The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Colin S Brent - One of the best experts on this subject based on the ideXlab platform.
-
diapause termination and postdiapause in Lygus Hesperus heteroptera miridae
Journal of Insect Science, 2021Co-Authors: Colin S BrentAbstract:The western tarnished plant bug, Lygus Hesperus Knight, overwinters as a diapausing adult in response to short day lengths. Once environmental conditions are favorable, the bugs revert to an active reproductive state. To determine the impact on life-history traits of diverting resources toward diapause rather than oogenesis during early adulthood, diapausing and nondiapausing L. Hesperus females were reared from the same cohorts. Body mass, ovarian maturation, ovipositional activity, and survivorship were monitored starting either at the time of release from diapause-inducing conditions or at adult eclosion for diapausers and nondiapausers, respectively. Females that had gone through 2 wk of diapause were larger and able to mobilize the resources necessary for oogenesis faster than nondiapausers, initiating oogenesis and ovipositing sooner and at a faster initial rate. However, lifetime egg production and average daily rates were similar for both groups. Postdiapausers lived longer than nondiapausers by an average of 19 d, which is five more than the 2-wk period when they were reproductively senescent. Overall, the results indicate that short-term diapause does not have a negative impact on life history. Furthermore, the extra endogenous resources stored during diapause may be able to enhance the alacrity with which the female can take advantage of improved environmental conditions and may prolong life by shielding the females against environmental stressors such as temperature extremes, oxidative agents, or food deficits.
-
trpa1 modulates noxious odor responses in Lygus Hesperus
Journal of Insect Physiology, 2020Co-Authors: Joe J Hull, Yuwen Yang, Katelyn Miyasaki, Colin S BrentAbstract:Lygus Hesperus isa key pest of many economically important crops across western North America. Central to many aspects of the lives of these insects is chemical signalling, with identified roles in host plant selection, aggregation and passive mate guarding. The development of novel monitoring and control approaches for this insect will rely on a sound understanding of how these cues are perceived and processed, and their impact on behavior. Towards this end, we investigated allyl isothiocyanate, cinnamaldehyde and citronellal, compounds that are noxious repellents to other insects. We found that L. Hesperus avoided areas containing the three compounds and that exposure induced increases in movement velocity and duration in both nymphs and adults. This suggests these compounds may work as repellents. To better understand the underlying physiology of this response, RNA interference by dsRNA injection was used to inhibit the expression of two chemosensory-associated proteins, the odorant receptor co-receptor (Orco) and the transient receptor potential A (TRPA1) channel. While knockdown of Orco did not change the reaction of adult females to citronellal, TRPA1 silencing effectively eliminated the induced increase to movement, suggesting a chemoperceptory role in citronellal detection.
-
reproductive development of Lygus Hesperus hemiptera miridae adults under constant and variable temperatures
Journal of Insect Science, 2019Co-Authors: Colin S Brent, D W SpurgeonAbstract:As water for agriculture becomes less available in the semi-arid western United States, alternative irrigation strategies such as deficit irrigation may be necessary for continued crop production. Alternative irrigation practices in cotton (Gossypium spp. [Malvales: Valvaceae]) can result in episodic drought stress that alters temperature profiles within the crop canopy. These altered temperatures may influence populations of important pests such as Lygus Hesperus Knight. Field studies often associate lower population densities of L. Hesperus with limited irrigation. Recent studies of the thermal ecology of L. Hesperus egg and nymphal development have demonstrated only subtle effects of the high, variable temperatures typical of moderate drought stress in cotton. However, influences of these conditions on L. Hesperus adult reproductive development have not been studied. The reproductive development of L. Hesperus adults was examined under constant (±0.2°C) and variable (±8°C) regimes at a low (15°C), moderate (22°C), and high (29°C) daily mean temperatures. No developmental differences were demonstrated between temperature regimes under moderate or high temperatures. At the low temperature, only the times to the occurrence of eggs, filled medial accessory glands, and filling seminal vesicles were shorter under variable regime, compared with the constant temperature. These results suggest that temporary, episodic increases in crop canopy temperatures caused by moderate drought stress are unlikely to impact L. Hesperus population growth, and may only promote short-term displacement of adults into adjacent crops with preferable conditions.
-
rna interference mediated knockdown of eye coloration genes in the western tarnished plant bug Lygus Hesperus knight
Archives of Insect Biochemistry and Physiology, 2019Co-Authors: Colin S Brent, Joe J HullAbstract:Insect eye coloration arises from the accumulation of various pigments. A number of genes that function in the biosynthesis (vermilion, cinnabar, and cardinal) and importation (karmoisin, white, scarlet, and brown) of these pigments, and their precursors, have been identified in diverse species and used as markers for transgenesis and gene editing. To examine their suitability as visible markers in Lygus Hesperus Knight (western tarnished plant bug), transcriptomic data were screened for sequences exhibiting homology with the Drosophila melanogaster proteins. Complete open reading frames encoding putative homologs for all seven genes were identified. Bioinformatic-based sequence and phylogenetic analyses supported initial annotations as eye coloration genes. Consistent with their proposed role, each of the genes was expressed in adult heads as well as throughout nymphal and adult development. Adult eyes of those injected with double-stranded RNAs (dsRNAs) for karmoisin, vermilion, cinnabar, cardinal, and scarlet were characterized by a red band along the medial margin extending from the rostral terminus to the antenna. In contrast, eyes of insects injected with dsRNAs for both white and brown were a uniform light brown. White knockdown also produced cuticular and behavioral defects. Based on its expression profile and robust visible phenotype, cardinal would likely prove to be the most suitable marker for developing gene editing methods in Lygus species.
-
development and survival of Lygus Hesperus hemiptera miridae nymphs under constant and variable temperatures
Journal of Insect Science, 2019Co-Authors: D W Spurgeon, Colin S BrentAbstract:Thermal environments of the arid western United States are often harsh compared with the ranges of temperatures favorable for development and survival of crop insect pests. In cotton (Gossypium spp., [Malvales: Malvaceae]), new irrigation practices such as deficit irrigation may impact populations of pest and beneficial arthropods by temporarily altering temperature profiles within the plant canopy. Most information regarding the temperature-dependent development and survival of an important cotton pest, the western tarnished plant bug (Lygus Hesperus Knight [Hemiptera: Miridae]), is derived from constant temperature studies. We examined the development and survival of L. Hesperus nymphs under constant (+/- 0.2 degrees C) and variable (+/- 8 degrees C) temperature regimes at daily mean temperatures of 15, 22, and 29 degrees C. Under the low temperature (15 degrees C), stadium lengths and duration of the entire nymphal stage were shorter when temperatures were variable compared with a constant temperature. No differences in development times were observed between regimes at the medium temperature (22 degrees C). Except for the 1st stadium, development times under the high variable temperature regime were longer compared with the high constant regime (29 degrees C). Nymph survival was unaffected by temperature regime except at the lowest temperature, where daily thermal fluctuations substantially improved survival compared with the constant conditions. These results suggest that temporarily increased crop canopy temperatures caused by altered irrigation schemes are unlikely to substantially reduce the growth of L. Hesperus populations. However, enhanced nymphal development and survival under low variable temperatures likely contribute to the survival of overwintering L. Hesperus in the absence of acute, low-temperature mortality.
Joe J Hull - One of the best experts on this subject based on the ideXlab platform.
-
trpa1 modulates noxious odor responses in Lygus Hesperus
Journal of Insect Physiology, 2020Co-Authors: Joe J Hull, Yuwen Yang, Katelyn Miyasaki, Colin S BrentAbstract:Lygus Hesperus isa key pest of many economically important crops across western North America. Central to many aspects of the lives of these insects is chemical signalling, with identified roles in host plant selection, aggregation and passive mate guarding. The development of novel monitoring and control approaches for this insect will rely on a sound understanding of how these cues are perceived and processed, and their impact on behavior. Towards this end, we investigated allyl isothiocyanate, cinnamaldehyde and citronellal, compounds that are noxious repellents to other insects. We found that L. Hesperus avoided areas containing the three compounds and that exposure induced increases in movement velocity and duration in both nymphs and adults. This suggests these compounds may work as repellents. To better understand the underlying physiology of this response, RNA interference by dsRNA injection was used to inhibit the expression of two chemosensory-associated proteins, the odorant receptor co-receptor (Orco) and the transient receptor potential A (TRPA1) channel. While knockdown of Orco did not change the reaction of adult females to citronellal, TRPA1 silencing effectively eliminated the induced increase to movement, suggesting a chemoperceptory role in citronellal detection.
-
rna interference mediated knockdown of eye coloration genes in the western tarnished plant bug Lygus Hesperus knight
Archives of Insect Biochemistry and Physiology, 2019Co-Authors: Colin S Brent, Joe J HullAbstract:Insect eye coloration arises from the accumulation of various pigments. A number of genes that function in the biosynthesis (vermilion, cinnabar, and cardinal) and importation (karmoisin, white, scarlet, and brown) of these pigments, and their precursors, have been identified in diverse species and used as markers for transgenesis and gene editing. To examine their suitability as visible markers in Lygus Hesperus Knight (western tarnished plant bug), transcriptomic data were screened for sequences exhibiting homology with the Drosophila melanogaster proteins. Complete open reading frames encoding putative homologs for all seven genes were identified. Bioinformatic-based sequence and phylogenetic analyses supported initial annotations as eye coloration genes. Consistent with their proposed role, each of the genes was expressed in adult heads as well as throughout nymphal and adult development. Adult eyes of those injected with double-stranded RNAs (dsRNAs) for karmoisin, vermilion, cinnabar, cardinal, and scarlet were characterized by a red band along the medial margin extending from the rostral terminus to the antenna. In contrast, eyes of insects injected with dsRNAs for both white and brown were a uniform light brown. White knockdown also produced cuticular and behavioral defects. Based on its expression profile and robust visible phenotype, cardinal would likely prove to be the most suitable marker for developing gene editing methods in Lygus species.
-
prediction of a peptidome for the western tarnished plant bug Lygus Hesperus
General and Comparative Endocrinology, 2017Co-Authors: Andrew E Christie, Joe J Hull, Scott M Geib, Josh A Richer, Erica E TassoneAbstract:Many strategies for controlling insect pests require an understanding of their hormonal signaling agents, peptides being the largest and most diverse single class of these molecules. Lygus Hesperus is a pest species of particular concern, as it is responsible for significant damage to a wide variety of commercially important plant crops. At present, little is known about the peptide hormones of L. Hesperus. Here, transcriptomic data were used to predict a peptidome for L. Hesperus. Fifty-three L. Hesperus transcripts encoding peptide precursors were identified, with a subset amplified by PCR for sequence verification. The proteins deduced from these transcripts allowed for the prediction of a 119-sequence peptidome for L. Hesperus. The predicted peptides include isoforms of allatostatin A, allatostatin B (AST-B), allatostatin C, allatotropin, bursicon, CCHamide, corazonin, crustacean cardioactive peptide, crustacean hyperglycemic hormone/ion transport peptide, diuretic hormone 31, GSEFLamide, insulin-like peptide, myosuppressin, neuroparsin, neuropeptide F, orcokinin, orcomyotropin, pyrokinin, short neuropeptide F, SIFamide, sulfakinin and tachykinin-related peptide. Of note were several isoforms of AST-B that possess -WX7Wamide carboxyl-termini rather than the stereotypical -WX6Wamide (e.g., KWQDMQNPGWamide), an allatotropin ending in -SARGFamide rather than -TARGFamide (GLKNGPLNSARGFamide), a GSEFLamide ending in -GTEFLamide (TVGTEFLamide), several orcokinins with PMDEIDR- rather than NFDEIDR- amino-termini (e.g., PMDEIDRAGFTHFV), and an eight rather than 12 amino acid long isoform of SIFamide (PPFNGSIFamide). Collectively, the L. Hesperus peptidome predicted here provides a resource for initiating physiological investigations of peptidergic signaling in this species, including studies directed at the biological control of this agricultural pest.
-
de novo construction of an expanded transcriptome assembly for the western tarnished plant bug Lygus Hesperus
GigaScience, 2016Co-Authors: Erica E Tassone, Jeffrey A Fabrick, Scott M Geib, Brian Hall, Colin S Brent, Joe J HullAbstract:Background The plant bug Lygus Hesperus Knight is a polyphagous pest of many economically important crops. Despite its pest status, little is known about the molecular mechanisms responsible for much of the biology of this species. Earlier Lygus transcriptome assemblies were limited by low read depth, or because they focused on specific conditions. To generate a more comprehensive transcriptome, we supplemented previous datasets with new reads corresponding to specific tissues (heads, antennae, and male reproductive tissues). This transcriptome augments current Lygus molecular resources and provides the foundational knowledge critical for future comparative studies.
-
molecular cloning and characterization of g alpha proteins from the western tarnished plant bug Lygus Hesperus
Insects, 2014Co-Authors: Joe J Hull, Mei-xian WangAbstract:The Gα subunits of heterotrimeric G proteins play critical roles in the activation of diverse signal transduction cascades. However, the role of these genes in chemosensation remains to be fully elucidated. To initiate a comprehensive survey of signal transduction genes, we used homology-based cloning methods and transcriptome data mining to identity Gα subunits in the western tarnished plant bug (Lygus Hesperus Knight). Among the nine sequences identified were single variants of the Gαi, Gαo, Gαs, and Gα12 subfamilies and five alternative splice variants of the Gαq subfamily. Sequence alignment and phylogenetic analyses of the putative L. Hesperus Gα subunits support initial classifications and are consistent with established evolutionary relationships. End-point PCR-based profiling of the transcripts indicated head specific expression for LhGαq4, and largely ubiquitous expression, albeit at varying levels, for the other LhGα transcripts. All subfamilies were amplified from L. Hesperus chemosensory tissues, suggesting potential roles in olfaction and/or gustation. Immunohistochemical staining of cultured insect cells transiently expressing recombinant His-tagged LhGαi, LhGαs, and LhGαq1 revealed plasma membrane targeting, suggesting the respective sequences encode functional G protein subunits.
Jeffrey A Fabrick - One of the best experts on this subject based on the ideXlab platform.
-
insecticidal activity of marigold tagetes patula plants and foliar extracts against the hemipteran pests Lygus Hesperus and bemisia tabaci
PLOS ONE, 2020Co-Authors: Jeffrey A Fabrick, Andrea J Yool, Dale W SpurgeonAbstract:The western tarnished plant bug, Lygus Hesperus Knight (Hemiptera: Miridae) and the whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) are key hemipteran pests of numerous crop plants throughout the western United States and Mexico. Management in the U.S. currently relies on only a few insecticides and is threatened by the evolution of resistance. New chemistries or alternative management strategies are needed to reduce selection pressure on current insecticides and enhance control. Here, we investigated the bio-insecticidal toxicity of the French marigold, Tagetes patula Linnaeus (Asterales: Asteraceae), against both L. Hesperus and B. tabaci. Assays indicated significantly reduced survival of both pest species on T. patula plants, and in diet incorporation assays containing aqueous and methanolic marigold foliar extracts. Mortality was concentration-dependent, indicating the presence of one or more extractable toxicants. These data suggest that T. patula plants have insecticidal constituents that might be identified and developed as novel alternatives to conventional chemical treatments.
-
de novo construction of an expanded transcriptome assembly for the western tarnished plant bug Lygus Hesperus
GigaScience, 2016Co-Authors: Erica E Tassone, Jeffrey A Fabrick, Scott M Geib, Brian Hall, Colin S Brent, Joe J HullAbstract:Background The plant bug Lygus Hesperus Knight is a polyphagous pest of many economically important crops. Despite its pest status, little is known about the molecular mechanisms responsible for much of the biology of this species. Earlier Lygus transcriptome assemblies were limited by low read depth, or because they focused on specific conditions. To generate a more comprehensive transcriptome, we supplemented previous datasets with new reads corresponding to specific tissues (heads, antennae, and male reproductive tissues). This transcriptome augments current Lygus molecular resources and provides the foundational knowledge critical for future comparative studies.
-
transcriptome based identification of abc transporters in the western tarnished plant bug Lygus Hesperus
PLOS ONE, 2014Co-Authors: Joe J Hull, Jeffrey A Fabrick, Scott M Geib, Colin S Brent, Douglas B Walsh, Kendrick H Chaney, Laura Corley LavineAbstract:ATP-binding cassette (ABC) transporters are a large superfamily of proteins that mediate diverse physiological functions by coupling ATP hydrolysis with substrate transport across lipid membranes. In insects, these proteins play roles in metabolism, development, eye pigmentation, and xenobiotic clearance. While ABC transporters have been extensively studied in vertebrates, less is known concerning this superfamily in insects, particularly hemipteran pests. We used RNA-Seq transcriptome sequencing to identify 65 putative ABC transporter sequences (including 36 full-length sequences) from the eight ABC subfamilies in the western tarnished plant bug (Lygus Hesperus), a polyphagous agricultural pest. Phylogenetic analyses revealed clear orthologous relationships with ABC transporters linked to insecticide/xenobiotic clearance and indicated lineage specific expansion of the L. Hesperus ABCG and ABCH subfamilies. The transcriptional profile of 13 LhABCs representative of the ABCA, ABCB, ABCC, ABCG, and ABCH subfamilies was examined across L. Hesperus development and within sex-specific adult tissues. All of the transcripts were amplified from both reproductively immature and mature adults and all but LhABCA8 were expressed to some degree in eggs. Expression of LhABCA8 was spatially localized to the testis and temporally timed with male reproductive development, suggesting a potential role in sexual maturation and/or spermatozoa protection. Elevated expression of LhABCC5 in Malpighian tubules suggests a possible role in xenobiotic clearance. Our results provide the first transcriptome-wide analysis of ABC transporters in an agriculturally important hemipteran pest and, because ABC transporters are known to be important mediators of insecticidal resistance, will provide the basis for future biochemical and toxicological studies on the role of this protein family in insecticide resistance in Lygus species.
-
molecular and functional characterization of multiple aquaporin water channel proteins from the western tarnished plant bug Lygus Hesperus
Insect Biochemistry and Molecular Biology, 2014Co-Authors: Jeffrey A Fabrick, Joe J Hull, Jinxin V Pei, Andrea J YoolAbstract:Aquaporins (AQPs) are integral membrane channel proteins that facilitate the bidirectional transfer of water or other small solutes across biological membranes involved in numerous essential physiological processes. In arthropods, AQPs belong to several subfamilies, which contribute to osmoregulation, respiration, cryoprotection, anhydrobiosis, and excretion. We cloned and characterized five novel AQPs from the western tarnished plant bug, Lygus Hesperus, a polyphagous insect pest of food and fiber crops throughout western North America. The L. Hesperus AQPs (LhAQP1-5) belong to different phylogenetic subfamilies, have unique transcription profiles and cellular localizations, and all transport water (but not glycerol) when heterologously expressed in Xenopus laevis oocytes. Our results demonstrate that multiple AQPs with possible compensatory functions are produced in L. Hesperus that likely play important roles in maintaining water homeostasis in this important insect pest.
-
sequencing and de novo assembly of the western tarnished plant bug Lygus Hesperus transcriptome
PLOS ONE, 2013Co-Authors: Joe J Hull, Jeffrey A Fabrick, Scott M Geib, Colin S BrentAbstract:Background: Mirid plant bugs (Hemiptera: Miridae) are economically important insect pests of many crops worldwide. The western tarnished plant bug Lygus Hesperus Knight is a pest of cotton, alfalfa, fruit and vegetable crops, and potentially of several emerging biofuel and natural product feedstocks in the western US. However, little is known about the underlying molecular genetics, biochemistry, or physiology of L. Hesperus, including their ability to survive extreme environmental conditions. Methodology/Principal Findings: We used 454 pyrosequencing of a normalized adult cDNA library and de novo assembly to obtain an adult L. Hesperus transcriptome consisting of 1,429,818 transcriptomic reads representing 36,131 transcript isoforms (isotigs) that correspond to 19,742 genes. A search of the transcriptome against deposited L. Hesperus protein sequences revealed that 86 out of 87 were represented. Comparison with the non-redundant database indicated that 54% of the transcriptome exhibited similarity (e-value #1 25 ) with known proteins. In addition, Gene Ontology (GO) terms, Kyoto Encyclopedia of Genes and Genomes (KEGG) annotations, and potential Pfam domains were assigned to each transcript isoform. To gain insight into the molecular basis of the L. Hesperus thermal stress response we used transcriptomic sequences to identify 52 potential heat shock protein (Hsp) homologs. A subset of these transcripts was sequence verified and their expression response to thermal stress monitored by semi-quantitative PCR. Potential homologs of Hsp70, Hsp40, and 2 small Hsps were found to be upregulated in the heat-challenged adults, suggesting a role in thermotolerance. Conclusions/Significance: The L. Hesperus transcriptome advances the underlying molecular understanding of this arthropod pest by significantly increasing the number of known genes, and provides the basis for further exploration and understanding of the fundamental mechanisms of abiotic stress responses.
William A. Brindley - One of the best experts on this subject based on the ideXlab platform.
-
structure of populations of Lygus Hesperus hemiptera miridae with multiple resistance mechanisms to trichlorfon
Journal of Economic Entomology, 1993Co-Authors: William A. BrindleyAbstract:Five populations of Lygus Hesperus Knight collected from alfalfa fields in Utah and Idaho were exposed to a range of concentrations of trichlorfon in a contact bioassay using plastic, self-closing bags. Various degrees of resistance were noticed. Esterase activity and acetylcholinesterase (AChE) insensitivity were assayed in 160 individuals from each population. Esterase activity of the most resistant population from Idaho was more than four times that of the susceptible Utah population, and AChE of the most resistant population was only one-third as sensitive to 10-7 M paraoxon. We detected a linear correlation between esterase activity and AChE insensitivity levels with the logarithm of the LC50s. Population structures were discerned from distribution patterns of esterase activities and AChE insensitivities, as well as from slopes of the responses. The susceptible population was very homogeneous and the resistant populations were more heterogeneous. Interactions between the multiple resistance mechanisms are discussed.
-
molecular properties of acetylcholinesterase purified from Lygus Hesperus knight hemiptera miridae
Insect Biochemistry and Molecular Biology, 1992Co-Authors: Kun Yan Zhu, William A. BrindleyAbstract:Abstract Molecular properties of acetylcholinesterase (AChE, EC 3.1.1.7) purified from Lygus Hesperus Knight were characterized by sucrose gradient centrifugation, non-denaturing, denaturing, and two-dimensional polyacrylamide gel electrophoresis, isoelectric focusing, and inhibition by paraoxon. AChE was found to be a globular enzyme with three distinct molecular forms. The major form, accounting for about 89% of total AChE activity, was a hydrophilic form (b) with a sedimentation coefficient of 7.3 S. Two other minor forms, which were recovered in either non-denaturing or denaturing gel electrophoresis but not in the centrifugation, were hydrophilic (a) and amphiphilic (c) forms, accounting for about 4 and 7% of total AChE activity, respectively. The molecular weights for the native and reduced protein were 199,000 and 94,000 for the hydrophilic a form, 150,000 and 79,000 for the hydrophilic b form, and 82,000 and 86,000 for the amphiphilic form, indicating that the molecular forms a and b were dimers while c was a monomer. All three molecular forms appeared to have very similar isoelectric points (7.4), and responded similarly to inhibition by paraoxon. These similarities may indicate structural similarity among these molecular forms of AChE.
-
enzymological and inhibitory properties of acetylcholinesterase purified from Lygus Hesperus knight hemiptera miridae
Insect Biochemistry and Molecular Biology, 1992Co-Authors: Kun Yan Zhu, William A. BrindleyAbstract:We studied the enzymological and inhibitory properties of a 600-fold purified acetylcholinesterase (AChE, EC 3.1.1.7) from Lygus Hesperus Knight. The optimal pH and temperature were 7.5–8.0 and 35–40°C, respectively, for hydrolyzing selected substrates. Km and Vmax were 6.9 × 10−5 M and 42.9 units/mg for acetylthiocholine (ATC), 6.5 × 10−5 M and 32.8 units/mg for acetyl-(β-methyl) thiocholine (AβMTC), 7.2 × 10−5 M and 21.9 units/mg for propionylthiocholine (PTC), and 3.3 × 10−3 M and 4.2 units/mg for S-butyrylthiocholine (BTC), at 37°C and pH 7.7. The efficiency for hydrolyzing different substrates was ATC > AβMTC > PTC > BTC. Enzyme activity was inhibited by 10−7 M eserine or BW284C51, but not by ethopropazine. The enzyme's inhibitor and substrate specificities, and substrate (ATC) inhibition confirmed that it was an AChE. Bimolecular reaction constants were 9.44 × 105 M−1 min−1 for paraoxon, 2.21 × 105 M−1 min−1 for dichlorvos, 8.28 × 106 M−1 min−1 for naled, 2.15 × 104 M−1 min−1 for oxydemeton-methyl, 4.18 × 104 M−1 min− for demeton-S-methyl, for 2.98 × 105 M−1 min−1 for mevinphos, at 25°C. The inhibitory potency for all six organophosphorus compounds was mainly determined by the affinity between the organophosphates and AChE. Eserine and carbofuran were competitive inhibitors for the active sites of AChE. The competitive inhibition constant was 1.20 × 10−8 M for eserine and 1.24 × 10−8 M for carbofuran.
-
Significance of carboxylesterases and insensitive acetylcholinesterase in conferring organophosphate resistance in Lygus Hesperus populations
Pesticide Biochemistry and Physiology, 1992Co-Authors: Kun Yan Zhu, William A. BrindleyAbstract:Abstract We used four organophosphorus compounds (paraoxon, dichlorvos, naled, and oxydemeton-methyl) to study the inhibition of acetylcholinesterase purified from five field populations (Caldwell, Kuna, Roswell, and Star in Idaho and Logan in Utah) of Lygus Hesperus Knight. The sensitivity of acetylcholinesterase to the four organophosphorus compounds in different insect locations was Logan > Roswell > Caldwell > Kuna > Star, and the insensitivity spectrum of acetylcholinesterase to different organophosphorus compounds was rather broad. A good correlation between the specific activity of carboxylesterases and trichlorfon LC 50 among the five populations of L. Hesperus suggested that trichlorfon resistance was mainly established by carboxylesterase activity. Preincubation of paraoxon, dichlorvos, or oxydemeton-methyl with carboxylesterase (197.5 units/mg protein) from the Roswell insects reduced the inhibitory potency of these compounds by 81, 51, and 22%, respectively, while preincubation with carboxylesterases (44.7 units/mg protein) from the Logan insects reduced the inhibitory potency of these compounds by 33, 39, and 4%, respectively. Carboxylesterases in L. Hesperus were fairly specific to certain organophosphorus compounds. It could reduce paraoxon more efficiently than oxydemeton-methyl.
-
isolation and partial purification of acetylcholinesterase from Lygus Hesperus hemiptera miridae
Journal of Economic Entomology, 1991Co-Authors: Kun Yan Zhu, William A. Brindley, T H HsiaoAbstract:Acetylcholinesterase (AChE) from Lygus Hesperus Knight was isolated and partially purified by Triton X-100 extraction, ammonium sulfate precipitation, gel filtration, and affinity chromatography. The degree of the purification was about l,400-fold and the yield was about 3.3%. Purification was primarily the result of affinity chromatography, and the low recovery was due to sequential loss of AChE in each step during purification. The solubility of AChE can be greatly enhanced by addition of Triton X-100 but not by high ionic strength, suggesting that L. Hesperus contains little or no asymmetric forms of AChE. The procedure is evaluated, and the possibility of increasing the yield is also discussed.
Dale W Spurgeon - One of the best experts on this subject based on the ideXlab platform.
-
insecticidal activity of marigold tagetes patula plants and foliar extracts against the hemipteran pests Lygus Hesperus and bemisia tabaci
PLOS ONE, 2020Co-Authors: Jeffrey A Fabrick, Andrea J Yool, Dale W SpurgeonAbstract:The western tarnished plant bug, Lygus Hesperus Knight (Hemiptera: Miridae) and the whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) are key hemipteran pests of numerous crop plants throughout the western United States and Mexico. Management in the U.S. currently relies on only a few insecticides and is threatened by the evolution of resistance. New chemistries or alternative management strategies are needed to reduce selection pressure on current insecticides and enhance control. Here, we investigated the bio-insecticidal toxicity of the French marigold, Tagetes patula Linnaeus (Asterales: Asteraceae), against both L. Hesperus and B. tabaci. Assays indicated significantly reduced survival of both pest species on T. patula plants, and in diet incorporation assays containing aqueous and methanolic marigold foliar extracts. Mortality was concentration-dependent, indicating the presence of one or more extractable toxicants. These data suggest that T. patula plants have insecticidal constituents that might be identified and developed as novel alternatives to conventional chemical treatments.
-
Diapause Response to Photoperiod in an Arizona Population of Lygus Hesperus (Hemiptera: Miridae)
Journal of Entomological Science, 2015Co-Authors: Dale W Spurgeon, Colin S BrentAbstract:Abstract The western tarnished plant bug (Lygus Hesperus Knight) is an important crop pest in the western United States that overwinters in an adult diapause. However, knowledge of L. Hesperus diapause is incomplete. Eggs from field-collected adults were reared under photoperiods of 10:14, 11:13, 12:12, and 13:11 (L:D) h at 26.7 ± 1°C, and the diapause response for each gender was modeled by a logistic function. Incidence of a recently reported “glass bead” fat body type also was examined. Validation studies using the same methods were subsequently conducted using photoperiods of 10.5:13.5, 11.5:12.5, and 12.5:11.5 (L:D) h. No effects of bug gender, photoperiod, or diapause status on occurrence of the novel fat type were detected. Estimates of diapause in validation studies were within confidence intervals for initial predictions, but systematic deviations from initial predictions prompted refitting of the models to include validation data. Refitted functions estimated critical photoperiods of 11h44min fo...
-
temperature dependent egg development of Lygus Hesperus hemiptera miridae
Journal of Economic Entomology, 2013Co-Authors: Rodney W Cooper, Dale W SpurgeonAbstract:Lygus Hesperus Knight (Hemiptera: Miridae) is a key agricultural pest in the western United States, but certain aspects of its temperature-dependent development are poorly defined. Accurate models describing the relationships between temperature and development of L. Hesperus would facilitate the study of Lygus seasonal population dynamics and overwintering ecology. We used nonlinear biophysical models to describe the development of L. Hesperus eggs oviposited in green bean pods and semitransparent agarose and held under constant temperatures from 10 to 37.8°C. The agarose substrate was used because it is less susceptible than green beans to deterioration at low and high temperature extremes, and because it allowed the observation of phases of embryonic development that are hidden from view from eggs developing in plant material. The models indicated that both low and high temperature inhibited development of each observed embryonic phase regardless of oviposition substrate. Developmental rates asymptotically approached zero with decreasing temperature in the lower thermal range, and decreased with increasing temperatures above 32.2°C. Eggs oviposited in agarose developed slower than eggs oviposited in green bean pods suggesting that egg developmental rates were influenced by the type of host substrate. Our temperature-dependent developmental rate models for L. Hesperus eggs supplement nonlinear models recently reported for L. Hesperus nymphal and adult reproductive development and should be useful in planning and interpreting field studies of L. Hesperus population dynamics and overwintering ecology.
-
temperature dependent reproductive development of Lygus Hesperus hemiptera miridae
Environmental Entomology, 2012Co-Authors: Dale W Spurgeon, W R CooperAbstract:ABSTRACT Recent studies to elucidate relationships between the western tarnished plant bug, Lygus Hesperus Knight, and injury to cotton (Gossypium spp.) have identified important differences in feeding behaviors among adults of different gender and reproductive states. These findings suggest a need for improved knowledge of L. Hesperus temperature-dependent reproductive development. We used nonlinear biophysical development rate models to describe the reproductive development of adult L. Hesperus held under constant temperatures from 12.8 to 35.0°C. In addition, abdominal coloration was measured as a nondestructive indicator of reproductive maturity. The nonlinear models indicated most stages of ovary, seminal vesicle, and medial accessory gland development were subject to mild high-temperature inhibition, except for the stage of filled seminal vesicles. Development of filled seminal vesicles was subject to minor low-temperature inhibition and severe high-temperature inhibition. Estimated development time...
-
temperature dependent development of Lygus Hesperus hemiptera miridae nymphs
Journal of Economic Entomology, 2012Co-Authors: Rodney W Cooper, Dale W SpurgeonAbstract:ABSTRACT Lygus Hesperus Knight (Hemiptera: Miridae) is a key pest of fruit and vegetable crops, forages, and cotton (Gossypium spp.) in the western United States. Accurate models describing relationships between temperature and L. Hesperus development are critical to the study of seasonal L. Hesperus population dynamics. Development of L. Hesperus nymphs was assessed at nine constant temperatures from 10 to 37.8°C. The relationships between temperature and development for each L. Hesperus instar, and for the entire nymphal stage, were best described by six-parameter biophysical models indicating both low- and high-temperature inhibition of development. Development rates asymptotically approached zero with decreasing temperature in the lower thermal range, and decreased with increasing temperatures above 32.2°C. Nymphs did not survive from egg hatch to adulthood at either 10 or 37.8°C, and nymph mortality was >90% at both 12.8 and 35.0°C. The fifth instar exhibited the longest stadium, whereas the shortest...
