Matrix metalloproteinases (MMPs) are crucial for tissue remodeling and immune responses in insects, yet it remains unclear how MMPs affect the various immune processes against pathogenic infections and whether the res...Matrix metalloproteinases (MMPs) are crucial for tissue remodeling and immune responses in insects, yet it remains unclear how MMPs affect the various immune processes against pathogenic infections and whether the responses vary among insects. In this study, we used the lepidopteran pest Ostrinia furnacalis larvae to address these questions by examining the changes of immune-related gene expression and antimicrobial activity after the knockdown of MMP14 and bacterial infections. We identified MMP14 in O. furnacalis using the rapid amplification of complementary DNA ends (RACE), and found that it was conserved and belonged to the MMP1 subfamily. Our functional investigations revealed that MMP14 is an infection-responsive gene, and its knockdown reduces phenoloxidase (PO) activity and Cecropin expression, while the expressions of Lysozyme, Attacin, Gloverin, and Moricin are enhanced after MMP14 knockdown. Further PO and lysozyme activity determinations showed consistent results with gene expression of these immune-related genes. Finally, the knockdown of MMP14 decreased larvae survival to bacterial infections. Taken together, our data indicate that MMP14 selectively regulates the immune responses, and is required to defend against bacterial infections in O. furnacalis larvae. Conserved MMPs may serve as a potential target for pest control using a combination of double-stranded RNA and bacterial infection.展开更多
Bacillus thuringiensis is a Gram-positive aerobic bacterium that produces insecticidal crystalline inclusions during sporulation phases of the mother cell. The vir- ulence factor, known as parasporal crystals, is comp...Bacillus thuringiensis is a Gram-positive aerobic bacterium that produces insecticidal crystalline inclusions during sporulation phases of the mother cell. The vir- ulence factor, known as parasporal crystals, is composed of Cry and Cyt toxins. Most Cry toxins display a common 3-domain topology. Cry toxins exert intoxication through toxin activation, receptor binding and pore formation in a suitable larval gut environment. The mosquitocidal toxins of Bt subsp, israelensis (Bti) were found to be highly active against mosquito larvae and are widely used for vector control. Bt subsp, jegathesan is another strain which possesses high potency against broad range of mosquito larvae. The present review summarizes characterized receptors for Cry toxins in mosquito larvae, and will also discuss the diversity and effects of 3-D mosquitocidal Cry toxin and the ongo- ing research for Cry toxin mechanisms generated from investigations of lepidopteran and dipteran larvae.展开更多
Spatial and temporal patterns of insect damage in relation to aflatoxin contamination in a corn field with plants of uniform genetic background are not well understood. After previous examination of spatial patterns o...Spatial and temporal patterns of insect damage in relation to aflatoxin contamination in a corn field with plants of uniform genetic background are not well understood. After previous examination of spatial patterns of insect damage and aflatoxin in pre-harvest corn fields, we further examined both spatial and temporal patterns of cob- and kernel- feeding insect damage, and aflatoxin level with two samplings at pre-harvest in 2008 and 2009. The feeding damage by each of the ear/kernel-feeding insects (i.e., corn earworm/fall armyworm damage on the silk/cob, and discoloration of corn kernels by stink bugs) and maize weevil population were assessed at each grid point with five ears. Sampling data showed a field edge effect in both insect damage and aflatoxin contamination in both years. Maize weevils tended toward an aggregated distribution more frequently than either corn earworm or stink bug damage in both years. The frequency of detecting aggregated distribution for aflatoxin level was less than any of the insect damage assessments. Stink bug damage and maize weevil number were more closely associated with aflatoxin level than was corn earworm damage. In addition, the indices of spatial-temporal association (χ) demonstrated that the number of maize weevils was associated between the first (4 weeks pre-harvest) and second (1 week pre-harvest) samplings in both years on all fields. In contrast, corn earworm damage between the first and second samplings from the field on the Belflower Farm, and aflatoxin level and corn earworm damage from the field on the Lang Farm were dissociated in 2009.展开更多
ldentifying novel biocontrol agents and developing new strategies are urgent goals in insect pest biocontrol.Ascoviruses are potential competent insect viruses that may be developed into bioinsecticides,but this aim i...ldentifying novel biocontrol agents and developing new strategies are urgent goals in insect pest biocontrol.Ascoviruses are potential competent insect viruses that may be developed into bioinsecticides,but this aim is impeded by their poor oral infectivity.To improve the per os infectivity of ascovirus,Bacillus thuringiensis kurstaki(Btk)was employed as a helper to damage the midgut of lepidopteran larvae(Helicoverpa armigera,Mythimna separata,Spodoptera frugiperda,and S.litura)in formulations with Heliothis virescens ascovirus isolates(HvAV-3h and HvAV-3j).Btk and ascovirus mixtures(Btk/HvAV-3h and B1k/HvAV-3j)were fed to insect larvae(3rd instar).With the exception of S.frugiperda larvae,which exhibited low mortality after ingesting Btk,the larvae of the other tested species showed three types of response to feeding on the formulas:type I,the tested larvae(H.armigera)were killed by Btk infection so quickly that insufficient time and resources remained for ascoviral invasion;type II,both Btk and the ascovirus were depleted by their competition,such that neither was successfully released or colonized the tissue;type II,Btk was eliminated by the ascovirus,and the ascovirus achieved systemic infection in the tested larvae.The feeding of Btk/ascovirus formulas led to a great reduction in larval diet consumption and resulted in a significant decrease in the emergence rate of H.armigera,M.separata,and S.litura larvae,which suggested that the formulas exerted marked oral control effects on both the contemporary individuals and the next generation of these tested pest species.展开更多
Bacterial endosymbionts of sap-sucking insects provide their host with a num- ber of beneficial qualities,including the supply of nutrition,defense against parasitoids, and protection from heat stress.Damage to these ...Bacterial endosymbionts of sap-sucking insects provide their host with a num- ber of beneficial qualities,including the supply of nutrition,defense against parasitoids, and protection from heat stress.Damage to these bacterial associates can therefore have a negative impact on the fitness of their insect host.We evaluated observational and experi- mental factors regarding the normative hemlock woolly adelgid (Adelges tsugae Annand) (Hemiptera:Adelgidae)to help understand the roles of its three recently identified symbionts,including under heat stress conditions.The prevalence of A.tsugae's facultafive symbiont (Serratia symbiotica)was examined at different spatial scales to determine how variable infection rates are for this symbiont.There was no significant difference found in infection rates between adelgids on a tree,within a plot,or within a state.However, significantly more adelgids in Georgia (95%)had S.symbiotica compared to those in New York (68%).Microsatellite genotyping of the adelgids found that this difference was most likely not the result of a second introduction ofA.tsugae into eastern North America.Comparison orS.symbiotica proportions between first and fourth instars showed that symbiont absence did not affect the ability ofA.tsugae to survive aestivation.Evaluations of sym- biont densities within each adelgid found that when S.symbiotica was absent,the density of obligate symbionts was significantly higher.Exposure to heat stress (32.5℃)was not consistently correlated with changes in symbiont densities over a 4-d period.Overall,we have shown that symbiont prevalence and densities vary within the broad population of A.tsugae in eastern North America,with potentially significant effects upon the ecology of this important pest.展开更多
Phytopathogen infections are frequently influenced by both biotic and abiotic factors in a crop field. The effect of brown stink bug, Euschistus servus (Hemiptera: Pentatomidae), feeding and planting date and sampl...Phytopathogen infections are frequently influenced by both biotic and abiotic factors in a crop field. The effect of brown stink bug, Euschistus servus (Hemiptera: Pentatomidae), feeding and planting date and sampling time on common smut (Ustilago maydis) infection percentage of maize plants was examined in 2005 and 2006, and 2010 and 2011, respectively. Brown stink bug adult feeding on maize hybrid "DKC6971" at flowering in 2005 and 2006 did not influence smut infection percentage when examined using 3 treatments (i.e., 0 adult, 5 adults, and 5 adults mixed with the smut spores). The smut infection percentages were 〈 3% (n =12) in the 3 treatments. The smut infection percentage among the 4 weekly samplings was the same, so was natural aflatoxin contamination at harvest among the treatments. The 2nd experiment showed that planting date did not affect the smut infection percentage in either 2010 or 2011. But, the smut infection percentage from the postflowering sampling was greater than preflowering sampling in both years. The smut infection percentage varied among the germplasm lines in 2010, but not in 2011. This study demonstrated that brown stink bug feeding at flowering had no effect on smut infection in maize, and the best time for smut evaluation would be after flowering. The temperature and precipitation might have also influenced the percentage of smut-infected maize plants during the 4 years when the experiments were conducted. The similarity between kernel-colonizing U. maydis and Aspergillus flavus infections and genotype × environment interaction were also discussed.展开更多
The brown stink bug (BSB), Euschistus servus (Say)(Hemiptera: Pentatomidae), is a serious economic pest of corn production in the southeastern United States. The BSB population dynamics was mon itored for 17 weeks fro...The brown stink bug (BSB), Euschistus servus (Say)(Hemiptera: Pentatomidae), is a serious economic pest of corn production in the southeastern United States. The BSB population dynamics was mon itored for 17 weeks from tasseling to preharvest of corn plants (i.e., late May to mid-September) using pheromone traps in three corn fields from 2005 to 2009. The trap data showed two peaks in early June and mid-August, respectively. The relationship between trap catch and pregrowing season weather data was examined using correlation and stepwise multiple factor regression analyses. Weather indices used for the analyses were accumulated growing degree day (AGDD), number of days with minimum temperature below 0℃(Subz), accumulated daily maximum (AMaxT) and minimum temperatures (AMinT) and rainfall (ARain). The weather indices were calculated with lower (10℃) and upper (35℃) as biological thresholds. The parameters used in regression analysis were seasonal abundance (or overall mean of BSB adult catch)(BSBm), number of BSB adults caught at a peak (PeakBSB), and peak week (Peakwk). The BSBm was negatively related to high temperature (AmaxT or AGDD) consistently, whereas IstPeakBSB was positively correlated to both ARain and Subz, irrespective of weather data durations (the first 4, 4.5, and 5 months). In contrast, the 7-month weather data (AGDD7) were negatively correlated to the BSBm only, but not correlated to the second PeakBSB. The 5-year monitoring study demonstrated that weather data can be used to predict the BSB abundance at its first peak in tasseling corn fields in the southeastern U.S. states.展开更多
In sub-Saharan Africa cassava growing areas,two members of the Bemisia tabaci species complex termed sub-Saharan Africa 1(SSA1)and SSA2 have been reported as the prevalent whiteflies associated with the spread of viru...In sub-Saharan Africa cassava growing areas,two members of the Bemisia tabaci species complex termed sub-Saharan Africa 1(SSA1)and SSA2 have been reported as the prevalent whiteflies associated with the spread of viruses that cause cassava mosaic disease(CMD)and cassava brown streak disease(CBSD)pandemics.At the peak of CMD pandemic in the late 1990s,SSA2 was the prevalent whitefly,although its numbers have diminished over the last two decades with the resurgence of SSA1 whiteflies.Three SSA1 subgroups(SGI to SG3)are the predominant whiteflies in East Africa and vary in distribution and biological properties.Mating compatibility between SSA1 subgroups and SSA2 whiteflies was reported as the possible driver for the resurgence of SSA 1 whiteflies.In this study,a combination of both phylogenomic methods and reciprocal crossing experiments were applied to determine species status of SSA1 subgroups and SSA2 white-fly populations.Phylogenomic analyses conducted with 26548205 bp whole genome single nucleotide polymorphisms(SNPs)and the full mitogenomes clustered SSA1 subgroups together and separate from SSA2 species.Mating incompatibility between SSA1 subgroups and SSA2 further demonstrated their distinctiveness from each other.Phylogenomic analyses conducted with SNPs and mitogenomes also revealed different genetic relationships among SSA1 subgroups.The former clustered SSA 1-SGI and SSA1-SG2 to-gether but separate from SSA1-SG3,while the latter clustered SSA1-SG2 and SSA1-SG3 together but separate from SSA 1-SG1.Mating compatibility was observed between SSA 1-SGI and SSA1-SG2,while incompatibility occurred between SSA 1-SGI and SSA1-SG3,and SSA 1-SG2 and SSA 1-SG3.Mating results among SSA 1 subgroups were coherent with phylogenomics results based on SNPs but not the full mitogenomes.Furthermore,this study revealed that the secondary endosymbiont--did not mediate reproductive success in the crossing assays carried out.Overall,using genome wide SNPs together with reciprocal crossings assays,this study established accurate genetic relationships among cassava-colonizing populations,illustrating that SSA1 and SSA2 are distinct species while at least two species occur within SSA1 species.展开更多
Pesticide resistance and resurgence are serious problems often occurring simultaneously in the field.In our long-term study of a fenpropathrin-resistant strain of Tetranychus cinnabaribus,enhancement of detoxification...Pesticide resistance and resurgence are serious problems often occurring simultaneously in the field.In our long-term study of a fenpropathrin-resistant strain of Tetranychus cinnabaribus,enhancement of detoxification and modified fecundity mechanisms were both observed.Here we investigate the network across these two mechanisms and find a key node between resistance and resurgence.We show that the ecdysone pathway is involved in regulating the fecundity of T.cinnabaribus.The concentration change of ecdysone is consistent with the fecundity curve;the concentration of ecdysone is higher in the fenpropathrin-resistant strain which has stronger fecundity.The enhancement of ecdysone is due to overexpression of two P450 genes(CYP314A1 and CYP315A1)in the ecdysone synthesis pathway.Silencing expression of these CYP genes resulted in lower concentration of ecdysone,reduced expression of vitellogenin,and reduced fecundity of T.cinnabaribus.The expression of CYP315A1 is regulated by transcription factors Cap-n-collar isoform C(CncC)and Musculoaponeurotic fibrosarcoma protein(Maf),which are involved in regulating other P450 genes functioning in detoxification of fenpropathrin in T.cinnabaribus.A similar regulation is established in citrus pest mite Panonychus citri showing that the CncC pathway regulates expression of PcCYP315Al,which affects mite fecundity.Transcription factors are activated to upregulate detoxification genes facilitating pesticide resistance,while the“one to multiple”regulation mode of transcription factors simultaneously increases expression of metabolic enzyme genes in hormone pathways and alters the physiology of pests.This is an important response of arthropods to pesticides which leads to resistance and population resurgence.展开更多
Insect pest damage to crops is a threat to global food security(Tilman et al.,2011).Climate change,the evolution of insecticide resistance,and the phasing out of insecticides due to environmental and safety concerns e...Insect pest damage to crops is a threat to global food security(Tilman et al.,2011).Climate change,the evolution of insecticide resistance,and the phasing out of insecticides due to environmental and safety concerns exacerbate this problem.Farmers urgently need safe and effective crop protection tools to sustainably generate yields that meet ever-increasing global demand.展开更多
Anautogenous mosquitoes must blood feed on a vertebrate host to produce eggs.Each gonadotrophic cycle is subdivided into a sugar-feeding previtellogenic phase that produces primary follicles and a blood meal-activated...Anautogenous mosquitoes must blood feed on a vertebrate host to produce eggs.Each gonadotrophic cycle is subdivided into a sugar-feeding previtellogenic phase that produces primary follicles and a blood meal-activated vitellogenic phase in which large numbers of eggs synchronously mature and are laid.Multiple endocrine factors including juvenile hormone(JH),insulin-like peptides(ILPs),ovary ecdysteroidogenic hormone(OEH),and 20-hydroxyecdysone(20E)coordinate each gonadotrophic cycle.Egg formation also requires nutrients from feeding that are stored in the fat body.Regulation of egg formation is best understood in Aedes aegypti but the role different endocrine factors play in regulating nutrient mobilization and storage remains unclear.In this study,we report that adult female Ae.aegypti maintained triacylglycerol(TAG)stores during the previtellogenic phase of the first gonadotrophic cycle while glycogen stores declined.In contrast,TAG and glycogen stores were rapidly mobilized during the vitellogenic phase and then replenishment.Several genes encoding enzymes with functions in TAG and glycogen metabolism were differentially expressed in the fat body,which suggested regulation was mediated in part at the transcriptional level.Gain of function assays indicated that stored nutrients were primarily mobilized by adipokinetic hormone(AKH)while juvenoids and OEH regulated replenishment.ILP3 further showed evidence of negatively regulating certain lipolytic enzymes.Loss of function assays indicated AKH depends on the AKH receptor(AKHR)for function.Altogether,our results indicate that the opposing activities of different hormones regulate nutrient stores during a gonadotrophic cycle in Ae.aegypti.展开更多
DNA methylation is accomplished in animals by 2 classes of enzymes known as DNA methyltransferases, DNMT3 and DNMT 1, which perform de novo methylation and maintenance methylation, respectively. Several studies of hym...DNA methylation is accomplished in animals by 2 classes of enzymes known as DNA methyltransferases, DNMT3 and DNMT 1, which perform de novo methylation and maintenance methylation, respectively. Several studies of hymenopteran eusocial insects suggest that DNA methylation is capable of influencing developmental plasticity. However, fundamental questions remain about the patterning of DNA methylation during the course of insect development. In this study, we performed quantitative real-time PCR (qPCR) on transcripts from the single-copy orthologs of DNMT1 and DNMT3 in the red imported fire ant, Solenopsis invicta. In particular, we assessed the expression of S. invicta Dnmtl and Dnmt3 mRNA during 7 stages of worker development, among behaviorally distinct adults, and among male and female gonads. Dnmt3 was most highly expressed during embryonic development, whereas Dnmtl was similarly expressed throughout the course of develop- ment. Moreover, Dnmtl and Dnmt3 were highly expressed in testes and ovaries. Neither Dnmt was significantly differentially expressed among heads of behaviorally distinct adult castes. Our results support the hypothesis that extensive patterning of DNA methylation occurs during gametogenesis and embryogenesis in the insect order Hymenoptera.展开更多
基金supported by the National Natural Sci-ence Foundation of China(32072417 and 31901876)the Natural Science Foundation of Jiangsu Province(BK20190900)the China Postdoctoral Science Foundation Funded Project(2018M642343).
文摘Matrix metalloproteinases (MMPs) are crucial for tissue remodeling and immune responses in insects, yet it remains unclear how MMPs affect the various immune processes against pathogenic infections and whether the responses vary among insects. In this study, we used the lepidopteran pest Ostrinia furnacalis larvae to address these questions by examining the changes of immune-related gene expression and antimicrobial activity after the knockdown of MMP14 and bacterial infections. We identified MMP14 in O. furnacalis using the rapid amplification of complementary DNA ends (RACE), and found that it was conserved and belonged to the MMP1 subfamily. Our functional investigations revealed that MMP14 is an infection-responsive gene, and its knockdown reduces phenoloxidase (PO) activity and Cecropin expression, while the expressions of Lysozyme, Attacin, Gloverin, and Moricin are enhanced after MMP14 knockdown. Further PO and lysozyme activity determinations showed consistent results with gene expression of these immune-related genes. Finally, the knockdown of MMP14 decreased larvae survival to bacterial infections. Taken together, our data indicate that MMP14 selectively regulates the immune responses, and is required to defend against bacterial infections in O. furnacalis larvae. Conserved MMPs may serve as a potential target for pest control using a combination of double-stranded RNA and bacterial infection.
文摘Bacillus thuringiensis is a Gram-positive aerobic bacterium that produces insecticidal crystalline inclusions during sporulation phases of the mother cell. The vir- ulence factor, known as parasporal crystals, is composed of Cry and Cyt toxins. Most Cry toxins display a common 3-domain topology. Cry toxins exert intoxication through toxin activation, receptor binding and pore formation in a suitable larval gut environment. The mosquitocidal toxins of Bt subsp, israelensis (Bti) were found to be highly active against mosquito larvae and are widely used for vector control. Bt subsp, jegathesan is another strain which possesses high potency against broad range of mosquito larvae. The present review summarizes characterized receptors for Cry toxins in mosquito larvae, and will also discuss the diversity and effects of 3-D mosquitocidal Cry toxin and the ongo- ing research for Cry toxin mechanisms generated from investigations of lepidopteran and dipteran larvae.
文摘Spatial and temporal patterns of insect damage in relation to aflatoxin contamination in a corn field with plants of uniform genetic background are not well understood. After previous examination of spatial patterns of insect damage and aflatoxin in pre-harvest corn fields, we further examined both spatial and temporal patterns of cob- and kernel- feeding insect damage, and aflatoxin level with two samplings at pre-harvest in 2008 and 2009. The feeding damage by each of the ear/kernel-feeding insects (i.e., corn earworm/fall armyworm damage on the silk/cob, and discoloration of corn kernels by stink bugs) and maize weevil population were assessed at each grid point with five ears. Sampling data showed a field edge effect in both insect damage and aflatoxin contamination in both years. Maize weevils tended toward an aggregated distribution more frequently than either corn earworm or stink bug damage in both years. The frequency of detecting aggregated distribution for aflatoxin level was less than any of the insect damage assessments. Stink bug damage and maize weevil number were more closely associated with aflatoxin level than was corn earworm damage. In addition, the indices of spatial-temporal association (χ) demonstrated that the number of maize weevils was associated between the first (4 weeks pre-harvest) and second (1 week pre-harvest) samplings in both years on all fields. In contrast, corn earworm damage between the first and second samplings from the field on the Belflower Farm, and aflatoxin level and corn earworm damage from the field on the Lang Farm were dissociated in 2009.
基金the National Natural Science Foundation of China(31700141,31872027)Provincial Natural Science Foundation of Hunan(2019JJ50234)+1 种基金Changsha Science and Technology Project(kq 1901033)Double firstclass construction project of Hunan Agricultural University.
文摘ldentifying novel biocontrol agents and developing new strategies are urgent goals in insect pest biocontrol.Ascoviruses are potential competent insect viruses that may be developed into bioinsecticides,but this aim is impeded by their poor oral infectivity.To improve the per os infectivity of ascovirus,Bacillus thuringiensis kurstaki(Btk)was employed as a helper to damage the midgut of lepidopteran larvae(Helicoverpa armigera,Mythimna separata,Spodoptera frugiperda,and S.litura)in formulations with Heliothis virescens ascovirus isolates(HvAV-3h and HvAV-3j).Btk and ascovirus mixtures(Btk/HvAV-3h and B1k/HvAV-3j)were fed to insect larvae(3rd instar).With the exception of S.frugiperda larvae,which exhibited low mortality after ingesting Btk,the larvae of the other tested species showed three types of response to feeding on the formulas:type I,the tested larvae(H.armigera)were killed by Btk infection so quickly that insufficient time and resources remained for ascoviral invasion;type II,both Btk and the ascovirus were depleted by their competition,such that neither was successfully released or colonized the tissue;type II,Btk was eliminated by the ascovirus,and the ascovirus achieved systemic infection in the tested larvae.The feeding of Btk/ascovirus formulas led to a great reduction in larval diet consumption and resulted in a significant decrease in the emergence rate of H.armigera,M.separata,and S.litura larvae,which suggested that the formulas exerted marked oral control effects on both the contemporary individuals and the next generation of these tested pest species.
文摘Bacterial endosymbionts of sap-sucking insects provide their host with a num- ber of beneficial qualities,including the supply of nutrition,defense against parasitoids, and protection from heat stress.Damage to these bacterial associates can therefore have a negative impact on the fitness of their insect host.We evaluated observational and experi- mental factors regarding the normative hemlock woolly adelgid (Adelges tsugae Annand) (Hemiptera:Adelgidae)to help understand the roles of its three recently identified symbionts,including under heat stress conditions.The prevalence of A.tsugae's facultafive symbiont (Serratia symbiotica)was examined at different spatial scales to determine how variable infection rates are for this symbiont.There was no significant difference found in infection rates between adelgids on a tree,within a plot,or within a state.However, significantly more adelgids in Georgia (95%)had S.symbiotica compared to those in New York (68%).Microsatellite genotyping of the adelgids found that this difference was most likely not the result of a second introduction ofA.tsugae into eastern North America.Comparison orS.symbiotica proportions between first and fourth instars showed that symbiont absence did not affect the ability ofA.tsugae to survive aestivation.Evaluations of sym- biont densities within each adelgid found that when S.symbiotica was absent,the density of obligate symbionts was significantly higher.Exposure to heat stress (32.5℃)was not consistently correlated with changes in symbiont densities over a 4-d period.Overall,we have shown that symbiont prevalence and densities vary within the broad population of A.tsugae in eastern North America,with potentially significant effects upon the ecology of this important pest.
文摘Phytopathogen infections are frequently influenced by both biotic and abiotic factors in a crop field. The effect of brown stink bug, Euschistus servus (Hemiptera: Pentatomidae), feeding and planting date and sampling time on common smut (Ustilago maydis) infection percentage of maize plants was examined in 2005 and 2006, and 2010 and 2011, respectively. Brown stink bug adult feeding on maize hybrid "DKC6971" at flowering in 2005 and 2006 did not influence smut infection percentage when examined using 3 treatments (i.e., 0 adult, 5 adults, and 5 adults mixed with the smut spores). The smut infection percentages were 〈 3% (n =12) in the 3 treatments. The smut infection percentage among the 4 weekly samplings was the same, so was natural aflatoxin contamination at harvest among the treatments. The 2nd experiment showed that planting date did not affect the smut infection percentage in either 2010 or 2011. But, the smut infection percentage from the postflowering sampling was greater than preflowering sampling in both years. The smut infection percentage varied among the germplasm lines in 2010, but not in 2011. This study demonstrated that brown stink bug feeding at flowering had no effect on smut infection in maize, and the best time for smut evaluation would be after flowering. The temperature and precipitation might have also influenced the percentage of smut-infected maize plants during the 4 years when the experiments were conducted. The similarity between kernel-colonizing U. maydis and Aspergillus flavus infections and genotype × environment interaction were also discussed.
文摘The brown stink bug (BSB), Euschistus servus (Say)(Hemiptera: Pentatomidae), is a serious economic pest of corn production in the southeastern United States. The BSB population dynamics was mon itored for 17 weeks from tasseling to preharvest of corn plants (i.e., late May to mid-September) using pheromone traps in three corn fields from 2005 to 2009. The trap data showed two peaks in early June and mid-August, respectively. The relationship between trap catch and pregrowing season weather data was examined using correlation and stepwise multiple factor regression analyses. Weather indices used for the analyses were accumulated growing degree day (AGDD), number of days with minimum temperature below 0℃(Subz), accumulated daily maximum (AMaxT) and minimum temperatures (AMinT) and rainfall (ARain). The weather indices were calculated with lower (10℃) and upper (35℃) as biological thresholds. The parameters used in regression analysis were seasonal abundance (or overall mean of BSB adult catch)(BSBm), number of BSB adults caught at a peak (PeakBSB), and peak week (Peakwk). The BSBm was negatively related to high temperature (AmaxT or AGDD) consistently, whereas IstPeakBSB was positively correlated to both ARain and Subz, irrespective of weather data durations (the first 4, 4.5, and 5 months). In contrast, the 7-month weather data (AGDD7) were negatively correlated to the BSBm only, but not correlated to the second PeakBSB. The 5-year monitoring study demonstrated that weather data can be used to predict the BSB abundance at its first peak in tasseling corn fields in the southeastern U.S. states.
基金supported by two grants obtained from the Bill&Melinda Gates FoundationEnabling Research Tools for Cassava Virologists and Breeders,OPP1080766the African Cassava Whitefly Project,OPP1058938.
文摘In sub-Saharan Africa cassava growing areas,two members of the Bemisia tabaci species complex termed sub-Saharan Africa 1(SSA1)and SSA2 have been reported as the prevalent whiteflies associated with the spread of viruses that cause cassava mosaic disease(CMD)and cassava brown streak disease(CBSD)pandemics.At the peak of CMD pandemic in the late 1990s,SSA2 was the prevalent whitefly,although its numbers have diminished over the last two decades with the resurgence of SSA1 whiteflies.Three SSA1 subgroups(SGI to SG3)are the predominant whiteflies in East Africa and vary in distribution and biological properties.Mating compatibility between SSA1 subgroups and SSA2 whiteflies was reported as the possible driver for the resurgence of SSA 1 whiteflies.In this study,a combination of both phylogenomic methods and reciprocal crossing experiments were applied to determine species status of SSA1 subgroups and SSA2 white-fly populations.Phylogenomic analyses conducted with 26548205 bp whole genome single nucleotide polymorphisms(SNPs)and the full mitogenomes clustered SSA1 subgroups together and separate from SSA2 species.Mating incompatibility between SSA1 subgroups and SSA2 further demonstrated their distinctiveness from each other.Phylogenomic analyses conducted with SNPs and mitogenomes also revealed different genetic relationships among SSA1 subgroups.The former clustered SSA 1-SGI and SSA1-SG2 to-gether but separate from SSA1-SG3,while the latter clustered SSA1-SG2 and SSA1-SG3 together but separate from SSA 1-SG1.Mating compatibility was observed between SSA 1-SGI and SSA1-SG2,while incompatibility occurred between SSA 1-SGI and SSA1-SG3,and SSA 1-SG2 and SSA 1-SG3.Mating results among SSA 1 subgroups were coherent with phylogenomics results based on SNPs but not the full mitogenomes.Furthermore,this study revealed that the secondary endosymbiont--did not mediate reproductive success in the crossing assays carried out.Overall,using genome wide SNPs together with reciprocal crossings assays,this study established accurate genetic relationships among cassava-colonizing populations,illustrating that SSA1 and SSA2 are distinct species while at least two species occur within SSA1 species.
基金This study was funded in part by National Natural Science Foundation of China(31972297)Fundamental Research Funds for the Central Universities(SWU115073).
文摘Pesticide resistance and resurgence are serious problems often occurring simultaneously in the field.In our long-term study of a fenpropathrin-resistant strain of Tetranychus cinnabaribus,enhancement of detoxification and modified fecundity mechanisms were both observed.Here we investigate the network across these two mechanisms and find a key node between resistance and resurgence.We show that the ecdysone pathway is involved in regulating the fecundity of T.cinnabaribus.The concentration change of ecdysone is consistent with the fecundity curve;the concentration of ecdysone is higher in the fenpropathrin-resistant strain which has stronger fecundity.The enhancement of ecdysone is due to overexpression of two P450 genes(CYP314A1 and CYP315A1)in the ecdysone synthesis pathway.Silencing expression of these CYP genes resulted in lower concentration of ecdysone,reduced expression of vitellogenin,and reduced fecundity of T.cinnabaribus.The expression of CYP315A1 is regulated by transcription factors Cap-n-collar isoform C(CncC)and Musculoaponeurotic fibrosarcoma protein(Maf),which are involved in regulating other P450 genes functioning in detoxification of fenpropathrin in T.cinnabaribus.A similar regulation is established in citrus pest mite Panonychus citri showing that the CncC pathway regulates expression of PcCYP315Al,which affects mite fecundity.Transcription factors are activated to upregulate detoxification genes facilitating pesticide resistance,while the“one to multiple”regulation mode of transcription factors simultaneously increases expression of metabolic enzyme genes in hormone pathways and alters the physiology of pests.This is an important response of arthropods to pesticides which leads to resistance and population resurgence.
基金supported by the Science and Technology Innovation Project of the Chinese Academy of Agricultural Sciences(CAAS-2060302).
文摘Insect pest damage to crops is a threat to global food security(Tilman et al.,2011).Climate change,the evolution of insecticide resistance,and the phasing out of insecticides due to environmental and safety concerns exacerbate this problem.Farmers urgently need safe and effective crop protection tools to sustainably generate yields that meet ever-increasing global demand.
基金provided by the National Institutes of Health(R01AI033108,R01AI106892)awarded to MRS and MRBNational Science Foundation(IOS 1656236)awarded to MRS and MRB+3 种基金United States Department of Agriculture Hatch Project GEO00772 to MRSthe Pulliam Endowment(MRS)partially supported by the National Natural Science Foundation(31901876)the Natural Science Foundation of Jiangsu Province(KB20190900).
文摘Anautogenous mosquitoes must blood feed on a vertebrate host to produce eggs.Each gonadotrophic cycle is subdivided into a sugar-feeding previtellogenic phase that produces primary follicles and a blood meal-activated vitellogenic phase in which large numbers of eggs synchronously mature and are laid.Multiple endocrine factors including juvenile hormone(JH),insulin-like peptides(ILPs),ovary ecdysteroidogenic hormone(OEH),and 20-hydroxyecdysone(20E)coordinate each gonadotrophic cycle.Egg formation also requires nutrients from feeding that are stored in the fat body.Regulation of egg formation is best understood in Aedes aegypti but the role different endocrine factors play in regulating nutrient mobilization and storage remains unclear.In this study,we report that adult female Ae.aegypti maintained triacylglycerol(TAG)stores during the previtellogenic phase of the first gonadotrophic cycle while glycogen stores declined.In contrast,TAG and glycogen stores were rapidly mobilized during the vitellogenic phase and then replenishment.Several genes encoding enzymes with functions in TAG and glycogen metabolism were differentially expressed in the fat body,which suggested regulation was mediated in part at the transcriptional level.Gain of function assays indicated that stored nutrients were primarily mobilized by adipokinetic hormone(AKH)while juvenoids and OEH regulated replenishment.ILP3 further showed evidence of negatively regulating certain lipolytic enzymes.Loss of function assays indicated AKH depends on the AKH receptor(AKHR)for function.Altogether,our results indicate that the opposing activities of different hormones regulate nutrient stores during a gonadotrophic cycle in Ae.aegypti.
文摘DNA methylation is accomplished in animals by 2 classes of enzymes known as DNA methyltransferases, DNMT3 and DNMT 1, which perform de novo methylation and maintenance methylation, respectively. Several studies of hymenopteran eusocial insects suggest that DNA methylation is capable of influencing developmental plasticity. However, fundamental questions remain about the patterning of DNA methylation during the course of insect development. In this study, we performed quantitative real-time PCR (qPCR) on transcripts from the single-copy orthologs of DNMT1 and DNMT3 in the red imported fire ant, Solenopsis invicta. In particular, we assessed the expression of S. invicta Dnmtl and Dnmt3 mRNA during 7 stages of worker development, among behaviorally distinct adults, and among male and female gonads. Dnmt3 was most highly expressed during embryonic development, whereas Dnmtl was similarly expressed throughout the course of develop- ment. Moreover, Dnmtl and Dnmt3 were highly expressed in testes and ovaries. Neither Dnmt was significantly differentially expressed among heads of behaviorally distinct adult castes. Our results support the hypothesis that extensive patterning of DNA methylation occurs during gametogenesis and embryogenesis in the insect order Hymenoptera.