Beltsville Agricultural Research Center

Baltimore Highlands, MD, United States

Beltsville Agricultural Research Center

Baltimore Highlands, MD, United States
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Parker M.L.,University of Victoria | Penarete-Vargas D.M.,Montpellier University | Hamilton P.T.,University of Victoria | Guerin A.,Montpellier University | And 5 more authors.
Proceedings of the National Academy of Sciences of the United States of America | Year: 2016

Plasmodium falciparum and Toxoplasma gondii are widely studied parasites in phylum Apicomplexa and the etiological agents of severe human malaria and toxoplasmosis, respectively. These intracellular pathogens have evolved a sophisticated invasion strategy that relies on delivery of proteins into the host cell, where parasite-derived rhoptry neck protein 2 (RON2) family members localize to the host outer membrane and serve as ligands for apical membrane antigen (AMA) family surface proteins displayed on the parasite. Recently, we showed that T. gondii harbors a novel AMA designated as TgAMA4 that shows extreme sequence divergence from all characterized AMA family members. Here we show that sporozoite-expressed TgAMA4 clusters in a distinct phylogenetic clade with Plasmodium merozoite apical erythrocyte-binding ligand (MAEBL) proteins and forms a high-affinity, functional complex with its coevolved partner, TgRON2L1. High-resolution crystal structures of TgAMA4 in the apo and TgRON2L1-bound forms complemented with alanine scanning mutagenesis data reveal an unexpected architecture and assembly mechanism relative to previously characterized AMA-RON2 complexes. Principally, TgAMA4 lacks both a deep surface groove and a key surface loop that have been established to govern RON2 ligand binding selectivity in other AMAs. Our study reveals a previously underappreciated level of molecular diversity at the parasite-host-cell interface and offers intriguing insight into the adaptation strategies underlying sporozoite invasion. Moreover, our data offer the potential for improved design of neutralizing therapeutics targeting a broad range of AMA-RON2 pairs and apicomplexan invasive stages.

Home > Press > News from Quorum: The Agricultural Research Service of the USDA uses a Quorum Cryo-SEM preparation system for the study of mites, ticks and other soft bodied organisms Abstract: Quorum Technologies, market and technology leaders in electron microscopy coating and cryogenic preparation products, report on the work of the Agricultural Research Service of the US Department of Agriculture where their PP2000 Cryo-SEM preparation system is in use to prepare soft bodied organisms including mites & ticks for study using cryo-SEM Dr Gary Bauchan is the Director of the Electron and Confocal Microscopy Unit at the Agricultural Research Service (ARS), the principal in-house research agency of the United States Department of Agriculture. The Unit is a core facility with the responsibility of providing collaborative assistance to scientists from ARS, Northeast Area and Beltsville Agricultural Research Center (BARC) who have microscopy applications that require high resolution imaging. Dr Bauchan’s team have produced images using electron microscopes of bacteria, fungi, mites, insects, nematodes and parasites along with plant and animal tissues both healthy and diseased. One of his major collaborations is with Dr Ron Ochoa, the world's expert on plant feeding mites. Biological specimens require special treatment due to the high water content of the samples. Many of the specimens are in liquid cultures or are very soft-bodied and by using classical preparative techniques will either destroy the specimen or distort the specimen producing artefacts. A cryo-prep system is an ultra-fast method to ready the specimens for observation in a SEM especially a high resolution field emission SEM. Thus, specimens are frozen in time to allow for observation of feeding behaviour, mating behaviour, host/parasite interactions, etc. It preserves the natural orientation of ultrafine structures such as setae, antenna, legs, skin texture, sensory organs, waxy coatings and eggs. Asked about his experience using a Quorum PP2000 Cryo-SEM preparation system on the Hitachi S-4700 field emission scanning electron microscope, Dr Bauchan said “The Quorum system is easy to use, the set-up for imaging is logical, durable, reliable, and maintains ultra-low temperatures for a long period of time. Holders containing pre-frozen samples are transferred into the cryo-prep chamber where they are etched to remove any surface contamination (condensed water vapour) by raising the temperature of the stage from -130 ºC to -90 °C for 10-15 minutes. Following etching, the temperature inside the chamber was lowered below -130 °C, and the specimens were coated with a 10 nm layer of platinum using a magnetron sputter head equipped with a platinum target. The specimens were transferred to a pre-cooled (-130 °C) cryo-stage in the SEM for observation.” The system has been used in multiple projects by the Unit, many of which have been published with the generation of stunning, colourful images. The use of low temperature SEM has been shown time and again to be the best method for the examination of microscopic biological specimens and their ultrastructure. The work in conjunction with Dr Ochoa has been particularly productive with five papers published this year to date. These have focused on the field of acarology, a branch of zoology dealing with the study of mites and ticks. The PP2000 is one of Quorum's highly automated, easy-to-use, column-mounted, gas-cooled cryo-SEM preparation systems suitable for most makes and models of SEM, FE-SEM and FIB/SEM. To obtain full details of the latest cryo-SEM preparation systems and other products available from Quorum Technologies, please visit Note to editors from USDA-ARS: “Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the USDA.” About Quorum Technologies Limited Quorum Technologies are market and technology leaders in electron microscopy (EM) coating and cryogenic preparation. The company was founded in 2001 after the acquisition of the long-established Polaron brand and its range of EM products from Thermo Instruments. In 2005, Quorum acquired the Emitech company allowing the extension of their product range and further growth of the business. Since the start, Quorum has responding to industry requests and requirements for new instruments and techniques. This first culminated in the introduction of the market-leading Q Series of vacuum coaters and PP3010T cryo preparation system for SEM and FIB/SEM - true ground-up redesigns that have truly set the standard within the specimen preparation field. Further impetus and investment came with the acquisition of Quorum by Judges Scientific plc and a move to purpose-built factory and offices close to the South Downs National Park at Laughton, East Sussex in the South East of England. In 2014 Quorum were proud winners of the Queen's Award for Enterprise for International Trade. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Nemchinov L.G.,Beltsville Agricultural Research Center
European Journal of Plant Pathology | Year: 2017

Alfalfa (Medicago sativa) is a natural host plant for many plant pathogens including fungi, bacteria, nematodes and viruses. Alfalfa latent virus (ALV) is strain of Pea streak virus, a member of the carlavirus group that occurs symptomlessly in alfalfa. The first complete genomic sequence of the ALV that was recently obtained in our laboratory showed that the virus differs substantially from other members of the genus Carlavirus. Here we report generation of infectious RNA transcripts from the constructed full-length viral cDNA clone as a proof that ALV nucleotide sequence is correct and as an initial step toward development of the ALV-based vector for gene silencing and expression of foreign proteins in alfalfa. This is the first report describing the development of a complete cDNA clone of the ALV strain of Pea streak virus and its infectivity in the diagnostic pea (Pisum sativum) and natural alfalfa hosts. © 2017 US Government

Dubey J.P.,Beltsville Agricultural Research Center
Veterinary Parasitology | Year: 2017

Oocysts are important stage for the spread of Toxoplasma gondii because they are environmentally resistant. Among all hosts of T. gondii, only felids can excrete oocysts. Cats that have excreted T. gondii oocysts after primary infection develop immunity to re-excretion of oocysts, and this immunity appears to be long-lasting. It would be desirable to have a non-infectious vaccine for the prevention of T. gondii infection in cats and to understand mechanism of immunity to excretion of oocysts. An initial step will be to indentify stage/stages of the parasite for induction of immunity. A chemically-induced mutant of T. gondii, T-263, is immunogenic but lacks the capacity to form oocysts in cats. Cats fed live bradyzoites of T-263 do not excrete oocysts after challenge with oocyst producing strains. However, it is not known at what stage of the parasite development the oocyst formation is halted. Here, four cats were fed live tissue cysts of the T-263 strain and examined for enteroepithelial stages and oocyst production. Two cats were administered methyl prednisolone aceatate (20. mg/kg) once intramuscularly and these cats were euthanized 5 and 7. days post inoculation. No oocysts but immature and mature schizonts (types D and E), male, and female gamonts were detected in two cats euthanized. The remaining two cats did not excrete oocysts examined 3-14. days post inoculation, but both seroconverted and developed antibody titers of 1:400 tested by the modification agglutination test, indicating exposure to the inocula. The results demonstrate that the T-263 strain is defective in oocyst formation and the observations should help future studies in identification of genes/factors responsible for oocyst formation in the intestine of cats. © 2017.

Bevacqua C.E.,University of Maryland College Park | Rice C.P.,Beltsville Agricultural Research Center | Torrents A.,University of Maryland College Park | Ramirez M.,District of Columbia Water and Sewer Authority
Science of the Total Environment | Year: 2011

Steroid hormones can act as potent endocrine disruptors when released into the environment. The main sources of these chemicals are thought to be wastewater treatment plant discharges and waste from animal feeding operations. While these compounds have frequently been found in wastewater effluents, few studies have investigated biosolids or manure, which are routinely land applied, as potential sources. This study assessed the potential environmental contribution of steroid hormones from biosolids and chicken litter. Hormone concentrations in samples of limed biosolids collected at a waste treatment plant over a four year period ranged from < 2.5 to 21.7. ng/g dry weight for estrone (E1) and < 2.5 to 470. ng/g dry weight for progesterone. Chicken litter from 12 mid-Atlantic farms had averages of 41.4. ng/g dry weight E1, 63.4. ng/g dry weight progesterone, and 19.2. ng/g dry weight E1-sulfate (E1-S). Other analytes studied were 17β-estradiol (E2), estriol (E3), 17β-ethinylestradiol (EE2), testosterone, E2-3-sulfate (E2-3-S), and E2-17-sulfate (E2-17-3). © 2011 Elsevier B.V.

Delwiche S.R.,U.S. Department of Agriculture | Kim M.S.,Beltsville Agricultural Research Center | Dong Y.,University of Minnesota
Sensing and Instrumentation for Food Quality and Safety | Year: 2011

Fusarium head blight is a fungal disease that affects the world's small grains, such as wheat and barley. Attacking the spikelets during development, the fungus causes a reduction of yield and grain of poorer processing quality. Secondary metabolites that often accompany the fungus, such as deoxynivalenol (DON), are health concerns to humans and livestock. Conventional grain inspection procedures for Fusarium damage are heavily reliant on human visual analysis. As an inspection alternative, a near-infrared (NIR) hyperspectral image system (1000-1700 nm) was fabricated and applied to Fusarium-damaged kernel recognition. An existing extended visible (400-1000 nm) system was similarly used. Exhaustive searches were performed on the 144 and 125 wavelength pair images that, respectively, comprised the NIR and visible systems to determine accuracy of classification using a linear discriminant analysis (LDA) classifier. On a limited set of wheat samples the best wavelength pairs, either with visible or NIR wavelengths, were able to discriminate Fusarium-damaged kernels from sound kernels, both based on visual assessment, at an average accuracy of approximately 95%. Accuracy dropped off substantially when the visual contrast between the two kernel conditions became imperceptible. The NIR region was slightly better than the visible region in its broader array of acceptable wavelength pairs. Further, the region of interest (ROI) defined as the whole kernel was slightly better than ROIs limited to either a portion of the endosperm or the germ tip. For the NIR region, the spectral absorption near 1200 nm, attributed to ergosterol (a primary constituent in fungi cell membranes), was shown to be useful in spectral recognition of Fusarium damage. © 2011 Springer Science+Business Media, LLC.

Farnham M.W.,U.S. Department of Agriculture | Lester G.E.,Beltsville Agricultural Research Center | Hassell R.,Clemson University
Journal of Food Composition and Analysis | Year: 2012

Leaf green Brassica crops: collard (Brassica oleracea L.), mustard (Brassica juncea L.) and turnip (Brassica rapa L.) greens are important commercial and culinary vegetables, especially in the southern United States. However, almost no information on essential human-health vitamins [ascorbic acid (vitamin C), folate (vitamin B 9), phylloquinone (vitamin K 1) and the carotenoids lutein and β-carotene (provitamin A)] is available. Leafy green Brassicas (15 collard, 2 mustard and 2 turnip greens) were harvested at peak whole-plant maturity, separated into younger (top-canopy) or older (bottom-canopy) leaves and assayed for the aforementioned vitamins and carotenoids. On a 100g fresh mass basis, percent dry mass (14.7g versus 13.2g), total (132.7mg versus 109.1mg) and free (58.7mg versus 52.8mg) ascorbic acid, folate (183μg versus 112μg) and lutein (9790μg versus 8950μg) concentrations were significantly higher in younger versus older leaves. Phylloquinone (435μg versus 459μg) and β-carotene (11,130μg versus 11,619μg) were equally concentrated in younger and older leaves. On a fresh mass basis, all vitamins were found to be highly concentrated in all nineteen leafy green Brassica genotypes, with particular genotypes within each Brassica species having exceptionally high concentrations. Findings from this study revealed that leafy green Brassica genotypes are nutritionally dense in essential human-health vitamins C, B 9, K, provitamin A (β-carotene) and lutein. Concentration differences in the examined nutritional components among the genotypes (e.g. significant differences in lutein concentrations from 5120 to 15,360μg/100gfm) reveal potential differences that might be exploited in genetic improvement through plant selection and breeding. © 2012.

Postnikova O.A.,Beltsville Agricultural Research Center | Shao J.,Beltsville Agricultural Research Center | Nemchinov L.G.,Beltsville Agricultural Research Center
Molecular Genetics and Genomics | Year: 2014

Transcription factors (TFs) are proteins that govern organismal development and response to the environment by regulating gene expression. Information on the amount and diversity of TFs within individual plant species is critical for understanding of their biological roles and evolutionary history across the plant kingdom. Currently, only scattered information on separate TFs is available for alfalfa, the most extensively cultivated forage legume in the world. In the meantime, several large transcriptomic resources that can be used to identify and characterize alfalfa TF genes are freely accessible online. In this study, we have performed an in silico analysis of transcriptome data generated in our laboratory and publicly acquirable from other sources to reveal and systematize alfalfa transcription factors. Transcriptome-wide mining enabled prediction of 983 TFs along with their sequence features and putative phylogenies of the largest families. All data were assembled into a simple open-access database named AlfalfaTFDB ( alfalfatfdb.html ). Transcriptomic analysis used in this work represents an effective approach for the identification of TF genes in plants with incomplete genomes, such as alfalfa. Integrated TF repertoires of Medicago sativa will provide an important tool for studying regulation of gene expression in other complex non-model species of agricultural significance. © 2014 Springer-Verlag.

Yang T.,Beltsville Agricultural Research Center | Peng H.,Beltsville Agricultural Research Center | Whitaker B.D.,Beltsville Agricultural Research Center | Jurick W.M.,Beltsville Agricultural Research Center
Physiologia Plantarum | Year: 2013

Calcium has been shown to enhance stress tolerance, maintain firmness and reduce decay in fruits. Previously we reported that seven tomato SlSRs encode calcium/calmodulin-regulated proteins, and that their expressions are developmentally regulated during fruit development and ripening, and are also responsive to ethylene. To study their expressions in response to stresses encountered during postharvest handling, tomato fruit at the mature-green stage was subjected to chilling and wounding injuries, infected with Botrytis cinerea and treated with salicylic acid or methyl jasmonate. Gene expression studies revealed that the seven SlSRs differentially respond to different stress signals. SlSR2 was the only gene upregulated by all the treatments. SlSR4 acted as a late pathogen-induced gene; it was upregulated by salicylic acid and methyl jasmonate, but downregulated by cold treatment. SlSR3L was cold- and wound-responsive and was also induced by salicylic acid. SlSR1 and SlSR1L were repressed by cold, wounding and pathogen infection, but were upregulated by salicylic acid and methyl jasmonate. Overall, results of these expression studies indicate that individual SlSRs have distinct roles in responses to the specific stress signals, and SlSRs may act as a coordinator(s) connecting calcium-mediated signaling with other stress signal transduction pathways during fruit ripening and storage. © 2013 Scandinavian Plant Physiology Society.

Metabolites and stress related transcripts were measured in Arabidopsis thaliana in response to chilling temperatures. Rates of carbon assimilation increased 17% on average in response to cold treatment. Sucrose, glucose and fructose accumulation consumed 42% of the carbon from A but leaf starch only could synthesize ∼10% of observed changes in soluble sugars. Carbohydrates were the only major class of metabolites that accumulated during the first 24. h of cold treatment. Except maltose and raffinose, carbohydrate accumulation was abolished when cold treatments were in darkness. Starch hydrolysis was correlated with maltose accumulation and increased expression of BAM3, which encodes a β-amylase necessary for starch mobilization. Hexose accumulation was delayed 6. h and raffinose accumulation was not observed in a starchless (pgm1) mutant. Changes of expression of five stress-induced transcripts in response to cold were similar in the wild type and in the pgm1 mutant. Three of five stress related transcripts had decreased expression when cold treatments were performed in the dark compared to the light. Therefore, starch hydrolysis may augment hexose and raffinose accumulations during the first 24. h after a cold shock and a partial cold stress response was observed in Arabidopsis during cold treatments in the dark. © 2011.

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