly host, Bemisia tabaci, was presented to these two wasp species in densities of 10, 20, 30, 40, 50 and 60 third-instar nymphs per clip cage. Mated whitefly parasitoid females fed on more hosts than unmated females under a range of host densities （under all six host densities for En. sophia; under the densities of 40 nymphs or more for Er. melanoscutus）. Meanwhile, mated females parasitized more whitefly nymphs than unmated females under all host densities for both species. With increase of host density, mated or unmated Er. melanoscutus females killed more hosts by host feeding and parasitism. Mated En. sophia females killed more hosts by host feeding with increase of host density, whereas unmated females did not parasitze whitefly nymphs at all. Our results suggest that only mated female parasitoids with host-feeding behavior should be released in crop systems to increase their bio-control efficiency.展开更多
Fitness and efficacy of Encarsia sophia （Girault ＆ Dodd） （Hymenoptera： Aphelinidae） as a biological control agent was compared on two species of whitefly （Hemiptera： Aleyrodidae） hosts, the relatively smaller...Fitness and efficacy of Encarsia sophia （Girault ＆ Dodd） （Hymenoptera： Aphelinidae） as a biological control agent was compared on two species of whitefly （Hemiptera： Aleyrodidae） hosts, the relatively smaller sweetpotato whitefly, Bemisia tabaci （Gennadius） biotype ＇B＇, and the larger greenhouse whitefly, Trialeurodes vaporariorum （Westwood）. Significant differences were observed on green bean （Phaseolus vulgaris L.） in the laboratory at 27 ± 2℃, 55% 4- 5% RH, and a photoperiod of 14 ： 10 h （L ： D）. Adult parasitoids emerging from T. vaporariorum were larger than those emerging from B. tabaci, and almost all biological parameters of E. sophia parasitizing the larger host species were superior except for the developmental times of the parasitoids that were similar when para- sitizing the two host species. Furthermore, parasitoids emerging from T. vaporariorum parasitized more of these hosts than did parasitoids emerging from B. tabaci. We conclude that E. sophia reared from larger hosts had better fitness than from smaller hosts. Those from either host also preferred the larger host for oviposition but were just as effective on smaller hosts. Therefore, larger hosts tended to produce better parasitoids than smaller hosts.展开更多
The fall armyworm(FAW),Spodoptera frugiperda,is a destructive pest native to America and has recently become an invasive insect pest in China.Because of its rapid spread and great risks in China,understanding of FAW g...The fall armyworm(FAW),Spodoptera frugiperda,is a destructive pest native to America and has recently become an invasive insect pest in China.Because of its rapid spread and great risks in China,understanding of FAW genetic background and pesticide resistance is urgent and essential to develop effective management strategies.Here,we assembled a chromosome-level genome of a male FAW(SFynMstLFR)and compared re-sequencing results of the populations from America,Africa,and China.Strain identification of 163 individuals collected from America,Africa and China showed that both C and R strains were found in the American pop-ulations,while only C strain was found in the Chinese and African populations.Moreover,population geno-mics analysis showed that populations from Africa and China have close relationship with significantly genetic differentiation from American populations.Taken toge-ther,FAWs invaded into China were most likely origi-nated from Africa.Comparative genomics analysis displayed that the cytochrome p450 gene family is extremely expanded to 425 members in FAW,of which 283 genes are specific to FAW.Treatments of Chinese populations with twenty-three pesticides showed the variant patterns of transcriptome profiles,and several detoxification genes such as AOX,UGT and GST spe-cially responded to the pesticides.These findings will be useful in developing effective strategies for manage-ment of FAW in China and other invaded areas.展开更多
The green peach aphid, Myzus persicae Sulzer （Hemiptera, Aphididae）, is an important cosmopolitan pest. Real time qRT-PCR has been used for target gene expression analysis on M. persicae. Using real time qRT-PCR, th...The green peach aphid, Myzus persicae Sulzer （Hemiptera, Aphididae）, is an important cosmopolitan pest. Real time qRT-PCR has been used for target gene expression analysis on M. persicae. Using real time qRT-PCR, the expression levels are normalized on the basis of the reliable reference genes. However, to date, the stability of available reference genes has been insufficient. In this study, we evaluated nine candidate reference genes from M. persicae under diverse experimental conditions. The tested candidate genes were comprehensively ranked based on five alternative methods （RefFinder, geNorm, Normfinder, BestKeeper and the comparative ACt method）. 18s, Actin and ribosomal protein L27 （L27） were recommended as the most stable reference genes for M. persicae, whereas ribosomal protein L27 （L27） was found to be the least stable reference genes for abiotic studies （photoperiod, temperature and insecticide susceptibility）. Our finding not only sheds light on establishing an accurate and reliable normalization of real time qRT-PCR data in M. persicae but also lays a solid foundation for further studies of M. persicae involving RNA interference and functional gene research.展开更多
Insect neuropeptides play an important role in regulating physiological functions such as growth,development,behavior and reproduction.We identified temperaturesensitive neuropeptides and receptor genes of the cotton ...Insect neuropeptides play an important role in regulating physiological functions such as growth,development,behavior and reproduction.We identified temperaturesensitive neuropeptides and receptor genes of the cotton whitefly,Bemisia tabaci.We identified 38 neuropeptide precursor genes and 35 neuropeptide receptors and constructed a phylogenetic tree using additional data from other insects.As temperature adaptability enables B.tabaci to colonize a diversity of habitats,we performed quantitative polymerase chain reaction with two temperature stresses(low=4℃ and high=40℃)to screen for temperature-sensitive neuropeptides.We found many neuropeptides and receptors that may be involved in the temperature adaptability of B.tabaci.This study is the first to identify B.tabaci neuropeptides and their receptors,and it will help to reveal the roles of neuropeptides in temperature adaptation of B.tabaci.展开更多
Cuticular hydrocarbons form a barrier that protects terrestrial insects from water loss via the epicuticle.Lipophorin loads and transports lipids,including hydrocarbons,from one tissue to another.In some insects,the l...Cuticular hydrocarbons form a barrier that protects terrestrial insects from water loss via the epicuticle.Lipophorin loads and transports lipids,including hydrocarbons,from one tissue to another.In some insects,the lipophorin receptor(LpR),which binds to lipophorin and accepts its lipid cargo,is essential for female fecundity because it mediates the incorporation of lipophorin by developing oocytes.However,it is unclear whether LpR is involved in the accumulation of cuticular hydrocarbons and its precise role in aphid reproduction remains unknown.We herein present the results of our molecular characterization,phylogenetic analysis,and functional annotation of the pea aphid(Acyrthosiphon pisum)LpR gene(ApLpR).This gene was transcribed throughout the A.pisum life cycle,but especially during the embryonic stage and in the abdominal cuticle.Furthermore,we optimized the RHA interference(RNAi)parameters by determining the ideal dose and duration for gene silencing in the pea aphid.We observed that the RNAi-based ApLpR suppression significantly decreased the internal and cuticular hydrocarbon contents as well as adult fecundity.Additionally,a deficiency in cuticular hydrocarbons increased the susceptibility of aphids to desiccation stress,with decreased survival rates under simulated drought conditions.Moreover,ApLpR expression levels significantly increased in response to the desiccation treatment.These results confirm that ApLpR is involved in transporting hydrocarbons and protecting aphids from desiccation stress.Furthermore,this gene is vital for aphid reproduction.Therefore,the ApLpR gene of A.pisum may be a novel RNAi target relevant for insect pest management.展开更多
Development, survivorship, pupal weight, oviposition, and life table parameters of the oriental tobacco budworm, Helicoverpa assulta Guenée, were evaluated in the laboratory on an artificial diet, pepper （Capsic...Development, survivorship, pupal weight, oviposition, and life table parameters of the oriental tobacco budworm, Helicoverpa assulta Guenée, were evaluated in the laboratory on an artificial diet, pepper （Capsicumfrutescens L.）, and tobacco （Nicotiana tobacum L.）. We found that the average developmental time of immature stages was longest on tobacco （36.2 d）, intermediate on pepper （34.4 d）, and shortest on artificial diet （33.5 d）. Immature survival from egg to pupa varied from 31% on tobacco, 43% on pepper, and 74% on artificial diet. Pupal weight ranged from 197.4 mg/pupa on tobacco, 233.1 mg/pupa on pepper and 253.4 mg/pupa on artificial diet. The average numbers of eggs laid by adults reared as larvae on the artificial diet, pepper, or tobacco were 614, 421 and 334 eggs/female, respectively. Numbers of remaining eggs in ovaries of the adult females reared as larvae on the artificial diet, pepper, or tobacco were 16, 26, and 42 eggs/female, respectively. The longevity of adult females developed from larvae reared on the three diets was not significantly different, whereas the longevity of male adults from the larvae reared on artificial diet was longer （16.8 d） than that for males reared on tobacco （13.8 d） and pepper （13.3 d）. The intrinsic, finite, gross, and net rates of increase were highest for females reared as larvae on artificial diet, lowest for females emerging from larvae reared on tobacco, and intermediate for females emerging from larvae reared on pepper. Generation times and doubling time of H. assulta were shortest for larvae fed artificial diet, intermediate from larvae reared on pepper, and longest from larvae reared on tobacco. We concluded that the artificial diet was the most suitable larval diet ofH. assulta followed by pepper, and tobacco.展开更多
We conducted three experiments for management of Bemisia tabaci （Gennadius） biotype＇ B＇ on tomatoes under greenhouse conditions： （i） vertically placing yellow sticky cards either parallel or perpendicular to to...We conducted three experiments for management of Bemisia tabaci （Gennadius） biotype＇ B＇ on tomatoes under greenhouse conditions： （i） vertically placing yellow sticky cards either parallel or perpendicular to tomato rows at a rate of 1 per 3-m row; （ii） releasing Eretmocerus sp. nr. rajasthanicus once at 30 adults/m2 in the high whitefly density greenhouses （〉 10 adults/plant）, or twice at 15 adults/m2 at a 5-day interval in the low whitefly density greenhouses （〈 10 adults/plant）; and （iii） using combinations of yellow sticky cards that were placed vertically parallel to tomato rows and parasitoids released once at 30/m2 in high whitefly density greenhouses or twice at 15/m2 at a 5-day interval in low whitefly density greenhouses. Our data show that yellow sticky cards trapped B. tabaci adults and significantly reduced whitefly populations on tomato. The yellow sticky cards that were placed parallel to tomato rows caught significantly more whitefly adults than those placed perpendicular to tomato rows on every sampling date. In the treatment where parasitoids were released once at 30/m2 in high whitefly density greenhouses, the number of live whitefly nymphs were reduced from 4.6/leaf to 2.9/leaf in 40 days as compared with those on untreated plants on which live whitefly nymphs increased from 4.4/leaf to 8.9/leaf. In the treatment where parasitoids were released twice at 15/m2 in low whitefly density greenhouses, the numbers of live nymphs ofB. tabaci on tomato leaves were reduced from 2.1/leaf to 1.7/leaf in 20 days as compared with those on untreated plants on which numbers of live nymphs ofB. tabaci increased from 2.2/leaf to 4.5/leaf. In the treatment of yellow sticky cards and parasitoid release once at 30/m2 in high whitefly density greenhouses, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 7.2/leaf to 1.9/leaf, and in the treatment of yellow sticky cards and parasitoid release twice at 15/m2 at a 5-day interval at low whitefly density, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 2.5/leaf to 0.8/leaf; whereas the numbers of live nymphs of B. tabaci on untreated plants increased from 4.4/leaf to 8.9/leaf. An integrated program for management of B. tabaci on greenhouse vegetables by using yellow sticky cards, parasitoids and biorational insecticides is discussed.展开更多
Southwestern corn borer （SWCB, Diatraea grandiosella） and fall armyworm （FAW, Spodopterafrugiperda） are major pests of sorghum in the southern United States. Host plant resistance is a desirable means for reducing...Southwestern corn borer （SWCB, Diatraea grandiosella） and fall armyworm （FAW, Spodopterafrugiperda） are major pests of sorghum in the southern United States. Host plant resistance is a desirable means for reducing plant damage and yield losses from both insects. In this study, we evaluated 12 sorghum lines for whorl-stage resistance to leaf-feeding SWCB and FAW in greenhouse and laboratory bioassays. Differential plant responses were detected against the two insects. Among 12 lines tested, CM1821, Della and PI196583 were resistant to both insects, while BTx2752 was largely susceptible. Line R.09110 was resistant to SWCB, but susceptible to FAW, whereas Redbine-60 was suscep- tible to SWCB, but not to FAW. In addition, we quantified various chemical components in the plants and determined their association with insect resistance. Tannin and chloro- phyll in leaves did not show any significant correlation with resistance to either insects, but contents of soluble protein in general were negatively correlated with resistance to both insects. Endogenous soluble sugar and dhurrin were only positively correlated with resistance to SWCB, but not with FAW resistance. To gain some molecular insight into resistance mechanism of sorghum to SWCB, we performed qPCR reactions for key genes encoding enzymes involved in dhurrin and jasmonic acid （JA） biosynthesis on selected resistant or susceptible lines. Although these genes were rapidly and strongly induced by insect feeding in all lines, the observed resistance is likely explained by higher constitutive dhurrin contents in some resistant lines and higher basal JA biosynthesis in others. Our results suggest that sorghum utilizes multiple strategies to defend itself against SWCB.展开更多
The functional response of Cydonia vicina nilotica Muls. （Coleoptera： Coccinellidae） to six densities of Aphis craccivora Koch （Homoptera： Aphididae） nymphs on broad bean （Viciafaba Linn.） was investigated in ...The functional response of Cydonia vicina nilotica Muls. （Coleoptera： Coccinellidae） to six densities of Aphis craccivora Koch （Homoptera： Aphididae） nymphs on broad bean （Viciafaba Linn.） was investigated in the laboratory. A linear relationship between the rate of consumption and prey density was observed with r^2 values between 0.58 and 0.97. Plotting prey density against prey killed by four larval instars, and adult males and females of C. vicina nilotica fit well with the type Ⅱ model of Holling＇ s disc equation. Adult females consumed the highest number of prey, followed by fourth instars and adult males. Based on the functional response data, the model predicts a maximum of 144.9, 116.3, 86.2, 80.0, 72.5 and 20.0 nymphs to be consumed per day by an individual adult female, fourth instar, adult male, third, second and first instars, respectively. The differences in the responses of the predator to aphid densities are discussed.展开更多
Natal rearing experience of animals may affect their behaviors,such as habitat selection and oviposition decision.As part of the overall fitness of insect parasitoids, successful host discrimination (distinguishing pa...Natal rearing experience of animals may affect their behaviors,such as habitat selection and oviposition decision.As part of the overall fitness of insect parasitoids, successful host discrimination (distinguishing parasitized hosts from unparasitized hosts) is of paramount importance.In this study we examined whether and how parasitoids' natal rearing experience would affect their host discrimination ability according to host availability.We established separate colonies ofAphidius gifuensis Ashmead by continual rearing on two hosts,Sitobion avenae E and Myzuspersicae (Suzler),and quantified self superparasitism and self superparasitism versus parasitism ratio for the four:combinations ofparasitoid colonies and host species (S.aveane and M.persicae)at four host densities (30,50,100 or 150 per plant).Results showed that self superparasitism ofM.persicae by A.gifuensis reared on S.avenae was significantly higher than by those reared on M.persicae,no matter whether the host densities were 30,50,100 or 150.Aphidius gifuensis reared on M.persicae significantly superparasitized more S.avenae than those reared on S.aveane only when host density was 30.Self superparasitism versus parasitism ratio of A.gifuensis from both colonies was always lower on natal hosts than on new hosts,and the difference was more pronounced as the host density decreased.These results suggested that natal rearing effects is important on host discrimination and oviposition decision of the parasitoid A.gifuensis.These effects promoted the parasitoid's host adaptation and made them confer greater fitness.展开更多
The impacts of potato psyllid （Bactericera cockerelli） feeding on potato foliage on the free amino acids （FAAs） composition in potato leaf and tubers were determined under greenhouse conditions. The free amino aci...The impacts of potato psyllid （Bactericera cockerelli） feeding on potato foliage on the free amino acids （FAAs） composition in potato leaf and tubers were determined under greenhouse conditions. The free amino acids in plant extracts were separated by high-performance liquid chromatography, and in both leaf and tuber samples, at least 17 FAAs were detected. Psyllid feeding significantly changed the levels of several FAAs in both leaf and tuber samples. The concentration of leucine increased 1.5-fold, whereas that of serine and proline increased 2- and 3-fold, respectively. In contrast, the concentrations ofglutamic acid, aspartic acid and lyscine were significantly reduced by 42.0%, 52.1% and 27.5%, respectively. There were also significant changes in the levels of FAAs in the Zebra chip （ZC） infected tubers compared with the healthy tubers, and the levels of six of the FAAs increased, and the levels of nine of the FAAs decreased. The results from this study indicate that potato psyllid causes major changes in free amino acid composition of plant tissues, and this change in plant metabolism may contribute to the plant stress as indicated by increased levels of proline in the leaves and hence promoting the development of plant diseases such as ZC disease.展开更多
Water retention is critical for physiological homeostasis and survival in terrestrial insects. While deposition of hydrocarbons on insect cuticles as a key measure for water conservation has been extensively investiga...Water retention is critical for physiological homeostasis and survival in terrestrial insects. While deposition of hydrocarbons on insect cuticles as a key measure for water conservation has been extensively investigated, we know little about other mechanisms for preventing water loss in insects. Here, we report two fatty acid synthetic genes that are independent of hydrocarbon production but crucial for water retention in the German cockroach Blattella germanica (L.). First, an integument enriched fatty acid elongase gene (BgElo1) was identified as a critical gene for desiccation resistance in B. germanica;however, knockdown of BgElo1 surprisingly failed to cause a decline in cuticular lipids. In addition, RNA interference (RNAi)-knockdown of an upstream fatty acid synthase gene (BgFas3) showed a similar phenotype, and transmission electron microscopy analysis revealed that BgFas3- or BgElo1-RNAi did not affect cuticle architecture. Bodyweight loss test showed that repression of BgFas3 and BgElo1 significantly increased the weight loss rate, but the difference disappeared when the respiration was closed by freeze killing the cockroaches. A water immersion test was performed, and we found that BgFas3- and BgElo1-RNAi made it difficult for cockroaches to recover from drowning, which was supported by the upregulation of hypoxia-related genes after a 10-h recovery from drowning. Moreover, a dyeing assay with water-soluble Eosin Y showed that this was caused by the entry of water into the respiratory system. Our research suggests that BgFas3 and BgElo1 are required for both inward and outward waterproofing of the respiratory system. This study benefits the understanding of water retention mechanisms in insects.展开更多
Microbial abundance and diversity of different life stages （fourth instar larvae, pupae and adults） of the diamondback moth, Plutella xylostella L., collected from field and reared in laboratory, were investigated u...Microbial abundance and diversity of different life stages （fourth instar larvae, pupae and adults） of the diamondback moth, Plutella xylostella L., collected from field and reared in laboratory, were investigated using bacteria culture-dependent method and PCR-DGGE analysis based on the sequence of bacteria 16S rRNA V3 region gene. A large quantity of bacteria was found in all life stages ofP. xylostella. Field population had higher quantity of bacteria than laboratory population, and larval gut had higher quantity than pupae and adults. Culturable bacteria differed in different life stages ofP. xylostella. Twenty-five different bacterial strains were identified in total, among them 20 strains were presented in larval gut, only 8 strains in pupae and 14 strains in adults were detected. Firmicutes bacteria, Bacillus sp., were the most dominant species in every life stage. 15 distinct bands were obtained from DGGE electrophoresis gel. The sequences blasted in GenBank database showed these bacteria belonged to six different genera. Phylogenetic analysis showed the sequences of the bacteria belonged to the Actinobacteri, Proteobacteria and Firmicutes. Serratia sp. in Proteobacteria was the most abundant species in larval gut. In pupae, unculturable bacteria were the most dominant species, and unculturable bacteria and Serratia sp. were the most dominant species in adults. Our study suggested that a combination of molecular and traditional culturing methods can be effectively used to analyze and to determine the diversity of gut microflora. These known bacteria may play important roles in development of P. xylostella.展开更多
Most female herbivores ensure to lay eggs where their offspring can develop successfully. The oviposition preferences of females affect strategies in pest management. In this study, the performance of two cohorts of T...Most female herbivores ensure to lay eggs where their offspring can develop successfully. The oviposition preferences of females affect strategies in pest management. In this study, the performance of two cohorts of Trichoplusia ni larvae on cabbage and cotton （after they had been transferred from their original host plants） were investigated. The preferences of female moth ovipositing and larval feeding on these two host plants were observed. The results indicated that plants significantly affected oviposition preference of the female adults and development and survival of larvae of T. ni. All females preferred to lay eggs on cabbage than cotton regardless from which host they originated. The detrimental effects of cotton on the development and survival of T. ni larvae originated from cabbage （CaTn） increased with the increase of the larval age when they were transferred. In addition, the host plant change did not significantly affect the development and survival of larvae of T. ni originating from cotton （CoTn）. Larvae of CaTn preferred cabbage plants as compared to cotton plants, whereas larvae of CoTn did not show a significant choice. Although the adult females preferred laying eggs on cabbage, they did not show preferences between cotton and cabbage in a Y-tube olfactometer test. The hypothesis of oviposition preference and performance of larvae was supported by the results of CaTn, whereas they not supported by those from CoTn. Based on these results, the strategy to manage this serious pest was discussed.展开更多
A recombinant Helicoverpa armigera nucleopolyhedrovirus （HearNPV） ex- pressing the insect-selective neurotoxin （RjAalTjO from Cuban scorpion Rhopalurus junceus was constructed by replacing the UDP-glucosyltransfera...A recombinant Helicoverpa armigera nucleopolyhedrovirus （HearNPV） ex- pressing the insect-selective neurotoxin （RjAalTjO from Cuban scorpion Rhopalurus junceus was constructed by replacing the UDP-glucosyltransferase gene （egt） using ）^- red homologous recombination system. Another egt deleted control HearNPV was con- structed in a similar way by inserting egfp gene into the egt locus. One-step viral growth curve and viral DNA replication curve analysis confirmed that the recombination did not affect the viral growth and DNA replication in host cells. There is no discernable differ- ence in occlusion-body morphogenesis between RjAalTf-HearNPV,, Egfp-HearNPV and HZ8-HearNPV, which was confirmed by transmission electron microscopy analysis. How- ever, the insecticidal activity of RjAal 7f-HearNPV is enhanced against the third instar H. armigera larvae according to the bioassay on virulence comparison. There is a dramatic reduction （56.9%） in median lethal dose （LD50） and also a reduction （13.4%） in median sur- vival time （ST50） for the recombinant RjAalTf-HearNPV compared to the HZ8-HearNPV, but only a 27.5% reduction in LD50 and 10.1% reduction in ST50 value when Egfp- HearNPV is compared with HZ8-HearNPV. The daily diet consumption analysis showed that the RjAal 7f-HearNPV was able to inhibit the infected larvae feeding compared with the egt minus HearNPV. These results demonstrated that this novel recombinant RjAa17f- HearNPV could improve the insecticidal effect against its host insects and RjAa17fcould be a considerable candidate for other recombinant baculovirus constructions.展开更多
Insects possess specific immune responses to protect themselves from different types of pathogens.Activation of immune cascades can inflict significant developmental costs on the surviving host.To characterize infecti...Insects possess specific immune responses to protect themselves from different types of pathogens.Activation of immune cascades can inflict significant developmental costs on the surviving host.To characterize infection kinetics in a surviving host that experiences baculovirus inoculation,it is crucial to determine the timing of immune responses.Here,we investigated time-dependent immune responses and developmental costs elicited by inoculations from each of two wild-type baculoviruses,Autographa californica multiple nucleopolyhedrovirus(AcMNPV)and Helicoverpa zea single nucleopolyhedrovirus(HzSNPV),in their common host H.zea.As H.zea is a semi-permissive host of AcMNPV and fully permissive to HzSNPV,we hypothesized there are differential immune responses and fitness costs associated with resisting infection by each virus species.Newly molted 4th-instar larvae that were inoculated with a low dose(LD15)of either virus showed signify icantly higher hemolymph FAD-glucose dehydrogenase(GLD)activities compared to the corresponding control larvae.Hemolymph phenoloxidase(PO)activity,protein concentration and total hemocyte numbers were not increased,but instead were lower than in control larvae at some time points post-inoculation.Larvae that survived either virus inoculation exhibited reduced pupal weight;survivors inoculated with AcMNPV grew slower than the control larvae,while survivors of HzSNPV pupated earlier than control larvae.Our results highlight the complexity of immune responses and fitness costs associated with combating different baculoviruses.展开更多
基金supported in part by the National Natural Science Foundation of China(32202295)Guizhou Provincial Science and Technology Projects(Qian Ke He Ji Chu-ZK[2022]General 051)+1 种基金Scientific Research Foundation for Talent Introduced in Guizhou University(Gui Da Te Gang He Zi[2021]22)Guizhou Provincial Science and Technology Projects(Qian Ke He Support[2019]2292,Qian Ke He NY[2013]3040).
文摘Neuropeptides are crucial in regulation of a rich variety of developmental,physiological,and behavioral functions throughout the life cycle of insects.Using an integrated approach of multiomics,we identified neuropeptide precursors in the greater wax moth Galleria mellonella,which is a harmful pest of honeybee hives with a worldwide distribution.Here,a total of 63 and 67 neuropeptide precursors were predicted and annotated in the G.mellonella genome and transcriptome,in which 40 neuropeptide precursors were confirmed in the G.mellonella peptidome.Interestingly,we identified 12 neuropeptide precursor genes present in G.mellonella but absent in honeybees,which may be potential novel pesticide target sites.Honeybee hives were contaminated with heavy metals such as lead,enabling its bioaccumulation in G.mellonella bodies through the food chain,we performed transcriptome sequencing to analyze the effects of Pb stress on the mRNA expression level of G.mellonella neuropeptide precursors.After treatment by Pb,the expression of neuropeptide F1 was found to be significantly downregulated,implying that this neuropeptide might be associated with responding to the heavy metal stress in G.mellonella.This study comprehensively identified neuropeptide precursors in G.mellonella,and discussed the effects of heavy metals on insect neuropeptides,with the example of G.mellonella.The results are valuable for future elucidation of how neuropeptides regulate physiological functions in G.mellonella and contribute to our understanding of the insect's environmental plasticity and identify potential new biomarkers to assess heavy metal toxicity in insects.
基金funded by the National Natural Science Foundation of China(32200384)the China Postdoctoral Science Foundation(2022M710053).
文摘Lipid and sugar homeostasis is critical for insect development and survival.In this study,we characterized an acetyl coenzyme A carboxylase gene in Blattella germanica(BgACC)that is involved in both lipogenesis and sugar homeostasis.We found that BgACC was dominantly expressed in the fat body and integument,and was significantly upregulated after molting.Knockdown of BgACC in 5th-instar nymphs did not affect their normal molting to the next nymphal stage,but it caused a lethal phenotype during adult emergence.BgACC-RNA interference(RNAi)significantly downregulated total free fatty acid(FFA)and triacylglycerol(TAG)levels,and also caused a significant decrease of cuticular hydrocarbons(CHCs).Repression of BgACC in adult females affected the development of oocytes and resulted in sterile females,but BgACC-RNAi did not affect the reproductive ability of males.Interestingly,knockdown of BgACC also changed the expression of insulin-like peptide genes(BglLPs),which mimicked a physiological state of high sugar uptake.In addition,BgACC was upregulated when B.germanica were fed on a high sucrose diet,and repression of BgACC upregulated the expression of the glycogen synthase gene(BgGlyS).Moreover,BgACC-RNAi increased the circulating sugar levels and glycogen storage,and a longevity assay suggested that BgACC was important for the survival of B.germanica under conditions of high sucrose uptake.Our results confirm that BgACC is involved in multiple lipid biogenesis and sugar homeostasis processes,which further modulates insect reproduction and sugar tolerance.This study benefits our understanding of the crosstalk between lipid and sugar metabolism.
基金This work was supported by Ministry of Education of the People's Republic of China Chinese Universities Scientific Fund(No.Z1090121096,NWAFU)Ministry of Science and Technology of the People's Republic of China National Key R&D Program of China(2017YFC1200605).
文摘In a tritrophic context of plant-insect-entomopathogen,plants play important roles in modulating the interaction of insects and their pathogenic viruses.Currently,the influence of plants on the transmission of insect viruses has been mainly studied on baculoviruses and some RNA viruses,whereas the impact of plants on other insect viruses is largely unknown.Here,we identified a new densovirus infecting the green peach aphid Myzus persicae and tested whether and how host plants influence the transmission of the aphid densovirus.The complete single-stranded DNA genome of the virus,M.persicae densovirus 2,is 5727 nt and contains inverted terminal repeats.Transcription and phylogenetic analysis indicated that the virus was distinct from other a few identified aphid densoviruses.The virus abundance was detected highly in the intestinal tract of aphids,compared with the lower level of it in other tissues including head,embryo,and epidermis.Cabbage and pepper plants had no obvious effect on the vertical transmission and saliva-mediated horizontal transmission of the virus.However,the honeydew-mediated horizontal transmission among aphids highly depended on host plants(65%on cabbages versus 17%on peppers).Although the virus concentration in the honeydew produced by aphids between 2 plants was similar,the honeydew production of the infected aphids reared on peppers was dramatically reduced.Taken together,our results provide evidence that plants influence the horizontal transmission of a new densovirus in an aphid population by modulating honeydew secretion of aphids,suggesting plants may manipulate the spread of an aphid-pathogenic densovirus in nature.
基金We appreciate the assistance of Y.-M. Zhang and Texas AgriLife Research, Texas A＆M University Sys- tem during this study. The research was financially supported by the National Natural Science Foundation of China （30930062）, the National Basic Research and Development Program of China （2006CB102005-3 and 2009CB 119200） and the Fund for Modem Agro-industry Technology Research System （nycytx-004）.
文摘The parasitoids in the genera of Encarsia and Eretmocerus （Hymenoptera： Aphelinidae） are important biological control agents of whiteflies, and some of them not only parasitize hosts but also kill them with strong host-feeding capacity. Two whitefly parasitoid species, Encarsia sophia and Eretmocerus melanoscutus were examined to determine if mating and host density affected their host feeding and parasitism. The whitefly host, Bemisia tabaci, was presented to these two wasp species in densities of 10, 20, 30, 40, 50 and 60 third-instar nymphs per clip cage. Mated whitefly parasitoid females fed on more hosts than unmated females under a range of host densities （under all six host densities for En. sophia; under the densities of 40 nymphs or more for Er. melanoscutus）. Meanwhile, mated females parasitized more whitefly nymphs than unmated females under all host densities for both species. With increase of host density, mated or unmated Er. melanoscutus females killed more hosts by host feeding and parasitism. Mated En. sophia females killed more hosts by host feeding with increase of host density, whereas unmated females did not parasitze whitefly nymphs at all. Our results suggest that only mated female parasitoids with host-feeding behavior should be released in crop systems to increase their bio-control efficiency.
文摘Fitness and efficacy of Encarsia sophia （Girault ＆ Dodd） （Hymenoptera： Aphelinidae） as a biological control agent was compared on two species of whitefly （Hemiptera： Aleyrodidae） hosts, the relatively smaller sweetpotato whitefly, Bemisia tabaci （Gennadius） biotype ＇B＇, and the larger greenhouse whitefly, Trialeurodes vaporariorum （Westwood）. Significant differences were observed on green bean （Phaseolus vulgaris L.） in the laboratory at 27 ± 2℃, 55% 4- 5% RH, and a photoperiod of 14 ： 10 h （L ： D）. Adult parasitoids emerging from T. vaporariorum were larger than those emerging from B. tabaci, and almost all biological parameters of E. sophia parasitizing the larger host species were superior except for the developmental times of the parasitoids that were similar when para- sitizing the two host species. Furthermore, parasitoids emerging from T. vaporariorum parasitized more of these hosts than did parasitoids emerging from B. tabaci. We conclude that E. sophia reared from larger hosts had better fitness than from smaller hosts. Those from either host also preferred the larger host for oviposition but were just as effective on smaller hosts. Therefore, larger hosts tended to produce better parasitoids than smaller hosts.
基金This study was financially supported by the Yunnan Eco-friendly Food International Cooperation Research Center(YEFICRC)Project of Yunnan Provincial Key Programs(Grant No.2019ZG009)the National Key R&D Program of China(Grant No.2019YFD0300101)+3 种基金the Guangdong Provincial Key Laboratory of Genome Read and Write(Grant No.2017B030301011)the Key Research Program of the Chinese Academy of Sciences(KJZD-SW-L07)the Youth Innovation Promotion Association,CAS(No.2016080)Key-Area Research and Development Program of Guangdong Province(No.2020B020224002)。
文摘The fall armyworm(FAW),Spodoptera frugiperda,is a destructive pest native to America and has recently become an invasive insect pest in China.Because of its rapid spread and great risks in China,understanding of FAW genetic background and pesticide resistance is urgent and essential to develop effective management strategies.Here,we assembled a chromosome-level genome of a male FAW(SFynMstLFR)and compared re-sequencing results of the populations from America,Africa,and China.Strain identification of 163 individuals collected from America,Africa and China showed that both C and R strains were found in the American pop-ulations,while only C strain was found in the Chinese and African populations.Moreover,population geno-mics analysis showed that populations from Africa and China have close relationship with significantly genetic differentiation from American populations.Taken toge-ther,FAWs invaded into China were most likely origi-nated from Africa.Comparative genomics analysis displayed that the cytochrome p450 gene family is extremely expanded to 425 members in FAW,of which 283 genes are specific to FAW.Treatments of Chinese populations with twenty-three pesticides showed the variant patterns of transcriptome profiles,and several detoxification genes such as AOX,UGT and GST spe-cially responded to the pesticides.These findings will be useful in developing effective strategies for manage-ment of FAW in China and other invaded areas.
文摘The green peach aphid, Myzus persicae Sulzer （Hemiptera, Aphididae）, is an important cosmopolitan pest. Real time qRT-PCR has been used for target gene expression analysis on M. persicae. Using real time qRT-PCR, the expression levels are normalized on the basis of the reliable reference genes. However, to date, the stability of available reference genes has been insufficient. In this study, we evaluated nine candidate reference genes from M. persicae under diverse experimental conditions. The tested candidate genes were comprehensively ranked based on five alternative methods （RefFinder, geNorm, Normfinder, BestKeeper and the comparative ACt method）. 18s, Actin and ribosomal protein L27 （L27） were recommended as the most stable reference genes for M. persicae, whereas ribosomal protein L27 （L27） was found to be the least stable reference genes for abiotic studies （photoperiod, temperature and insecticide susceptibility）. Our finding not only sheds light on establishing an accurate and reliable normalization of real time qRT-PCR data in M. persicae but also lays a solid foundation for further studies of M. persicae involving RNA interference and functional gene research.
基金the Qingdao Agricultural University Highlevel Talent Fund(665-1117002663-1119002)+1 种基金Qingdao Agricultural University Graduate Innovation Program(QYC201809)the National Nature Science Foundation of China(31901948).
文摘Insect neuropeptides play an important role in regulating physiological functions such as growth,development,behavior and reproduction.We identified temperaturesensitive neuropeptides and receptor genes of the cotton whitefly,Bemisia tabaci.We identified 38 neuropeptide precursor genes and 35 neuropeptide receptors and constructed a phylogenetic tree using additional data from other insects.As temperature adaptability enables B.tabaci to colonize a diversity of habitats,we performed quantitative polymerase chain reaction with two temperature stresses(low=4℃ and high=40℃)to screen for temperature-sensitive neuropeptides.We found many neuropeptides and receptors that may be involved in the temperature adaptability of B.tabaci.This study is the first to identify B.tabaci neuropeptides and their receptors,and it will help to reveal the roles of neuropeptides in temperature adaptation of B.tabaci.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.31772533 and 31670659)the State Key Laboratory of Integrated Management of Pest Insects and Rodents(Grant No.Chinese IPM1717).
文摘Cuticular hydrocarbons form a barrier that protects terrestrial insects from water loss via the epicuticle.Lipophorin loads and transports lipids,including hydrocarbons,from one tissue to another.In some insects,the lipophorin receptor(LpR),which binds to lipophorin and accepts its lipid cargo,is essential for female fecundity because it mediates the incorporation of lipophorin by developing oocytes.However,it is unclear whether LpR is involved in the accumulation of cuticular hydrocarbons and its precise role in aphid reproduction remains unknown.We herein present the results of our molecular characterization,phylogenetic analysis,and functional annotation of the pea aphid(Acyrthosiphon pisum)LpR gene(ApLpR).This gene was transcribed throughout the A.pisum life cycle,but especially during the embryonic stage and in the abdominal cuticle.Furthermore,we optimized the RHA interference(RNAi)parameters by determining the ideal dose and duration for gene silencing in the pea aphid.We observed that the RNAi-based ApLpR suppression significantly decreased the internal and cuticular hydrocarbon contents as well as adult fecundity.Additionally,a deficiency in cuticular hydrocarbons increased the susceptibility of aphids to desiccation stress,with decreased survival rates under simulated drought conditions.Moreover,ApLpR expression levels significantly increased in response to the desiccation treatment.These results confirm that ApLpR is involved in transporting hydrocarbons and protecting aphids from desiccation stress.Furthermore,this gene is vital for aphid reproduction.Therefore,the ApLpR gene of A.pisum may be a novel RNAi target relevant for insect pest management.
文摘Development, survivorship, pupal weight, oviposition, and life table parameters of the oriental tobacco budworm, Helicoverpa assulta Guenée, were evaluated in the laboratory on an artificial diet, pepper （Capsicumfrutescens L.）, and tobacco （Nicotiana tobacum L.）. We found that the average developmental time of immature stages was longest on tobacco （36.2 d）, intermediate on pepper （34.4 d）, and shortest on artificial diet （33.5 d）. Immature survival from egg to pupa varied from 31% on tobacco, 43% on pepper, and 74% on artificial diet. Pupal weight ranged from 197.4 mg/pupa on tobacco, 233.1 mg/pupa on pepper and 253.4 mg/pupa on artificial diet. The average numbers of eggs laid by adults reared as larvae on the artificial diet, pepper, or tobacco were 614, 421 and 334 eggs/female, respectively. Numbers of remaining eggs in ovaries of the adult females reared as larvae on the artificial diet, pepper, or tobacco were 16, 26, and 42 eggs/female, respectively. The longevity of adult females developed from larvae reared on the three diets was not significantly different, whereas the longevity of male adults from the larvae reared on artificial diet was longer （16.8 d） than that for males reared on tobacco （13.8 d） and pepper （13.3 d）. The intrinsic, finite, gross, and net rates of increase were highest for females reared as larvae on artificial diet, lowest for females emerging from larvae reared on tobacco, and intermediate for females emerging from larvae reared on pepper. Generation times and doubling time of H. assulta were shortest for larvae fed artificial diet, intermediate from larvae reared on pepper, and longest from larvae reared on tobacco. We concluded that the artificial diet was the most suitable larval diet ofH. assulta followed by pepper, and tobacco.
基金This research was funded by Tianjin City Science ＆ Technology Training Project （No. 043121811）, South Tianjin National Science ＆ Technology Demonstration District Special Project （No. 043124311）, and the General Project of Tianjin Municipal Natural Science Foundation （No. 05YFJMJC07100）. We would like to thank G. A. Evans CUSDA-APHIS, BeltsviUe, MD, USA） and J. Huang （Fujian Agricultural ＆ Forestry University, Fuzhou, China） for identification of the parasitoid. We would also like to thank W. J. Sun, Director of South Tianjin National Sci- ence ＆ Technology Demonstration District, for his support.
文摘We conducted three experiments for management of Bemisia tabaci （Gennadius） biotype＇ B＇ on tomatoes under greenhouse conditions： （i） vertically placing yellow sticky cards either parallel or perpendicular to tomato rows at a rate of 1 per 3-m row; （ii） releasing Eretmocerus sp. nr. rajasthanicus once at 30 adults/m2 in the high whitefly density greenhouses （〉 10 adults/plant）, or twice at 15 adults/m2 at a 5-day interval in the low whitefly density greenhouses （〈 10 adults/plant）; and （iii） using combinations of yellow sticky cards that were placed vertically parallel to tomato rows and parasitoids released once at 30/m2 in high whitefly density greenhouses or twice at 15/m2 at a 5-day interval in low whitefly density greenhouses. Our data show that yellow sticky cards trapped B. tabaci adults and significantly reduced whitefly populations on tomato. The yellow sticky cards that were placed parallel to tomato rows caught significantly more whitefly adults than those placed perpendicular to tomato rows on every sampling date. In the treatment where parasitoids were released once at 30/m2 in high whitefly density greenhouses, the number of live whitefly nymphs were reduced from 4.6/leaf to 2.9/leaf in 40 days as compared with those on untreated plants on which live whitefly nymphs increased from 4.4/leaf to 8.9/leaf. In the treatment where parasitoids were released twice at 15/m2 in low whitefly density greenhouses, the numbers of live nymphs ofB. tabaci on tomato leaves were reduced from 2.1/leaf to 1.7/leaf in 20 days as compared with those on untreated plants on which numbers of live nymphs ofB. tabaci increased from 2.2/leaf to 4.5/leaf. In the treatment of yellow sticky cards and parasitoid release once at 30/m2 in high whitefly density greenhouses, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 7.2/leaf to 1.9/leaf, and in the treatment of yellow sticky cards and parasitoid release twice at 15/m2 at a 5-day interval at low whitefly density, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 2.5/leaf to 0.8/leaf; whereas the numbers of live nymphs of B. tabaci on untreated plants increased from 4.4/leaf to 8.9/leaf. An integrated program for management of B. tabaci on greenhouse vegetables by using yellow sticky cards, parasitoids and biorational insecticides is discussed.
文摘Southwestern corn borer （SWCB, Diatraea grandiosella） and fall armyworm （FAW, Spodopterafrugiperda） are major pests of sorghum in the southern United States. Host plant resistance is a desirable means for reducing plant damage and yield losses from both insects. In this study, we evaluated 12 sorghum lines for whorl-stage resistance to leaf-feeding SWCB and FAW in greenhouse and laboratory bioassays. Differential plant responses were detected against the two insects. Among 12 lines tested, CM1821, Della and PI196583 were resistant to both insects, while BTx2752 was largely susceptible. Line R.09110 was resistant to SWCB, but susceptible to FAW, whereas Redbine-60 was suscep- tible to SWCB, but not to FAW. In addition, we quantified various chemical components in the plants and determined their association with insect resistance. Tannin and chloro- phyll in leaves did not show any significant correlation with resistance to either insects, but contents of soluble protein in general were negatively correlated with resistance to both insects. Endogenous soluble sugar and dhurrin were only positively correlated with resistance to SWCB, but not with FAW resistance. To gain some molecular insight into resistance mechanism of sorghum to SWCB, we performed qPCR reactions for key genes encoding enzymes involved in dhurrin and jasmonic acid （JA） biosynthesis on selected resistant or susceptible lines. Although these genes were rapidly and strongly induced by insect feeding in all lines, the observed resistance is likely explained by higher constitutive dhurrin contents in some resistant lines and higher basal JA biosynthesis in others. Our results suggest that sorghum utilizes multiple strategies to defend itself against SWCB.
文摘The functional response of Cydonia vicina nilotica Muls. （Coleoptera： Coccinellidae） to six densities of Aphis craccivora Koch （Homoptera： Aphididae） nymphs on broad bean （Viciafaba Linn.） was investigated in the laboratory. A linear relationship between the rate of consumption and prey density was observed with r^2 values between 0.58 and 0.97. Plotting prey density against prey killed by four larval instars, and adult males and females of C. vicina nilotica fit well with the type Ⅱ model of Holling＇ s disc equation. Adult females consumed the highest number of prey, followed by fourth instars and adult males. Based on the functional response data, the model predicts a maximum of 144.9, 116.3, 86.2, 80.0, 72.5 and 20.0 nymphs to be consumed per day by an individual adult female, fourth instar, adult male, third, second and first instars, respectively. The differences in the responses of the predator to aphid densities are discussed.
基金the National Basic Research Program of Ministry of Science and Technology,China(973 Program,2012CB114105)National Natural Science Foundation of China (31272089)China Agriculture Research System (CARS一25一B一06).
文摘Natal rearing experience of animals may affect their behaviors,such as habitat selection and oviposition decision.As part of the overall fitness of insect parasitoids, successful host discrimination (distinguishing parasitized hosts from unparasitized hosts) is of paramount importance.In this study we examined whether and how parasitoids' natal rearing experience would affect their host discrimination ability according to host availability.We established separate colonies ofAphidius gifuensis Ashmead by continual rearing on two hosts,Sitobion avenae E and Myzuspersicae (Suzler),and quantified self superparasitism and self superparasitism versus parasitism ratio for the four:combinations ofparasitoid colonies and host species (S.aveane and M.persicae)at four host densities (30,50,100 or 150 per plant).Results showed that self superparasitism ofM.persicae by A.gifuensis reared on S.avenae was significantly higher than by those reared on M.persicae,no matter whether the host densities were 30,50,100 or 150.Aphidius gifuensis reared on M.persicae significantly superparasitized more S.avenae than those reared on S.aveane only when host density was 30.Self superparasitism versus parasitism ratio of A.gifuensis from both colonies was always lower on natal hosts than on new hosts,and the difference was more pronounced as the host density decreased.These results suggested that natal rearing effects is important on host discrimination and oviposition decision of the parasitoid A.gifuensis.These effects promoted the parasitoid's host adaptation and made them confer greater fitness.
文摘The impacts of potato psyllid （Bactericera cockerelli） feeding on potato foliage on the free amino acids （FAAs） composition in potato leaf and tubers were determined under greenhouse conditions. The free amino acids in plant extracts were separated by high-performance liquid chromatography, and in both leaf and tuber samples, at least 17 FAAs were detected. Psyllid feeding significantly changed the levels of several FAAs in both leaf and tuber samples. The concentration of leucine increased 1.5-fold, whereas that of serine and proline increased 2- and 3-fold, respectively. In contrast, the concentrations ofglutamic acid, aspartic acid and lyscine were significantly reduced by 42.0%, 52.1% and 27.5%, respectively. There were also significant changes in the levels of FAAs in the Zebra chip （ZC） infected tubers compared with the healthy tubers, and the levels of six of the FAAs increased, and the levels of nine of the FAAs decreased. The results from this study indicate that potato psyllid causes major changes in free amino acid composition of plant tissues, and this change in plant metabolism may contribute to the plant stress as indicated by increased levels of proline in the leaves and hence promoting the development of plant diseases such as ZC disease.
基金This work was supported by the National Natural Science Foundation of China(Grant No.31772533).
文摘Water retention is critical for physiological homeostasis and survival in terrestrial insects. While deposition of hydrocarbons on insect cuticles as a key measure for water conservation has been extensively investigated, we know little about other mechanisms for preventing water loss in insects. Here, we report two fatty acid synthetic genes that are independent of hydrocarbon production but crucial for water retention in the German cockroach Blattella germanica (L.). First, an integument enriched fatty acid elongase gene (BgElo1) was identified as a critical gene for desiccation resistance in B. germanica;however, knockdown of BgElo1 surprisingly failed to cause a decline in cuticular lipids. In addition, RNA interference (RNAi)-knockdown of an upstream fatty acid synthase gene (BgFas3) showed a similar phenotype, and transmission electron microscopy analysis revealed that BgFas3- or BgElo1-RNAi did not affect cuticle architecture. Bodyweight loss test showed that repression of BgFas3 and BgElo1 significantly increased the weight loss rate, but the difference disappeared when the respiration was closed by freeze killing the cockroaches. A water immersion test was performed, and we found that BgFas3- and BgElo1-RNAi made it difficult for cockroaches to recover from drowning, which was supported by the upregulation of hypoxia-related genes after a 10-h recovery from drowning. Moreover, a dyeing assay with water-soluble Eosin Y showed that this was caused by the entry of water into the respiratory system. Our research suggests that BgFas3 and BgElo1 are required for both inward and outward waterproofing of the respiratory system. This study benefits the understanding of water retention mechanisms in insects.
文摘Microbial abundance and diversity of different life stages （fourth instar larvae, pupae and adults） of the diamondback moth, Plutella xylostella L., collected from field and reared in laboratory, were investigated using bacteria culture-dependent method and PCR-DGGE analysis based on the sequence of bacteria 16S rRNA V3 region gene. A large quantity of bacteria was found in all life stages ofP. xylostella. Field population had higher quantity of bacteria than laboratory population, and larval gut had higher quantity than pupae and adults. Culturable bacteria differed in different life stages ofP. xylostella. Twenty-five different bacterial strains were identified in total, among them 20 strains were presented in larval gut, only 8 strains in pupae and 14 strains in adults were detected. Firmicutes bacteria, Bacillus sp., were the most dominant species in every life stage. 15 distinct bands were obtained from DGGE electrophoresis gel. The sequences blasted in GenBank database showed these bacteria belonged to six different genera. Phylogenetic analysis showed the sequences of the bacteria belonged to the Actinobacteri, Proteobacteria and Firmicutes. Serratia sp. in Proteobacteria was the most abundant species in larval gut. In pupae, unculturable bacteria were the most dominant species, and unculturable bacteria and Serratia sp. were the most dominant species in adults. Our study suggested that a combination of molecular and traditional culturing methods can be effectively used to analyze and to determine the diversity of gut microflora. These known bacteria may play important roles in development of P. xylostella.
文摘Most female herbivores ensure to lay eggs where their offspring can develop successfully. The oviposition preferences of females affect strategies in pest management. In this study, the performance of two cohorts of Trichoplusia ni larvae on cabbage and cotton （after they had been transferred from their original host plants） were investigated. The preferences of female moth ovipositing and larval feeding on these two host plants were observed. The results indicated that plants significantly affected oviposition preference of the female adults and development and survival of larvae of T. ni. All females preferred to lay eggs on cabbage than cotton regardless from which host they originated. The detrimental effects of cotton on the development and survival of T. ni larvae originated from cabbage （CaTn） increased with the increase of the larval age when they were transferred. In addition, the host plant change did not significantly affect the development and survival of larvae of T. ni originating from cotton （CoTn）. Larvae of CaTn preferred cabbage plants as compared to cotton plants, whereas larvae of CoTn did not show a significant choice. Although the adult females preferred laying eggs on cabbage, they did not show preferences between cotton and cabbage in a Y-tube olfactometer test. The hypothesis of oviposition preference and performance of larvae was supported by the results of CaTn, whereas they not supported by those from CoTn. Based on these results, the strategy to manage this serious pest was discussed.
文摘A recombinant Helicoverpa armigera nucleopolyhedrovirus （HearNPV） ex- pressing the insect-selective neurotoxin （RjAalTjO from Cuban scorpion Rhopalurus junceus was constructed by replacing the UDP-glucosyltransferase gene （egt） using ）^- red homologous recombination system. Another egt deleted control HearNPV was con- structed in a similar way by inserting egfp gene into the egt locus. One-step viral growth curve and viral DNA replication curve analysis confirmed that the recombination did not affect the viral growth and DNA replication in host cells. There is no discernable differ- ence in occlusion-body morphogenesis between RjAalTf-HearNPV,, Egfp-HearNPV and HZ8-HearNPV, which was confirmed by transmission electron microscopy analysis. How- ever, the insecticidal activity of RjAal 7f-HearNPV is enhanced against the third instar H. armigera larvae according to the bioassay on virulence comparison. There is a dramatic reduction （56.9%） in median lethal dose （LD50） and also a reduction （13.4%） in median sur- vival time （ST50） for the recombinant RjAalTf-HearNPV compared to the HZ8-HearNPV, but only a 27.5% reduction in LD50 and 10.1% reduction in ST50 value when Egfp- HearNPV is compared with HZ8-HearNPV. The daily diet consumption analysis showed that the RjAal 7f-HearNPV was able to inhibit the infected larvae feeding compared with the egt minus HearNPV. These results demonstrated that this novel recombinant RjAa17f- HearNPV could improve the insecticidal effect against its host insects and RjAa17fcould be a considerable candidate for other recombinant baculovirus constructions.
基金the United States Department of Agriculture(AFRI 2017-67013-26596)awarded to GWF and KHNational Science Foundation(IOS-1645548)awarded to GWF,IS,and KH+1 种基金and Hatch Project PEN04576(GWF and KH).QP thanks the financial support from China Scholarship Council(grant 201506300111)Natural Sciences and Engineering Research Council of Canada Postdoctoral Fellowship(NSERC PDF-488105-2016).
文摘Insects possess specific immune responses to protect themselves from different types of pathogens.Activation of immune cascades can inflict significant developmental costs on the surviving host.To characterize infection kinetics in a surviving host that experiences baculovirus inoculation,it is crucial to determine the timing of immune responses.Here,we investigated time-dependent immune responses and developmental costs elicited by inoculations from each of two wild-type baculoviruses,Autographa californica multiple nucleopolyhedrovirus(AcMNPV)and Helicoverpa zea single nucleopolyhedrovirus(HzSNPV),in their common host H.zea.As H.zea is a semi-permissive host of AcMNPV and fully permissive to HzSNPV,we hypothesized there are differential immune responses and fitness costs associated with resisting infection by each virus species.Newly molted 4th-instar larvae that were inoculated with a low dose(LD15)of either virus showed signify icantly higher hemolymph FAD-glucose dehydrogenase(GLD)activities compared to the corresponding control larvae.Hemolymph phenoloxidase(PO)activity,protein concentration and total hemocyte numbers were not increased,but instead were lower than in control larvae at some time points post-inoculation.Larvae that survived either virus inoculation exhibited reduced pupal weight;survivors inoculated with AcMNPV grew slower than the control larvae,while survivors of HzSNPV pupated earlier than control larvae.Our results highlight the complexity of immune responses and fitness costs associated with combating different baculoviruses.
