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ABSTRACT: Aphid (Hemiptera: Aphididae) saliva, when injected into host plants during feeding, causes physiological changes in hosts that facilitate aphid feeding and cause injury to plants. Comparing salivary constituents among aphid species could help identify which salivary products are universally important for general aphid feeding processes, which products are involved with specific host associations, or which products elicit visible injury to hosts. We compared the salivary proteins from five aphid species, namely, Diuraphis noxia (Kurdjumov), D. tritici (Gillette), D. mexicana (Baker), Schizaphis graminum (Rondani), and Acyrthosiphon pisum (Harris). A 132-kDa protein band was detected from the saliva of all five species using sodium dodecyl sulfate polyacrylamide gel electrophoresis. Alkaline phosphatase activity was detected from the saliva of all five species and may have a universal role in the feeding process of aphids. The Diuraphis species cause similar visible injury to grass hosts, and nine electrophoretic bands were unique to the saliva of these three species. S. graminum shares mutual hosts with the Diuraphis species, but visible injury to hosts caused by S. graminum feeding differs from that of Diuraphis feeding. Only two mutual electrophoretic bands were visualized in the saliva of Diuraphis and S. graminum. Ten unique products were detected from the saliva of A. pisum, which feeds on dicotyledonous hosts. Our comparisons of aphid salivary proteins revealed similarities among species which cause similar injury on mutual hosts, fewer similarities among species that cause different injury on mutual hosts, and little similarity among species which feed on unrelated hosts.
Environmental Entomology 02/2011; 40(1):151-6. · 1.56 Impact Factor
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ABSTRACT: Salivary secretions play critical roles in aphid-host plant interactions and are responsible for damage associated with aphid feeding. The objectives of this study were to evaluate aspects of salivation and the salivary constituents of Diuraphis noxia (Hemiptera: Aphididae). Salivary proteins were isolated and compared from three aphid probed diets: pure water, 15% sucrose, or amino acids (100 mM serine, 100 mM methionine, 100 mM aspartic acid, and 15% sucrose). After 6 h, more aphids settled on sucrose diet compared with other diets, but there were no significant differences in the number of stylet sheaths produced per aphid after 24 h. There were differences in the amount of soluble salivary protein (watery saliva), with the greatest amount secreted in sucrose diet, followed by amino acid diet and pure water, respectively. Protein constituents secreted into sucrose and amino acid diets were compared using gel electrophoresis using standardized amounts of protein. More protein bands and bands of greater intensity were visualized from probed sucrose diet compared with probed amino acid diet, indicating qualitative differences. Phosphatase was putatively identified from D. noxia saliva from a major protein band using gel electrophoresis and mass spectrophotometry. Alkaline phosphatase activity was confirmed in sucrose diet using enzymatic assays but was not detected in aphid probed water or amino acid diets. Other peptides in sucrose diet weakly but significantly showed similarities to putative dehydrogenase and RNA helicase expressed sequence tags identified from other aphids. The implications of these findings in aphid salivation and plant-insect interactions are discussed.
Environmental Entomology 02/2010; 39(1):223-31. · 1.56 Impact Factor
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ABSTRACT: The importance of host plant effects on aphids, and their natural enemies, has been well documented. However, few studies have isolated the mechanisms that determine suitability of insect prey among host plants for the survival and development of predators. We evaluated the nutritional interactions among alfalfa, Medicago sativa L. ‘OKO8’, and faba bean, Vicia faba L. ‘Windsor’, host plants, pea aphid herbivores, Acyrthosiphon pisum (Harris), and a lacewing predator, Chrysoperla rufilabris Burmeister. The survival and development of lacewing larvae supplied with five daily levels (1.2–16.4 mg) of pea aphids reared on either alfalfa or faba bean were documented. Compared with aphids reared on faba bean, those reared on alfalfa stored 6.3 times greater levels of myristic acid resulting in a 2.7-fold increase in total fatty acid content (micrograms per milligram of aphid weight). This increase in total fatty acids equated to an ≈1.3-fold increase in available calories for C. rufilabris provided with pea aphids reared on alfalfa. There were no statistical differences among treatments in the ratio of lacewing individuals surviving to the pupal or adult stage. The ratio of deformed lacewing adults increased with decreasing daily prey levels, and this increase was greatest for C. rufilabris supplied with pea aphids reared on faba beans. Lacewing larvae supplied with pea aphids reared on alfalfa had faster developmental rates (1/d) than C. rufilabris larvae supplied with pea aphids reared on faba beans. Interestingly, these differences in developmental rates between host plants continued to occur after the rates plateaued at the highest daily prey level. The separation of C. rufilabris developmental rates between host plants at low and high daily pea aphid levels does not support the hypothesis that quantitative differences in the nutritional value of pea aphids, as influenced by differences in fatty acids and calculated nutrition levels (calories) between pea aphids reared on separate plant hosts, were responsible for differences in C. rufilabris developmental rates. Rather, separation of developmental rates at low and high daily prey levels, and no statistical interactions between daily prey levels and host plants, suggest qualitative differences in the nutritional value of pea aphids between host plants.
Environmental Entomology 01/2009; · 1.56 Impact Factor
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ABSTRACT: The wheat leaf proteome was mapped and partially characterized to function as a comparative template for future wheat research. In total, 404 proteins were visualized, and 277 of these were selected for analysis based on reproducibility and relative quantity. Using a combination of protein and expressed sequence tag database searching, 142 proteins were putatively identified with an identification success rate of 51%. The identified proteins were grouped according to their functional annotations with the majority (40%) being involved in energy production, primary, or secondary metabolism. Only 8% of the protein identifications lacked ascertainable functional annotation. The 51% ratio of successful identification and the 8% unclear functional annotation rate are major improvements over most previous plant proteomic studies. This clearly indicates the advancement of the plant protein and nucleic acid sequence and annotation data available in the databases, and shows the enhanced feasibility of future wheat leaf proteome research.
PROTEOMICS 05/2005; 5(6):1624-33. · 4.51 Impact Factor
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ABSTRACT: Pea aphids, Acyrthosiphon pisum (Harris), reared at 10 degrees C contain higher levels of fatty acids than those reared at 25 degrees C. This is primarily the result of an accumulation of triacylglycerols containing myristic acid. When aphids reared at 25 degrees C were transferred to 10 degrees C there was a gradual increase in triacylglycerol content that reached a maximum at 16 days post-transfer. Treatment of aphids with precocene II prior to transfer to 10 degrees C blocked the accumulation of fatty acids including myristic acid. A single application of 2 microg precocene II/aphid or two applications of 0.5 microg precocene II/ aphid administered on consecutive days resulted in aphids moved to 10 degrees C maintaining the same fatty acid profile as aphids maintained at 25 degrees C. Aphids that were treated with precocene II and maintained at 25 degrees C did not show changes in fatty acid profiles. Rearing aphids at 10 degrees C resulted in lower rates of reproduction and lower total numbers of progeny with longer longevity. Treatment with precocene II significantly decreased the total number of progeny produced at both temperatures. Precocene II did not reduce life span of aphids reared at 25 degrees C, however, the life span of treated aphids reared at 10 degrees C was decreased. The mechanism by which precocene II prevents the accumulation of myristic acid in aphids reared at 10 degrees C remains to be determined.
Journal of Insect Physiology 05/2005; 51(4):411-6. · 2.24 Impact Factor
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ABSTRACT: Fatty acids of spotted alfalfa aphids, Therioaphis maculata (Buckton), were compared to determine what effects host condition and susceptibility to aphids have on fatty acid metabolism. Myristic acid was the predominant fatty acid in aphids that were feeding on newly infested, green alfalfa tissues. In contrast, linoleic acid was the predominant fatty acid in aphids that were feeding on chlorotic leaves 14 days after the plants were infested. Amounts of myristic acid per mg of aphid, examined 14 days after the plants were infested, were ca. 71% less than that for aphids collected from alfalfa 4 days after the plants were infested. Amounts of linoleic acid per mg of aphid live weight did not change over this period. These changes in spotted alfalfa aphid fatty acids were not due to variations in either fatty acid compositions of aphid life stages or alfalfa fatty acids.Ratios of myristic acid to linoleic acid varied in aphids removed from plants 4 days after infestation compared to aphids with which the plants were originally infested. These ratios increased in aphids feeding on alfalfa plants that were susceptible to spotted alfalfa aphids and decreased in aphids feeding on plants that exhibited resistance characteristics of antibiosis and/or antixenosis.
Archives of Insect Biochemistry and Physiology 02/2005; 18(1):1 - 12. · 1.36 Impact Factor
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ABSTRACT: The wheat leaf proteome was mapped and partially characterized to function as a comparative template for future wheat research. In total, 404 proteins were visualized, and 277 of these were selected for analysis based on reproducibility and relative quantity. Using a combination of protein and expressed sequence tag database searching, 142 proteins were putatively identified with an identification success rate of 51%. The identified proteins were grouped according to their functional annotations with the majority (40%) being involved in energy production, primary, or secondary metabolism. Only 8% of the protein identifications lacked ascertainable functional annotation. The 51% ratio of successful identification and the 8% unclear functional annotation rate are major improvements over most previous plant proteomic studies. This clearly indicates the advancement of the plant protein and nucleic acid sequence and annotation data available in the databases, and shows the enhanced feasibility of future wheat leaf proteome research.
PROTEOMICS. 01/2005; 5(6):1624-1633.
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ABSTRACT: The saliva of ticks contains a complex mixture of bioactive molecules including proteins that modulate host responses ensuring successful feeding. The limited amount of saliva that can be obtained from ticks has hampered characterization of salivary proteins using traditional protein chemistry. Recent improvements in two-dimensional gel electrophoresis, mass spectrometry, and bioinformatics provide new tools to characterize small amounts of protein. These methods were employed to characterize salivary proteins from Amblyomma americanum and Amblyvomma maculatum. Salivation was induced by injection of dopamine and theophylline. It was necessary to desalt and concentrate saliva before analysis by 2-D electrophoresis. Comparison of 1-D and 2-D gel patterns revealed that the major protein component of saliva did not appear on 2-D gels. Characterization of this protein showed that it was identical to the major protein present in the hemolymph of both tick species. Protein profiles obtained by 1-D and 2-D gel electrophoresis were similar for both tick species, however, higher concentrations of lower molecular weight proteins were present in A. maculatum. Protein analysis by MALDI-TOF mass spectrometry and western blot analysis showed that except for the most abundant protein with a molecular weight of 95 kDa, all of the proteins detected were of host origin. It is not known if this is an artifact of the collection method or has physiological significance. In either case, in these species of ticks, host proteins will have to be removed from saliva samples prior to 2-D analysis in order to characterize lower abundance proteins of tick origin.
Enperimental and Applied Acarology 02/2004; 32(1-2):77-87. · 1.73 Impact Factor
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ABSTRACT: The salivary glands and saliva from the lone star tick Amblyomma americanum (L.) were analyzed for the presence of the two endogenous agonists of cannabinoid receptors, N-arachidonoylethanolamine (anandamide) and 2-arachidonoylglycerol (2-AG), as well as of the anandamide congener, N-palmitoylethanolamine (PEA), an anti-inflammatory and analgesic mediator that is inactive at cannabinoid receptors. Two very sensitive mass-spectrometric techniques were used for this purpose. Both 2-AG and PEA, as well as other N-acylethanolamines (NAEs), were identified in salivary glands, but anandamide was below detection. The levels of 2-AG were considerably higher in the salivary glands of partially fed than replete females. Ex vivo gland stimulation with arachidonic acid increased the levels of 2-AG, but not of PEA or other NAEs, and caused the formation of anandamide and of the potent analgesic compound N-arachidonoylglycine. Instead, the amounts of anandamide, 2-AG and PEA were not influenced by treatment of salivary glands with dopamine, which stimulates saliva secretion. The possible biosynthetic precursors of anandamide, PEA and other NAEs were also detected in salivary glands, whereas only PEA was detected in tick saliva. These data demonstrate for the first time that the salivary glands of an obligate ectoparasite species can make endocannabinoids and/or related congeners with analgesic and anti-inflammatory activity, which possibly participate in the inhibition of the host defense reactions.
Biochimica et Biophysica Acta 08/2003; 1633(1):61-7. · 4.66 Impact Factor
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ABSTRACT: Hippodamia convergens Guérin-Méneville and Coccinella septempunctata L. (Coleoptera: Coccinellidae) larvae were supplied daily with 1, 2, 4, or 16 mg of Acyrthosiphon kondoi Shinji (Homoptera: Aphididae) reared on one of two susceptible ('OK08' or 'CUF-101') or one resistant ('54H55') alfalfa cultivar (IMedicago sativa L.) . Hippodamia convergens survived to the adult stage when supplied with > or = 1 mg of A. kondoi per day from both susceptible and aphid-resistant cultivars, whereas C. septempunctata required > or = 2 mg of A. kondoi per day (from each cultivar) for survival to the adult stage. For both H. convergens and C. septempunctata, no consistent differences in survivorship or developmental times were observed between predator larvae supplied with increasing daily levels of A. kondoi from susceptible (OKO8 orCUF-101) versus resistant (54H55) cultivars. Additionally, alfalfa cultivar had no indirect influence on adult weight of H. convergens or C. septempunctata. Results from our study suggest that the resistant alfalfa cultivar (54H55) would have little to no effect on the nutritional value of A. kondoi for ladybeetle predators.
Journal of Economic Entomology 06/2002; 95(3):552-7. · 1.70 Impact Factor
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ABSTRACT: Coleomegilla maculata (DeGeer) and Hippodamia convergens Guérin-Méneville larvae were supplied daily with ≈1.2, 2.2, 4.3, 8.2, or 16.4 mg of Acyrthosiphon pisum Harris reared on either alfalfa Medicago sativa L. (`OK08') or faba beans Vicia faba L. (`Windsor'). Myristic acid and total fatty acid content (μg/mg aphid fresh weight) were 6.3 and 2.7 times greater, respectively, in pea aphids reared on alfalfa as compared with faba beans, resulting in a 1.17-fold increase in caloric content. Higher survival ratios were observed for both C. maculata and H. convergens supplied with low daily prey levels of pea aphids reared on alfalfa versus faba beans, but no differences were observed at higher prey levels. When pea aphids reared on alfalfa were supplied to C. maculata and H. convergens larvae at low prey levels, preimaginal developmental times were significantly reduced compared with those supplied with pea aphids reared on faba beans at the same prey levels. At higher daily pea aphid levels, C. maculata and H. convergens developmental times were not significantly different between host plants. At lower daily prey levels, C. maculata and H. convergens elliptical body area was larger when supplied with pea aphids reared on alfalfa, but body areas were similar at higher daily prey levels. Convergence of survival ratios, developmental times, and elliptical body areas for C. maculata and H. convergens at high (less limiting) prey levels supports the hypothesis that differences in prey nutritional value between pea aphids reared on alfalfa versus faba beans are quantitative and appear to be primarily influenced by differences in pea aphid myristic acid content.
Environmental Entomology 09/2001; 30(5):964-971. · 1.56 Impact Factor
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ABSTRACT: Feeding by the spotted alfalfa aphid, Therioaphis maculata (Buckton), on susceptible alfalfa, Medicago sativa L., results in dramatic changes in plant biochemistry that in turn have profound effects on aphid physiology. These aphids select older leaves on the plant as feeding sites. One component of this selection process may be the amount and composition of plant epicuticular lipids, which vary with leaf age. Feeding aphids induce a senescence-like state in the leaf that is characterized by loss of chlorophyll, decreased levels of soluble protein and fatty acids, and increased production of ethylene. This process involves lipid peroxidation and, like senescence, is probably free-radical-mediated. Leaves of alfalfa having resistance to spotted alfalfa aphid contain higher activities of catalase than do susceptible leaves. This enzyme may function in concert with other antioxidant enzymes to quench aphid-induced free radical damage and thus impart resistance. Aphid fatty acid metabolism is altered by changes in plant metabolism and thus reflects the close relationship between aphid and plant biochemistry.
Archives of Insect Biochemistry and Physiology 12/1990; 17(4):235 - 251. · 1.36 Impact Factor
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ABSTRACT: Prostaglandins of the 2-series (e.g. PGE2) are typically synthesized from arachidonic acid (AA) after AA is released from cellular phospholipids after activation of an intracellular phospholipase A2 (PLA2). Treatment of isolated salivary glands with PLA2 inhibitor oleyloxyethyl phosphorylcholine (OPC) or prostaglandin synthetase inhibitors reduced dopamine-induced fluid secretion and cyclic AMP (cAMP) levels in isolated salivary glands. PGE2 and its analog, 17-phenyl trinor PGE2, partly reversed the inhibition of secretion and cAMP level by OPC, suggesting that prostaglandins may have an autocrine effect in modulating tick salivary gland function. A specific PGE2 receptor was identified in the plasma membrane fraction of the salivary glands. The receptor exhibits a single, high affinity PGE2 binding site with a KD≈ 29 nM, is saturable, reversible, and specific for PGE2 and coupled to a cholera toxin-sensitive guanine nucleotide regulatory protein. Assay of adenylate cyclase activity in salivary gland membranes showed that PGE2 neither stimulated nor inhibited adenylate cyclase activity, indicating that the PGE2 effects on cAMP levels and possibly secretion are indirect, and that the PGE2 receptor stimulates an alternate “second messenger” pathway.
Insect Biochemistry and Molecular Biology.
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ABSTRACT: Previous studies identified a prostaglandin E2 (PGE2) receptor in the salivary glands of partially fed female lone star ticks, Amblyomma americanum (L.). In the present studies, protein secretion from dispersed salivary gland acini was shown to be specific for PGE2, as compared with PGF2α or the thromboxane analog U-46619, in accordance with their respective binding affinities for the PGE2 receptor. Furthermore, the selective PGE2 EP1 receptor agonist, 17-phenyl trinor PGE2, was as effective as PGE2 in stimulating secretion of anticoagulant protein. Calcium ionophore A-23187 (1 to 100 μM) stimulated secretion of anticoagulant protein in a dose-dependent manner but the voltage-gated Ca2+-channel blocker verapamil (1 to 1000 μM) and the receptor-mediated Ca2+-entry antagonist, SK&F 96365 (1 and 10 μM), and 5 mM ethylene glycol bis(β-aminoethyl ether)-N,NN′,N′-tetraacetic acid (EGTA) had no appreciable effect on inhibiting PGE2-stimulated secretion of anticoagulant protein. PGE2 (0.1 μM) and the non-hydrolyzable analog of guanosine triphosphate (GTP), GTPγS (10 μM), directly activated phospholipase C (PLC) in a membrane-enriched fraction of the salivary glands after PLC was first incubated with the PGE2 EP1 receptor antagonist AH-6809, which presumably antagonized endogenous PGE2 (0.3 μM) in the broken-cell-membrane-enriched fraction. TMB-8, an antagonist of intracellular inositol trisphosphate (IP3) receptors, inhibited PGE2-stimulated secretion. The results support the hypothesis that PGE2 stimulates secretion of tick salivary gland protein via a phosphoinositide signaling pathway and mobilization of intracellular Ca2+.
Insect Biochemistry and Molecular Biology.
