| astragalus bisulcatus--a cause of selenium or locoweed poisoning? | certain plants accumulate selenium at levels that render them toxic. one of the principle groups of selenium-accumulating plants is the selenium-accumulating astragalus. reports in early literature suggest that selenium is the only toxin in these plants. sheep fed astragalus bisulcatus, a selenium-accumulating plant, had signs similar to those observed in locoweed poisoning, and the microscopic lesions from tissues collected from these sheep were similar to those of locoweed poisoning rather tha ... | 1983 | 6845629 |
| reproductive response of ewes fed alfalfa pellets containing sodium selenate or astragalus bisulcatus as a selenium source. | selenium fed to open cycling ewes in the form of sodium selenate or astragalus bisulcatus (a selenium accumulator plant) at 24 or 29 ppm selenium, respectively, in alfalfa hay pellets did not alter the estrous cycle length, estrus behavior, progesterone or estrogen profiles, pregnancy rate or outcome of parturition (p > 0.05). there was wool loss in some ewes fed seleniferous pellets and the mean whole blood selenium levels were 0.45, 1.3 and 2.4 ppm, respectively, for control, a bisulcatus and ... | 1995 | 7709586 |
| comparative toxicity of selenium from seleno-dl-methionine, sodium selenate, and astragalus bisulcatus in pigs. | selenium is an essential micronutrient, although ingestion in excess in pigs can cause disease conditions including neurological dysfunction and chronic skin and hoof lesions. controlled feeding trials in growing swine, using the same se content in feed sources, resulted in higher concentrations (p < or = 0.05) of se in blood and organs of pigs fed seleno-dl-methionine compared with those receiving astragalus bisulcatus or sodium selenate. clinical signs of se toxicity including neurological sig ... | 1996 | 8921324 |
| selenite precipitation by a rhizospheric strain of stenotrophomonas sp. isolated from the root system of astragalus bisulcatus: a biotechnological perspective. | a bacterial strain (seite02), related to the species stenotrophomonas maltophilia and resistant to selenite (seiv) up to 50 mm in the growth medium, was isolated from rhizospheric soil of a selenium hyperaccumulator plant, the legume astragalus bisulcatus. the influence of seiv on the active growth of this se-tolerant bacterial strain has been investigated in oxic conditions, along with the isolate's ability to reduce selenite to elemental selenium (se(0)). interestingly, concentrations of 0.5 m ... | 2005 | 15661289 |
| rhizosphere-induced selenium precipitation for possible applications in phytoremediation of se polluted effluents. | two bacterial isolates were obtained in axenic culture from the rhizosphere soil of astragalus bisulcatus, a legume able to hyperaccumulate selenium. both strains resulted of particular interest for their high resistance to the toxic oxyanion seo3(2-) (selenite, se(iv)). on the basis of molecular and biochemical analyses, these two isolates were attributed to the species bacillus mycoides and stenotrophomonas maltophilia, respectively. their capability in axenic culture to precipitate the solubl ... | 2005 | 15948605 |
| isolation and partial characterization of transfer rnas from astragalus bisulcatus. | a procedure has been developed for the isolation of transfer rna from the selenium accumulator plant astragalus bisulcatus. this material appears free of interfering phenolic compounds, has a high guanosine to cytidine ratio, shows a major and modified nucleoside composition characteristic of plant transfer rnas, and exhibits chromatographic and electrophoretic properties similar to transfer rnas from other well studied bacterial and plant systems. rnas isolated from a. bisulcatus seedlings incu ... | 1979 | 16660758 |
| the role of selenium in protecting plants against prairie dog herbivory: implications for the evolution of selenium hyperaccumulation. | some plants can hyperaccumulate the element selenium (se) up to 10,000 mg se kg(-1) dry weight. hyperaccumulation has been hypothesized to defend against herbivory. in laboratory studies high se levels protect plants from invertebrate herbivores and pathogens. however, field studies and mammalian herbivore studies that link se accumulation to herbivory protection are lacking. in this study a combination of field surveys and manipulative field studies were carried out to determine whether plant s ... | 2008 | 18278517 |
| organoselenides from nicotiana tabacum genetically modified to accumulate selenium. | nicotiana tabacum l. (tobacco) plants were transformed to overexpress a selenocysteine methyltransferase gene from the selenium hyperaccumulator astragalus bisulcatus (hook.) a. gray (two-grooved milkvetch), and an atp-sulfurylase gene from brassica oleracea l. var. italica (broccoli). solvent extraction of leaves harvested from plants treated with selenate revealed five selenium-containing compounds, of which four were identified by chemical synthesis as 2-(methylseleno)acetaldehyde, 2,2-bis(me ... | 2009 | 19570557 |
| selenium hyperaccumulators harbor a diverse endophytic bacterial community characterized by high selenium resistance and plant growth promoting properties. | selenium (se)-rich plants may be used to provide dietary se to humans and livestock, and also to clean up se-polluted soils or waters. this study focused on endophytic bacteria of plants that hyperaccumulate selenium (se) to 0.5-1% of dry weight. terminal restriction fragment length polymorphism (t-rflp) analysis was used to compare the diversity of endophytic bacteria of hyperaccumulators stanleya pinnata (brassicaceae) and astragalus bisulcatus (fabaceae) with those from related non-accumulato ... | 2015 | 25784919 |
| overexpression of selenocysteine methyltransferase in arabidopsis and indian mustard increases selenium tolerance and accumulation. | a major goal of phytoremediation is to transform fast-growing plants with genes from plant species that hyperaccumulate toxic trace elements. we overexpressed the gene encoding selenocysteine methyltransferase (smt) from the selenium (se) hyperaccumulator astragalus bisulcatus in arabidopsis and indian mustard (brassica juncea). smt detoxifies selenocysteine by methylating it to methylselenocysteine, a nonprotein amino acid, thereby diminishing the toxic misincorporation of se into protein. our ... | 2004 | 14671009 |
| selenium distribution and speciation in the hyperaccumulator astragalus bisulcatus and associated ecological partners. | the goal of this study was to investigate how plant selenium (se) hyperaccumulation may affect ecological interactions and whether associated partners may affect se hyperaccumulation. the se hyperaccumulator astragalus bisulcatus was collected in its natural seleniferous habitat, and x-ray fluorescence mapping and x-ray absorption near-edge structure spectroscopy were used to characterize se distribution and speciation in all organs as well as in encountered microbial symbionts and herbivores. s ... | 2012 | 22645068 |
| delayed formation of zero-valent selenium nanoparticles by bacillus mycoides seite01 as a consequence of selenite reduction under aerobic conditions. | selenite (seo32-) oxyanion shows severe toxicity to biota. different bacterial strains exist that are capable of reducing seo32- to non-toxic elemental selenium (se0), with the formation of se nanoparticles (senps). these senps might be exploited for technological applications due to their physico-chemical and biological characteristics. the present paper discusses the reduction of selenite to senps by a strain of bacillus sp., seite01, isolated from the rhizosphere of the se-hyperaccumulator le ... | 2014 | 24606965 |
| effects of selenium hyperaccumulation on plant-plant interactions: evidence for elemental allelopathy? | • few studies have investigated plant-plant interactions involving hyperaccumulator plants. here, we investigated the effect of selenium (se) hyperaccumulation on neighboring plants. • soil and litter se concentrations were determined around the hyperaccumulators astragalus bisulcatus and stanleya pinnata and around the nonhyperaccumulators medicago sativa and helianthus pumilus. we also compared surrounding vegetative cover, species composition and se concentration in two plant species (artemis ... | 2011 | 21371042 |
| spatial imaging, speciation, and quantification of selenium in the hyperaccumulator plants astragalus bisulcatus and stanleya pinnata. | astragalus bisulcatus and stanleya pinnata hyperaccumulate selenium (se) up to 1% of plant dry weight. in the field, se was mostly present in the young leaves and reproductive tissues of both hyperaccumulators. microfocused scanning x-ray fluorescence mapping revealed that se was hyperaccumulated in trichomes in young leaves of a. bisulcatus. none of 10 other elements tested were accumulated in trichomes. micro x-ray absorption spectroscopy and liquid chromatography-mass spectrometry showed that ... | 2006 | 16920881 |
| production of se-methylselenocysteine in transgenic plants expressing selenocysteine methyltransferase. | it has become increasingly evident that dietary se plays a significant role in reducing the incidence of lung, colorectal and prostate cancer in humans. different forms of se vary in their chemopreventative efficacy, with se-methylselenocysteine being one of the most potent. interestingly, the se accumulating plant astragalus bisulcatus (two-grooved poison vetch) contains up to 0.6% of its shoot dry weight as se-methylselenocysteine. the ability of this se accumulator to biosynthesize se-methyls ... | 2004 | 15005814 |
| molybdenum accumulation, tolerance and molybdenum-selenium-sulfur interactions in astragalus selenium hyperaccumulator and nonaccumulator species. | some species hyperaccumulate selenium (se) upwards of 0.1% of dry weight. this study addressed whether se hyperaccumulators also accumulate and tolerate more molybdenum (mo). a field survey revealed on average 2-fold higher mo levels in three hyperaccumulator astragali compared to three nonaccumulator astragali, which were not significantly different. next, a controlled study was performed where hyperaccumulators astragalus racemosus and astragalus bisulcatus were compared with nonaccumulators a ... | 2015 | 26074355 |
| do selenium hyperaccumulators affect selenium speciation in neighboring plants and soil? an x-ray microprobe analysis. | neighbors of se hyperaccumulators stanleya pinnata and astragalus bisulcatus were found earlier to have elevated se levels. here we investigate whether se hyperaccumulators affect se localization and speciation in surrounding soil and neighboring plants. x-ray fluorescence mapping and x-ray absorption near-edge structure spectroscopy were used to analyze se localization and speciation in leaves of artemisia ludoviciana, symphyotrichum ericoides and chenopodium album growing next to se hyperaccum ... | 2015 | 26030363 |
| analysis of selenium accumulation, speciation and tolerance of potential selenium hyperaccumulator symphyotrichum ericoides. | symphyotrichum ericoides was shown earlier to contain hyperaccumulator levels of selenium (se) in the field (>1000 mg kg(-1) dry weight (dw)), but only when growing next to other se hyperaccumulators. it was also twofold larger next to hyperaccumulators and suffered less herbivory. this raised two questions: whether s. ericoides is capable of hyperaccumulation without neighbor assistance, and whether its se-derived benefit is merely ecological or also physiological. here, in a comparative greenh ... | 2014 | 24423113 |
| selenium hyperaccumulator plants stanleya pinnata and astragalus bisulcatus are colonized by se-resistant, se-excluding wasp and beetle seed herbivores. | selenium (se) hyperaccumulator plants can concentrate the toxic element se up to 1% of shoot (dw) which is known to protect hyperaccumulator plants from generalist herbivores. there is evidence for se-resistant insect herbivores capable of feeding upon hyperaccumulators. in this study, resistance to se was investigated in seed chalcids and seed beetles found consuming seeds inside pods of se-hyperaccumulator species astragalus bisulcatus and stanleya pinnata. selenium accumulation, localization ... | 2012 | 23226523 |
| selenium hyperaccumulation by astragalus (fabaceae) does not inhibit root nodule symbiosis. | | 2012 | 23204487 |
| interactions of selenium hyperaccumulators and nonaccumulators during cocultivation on seleniferous or nonseleniferous soil--the importance of having good neighbors. | • this study investigated how selenium (se) affects relationships between se hyperaccumulator and nonaccumulator species, particularly how plants influence their neighbors' se accumulation and growth. • hyperaccumulators astragalus bisulcatus and stanleya pinnata and nonaccumulators astragalus drummondii and stanleya elata were cocultivated on seleniferous or nonseleniferous soil, or on gravel supplied with different selenate concentrations. the plants were analyzed for growth, se accumulation a ... | 2012 | 22269105 |
| a comparison of sulfate and selenium accumulation in relation to the expression of sulfate transporter genes in astragalus species. | sulfate and selenate uptake were investigated in both selenium (se) hyperaccumulators (astragalus racemosus and astragalus bisulcatus) and closely related nonaccumulator species (astragalus glycyphyllos and astragalus drummondii). sulfur (s) starvation increased se accumulation, whereas increased selenate supply increased sulfate accumulation in both root and shoot tissues. cdnas for homologs of groups 1 to 4 sulfate transporters were cloned from these astragalus species to investigate patterns ... | 2011 | 21972267 |
| selenium hyperaccumulators facilitate selenium-tolerant neighbors via phytoenrichment and reduced herbivory. | soil surrounding selenium (se) hyperaccumulator plants was shown earlier to be enriched in se, impairing the growth of se-sensitive plant species. because se levels in neighbors of hyperaccumulators were higher and se has been shown to protect plants from herbivory, we investigate here the potential facilitating effect of se hyperaccumulators on se-tolerant neighboring species in the field. | 2011 | 21856156 |
| selenium hyperaccumulation offers protection from cell disruptor herbivores. | hyperaccumulation, the rare capacity of certain plant species to accumulate toxic trace elements to levels several orders of magnitude higher than other species growing on the same site, is thought to be an elemental defense mechanism against herbivores and pathogens. previous research has shown that selenium (se) hyperaccumulation protects plants from a variety of herbivores and pathogens. selenium hyperaccumulating plants sequester se in discrete locations in the leaf periphery, making them po ... | 2010 | 20799959 |
| characterization of selenocysteine methyltransferases from astragalus species with contrasting selenium accumulation capacity. | a group of selenium (se)-hyperaccumulating species belonging to the genus astragalus are known for their capacity to accumulate up to 0.6% of their foliar dry weight as se, with most of this se being in the form of se-methylselenocysteine (mesecys). here, we report the isolation and molecular characterization of the gene that encodes a putative selenocysteine methyltransferase (smt) enzyme from the non-accumulator astragalus drummondii and biochemically compare it with an authentic smt enzyme fr ... | 2009 | 19309459 |
| selenium hyperaccumulation reduces plant arthropod loads in the field. | the elemental defense hypothesis proposes that some plants hyperaccumulate toxic elements as a defense mechanism. in this study the effectiveness of selenium (se) as an arthropod deterrent was investigated under field conditions. arthropod loads were measured over two growing seasons in se hyperaccumulator habitats in colorado, usa, comparing se hyperaccumulator species (astragalus bisulcatus and stanleya pinnata) with nonhyperaccumulators (camelina microcarpa, astragalus americanus, descurainia ... | 2008 | 18028291 |
| seasonal fluctuations of selenium and sulfur accumulation in selenium hyperaccumulators and related nonaccumulators. | some plants hyperaccumulate selenium (se) up to 1% of dry weight. this study was performed to obtain insight into whole-plant se fluxes in hyperaccumulators. selenium hyperaccumulators astragalus bisulcatus and stanleya pinnata were monitored over two growing seasons for seasonal fluctuations in concentrations of se and the chemically similar element sulfur (s). the related nonhyperaccumulators astragalus sericoleucus, oxytropis sericea and thlaspi montanum were included for comparison. in both ... | 2007 | 17244046 |
| overexpressing both atp sulfurylase and selenocysteine methyltransferase enhances selenium phytoremediation traits in indian mustard. | a major goal of our selenium (se) phytoremediation research is to use genetic engineering to develop fast-growing plants with an increased ability to tolerate, accumulate, and volatilize se. to this end we incorporated a gene (encoding selenocysteine methyltransferase, smt) from the se hyperaccumulator, astragalus bisulcatus, into indian mustard (leduc, d.l., tarun, a.s., montes-bayón, m., meija, j., malit, m.f., wu, c.p., abdelsamie, m., chiang, c.-y., tagmount, a., desouza, m., neuhierl, b., b ... | 2006 | 16515825 |
| imaging of selenium in plants using tapered metal monocapillary optics. | tapered metal monocapillary optics provide a potential alternative to conventional methods of producing small x-ray beams. this paper presents the initial results of chemically specific imaging using such devices. cellular resolution of organic selenium is obtained in a longitudinal section of mature astragalus bisulcatus, a selenium hyperaccumulating plant. this work demonstrates the utility of metal monocapillary optics for imaging dilute levels of target elements in biological tissues. | 2003 | 12714765 |
| chemical form and distribution of selenium and sulfur in the selenium hyperaccumulator astragalus bisulcatus. | in its natural habitat, astragalus bisulcatus can accumulate up to 0.65% (w/w) selenium (se) in its shoot dry weight. x-ray absorption spectroscopy has been used to examine the selenium biochemistry of a. bisulcatus. high concentrations of the nonprotein amino acid se-methylseleno-cysteine (cys) are present in young leaves of a. bisulcatus, but in more mature leaves, the se-methylseleno-cys concentration is lower, and selenate predominates. seleno-cys methyltransferase is the enzyme responsible ... | 2003 | 12644695 |
| quantitative, chemically specific imaging of selenium transformation in plants. | quantitative, chemically specific images of biological systems would be invaluable in unraveling the bioinorganic chemistry of biological tissues. here we report the spatial distribution and chemical forms of selenium in astragalus bisulcatus (two-grooved poison or milk vetch), a plant capable of accumulating up to 0.65% of its shoot dry biomass as se in its natural habitat. by selectively tuning incident x-ray energies close to the se k-absorption edge, we have collected quantitative, 100-micro ... | 2000 | 10984519 |
| comparative enzymology of the adenosine triphosphate sulphurylases from leaf tissue of selenium-accumulator and non-accumulator plants. | 1. atp sulphurylases were partially purified (20-40-fold) from leaf tissue of astragalus bisulcatus, astragalus racemosus (selenium-accumulator species) and astragalus hamosus and astragalus sinicus (non-accumulator species). activity was measured by sulphate-dependent pp(i)-atp exchange. the enzymes were separated from pyrophosphatase and adenosine triphosphatase activities. the properties of the astragalus atp sulphurylases were similar to the spinach enzyme. 2. the atp sulphurylases from both ... | 1974 | 4377098 |
| biosynthesis of se-methylselenocysteine and s-methylcysteine in astragalus bisulcatus. | | 1970 | 5475881 |
| seleno-amino acid found in astragalus bisulcatus. | ion-exchange and filter-paper columns were used in a separation of amino acids from an extract of astragalus bisulcatus. two amino acids were identified, s-methylcysteine and se-methylselenocysteine. | 1960 | 13839255 |