Two important mycotoxins, aflatoxin and fumonisin, are among the most potent naturally occurring carcinogens, contaminating maize(Zea mays) and affecting crop yield and quality.Resistance of maize to pre-harvest mycot...Two important mycotoxins, aflatoxin and fumonisin, are among the most potent naturally occurring carcinogens, contaminating maize(Zea mays) and affecting crop yield and quality.Resistance of maize to pre-harvest mycotoxin contamination, specifically aflatoxin produced by Aspergillus flavus and fumonisin produced by Fusarium verticillioides, is a goal in breeding programs that screen for these important traits with the aim of developing resistant commercial hybrids. We conducted two years of field evaluations on 87 inbred lines originating primarily in China and Mexico and not previously screened for resistance.The objectives of our study were to identify resistant germplasm for breeding purposes and to examine possible relationships between resistances to the two mycotoxins. Aflatoxin and fumonisin were present in samples harvested from all lines in both years.Concentrations of total aflatoxin ranged from 52.00 ± 20.00 to 1524.00 ± 396.00 μg kg^(-1),while those of fumonisin ranged from 0.60 ± 0.06 to 124.00 ± 19.50 mg kg^(-1). The inbred lines TUN15, TUN61, TUN37, CY2, and TUN49 showed the lowest aflatoxin accumulation and CN1, GT601, TUN09, TUN61, and MP717 the lowest fumonisin accumulation. TUN61 showed the lowest accumulation of both mycotoxins. This study confirmed previous observations that high levels of aflatoxin can coexist with fumonisin, with 55 maize lines showing a positive correlation coefficient between the concentrations of aflatoxin and fumonisin and 32 lines showing a negative correlation coefficient. These selected lines,particularly TUN61, may provide sources of resistance to mycotoxin contamination in breeding programs. However, the mechanism of resistance in this germplasm remains to be identified. Future research should also address factors that influence the fungus–plant interaction, such as herbivory and environmental stress.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
The yellow peach moth, Conogethes punctiferalis （Guenee）, a multivoltine species that overwinters as diapausing larvae, is one of the most serious insect pests on maize in China. Effect of photoperiod and temperatur...The yellow peach moth, Conogethes punctiferalis （Guenee）, a multivoltine species that overwinters as diapausing larvae, is one of the most serious insect pests on maize in China. Effect of photoperiod and temperature on larval diapause was examined under empirical laboratory conditions. Short-day treatments caused larval diapause at 25℃, and the critical photoperiod was between 12 and 13 h （or 12 h 51 min） light per day. No sensitive instar was identified for diapause induction under alternated short- （L ： D 11 ： 13 h） and long-day （L ： D 14 ： 10 h） treatments at different larval stages. However, accumulative treatment of three instars and 10 d under short-day treatment was required for the induction of 50% larval diapause. All larvae entered diapause at 20℃, whereas less than 3% did so at 30℃, irrespective of the long- or short-day treatment. Furthermore, under the short-day treatment, more than 90% of larvae went into diapause with temperatures ≤ 25℃, but less than 17% did so at 28℃. In contrast, under the long-day treatment, less than 19% of larvae went into diapause with temperatures ≥23 ℃. The forward shift （5℃） of critical temperature under the long-day regime demonstrated the compensatory effect of temperature and photoperiod on diapause induction. In conclusion, C. punctiferalis had a temperature-dependent type Ⅰ photoperiodic diapause response; there was no sensitive instar for diapause determination, but the photoperiodic accumulation time countermeasures both of the short-day cycles and the number ofinstars exposed, and the photoperiodic diapause response, was a temperature-compensated phenomenon.展开更多
MicroRNAs(miRNAs)are regulatory RNA molecules that bind to target messenger RNAs(mRNAs)and affect the stability or translational efficiency of the bound mRNAs.Single or dual-luciferase reporter systems have been succe...MicroRNAs(miRNAs)are regulatory RNA molecules that bind to target messenger RNAs(mRNAs)and affect the stability or translational efficiency of the bound mRNAs.Single or dual-luciferase reporter systems have been successfully used to identify miRNA target genes in mammalian cells.These reporter systems,however,are not sensitive enough to verify miRNA-target gene relationships in insect cell lines because the promoters of the target luciferase(usually Renilla)used in these reporter systems are too weak to drive sufficient expression of the target luciferase in insect cells.In this study,we replaced the SV40 promoter in the psiCHECK-2 reporter vector,which is widely used with mammalian cell lines,with the HSV-TK or AC5.1 promoter to yield two new dual-luciferase reporter vectors,designated psiCHECK-2-TK and psiCHECK-2-AC5.1,respectively.Only psiCHECK-2 and psiCHECK-2-AC5.1 had suitable target(7?enz7/a)/reference(firefly)luciferase activity ratios in mammalian(HeLa and HEK293)and insect(Sf9,S2,Helicoverpa zea fat body and ovary)cell lines,while psiCHECK-2-TK had suitable Renilla/firefly luciferase activity ratios regardless of the cell line.Moreover,psiCHECK-2-TK successfully detected the interaction between Helicoverpa armigera miRNA9a and its target,the 3'-untranslated region of heat shock protein 90,in both mammalian and H.zea cell lines,but psiCHECK-2 failed to do so in IT.zea cell lines.Furthermore,psiCHECK-2-TK with the target sequence,HzMasc(H.zea Masculinizer),accurately differentiated between H.zea cell lines with or without the negative regulation factor(miRNA or piRNA)of HzMasc.These data demonstrate that psiCHECK-2-TK can be used to functionally characterize small RNA target genes in both mammalian and insect cells.展开更多
While CrylAc has been known to bind with larval midgut proteins cad- herin, APN （amino peptidase N）, ALP （alkaline phosphatase） and ABCC2 （adenosine triphosphate-binding cassette transporter subfamily C2）, littl...While CrylAc has been known to bind with larval midgut proteins cad- herin, APN （amino peptidase N）, ALP （alkaline phosphatase） and ABCC2 （adenosine triphosphate-binding cassette transporter subfamily C2）, little is known about the recep- tors of Cry2Ab. To provide a clue to the receptors of Cry2Ab, we tested the baseline cytotoxicity of activated Cry 1Ac and Cry2Ab against the midgut and fat body cell lines of Helicoverpa zea and the ovary cell line ofSpodopterafrugiperda （SFg）. As expected, the descending order of cytotoxicity of CrylAc against the three cell lines in terms of 50% lethal concetration （LC50） was midgut （31.0μg/mL） 〉 fat body （59.0μg/mL） and SF9 cell （99.6μg/mL）. By contrast, the fat body cell line （LC50 = 7.55μg/mL） was about twice more susceptible to Cry2Ab than the midgut cell line （16.0/xg/mL）, the susceptibility of which was not significantly greater than that of SF9 cells （27.0μg/mL）. Further, ligand blot showed the binding differences between CrylAc and Cry2Ab in the three cell lines. These results indicated that the receptors of Cry2Ab were enriched in fat body cells and thus largely different from the receptors of CrylAc, which were enriched in midgut cells.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
Genetically engineered crops simultaneously produce defensive allelochemi-cals and Bacillus thuringiensis(Bt)toxin proteins to kill some of the world's most devastating insect pests.How the two types of toxins,whe...Genetically engineered crops simultaneously produce defensive allelochemi-cals and Bacillus thuringiensis(Bt)toxin proteins to kill some of the world's most devastating insect pests.How the two types of toxins,when ingested sequentially or simultaneously,interact at both lethal and sublethal doses in these pests remains underexplored.Here,we examined the toxicological interactions between the Bt toxin Cry 1 Ac and the flavonoid allelochemical flavone in Helicoverpa armigera.Simultaneous exposure of H.armigera neonates to lethal doses(LC25)of Cry 1 Ac and flavone caused a mortality significantly higher than that of either toxin alone and their expected additive mortality.Preexposure for 24 h to a sublethal dose(LC10)of Cry 1 Ac followed by 6-d simultaneous exposure to the same dose of Cry 1 Ac plus a lethal dose(1.6 mg/g diets,LC50)of flavone resulted in a mortality significantly higher than that of the LC50 dose of flavone alone and the expected additive mortality of the LC50 dose of flavone plus the LC10 dose of Cry 1 Ac.One-day preexposure to the sublethal dose(LC10)of flavone followed by 6-d simultaneous exposure to the LC50 dose(6 ng/cm2)of Cry 1 Ac plus the LC25 dose of flavone yielded a mortality significantly higher than that of the LC50 dose of Cry 1 Ac but similar to the expected additive mortality of the LC50 dose of Cry 1 Ac plus the LC50 dose of flavone.The results suggest that Cry 1 Ac induces and synergizes the toxicity of flavone against H.armigera larvae.展开更多
Insects utilize xenobiotic compounds to up-and downregulate cytochrome P450 monooxygenases(P450s)involved in detoxification of toxic xenobiotics including phytochemicals and pesticides.G-quadruplexes(G4)-forming DNA m...Insects utilize xenobiotic compounds to up-and downregulate cytochrome P450 monooxygenases(P450s)involved in detoxification of toxic xenobiotics including phytochemicals and pesticides.G-quadruplexes(G4)-forming DNA motifs are enriched in the promoter regions of transcription factors and function as cis-acting elements to regulate these genes.Whether and how P450s gain and keep G4 DNA motifs to regulate their expression still remain unexplored.Here,we show that CYP321A1,a xenobiotic-metabolizing P450 from Helicoverpa zea,a polyphagous insect of economic importance,has acquired and preserved a G4 DNA motif by selectively retaining a transposon known as HzIS1-3 that carries this G4 DNA motif in its promoter region.The HzIS1-3 G4 DNA motif acts as a silencer to suppress the constitutive and induced expression of CYP321A1 by plant allelochemicals flavone and xanthotoxin through folding into an intramolecular parallel or hybrid-1 conformation in the absence or presence of K^(+).The G4 ligand N-methylmesoporphyrin IX(NMM)strengthens the silencing effect of HzIS1-3 G4 DNA motif by switching its structure from hybrid-1 to hybrid-2.The enrichment of transposons in P450s and other environment-adaptation genes implies that selective retention of G4 DNA motif-carrying transposons may be the main evolutionary route for these genes to obtain G4 DNA motifs.展开更多
After examining ear-colonizing pest resistance, 20 maize lines from the USDA- ARS Germplasm Enhancement of Maize （GEM） Program were evaluated for whorl-feeding fall armyworm （FAW） （Spodopterafrugiperda） resistan...After examining ear-colonizing pest resistance, 20 maize lines from the USDA- ARS Germplasm Enhancement of Maize （GEM） Program were evaluated for whorl-feeding fall armyworm （FAW） （Spodopterafrugiperda） resistance using 4 maize inbred lines as the resistant and susceptible controls. Both FAW injury ratings at 7- and 14-d after infestation, and predator abundance and diversity at whorl stage （V6-V8） were recorded in 2009 and 2010. The survey of the diversity and abundance of predators in each experimental plot were conducted 7 d after the FAW infestation. Of the 20 germplasm lines examined, 3 of them （i.e., entries 9, 15, and 19 that were derived from tropical maize germplasm lines were originated from Uruguay, Cuba, and Thailand, respectively） were identified as the best FAW-resistant germplasm lines using the leaf injury ratings and predator survey data. In addition, the abundance and diversity of the predators were greater in 2010 than in 2009, which might have caused the low level of the FAW injury ratings on all lines examined in 2010. The 2-year data showed that the FAW injury ratings were negatively correlated to the predator abundance and diversity, which is also influence by genotype × environment interactions. The findings suggested that tropical germplasm is an important source of native resistance to the FAW and the corn earworm. At the same time, the maize genotype x environment interaction （e.g., predator attractiveness, and varying weather conditions） should be included in the multiple-year evaluations of insect and disease resistance of maize germplasm lines under field conditions.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 invasive Q biotype whitefly was first detected in the US on poinsettia in 2004 and is still not a pest outside of greenhouse environments in the US. To assess the potential for the establishment of the Q biotype o...The invasive Q biotype whitefly was first detected in the US on poinsettia in 2004 and is still not a pest outside of greenhouse environments in the US. To assess the potential for the establishment of the Q biotype on field crops, population cage experiments were conducted to compare the performance of a poinsettia-derived Q population named P＇06 on poinsettia and six field crops （alfalfa, tomato, melon, cotton, cowpea and cabbage）. P＇06 adults reared on poinsettia as nymphs laid eggs on all six field crops. Significantly more eggs were laid on alfalfa, tomato, melon and cotton than on cabbage, cowpea and poinsettia. These eggs hatched and the nymphs developed to adults on the six field crops. Relative to poinsettia, whitefly survival was similar on cowpea, alfalfa, tomato and cabbage, but significantly higher on cotton and melon. Moreover, P＇06 had significantly shorter development times from egg to adult on cotton, melon, cowpea, tomato and alfalfa than they did on poinsettia. However, the F1 adults raised on the six field crops had significantly shorter lifespans and laid 11- to 18-fold fewer eggs than did the F1 adults raised on poinsettia. Taken together, while P＇06 may have some potential to establish on field crops, the shorter lifespans and extremely low fectmdities of the F1 adults raised on the six field crops suggests that P＇06 is incapable of rapidly adapting to them. Poor adaptation to field crops may explain, at least partially, why the Q biotype has not established in the US field system.展开更多
Integrated pest management （IPM） has long been considered a profit- and product （or technology）-driven multidisciplinary research field that maximizes crop yield and minimizes pest-inflicted economic losses. The i...Integrated pest management （IPM） has long been considered a profit- and product （or technology）-driven multidisciplinary research field that maximizes crop yield and minimizes pest-inflicted economic losses. The introduction of transgenic crops has revolutionized crop protection and IPM by combining crop protection and genetics into one entity-the seed. Before the arrival of transgenic technology, studies of insect-plant interactions were frequently categorized under the field of ecology, and IPM programs were then the product of applied ecological research on suppressing pest populations in crop or livestock production.展开更多
基金partially supported by the U.S.Department of Agriculture-Agricultural Research Service(USDA-ARS)the Georgia Agricultural Commodity Commission for Corn+1 种基金the National Corn Growers AssociationAMCOE(Aflatoxin Mitigation Center of Excellence)
文摘Two important mycotoxins, aflatoxin and fumonisin, are among the most potent naturally occurring carcinogens, contaminating maize(Zea mays) and affecting crop yield and quality.Resistance of maize to pre-harvest mycotoxin contamination, specifically aflatoxin produced by Aspergillus flavus and fumonisin produced by Fusarium verticillioides, is a goal in breeding programs that screen for these important traits with the aim of developing resistant commercial hybrids. We conducted two years of field evaluations on 87 inbred lines originating primarily in China and Mexico and not previously screened for resistance.The objectives of our study were to identify resistant germplasm for breeding purposes and to examine possible relationships between resistances to the two mycotoxins. Aflatoxin and fumonisin were present in samples harvested from all lines in both years.Concentrations of total aflatoxin ranged from 52.00 ± 20.00 to 1524.00 ± 396.00 μg kg^(-1),while those of fumonisin ranged from 0.60 ± 0.06 to 124.00 ± 19.50 mg kg^(-1). The inbred lines TUN15, TUN61, TUN37, CY2, and TUN49 showed the lowest aflatoxin accumulation and CN1, GT601, TUN09, TUN61, and MP717 the lowest fumonisin accumulation. TUN61 showed the lowest accumulation of both mycotoxins. This study confirmed previous observations that high levels of aflatoxin can coexist with fumonisin, with 55 maize lines showing a positive correlation coefficient between the concentrations of aflatoxin and fumonisin and 32 lines showing a negative correlation coefficient. These selected lines,particularly TUN61, may provide sources of resistance to mycotoxin contamination in breeding programs. However, the mechanism of resistance in this germplasm remains to be identified. Future research should also address factors that influence the fungus–plant interaction, such as herbivory and environmental stress.
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.
文摘The yellow peach moth, Conogethes punctiferalis （Guenee）, a multivoltine species that overwinters as diapausing larvae, is one of the most serious insect pests on maize in China. Effect of photoperiod and temperature on larval diapause was examined under empirical laboratory conditions. Short-day treatments caused larval diapause at 25℃, and the critical photoperiod was between 12 and 13 h （or 12 h 51 min） light per day. No sensitive instar was identified for diapause induction under alternated short- （L ： D 11 ： 13 h） and long-day （L ： D 14 ： 10 h） treatments at different larval stages. However, accumulative treatment of three instars and 10 d under short-day treatment was required for the induction of 50% larval diapause. All larvae entered diapause at 20℃, whereas less than 3% did so at 30℃, irrespective of the long- or short-day treatment. Furthermore, under the short-day treatment, more than 90% of larvae went into diapause with temperatures ≤ 25℃, but less than 17% did so at 28℃. In contrast, under the long-day treatment, less than 19% of larvae went into diapause with temperatures ≥23 ℃. The forward shift （5℃） of critical temperature under the long-day regime demonstrated the compensatory effect of temperature and photoperiod on diapause induction. In conclusion, C. punctiferalis had a temperature-dependent type Ⅰ photoperiodic diapause response; there was no sensitive instar for diapause determination, but the photoperiodic accumulation time countermeasures both of the short-day cycles and the number ofinstars exposed, and the photoperiodic diapause response, was a temperature-compensated phenomenon.
基金This work was supported by the National Science Foundation of China(NSFC)-Henan Joint major grant(U2004206)the State Key Laboratory of Cotton Biology(CB2020A06).
文摘MicroRNAs(miRNAs)are regulatory RNA molecules that bind to target messenger RNAs(mRNAs)and affect the stability or translational efficiency of the bound mRNAs.Single or dual-luciferase reporter systems have been successfully used to identify miRNA target genes in mammalian cells.These reporter systems,however,are not sensitive enough to verify miRNA-target gene relationships in insect cell lines because the promoters of the target luciferase(usually Renilla)used in these reporter systems are too weak to drive sufficient expression of the target luciferase in insect cells.In this study,we replaced the SV40 promoter in the psiCHECK-2 reporter vector,which is widely used with mammalian cell lines,with the HSV-TK or AC5.1 promoter to yield two new dual-luciferase reporter vectors,designated psiCHECK-2-TK and psiCHECK-2-AC5.1,respectively.Only psiCHECK-2 and psiCHECK-2-AC5.1 had suitable target(7?enz7/a)/reference(firefly)luciferase activity ratios in mammalian(HeLa and HEK293)and insect(Sf9,S2,Helicoverpa zea fat body and ovary)cell lines,while psiCHECK-2-TK had suitable Renilla/firefly luciferase activity ratios regardless of the cell line.Moreover,psiCHECK-2-TK successfully detected the interaction between Helicoverpa armigera miRNA9a and its target,the 3'-untranslated region of heat shock protein 90,in both mammalian and H.zea cell lines,but psiCHECK-2 failed to do so in IT.zea cell lines.Furthermore,psiCHECK-2-TK with the target sequence,HzMasc(H.zea Masculinizer),accurately differentiated between H.zea cell lines with or without the negative regulation factor(miRNA or piRNA)of HzMasc.These data demonstrate that psiCHECK-2-TK can be used to functionally characterize small RNA target genes in both mammalian and insect cells.
文摘While CrylAc has been known to bind with larval midgut proteins cad- herin, APN （amino peptidase N）, ALP （alkaline phosphatase） and ABCC2 （adenosine triphosphate-binding cassette transporter subfamily C2）, little is known about the recep- tors of Cry2Ab. To provide a clue to the receptors of Cry2Ab, we tested the baseline cytotoxicity of activated Cry 1Ac and Cry2Ab against the midgut and fat body cell lines of Helicoverpa zea and the ovary cell line ofSpodopterafrugiperda （SFg）. As expected, the descending order of cytotoxicity of CrylAc against the three cell lines in terms of 50% lethal concetration （LC50） was midgut （31.0μg/mL） 〉 fat body （59.0μg/mL） and SF9 cell （99.6μg/mL）. By contrast, the fat body cell line （LC50 = 7.55μg/mL） was about twice more susceptible to Cry2Ab than the midgut cell line （16.0/xg/mL）, the susceptibility of which was not significantly greater than that of SF9 cells （27.0μg/mL）. Further, ligand blot showed the binding differences between CrylAc and Cry2Ab in the three cell lines. These results indicated that the receptors of Cry2Ab were enriched in fat body cells and thus largely different from the receptors of CrylAc, which were enriched in midgut cells.
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supported by the USDA National Institute of Food and Agriculture Hatch Project(No.ARZT-1370680-R31-172)National Science Foundation of China(NSFC)-Henan Joint major grant(No.U2004206)+1 种基金Key Scientific Research Projects of Colleges and Universities in Henan Province(No.21A210027)State Key Laboratory of Cotton Biology Open Fund(No.CB2020A06).
文摘Genetically engineered crops simultaneously produce defensive allelochemi-cals and Bacillus thuringiensis(Bt)toxin proteins to kill some of the world's most devastating insect pests.How the two types of toxins,when ingested sequentially or simultaneously,interact at both lethal and sublethal doses in these pests remains underexplored.Here,we examined the toxicological interactions between the Bt toxin Cry 1 Ac and the flavonoid allelochemical flavone in Helicoverpa armigera.Simultaneous exposure of H.armigera neonates to lethal doses(LC25)of Cry 1 Ac and flavone caused a mortality significantly higher than that of either toxin alone and their expected additive mortality.Preexposure for 24 h to a sublethal dose(LC10)of Cry 1 Ac followed by 6-d simultaneous exposure to the same dose of Cry 1 Ac plus a lethal dose(1.6 mg/g diets,LC50)of flavone resulted in a mortality significantly higher than that of the LC50 dose of flavone alone and the expected additive mortality of the LC50 dose of flavone plus the LC10 dose of Cry 1 Ac.One-day preexposure to the sublethal dose(LC10)of flavone followed by 6-d simultaneous exposure to the LC50 dose(6 ng/cm2)of Cry 1 Ac plus the LC25 dose of flavone yielded a mortality significantly higher than that of the LC50 dose of Cry 1 Ac but similar to the expected additive mortality of the LC50 dose of Cry 1 Ac plus the LC50 dose of flavone.The results suggest that Cry 1 Ac induces and synergizes the toxicity of flavone against H.armigera larvae.
基金supported by the National Natural Science Foundation of China(No.31701791)National Science Foundation of China(NSFC)-Henan Joint major grant(No.U2004206)+1 种基金the State Key Laboratory of Cotton Biology(No.CB2020A06)the USDA National Institute of Food and Agriculture Hatch Project(No.ARZT-1370680-R31-R31-172).
文摘Insects utilize xenobiotic compounds to up-and downregulate cytochrome P450 monooxygenases(P450s)involved in detoxification of toxic xenobiotics including phytochemicals and pesticides.G-quadruplexes(G4)-forming DNA motifs are enriched in the promoter regions of transcription factors and function as cis-acting elements to regulate these genes.Whether and how P450s gain and keep G4 DNA motifs to regulate their expression still remain unexplored.Here,we show that CYP321A1,a xenobiotic-metabolizing P450 from Helicoverpa zea,a polyphagous insect of economic importance,has acquired and preserved a G4 DNA motif by selectively retaining a transposon known as HzIS1-3 that carries this G4 DNA motif in its promoter region.The HzIS1-3 G4 DNA motif acts as a silencer to suppress the constitutive and induced expression of CYP321A1 by plant allelochemicals flavone and xanthotoxin through folding into an intramolecular parallel or hybrid-1 conformation in the absence or presence of K^(+).The G4 ligand N-methylmesoporphyrin IX(NMM)strengthens the silencing effect of HzIS1-3 G4 DNA motif by switching its structure from hybrid-1 to hybrid-2.The enrichment of transposons in P450s and other environment-adaptation genes implies that selective retention of G4 DNA motif-carrying transposons may be the main evolutionary route for these genes to obtain G4 DNA motifs.
文摘After examining ear-colonizing pest resistance, 20 maize lines from the USDA- ARS Germplasm Enhancement of Maize （GEM） Program were evaluated for whorl-feeding fall armyworm （FAW） （Spodopterafrugiperda） resistance using 4 maize inbred lines as the resistant and susceptible controls. Both FAW injury ratings at 7- and 14-d after infestation, and predator abundance and diversity at whorl stage （V6-V8） were recorded in 2009 and 2010. The survey of the diversity and abundance of predators in each experimental plot were conducted 7 d after the FAW infestation. Of the 20 germplasm lines examined, 3 of them （i.e., entries 9, 15, and 19 that were derived from tropical maize germplasm lines were originated from Uruguay, Cuba, and Thailand, respectively） were identified as the best FAW-resistant germplasm lines using the leaf injury ratings and predator survey data. In addition, the abundance and diversity of the predators were greater in 2010 than in 2009, which might have caused the low level of the FAW injury ratings on all lines examined in 2010. The 2-year data showed that the FAW injury ratings were negatively correlated to the predator abundance and diversity, which is also influence by genotype × environment interactions. The findings suggested that tropical germplasm is an important source of native resistance to the FAW and the corn earworm. At the same time, the maize genotype x environment interaction （e.g., predator attractiveness, and varying weather conditions） should be included in the multiple-year evaluations of insect and disease resistance of maize germplasm lines under field conditions.
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 invasive Q biotype whitefly was first detected in the US on poinsettia in 2004 and is still not a pest outside of greenhouse environments in the US. To assess the potential for the establishment of the Q biotype on field crops, population cage experiments were conducted to compare the performance of a poinsettia-derived Q population named P＇06 on poinsettia and six field crops （alfalfa, tomato, melon, cotton, cowpea and cabbage）. P＇06 adults reared on poinsettia as nymphs laid eggs on all six field crops. Significantly more eggs were laid on alfalfa, tomato, melon and cotton than on cabbage, cowpea and poinsettia. These eggs hatched and the nymphs developed to adults on the six field crops. Relative to poinsettia, whitefly survival was similar on cowpea, alfalfa, tomato and cabbage, but significantly higher on cotton and melon. Moreover, P＇06 had significantly shorter development times from egg to adult on cotton, melon, cowpea, tomato and alfalfa than they did on poinsettia. However, the F1 adults raised on the six field crops had significantly shorter lifespans and laid 11- to 18-fold fewer eggs than did the F1 adults raised on poinsettia. Taken together, while P＇06 may have some potential to establish on field crops, the shorter lifespans and extremely low fectmdities of the F1 adults raised on the six field crops suggests that P＇06 is incapable of rapidly adapting to them. Poor adaptation to field crops may explain, at least partially, why the Q biotype has not established in the US field system.
文摘Integrated pest management （IPM） has long been considered a profit- and product （or technology）-driven multidisciplinary research field that maximizes crop yield and minimizes pest-inflicted economic losses. The introduction of transgenic crops has revolutionized crop protection and IPM by combining crop protection and genetics into one entity-the seed. Before the arrival of transgenic technology, studies of insect-plant interactions were frequently categorized under the field of ecology, and IPM programs were then the product of applied ecological research on suppressing pest populations in crop or livestock production.
