Southern Insect Management Research Unit

Stoneville, MS, United States

Southern Insect Management Research Unit

Stoneville, MS, United States
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Yang Y.,Louisiana State University | Zhu Y.C.,Southern Insect Management Research Unit | Ottea J.,Louisiana State University | Husseneder C.,Louisiana State University | And 4 more authors.
Insect Science | Year: 2013

Diatraea saccharalis is a major corn borer pest. Midgut serine proteinases are essential for insect growth and development. Alteration of midgut proteinases is responsible for Bt resistance development in some species. To clone midgut trypsin and chymotrypsin cDNAs and to test if the Cry1Ab resistance in D. saccharalis is associated with changes in midgut proteinases, total midgut tryptic and chymotryptic activities, cDNA sequences, and gene expressions of three trypsin and three chymotrypsin genes were comparatively examined between Cry1Ab-susceptible (Cry1Ab-SS) and Cry1Ab-resistant (Cry1Ab-RR) strains. Full-length cDNAs encoding three trypsin- and three chymotrypsin-like proteinases were sequenced from Cry1Ab-SS and Cry1Ab-RR larvae. These cDNAs code for active forms of midgut serine proteinases with all functional motifs, including signal peptide, conserved His-Asp-Ser for the catalytic triad, three pairs of cysteines for disulfide bridge configurations, and conserved substrate specificity determination residues. In general, cDNA and putative protein sequences are highly similar between Cry1Ab-SS and Cry1Ab-RR strains, except for a few nucleotide and predicted amino acid substitutions, whose function need to be further clarified. Total trypsin and chymotrypsin activities were also similar between Cry1Ab-SS and Cry1Ab-RR strains. Transcriptional levels of the trypsin and chymotrypsin genes had numerical difference between Cry1Ab-SS and Cry1Ab-RR strains, but the difference was not statistically significant. Data suggest that the development of Cry1Ab resistance in D. saccharalis was not significantly associated with these trypsins and chymotrypsins. Results clarified the role of six midgut proteinases and provided a foundation for continuing examination of potential involvement of other midgut proteinases in Bt resistance development and other important biochemical processes. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.


Yang Y.,Louisiana State University | Zhu Y.C.,Southern Insect Management Research Unit | Ottea J.,Louisiana State University | Husseneder C.,Louisiana State University | And 5 more authors.
PLoS ONE | Year: 2011

The sugarcane borer, Diatraea saccharalis, is a major target pest of transgenic corn expressing Bacillus thuringiensis (Bt) proteins (i.e., Cry1Ab) in South America and the mid-southern region of the United States. Evolution of insecticide resistance in such target pests is a major threat to the durability of transgenic Bt crops. Understanding the pests' resistance mechanisms will facilitate development of effective strategies for delaying or countering resistance. Alterations in expression of cadherin- and alkaline phosphatase (ALP) have been associated with Bt resistance in several species of pest insects. In this study, neither the activity nor gene regulation of ALP was associated with Cry1Ab resistance in D. saccharalis. Total ALP enzymatic activity was similar between Cry1Ab-susceptible (Cry1Ab-SS) and -resistant (Cry1Ab-RR) strains of D. saccharalis. In addition, expression levels of three ALP genes were also similar between Cry1Ab-SS and -RR, and cDNA sequences did not differ between susceptible and resistant larvae. In contrast, altered expression of a midgut cadherin (DsCAD1) was associated with the Cry1Ab resistance. Whereas cDNA sequences of DsCAD1 were identical between the two strains, the transcript abundance of DsCAD1 was significantly lower in Cry1Ab-RR. To verify the involvement of DsCAD1 in susceptibility to Cry1Ab, RNA interference (RNAi) was employed to knock-down DsCAD1 expression in the susceptible larvae. Down-regulation of DsCAD1 expression by RNAi was functionally correlated with a decrease in Cry1Ab susceptibility. These results suggest that down-regulation of DsCAD1 is associated with resistance to Cry1Ab in D. saccharalis.


Jurat-Fuentes J.L.,University of Tennessee at Knoxville | Karumbaiah L.,University of Georgia | Jakka S.R.K.,University of Tennessee at Knoxville | Ning C.,Chinese Academy of Agricultural Sciences | And 8 more authors.
PLoS ONE | Year: 2011

Development of insect resistance is one of the main concerns with the use of transgenic crops expressing Cry toxins from the bacterium Bacillus thuringiensis. Identification of biomarkers would assist in the development of sensitive DNA-based methods to monitor evolution of resistance to Bt toxins in natural populations. We report on the proteomic and genomic detection of reduced levels of midgut membrane-bound alkaline phosphatase (mALP) as a common feature in strains of Cry-resistant Heliothis virescens, Helicoverpa armigera and Spodoptera frugiperda when compared to susceptible larvae. Reduced levels of H. virescens mALP protein (HvmALP) were detected by two dimensional differential in-gel electrophoresis (2D-DIGE) analysis in Cry-resistant compared to susceptible larvae, further supported by alkaline phosphatase activity assays and Western blotting. Through quantitative real-time polymerase chain reaction (qRT-PCR) we demonstrate that the reduction in HvmALP protein levels in resistant larvae are the result of reduced transcript amounts. Similar reductions in ALP activity and mALP transcript levels were also detected for a Cry1Ac-resistant strain of H. armigera and field-derived strains of S. frugiperda resistant to Cry1Fa. Considering the unique resistance and cross-resistance phenotypes of the insect strains used in this work, our data suggest that reduced mALP expression should be targeted for development of effective biomarkers for resistance to Cry toxins in lepidopteran pests. © 2011 Jurat-Fuentes et al.


Gore J.,Mississippi State University | Cook D.R.,Mississippi State University | Catchot A.L.,Mississippi State University | Musser F.R.,Mississippi State University | And 7 more authors.
Journal of Cotton Science | Year: 2013

Twospotted spider mite, Tetranychus urticae (Koch), has become a significant early season pest of cotton, Gossypium hirsutum L., in the midsouthern U.S. Sixteen experiments were conducted across the midsouthern U. S. to determine the impact of twospotted spider mite infestation timing on cotton injury, stunting, and yields. Twospotted spider mites from a greenhouse colony were used to initiate infestations at the three-leaf stage, at first flower, and at 200 heat unit intervals after first flower. Twospotted spider mite injury on a scale of zero to five (0 = no injury, 5 = severe injury), plant stunting, and final cotton yields were measured. In general, all infestation timings had higher injury ratings compared to the uninfested control. The highest injury ratings were observed for the three-leaf and first flower infestations. Additionally, infestations at the three-leaf stage caused more plant stunting than later infestation timings. In most of the experiments, the three-leaf infestation resulted in significant stunting of cotton plants. For cotton yields, early infestations caused the greatest yield losses. Significant yield losses compared to the untreated control were observed for infestations initiated up to first flower plus 800 heat units. These results suggest that cotton should be protected from twospotted spider mite infestations beyond that point in the growing season. Results from this experiment will be used to improve integrated pest management of twospotted spider mite in cotton. © The Cotton Foundation 2013.


Gunawardena D.A.,Texas A&M University | Fernando S.D.,Texas A&M University | Fernando T.J.,Texas A&M University | Perera O.P.,Southern Insect Management Research Unit
Biological Engineering Transactions | Year: 2012

Fuel cells with enzyme-coated electrodes, commonly known as enzymatic fuel cells, are closely looked at as a means to power implantable medical devices and miniaturized bioelectronic devices such as biomicroeletromechanical or nanoelectromechanical systems (bioMEMS/NEMS). This study attempts to develop a fuel cell with the proton exchange membrane (PEM) totally replaced by an enzyme coating tethered only to one electrode (anode). It was conjectured that the specificity of the enzyme to only a specific substrate at the anode coupled with the selectivity of reactions that could occur at the cathode due to thermodynamic preferences will discourage crossover reactions, making the PEM elimination possible. In the anode, lactate dehydrogenase (LDH), a NAD-dependent oxidoreductase, was immobilized on a gold-coated electrode using a layer-by-layer assembly technique. The LDH-coated anode catalyzed the oxidation of lactate to pyruvate, while Pt was used to catalyze the reduction of oxygen to water. Three parameters were selected to elucidate the behavior of the fuel cell under different load conditions. These parameters (lactate concentration, fuel cell temperature, and feed flow rate) were varied within the human physiological range to evaluate the performance as an implantable fuel cell. The cell reported an average open-circuit voltage of 261.72 ±0.01 mV, power density of 360.6 nW cm -1, and voltage efficiency of 25.05%. This experiment demonstrated that total elimination of the PEM is possible via coating only one electrode with a substrate-specific enzyme. This is a significant step toward developing power supplies for bioelectronic devices via enzymatic fuel cells, since elimination of the PEM enables unprecedented simplification of the fuel cell architecture (for miniaturization) while eliminating a component that contributes to significant internal resistance. © 2012 ASABE.


Owen L.N.,Mississippi State University | Catchot A.L.,Mississippi State University | Musser F.R.,Mississippi State University | Gore J.,Mississippi State University | And 3 more authors.
Crop Protection | Year: 2013

Field experiments were conducted during 2009 and 2010 to evaluate the effects of defoliation on maturity group IV soybeans, Glycine max (L.) Merr., grown in Mississippi. During each year, two locations were planted with maturity group IV soybeans that were subjected to various levels of defoliation during R3, R5, and R6 growth stages. Soybeans were subjected to various levels of defoliation within the upper 50% of the plant canopy, lower 50% of the plant canopy, and whole-plant canopy. There was greater yield loss from defoliation occurring in the upper plant canopy compared with the lower plant canopy during R3 and R5 stages, but no difference between canopy regions during R6 stage. Yield loss from whole plant defoliation was greater than upper or lower canopy defoliation. Results confirmed that soybeans during R3 and R5 stages are more susceptible to yield loss than during R6. However, yield losses were not significantly different between R 3 and R5 until defoliation exceeded 63%. Dynamic economic injury levels were determined for each growth stage based on yield loss equations, value of the crop, and cost of control and can be used as a basis for developing action thresholds in high-yielding soybean production environments. © 2013.


Owen L.N.,Mississippi State University | Catchot A.L.,Mississippi State University | Musser F.R.,Mississippi State University | Gore J.,Mississippi State University | And 2 more authors.
Florida Entomologist | Year: 2013

Field populations of soybean looper, Chrysodeixis includens (Walker) (Noctuidae), were collected from soybean, Glycine max (L.) Merr., fields in Mississippi and Louisiana during 2010 and 2011 to determine their susceptibility to novel insecticides. Flubendiamide and chloran-traniliprole are diamide insecticides that have recently been registered for use in field crops. Baseline data were collected for each of these insecticides as well as for methoxyfenozide, which has been the recommended insecticide for soybean looper in Mississippi soybeans prior to the introduction of these new novel insecticides. Mean LC50 values for flubendiamide and chlorantraniliprole were similar among the populations tested, and susceptibility was higher for methoxyfenozide compared to flubendiamide and chlorantraniliprole. Diet incorporated assays determined a 9.4-fold variation in susceptibility to flubendiamide among the 7 soybean looper populations tested. Variation to chlorantraniliprole was 6.25-fold and variation for methoxyfenozide was 5.37-fold. Variation in the diamide insecticides was higher than methoxyfenozide with less exposure to soybean looper populations. Documenting variability along with baseline data will be useful in the future for resistance monitoring of soybean loopers to diamide insecticides.


Zhu Y.C.,Southern Insect Management Research Unit | Guo Z.,Southern Insect Management Research Unit | He Y.,Zhejiang Academy of Agricultural Sciences | Luttrell R.,Southern Insect Management Research Unit
PLoS ONE | Year: 2012

The tarnished plant bug has become increasingly resistant to organophosphates in recent years. To better understand acephate resistance mechanisms, biological, biochemical, and molecular experiments were systematically conducted with susceptible (LLS) and acephate-selected (LLR) strains. Selection of a field population with acephate significantly increased resistance ratio to 5.9-fold, coupled with a significant increase of esterase activities by 2-fold. Microarray analysis of 6,688 genes revealed 329 up- and 333 down-regulated (≥2-fold) genes in LLR. Six esterase, three P450, and one glutathione S-transferase genes were significantly up-regulated, and no such genes were down-regulated in LLR. All vitellogenin and eggshell protein genes were significantly down-regulated in LLR. Thirteen protease genes were significantly down-regulated and only 3 were up-regulated in LLR. More than twice the number of catalysis genes and more than 3.6-fold of metabolic genes were up-regulated, respectively, as compared to those down-regulated with the same molecular and biological functions. The large portion of metabolic or catalysis genes with significant up-regulations indicated a substantial increase of metabolic detoxification in LLR. Significant increase of acephate resistance, increases of esterase activities and gene expressions, and variable esterase sequences between LLS and LLR consistently demonstrated a major esterase-mediated resistance in LLR, which was functionally provable by abolishing the resistance with esterase inhibitors. In addition, significant elevation of P450 gene expression and reduced susceptibility to imidacloprid in LLR indicated a concurrent resistance risk that may impact other classes of insecticides. This study demonstrated the first association of down-regulation of reproductive- and digestive-related genes with resistance to conventional insecticides, suggesting potential fitness costs associated with resistance development. This study shed new light on the understanding of the molecular basis of insecticide resistance, and the information is highly valuable for development of chemical control guidelines and tactics to minimize resistance and cross-resistance risks.


PubMed | Southern Insect Management Research Unit
Type: Journal Article | Journal: PloS one | Year: 2012

The tarnished plant bug has become increasingly resistant to organophosphates in recent years. To better understand acephate resistance mechanisms, biological, biochemical, and molecular experiments were systematically conducted with susceptible (LLS) and acephate-selected (LLR) strains. Selection of a field population with acephate significantly increased resistance ratio to 5.9-fold, coupled with a significant increase of esterase activities by 2-fold. Microarray analysis of 6,688 genes revealed 329 up- and 333 down-regulated (2-fold) genes in LLR. Six esterase, three P450, and one glutathione S-transferase genes were significantly up-regulated, and no such genes were down-regulated in LLR. All vitellogenin and eggshell protein genes were significantly down-regulated in LLR. Thirteen protease genes were significantly down-regulated and only 3 were up-regulated in LLR. More than twice the number of catalysis genes and more than 3.6-fold of metabolic genes were up-regulated, respectively, as compared to those down-regulated with the same molecular and biological functions. The large portion of metabolic or catalysis genes with significant up-regulations indicated a substantial increase of metabolic detoxification in LLR. Significant increase of acephate resistance, increases of esterase activities and gene expressions, and variable esterase sequences between LLS and LLR consistently demonstrated a major esterase-mediated resistance in LLR, which was functionally provable by abolishing the resistance with esterase inhibitors. In addition, significant elevation of P450 gene expression and reduced susceptibility to imidacloprid in LLR indicated a concurrent resistance risk that may impact other classes of insecticides. This study demonstrated the first association of down-regulation of reproductive- and digestive-related genes with resistance to conventional insecticides, suggesting potential fitness costs associated with resistance development. This study shed new light on the understanding of the molecular basis of insecticide resistance, and the information is highly valuable for development of chemical control guidelines and tactics to minimize resistance and cross-resistance risks.

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