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United States Department of Agriculture

Agricultural Research Service

Brenda S. Oppert

Research Molecular Biologist

Photo of Dr. Brenda Oppert

Dr. Brenda Oppert
Research Molecular Biologist

Stored Product Insect & Engineering Research Unit
Center for Grain & Animal Health Research

1515 College Avenue
Manhattan, KS  66502

Voice: (785) 776-2780
Fax: (785) 537-5584

Educational / Professional Background

Dr. Oppert received B.S. and M.S. degrees in biology from the University of Texas at El Paso. She received a Ph.D. in the area of protein biochemistry from Kansas State University in 1991. Since that time, Dr. Oppert has worked at CGAHR in the area of insect gut biochemistry.

Research Interests

Our research mission is to find better, safer ways to control insect pests found in and around food storage areas, including grain storage and processing facilities and warehouses. Often these pests are even smaller than field pests and provide challenges when trying to understand basic digestive processes and physiological responses. Therefore, we have adopted a number of proteomics and genomics techniques, including 2-D gel analysis, multiphase chromatography, protein identification by sequencing, peptide fingerprinting and mass spec, subgenome characterization, and gene expression. Specific research areas include the use of proteomics and genomics to understand insect responses to digestive proteinase inhibitors and microbial toxins. Comparisons of differential responses in insects have been particularly enlightening. This research will lead to improved control methods for stored product pests.

Current Research Projects

Functional Genomics Applied To Stored Product Pest Problems
New insect control products for storage pests are urgently needed to replace those that are undergoing deregulation or to circumvent resistant pest populations. With the sequencing of the red flour beetle genome, we now have new tools to develop control products based on vulnerabilities in the biology of the beetle. We developed microarrays that contain representative sequences from each gene in the red flour beetle genome to identify sequences that are highly expressed in a particular tissue. Initial studies have identified gut transcripts as potential new targets for biopesticides. Beetle genome microarrays are also being used to probe the beetle's response to dietary inhibitors, toxins, and current control products, such as phosphine. We've found that beetle larvae fed dietary inhibitors mount a complex genetic response to survive. This information has provided us with details about genes that are transcribed by the beetle to survive inhibitor damage, and also genes that encode enzymes critical to digestion of protein in the diet. Because a closely related beetle, the yellow mealworm, has no sequenced genome, we are using high throughput sequencing to identify highly expressed genes in the gut of mealworm larvae. By comparing genetic transcripts in mealworm larvae exposed or not to a bacterial toxin, we are beginning to understand the complex response of mealworm larvae to toxins. All functional genomics applications are highly dependent on sophisticated bioinformatics algorithms, which we are developing to analyze insect sequences and data. As we identify potential new targets for biopesticides, we are using high throughput bioassays to evaluate purified proteins, peptides, or a process of interfering in the synthesis of genetic transcripts, called RNA interference. Biopesticides have applications in the integrated pest management of storage pests in sprays, formulations, or transgenic cereals. (Cooperators: Drs. Jeff Lord, Jeff Fabrick, Juan Luis Jurat-Fuentes, Elena Elpidina, John Tomich)

Discovery of More Effective Insect Control Proteins
Proteins that negatively impact insect growth and development are useful in insect control, because genes encoding insecticidal proteins can be expressed in plants to enhance host plant resistance. Proteinase inhibitors are good candidates because they disrupt insect digestion. However, insects can compensate for proteinase inhibitors by increasing the expression of digestive proteinases and/or expressing inhibitor-insensitive proteinases. Dr. Oppert was part of a team that discovered that combinations of digestive inhibitors targeting different proteinase classes provided better control of some stored product pests. Testing of other proteins by the research group led to the identification of vitamin-binding proteins that were also effective in the control of some stored product pests. Genes for these proteins can be expressed in wheat, maize, and other cereals to reduce pest damage to these products.

Biochemical Techniques Developed To Evaluate Proteinases In Mixtures
Insect proteinases are being investigated to identify those that may be targeted by biopesticides. The study of stored product insect proteinases is complicated by the small size of the insect, and the collection of sufficient quantities of digestive proteinases for purification is problematic. Dr. Oppert developed two major techniques that facilitate the analysis of complex mixtures of proteinases. One technique is a fast, simple, and economical microplate assay (see Oppert et al., 1997b). The other technique provides both a qualitative and quantitative identification of proteinases in the mixture (see Oppert and Kramer, 1998). These techniques have promoted rapid and efficient identification of digestive proteinases in moth and beetle pests of stored products. Researchers from areas other than agriculture have used these assays to study proteinases prior to purification.

Elucidation of Insect Resistance To Bacillus Thuringiensis
Proteinaceous toxins from the bacterium Bacillus thuringiensis (Bt) have been used for years in spray applications to control insect pests. Genes encoding these toxins are now being expressed in plants to control crop pests. Expression of Bt toxins in plants will increase exposure levels to insects for longer periods, thus providing increased selection pressure for the survival of resistant populations of pests. Insects can adapt to Bt toxins through an alteration in the gut receptor that binds the toxin in the early stages of toxicity. Through her work with digestive proteinases of the Indianmeal moth, a major pest of stored products, Dr. Oppert described a novel mechanism of insect resistance to Bt. Some Bt-resistant Indianmeal moths have reduced digestive proteinase activity that enables them to survive on diets containing Bt toxins. This was the first evidence of multiple adaptations in insects that result in a loss of Bt toxin efficacy. Information from this research is being used in the design of more efficient microbial toxins and in the development of effective resistance management policies.

Project Information
A digestive prolyl carboxypeptidase in Tenebrio molitor larvae
Prolyl carboxypeptidase (PRCP) is a serine peptidase that cleaves specifically at proline amino acids in proteins, which are abundant in cereals. The study of PRCP is important because it has been described in the regulation of physiological processes in different organisms, but, it has not been studied extensively in insects. We discovered that PRCP is an important enzyme in the digestion of proteins in cereals for the yellow mealworm, Tenebrio molitor, and, we purified and characterized the enzyme, providing the first detailed analysis of PRCP in insects. Our data indicates that the complex of digestive enzymes found in this insect may be adaptations of mammalian lysozyme enzymes during evolution, in this case to allow the insect to digest cereal proteins enriched in proline amino acids. Therefore, the enzyme may be a target for the development of new control methods to prevent damage to stored grains and products.

Characterization of cDNAs encoding serine proteases and their transcriptional responses to Cry1Ab protoxin in the gut of Ostrinia nubilalis larvae
Insect peptidases affect the efficacy of insecticidal microbial toxins, such as those from the bacterium Bacillus thuringiensis (Bt). Thus, understanding the expression of peptidase genes in a target pest is important to more effectively design and deploy Bt toxins. Larvae of the European corn borer, Ostrinia nubilalis, a major target of Bt transgenic corn, express a suite of peptidases at various locations in the gut. Our data suggest that peptidase genes can be grouped by genetic relatedness and expression patterns in the gut. We found that some genes were increased in expression when larvae were exposed to toxin. These data represent the most comprehensive study to date on the effect of Bt toxin on the expression of larval gut peptidase genes in the O. nubilalis. The data can be used to improve transgenic constructs for efficacy and durability in the field.

Expression of an endoglucanase from Tribolium castaneum (TcEG1) in Saccharomyces cerevisiae
Some insects have enzymes that can efficiently process plant material, and thus these enzymes may have applications in the biofuels industry. One such enzyme comes from the red flour beetle, Tribolium castaneum, which we previously identified as a potential plant-processing enzyme in extreme conditions, such as very alkaline environments. We put the gene for this enzyme in a yeast system to further study its properties. The yeast-expressed enzyme was similar to that of the beetle enzyme, demonstrating that expression of the gene in different systems does not disrupt the activity of the protein. We speculate that this enzyme may be useful in cases where harsh alkaline conditions are necessary for processing of plant materials for applications such as biofuels.

Bacillus thuringiensis Cry3Aa protoxin intoxication of Tenebrio molitor induces widespread changes in the expression of serine peptidase transcripts
Some insecticides are based on toxins produced by bacteria or other microbes, but these insecticides often don’t work well for beetle pests. In order to make these microbial toxins more effective for controlling beetles, we need to understand how they kill the insect. Most of the microbial toxins used for insect control are produced by the bacterium Bacillus thuringiensis, and we used one of these toxins in our study. We know that there are enzymes in the beetle gut that are involved in activating the toxin and making it soluble so that it can bind to the lining of the insect gut. Binding of the toxin starts a chain of events that we still don’t fully understand, but leads to killing the insect. To better understand this process, we determined how many enzymes are in the gut of mealworm larvae, and what changes are induced in these enzymes when mealworm larvae are fed toxin. Our results suggest that that mealworm larvae exposed to toxin are attempting to decrease toxicity of the toxin while maintaining efficient digestion. Knowledge of how the gut enzymes in mealworm larvae are affected by microbial toxins may help us to improve these important biopesticides for beetle pest control.

Cysteine digestive peptidases function as post-glutamine cleaving enzymes in tenebrionid stored-product pests
To be successful, stored product pests need to have enzymes capable of efficiently digesting their main dietary proteins, which have many glutamine and proline amino acids. We describe for the first time one enzyme, a glutamine-specific peptidase, in the gut of Tenebrio molitor larvae that are capable of digesting proteins by hydrolyzing at glutamine residues. Our characterization of these peptidases indicates that they are previously studied enzymes belonging to the class of cysteine peptidases, hypothesized to have evolved in storage pests to protect the insect from serine protease inhibitors found in cereals. We now propose that storage pests also have retained cysteine peptidases to efficiently digest cereal proteins. These results may be exploited to develop new control products for storage pests.

Transcriptome profiling of the intoxication response of Tenebrio molitor larvae to Bacillus thuringiensis Cry3Aa protoxin
Responses of coleopteran storage pests to microbial toxins has not been well-studied. We used high throughput sequencing to determine the effect of Bacillus thuringiensis Cry3Aa protoxin on transcript expression in the gut of Tenebrio molitor larvae. Transcripts associated with mitochondrial respiration, membrane restructuring, immunity, and signaling were increased, while transcripts associated with the metabolism of food and storage proteins were repressed in Cry3Aa-intoxicated larvae. Knowledge of the intricate responses to toxin in intoxicated larvae can provide information critical to the improvement of microbial toxins for coleopteran pest control.

Microarray analysis reveals strategies of Tribolium castaneum larvae to compensate for cysteine and serine protease inhibitors
Previously, our studies determined that flour beetle larvae respond to dietary inhibitors by shifting from one class of proteases to another. This response is problematic if cereal inhibitors are to be incorporated into IPM strategies for storage pest control. To study this at the gene level, whole-genome microarrays were used to evaluate the inhibitor response. The data demonstrated that the response by beetle larvae to dietary inhibitors involves a complicated adjustment of gene expression. However, the study also provided clues as to how to better utilize inhibitors for beetle pest control. Therefore, effective control of beetles may soon be possible with a strategy that can anticipate beetle responses to inhibitors.

Agricultural Research Service (ARS) News
Magazine Articles
Avidin: An Egg-Citing Insecticidal Protein in Corn
News, Miscellaneous
Missing Enzyme Linked to Bt-Resistance in Insects

Recent Publications
Article Link Klocko, A.L., R. Meilan, R.R. James, V. Viswanath, C. Ma, P. Payne, L. Miller, J.S. Skinner, B. Oppert, G.A. Cardineau, and S.H. Strauss. 2014. Bt-Cry3Aa transgene expression reduces insect damage and improves growth in field-grown hybrid poplar. Can. J. For. Res. 44: 28-35.
Article Link Liu, C., Y. Xiao, X. Li, B.S. Oppert, B.E. Tabashnik, and K. Wu. 2014. Cis-mediated down-regulation of a trypsin gene associated with Bt resistance in cotton bollworm. Sci. Rep. 4: 7219.
pdf icon PDF Semashko, T.A., E.A. Vorotnikova, V.F. Sharikova, K.S. Vinokurov, Y.A. Smirnova, Y.E. Dunaevsky, M.A. Belozersky, B. Oppert, E.N. Elpidina. 2014. Selective chromogenic and fluorogenic peptide substrates for the assay of cysteine peptidases in complex mixtures. Anal. Biochem. 449: 179-187.
pdf icon PDF Goptar, I.A., D.A. Shagin, I.A. Shagina, E.S. Mudrik, Y.A. Smirnova, D.P. Zhuzhikov, Y.E. Dunaevsky, B.S. Oppert, I.Y. Filippova, and E.N. Elipidina. 2013. A digestive prolyl carboxypeptidase in Tenebrio molitor larvae. Insect Biochem. Mol. Biol. 43: 501:509.
pdf icon PDF Oppert, B., and T.D. Morgan. 2013. Improved high-throughput bioassay for Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae). J. Stored Prod. Res. 52: 68-73.
pdf icon PDF Gao, Y., B.S. Oppert, J.C. Lord, C. Liu, and Z. Lei. 2012. Bacillus thuringiensis Cry3Aa toxin increases the susceptibility of Crioceris quatuordecimpunctata to Beauveria bassiana infection. J. Invertebr. Pathol. 109: 260-263.
pdf icon PDF Goptar, I.A., T.A. Semashko, S.A. Danilenko, E.N. Lysogorskaya, E.S. Oksenoit, D.P. Zhuzhikov, M.A. Belozersky, Y.E. Dunaevsky, B. Oppert, I.Y. Filippova, and E.N. Elpidina. 2012. Cysteine digestive peptidases function as post-glutamine cleaving enzymes in tenebrionid stored-product pests. Comp. Biochem. Physiol. Part B 161: 148-154.
pdf icon PDF Oppert, B., A.G. Martynov, and E.N. Elpidina. 2012. Bacillus thuringiensis Cry3Aa protoxin intoxication of Tenebrio molitor induces widespread changes in the expression of serine peptidase transcripts. Comp. Biochem. Physiol. Part D 7: 233-243.
pdf icon PDF Oppert, B.S., S.E. Dowd, P. Bouffard, L. Li, A. Conesa, M.D. Lorenzen, M. Toutges, J. Marshall, D.L. Huestis, J.A. Fabrick, C. Oppert, and J.L. Jurat-Fuentes. 2012. Transcriptome profiling of the intoxication response of Tenebrio molitor larvae to Bacillus thuringiensis Cry3Aa protoxin. PLoS ONE 7(e34624), 12 pp.
pdf icon PDF Valadez-Lira, J.A., J.M. Alcocer-Gonzalez, G. Damas, G. Nuñez-Mejiá, B. Oppert, C. Rodriguez-Padilla, and P. Tamez-Guerra. 2012. Comparative evaluation of phenoloxidase activity in different larval stages of four lepidopteran pests after exposure to Bacillus thuringiensis. J. Insect Sci. 12(80),11 pp.
Article Link Yao, J., L.L. Buschman, B. Oppert, C. Khajuria, and K.Y. Zhu. 2012. Characterization of cDNAs encoding serine proteases and their transcriptional responses to Cry1Ab protoxin in the gut of Ostrinia nubilalis larvae. PloS ONE 7(8): e44090.
pdf icon PDF Gao, Y., J. L. Jurat-Fuentes, B. Oppert, J.A. Fabrick, C. Liu, J. Gao, and Z. Lei. 2011. Increased toxicity of Bacillus thuringiensis Cry3Aa against Crioceris quatuordecimpunctata, Phaedon brassicae and Colaphellus bowringi by a Tenebrio molitor cadherin fragment. Pest Manag. Sci. 67: 1076-1081.
pdf icon PDF Oppert, B., T.D. Morgan, and K.J. Kramer. 2011. Efficacy of Bacillus thuringiensis Cry3Aa protoxin and protease inhibitors against coleopteran storage pests. Pest Manag. Sci. 67: 568-573.
Article Link Toutges, M.J., K.L. Hartzer, J.C. Lord, and B.S. Oppert. 2011. Evaluation of reference genes for quantitative polymerase chain reaction across life cycle stages and tissue types of Tribolium castaneum. J. Agric. Food Chem. 58: 8948-8951.
pdf icon PDF Willis, J.D., B.S. Oppert, C. Oppert, W.E. Klingeman, and J.L. Jurat-Fuentes. 2011. Identification, cloning, and expression of a GHF9 cellulase from Tribolium castaneum (Coleoptera: Tenebrionidae). J. Insect Physiol. 57: 300-306.
pdf icon PDF Dubovenko, A.G., Y.E. Dunaevsky, M.A. Belozersky, B. Oppert, J.C. Lord, and E.N. Elpidina. 2010. Trypsin-like proteins of the fungi as possible markers of pathogenicity. Fungal Biol. 114: 151-159.
pdf icon PDF Gao, Y., Y. Hu, Q. Fu, J. Zhang, B.S. Oppert, F. Lai, and Z. Zhang. 2010. Screen of Bacillus thuringiensis toxins for transgenic rice to control Sesamia inferens and Chilo suppressalis. J. Invertebr. Pathol. 105: 11-15.
pdf icon PDF Liu, C., Y. Gao, C. Ning, K. Wu, B.S. Oppert, and Y. Gao. 2010. Antisera-mediated in vivo reduction of Cry1Ac toxicity in Helicoverpa armigera. J. Insect Physiol. 56: 718-724.
pdf icon PDF Lord, J.C., K. Hartzer, M. Toutges, and B. Oppert. 2010. Evaluation of quantitative PCR reference genes for gene expression studies in Tribolium castaneum after fungal challenge. J. Microbiol. Meth. 80: 219-221.
pdf icon PDF Oppert B.S., E.N. Elpidina, M. Toutges, and S. Mazumdar-Leighton. 2010. Microarray analysis reveals strategies of Tribolium castaneum larvae to compensate for cysteine and serine protease inhibitors. Comp. Biochem. Physiol. Part D 5: 280-287.
pdf icon PDF Oppert, B.S. 2010. Rapid bioassay to screen potential biopesticides in Tenebrio molitor larvae. Biopestic. Int. 6: 67-73.
pdf icon PDF Oppert, B.S., R.T. Ellis, and J. Babcock. 2010. Effects of Cry1F and Cry34Ab1/35Ab1 on storage pests. J. Stored Prod. Res. 46: 143-148.
pdf icon PDF Oppert, C., W.E. Klingeman, J.D. Willis, B. Oppert, and J.L. Jurat-Fuentes. 2010. Prospecting for cellulolytic activity in insect digestive fluids. Comp. Biochem. Physiol. Part B 155: 145-154.
pdf icon PDF Willis, J.D., W.E. Klingeman, C. Oppert, B.S. Oppert, and J.L. Jurat-Fuentes. 2010. Characterization of cellulolytic activity from digestive fluids of Dissosteira carolina (Orthoptera: Acrididae). Comp. Biochem. Physiol. Part B 157: 267-272.
Article Link Crook, D.J., S. Prabhakar, and B. Oppert. 2009. Protein digestion in larvae of the red oak borer Enaphalodes rufulus. Physiol. Entomol. 34: 152-157.
pdf icon PDF Fabrick, J., C. Oppert, M.D. Lorenzen, K. Morris, B. Oppert, and J.L. Jurat-Fuentes. 2009. A novel Tenebrio molitor cadherin is a functional receptor for Bacillus thuringiensis Cry3Aa toxin. J. Biol. Chem. 284: 18401-18410.
pdf icon PDF Huestis, D.L., B. Oppert, and J.L. Marshall. 2009. Geographic distributions of Idh-1 alleles in a cricket are linked to differential enzyme kinetic performance across thermal environments. BMC Evol. Biol. 9(113), 12 pp.
pdf icon PDF Liu, C., K. Wu, Y. Wu, Y. Gao, C. Ning, and B. Oppert. 2009. Reduction of Bacillus thuringiensis Cry1Ac toxicity against Helicoverpa armigera by a soluble toxin-binding cadherin fragment. J. Insect Physiol. 55: 686-693.
pdf icon PDF Marshall, J.L., D.L. Huestis, Y. Hiromasa, S. Wheeler, C. Oppert, S.A. Marshall, J.M. Tomich, and B. Oppert. 2009. Identification, RNAi knockdown, and functional analysis of an ejaculate protein that mediates a postmating, prezygotic phenotype in a cricket. PloS ONE 4(e7537), 10 pp.
pdf icon PDF Morris, K., M.D. Lorenzen, Y. Hiromasa, J.M. Tomich, C. Oppert, E.N. Elpidina, K.Vinokurov, J.L. Jurat-Fuentes, J. Fabrick, and B. Oppert. 2009. Tribolium castaneum larval gut transcriptome and proteome: a resource for the study of the coleopteran gut. J. Proteome Res. 8: 3889-3898.
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Last Modified: 1/9/2015
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