Wayne Hunter
USDA Agricultural Research Service, Subtropical Insects, Department Member
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We report on the development, evaluation, and efficient delivery of antisense oligonucleotide FANA (2′-deoxy-2′-fluoro-arabinonucleotide) RNA-targeting technology into citrus trees and potato plants for management of bacterial pathogens... more
We report on the development, evaluation, and efficient delivery of antisense oligonucleotide FANA (2′-deoxy-2′-fluoro-arabinonucleotide) RNA-targeting technology into citrus trees and potato plants for management of bacterial pathogens and arthropod pests. The FANA ASO technology is a single nucleotide strand of 20–24 nt in length that incorporates 2′F- chemically modifications of nucleotides, along with a phosphorothioate backbone and modified flanking nucleotides, in their structure called “gapmers,” produced by AUM LifeTech., Inc. These unique modified structures of FANA “triggers” enables gymnotic activity that self-delivers into cells, moving systemically in treated plants and insects, with significant suppression of their RNA targets. Reported is the FANA suppression of two plant-infecting bacterium Candidatus Liberibacter asiaticus, CLas (in citrus trees), and C. Liberibacter solanacearum, CLso (in potato and tomato). The CLas pathogen is associated with huanglongbing (a.k.a...
Research Interests: Entomology, Biotechnology, Biology, Gene Targeting In Prokaryotes, Agricultural Biotechnology, and 15 moreIntegrated Pest Management, Antibacterial agents, Grapevines, Biopesticides, Hemiptera, Citrus, Antibacterial activity, Antisense oligonucleotides, Gene Targeting, Greening, Gene Targeting and Genome Engineering, Antisense Technology, Insect Vectors, Huanglongbing, and Diaphorina citri
The Agricultural Research Service (ARS) is the intramural research agency of the United States Department of Agriculture (USDA) which addresses basic scientific questions and develops applied solutions to a range of agricultural problems,... more
The Agricultural Research Service (ARS) is the intramural research agency of the United States Department of Agriculture (USDA) which addresses basic scientific questions and develops applied solutions to a range of agricultural problems, and in doing so protects national food security and supports international trade. The damage to agricultural commodities inflicted by insects and other arthropod pest species causes a reduction in producer output and profitability, thereby affecting product quality, such that the development of novel and effective arthropod control tactics remains a research challenge at USDA ARS. Additionally, USDA ARS conducts research into arthropod control within urban settings, where damage to dwellings, and ornamental and shade plants are of concern to homeowners and businesses alike. These goals of controlling pests must be balanced with environmental concerns, including the protection of pollinators and other beneficial species. The recent development of RN...
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Detailed annotation and comparative analysis were performed on the Asian citrus psyllid (ACP), Diaphorina citri, vacuolar-type ATP synthase (V-ATPase) to support the biological understanding and development of novel therapeutics to manage... more
Detailed annotation and comparative analysis were performed on the Asian citrus psyllid (ACP), Diaphorina citri, vacuolar-type ATP synthase (V-ATPase) to support the biological understanding and development of novel therapeutics to manage psyllid vectors. D. citri is a hemipteran insect that vectors the causative agent, the bacteria Candidatus Liberibacter asiaticus (CLas), of the citrus greening disease, Huanglongbing (HLB). Millions of citrus trees have been destroyed by citrus greening and every grove in Florida has been directly impacted. In eukaryotic organisms, V-ATPase is an abundant heterodimeric enzyme that serves the cell with essential compartment acidification through the active processes that transport protons across the membrane. Manual curation was completed on 15 putative V-ATPase genes in the D. citri genome. Comparative genomic analysis reveals that the D. citri V-ATPase subunits share domains and motifs with other insects, including the V-ATPase-A superfamily doma...
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The advantages from exogenously applied RNAi biopesticides have yet to be realized in through commercialization due to inconsistent activity of the dsRNA trigger, and the activity level of RNAi suppression. This has prompted research on... more
The advantages from exogenously applied RNAi biopesticides have yet to be realized in through commercialization due to inconsistent activity of the dsRNA trigger, and the activity level of RNAi suppression. This has prompted research on improving delivery methods for applying exogenous dsRNA into plants and insects for the management of pests and pathogens. Another aspect to improve RNAi activity is the incorporation of modified 2′-F pyrimidine nucleotides into the dsRNA trigger. Modified dsRNA incorporating 32–55% of the 2′-F- nucleotides produced improved RNAi activity that increased insect mortality by 12–35% greater than non-modified dsRNA triggers of the same sequence. These results were repeatable across multiple Hemiptera: the Asian citrus psyllid (Diaphorina citri, Liviidae); whitefly (Bemisia tabaci, Aleyroididae); and the glassy-winged sharpshooter (Homalodisca vitripennis, Cicadellidae). Studies using siRNA with modified 2′-F- pyrimidines in mammalian cells show they impr...
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Citrus greening disease is caused by the pathogenCandidatusLiberibacter asiaticus, which is transmitted by the Asian citrus psyllid,Diaphorina citri. There is no curative treatment or significant prevention mechanism for this detrimental... more
Citrus greening disease is caused by the pathogenCandidatusLiberibacter asiaticus, which is transmitted by the Asian citrus psyllid,Diaphorina citri. There is no curative treatment or significant prevention mechanism for this detrimental disease that causes continued economic losses from reduced citrus production. A high quality genome ofD. citriis being manually annotated to provide accurate gene models required to identify novel control targets and increase understanding of this pest. Here, we annotated genes involved in glycolysis, gluconeogenesis, and trehaloneogenesis in theD. citrigenome, as these are core metabolic pathways and suppression could reduce this pest. Specifically, twenty-five genes were identified and annotated in the glycolysis and gluconeogenesis pathways and seven genes for the trehaloneogenesis pathway. Comparative analysis showed that the glycolysis genes inD. citriare highly conserved compared to orthologs in other insect systems, but copy numbers vary inD....
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Insects have a segmented body plan that is established during embryogenesis when the anterior-posterior (A-P) axis is divided into repeated units by a cascade of gene expression. The cascade is initiated by protein gradients created by... more
Insects have a segmented body plan that is established during embryogenesis when the anterior-posterior (A-P) axis is divided into repeated units by a cascade of gene expression. The cascade is initiated by protein gradients created by translation of maternally provided mRNAs, localized at the anterior and posterior poles of the embryo. Particular combinations of these proteins activate specific gap genes to divide the embryo into distinct regions along the A-P axis. Gap genes then activate pair-rule genes, which are usually expressed in part of every other segment. The pair-rule genes, in turn, activate expression of segment polarity genes in a portion of each segment. The segmentation genes are generally conserved among insects, although there is considerable variation in how they are deployed. We annotated 24 segmentation gene homologs in the Asian citrus psyllid, Diaphorina citri. We identified most of the genes that were expected to be present based on known phylogenetic distri...
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Huanglongbing (HLB), also known as citrus greening disease, is caused by the bacterium Candidatus Liberibacter asiaticus (CLas). It is a serious threat to global citrus production. This bacterium is transmitted by the Asian citrus... more
Huanglongbing (HLB), also known as citrus greening disease, is caused by the bacterium Candidatus Liberibacter asiaticus (CLas). It is a serious threat to global citrus production. This bacterium is transmitted by the Asian citrus psyllid, Diaphorina citri (Hemiptera). There are no effective in planta treatments for CLas. Therefore, one strategy is to manage the psyllid population. Manual annotation of the D. citri genome can identify and characterize gene families that could be novel targets for psyllid control. The yellow gene family is an excellent target because yellow genes, which have roles in melanization, are linked to development and immunity. Combined analysis of the genome with RNA-seq datasets, sequence homology, and phylogenetic trees were used to identify and annotate nine yellow genes in the D. citri genome. Manual curation of genes in D. citri provided in-depth analysis of the yellow family among hemipteran insects and provides new targets for molecular control of th...
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The polysaccharide chitin is critical for the formation of many insect structures, including the exoskeleton, and is required for normal development. Here we report the annotation of three genes from the chitin synthesis pathway in the... more
The polysaccharide chitin is critical for the formation of many insect structures, including the exoskeleton, and is required for normal development. Here we report the annotation of three genes from the chitin synthesis pathway in the Asian citrus psyllid, Diaphorina citri (Hemiptera: Liviidae), the vector of Huanglongbing (citrus greening disease). Most insects have two chitin synthase (CHS) genes but, like other hemipterans, D. citri has only one. In contrast, D. citri is unusual among insects in having two UDP-N-acetylglucosamine pyrophosphorylase (UAP) genes. One of the D. citri UAP genes is broadly expressed, while the other is expressed predominantly in males. Our work helps pave the way for potential utilization of these genes as pest control targets to reduce the spread of Huanglongbing.
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Chitin deacetylases (CDAs) are one of the least understood components of insect chitin metabolism. The partial deacetylation of chitin polymers appears to be important for the proper formation of higher order chitin structures, such as... more
Chitin deacetylases (CDAs) are one of the least understood components of insect chitin metabolism. The partial deacetylation of chitin polymers appears to be important for the proper formation of higher order chitin structures, such as long fibers and bundles, that contribute to the integrity of the insect exoskeleton and other structures. Some CDAs may also play a role in bacterial defense. Here we report the characterization of four CDA genes from the Asian citrus psyllid, Diaphorina citri, laying the groundwork for future study of these genes. D. citri is the vector for Candidatus Liberibacter asiaticus (CLas), which is responsible for the global outbreak of Huanglongbing (citrus greening) disease. The manual annotation was done as part of a collaborative community annotation project (https://citrusgreening.org/annotation/index).
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ABSTRACTHuanglongbing (HLB), also known as citrus greening disease, is caused by the bacterium Candidatus Liberibacter asiaticus (CLas) and represents a serious threat to global citrus production. This bacteria is transmitted by the Asian... more
ABSTRACTHuanglongbing (HLB), also known as citrus greening disease, is caused by the bacterium Candidatus Liberibacter asiaticus (CLas) and represents a serious threat to global citrus production. This bacteria is transmitted by the Asian citrus psyllid, Diaphorina citri (Hemiptera) and there are no effective in-planta treatments for CLas. Therefore, one strategy is to manage the psyllid population. Manual annotation of the D. citri genome can identify and characterize gene families that could serve as novel targets for psyllid control. The yellow gene family represents an excellent target as yellow genes are linked to development and immunity due to their roles in melanization. Combined analysis of the genome with RNA-seq datasets, sequence homology, and phylogenetic trees were used to identify and annotate nine yellow genes for the D. citri genome. Phylogenetic analysis shows a unique duplication of yellow-y in D. citri, with life stage specific expression for these two genes. Gen...
Research Interests: Genetics, Biology, Annotation, Genome, Gene, and 3 moreHemiptera, Phylogenetic Tree, and Diaphorina citri
BackgroundDiaphorina citriis a vector of “CandidatusLiberibacter asiaticus” (CLas), the gram-negative bacterial pathogen associated with citrus greening disease. Control measures rely on pesticides with negative impacts on the... more
BackgroundDiaphorina citriis a vector of “CandidatusLiberibacter asiaticus” (CLas), the gram-negative bacterial pathogen associated with citrus greening disease. Control measures rely on pesticides with negative impacts on the environment, natural ecosystems and human and animal health. In contrast, gene-targeting methods have the potential to specifically target the vector species and/or reduce pathogen transmission.ResultsTo improve the genomic resources needed for targeted pest control, we assembled aD. citrigenome based on PacBio long reads followed by proximity ligation-based scaffolding. The 474 Mb genome has 13 chromosomal-length scaffolds. 1,036 genes were manually curated as part of a community annotation project, composed primarily of undergraduate students. We also computationally identified a total of 1,015 putative transcription factors (TFs) and were able to infer motifs for 337 TFs (33 %). In addition, we produced a genome-independent transcriptome and genomes forD. c...
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Phloem and plant sap feeding insects invade the integrity of crops and fruits to retrieve nutrients, in the process damaging food crops. Hemipteran insects account for a number of economically substantial pests of plants that cause damage... more
Phloem and plant sap feeding insects invade the integrity of crops and fruits to retrieve nutrients, in the process damaging food crops. Hemipteran insects account for a number of economically substantial pests of plants that cause damage to crops by feeding on phloem sap. The brown marmorated stink bug (BMSB), Halyomorpha halys (Heteroptera: Pentatomidae) and the Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae) are hemipteran insect pests introduced in North America, where they are an invasive agricultural pest of high-value specialty, row, and staple crops and citrus fruits, as well as a nuisance pest when they aggregate indoors. Insecticide resistance in many species has led to the development of alternate methods of pest management strategies. Double-stranded RNA (dsRNA)-mediated RNA interference (RNAi) is a gene silencing mechanism for functional genomic studies that has potential applications as a tool for the management of insect pests. Exogenously ...
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Citrus production worldwide is currently facing significant losses due to citrus greening disease, also known as Huanglongbing. The citrus greening bacteria, Candidatus Liberibacter asiaticus (CLas), is a persistent propagative pathogen... more
Citrus production worldwide is currently facing significant losses due to citrus greening disease, also known as Huanglongbing. The citrus greening bacteria, Candidatus Liberibacter asiaticus (CLas), is a persistent propagative pathogen transmitted by the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae). Hemipterans characterized to date lack a number of insect immune genes, including those associated with the Imd pathway targeting Gram-negative bacteria. The D. citri draft genome was used to characterize the immune defense genes present in D. citri. Predicted mRNAs identified by screening the published D. citri annotated draft genome were manually searched using a custom database of immune genes from previously annotated insect genomes. Toll and JAK/STAT pathways, general defense genes Dual oxidase, Nitric oxide synthase, prophenoloxidase, and cellular immune defense genes were present in D. citri. In contrast, D. citri lacked genes for the Imd pathway, most an...
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Diaphorina citri, known as the Asian citrus psyllid, is an important pest of citrus because it transmits a phloem-limited bacteria strongly implicated in huanglongbing (citrus greening disease). Emerging biotechnologies, such as RNA... more
Diaphorina citri, known as the Asian citrus psyllid, is an important pest of citrus because it transmits a phloem-limited bacteria strongly implicated in huanglongbing (citrus greening disease). Emerging biotechnologies, such as RNA interference, could provide a new sustainable and environmentally friendly strategy for the management of this pest. In this study, genome and functional analysis were performed to verify whether the RNAi core genes are present in the Asian psyllid genome and if the RNAi machinery could be exploited to develop a management strategy for this pest. Analyses of RNAi-related genes in the Asian citrus psyllid genome showed an absence of sequences encoding R2D2, a dsRNA-binding protein that functions as a cofactor of Dicer-2 in Drosophila. Nevertheless, bioassays using an in Planta System showed that the Asian citrus psyllid was very sensitive to ingested dsRNA, demonstrating a strong RNAi response. A small dose of dsRNA administered through a citrus flush was...
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The Asian citrus psyllid (Diaphorina citri Kuwayama) is the insect vector of the bacterium Candidatus Liberibacter asiaticus (CLas), the pathogen associated with citrus Huanglongbing (HLB, citrus greening). HLB threatens citrus production... more
The Asian citrus psyllid (Diaphorina citri Kuwayama) is the insect vector of the bacterium Candidatus Liberibacter asiaticus (CLas), the pathogen associated with citrus Huanglongbing (HLB, citrus greening). HLB threatens citrus production worldwide. Suppression or reduction of the insect vector using chemical insecticides has been the primary method to inhibit the spread of citrus greening disease. Accurate structural and functional annotation of the Asian citrus psyllid genome, as well as a clear understanding of the interactions between the insect and CLas, are required for development of new molecular-based HLB control methods. A draft assembly of the D. citri genome has been generated and annotated with automated pipelines. However, knowledge transfer from well-curated reference genomes such as that of Drosophila melanogaster to newly sequenced ones is challenging due to the complexity and diversity of insect genomes. To identify and improve gene models as potential targets for ...
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The whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) is among the 100 worst invasive species in the world. As one of the most important crop pests and virus vectors, B. tabaci causes substantial crop losses and poses a serious threat to... more
The whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) is among the 100 worst invasive species in the world. As one of the most important crop pests and virus vectors, B. tabaci causes substantial crop losses and poses a serious threat to global food security. We report the 615-Mb high-quality genome sequence of B. tabaci Middle East-Asia Minor 1 (MEAM1), the first genome sequence in the Aleyrodidae family, which contains 15,664 protein-coding genes. The B. tabaci genome is highly divergent from other sequenced hemipteran genomes, sharing no detectable synteny. A number of known detoxification gene families, including cytochrome P450s and UDP-glucuronosyltransferases, are significantly expanded in B. tabaci. Other expanded gene families, including cathepsins, large clusters of tandemly duplicated B. tabaci-specific genes, and phosphatidylethanolamine-binding proteins (PEBPs), were found to be associated with virus acquisition and transmission and/or insecticide resistance, likely cont...
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Research Interests: Comparative Anatomy, Botany, Microbiology, Entomology, Developmental Biology, and 15 moreBiology, Morphogenesis, Medicine, Plant Science, Multidisciplinary, Plant cell biology, Biological Sciences, Anatomy and Physiology, Animals, Feeding Behavior, Molecular Cell Biology, Hemiptera, Plant Microbiology, Aphididae, and Diaphorina citri
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Short interfering RNAs which can be used to reduce gene expression, or ‘silence’ this expression in a sequence specific manner is call RNA interference, RNAi. In the case of hemipteran pests, RNAi has only recently been shown to disrupt... more
Short interfering RNAs which can be used to reduce gene expression, or ‘silence’ this expression in a sequence specific manner is call RNA interference, RNAi. In the case of hemipteran pests, RNAi has only recently been shown to disrupt their biology. We propose that RNAi has the potential to be applied in an area wide management strategy, thereby suppressing the pest populations to reduce disease spread. Previously we generated leafhopper genetic datasets from three species of known vectors of Xylella fastidiosa (Xf), the plant infecting bacterium which causes Pierce’s disease (PD) of grapevine. Using genomic analyses we identified a subset of potential genetic targets which may be used to suppress these sharpshooter leafhoppers. The primary disease vector, the glassy-winged sharpshooter (GWSS; Homalodisca vitripennis) vectors the Xf xylem-limited bacteria that causes PD in grapevine as well as ‘Scorch-like’ pathogens of other woody agricultural fruit, nut, and ornamental crops. Bu...
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Research Interests: Genetics, Microbiology, Immunology, Molecular Biology, Genomics, and 22 moreMedical Microbiology, Ecology, Climate, RNAi technologyes, RNAi related, RNA interference, Beekeeping, Seasonality, Bees, Apis mellifera, Animals, Florida, Honey bee, Disease Control, Pennsylvania, Colony Collapse Disorder, Population Decline, Honey Bee Research, Large Scale, Food Products, RNA Virus, and single stranded DNA
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Pathogenesis-related group 5 (PR5) plant proteins include thaumatin, osmotin, and related proteins, many of which have antimicrobial activity. The recent discovery of PR5-like (PR5-L) sequences in nematodes and insects raises questions... more
Pathogenesis-related group 5 (PR5) plant proteins include thaumatin, osmotin, and related proteins, many of which have antimicrobial activity. The recent discovery of PR5-like (PR5-L) sequences in nematodes and insects raises questions about their evolutionary relationships. Using complete plant genome data and discovery of multiple insect PR5-L sequences, phylogenetic comparisons among plants and animals were performed. All PR5/PR5-L protein sequences were mined from genome data of a member of each of two main angiosperm groups—the eudicots (Arabidoposis thaliana) and the monocots (Oryza sativa)—and from the Caenorhabditis nematode (C. elegans and C. briggsase). Insect PR5-L sequences were mined from EST databases and GenBank submissions from four insect orders: Coleoptera (Diaprepes abbreviatus and Biphyllus lunatus), Orthoptera (Schistocerca gregaria), Hymenoptera (Lysiphlebus testaceipes), and Hemiptera (Toxoptera citricida). Parsimony and Bayesian phylogenetic analyses showed that the PR5 family is paraphyletic in plants, likely arising from 10 genes in a common ancestor to monocots and eudicots. After evolutionary divergence of monocots and eudicots, PR5 genes increased asymmetrically among the 10 clades. Insects and nematodes contain multiple sequences (seven PR5-Ls in nematodes and at least three in some insects) all related to the same plant clade, with nematode and insect sequences separating as two clades. Protein structural homology modeling showed strong similarity among animal and plant PR5/PR5-Ls, with divergence only in surface-exposed loops. Sequence and structural conservation among PR5/PR5-Ls suggests an important and conserved role throughout the evolutionary divergence of the diverse organisms from which they reside.
Research Interests: Evolutionary Biology, Genetics, Molecular Evolution, Forecasting, Homology Modeling, and 17 moreMolecular, Phylogeny, Sequence alignment, Expressed Sequence Tags, Animals, Antimicrobial activity, Insects, Oryza Sativa, Protein structure, Protein Sequence Analysis, Nematoda, Amino Acid Sequence, Structure activity Relationship, Gene Family, PLANT PROTEINS, Biochemistry and cell biology, and Molecular Sequence Data
Research Interests: Molecular Biology, Plant Biology, Abiotic Stress, Plant Science, Molecular Mechanics, and 14 moreHerbivory, Expression Profiling, Citrus, PLANT DEFENSE, Protein Sequence Analysis, Gene Function, Insect plant interaction, Plant Insect Interactions, Cell Wall, Citrus Sinensis, Salicylic Acid, Host Plant, Aphid, and Jasmonic Acid
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Research Interests: Bioinformatics, Evolutionary Biology, Genetics, Genomics, Computational Biology, and 14 moreSymbiosis, Evolution, Gene expression, Biological Sciences, Expressed Sequence Tags, Animals, Aphids, Genome Annotation, System Development, Model System, Heat Shock, Gene Expression Regulation, Gene expression profiling, and Aphid
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Research Interests: Bioinformatics, Genetics, Entomology, Molecular Biology, Genomics, and 30 moreComputational Biology, Virology, Agricultural Entomology, Biological Control, RNA viruses, Biological Sciences, Insect Viruses, Phylogeny, IRES, Animals, Planthoppers, Leafhoppers, Hemiptera, Genome Organization, Molecular Characterization, Insect, Protein Conformation, Genome sequence, Amino Acid Sequence, Base Sequence, Open Reading Frame, In Silico, RNA Dependent RNA Polymerase, Virus Vector Relationships, RNA Virus, Viral Genomics, Internal ribosome entry site, Structural model, single stranded DNA, and Molecular Sequence Data
Research Interests: Genetics, Real-time RT-PCR, Potato, Expressed Sequence Tags, PPI, and 15 moreFruit, Gene, Pi, Citrus, Fruit set and development, Mechanical Stress, S100 protein family, Open Reading Frame, PLANT PROTEINS, Trypsin Inhibitor, cDNA library, Gene expression profiling, Plant Leaves, Cysteine Proteinase Inhibitors, and Molecular Sequence Data
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Research Interests: Bioinformatics, Entomology, Electron Microscopy, Molecular Biology, Computational Biology, and 28 moreVirology, Agriculture, Biological Control, Hymenoptera, Biological Sciences, Insect Viruses, Ants, Sequence alignment, Female, Animals, Florida, Male, Impact of Agricultulral Cooperative Societies on Farmers Productivity, Fire Ants, Solenopsis, Cysteine endopeptidases, Insect Virology and Pathology, Seasons, Genome sequence, Amino Acid Sequence, Virus infection, Open Reading Frame, RNA Dependent RNA Polymerase, RNA Virus, Nucleotides, Red Fire Ants, Electron Microscope, and Molecular Sequence Data
The botanical product RD-Repelin® was highly repellent to pea aphids at concentrations of 1%, 4% or 10%. Repellency occurred prior to leaf contact by aphids at all three concentrations. RD-Repelin® delayed symptom expression of zucchini... more
The botanical product RD-Repelin® was highly repellent to pea aphids at concentrations of 1%, 4% or 10%. Repellency occurred prior to leaf contact by aphids at all three concentrations. RD-Repelin® delayed symptom expression of zucchini yellow mosaic virus (ZYMV) in 81% of plants treated with 1% concentration, although virus transmission was not prevented. The effects of RD-Repelin® on aphid settling behaviour, symptom expression and potential for pest management are discussed.
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Homalodisca vitripennis Germar 1821 (Hemiptera: Cicadellidae) [Takiya et al. (2006) Ann Entomol Soc Am 99:648–655; syn. H. coagulata (Say)] salivary gland and gut EST libraries were used to isolate cDNA fragments of the gene transcripts... more
Homalodisca vitripennis Germar 1821 (Hemiptera: Cicadellidae) [Takiya et al. (2006) Ann Entomol Soc Am 99:648–655; syn. H. coagulata (Say)] salivary gland and gut EST libraries were used to isolate cDNA fragments of the gene transcripts encoding for cathepsin L, asparaginyl endopeptidase, cathepsin B, metalloendopeptidase, cathepsin D, multicatalytic endopeptidase, and a sugar-binding C-type lectin. Transcript levels were evaluated in immature and adult H. vitripennis feeding on sunflower (Helianthus annuus) or cowpea (Vigna unguiculata). Northern blot hybridization results showed that expression of most of the transcripts were similar for all developmental stages and feeding on the two diets examined. However, the expression of the transcript for asparaginyl endopeptidase was less expressed in sunflower-fed adult females compared to sunflower-fed immatures. Also, the expression of the C-type lectin transcript was up-regulated in adults compared to immatures when fed on either diet. Documenting both the presence and variation of transcript expression involved in putative digestive proteolysis in this xylem-feeding leafhopper is noteworthy and aids efforts to design specific diet formulations for mass production of hosts and parasitoids to be used as effective biological control measures. Arch. Insect Biochem. Physiol. 66:76–88, 2007. Published 2007 Wiley-Liss, Inc.