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Sample records for mediate directional pollen

  1. Direct and reverse pollen-mediated gene flow between GM rice and red rice weed

    PubMed Central

    Serrat, X.; Esteban, R.; Peñas, G.; Català, M. M.; Melé, E.; Messeguer, J.

    2013-01-01

    Potential risks of genetically modified (GM) crops must be identified before their commercialization, as happens with all new technologies. One of the major concerns is the proper risk assessment of adventitious presence of transgenic material in rice fields due to cross-pollination. Several studies have been conducted in order to quantify pollen-mediated gene flow from transgenic rice (Oryza sativa) to both conventional rice and red rice weed (O. sativa f. spontanea) under field conditions. Some of these studies reported GM pollen-donor rice transferring GM traits to red rice. However, gene flow also occurs in the opposite direction, in a phenomenon that we have called reverse gene flow, resulting in transgenic seeds that have incorporated the traits of wild red rice. We quantified reverse gene flow using material from two field trials. A molecular analysis based on amplified fragment length polymorphisms was carried out, being complemented with a phenotypic identification of red rice traits. In both field trials, the reverse gene flow detected was greater than the direct gene flow. The rate of direct gene flow varied according to the relative proportions of the donor (GM rice) and receptor (red rice) plants and was influenced by wind direction. The ecological impact of reverse gene flow is limited in comparison with that of direct gene flow because non-shattered and non-dormant seeds would be obtained in the first generation. Hybrid seed would remain in the spike and therefore most of it would be removed during harvesting. Nevertheless, this phenomenon must be considered in fields used for elite seed production and in developing countries where farmers often keep some seed for planting the following year. In these cases, there is a higher risk of GM red rice weed infestation increasing from year to year and therefore a proper monitoring plan needs to be established.

  2. Aridopsis COBRA-LIKE 10, a GPI-anchored protien, mediates directional growth of pollen tubes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Successful reproduction of flowering plants requires constant communication between female tissues and growing pollen tubes. Female cells secrete molecules and peptides as nutrients or guidance cues for fast and directional tube growth, which is executed by dynamic changes of intracellular activitie...

  3. Plant transformation via pollen tube-mediated gene transfer

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Genetic transformation using foreign genes and the subsequent development of transgenic plants has been employed to develop enhanced elite germplasm. Although some skepticism exits regarding pollen tube-mediated gene transfer (PTT), reports demonstrating improved transformation efficiency with PTT ...

  4. Arabidopsis thaliana CML25 mediates the Ca(2+) regulation of K(+) transmembrane trafficking during pollen germination and tube elongation.

    PubMed

    Wang, Shuang-Shuang; Diao, Wen-Zhu; Yang, Xue; Qiao, Zhu; Wang, Mei; Acharya, Biswa R; Zhang, Wei

    2015-11-01

    The concentration alteration of cytosolic-free calcium ([Ca(2+) ]cyt ) is a well-known secondary messenger in plants and plays important roles during pollen grain germination and tube elongation. Here we demonstrate that CML25, a member of calmodulin-like proteins, has Ca(2+) -binding activity and plays a role in pollen grain germination, tube elongation and seed setting. CML25 transcript was abundant in mature pollen grains and pollen tubes, and its product CML25 protein was primarily directed to the cytoplasm. Two independent CML25 loss-of-function T-DNA insertion mutants suffered a major reduction in both the rate of pollen germination and the elongation of the pollen tube. Also, pollen grains of cml25 mutants were less sensitive to the external K(+) and Ca(2+) concentration than wild-type pollen. The disruption of CML25 increased the [Ca(2+) ]cyt in both the pollen grain and the pollen tube, which in turn impaired the Ca(2+) -dependent inhibition of whole-cell inward K(+) currents in protoplasts prepared from these materials (pollen grain and pollen tube). Complementation of cml25-1 mutant resulted in the recovery of wild-type phenotype. Our findings indicate that CML25 is an important transducer in the Ca(2+) -mediated regulation of K(+) influx during pollen germination and tube elongation. PMID:25923414

  5. Influence of wind direction on pollen concentration in the atmosphere

    NASA Astrophysics Data System (ADS)

    Silva Palacios, I.; Tormo Molina, R.; Muñoz Rodríguez, A. F.

    The daily pollen concentration in the atmosphere of Badajoz (SW Spain) was analysed over a 6-year period (1993-1998) using a volumetric aerobiological trap. The results for the main pollination period are compared with the number of hours of wind each day in the four quadrants: 1 (NE), 2 (SE), 3 (SW) and 4 (NW). The pollen source distribution allowed 16 pollen types to be analysed as a function of their distribution in the four quadrants with respect to the location of the trap. Four of them correspond to species growing in an irrigated farmland environment (Amaranthaceae-Chenopodiaceae, Plantago, Scirpus, and Typha), five to riparian and woodland species (Salix, Fraxinus, Alnus, Populus, and Eucalyptus), four to urban ornamentals (Ulmus, Arecaceae, Cupressaceae, and Casuarina), and three which include the most frequent pollen grains of widely distributed species (Poaceae, Quercus, and Olea). The results show that the distribution of the sources and the wind direction play a very major role in determining the pollen concentration in the atmosphere when these sources are located in certain quadrants, and that the widely distributed pollen sources show no relationship with wind direction. In some years the values of the correlations were not maintained, which leads one to presume that, in order to draw significant conclusions and establish clear patterns of the influence of wind direction, a continuous and more prolonged study will be required.

  6. Control of Pollen-Mediated Gene Flow in Transgenic Trees[W][OA

    PubMed Central

    Zhang, Chunsheng; Norris-Caneda, Kim H.; Rottmann, William H.; Gulledge, Jon E.; Chang, Shujun; Kwan, Brian Yow-Hui; Thomas, Anita M.; Mandel, Lydia C.; Kothera, Ronald T.; Victor, Aditi D.; Pearson, Leslie; Hinchee, Maud A.W.

    2012-01-01

    Pollen elimination provides an effective containment method to reduce direct gene flow from transgenic trees to their wild relatives. Until now, only limited success has been achieved in controlling pollen production in trees. A pine (Pinus radiata) male cone-specific promoter, PrMC2, was used to drive modified barnase coding sequences (barnaseH102E, barnaseK27A, and barnaseE73G) in order to determine their effectiveness in pollen ablation. The expression cassette PrMC2-barnaseH102E was found to efficiently ablate pollen in tobacco (Nicotiana tabacum), pine, and Eucalyptus (spp.). Large-scale and multiple-year field tests demonstrated that complete prevention of pollen production was achieved in greater than 95% of independently transformed lines of pine and Eucalyptus (spp.) that contained the PrMC2-barnaseH102E expression cassette. A complete pollen control phenotype was achieved in transgenic lines and expressed stably over multiple years, multiple test locations, and when the PrMC2-barnaseH102E cassette was flanked by different genes. The PrMC2-barnaseH102E transgenic pine and Eucalyptus (spp.) trees grew similarly to control trees in all observed attributes except the pollenless phenotype. The ability to achieve the complete control of pollen production in field-grown trees is likely the result of a unique combination of three factors: the male cone/anther specificity of the PrMC2 promoter, the reduced RNase activity of barnaseH102E, and unique features associated with a polyploid tapetum. The field performance of the PrMC2-barnaseH102E in representative angiosperm and gymnosperm trees indicates that this gene can be used to mitigate pollen-mediated gene flow associated with large-scale deployment of transgenic trees. PMID:22723085

  7. The Pollen Receptor Kinase LePRK2 Mediates Growth-Promoting Signals and Positively Regulates Pollen Germination and Tube Growth

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In flowering plants, the process of pollen germination and tube growth is required for successful fertilization. A pollen receptor kinase from tomato, LePRK2, has been implicated in signaling during pollen germination and tube growth as well as in mediating pollen (tube)-pistil communication. Here w...

  8. Pollen-Mediated Movement of Herbicide Resistance Genes in Lolium rigidum

    PubMed Central

    Loureiro, Iñigo; Escorial, María-Concepción; Chueca, María-Cristina

    2016-01-01

    The transfer of herbicide resistance genes by pollen is a major concern in cross-pollinated species such as annual ryegrass (Lolium rigidum). A two-year study was conducted in the greenhouse, under favorable conditions for pollination, to generate information on potential maximum cross-pollination. This maximum cross-pollination rate was 56.1%. A three-year field trial was also conducted to study the cross-pollination rates in terms of distance and orientation to an herbicide-resistant pollen source. Under field conditions, cross-pollination rates varied from 5.5% to 11.6% in plants adjacent to the pollen source and decreased with increasing distances (1.5 to 8.9% at 15 m distance and up to 4.1% at 25 m in the downwind direction). Environmental conditions influenced the cross-pollination both under greenhouse and field conditions. Data were fit to an exponential decay model to predict gene flow at increasing distances. This model predicted an average gene flow of 7.1% when the pollen donor and recipient plants were at 0 m distance from each other. Pollen-mediated gene flow declined by 50% at 16.7 m from the pollen source, yet under downwind conditions gene flow of 5.2% was predicted at 25 m, the farthest distance studied. Knowledge of cross-pollination rates will be useful for assessing the spread of herbicide resistance genes in L. rigidum and in developing appropriate strategies for its mitigation. PMID:27336441

  9. Floral traits mediate the vulnerability of aloes to pollen theft and inefficient pollination by bees

    PubMed Central

    Hargreaves, Anna L.; Harder, Lawrence D.; Johnson, Steven D.

    2012-01-01

    Background and Aims Pollen-collecting bees are among the most important pollinators globally, but are also the most common pollen thieves and can significantly reduce plant reproduction. The pollination efficiency of pollen collectors depends on the frequency of their visits to female(-phase) flowers, contact with stigmas and deposition of pollen of sufficient quantity and quality to fertilize ovules. Here we investigate the relative importance of these components, and the hypothesis that floral and inflorescence characteristics mediate the pollination role of pollen collection by bees. Methods For ten Aloe species that differ extensively in floral and inflorescence traits, we experimentally excluded potential bird pollinators to quantify the contributions of insect visitors to pollen removal, pollen deposition and seed production. We measured corolla width and depth to determine nectar accessibility, and the phenology of anther dehiscence and stigma receptivity to quantify herkogamy and dichogamy. Further, we compiled all published bird-exclusion studies of aloes, and compared insect pollination success with floral morphology. Key Results Species varied from exclusively insect pollinated, to exclusively bird pollinated but subject to extensive pollen theft by insects. Nectar inaccessibility and strong dichogamy inhibited pollination by pollen-collecting bees by discouraging visits to female-phase (i.e. pollenless) flowers. For species with large inflorescences of pollen-rich flowers, pollen collectors successfully deposited pollen, but of such low quality (probably self-pollen) that they made almost no contribution to seed set. Indeed, considering all published bird-exclusion studies (17 species in total), insect pollination efficiency varied significantly with floral shape. Conclusions Species-specific floral and inflorescence characteristics, especially nectar accessibility and dichogamy, control the efficiency of pollen-collecting bees as pollinators of aloes

  10. Reactive oxygen species mediate pollen tube rupture to release sperm for fertilization in Arabidopsis

    NASA Astrophysics Data System (ADS)

    Duan, Qiaohong; Kita, Daniel; Johnson, Eric A.; Aggarwal, Mini; Gates, Laura; Wu, Hen-Ming; Cheung, Alice Y.

    2014-01-01

    In flowering plants, sperm are transported inside pollen tubes to the female gametophyte for fertilization. The female gametophyte induces rupture of the penetrating pollen tube, resulting in sperm release and rendering them available for fertilization. Here we utilize the Arabidopsis FERONIA (FER) receptor kinase mutants, whose female gametophytes fail to induce pollen tube rupture, to decipher the molecular mechanism of this critical male-female interactive step. We show that FER controls the production of high levels of reactive oxygen species at the entrance to the female gametophyte to induce pollen tube rupture and sperm release. Pollen tube growth assays in vitro and in the pistil demonstrate that hydroxyl free radicals are likely the most reactive oxygen molecules, and they induce pollen tube rupture in a Ca2+-dependent process involving Ca2+ channel activation. Our results provide evidence for a RHO GTPase-based signalling mechanism to mediate sperm release for fertilization in plants.

  11. Effect of land uses and wind direction on the contribution of local sources to airborne pollen.

    PubMed

    Rojo, Jesús; Rapp, Ana; Lara, Beatriz; Fernández-González, Federico; Pérez-Badia, Rosa

    2015-12-15

    The interpretation of airborne pollen levels in cities based on the contribution of the surrounding flora and vegetation is a useful tool to estimate airborne allergen concentrations and, consequently, to determine the allergy risk for local residents. This study examined the pollen spectrum in a city in central Spain (Guadalajara) and analysed the vegetation landscape and land uses within a radius of 20km in an attempt to identify and locate the origin of airborne pollen and to determine the effect of meteorological variables on pollen emission and dispersal. The results showed that local wind direction was largely responsible for changes in the concentrations of different airborne pollen types. The land uses contributing most to airborne pollen counts were urban green spaces, though only 0.1% of the total surface area studied, and broadleaved forest which covered 5% of the study area. These two types of land use together accounted for 70% of the airborne pollen. Crops, scrubland and pastureland, though covering 80% of the total surface area, contributed only 18.6% to the total pollen count, and this contribution mainly consisted of pollen from Olea and herbaceous plants, including Poaceae, Urticaceae and Chenopodiaceae-Amaranthaceae. Pollen from ornamental species were mainly associated with easterly (Platanus), southerly (Cupressaceae) and westerly (Cupressaceae and Platanus) winds from the areas where the city's largest parks and gardens are located. Quercus pollen was mostly transported by winds blowing in from holm-oak stands on the eastern edge of the city. The highest Populus pollen counts were associated with easterly and westerly winds blowing in from areas containing rivers and streams. The airborne pollen counts generally rose with increasing temperature, solar radiation and hours of sunlight, all of which favour pollen release. In contrast, pollen counts declined with increased relative humidity and rainfall, which hinder airborne pollen transport

  12. Modelling pollen-mediated gene flow in rice: risk assessment and management of transgene escape.

    PubMed

    Rong, Jun; Song, Zhiping; de Jong, Tom J; Zhang, Xinsheng; Sun, Shuguang; Xu, Xian; Xia, Hui; Liu, Bo; Lu, Bao-Rong

    2010-05-01

    Fast development and commercialization of genetically modified plants have aroused concerns of transgene escape and its environmental consequences. A model that can effectively predict pollen-mediated gene flow (PMGF) is essential for assessing and managing risks from transgene escape. A pollen-trap method was used to measure the wind-borne pollen dispersal in cultivated rice and common wild rice, and effects of relative humidity, temperature and wind speed on pollen dispersal were estimated. A PMGF model was constructed based on the pollen dispersal pattern in rice, taking outcrossing rates of recipients and cross-compatibility between rice and its wild relatives into consideration. Published rice gene flow data were used to validate the model. Pollen density decreased in a simple exponential pattern with distances to the rice field. High relative humidity reduced pollen dispersal distances. Model simulation showed an increased PMGF frequency with the increase of pollen source size (the area of a rice field), but this effect levelled off with a large pollen-source size. Cross-compatibility is essential when modelling PMGF from rice to its wild relatives. The model fits the data well, including PMGF from rice to its wild relatives. Therefore, it can be used to predict PMGF in rice under diverse conditions (e.g. different outcrossing rates and cross-compatibilities), facilitating the determination of isolation distances to minimize transgene escape. The PMGF model may be extended to other wind-pollinated plant species such as wheat and barley. PMID:20132516

  13. Wind-mediated horseweed (Conyza canadensis) gene flow: pollen emission, dispersion, and deposition

    PubMed Central

    Huang, Haiyan; Ye, Rongjian; Qi, Meilan; Li, Xiangzhen; Miller, David R; Stewart, Charles Neal; DuBois, David W; Wang, Junming

    2015-01-01

    Abstract Horseweed (Conyza canadensis) is a problem weed in crop production because of its evolved resistance to glyphosate and other herbicides. Although horseweed is mainly self-pollinating, glyphosate-resistant (GR) horseweed can pollinate glyphosate-susceptible (GS) horseweed. To the best of our knowledge, however, there are no available data on horseweed pollen production, dispersion, and deposition relative to gene flow and the evolution of resistance. To help fill this knowledge gap, a 43-day field study was performed in Champaign, Illinois, USA in 2013 to characterize horseweed atmospheric pollen emission, dispersion, and deposition. Pollen concentration and deposition, coupled with atmospheric data, were measured in a source field (180 m by 46 m) and its surrounding areas up to 1 km downwind horizontally and up to 100 m vertically. The source strength (emission rate) ranged from 0 to 140 pollen grains per plant per second (1170 to 2.1×106 per plant per day). For the life of the study, the estimated number of pollen grains generated from this source field was 10.5×1010 (2.3×106 per plant). The release of horseweed pollen was not strongly correlated to meteorological data and may be mainly determined by horseweed physiology. Horseweed pollen reached heights of 80 to100 m, making long-distance transport possible. Normalized (by source data) pollen deposition with distance followed a negative-power exponential curve. Normalized pollen deposition was 2.5% even at 480 m downwind from the source edge. Correlation analysis showed that close to or inside the source field at lower heights (≤3 m) vertical transport was related to vertical wind speed, while horizontal pollen transport was related to horizontal wind speed. High relative humidity prevented pollen transport at greater heights (3–100 m) and longer distances (0–1000 m) from the source. This study can contribute to the understanding of how herbicide-resistance weeds or invasive plants affect

  14. Wind-mediated horseweed (Conyza canadensis) gene flow: pollen emission, dispersion, and deposition.

    PubMed

    Huang, Haiyan; Ye, Rongjian; Qi, Meilan; Li, Xiangzhen; Miller, David R; Stewart, Charles Neal; DuBois, David W; Wang, Junming

    2015-07-01

    Horseweed (Conyza canadensis) is a problem weed in crop production because of its evolved resistance to glyphosate and other herbicides. Although horseweed is mainly self-pollinating, glyphosate-resistant (GR) horseweed can pollinate glyphosate-susceptible (GS) horseweed. To the best of our knowledge, however, there are no available data on horseweed pollen production, dispersion, and deposition relative to gene flow and the evolution of resistance. To help fill this knowledge gap, a 43-day field study was performed in Champaign, Illinois, USA in 2013 to characterize horseweed atmospheric pollen emission, dispersion, and deposition. Pollen concentration and deposition, coupled with atmospheric data, were measured in a source field (180 m by 46 m) and its surrounding areas up to 1 km downwind horizontally and up to 100 m vertically. The source strength (emission rate) ranged from 0 to 140 pollen grains per plant per second (1170 to 2.1×10(6) per plant per day). For the life of the study, the estimated number of pollen grains generated from this source field was 10.5×10(10) (2.3×10(6) per plant). The release of horseweed pollen was not strongly correlated to meteorological data and may be mainly determined by horseweed physiology. Horseweed pollen reached heights of 80 to100 m, making long-distance transport possible. Normalized (by source data) pollen deposition with distance followed a negative-power exponential curve. Normalized pollen deposition was 2.5% even at 480 m downwind from the source edge. Correlation analysis showed that close to or inside the source field at lower heights (≤3 m) vertical transport was related to vertical wind speed, while horizontal pollen transport was related to horizontal wind speed. High relative humidity prevented pollen transport at greater heights (3-100 m) and longer distances (0-1000 m) from the source. This study can contribute to the understanding of how herbicide-resistance weeds or invasive plants affect ecology

  15. Pollen-mediated gene flow in flax (Linum usitatissimum L.): can genetically engineered and organic flax coexist?

    PubMed

    Jhala, A J; Bhatt, H; Topinka, K; Hall, L M

    2011-04-01

    Coexistence allows growers and consumers the choice of producing or purchasing conventional or organic crops with known standards for adventitious presence of genetically engineered (GE) seed. Flax (Linum usitatissimum L.) is multipurpose oilseed crop in which product diversity and utility could be enhanced for industrial, nutraceutical and pharmaceutical markets through genetic engineering. If GE flax were released commercially, pollen-mediated gene flow will determine in part whether GE flax could coexist without compromising other markets. As a part of pre-commercialization risk assessment, we quantified pollen-mediated gene flow between two cultivars of flax. Field experiments were conducted at four locations during 2006 and 2007 in western Canada using a concentric donor (20 × 20 m) receptor (120 × 120 m) design. Gene flow was detected through the xenia effect of dominant alleles of high α-linolenic acid (ALA; 18:3(cisΔ9,12,15)) to the low ALA trait. Seeds were harvested from the pollen recipient plots up to a distance of 50 m in eight directions from the pollen donor. High ALA seeds were identified using a thiobarbituric acid test and served as a marker for gene flow. Binomial distribution and power analysis were used to predict the minimum number of seeds statistically required to detect the frequency of gene flow at specific α (confidence interval) and power (1-β) values. As a result of the low frequency of gene flow, approximately 4 million seeds were screened to derive accurate quantification. Frequency of gene flow was highest near the source: averaging 0.0185 at 0.1 m but declined rapidly with distance, 0.0013 and 0.00003 at 3 and 35 m, respectively. Gene flow was reduced to 50% (O₅₀) and 90% (O₉₀) between 0.85 to 2.64 m, and 5.68 to 17.56 m, respectively. No gene flow was detected at any site or year > 35 m distance from the pollen source, suggesting that frequency of gene flow was ≤ 0.00003 (P = 0.95). Although it is not possible to

  16. Pollen-mediated gene flow in flax (Linum usitatissimum L.): can genetically engineered and organic flax coexist?

    PubMed Central

    Jhala, A J; Bhatt, H; Topinka, K; Hall, L M

    2011-01-01

    Coexistence allows growers and consumers the choice of producing or purchasing conventional or organic crops with known standards for adventitious presence of genetically engineered (GE) seed. Flax (Linum usitatissimum L.) is multipurpose oilseed crop in which product diversity and utility could be enhanced for industrial, nutraceutical and pharmaceutical markets through genetic engineering. If GE flax were released commercially, pollen-mediated gene flow will determine in part whether GE flax could coexist without compromising other markets. As a part of pre-commercialization risk assessment, we quantified pollen-mediated gene flow between two cultivars of flax. Field experiments were conducted at four locations during 2006 and 2007 in western Canada using a concentric donor (20 × 20 m) receptor (120 × 120 m) design. Gene flow was detected through the xenia effect of dominant alleles of high α-linolenic acid (ALA; 18:3cisΔ9,12,15) to the low ALA trait. Seeds were harvested from the pollen recipient plots up to a distance of 50 m in eight directions from the pollen donor. High ALA seeds were identified using a thiobarbituric acid test and served as a marker for gene flow. Binomial distribution and power analysis were used to predict the minimum number of seeds statistically required to detect the frequency of gene flow at specific α (confidence interval) and power (1−β) values. As a result of the low frequency of gene flow, approximately 4 million seeds were screened to derive accurate quantification. Frequency of gene flow was highest near the source: averaging 0.0185 at 0.1 m but declined rapidly with distance, 0.0013 and 0.00003 at 3 and 35 m, respectively. Gene flow was reduced to 50% (O50) and 90% (O90) between 0.85 to 2.64 m, and 5.68 to 17.56 m, respectively. No gene flow was detected at any site or year >35 m distance from the pollen source, suggesting that frequency of gene flow was ⩽0.00003 (P=0.95). Although it is not possible

  17. Pollen- and Seed-Mediated Transgene Flow in Commercial Cotton Seed Production Fields

    PubMed Central

    Heuberger, Shannon; Ellers-Kirk, Christa; Tabashnik, Bruce E.; Carrière, Yves

    2010-01-01

    Background Characterizing the spatial patterns of gene flow from transgenic crops is challenging, making it difficult to design containment strategies for markets that regulate the adventitious presence of transgenes. Insecticidal Bacillus thuringiensis (Bt) cotton is planted on millions of hectares annually and is a potential source of transgene flow. Methodology/Principal Findings Here we monitored 15 non-Bt cotton (Gossypium hirsutum, L.) seed production fields (some transgenic for herbicide resistance, some not) for gene flow of the Bt cotton cry1Ac transgene. We investigated seed-mediated gene flow, which yields adventitious Bt cotton plants, and pollen-mediated gene flow, which generates outcrossed seeds. A spatially-explicit statistical analysis was used to quantify the effects of nearby Bt and non-Bt cotton fields at various spatial scales, along with the effects of pollinator abundance and adventitious Bt plants in fields, on pollen-mediated gene flow. Adventitious Bt cotton plants, resulting from seed bags and planting error, comprised over 15% of plants sampled from the edges of three seed production fields. In contrast, pollen-mediated gene flow affected less than 1% of the seed sampled from field edges. Variation in outcrossing was better explained by the area of Bt cotton fields within 750 m of the seed production fields than by the area of Bt cotton within larger or smaller spatial scales. Variation in outcrossing was also positively associated with the abundance of honey bees. Conclusions/Significance A comparison of statistical methods showed that our spatially-explicit analysis was more powerful for understanding the effects of surrounding fields than customary models based on distance. Given the low rates of pollen-mediated gene flow observed in this study, we conclude that careful planting and screening of seeds could be more important than field spacing for limiting gene flow. PMID:21152426

  18. ABCG26-mediated polyketide trafficking and hydroxycinnamoyl spermidines contribute to pollen wall exine formation in Arabidopsis.

    PubMed

    Quilichini, Teagen D; Samuels, A Lacey; Douglas, Carl J

    2014-11-01

    Pollen grains are encased by a multilayered, multifunctional wall. The sporopollenin and pollen coat constituents of the outer pollen wall (exine) are contributed by surrounding sporophytic tapetal cells. Because the biosynthesis and development of the exine occurs in the innermost cell layers of the anther, direct observations of this process are difficult. The objective of this study was to investigate the transport and assembly of exine components from tapetal cells to microspores in the intact anthers of Arabidopsis thaliana. Intrinsically fluorescent components of developing tapetum and microspores were imaged in intact, live anthers using two-photon microscopy. Mutants of ABCG26, which encodes an ATP binding cassette transporter required for exine formation, accumulated large fluorescent vacuoles in tapetal cells, with corresponding loss of fluorescence on microspores. These vacuolar inclusions were not observed in tapetal cells of double mutants of abcg26 and genes encoding the proposed sporopollenin polyketide biosynthetic metabolon (ACYL COENZYME A SYNTHETASE5, POLYKETIDE SYNTHASE A [PKSA], PKSB, and TETRAKETIDE α-PYRONE REDUCTASE1), providing a genetic link between transport by ABCG26 and polyketide biosynthesis. Genetic analysis also showed that hydroxycinnamoyl spermidines, known components of the pollen coat, were exported from tapeta prior to programmed cell death in the absence of polyketides, raising the possibility that they are incorporated into the exine prior to pollen coat deposition. We propose a model where ABCG26-exported polyketides traffic from tapetal cells to form the sporopollenin backbone, in coordination with the trafficking of additional constituents, prior to tapetum programmed cell death. PMID:25415974

  19. The Arabidopsis KINβγ Subunit of the SnRK1 Complex Regulates Pollen Hydration on the Stigma by Mediating the Level of Reactive Oxygen Species in Pollen.

    PubMed

    Gao, Xin-Qi; Liu, Chang Zhen; Li, Dan Dan; Zhao, Ting Ting; Li, Fei; Jia, Xiao Na; Zhao, Xin-Ying; Zhang, Xian Sheng

    2016-07-01

    Pollen-stigma interactions are essential for pollen germination. The highly regulated process of pollen germination includes pollen adhesion, hydration, and germination on the stigma. However, the internal signaling of pollen that regulates pollen-stigma interactions is poorly understood. KINβγ is a plant-specific subunit of the SNF1-related protein kinase 1 complex which plays important roles in the regulation of plant development. Here, we showed that KINβγ was a cytoplasm- and nucleus-localized protein in the vegetative cells of pollen grains in Arabidopsis. The pollen of the Arabidopsis kinβγ mutant could not germinate on stigma, although it germinated normally in vitro. Further analysis revealed the hydration of kinβγ mutant pollen on the stigma was compromised. However, adding water to the stigma promoted the germination of the mutant pollen in vivo, suggesting that the compromised hydration of the mutant pollen led to its defective germination. In kinβγ mutant pollen, the structure of the mitochondria and peroxisomes was destroyed, and their numbers were significantly reduced compared with those in the wild type. Furthermore, we found that the kinβγ mutant exhibited reduced levels of reactive oxygen species (ROS) in pollen. The addition of H2O2 in vitro partially compensated for the reduced water absorption of the mutant pollen, and reducing ROS levels in pollen by overexpressing Arabidopsis CATALASE 3 resulted in compromised hydration of pollen on the stigma. These results indicate that Arabidopsis KINβγ is critical for the regulation of ROS levels by mediating the biogenesis of mitochondria and peroxisomes in pollen, which is required for pollen-stigma interactions during pollination. PMID:27472382

  20. TURAN and EVAN Mediate Pollen Tube Reception in Arabidopsis Synergids through Protein Glycosylation

    PubMed Central

    Lindner, Heike; Shimosato-Asano, Hiroko; Boisson-Dernier, Aurélien; Grossniklaus, Ueli

    2015-01-01

    Pollen tube (PT) reception in flowering plants describes the crosstalk between the male and female gametophytes upon PT arrival at the synergid cells of the ovule. It leads to PT growth arrest, rupture, and sperm cell release, and is thus essential to ensure double fertilization. Here, we describe TURAN (TUN) and EVAN (EVN), two novel members of the PT reception pathway that is mediated by the FERONIA (FER) receptor-like kinase (RLK). Like fer, mutations in these two genes lead to PT overgrowth inside the female gametophyte (FG) without PT rupture. Mapping by next-generation sequencing, cytological analysis of reporter genes, and biochemical assays of glycoproteins in RNAi knockdown mutants revealed both genes to be involved in protein N-glycosylation in the endoplasmic reticulum (ER). TUN encodes a uridine diphosphate (UDP)-glycosyltransferase superfamily protein and EVN a dolichol kinase. In addition to their common role during PT reception in the synergids, both genes have distinct functions in the pollen: whereas EVN is essential for pollen development, TUN is required for PT growth and integrity by affecting the stability of the pollen-specific FER homologs ANXUR1 (ANX1) and ANX2. ANX1- and ANX2-YFP reporters are not expressed in tun pollen grains, but ANX1-YFP is degraded via the ER-associated degradation (ERAD) pathway, likely underlying the anx1/2-like premature PT rupture phenotype of tun mutants. Thus, as in animal sperm–egg interactions, protein glycosylation is essential for the interaction between the female and male gametophytes during PT reception to ensure fertilization and successful reproduction. PMID:25919390

  1. Contemporary pollen-mediated gene immigration reflects the historical isolation of a rare, animal-pollinated shrub in a fragmented landscape.

    PubMed

    Sampson, J F; Byrne, M; Yates, C J; Gibson, N; Thavornkanlapachai, R; Stankowski, S; MacDonald, B; Bennett, I

    2014-02-01

    Fragmentation is generally considered to have negative impacts on widespread outbreeders but impacts on gene flow and diversity in patchy, naturally rare, self-compatible plant species remain unclear. We investigated diversity, gene flow and contemporary pollen-mediated gene immigration in the rare, narrowly distributed endemic shrub Calothamnus quadrifidus ssp. teretifolius. This taxon occurs in an internationally recognized biodiversity hotspot subjected to recent human-induced fragmentation and the condition of the remnants ranges from intact to highly degraded. Using microsatellites, we found that inbreeding, historically low gene flow and significant population differentiation have characterized the genetic system of C. quadrifidus ssp. teretifolius. Inbreeding arises from self-pollination, a small amount of biparental inbreeding and significant correlation of outcross paternity but fecundity was high suggesting populations might have purged their lethals. Paternity analyses show that pollinators can move pollen over degraded and intact habitat but populations in both intact and degraded remnants had few pollen parents per seed parent and low pollen immigration. Genetic diversity did not differ significantly between intact and degraded remnants but there were signs of genetic bottlenecks and reduced diversity in some degraded remnants. Overall, our study suggests human-induced fragmentation has not significantly changed the mating system, or pollen immigration to, remnant populations and therefore genetic connectivity need not be the highest conservation priority. Rather, for rare species adapted to higher levels of inbreeding, conservation efforts may be best directed to managing intact habitats and ecosystem processes. PMID:24065181

  2. Contemporary pollen-mediated gene immigration reflects the historical isolation of a rare, animal-pollinated shrub in a fragmented landscape

    PubMed Central

    Sampson, J F; Byrne, M; Yates, C J; Gibson, N; Thavornkanlapachai, R; Stankowski, S; MacDonald, B; Bennett, I

    2014-01-01

    Fragmentation is generally considered to have negative impacts on widespread outbreeders but impacts on gene flow and diversity in patchy, naturally rare, self-compatible plant species remain unclear. We investigated diversity, gene flow and contemporary pollen-mediated gene immigration in the rare, narrowly distributed endemic shrub Calothamnus quadrifidus ssp. teretifolius. This taxon occurs in an internationally recognized biodiversity hotspot subjected to recent human-induced fragmentation and the condition of the remnants ranges from intact to highly degraded. Using microsatellites, we found that inbreeding, historically low gene flow and significant population differentiation have characterized the genetic system of C. quadrifidus ssp. teretifolius. Inbreeding arises from self-pollination, a small amount of biparental inbreeding and significant correlation of outcross paternity but fecundity was high suggesting populations might have purged their lethals. Paternity analyses show that pollinators can move pollen over degraded and intact habitat but populations in both intact and degraded remnants had few pollen parents per seed parent and low pollen immigration. Genetic diversity did not differ significantly between intact and degraded remnants but there were signs of genetic bottlenecks and reduced diversity in some degraded remnants. Overall, our study suggests human-induced fragmentation has not significantly changed the mating system, or pollen immigration to, remnant populations and therefore genetic connectivity need not be the highest conservation priority. Rather, for rare species adapted to higher levels of inbreeding, conservation efforts may be best directed to managing intact habitats and ecosystem processes. PMID:24065181

  3. Pollen-mediated movement of herbicide resistance between commercial canola fields.

    PubMed

    Rieger, Mary A; Lamond, Michael; Preston, Christopher; Powles, Stephen B; Roush, Richard T

    2002-06-28

    There is considerable public and scientific debate for and against genetically modified (GM) crops. One of the first GM crops, Brassica napus (oilseed rape or canola) is now widely grown in North America, with proposed commercial release into Australia and Europe. Among concerns of opponents to these crops are claims that pollen movement will cause unacceptable levels of gene flow from GM to non-GM crops or to related weedy species, resulting in genetic pollution of the environment. Therefore, quantifying pollen-mediated gene flow is vital for assessing the environmental impact of GM crops. This study quantifies at a landscape level the gene flow that occurs from herbicide-resistant canola crops to nearby crops not containing herbicide resistance genes. PMID:12089441

  4. Immunoglobulin E (IgE)-mediated cross-reactivity between mesquite pollen proteins and lima bean, an edible legume

    PubMed Central

    Dhyani, A; Arora, N; Jain, V K; Sridhara, S; Singh, B P

    2007-01-01

    Immunoglobulin E (IgE)-mediated food allergy often develops as a consequence of allergic sensitization to pollen proteins. Mesquite (Prosopis juliflora) tree pollen is reported to be cross-reactive with other pollen species, but little has been reported on its cross-reactivity with plant-derived foods belonging to the same/different families. The present study investigates the in vitro cross-reactivity of mesquite pollen and lima bean (Phaseolus lunatus), an edible seed belonging to the Leguminosae family. Of 110 patients (asthma, rhinitis or both) tested intradermally, 20 showed marked positive reactions with Prosopis pollen extract. Of these, 12 patients showed elevated specific IgE to Prosopis pollen extract alone and four to both Phaseolus and pollen extract. In vitro cross-reactivity was investigated using inhibition assays [enzyme-linked immunosorbent assay (ELISA) inhibition, immunoblot inhibition], histamine release and lymphoproliferation. P. lunatus extract could inhibit IgE binding to P. juliflora in a dose-dependent manner, requiring 400 ng of protein for 50% inhibition in ELISA assay. Immunoblot and immunoblot inhibition demonstrated the presence of 20, 26, 35, 66 and 72 kDa as shared IgE binding components between the two extracts. Histamine release, peripheral blood mononuclear cells proliferation and interleukin (IL)-4 levels also suggested allergenic cross-reactivity. In conclusion, there is humoral and cellular cross-reactivity between Prosopis pollen and Phaseolus seed allergens. PMID:17614972

  5. Bee Pollen

    MedlinePlus

    ... Don’t confuse bee pollen with bee venom, honey, or royal jelly. People take bee pollen for ... Pollen, Extrait de Pollen d’Abeille, Honeybee Pollen, Honey Bee Pollen, Maize Pollen, Pine Pollen, Polen de ...

  6. The pollen-specific R-SNARE/longin PiVAMP726 mediates fusion of endo- and exocytic compartments in pollen tube tip growth.

    PubMed

    Guo, Feng; McCubbin, Andrew G

    2012-05-01

    The growing pollen tube apex is dedicated to balancing exo- and endocytic processes to form a rapidly extending tube. As perturbation of either tends to cause a morphological phenotype, this system provides tractable model for studying these processes. Vesicle-associated membrane protein 7s (VAMP7s) are members of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) family that mediate cognate membrane fusion but their role in pollen tube growth has not been investigated. This manuscript identifies PiVAMP726 of Petunia inflata as a pollen-specific VAMP7 that localizes to the inverted cone of transport vesicles at the pollen tube tip. The endocytic marker FM4-64 was found to colocalize with yellow fluorescent protein (YFP)-PiVAMP726, which is consistent with PiVAMP726 containing an amino-acid motif implicated in endosomal localization, At high overexpression levels, YFP- PiVAMP726 inhibited growth and caused the formation of novel membrane compartments within the pollen tube tip. Functional dissection of PiVAMP726 implicated the N-terminal longin domain in negative regulation of the SNARE activity, but not localization of PiVAMP726. Expression of the constitutively active C-terminal SNARE domain alone, in pollen tubes, generated similar phenotypes to the full-length protein, but the truncated domain was more potent than the wild-type protein at both inhibiting growth and forming the novel membrane compartments. Both endo- and exocytic markers localized to these compartments in addition to YFP-PiVAMP726, leading to the speculation that PiVAMP726 might be involved in the recycling of endocytic vesicles in tip growth. PMID:22345643

  7. The Arabidopsis KINβγ Subunit of the SnRK1 Complex Regulates Pollen Hydration on the Stigma by Mediating the Level of Reactive Oxygen Species in Pollen

    PubMed Central

    Zhao, Ting Ting; Li, Fei; Jia, Xiao Na; Zhao, Xin-Ying; Zhang, Xian Sheng

    2016-01-01

    Pollen–stigma interactions are essential for pollen germination. The highly regulated process of pollen germination includes pollen adhesion, hydration, and germination on the stigma. However, the internal signaling of pollen that regulates pollen–stigma interactions is poorly understood. KINβγ is a plant-specific subunit of the SNF1-related protein kinase 1 complex which plays important roles in the regulation of plant development. Here, we showed that KINβγ was a cytoplasm- and nucleus-localized protein in the vegetative cells of pollen grains in Arabidopsis. The pollen of the Arabidopsis kinβγ mutant could not germinate on stigma, although it germinated normally in vitro. Further analysis revealed the hydration of kinβγ mutant pollen on the stigma was compromised. However, adding water to the stigma promoted the germination of the mutant pollen in vivo, suggesting that the compromised hydration of the mutant pollen led to its defective germination. In kinβγ mutant pollen, the structure of the mitochondria and peroxisomes was destroyed, and their numbers were significantly reduced compared with those in the wild type. Furthermore, we found that the kinβγ mutant exhibited reduced levels of reactive oxygen species (ROS) in pollen. The addition of H2O2 in vitro partially compensated for the reduced water absorption of the mutant pollen, and reducing ROS levels in pollen by overexpressing Arabidopsis CATALASE 3 resulted in compromised hydration of pollen on the stigma. These results indicate that Arabidopsis KINβγ is critical for the regulation of ROS levels by mediating the biogenesis of mitochondria and peroxisomes in pollen, which is required for pollen–stigma interactions during pollination. PMID:27472382

  8. Transgene autoexcision in switchgrass pollen mediated by the Bxb1 recombinase

    PubMed Central

    2014-01-01

    Background Switchgrass (Panicum virgatum L.) has a great potential as a platform for the production of biobased plastics, chemicals and energy mainly because of its high biomass yield on marginal land and low agricultural inputs. During the last decade, there has been increased interest in the genetic improvement of this crop through transgenic approaches. Since switchgrass, like most perennial grasses, is exclusively cross pollinating and poorly domesticated, preventing the dispersal of transgenic pollen into the environment is a critical requisite for the commercial deployment of this important biomass crop. In this study, the feasibility of controlling pollen-mediated gene flow in transgenic switchgrass using the large serine site-specific recombinase Bxb1 has been investigated. Results A novel approach utilizing co-transformation of two separate vectors was used to test the functionality of the Bxb1/att recombination system in switchgrass. In addition, two promoters with high pollen-specific activity were identified and thoroughly characterized prior to their introduction into a test vector explicitly designed for both autoexcision and quantitative analyses of recombination events. Our strategy for developmentally programmed precise excision of the recombinase and marker genes in switchgrass pollen resulted in the generation of transgene-excised progeny. The autoexcision efficiencies were in the range of 22-42% depending on the transformation event and assay used. Conclusion The results presented here mark an important milestone towards the establishment of a reliable biocontainment system for switchgrass which will facilitate the development of this crop as a biorefinery feedstock through advanced biotechnological approaches. PMID:25148894

  9. IAA stimulates pollen tube growth and mediates the modification of its wall composition and structure in Torenia fournieri

    PubMed Central

    Wu, Juan-Zi; Lin, Yi; Zhang, Xue-Lian; Pang, Dai-Wen; Zhao, Jie

    2008-01-01

    The effects of several hormones on pollen tube growth were compared in Torenia fournieri and it was found that IAA was the most effective, stimulating pollen tube growth and causing the shank part of pollen tubes to be slender and straighter. The role of IAA was investigated by studying the changes in ultrastructure and PM H+-ATPase distribution in the pollen tubes and the modification of the tube wall. Using the fluorescent marker FM4-64, together with transmission electron microscopy, it was shown that secretory vesicles and mitochondria increased in IAA-treated tubes. Immunolocalization and fluorescence labelling, together with Fourier-transform infrared analysis, detected that IAA enhanced the level of PM H+-ATPase and the synthesis of pectins, and reduced the cellulose density in pollen tubes. Importantly, to observe the orientation of cellulose microfibrils in pollen tubes in situ, atomic force microscopy was used to examine the ‘intact’ tube wall. Atomic force microscopy images showed that cellulose microfibrils were parallel to each other in the subapical region of IAA-treated tubes, but disorganized in control tubes. All results provided new insights into the functions of cellulose microfibrils in pollen tube growth and direction, and revealed that the IAA-induced changes of pollen tubes were attributed to the increase in secretory vesicles, mitochondria, and PM H+-ATPase, and the modification of pectin and cellulose microfibrils in the tube wall. PMID:18544613

  10. Direct mediation, duality and unification

    NASA Astrophysics Data System (ADS)

    Abel, Steven; Khoze, Valentin V.

    2008-11-01

    It is well-known that in scenarios with direct gauge mediation of supersymmetry breaking the messenger fields significantly affect the running of Standard Model couplings and introduce Landau poles which are difficult to avoid. Among other things, this appears to remove any possibility of a meaningful unification prediction and is often viewed as a strong argument against direct mediation. We propose two ways that Seiberg duality can circumvent this problem. In the first, which we call ``deflected-unification'', the SUSY-breaking hidden sector is a magnetic theory which undergoes a Seiberg duality to an electric phase. Importantly, the electric version has fewer fundamental degrees of freedom coupled to the MSSM compared to the magnetic formulation. This changes the β-functions of the MSSM gauge couplings so as to push their Landau poles above the unification scale. We show that this scenario is realised for recently suggested models of gauge mediation based on a metastable SCQD-type hidden sector directly coupled to MSSM. The second possibility for avoiding Landau poles, which we call ``dual-unification'', begins with the observation that, if the mediating fields fall into complete SU(5) multiplets, then the MSSM+messengers exhibits a fake unification at unphysical values of the gauge couplings. We show that, in known examples of electric/magnetic duals, such a fake unification in the magnetic theory reflects a real unification in the electric theory. We therefore propose that the Standard Model could itself be a magnetic dual of some unknown electric theory in which the true unification takes place. This scenario maintains the unification prediction (and unification scale) even in the presence of Landau poles in the magnetic theory below the GUT scale. We further note that this dual realization of grand unification can explain why Nature appears to unify, but the proton does not decay.

  11. Pollen-mediated intraspecific gene flow from herbicide resistant oilseed rape (Brassica napus L.).

    PubMed

    Hüsken, Alexandra; Dietz-Pfeilstetter, Antje

    2007-10-01

    The cultivation of genetically modified (GM) herbicide resistant oilseed rape (Brassica napus) has increased over the past few years. The transfer of herbicide resistance genes via pollen (gene flow) from GM crops to non-GM crops is of relevance for the realisation of co-existence of different agricultural cultivation forms as well as for weed management. Therefore the likelihood of pollen-mediated gene flow has been investigated in numerous studies. Despite the difficulty to compare different experiments with varying levels of outcrossing, we performed a literature search for world-wide studies on cross-fertilisation in fully fertile oilseed rape. The occurrence and frequency of pollen-mediated intraspecific gene flow (outcrossing rate) can vary according to cultivar, experimental design, local topography and environmental conditions. The outcrossing rate from one field to another depends also on the size and arrangement of donor and recipient populations and on the ratio between donor and recipient plot size. The outcrossing levels specified in the presented studies are derived mostly from experiments where the recipient field is either surrounding the donor field (continuous design) or is located as a patch at different distances from the donor field (discontinuous design). Reports of gene flow in Brassica napus generally show that the amount of cross-fertilisation decreases as the distance from the pollen source increases. The evidence given in various studies reveals that the bulk of GM cross-fertilisation occurs within the first 10 m of the recipient field. The removal of the first 10 m of a non-transgenic field facing a GM crop might therefore be more efficient for reducing the total level of cross-fertilisation in a recipient sink population than to recommend separation distances. Future experiments should investigate cross-fertilisation with multiple adjacent donor fields at the landscape level under different spatial distributions of rapeseed cultivars

  12. Acetylesterase-Mediated Deacetylation of Pectin Impairs Cell Elongation, Pollen Germination, and Plant Reproduction

    SciTech Connect

    Gou J. Y.; Liu C.; Miller, L. M.; Hou, G.; Yu, X.-H.; Chen, X.-Y.

    2012-01-01

    Pectin is a major component of the primary cell wall of higher plants. Some galacturonyl residues in the backbone of pectinaceous polysaccharides are often O-acetylated at the C-2 or C-3 position, and the resulting acetylesters change dynamically during the growth and development of plants. The processes involve both enzymatic acetylation and deacetylation. Through genomic sequence analysis, we identified a pectin acetylesterase (PAE1) from black cottonwood (Populus trichocarpa). Recombinant Pt PAE1 exhibited preferential activity in releasing the acetate moiety from sugar beet (Beta vulgaris) and potato (Solanum tuberosum) pectin in vitro. Overexpressing Pt PAE1 in tobacco (Nicotiana tabacum) decreased the level of acetyl esters of pectin but not of xylan. Deacetylation engendered differential changes in the composition and/or structure of cell wall polysaccharides that subsequently impaired the cellular elongation of floral styles and filaments, the germination of pollen grains, and the growth of pollen tubes. Consequently, plants overexpressing PAE1 exhibited severe male sterility. Furthermore, in contrast to the conventional view, PAE1-mediated deacetylation substantially lowered the digestibility of pectin. Our data suggest that pectin acetylesterase functions as an important structural regulator in planta by modulating the precise status of pectin acetylation to affect the remodeling and physiochemical properties of the cell wall's polysaccharides, thereby affecting cell extensibility.

  13. Arabidopsis CBP1 Is a Novel Regulator of Transcription Initiation in Central Cell-Mediated Pollen Tube Guidance[OPEN

    PubMed Central

    Li, Hong-Ju; Zhu, Shan-Shan; Zhang, Meng-Xia; Wang, Tong; Xue, Yong; Shi, Dong-Qiao; Liu, Jie

    2015-01-01

    In flowering plants, sperm cells are delivered to the embryo sac by a pollen tube guided by female signals. Both the gametic and synergid cells contribute to pollen tube attraction. Synergids secrete peptide signals that lure the tube, while the role of the gametic cells is unknown. Previously, we showed that CENTRAL CELL GUIDANCE (CCG) is essential for pollen tube attraction in Arabidopsis thaliana, but the molecular mechanism is unclear. Here, we identified CCG BINDING PROTEIN1 (CBP1) and demonstrated that it interacts with CCG, Mediator subunits, RNA polymerase II (Pol II), and central cell-specific AGAMOUS-like transcription factors. In addition, CCG interacts with TATA-box Binding Protein 1 and Pol II as a TFIIB-like transcription factor. CBP1-knockdown ovules are defective in pollen tube attraction. Expression profiling revealed that cysteine-rich peptide (CRP) transcripts were downregulated in ccg ovules. CCG and CBP1 coregulate a subset of CRPs in the central cell and the synergids, including the attractant LURE1. CBP1 is extensively expressed in multiple vegetative tissues and specifically in the central cell in reproductive growth. We propose that CBP1, via interaction with CCG and the Mediator complex, connects transcription factors and the Pol II machinery to regulate pollen tube attraction. PMID:26462908

  14. AtVPS41-mediated endocytic pathway is essential for pollen tube-stigma interaction in Arabidopsis.

    PubMed

    Hao, Lihong; Liu, Jingjing; Zhong, Sheng; Gu, Hongya; Qu, Li-Jia

    2016-05-31

    In flowering plants, extensive male-female interactions are required for successful fertilization in which various signaling cascades are involved. Prevacuolar compartments (PVC) and vacuoles are two types of subcellular compartments that terminate signal transduction by sequestrating signaling molecules in yeast and mammalian cells; however, the manner in which they might be involved in male-female interactions in plants is unknown. In this study, we identified Arabidopsis thaliana vacuolar protein sorting 41 (AtVPS41), encoded by a single-copy gene with sequence similarity to yeast Vps41p, as a new factor controlling pollen tube-stigma interaction. Loss of AtVPS41 function disrupted penetration of pollen tubes into the transmitting tissue and thus led to failed male transmission. In the pollen tubes, AtVPS41 protein is associated with PVCs and the tonoplast. We demonstrate that AtVPS41 is required for the late stage of the endocytic pathway (i.e., endomembrane trafficking from PVCs to vacuoles) because internalization of cell-surface molecules was normal in the vps41-deficient pollen tubes, whereas PVC-to-vacuole trafficking was impaired. We further show that the CHCR domain is required for subcellular localization and biological functioning of AtVPS41. These results indicate that the AtVPS41-mediated late stage of the endocytic pathway is essential for pollen tube-stigma interaction in Arabidopsis. PMID:27185920

  15. AtVPS41-mediated endocytic pathway is essential for pollen tube–stigma interaction in Arabidopsis

    PubMed Central

    Hao, Lihong; Liu, Jingjing; Zhong, Sheng; Gu, Hongya; Qu, Li-Jia

    2016-01-01

    In flowering plants, extensive male–female interactions are required for successful fertilization in which various signaling cascades are involved. Prevacuolar compartments (PVC) and vacuoles are two types of subcellular compartments that terminate signal transduction by sequestrating signaling molecules in yeast and mammalian cells; however, the manner in which they might be involved in male–female interactions in plants is unknown. In this study, we identified Arabidopsis thaliana vacuolar protein sorting 41 (AtVPS41), encoded by a single-copy gene with sequence similarity to yeast Vps41p, as a new factor controlling pollen tube–stigma interaction. Loss of AtVPS41 function disrupted penetration of pollen tubes into the transmitting tissue and thus led to failed male transmission. In the pollen tubes, AtVPS41 protein is associated with PVCs and the tonoplast. We demonstrate that AtVPS41 is required for the late stage of the endocytic pathway (i.e., endomembrane trafficking from PVCs to vacuoles) because internalization of cell-surface molecules was normal in the vps41-deficient pollen tubes, whereas PVC-to-vacuole trafficking was impaired. We further show that the CHCR domain is required for subcellular localization and biological functioning of AtVPS41. These results indicate that the AtVPS41-mediated late stage of the endocytic pathway is essential for pollen tube–stigma interaction in Arabidopsis. PMID:27185920

  16. Current Directions in Mediation Analysis

    PubMed Central

    MacKinnon, David P.; Fairchild, Amanda J.

    2010-01-01

    Mediating variables continue to play an important role in psychological theory and research. A mediating variable transmits the effect of an antecedent variable on to a dependent variable, thereby providing more detailed understanding of relations among variables. Methods to assess mediation have been an active area of research for the last two decades. This paper describes the current state of methods to investigate mediating variables. PMID:20157637

  17. Immunomodulatory mediators from pollen enhance the migratory capacity of dendritic cells and license them for Th2 attraction.

    PubMed

    Mariani, Valentina; Gilles, Stefanie; Jakob, Thilo; Thiel, Martina; Mueller, Martin J; Ring, Johannes; Behrendt, Heidrun; Traidl-Hoffmann, Claudia

    2007-06-15

    The immune response of atopic individuals against allergens is characterized by increased levels of Th2 cytokines and chemokines. However, the way in which the cytokine/chemokine profile is matched to the type of invading allergen, and why these profiles sometimes derail and lead to disease, is not well understood. We recently demonstrated that pollen modulates dendritic cell (DC) function in a way that results in an enhanced capacity to initiate Th2 responses in vitro. Here, we examined the effects of aqueous birch pollen extracts (Bet.-APE) on chemokine receptor expression and chemokine production by human monocyte-derived DCs. Bet.-APE strongly induced expression and function of CXCR4 and reduced CCR1 and CCR5 expression on immature DCs. In addition, DC treatment with Bet.-APE significantly reduced LPS-induced production of CXCL10/IP-10, CCL5/RANTES; induced CCL22/macrophage-derived chemokine; and did not significantly change release of CCL17/thymus and activation-regulated chemokine. At a functional level, Bet.-APE increased the capacity of LPS-stimulated DCs to attract Th2 cells, whereas the capacity to recruit Th1 cells was reduced. Bet.-APE significantly and dose-dependently enhanced intracellular cAMP, suggesting that water-soluble factors from pollen grains bind a G(alphas)-protein-coupled receptor. E(1)-Phytoprostanes were identified to be one player in the Th2-polarizing potential of aqueous pollen extracts. In summary, our results demonstrate that pollen itself releases regulatory mediators which generate a Th2-promoting micromilieu with preferential recruitment of Th2 cells to the site of pollen exposure. PMID:17548598

  18. ABCG26-Mediated Polyketide Trafficking and Hydroxycinnamoyl Spermidines Contribute to Pollen Wall Exine Formation in Arabidopsis[W

    PubMed Central

    Quilichini, Teagen D.; Samuels, A. Lacey; Douglas, Carl J.

    2014-01-01

    Pollen grains are encased by a multilayered, multifunctional wall. The sporopollenin and pollen coat constituents of the outer pollen wall (exine) are contributed by surrounding sporophytic tapetal cells. Because the biosynthesis and development of the exine occurs in the innermost cell layers of the anther, direct observations of this process are difficult. The objective of this study was to investigate the transport and assembly of exine components from tapetal cells to microspores in the intact anthers of Arabidopsis thaliana. Intrinsically fluorescent components of developing tapetum and microspores were imaged in intact, live anthers using two-photon microscopy. Mutants of ABCG26, which encodes an ATP binding cassette transporter required for exine formation, accumulated large fluorescent vacuoles in tapetal cells, with corresponding loss of fluorescence on microspores. These vacuolar inclusions were not observed in tapetal cells of double mutants of abcg26 and genes encoding the proposed sporopollenin polyketide biosynthetic metabolon (ACYL COENZYME A SYNTHETASE5, POLYKETIDE SYNTHASE A [PKSA], PKSB, and TETRAKETIDE α-PYRONE REDUCTASE1), providing a genetic link between transport by ABCG26 and polyketide biosynthesis. Genetic analysis also showed that hydroxycinnamoyl spermidines, known components of the pollen coat, were exported from tapeta prior to programmed cell death in the absence of polyketides, raising the possibility that they are incorporated into the exine prior to pollen coat deposition. We propose a model where ABCG26-exported polyketides traffic from tapetal cells to form the sporopollenin backbone, in coordination with the trafficking of additional constituents, prior to tapetum programmed cell death. PMID:25415974

  19. A pollen-specific calmodulin-binding protein, NPG1, interacts with putative pectate lyases

    PubMed Central

    Shin, Sung-Bong; Golovkin, Maxim; Reddy, Anireddy S. N.

    2014-01-01

    Previous genetic studies have revealed that a pollen-specific calmodulin-binding protein, No Pollen Germination 1 (NPG1), is required for pollen germination. However, its mode of action is unknown. Here we report direct interaction of NPG1 with pectate lyase-like proteins (PLLs). A truncated form of AtNPG1 lacking the N-terminal tetratricopeptide repeat 1 (TPR1) failed to interact with PLLs, suggesting that it is essential for NPG1 interaction with PLLs. Localization studies with AtNPG1 fused to a fluorescent reporter driven by its native promoter revealed its presence in the cytosol and cell wall of the pollen grain and the growing pollen tube of plasmolyzed pollen. Together, our data suggest that the function of NPG1 in regulating pollen germination is mediated through its interaction with PLLs, which may modify the pollen cell wall and regulate pollen tube emergence and growth. PMID:24919580

  20. The Effect of Pollinator Type and Plant Spatial Structure on Patterns of Pollen-Mediated Gene Dispersal in Aquilegia Coerulea

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Background/Question/Methods - Direct estimation of pollen dispersal distances from paternity type analyses is often not possible. Therefore, recent emphasis have been on the development of indirect methods relying on the assumed decay with spatial distance in a measure of the genetic structure of p...

  1. Pollen-mediated gene flow from transgenic cotton under greenhouse conditions is dependent on different pollinators.

    PubMed

    Yan, Shuo; Zhu, Jialin; Zhu, Weilong; Li, Zhen; Shelton, Anthony M; Luo, Junyu; Cui, Jinjie; Zhang, Qingwen; Liu, Xiaoxia

    2015-01-01

    With the large-scale release of genetically modified (GM) crops, there are ecological concerns on transgene movement from GM crops to non-GM counterparts and wild relatives. In this research, we conducted greenhouse experiments to measure pollen-mediated gene flow (PGF) in the absence and presence of pollinators (Bombus ignitus, Apis mellifera and Pieris rapae) in one GM cotton (resistant to the insect Helicoverpa armigera and the herbicide glyphosate) and two non-GM lines (Shiyuan321 and Hai7124) during 2012 and 2013. Our results revealed that: (1) PGF varied depending on the pollinator species, and was highest with B. ignitus (10.83%) and lowest with P. rapae (2.71%); (2) PGF with B. ignitus depended on the distance between GM and non-GM cottons; (3) total PGF to Shiyuan321 (8.61%) was higher than to Hai7124 (4.10%). To confirm gene flow, we tested hybrids carrying transgenes for their resistance to glyphosate and H. armigera, and most hybrids showed strong resistance to the herbicide and insect. Our research confirmed that PGF depended on pollinator species, distance between plants and the receptor plant. PMID:26525573

  2. Pollen-mediated gene flow from transgenic cotton under greenhouse conditions is dependent on different pollinators

    PubMed Central

    Yan, Shuo; Zhu, Jialin; Zhu, Weilong; Li, Zhen; Shelton, Anthony M.; Luo, Junyu; Cui, Jinjie; Zhang, Qingwen; Liu, Xiaoxia

    2015-01-01

    With the large-scale release of genetically modified (GM) crops, there are ecological concerns on transgene movement from GM crops to non-GM counterparts and wild relatives. In this research, we conducted greenhouse experiments to measure pollen-mediated gene flow (PGF) in the absence and presence of pollinators (Bombus ignitus, Apis mellifera and Pieris rapae) in one GM cotton (resistant to the insect Helicoverpa armigera and the herbicide glyphosate) and two non-GM lines (Shiyuan321 and Hai7124) during 2012 and 2013. Our results revealed that: (1) PGF varied depending on the pollinator species, and was highest with B. ignitus (10.83%) and lowest with P. rapae (2.71%); (2) PGF with B. ignitus depended on the distance between GM and non-GM cottons; (3) total PGF to Shiyuan321 (8.61%) was higher than to Hai7124 (4.10%). To confirm gene flow, we tested hybrids carrying transgenes for their resistance to glyphosate and H. armigera, and most hybrids showed strong resistance to the herbicide and insect. Our research confirmed that PGF depended on pollinator species, distance between plants and the receptor plant. PMID:26525573

  3. Reproductive isolation is mediated by pollen incompatibility in sympatric populations of two Arnebia species.

    PubMed

    Wang, Lin-Lin; Zhang, Chan; Tian, Bin; Sun, Xu-Dong; Guo, Wen; Zhang, Ting-Feng; Yang, Yong-Ping; Duan, Yuan-Wen

    2015-12-01

    To explore uncertain aspects of the processes that maintain species boundaries, we evaluated contributions of pre- and postpollination reproductive isolation mechanisms in sympatric populations of Arnebia guttata and A. szechenyi. For this, we investigated their phylogenetic relationships, traits, microenvironments, pollinator visits, action of natural selection on floral traits, and the outcome of hand pollination between the two species. Phylogenetic analysis indicates that A. szechenyi is a derived species that could be closely related to A. guttata, and both could be diploid species. Arnebia guttata flowers have larger parts than A. szechenyi flowers, but smaller nectar guides. Soil supporting A. szechenyi had higher water contents than soil supporting neighboring populations of A. guttata (in accordance with their geographical distributions). The pollinators shared by the two species preferred A. szechenyi flowers, but interspecific visitations were frequent. We found evidence of conflicting selection pressures on floral tube length, flower diameter and nectar guide size mediated via male fitness, and on flower diameter and floral tube diameter via female fitness. Hand-pollination experiments indicate complete pollen incompatibility between the two species. Our results suggest that postpollination prezygotic mechanisms are largely responsible for reproductive isolation of sympatric populations of the two Arnebia species. PMID:26811758

  4. Cell-Cell Interactions during pollen tube guidance

    SciTech Connect

    Daphne Preuss

    2009-03-31

    The long-term goal of this research is to identify the signaling molecules that mediate plant cell-cell interactions during pollination. The immediate goals of this project are to perform genetic and molecular analysis of pollen tube guidance. Specifically, we proposed to: 1. Characterize the pistil components that direct pollen tube navigation using the Arabidopsis thaliana in vitro pollen tube guidance system 2. Identify pistil signals that direct pollen tube guidance by a) using microarrays to profile gene expression in developing pistils, and b) employing proteomics and metabolomics to isolate pollen tube guidance signals. 3. Explore the genetic basis of natural variation in guidance signals, comparing the in vitro interactions between pollen and pistils from A. thaliana and its close relatives.

  5. Investigating Pollen and Gene Flow of WYMV-Resistant Transgenic Wheat N12-1 Using a Dwarf Male-Sterile Line as the Pollen Receptor

    PubMed Central

    Dong, Shanshan; Liu, Yan; Yu, Cigang; Zhang, Zhenhua; Chen, Ming; Wang, Changyong

    2016-01-01

    Pollen-mediated gene flow (PMGF) is the main mode of transgene flow in flowering plants. The study of pollen and gene flow of transgenic wheat can help to establish the corresponding strategy for preventing transgene escape and contamination between compatible genotypes in wheat. To investigate the pollen dispersal and gene flow frequency in various directions and distances around the pollen source and detect the association between frequency of transgene flow and pollen density from transgenic wheat, a concentric circle design was adopted to conduct a field experiment using transgenic wheat with resistance to wheat yellow mosaic virus (WYMV) as the pollen donor and dwarf male-sterile wheat as the pollen receptor. The results showed that the pollen and gene flow of transgenic wheat varied significantly among the different compass sectors. A higher pollen density and gene flow frequency was observed in the downwind SW and W sectors, with average frequencies of transgene flow of 26.37 and 23.69% respectively. The pollen and gene flow of transgenic wheat declined dramatically with increasing distance from its source. Most of the pollen grains concentrated within 5 m and only a few pollen grains were detected beyond 30 m. The percentage of transgene flow was the highest where adjacent to the pollen source, with an average of 48.24% for all eight compass directions at 0 m distance. Transgene flow was reduced to 50% and 95% between 1.61 to 3.15 m, and 10.71 to 20.93 m, respectively. Our results suggest that climate conditions, especially wind direction, may significantly affect pollen dispersal and gene flow of wheat. The isolation-by-distance model is one of the most effective methods for achieving stringent transgene confinement in wheat. The frequency of transgene flow is directly correlated with the relative density of GM pollen grains in air currents, and pollen competition may be a major factor influencing transgene flow. PMID:26975052

  6. Investigating Pollen and Gene Flow of WYMV-Resistant Transgenic Wheat N12-1 Using a Dwarf Male-Sterile Line as the Pollen Receptor.

    PubMed

    Dong, Shanshan; Liu, Yan; Yu, Cigang; Zhang, Zhenhua; Chen, Ming; Wang, Changyong

    2016-01-01

    Pollen-mediated gene flow (PMGF) is the main mode of transgene flow in flowering plants. The study of pollen and gene flow of transgenic wheat can help to establish the corresponding strategy for preventing transgene escape and contamination between compatible genotypes in wheat. To investigate the pollen dispersal and gene flow frequency in various directions and distances around the pollen source and detect the association between frequency of transgene flow and pollen density from transgenic wheat, a concentric circle design was adopted to conduct a field experiment using transgenic wheat with resistance to wheat yellow mosaic virus (WYMV) as the pollen donor and dwarf male-sterile wheat as the pollen receptor. The results showed that the pollen and gene flow of transgenic wheat varied significantly among the different compass sectors. A higher pollen density and gene flow frequency was observed in the downwind SW and W sectors, with average frequencies of transgene flow of 26.37 and 23.69% respectively. The pollen and gene flow of transgenic wheat declined dramatically with increasing distance from its source. Most of the pollen grains concentrated within 5 m and only a few pollen grains were detected beyond 30 m. The percentage of transgene flow was the highest where adjacent to the pollen source, with an average of 48.24% for all eight compass directions at 0 m distance. Transgene flow was reduced to 50% and 95% between 1.61 to 3.15 m, and 10.71 to 20.93 m, respectively. Our results suggest that climate conditions, especially wind direction, may significantly affect pollen dispersal and gene flow of wheat. The isolation-by-distance model is one of the most effective methods for achieving stringent transgene confinement in wheat. The frequency of transgene flow is directly correlated with the relative density of GM pollen grains in air currents, and pollen competition may be a major factor influencing transgene flow. PMID:26975052

  7. Low level of pollen-mediated gene flow from cultivated to wild grapevine: consequences for the evolution of the endangered subspecies Vitis vinifera L. subsp. silvestris.

    PubMed

    Di Vecchi-Staraz, Manuel; Laucou, Valérie; Bruno, Gérard; Lacombe, Thierry; Gerber, Sophie; Bourse, Thibaut; Boselli, Maurizio; This, Patrice

    2009-01-01

    A parentage and a paternity-based approach were tested for estimation of pollen-mediated gene flow in wild grapevine (Vitis vinifera L. subsp. silvestris), a wind-pollinated species occurring in Mediterranean Europe and southwestern Asia. For this purpose, 305 seedlings collected in 2 years at 2 locations in France from 4 wild female individuals and 417 wild individuals prospected from France and Italy were analyzed using 20 highly polymorphic microsatellite loci. Their profiles were compared with a database consisting of 3203 accessions from the Institut National de la Recherche Agronomique Vassal collection including cultivars, rootstocks, interspecific hybrids, and other wild individuals. Paternity was assigned for 202 (66.2%) of the 305 seedlings, confirming the feasibility of the method. Most of the fertilizing pollen could be assigned to wild males growing nearby. Estimates of pollen immigration from the cultivated compartment (i.e., the totality of cultivars) ranged from 4.2% to 26% from nearby vineyards and from hidden pollinators such as cultivars and rootstocks that had escaped from farms. In an open landscape, the pollen flow was correlated to the distance between individuals, the main pollinator being the closest wild male (accounting for 51.4-86.2% of the pollen flow). In a closed landscape, more complex pollination occurred. Analysis of the parentage of the 417 wild individuals also revealed relationships between nearby wild individuals, but in the case of 12 individuals (3%), analysis revealed pollen immigration from vineyards, confirming the fitness of the hybrid seedlings. These pollen fluxes may have a significant effect on the evolution of wild populations: on the one hand, the low level of pollen-mediated gene flow from cultivated to wild grapevine could contribute to a risk of extinction of the wild compartment (i.e., the totality of the wild individuals). On the other hand, pollen dispersal within the wild populations may induce inbreeding

  8. Spatial and Temporal Assessment of Pollen- and Seed-Mediated Gene Flow from Genetically Engineered Plum Prunus domestica

    PubMed Central

    Scorza, Ralph; Kriss, Alissa B.; Callahan, Ann M.; Webb, Kevin; Demuth, Mark; Gottwald, Tim

    2013-01-01

    Pollen flow from a 0.46 ha plot of genetically engineered (GE) Prunus domestica located in West Virginia, USA was evaluated from 2000–2010. Sentinel plum trees were planted at distances ranging from 132 to 854 m from the center of the GE orchard. Plots of mixed plum varieties and seedlings were located at 384, 484 and 998 m from the GE plot. Bee hives (Apis mellifera) were dispersed between the GE plum plot and the pollen flow monitoring sites. Pollen-mediated gene flow from out of the GE plum plot to non-GE plums under the study conditions was low, only occurring at all in 4 of 11 years and then in only 0.31% of the 12,116 seeds analyzed. When it occurred, gene flow, calculated as the number of GUS positive embryos/total embryos sampled, ranged from 0.215% at 132 m from the center of the GE plum plot (28 m from the nearest GE plum tree) to 0.033–0.017% at longer distances (384–998 m). Based on the percentage of GUS positive seeds per individual sampled tree the range was 0.4% to 12%. Within the GE field plot, gene flow ranged from 4.9 to 39%. Gene flow was related to distance and environmental conditions. A single year sample from a sentinel plot 132 m from the center of the GE plot accounted for 65% of the total 11-year gene flow. Spatial modeling indicated that gene flow dramatically decreased at distances over 400 m from the GE plot. Air temperature and rainfall were, respectively, positively and negatively correlated with gene flow, reflecting the effects of weather conditions on insect pollinator activity. Seed-mediated gene flow was not detected. These results support the feasibility of coexistence of GE and non-GE plum orchards. PMID:24098374

  9. Pollen-mediated dispersal of glyphosate-resistance in Palmer amaranth under field conditions.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In addition to being a strong competitor with cotton and other row crops, Palmer amaranth has developed resistance to numerous important agricultural herbicides, including glyphosate. The objective of this study was to determine if the glyphosate-resistance trait can be transferred via pollen moveme...

  10. Evolutionarily conserved phenylpropanoid pattern on angiosperm pollen.

    PubMed

    Fellenberg, Christin; Vogt, Thomas

    2015-04-01

    The male gametophyte of higher plants appears as a solid box containing the essentials to transmit genetic material to the next generation. These consist of haploid generative cells that are required for reproduction, and an invasive vegetative cell producing the pollen tube, both mechanically protected by a rigid polymer, the pollen wall, and surrounded by a hydrophobic pollen coat. This coat mediates the direct contact to the biotic and abiotic environments. It contains a mixture of compounds required not only for fertilization but also for protection against biotic and abiotic stressors. Among its metabolites, the structural characteristics of two types of phenylpropanoids, hydroxycinnamic acid amides and flavonol glycosides, are highly conserved in Angiosperm pollen. Structural and functional aspects of these compounds will be discussed. PMID:25739656

  11. Native bees mediate long-distance pollen dispersal in a shade coffee landscape mosaic

    PubMed Central

    Jha, Shalene; Dick, Christopher W.

    2010-01-01

    Coffee farms are often embedded within a mosaic of agriculture and forest fragments in the world's most biologically diverse tropical regions. Although shade coffee farms can potentially support native pollinator communities, the degree to which these pollinators facilitate gene flow for native trees is unknown. We examined the role of native bees as vectors of gene flow for a reproductively specialized native tree, Miconia affinis, in a shade coffee and remnant forest landscape mosaic. We demonstrate extensive cross-habitat gene flow by native bees, with pollination events spanning more than 1,800 m. Pollen was carried twice as far within shade coffee habitat as in nearby forest, and trees growing within shade coffee farms received pollen from a far greater number of sires than trees within remnant forest. The study shows that shade coffee habitats support specialized native pollinators that enhance the fecundity and genetic diversity of remnant native trees. PMID:20660738

  12. Acetylesterase-Mediated Deacetylation of Pectin Impairs Cell Elongation, Pollen Germination, and Plant Reproduction[C][W

    PubMed Central

    Gou, Jin-Ying; Miller, Lisa M.; Hou, Guichuan; Yu, Xiao-Hong; Chen, Xiao-Ya; Liu, Chang-Jun

    2012-01-01

    Pectin is a major component of the primary cell wall of higher plants. Some galacturonyl residues in the backbone of pectinaceous polysaccharides are often O-acetylated at the C-2 or C-3 position, and the resulting acetylesters change dynamically during the growth and development of plants. The processes involve both enzymatic acetylation and deacetylation. Through genomic sequence analysis, we identified a pectin acetylesterase (PAE1) from black cottonwood (Populus trichocarpa). Recombinant Pt PAE1 exhibited preferential activity in releasing the acetate moiety from sugar beet (Beta vulgaris) and potato (Solanum tuberosum) pectin in vitro. Overexpressing Pt PAE1 in tobacco (Nicotiana tabacum) decreased the level of acetyl esters of pectin but not of xylan. Deacetylation engendered differential changes in the composition and/or structure of cell wall polysaccharides that subsequently impaired the cellular elongation of floral styles and filaments, the germination of pollen grains, and the growth of pollen tubes. Consequently, plants overexpressing PAE1 exhibited severe male sterility. Furthermore, in contrast to the conventional view, PAE1-mediated deacetylation substantially lowered the digestibility of pectin. Our data suggest that pectin acetylesterase functions as an important structural regulator in planta by modulating the precise status of pectin acetylation to affect the remodeling and physiochemical properties of the cell wall's polysaccharides, thereby affecting cell extensibility. PMID:22247250

  13. Naturalness from Runaways in Direct Mediation

    SciTech Connect

    Schafer-Nameki, Sakura; Tamarit, Carlos; Torroba, Gonzalo; /SLAC

    2011-02-07

    Postulating that the NMSSM singlet is a meson of a microscopic confining theory opens up new model-building possibilities. Based on this, we construct calculable models of direct mediation that solve the {mu}/B{mu} problem and simultaneously lead to realistic phenomenology. The singlet that couples to the Higgs fields develops a runaway produced by soft interactions, then stabilized by a small superpotential perturbation. The mechanism is first realized in an O'Raifeartaigh model of direct gauge mediation with metastable supersymmetry breaking. Focusing then on the microscopic theory, we argue that super QCD with massless and massive flavors in the free magnetic phase gives rise to this dynamics in the infrared. A deformation of the SQCD superpotential leads to large spontaneous R-symmetry breaking, gaugino masses naturally at the scale of the Higgs mass parameters, and absence of CP violating phases.

  14. Naturalness from runaways in direct mediation

    SciTech Connect

    Schaefer-Nameki, Sakura; Tamarit, Carlos; Torroba, Gonzalo

    2011-02-01

    Postulating that the nonminimal supersymmetric standard model singlet is a meson of a microscopic confining theory opens up new model-building possibilities. Based on this, we construct calculable models of direct mediation that solve the {mu}/B{sub {mu}} problem and simultaneously lead to realistic phenomenology. The singlet that couples to the Higgs fields develops a runaway produced by soft interactions and then stabilized by a small superpotential perturbation. The mechanism is first realized in an O'Raifeartaigh model of direct gauge mediation with metastable supersymmetry breaking. Focusing then on the microscopic theory, we argue that super QCD with massless and massive flavors in the free magnetic phase gives rise to this dynamics in the infrared. A deformation of the super QCD superpotential leads to large spontaneous R-symmetry breaking, gaugino masses naturally at the scale of the Higgs mass parameters, and the absence of CP violating phases.

  15. Hypervariable Domains of Self-Incompatibility RNases Mediate Allele-Specific Pollen Recognition.

    PubMed Central

    Matton, D. P.; Maes, O.; Laublin, G.; Xike, Q.; Bertrand, C.; Morse, D.; Cappadocia, M.

    1997-01-01

    Self-incompatibility (SI) in angiosperms is a genetic mechanism that promotes outcrossing through rejection of self-pollen. In the Solanaceae, SI is determined by a multiallelic S locus whose only known product is an S RNase. S RNases show a characteristic pattern of five conserved and two hypervariable regions. These are thought to be involved in the catalytic function and in allelic specificity, respectively. When the Solanum chacoense S12S14 genotype is transformed with an S11 RNase, the styles of plants expressing significant levels of the transgene reject S11 pollen. A previously characterized S RNase, S13, differs from the S11 RNase by only 10 amino acids, four of which are located in the hypervariable regions. When S12S14 plants were transformed with a chimeric S11 gene in which these four residues were substituted with those present in the S13 RNase, the transgenic plants acquired the S13 phenotype. This result demonstrates that the S RNase hypervariable regions control allelic specificity. PMID:12237346

  16. Corolla chirality does not contribute to directed pollen movement in Hypericum perforatum (Hypericaceae): mirror image pinwheel flowers function as radially symmetric flowers in pollination.

    PubMed

    Diller, Carolina; Fenster, Charles B

    2016-07-01

    Corolla chirality, the pinwheel arrangement of petals within a flower, is found throughout the core eudicots. In 15 families, different chiral type flowers (i.e., right or left rotated corolla) exist on the same plant, and this condition is referred to as unfixed/enantiomorphic corolla chirality. There are no investigations on the significance of unfixed floral chirality on directed pollen movement even though analogous mirror image floral designs, for example, enantiostyly, has evolved in response to selection to direct pollinator and pollen movement. Here, we examine the role of corolla chirality on directing pollen transfer, pollinator behavior, and its potential influence on disassortative mating. We quantified pollen transfer and pollinator behavior and movement for both right and left rotated flowers in two populations of Hypericum perforatum. In addition, we quantified the number of right and left rotated flowers at the individual level. Pollinators were indifferent to corolla chirality resulting in no difference in pollen deposition between right and left flowers. Corolla chirality had no effect on pollinator and pollen movement between and within chiral morphs. Unlike other mirror image floral designs, corolla chirality appears to play no role in promoting disassortative mating in this species. PMID:27547334

  17. An improved model of direct gauge mediation

    NASA Astrophysics Data System (ADS)

    Agashe, Kaustubh

    1998-09-01

    We present a new, improved model of gauge mediation of dynamical SUSY Breaking: the model does not have gauge messengers or ~10 TeV scalars charged under the Standard Model (SM), thus avoiding the problem of negative (mass)2 for supersymmetric SM (SSM) scalars faced by some earlier models. The gauge mediation is direct, i.e., the messengers which communicate SUSY breaking to the SSM fields carry quantum numbers of the gauge group which breaks SUSY. These messenger fields couple to a modulus field. The model has a very simple particle content: the modulus and the messengers are the only chiral superfields (other than the SSM fields) in the model. The inverted hierarchy mechanism is used to generate a local SUSY breaking minimum for the modulus field in a perturbative regime thus making the model calculable.

  18. Evaluating the effects of pollinator-mediated interactions using pollen transfer networks: evidence of widespread facilitation in south Andean plant communities.

    PubMed

    Tur, C; Sáez, A; Traveset, A; Aizen, M A

    2016-05-01

    Information about the relative importance of competitive or facilitative pollinator-mediated interactions in a multi-species context is limited. We studied interspecific pollen transfer (IPT) networks to evaluate quantity and quality effects of pollinator sharing among plant species on three high-Andean communities at 1600, 1800 and 2000 m a.s.l. To estimate the sign of the effects (positive, neutral or negative), the relation between conspecific and heterospecific pollen deposited on stigmas was analysed with GLMMs. Network analyses showed that communities were characterised by the presence of pollen hub-donors and receptors. We inferred that facilitative and neutral pollinator-mediated interactions among plants prevailed over competition. Thus, the benefits from pollinator sharing seem to outweigh the costs (i.e. heterospecific deposition and conspecific pollen loss). The largest proportion of facilitated species was found at the highest elevation community, suggesting that under unfavourable conditions for the pollination service and at lower plant densities facilitation can be more common. PMID:26991916

  19. Pollen-Mediated Gene Flow in Maize: Implications for Isolation Requirements and Coexistence in Mexico, the Center of Origin of Maize.

    PubMed

    Baltazar, Baltazar M; Castro Espinoza, Luciano; Espinoza Banda, Armando; de la Fuente Martínez, Juan Manuel; Garzón Tiznado, José Antonio; González García, Juvencio; Gutiérrez, Marco Antonio; Guzmán Rodríguez, José Luis; Heredia Díaz, Oscar; Horak, Michael J; Madueño Martínez, Jesús Ignacio; Schapaugh, Adam W; Stojšin, Duška; Uribe Montes, Hugo Raúl; Zavala García, Francisco

    2015-01-01

    Mexico, the center of origin of maize (Zea mays L.), has taken actions to preserve the identity and diversity of maize landraces and wild relatives. Historically, spatial isolation has been used in seed production to maintain seed purity. Spatial isolation can also be a key component for a strategy to minimize pollen-mediated gene flow in Mexico between transgenic maize and sexually compatible plants of maize conventional hybrids, landraces, and wild relatives. The objective of this research was to generate field maize-to-maize outcrossing data to help guide coexistence discussions in Mexico. In this study, outcrossing rates were determined and modeled from eight locations in six northern states, which represent the most economically important areas for the cultivation of hybrid maize in Mexico. At each site, pollen source plots were planted with a yellow-kernel maize hybrid and surrounded by plots with a white-kernel conventional maize hybrid (pollen recipient) of the same maturity. Outcrossing rates were then quantified by assessing the number of yellow kernels harvested from white-kernel hybrid plots. The highest outcrossing values were observed near the pollen source (12.9% at 1 m distance). The outcrossing levels declined sharply to 4.6, 2.7, 1.4, 1.0, 0.9, 0.5, and 0.5% as the distance from the pollen source increased to 2, 4, 8, 12, 16, 20, and 25 m, respectively. At distances beyond 20 m outcrossing values at all locations were below 1%. These trends are consistent with studies conducted in other world regions. The results suggest that coexistence measures that have been implemented in other geographies, such as spatial isolation, would be successful in Mexico to minimize transgenic maize pollen flow to conventional maize hybrids, landraces and wild relatives. PMID:26162097

  20. Pollen-Mediated Gene Flow in Maize: Implications for Isolation Requirements and Coexistence in Mexico, the Center of Origin of Maize

    PubMed Central

    Gutiérrez, Marco Antonio; Guzmán Rodríguez, José Luis; Horak, Michael J.; Madueño Martínez, Jesús Ignacio; Schapaugh, Adam W.; Stojšin, Duška; Uribe Montes, Hugo Raúl

    2015-01-01

    Mexico, the center of origin of maize (Zea mays L.), has taken actions to preserve the identity and diversity of maize landraces and wild relatives. Historically, spatial isolation has been used in seed production to maintain seed purity. Spatial isolation can also be a key component for a strategy to minimize pollen-mediated gene flow in Mexico between transgenic maize and sexually compatible plants of maize conventional hybrids, landraces, and wild relatives. The objective of this research was to generate field maize-to-maize outcrossing data to help guide coexistence discussions in Mexico. In this study, outcrossing rates were determined and modeled from eight locations in six northern states, which represent the most economically important areas for the cultivation of hybrid maize in Mexico. At each site, pollen source plots were planted with a yellow-kernel maize hybrid and surrounded by plots with a white-kernel conventional maize hybrid (pollen recipient) of the same maturity. Outcrossing rates were then quantified by assessing the number of yellow kernels harvested from white-kernel hybrid plots. The highest outcrossing values were observed near the pollen source (12.9% at 1 m distance). The outcrossing levels declined sharply to 4.6, 2.7, 1.4, 1.0, 0.9, 0.5, and 0.5% as the distance from the pollen source increased to 2, 4, 8, 12, 16, 20, and 25 m, respectively. At distances beyond 20 m outcrossing values at all locations were below 1%. These trends are consistent with studies conducted in other world regions. The results suggest that coexistence measures that have been implemented in other geographies, such as spatial isolation, would be successful in Mexico to minimize transgenic maize pollen flow to conventional maize hybrids, landraces and wild relatives. PMID:26162097

  1. Pollen Primer

    MedlinePlus

    ... air filters (HEPA) or an electrostatic air filter. Tree Pollen Trees produce pollen earliest, as soon as January in ... distributed miles away. Fewer than 100 kinds of trees cause allergies. Some common ones are catalpa, elm, ...

  2. Pollen Allergy

    MedlinePlus

    ... pollen count, which is often reported by local weather broadcasts or allergy websites, is a measure of how much pollen is in the air. Pollen counts tend to be highest early in the morning on warm, dry, breezy days and lowest during chilly, wet periods. ...

  3. 5-Aminolevulinic Acid Thins Pear Fruits by Inhibiting Pollen Tube Growth via Ca2+-ATPase-Mediated Ca2+ Efflux

    PubMed Central

    An, Yuyan; Li, Jie; Duan, Chunhui; Liu, Longbo; Sun, Yongping; Cao, Rongxiang; Wang, Liangju

    2016-01-01

    Chemical fruit thinning has become a popular practice in modern fruit orchards for achieving high quality fruits, reducing costs of hand thinning and promoting return bloom. However, most of the suggested chemical thinners are often concerned for their detrimental effects and environmental problems. 5-Aminolevulic acid (ALA) is a natural, nontoxic, biodegradable, and environment-friendly plant growth regulator. One of its outstanding roles is improving plant photosynthesis and fruit quality. Here, results showed that applying 100–200 mg/L ALA at full bloom stage significantly reduced pear fruit set. Both in vivo and in vitro studies showed that ALA significantly inhibited pollen germination and tube growth. ALA decreased not only cytosolic Ca2+ concentration ([Ca2+]cyt) but also “tip-focused” [Ca2+]cyt gradient, indicating that ALA inhibited pollen tube growth by down-regulating calcium signaling. ALA drastically enhanced pollen Ca2+-ATPase activity, suggesting that ALA-induced decrease of calcium signaling probably resulted from activating calcium pump. The significant negative correlations between Ca2+-ATPase activity and pollen germination or pollen tube length further demonstrated the critical role of calcium pump in ALA's negative effect on pollen germination. Taken together, our results suggest that ALA at low concentrations is a potential biochemical thinner, and it inhibits pollen germination and tube growth via Ca2+ efflux by activating Ca2+-ATPase, thereby thinning fruits by preventing fertilization. PMID:26904082

  4. Pollen Tubes Lacking a Pair of K+ Transporters Fail to Target Ovules in Arabidopsis[C][W][OA

    PubMed Central

    Lu, Yongxian; Chanroj, Salil; Zulkifli, Lalu; Johnson, Mark A.; Uozumi, Nobuyuki; Cheung, Alice; Sze, Heven

    2011-01-01

    Flowering plant reproduction requires precise delivery of the sperm cells to the ovule by a pollen tube. Guidance signals from female cells are being identified; however, how pollen responds to those cues is largely unknown. Here, we show that two predicted cation/proton exchangers (CHX) in Arabidopsis thaliana, CHX21 and CHX23, are essential for pollen tube guidance. Male fertility was unchanged in single chx21 or chx23 mutants. However, fertility was impaired in chx21 chx23 double mutant pollen. Wild-type pistils pollinated with a limited number of single and double mutant pollen producing 62% fewer seeds than those pollinated with chx23 single mutant pollen, indicating that chx21 chx23 pollen is severely compromised. Double mutant pollen grains germinated and grew tubes down the transmitting tract, but the tubes failed to turn toward ovules. Furthermore, chx21 chx23 pollen tubes failed to enter the micropyle of excised ovules. Green fluorescent protein–tagged CHX23 driven by its native promoter was localized to the endoplasmic reticulum of pollen tubes. CHX23 mediated K+ transport, as CHX23 expression in Escherichia coli increased K+ uptake and growth in a pH-dependent manner. We propose that by modifying localized cation balance and pH, these transporters could affect steps in signal reception and/or transduction that are critical to shifting the axis of polarity and directing pollen growth toward the ovule. PMID:21239645

  5. Fragmentation can increase spatial genetic structure without decreasing pollen-mediated gene flow in a wind-pollinated tree.

    PubMed

    Wang, Rong; Compton, Stephen G; Chen, Xiao-Yong

    2011-11-01

    Fragmentation reduces population sizes, increases isolation between habitats and can result in restricted dispersal of pollen and seeds. Given that diploid seed dispersal contributes more to shaping fine-scale spatial genetic structure (SGS) than haploid pollen flow, we tested whether fine-scale SGS can be sensitive to fragmentation even if extensive pollen dispersal is maintained. Castanopsis sclerophylla (Lindley & Paxton) Schottky (Fagaceae), a wind-pollinated and gravity seed-dispersed tree, was studied in an area of southeast China where its populations have been fragmented to varying extents by human activity. Using different age classes of trees in areas subject to varying extents of fragmentation, we found no significant difference in genetic diversity between prefragmentation vs. postfragmentation C. sclerophylla subpopulations. Genetic differentiation among postfragmentation subpopulations was also only slightly lower than among prefragmentation subpopulations. In the most fragmented habitat, selfing rates were significantly higher than zero in prefragmentation, but not postfragmentation, cohorts. These results suggest that fragmentation had not decreased gene flow among these populations and that pollen flow remains extensive. However, significantly greater fine-scale SGS was found in postfragmentation subpopulations in the most fragmented habitat, but not in less fragmented habitats. This alteration in SGS reflected more restricted seed dispersal, induced by changes in the physical environments and the prevention of secondary seed dispersal by rodents. An increase in SGS can therefore result from more restricted seed dispersal, even in the face of extensive pollen flow, making it a sensitive indicator of the negative consequences of population fragmentation. PMID:21981067

  6. Light mediators in dark matter direct detections

    SciTech Connect

    Li, Tai; Miao, Sen; Zhou, Yu-Feng

    2015-03-17

    In an extended effective operator framework, we investigate in detail the effects of light mediators on the event spectra of dark matter (DM)-nucleus scatterings. The presence of light mediators changes the interpretation of the current experimental data, especially the determination of DM particle mass. We show by analytic and numerical illustrations that in general for all the operators relevant to spin-independent scatterings, the DM particle mass allowed by a given set of experimental data increases significantly when the mediator particle becomes lighter. For instance, in the case of CDMS-II-Si experiment, the allowed DM particle mass can reach ∼50 (100) GeV at 68% (90%) confidence level, which is much larger than ∼10 GeV in the case with contact interactions. The increase of DM particle mass saturates when the mediator mass is below O(10) MeV. The upper limits from other experiments such as SuperCDMS, CDMSlite, CDEX, XENON10/100, LUX, PandaX etc. all tend to be weaker toward high DM mass regions. In a combined analysis, we show that the presence of light mediators can partially relax the tension in the current results of CDMS-II-Si, SuperCDMS and LUX.

  7. Long-term monitoring of airborne pollen in Alaska and the Yukon: Possible implications for global change

    SciTech Connect

    Anderson, J.H.

    1992-03-01

    Airborne pollen and spores have been sampled since 1978 in Fairbanks and 1982 Anchorage and other Alaska-Yukon locations for medical and ecological purposes. Comparative analyses of pre- and post-1986 data subsets reveal that after 1986 (1) pollen is in the air earlier, (2) the multiyear average of degree-days promoting pollen onset is little changed while (3) annual variation in degree-days at onset is greater, (4) pollen and spore annual productions are considerably higher, and (5) there is more year-to-year variation in pollen production. These changes probably reflect directional changes in certain weather variables, and there is some indication that they are of global change significance, i.e., related to increasing atmospheric greenhouse gases. Correlations with pollen data suggest that weather variables of high influence are temperatures during specific periods following pollen dispersal in the preceding year and the average temperature in April of the current year. Annual variations in pollen dispersal might be roughly linked to the 11 year sunspot cycle through air temperature mediators. Weather in 1990, apparent pollen production cycles under endogenous control, and the impending sunspot maximum portend a very severe pollen season in 199 existing but unfunded sampling projects.

  8. EVIDENCE FOR LANDSCAPE LEVEL, POLLEN-MEDIATED GENE FLOW FROM CREEPING BENTGRASS WITH CP4 EPSPS AS A MARKER

    EPA Science Inventory

    In a landscape level study, gene flow via pollen was tracked from multiple source fields of genetically modified (GM) herbicide resistant creeping bentgrass (Agrostis stolonifera L.) to 75 of 138 sentinel plants of A. stolonifera and to 29 of 69 resident populations of Agrostis s...

  9. Spatial and temporal assessment of pollen- and seed-mediated gene flow from genetically engineered plum Prunus domestica

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pollen flow from a 0.46 ha plot of mixed transgenic Prunus domestica located in West Virginia, USA, was evaluated from 2000-2010. Sentinel trees of ‘Italian Prune’ and ‘Seneca‘ plums, which are sexually compatible with the transgenic trees, were planted at distances ranging from 132 to 854 m from t...

  10. Pollen-Associated Microbiome Correlates with Pollution Parameters and the Allergenicity of Pollen

    PubMed Central

    Obersteiner, Andrea; Gilles, Stefanie; Frank, Ulrike; Beck, Isabelle; Häring, Franziska; Ernst, Dietrich; Rothballer, Michael; Hartmann, Anton; Traidl-Hoffmann, Claudia; Schmid, Michael

    2016-01-01

    Pollen allergies have been rapidly increasing over the last decades. Many allergenic proteins and non-allergenic adjuvant compounds of pollen are involved in the plant defense against environmental or microbial stress. The first aim of this study was to analyze and compare the colonizing microbes on allergenic pollen. The second aim was to investigate detectable correlations between pollen microbiota and parameters of air pollution or pollen allergenicity. To reach these aims, bacterial and fungal DNA was isolated from pollen samples of timothy grass (Phleum pratense, n = 20) and birch trees (Betula pendula, n = 55). With this isolated DNA, a terminal restriction fragment length polymorphism analysis was performed. One result was that the microbial diversity on birch tree and timothy grass pollen samples (Shannon/Simpson diversity indices) was partly significantly correlated to allergenicity parameters (Bet v 1/Phl p 5, pollen-associated lipid mediators). Furthermore, the microbial diversity on birch pollen samples was correlated to on-site air pollution (nitrogen dioxide (NO2), ammonia (NH3), and ozone (O3)). What is more, a significant negative correlation was observed between the microbial diversity on birch pollen and the measured NO2 concentrations on the corresponding trees. Our results showed that the microbial composition of pollen was correlated to environmental exposure parameters alongside with a differential expression of allergen and pollen-associated lipid mediators. This might translate into altered allergenicity of pollen due to environmental and microbial stress. PMID:26910418

  11. Pollen-Associated Microbiome Correlates with Pollution Parameters and the Allergenicity of Pollen.

    PubMed

    Obersteiner, Andrea; Gilles, Stefanie; Frank, Ulrike; Beck, Isabelle; Häring, Franziska; Ernst, Dietrich; Rothballer, Michael; Hartmann, Anton; Traidl-Hoffmann, Claudia; Schmid, Michael

    2016-01-01

    Pollen allergies have been rapidly increasing over the last decades. Many allergenic proteins and non-allergenic adjuvant compounds of pollen are involved in the plant defense against environmental or microbial stress. The first aim of this study was to analyze and compare the colonizing microbes on allergenic pollen. The second aim was to investigate detectable correlations between pollen microbiota and parameters of air pollution or pollen allergenicity. To reach these aims, bacterial and fungal DNA was isolated from pollen samples of timothy grass (Phleum pratense, n = 20) and birch trees (Betula pendula, n = 55). With this isolated DNA, a terminal restriction fragment length polymorphism analysis was performed. One result was that the microbial diversity on birch tree and timothy grass pollen samples (Shannon/Simpson diversity indices) was partly significantly correlated to allergenicity parameters (Bet v 1/Phl p 5, pollen-associated lipid mediators). Furthermore, the microbial diversity on birch pollen samples was correlated to on-site air pollution (nitrogen dioxide (NO2), ammonia (NH3), and ozone (O3)). What is more, a significant negative correlation was observed between the microbial diversity on birch pollen and the measured NO2 concentrations on the corresponding trees. Our results showed that the microbial composition of pollen was correlated to environmental exposure parameters alongside with a differential expression of allergen and pollen-associated lipid mediators. This might translate into altered allergenicity of pollen due to environmental and microbial stress. PMID:26910418

  12. Cryptochrome 2 mediates directional magnetoreception in cockroaches.

    PubMed

    Bazalova, Olga; Kvicalova, Marketa; Valkova, Tereza; Slaby, Pavel; Bartos, Premysl; Netusil, Radek; Tomanova, Katerina; Braeunig, Peter; Lee, How-Jing; Sauman, Ivo; Damulewicz, Milena; Provaznik, Jan; Pokorny, Richard; Dolezel, David; Vacha, Martin

    2016-02-01

    The ability to perceive geomagnetic fields (GMFs) represents a fascinating biological phenomenon. Studies on transgenic flies have provided evidence that photosensitive Cryptochromes (Cry) are involved in the response to magnetic fields (MFs). However, none of the studies tackled the problem of whether the Cry-dependent magnetosensitivity is coupled to the sole MF presence or to the direction of MF vector. In this study, we used gene silencing and a directional MF to show that mammalian-like Cry2 is necessary for a genuine directional response to periodic rotations of the GMF vector in two insect species. Longer wavelengths of light required higher photon fluxes for a detectable behavioral response, and a sharp detection border was present in the cyan/green spectral region. Both observations are consistent with involvement of the FADox, FAD(•-) and FADH(-) redox forms of flavin. The response was lost upon covering the eyes, demonstrating that the signal is perceived in the eye region. Immunohistochemical staining detected Cry2 in the hemispherical layer of laminal glia cells underneath the retina. Together, these findings identified the eye-localized Cry2 as an indispensable component and a likely photoreceptor of the directional GMF response. Our study is thus a clear step forward in deciphering the in vivo effects of GMF and supports the interaction of underlying mechanism with the visual system. PMID:26811445

  13. Cryptochrome 2 mediates directional magnetoreception in cockroaches

    PubMed Central

    Bazalova, Olga; Kvicalova, Marketa; Valkova, Tereza; Slaby, Pavel; Bartos, Premysl; Netusil, Radek; Tomanova, Katerina; Braeunig, Peter; Lee, How-Jing; Sauman, Ivo; Damulewicz, Milena; Provaznik, Jan; Pokorny, Richard; Dolezel, David; Vacha, Martin

    2016-01-01

    The ability to perceive geomagnetic fields (GMFs) represents a fascinating biological phenomenon. Studies on transgenic flies have provided evidence that photosensitive Cryptochromes (Cry) are involved in the response to magnetic fields (MFs). However, none of the studies tackled the problem of whether the Cry-dependent magnetosensitivity is coupled to the sole MF presence or to the direction of MF vector. In this study, we used gene silencing and a directional MF to show that mammalian-like Cry2 is necessary for a genuine directional response to periodic rotations of the GMF vector in two insect species. Longer wavelengths of light required higher photon fluxes for a detectable behavioral response, and a sharp detection border was present in the cyan/green spectral region. Both observations are consistent with involvement of the FADox, FAD•− and FADH– redox forms of flavin. The response was lost upon covering the eyes, demonstrating that the signal is perceived in the eye region. Immunohistochemical staining detected Cry2 in the hemispherical layer of laminal glia cells underneath the retina. Together, these findings identified the eye-localized Cry2 as an indispensable component and a likely photoreceptor of the directional GMF response. Our study is thus a clear step forward in deciphering the in vivo effects of GMF and supports the interaction of underlying mechanism with the visual system. PMID:26811445

  14. Strongly Coupled Semi-Direct Mediation of Supersymmetry Breaking

    SciTech Connect

    Ibe, M.; Izawa, K.-I.; Nakai, Y.; /Kyoto U., Yukawa Inst., Kyoto

    2011-09-13

    Supersymmetry (SUSY) is expected to be a crucial ingredient of basic laws in Nature. It is an attractive possibility that SUSY is broken at low energy within the experimental reach in the near future. Among others, low-energy dynamics with gauge mediation between a hidden sector of SUSY breaking and the visible sector of SUSY standard model may be phenomenologically viable. In particular, the gauge interactions are flavor blind, so that the unwanted flavor-changing processes are naturally suppressed. Strongly coupled semi-direct gauge mediation models of supersymmetry breaking through massive mediators with standard model charges are investigated by means of composite degrees of freedom. Sizable mediation is realized to generate the standard model gaugino masses for a small mediator mass without breaking the standard model symmetries.

  15. Linking pollinator visitation rate and pollen receipt.

    PubMed

    Cayenne Engel, E; Irwin, Rebecca E

    2003-11-01

    The majority of flowering plants require animals for pollination, a critical ecosystem service in natural and agricultural systems. However, quantifying useful estimates of pollinator visitation rates can be nearly impossible when pollinator visitation is infrequent. We examined the utility of an indirect measure of pollinator visitation, namely pollen receipt by flowers, using the hummingbird-pollinated plant, Ipomopsis aggregata (Polemoniaceae). Our a priori hypothesis was that increased pollinator visitation should result in increased pollen receipt by stigmas. However, the relationship between pollinator visitation rate and pollen receipt may be misleading if pollen receipt is a function of both the number of pollinator visits and variation in pollinator efficiency at depositing pollen, especially in the context of variable floral morphology. Therefore, we measured floral and plant characters known to be important to pollinator visitation and/or pollen receipt in I. aggregata (corolla length and width and plant height) and used path analysis to dissect and compare the effect of pollinator visitation rate vs. pollinator efficiency on pollen receipt. Of the characters we measured, pollinator visitation rate (number of times plants were visited multiplied by the mean percentage of flowers probed per visit) had the strongest direct positive effect on pollen receipt, explaining 36% of the variation in pollen receipt. Plant height had a direct positive effect on pollinator visitation rate and an indirect positive effect on pollen receipt. Despite the supposition that floral characters would directly affect pollen receipt as a result of changes in pollinator efficiency, corolla length and width only weakly affected pollen receipt. These results suggest a direct positive link between pollinator visitation rate and pollen receipt across naturally varying floral morphology in I. aggregata. Understanding the relationship between pollinator visitation rate and pollen

  16. BURSTING POLLEN is required to organize the pollen germination plaque and pollen tube tip in Arabidopsis thaliana.

    PubMed

    Hoedemaekers, Karin; Derksen, Jan; Hoogstrate, Suzanne W; Wolters-Arts, Mieke; Oh, Sung-Aeong; Twell, David; Mariani, Celestina; Rieu, Ivo

    2015-04-01

    Pollen germination may occur via the so-called germination pores or directly through the pollen wall at the site of contact with the stigma. In this study, we addressed what processes take place during pollen hydration (i.e. before tube emergence), in a species with extra-poral pollen germination, Arabidopsis thaliana. A T-DNA mutant population was screened by segregation distortion analysis. Histological and electron microscopy techniques were applied to examine the wild-type and mutant phenotypes. Within 1 h of the start of pollen hydration, an intine-like structure consisting of cellulose, callose and at least partly de-esterified pectin was formed at the pollen wall. Subsequently, this 'germination plaque' gradually extended and opened up to provide passage for the cytoplasm into the emerging pollen tube. BURSTING POLLEN (BUP) was identified as a gene essential for the correct organization of this plaque and the tip of the pollen tube. BUP encodes a novel Golgi-located glycosyltransferase related to the glycosyltransferase 4 (GT4) subfamily which is conserved throughout the plant kingdom. Extra-poral pollen germination involves the development of a germination plaque and BUP defines the correct plastic-elastic properties of this plaque and the pollen tube tip by affecting pectin synthesis or delivery. PMID:25442716

  17. Assessment of real-time PCR based methods for quantification of pollen-mediated gene flow from GM to conventional maize in a field study.

    PubMed

    Pla, Maria; La Paz, José-Luis; Peñas, Gisela; García, Nora; Palaudelmàs, Montserrat; Esteve, Teresa; Messeguer, Joaquima; Melé, Enric

    2006-04-01

    Maize is one of the main crops worldwide and an increasing number of genetically modified (GM) maize varieties are cultivated and commercialized in many countries in parallel to conventional crops. Given the labeling rules established e.g. in the European Union and the necessary coexistence between GM and non-GM crops, it is important to determine the extent of pollen dissemination from transgenic maize to other cultivars under field conditions. The most widely used methods for quantitative detection of GMO are based on real-time PCR, which implies the results are expressed in genome percentages (in contrast to seed or grain percentages). Our objective was to assess the accuracy of real-time PCR based assays to accurately quantify the contents of transgenic grains in non-GM fields in comparison with the real cross-fertilization rate as determined by phenotypical analysis. We performed this study in a region where both GM and conventional maize are normally cultivated and used the predominant transgenic maize Mon810 in combination with a conventional maize variety which displays the characteristic of white grains (therefore allowing cross-pollination quantification as percentage of yellow grains). Our results indicated an excellent correlation between real-time PCR results and number of cross-fertilized grains at Mon810 levels of 0.1-10%. In contrast, Mon810 percentage estimated by weight of grains produced less accurate results. Finally, we present and discuss the pattern of pollen-mediated gene flow from GM to conventional maize in an example case under field conditions. PMID:16604462

  18. City scale pollen concentration variability

    NASA Astrophysics Data System (ADS)

    van der Molen, Michiel; van Vliet, Arnold; Krol, Maarten

    2016-04-01

    Pollen are emitted in the atmosphere both in the country-side and in cities. Yet the majority of the population is exposed to pollen in cities. Allergic reactions may be induced by short-term exposure to pollen. This raises the question how variable pollen concentration in cities are in temporally and spatially, and how much of the pollen in cities are actually produced in the urban region itself. We built a high resolution (1 × 1 km) pollen dispersion model based on WRF-Chem to study a city's pollen budget and the spatial and temporal variability in concentration. It shows that the concentrations are highly variable, as a result of source distribution, wind direction and boundary layer mixing, as well as the release rate as a function of temperature, turbulence intensity and humidity. Hay Fever Forecasts based on such high resolution emission and physical dispersion modelling surpass traditional hay fever warning methods based on temperature sum methods. The model gives new insights in concentration variability, personal and community level exposure and prevention. The model will be developped into a new forecast tool to serve allergic people to minimize their exposure and reduce nuisance, coast of medication and sick leave. This is an innovative approach in hay fever warning systems.

  19. Allergies, asthma, and pollen

    MedlinePlus

    Allergic rhinitis - pollen ... them is your first step toward feeling better. Pollen is a trigger for many people who have allergies and asthma. The types of pollens that are triggers vary from person to person ...

  20. Pollen analyses for pollination research, unacetolyzed pollen

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pollinators can significantly increase the potential yield of crops, but little is known about which pollinators pollinate various crop species. Many pollinators feed on pollen, nectar and plant secretions associated with flowers, and consequently pollen attaches to the pollinators. Identification...

  1. Do urban canyons influence street level grass pollen concentrations?

    PubMed

    Peel, Robert George; Kennedy, Roy; Smith, Matt; Hertel, Ole

    2014-08-01

    In epidemiological studies, outdoor exposure to pollen is typically estimated using rooftop monitoring station data, whilst exposure overwhelmingly occurs at street level. In this study the relationship between street level and roof level grass pollen concentrations was investigated for city centre street canyon environments in Aarhus, Denmark, and London, UK, during the grass pollen seasons of 2010 and 2011 respectively. For the period mid-day to late evening, street level concentrations in both cities tended to be lower than roof-level concentrations, though this difference was found to be statistically significant only in London. The ratio of street/roof level concentrations was compared with temperature, relative humidity, wind speed and direction, and solar radiation. Results indicated that the concentration ratio responds to wind direction with respect to relative canyon orientation and local source distribution. In the London study, an increase in relative humidity was linked to a significant decrease in street/roof level concentration ratio, and a possible causative mechanism involving moisture mediated pollen grain buoyancy is proposed. Relationships with the other weather variables were not found to be significant in either location. These results suggest a tendency for monitoring station data to overestimate exposure in the canyon environment. PMID:24037300

  2. Do urban canyons influence street level grass pollen concentrations?

    NASA Astrophysics Data System (ADS)

    Peel, Robert George; Kennedy, Roy; Smith, Matt; Hertel, Ole

    2014-08-01

    In epidemiological studies, outdoor exposure to pollen is typically estimated using rooftop monitoring station data, whilst exposure overwhelmingly occurs at street level. In this study the relationship between street level and roof level grass pollen concentrations was investigated for city centre street canyon environments in Aarhus, Denmark, and London, UK, during the grass pollen seasons of 2010 and 2011 respectively. For the period mid-day to late evening, street level concentrations in both cities tended to be lower than roof-level concentrations, though this difference was found to be statistically significant only in London. The ratio of street/roof level concentrations was compared with temperature, relative humidity, wind speed and direction, and solar radiation. Results indicated that the concentration ratio responds to wind direction with respect to relative canyon orientation and local source distribution. In the London study, an increase in relative humidity was linked to a significant decrease in street/roof level concentration ratio, and a possible causative mechanism involving moisture mediated pollen grain buoyancy is proposed. Relationships with the other weather variables were not found to be significant in either location. These results suggest a tendency for monitoring station data to overestimate exposure in the canyon environment.

  3. Effect of topical applications of budesonide and azelastine on nasal symptoms, eosinophil count and mediator release in atopic patients after nasal allergen challenge during the pollen season.

    PubMed

    Wang, D; Smitz, J; De Waele, M; Clement, P

    1997-10-01

    We studied the activity of a topical form of a corticosteroid (budesonide) and an antihistamine (azelastine) in the treatment of seasonal allergic rhinitis by including an assessment of mediator concentrations and the percentage of eosinophils in the nasal secretions before and after the treatment. Nasal allergen challenge (NAC) during the season was performed to mimic an acute attack of allergic rhinitis and to objectively evaluate the effect of the drugs on the early-phase reaction. The study compared in a randomized way (2 parallel groups) the effect of budesonide (Rhinocort Aqua) and azelastine (Allergodil nasal spray) in a group of 14 patients during the pollen season. The study showed that azelastine significantly reduced sneezing, total nasal resistance and increased nasal airflow even when significant increases in histamine, tryptase and leukotriene C4 (LTC4) concentrations in nasal secretions were evidenced immediately after NAC. Budesonide showed a strong (p<0.05) decrease in infiltration and activation of eosinophils, and on tryptase and LTC4 release after NAC. These effects (not for LTC4) lasted at least for 1 week after therapy. Azelastine is a powerful topical antihistamine, while budesonide appears to be a potent long-acting anti-inflammatory agent. PMID:9338613

  4. ECHIDNA protein impacts on male fertility in Arabidopsis by mediating trans-Golgi network secretory trafficking during anther and pollen development.

    PubMed

    Fan, Xinping; Yang, Caiyun; Klisch, Doris; Ferguson, Alison; Bhaellero, Rishi P; Niu, Xiwu; Wilson, Zoe A

    2014-03-01

    The trans-Golgi network (TGN) plays a central role in cellular secretion and has been implicated in sorting cargo destined for the plasma membrane. Previously, the Arabidopsis (Arabidopsis thaliana) echidna (ech) mutant was shown to exhibit a dwarf phenotype due to impaired cell expansion. However, ech also has a previously uncharacterized phenotype of reduced male fertility. This semisterility is due to decreased anther size and reduced amounts of pollen but also to decreased pollen viability, impaired anther opening, and pollen tube growth. An ECH translational fusion (ECHPro:ECH-yellow fluorescent protein) revealed developmentally regulated tissue-specific expression, with expression in the tapetum during early anther development and microspore release and subsequent expression in the pollen, pollen tube, and stylar tissues. Pollen viability and production, along with germination and pollen tube growth, were all impaired. The ech anther endothecium secondary wall thickening also appeared reduced and disorganized, resulting in incomplete anther opening. This did not appear to be due to anther secondary thickening regulatory genes but perhaps to altered secretion of wall materials through the TGN as a consequence of the absence of the ECH protein. ECH expression is critical for a variety of aspects of male reproduction, including the production of functional pollen grains, their effective release, germination, and tube formation. These stages of pollen development are fundamentally influenced by TGN trafficking of hormones and wall components. Overall, this suggests that the fertility defect is multifaceted, with the TGN trafficking playing a significant role in the process of both pollen formation and subsequent fertilization. PMID:24424320

  5. Direct detection of exothermic dark matter with light mediator

    NASA Astrophysics Data System (ADS)

    Geng, Chao-Qiang; Huang, Da; Lee, Chun-Hao; Wang, Qing

    2016-08-01

    We study the dark matter (DM) direct detection for the models with the effects of the isospin-violating couplings, exothermic scatterings, and/or the lightness of the mediator, proposed to relax the tension between the CDMS-Si signals and null experiments. In the light of the new updates of the LUX and CDMSlite data, we find that many of the previous proposals are now ruled out, including the Ge-phobic exothermic DM model and the Xe-phobic DM one with a light mediator. We also examine the exothermic DM models with a light mediator but without the isospin violation, and we are unable to identify any available parameter space that could simultaneously satisfy all the experiments. The only models that can partially relax the inconsistencies are the Xe-phobic exothermic DM models with or without a light mediator. But even in this case, a large portion of the CDMS-Si regions of interest has been constrained by the LUX and SuperCDMS data.

  6. Less Pollen-Mediated Gene Flow for More Signatures of Glacial Lineages: Congruent Evidence from Balsam Fir cpDNA and mtDNA for Multiple Refugia in Eastern and Central North America

    PubMed Central

    Cinget, Benjamin; Gérardi, Sébastien; Beaulieu, Jean; Bousquet, Jean

    2015-01-01

    The phylogeographic structure and postglacial history of balsam fir (Abies balsamea), a transcontinental North American boreal conifer, was inferred using mitochondrial DNA (mtDNA) and chloroplast DNA (cpDNA) markers. Genetic structure among 107 populations (mtDNA data) and 75 populations (cpDNA data) was analyzed using Bayesian and genetic distance approaches. Population differentiation was high for mtDNA (dispersed by seeds only), but also for cpDNA (dispersed by seeds and pollen), indicating that pollen gene flow is more restricted in balsam fir than in other boreal conifers. Low cpDNA gene flow in balsam fir may relate to low pollen production due to the inherent biology of the species and populations being decimated by recurrent spruce budworm epidemics, and/or to low dispersal of pollen grains due to their peculiar structural properties. Accordingly, a phylogeographic structure was detected using both mtDNA and cpDNA markers and population structure analyses supported the existence of at least five genetically distinct glacial lineages in central and eastern North America. Four of these would originate from glacial refugia located south of the Laurentide ice sheet, while the last one would have persisted in the northern Labrador region. As expected due to reduced pollen-mediated gene flow, congruence between the geographic distribution of mtDNA and cpDNA lineages was higher than in other North American conifers. However, concordance was not complete, reflecting that restricted but nonetheless detectable cpDNA gene flow among glacial lineages occurred during the Holocene. As a result, new cpDNA and mtDNA genome combinations indicative of cytoplasmic genome capture were observed. PMID:25849816

  7. The Effects of Pollen-Enriched Pollen Substitute on Winter Cluster Size and the Prevalence of Nosema ceranae in Russian Honey Bee Colonies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study determined the effects of feeding a pollen substitute enriched with pollen and feeding protein in plastic frames placed directly in the brood nest on the growth of Russian honey bee colonies through the winter. Colonies were fed: 1) a mixture of 1/2 pollen and 1/2 commercial pollen substi...

  8. Barrier responses of human bronchial epithelial cells to grass pollen exposure.

    PubMed

    Blume, Cornelia; Swindle, Emily J; Dennison, Patrick; Jayasekera, Nivenka P; Dudley, Sarah; Monk, Phillip; Behrendt, Heidrun; Schmidt-Weber, Carsten B; Holgate, Stephen T; Howarth, Peter H; Traidl-Hoffmann, Claudia; Davies, Donna E

    2013-07-01

    The airway epithelium forms a physical, chemical and immunological barrier against inhaled environmental substances. In asthma, these barrier properties are thought to be abnormal. In this study, we analysed the effect of grass pollen on the physical and immunological barrier properties of differentiated human primary bronchial epithelial cells. Following exposure to Timothy grass (Phleum pratense) pollen extract, the integrity of the physical barrier was not impaired as monitored by measuring the transepithelial resistance and immunofluorescence staining of tight junction proteins. In contrast, pollen exposure affected the immunological barrier properties by modulating vectorial mediator release. CXC chemokine ligand (CXCL)8/interleukin (IL)-8 showed the greatest increase in response to pollen exposure with preferential release to the apical compartment. Inhibition of the extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase pathways selectively blocked apical CXCL8/IL-8 release via a post-transcriptional mechanism. Apical release of CC chemokine ligand (CCL)20/macrophage inflammatory protein-3α, CCL22/monocyte-derived chemokine and tumour necrosis factor-α was significantly increased only in severe asthma cultures, while CCL11/eotaxin-1 and CXCL10/interferon-γ-induced protein-10 were reduced in nonasthmatic cultures. The bronchial epithelial barrier modulates polarised release of mediators in response to pollen without direct effects on its physical barrier properties. The differential response of cells from normal and asthmatic donors suggests the potential for the bronchial epithelium to promote immune dysfunction in asthma. PMID:23143548

  9. Allergenic pollen and pollen allergy in Europe.

    PubMed

    D'Amato, G; Cecchi, L; Bonini, S; Nunes, C; Annesi-Maesano, I; Behrendt, H; Liccardi, G; Popov, T; van Cauwenberge, P

    2007-09-01

    The allergenic content of the atmosphere varies according to climate, geography and vegetation. Data on the presence and prevalence of allergenic airborne pollens, obtained from both aerobiological studies and allergological investigations, make it possible to design pollen calendars with the approximate flowering period of the plants in the sampling area. In this way, even though pollen production and dispersal from year to year depend on the patterns of preseason weather and on the conditions prevailing at the time of anthesis, it is usually possible to forecast the chances of encountering high atmospheric allergenic pollen concentrations in different areas. Aerobiological and allergological studies show that the pollen map of Europe is changing also as a result of cultural factors (for example, importation of plants such as birch and cypress for urban parklands), greater international travel (e.g. colonization by ragweed in France, northern Italy, Austria, Hungary etc.) and climate change. In this regard, the higher frequency of weather extremes, like thunderstorms, and increasing episodes of long range transport of allergenic pollen represent new challenges for researchers. Furthermore, in the last few years, experimental data on pollen and subpollen-particles structure, the pathogenetic role of pollen and the interaction between pollen and air pollutants, gave new insights into the mechanisms of respiratory allergic diseases. PMID:17521313

  10. Hive-stored pollen of honey bees: many lines of evidence are consistent with pollen preservation, not nutrient conversion.

    PubMed

    Anderson, Kirk E; Carroll, Mark J; Sheehan, Tim; Lanan, Michele C; Mott, Brendon M; Maes, Patrick; Corby-Harris, Vanessa

    2014-12-01

    Honey bee hives are filled with stored pollen, honey, plant resins and wax, all antimicrobial to differing degrees. Stored pollen is the nutritionally rich currency used for colony growth and consists of 40-50% simple sugars. Many studies speculate that prior to consumption by bees, stored pollen undergoes long-term nutrient conversion, becoming more nutritious 'bee bread' as microbes predigest the pollen. We quantified both structural and functional aspects associated with this hypothesis using behavioural assays, bacterial plate counts, microscopy and 454 amplicon sequencing of the 16S rRNA gene from both newly collected and hive-stored pollen. We found that bees preferentially consume fresh pollen stored for <3 days. Newly collected pollen contained few bacteria, values which decreased significantly as pollen were stored >96 h. The estimated microbe to pollen grain surface area ratio was 1:1 000 000 indicating a negligible effect of microbial metabolism on hive-stored pollen. Consistent with these findings, hive-stored pollen grains did not appear compromised according to microscopy. Based on year round 454 amplicon sequencing, bacterial communities of newly collected and hive-stored pollen did not differ, indicating the lack of an emergent microbial community co-evolved to digest stored pollen. In accord with previous culturing and 16S cloning, acid resistant and osmotolerant bacteria like Lactobacillus kunkeei were found in greatest abundance in stored pollen, consistent with the harsh character of this microenvironment. We conclude that stored pollen is not evolved for microbially mediated nutrient conversion, but is a preservative environment due primarily to added honey, nectar, bee secretions and properties of pollen itself. PMID:25319366

  11. Hive-stored pollen of honey bees: many lines of evidence are consistent with pollen preservation, not nutrient conversion

    PubMed Central

    Anderson, Kirk E; Carroll, Mark J; Sheehan, Tim; Mott, Brendon M; Maes, Patrick; Corby-Harris, Vanessa

    2014-01-01

    Honey bee hives are filled with stored pollen, honey, plant resins and wax, all antimicrobial to differing degrees. Stored pollen is the nutritionally rich currency used for colony growth and consists of 40–50% simple sugars. Many studies speculate that prior to consumption by bees, stored pollen undergoes long-term nutrient conversion, becoming more nutritious ‘bee bread’ as microbes predigest the pollen. We quantified both structural and functional aspects associated with this hypothesis using behavioural assays, bacterial plate counts, microscopy and 454 amplicon sequencing of the 16S rRNA gene from both newly collected and hive-stored pollen. We found that bees preferentially consume fresh pollen stored for <3 days. Newly collected pollen contained few bacteria, values which decreased significantly as pollen were stored >96 h. The estimated microbe to pollen grain surface area ratio was 1:1 000 000 indicating a negligible effect of microbial metabolism on hive-stored pollen. Consistent with these findings, hive-stored pollen grains did not appear compromised according to microscopy. Based on year round 454 amplicon sequencing, bacterial communities of newly collected and hive-stored pollen did not differ, indicating the lack of an emergent microbial community co-evolved to digest stored pollen. In accord with previous culturing and 16S cloning, acid resistant and osmotolerant bacteria like Lactobacillus kunkeei were found in greatest abundance in stored pollen, consistent with the harsh character of this microenvironment. We conclude that stored pollen is not evolved for microbially mediated nutrient conversion, but is a preservative environment due primarily to added honey, nectar, bee secretions and properties of pollen itself. PMID:25319366

  12. Testing the minimal direct gauge mediation at the LHC

    NASA Astrophysics Data System (ADS)

    Hamaguchi, Koichi; Ibe, Masahiro; Yanagida, Tsutomu T.; Yokozaki, Norimi

    2014-07-01

    We reexamine the models with gauge mediation in view of the minimality and the Higgs boson mass. As a result, we arrive at a very simple model of direct gauge mediation which does not suffer from the flavor problems nor the CP problems. The minimal supersymmetric Standard Model spectrum is determined by only three parameters, the size of the effective supersymmetry breaking, the messenger scale, and the messenger number. Surprisingly, such a very simple model is not only consistent with all the current constraints but also is testable at the upgraded LHC experiments. In particular, we show that the parameter space which is consistent with the Higgs boson mass at around 126 GeV can be tested through the stable stau searches at the 14 TeV run of the LHC. The gravitino is a viable candidate for a dark matter. We also give a short discussion on a possible connection of our model to the recently discovered x-ray line signal at 3.5 keV in the X-ray Multi-Mirror Mission Newton x-ray observatory data.

  13. The phosphatidylserine receptor TIM-4 does not mediate direct signaling.

    PubMed

    Park, Daeho; Hochreiter-Hufford, Amelia; Ravichandran, Kodi S

    2009-02-24

    Engulfment of apoptotic cells is an active process coordinated by receptors on phagocytes and ligands on apoptotic cells [1]. Phosphatidylserine (PtdSer) is a key ligand on apoptotic cells, and recently three PtdSer recognition receptors have been identified, namely, TIM-4, BAI1, and Stabilin-2 [1-6]. Whereas BAI1 is dependent on the ELMO1/Dock180/Rac signaling module, and Stablilin-2 appears to use the intracellular adaptor GULP [2, 3, 7], little is known about how TIM-4 transduces signals downstream of PtdSer recognition [8]. To test the role of known engulfment signaling pathways in TIM-4-mediated engulfment, we used a combination of dominant-negative mutants, knockdown of specific signaling proteins, and knockout cell lines. TIM-4 appears to be largely independent of the two known engulfment signaling pathways [7, 9-17], yet the TIM-4-mediated uptake is inhibited by cytoskeleton disrupting drugs. Remarkably, a version of TIM-4 lacking its cytoplasmic tail promoted corpse uptake via PtdSer recognition. Moreover, replacement of the transmembrane region of TIM-4 with a glycophosphatidylinositol anchor still promoted engulfment comparable to wild-type TIM-4. Thus, the transmembrane region and cytoplasmic tail of TIM-4 are dispensable for apoptotic cell engulfment, and we propose that TIM-4 is a PtdSer tethering receptor without any direct signaling of its own. PMID:19217291

  14. Pollen Allergens for Molecular Diagnosis.

    PubMed

    Pablos, Isabel; Wildner, Sabrina; Asam, Claudia; Wallner, Michael; Gadermaier, Gabriele

    2016-04-01

    Pollen allergens are one of the main causes of type I allergies affecting up to 30 % of the population in industrialized countries. Climatic changes affect the duration and intensity of pollen seasons and may together with pollution contribute to increased incidences of respiratory allergy and asthma. Allergenic grasses, trees, and weeds often present similar habitats and flowering periods compromising clinical anamnesis. Molecule-based approaches enable distinction between genuine sensitization and clinically mostly irrelevant IgE cross-reactivity due to, e. g., panallergens or carbohydrate determinants. In addition, sensitivity as well as specificity can be improved and lead to identification of the primary sensitizing source which is particularly beneficial regarding polysensitized patients. This review gives an overview on relevant pollen allergens and their usefulness in daily practice. Appropriate allergy diagnosis is directly influencing decisions for therapeutic interventions, and thus, reliable biomarkers are pivotal when considering allergen immunotherapy in the context of precision medicine. PMID:27002515

  15. Pollen (quick guide)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    What is pollen, and is it haploid or diploid? Pollen is a crucial stage of the plant life cycle — without pollen there will be no seed. When someone says “Think of a plant,” the plant you think of (whether it’s a tree, a tomato plant, or a geranium) is a sporophyte. Most land plants are sporophytes...

  16. Polyamines in Pollen: From Microsporogenesis to Fertilization

    PubMed Central

    Aloisi, Iris; Cai, Giampiero; Serafini-Fracassini, Donatella; Del Duca, Stefano

    2016-01-01

    The entire pollen life span is driven by polyamine (PA) homeostasis, achieved through fine regulation of their biosynthesis, oxidation, conjugation, compartmentalization, uptake, and release. The critical role of PAs, from microsporogenesis to pollen–pistil interaction during fertilization, is suggested by high and dynamic transcript levels of PA biosynthetic genes, as well as by the activities of the corresponding enzymes. Moreover, exogenous supply of PAs strongly affects pollen maturation and pollen tube elongation. A reduction of endogenous free PAs impacts pollen viability both in the early stages of pollen development and during fertilization. A number of studies have demonstrated that PAs largely function by modulating transcription, by structuring pollen cell wall, by modulating protein (mainly cytoskeletal) assembly as well as by modulating the level of reactive oxygen species. Both free low-molecular weight aliphatic PAs, and PAs conjugated to proteins and hydroxyl-cinnamic acids take part in these complex processes. Here, we review both historical and recent evidence regarding molecular events underlying the role of PAs during pollen development. In the concluding remarks, the outstanding issues and directions for future research that will further clarify our understanding of PA involvement during pollen life are outlined. PMID:26925074

  17. Direct contact between dendritic cells and bronchial epithelial cells inhibits T cell recall responses towards mite and pollen allergen extracts in vitro.

    PubMed

    Papazian, D; Wagtmann, V R; Hansen, S; Würtzen, P A

    2015-08-01

    Airway epithelial cells (AECs) form a polarized barrier along the respiratory tract. They are the first point of contact with airborne antigens and are able to instruct resident immune cells to mount appropriate immune responses by either soluble or contact-dependent mechanisms. We hypothesize that a healthy, polarized epithelial cell layer inhibits inflammatory responses towards allergens to uphold homeostasis. Using an in-vitro co-culture model of the airway epithelium, where a polarized cell layer of bronchial epithelial cells can interact with dendritic cells (DCs), we have investigated recall T cell responses in allergic patients sensitized to house dust mite, grass and birch pollen. Using allergen extract-loaded DCs to stimulate autologous allergen-specific T cell lines, we show that AEC-imprinted DCs inhibit T cell proliferation significantly of Bet v 1-specific T cell lines as well as decrease interleukin (IL)-5 and IL-13 production, whereas inhibition of Phl p 5-specific T cells varied between different donors. Stimulating autologous CD4(+) T cells from allergic patients with AEC-imprinted DCs also inhibited proliferation significantly and decreased production of both T helper type 1 (Th1) and Th2 cytokines upon rechallenge. The inhibitory effects of AECs' contact with DCs were absent when allergen extract-loaded DCs had been exposed only to AECs supernatants, but present after direct contact with AECs. We conclude that direct contact between DCs and AECs inhibits T cell recall responses towards birch, grass and house dust mite allergens in vitro, suggesting that AECs-DC contact in vivo constitute a key element in mucosal homeostasis in relation to allergic sensitisation. PMID:25707463

  18. A Glycosyltransferase from Nicotiana alata Pollen Mediates Synthesis of a Linear (1,5)-α-L-Arabinan When Expressed in Arabidopsis1[OPEN

    PubMed Central

    Ho, Yin Ying; Moller, Isabel E.; Koh, Poh-Ling; Bacic, Antony

    2016-01-01

    The walls of Nicotiana alata pollen tubes contain a linear arabinan composed of (1,5)-α-linked arabinofuranose residues. Although generally found as a side chain on the backbone of the pectic polysaccharide rhamnogalacturonan I, the arabinan in N. alata pollen tubes is considered free, as there is no detectable rhamnogalacturonan I in these walls. Carbohydrate-specific antibodies detected arabinan epitopes at the tip and along the shank of N. alata pollen tubes that are predominantly part of the primary layer of the bilayered wall. A sequence related to ARABINAN DEFICIENT1 (AtARAD1), a presumed arabinan arabinosyltransferase from Arabidopsis (Arabidopsis thaliana), was identified by searching an N. alata pollen transcriptome. Transcripts for this ARAD1-like sequence, which we have named N. alata ARABINAN DEFICIENT-LIKE1 (NaARADL1), accumulate in various tissues, most abundantly in the pollen grain and tube, and encode a protein that is a type II membrane protein with its catalytic carboxyl terminus located in the Golgi lumen. The NaARADL1 protein can form homodimers when transiently expressed in Nicotiana benthamiana leaves and heterodimers when coexpressed with AtARAD1. The expression of NaARADL1 in Arabidopsis led to plants with more arabinan in their walls and that also exuded a guttation fluid rich in arabinan. Chemical and enzymatic characterization of the guttation fluid showed that a soluble, linear α-(1,5)-arabinan was the most abundant polymer present. These results are consistent with NaARADL1 having an arabinan (1,5)-α-arabinosyltransferase activity. PMID:26850276

  19. Interferon-Gamma Directly Mediates Developmental Biliary Defects

    PubMed Central

    Cui, Shuang; EauClaire, Steven F.

    2013-01-01

    Abstract Biliary atresia (BA) is the most common identifiable hepatobiliary disease affecting infants, in which there are defects in intra- and extrahepatic bile ducts and progressive fibrosis. Activation of interferon-gamma (IFNγ) appears to be critical in both patients with BA and in rodent models of BA. We have recently reported a zebrafish model of biliary disease that shares features with BA, in which inhibition of DNA methylation leads to intrahepatic biliary defects and activation of IFNγ target genes. Here we report that ifng genes are hypomethylated and upregulated in zebrafish larvae treated with azacytidine (azaC), an inhibitor of DNA methylation. Injection of IFNγ protein into developing zebrafish larvae leads to biliary defects, suggesting that activation of the IFNγ pathway is sufficient to cause developmental biliary defects. These defects are associated with decreased cholangiocyte proliferation and with a decrease in the expression of vhnf1 (hnf1b, tcf2), which encodes a homeodomain protein with previously reported roles in biliary development in multiple models. These results support an importance of IFNγ in mediating biliary defects, and also demonstrate the feasibility of direct injection of intact protein into developing zebrafish larvae. PMID:23448251

  20. Pollen flow of wheat under natural conditions in the Huanghuai River Wheat Region, China.

    PubMed

    Sun, Ai-Qing; Zhang, Chun-Qing; Wu, Cheng-Lai; Gao, Qing-Rong

    2015-01-01

    The transgenic pollen spread is the main pathway of transgenic plant gene flow. The maximum distance of pollen dispersal (horizontal), the spatial dynamics of pollen movement (vertical), and the patterns of pollen dispersal are important considerations in biosafety assessments of genetically modified crops. To evaluate wheat (Triticum aestivum) pollen dispersal, we measured the pollen suspension velocity and analyzed pollen dispersal patterns under natural conditions in the Huanghuai River wheat-growing region in 2009. The pollen suspension velocity was 0.3-0.4 m/s. The highest pollen densities were detected in the north, northwest, and south of the pollen source. Pollen was dispersed over distances greater than 245 m in the northwest and northeast directions. At the pollen source center, pollen density decreased with increasing vertical height. In the north of the pollen source, the pollen density from 65 m to 225 m showed a wave-mode decrease with increasing height. The horizontal transport of pollen over longer distances fitted polynomial equations. In the north, the pollen density was highest at 45 m from the pollen source, and decreased with increasing distance. In the northwest, the pollen density showed a double-peak trend. In the northeast, pollen density was highest from 45 m to 125 m from the source. Wind speeds greater than the pollen suspension velocity and the duration of continuous gusts were the main factors affecting pollen dispersal. This information will be useful for determining the spatial isolation distances for hybrid seed production and for the commercial production of transgenic wheat. PMID:25658025

  1. Occupational Allergy to Peach (Prunus persica) Tree Pollen and Potential Cross-Reactivity between Rosaceae Family Pollens.

    PubMed

    Jiang, Nannan; Yin, Jia; Mak, Philip; Wen, Liping

    2015-10-01

    Orchard workers in north China are highly exposed to orchard pollens, especially peach and other Rosaceae family pollens during pollination season. The aim of this study was to investigate whether occupational allergy to peach tree pollen as a member of Rosaceae family is IgE-mediated and to evaluate the cross-reactivity among Rosaceae family pollens. Allergen skin test and conjunctival challenge test were performed; enzyme linked immune-sorbent assay (ELISA), inhibiting ELISA, western immunoblotting and inhibiting western immunoblotting were done with Rosaceae family orchard pollens, including peach, apricot, cherry, apple and pear tree pollens. Mass spectrometry was also performed to probe the main allergen component and cross-reactive protein. Sensitizations to peach pollen were found in both skin test and conjunctival challenge in the patients. Serum specific IgE to three pollens (peach, apricot and cherry) were detected through ELISA. When peach pollen used as solid phase, ELISA inhibition revealed other four kinds of pollens capable of inducing partial to strong inhibitions (45% to 87%), with the strongest inhibition belonging to apricot pollen (87%). Western blotting showed predominant IgE binding to a 20 KD protein among these pollens, which appeared to be a cross-reactive allergen component through western blotting inhibition. It was recognized as a protein homologous to glutathione s-transferase 16 from Arabidopsis thaliana. Peach and other Rosaceae family tree pollen may serve as a potential cause of IgE mediated occupational respiratory disease in orchard workers in north China. PMID:26742437

  2. Long-distance GM pollen movement of creeping bentgrass using modeled wind trajectory analysis.

    PubMed

    Van de Water, Peter K; Watrud, Lidia S; Lee, E Henry; Burdick, Connie; King, George A

    2007-06-01

    The importance of understanding the role of atmospheric conditions in pollen dispersal has grown in recent years with increased field-testing of genetically modified (GM) crop plants. An atmospheric model was used to characterize wind trajectories at 10 m and 100 m above GM pollen source fields located within a 4452-ha "control" area north of Madras, Oregon, USA, designated by the Oregon Department of Agriculture (ODA). The area was used in 2003 for the growth of GM creeping bentgrass (Agrostis stolonifera) engineered to be resistant to glyphosate herbicide. The presence of the GM gene (CP4 EPSPS) provided a distinct selectable marker for pollen-mediated gene flow to sentinel and resident Agrostis spp. plants. Linkage of GM gene presence with wind flow characteristics over the "control" area became essential to understand the timing and processes leading to long-distance transport of this pollen. Wind trajectories showed a general pattern of northwest to southeast air movement. Trajectory travel distances calculated hourly from 06:00 hours to 15:00 hours during the 2003 pollination period (15 June-15 July) showed movement up to 15 km from the "control" area's center by the first hour. Maximum travel distances increased to 40 and 55 km after two and three hours from release, respectively. Calculated wind trajectory positions corresponded with observed long-distance pollen-mediated gene flow in the seedlings of sentinel and resident plants. The highest correlations were found during the late morning hours. Back-calculated wind trajectories from sentinel and resident locations with GM-gene-positive progeny suggested that most successful fertilizations occurred in the direction of prevailing winds during late June 2003. The occurrence of positive progeny from sentinel plants, upwind of the "control" area during this period, indicated the additional influence of local topography on pollen dispersal. PMID:17555232

  3. The pollen enigma: modulation of the allergic immune response by non-allergenic, pollen-derived compounds.

    PubMed

    Gilles, Stefanie; Behrendt, Heidrun; Ring, Johannes; Traidl-Hoffmann, Claudia

    2012-01-01

    The question what makes an allergen an allergen puzzled generations of researchers. Pollen grains of anemophilous plants are the most important allergen carriers in ambient air, and pollinosis is a highly prevalent multi-organ disease in civilized countries. In the past, research on the allergenicity of pollen has mainly focused on elucidating genetic predisposing factors and on defining certain structural characteristics of pollen derived allergens. Recently, studies extended to the analysis of non-allergenic, adjuvant mediators co-released from pollen. Besides active proteases and oxidases, extracts of pollen contain low molecular weight molecules like pollen-associated lipid mediators or adenosine exhibiting a potential to stimulate and modulate cultured human immune cells. This article reviews our current knowledge on non-allergenic, protein and non-protein compounds from pollen and their in vitro and in vivo effects on the allergic immune response. To ultimately judge the physiological relevance of these compounds, a systematic approach will be needed comparing their releasability, content and activity in different, allergenic and non-allergenic, pollen species. System biology such as proteome and metabolome analysis will be a useful future approach to better understand pollen biology. PMID:22390694

  4. Growth of Pollen Tubes of Papaver rhoeas Is Regulated by a Slow-Moving Calcium Wave Propagated by Inositol 1,4,5-Trisphosphate.

    PubMed Central

    Franklin-Tong, V. E.; Drobak, B. K.; Allan, A. C.; Watkins, PAC.; Trewavas, A. J.

    1996-01-01

    A signaling role for cytosolic free Ca2+ ([Ca2+]i) in regulating Papaver rhoeas pollen tube growth during the self-incompatibility response has been demonstrated previously. In this article, we investigate the involvement of the phosphoinositide signal transduction pathway in Ca2+-mediated pollen tube inhibition. We demonstrate that P. rhoeas pollen tubes have a Ca2+-dependent polyphosphoinositide-specific phospholipase C activity that is inhibited by neomycin. [Ca2+]i imaging after photolysis of caged inositol (1,4,5)-trisphosphate (Ins[1,4,5]P3) in pollen tubes demonstrated that Ins(1,4,5)P3 could induce Ca2+ release, which was inhibited by heparin and neomycin. Mastoparan, which stimulated Ins(1,4,5)P3 production, also induced a rapid increase in Ca2+, which was inhibited by neomycin. These data provide direct evidence for the involvement of a functional phosphoinositide signal-transducing system in the regulation of pollen tube growth. We suggest that the observed Ca2+ increases are mediated, at least in part, by Ins(1,4,5)P3-induced Ca2+ release. Furthermore, we provide data suggesting that Ca2+ waves, which have not previously been reported in plant cells, can be induced in pollen tubes. PMID:12239415

  5. Dating Fossil Pollen: A Simulation.

    ERIC Educational Resources Information Center

    Sheridan, Philip

    1992-01-01

    Describes a hands-on simulation in which students determine the age of "fossil" pollen samples based on the pollen types present when examined microscopically. Provides instructions for the preparation of pollen slides. (MDH)

  6. Contrasts between the phylogeographic patterns of chloroplast and nuclear DNA highlight a role for pollen-mediated gene flow in preventing population divergence in an East Asian temperate tree.

    PubMed

    Bai, Wei-Ning; Wang, Wen-Ting; Zhang, Da-Yong

    2014-12-01

    Plant phylogeographic studies in East Asia have provided support for the biogeographic hypothesis that the complex landforms and climate of this region have provided substantial opportunities for allopatric speciation. However, most of these studies have been based on maternally inherited chloroplast DNA (cpDNA) markers and were therefore unable to reveal the role of pollen-mediated gene flow in preventing population divergence. Here, we investigate the phylogeography of the Chinese walnut Juglans cathayensis, a temperate deciduous tree widely distributed across disjunct montane sites in subtropical China. We genotyped 19 populations using seven cpDNA fragments and ten nuclear microsatellite loci and modeled the ecological niche of J. cathayensis. CpDNA analysis identified a total of nine haplotypes, and each of the 19 sampled populations was fixed for a single haplotype, displaying a prominent phylogeographic structure. The results of ecological niche modeling indicated that J. cathayensis populations survived the last glaciation in situ, although they were probably more fragmented than today. In contrast, we detected a much weaker, but nonetheless clear, genetic structure based on nuclear microsatellite data. Our study demonstrates how extensive pollen flow can erase the genetic imprint of long-term refugial isolation in maternal lineages, effectively preventing population differentiation in temperate, particularly wind-pollinated, forest trees in subtropical China. PMID:25196588

  7. Allergies, asthma, and pollen

    MedlinePlus

    ... Some trees Some grasses Weeds Ragweed Watch the weather and the season The amount of pollen in the air can affect whether you or your child has hay fever and asthma symptoms. On hot, dry, windy days, more pollen is in the air. ...

  8. Chilean and Southeast Pacific paleoclimate variations during the last glacial cycle: directly correlated pollen and δ18O records from ODP Site 1234

    NASA Astrophysics Data System (ADS)

    Heusser, Linda; Heusser, Cal; Mix, Alan; McManus, Jerry

    2006-12-01

    Joint pollen and oxygen isotope data from Ocean Drilling Program Site 1234 in the southeast Pacific provide the first, continuous record of temperate South American vegetation and climate from the last 140 ka. Located at ˜36°S, ˜65 km offshore of Concepcion, Chile, Site 1234 monitors the climatic transition zone between northern semi-arid, summer dry-winter wet climate and southern year-round, rainy, cool temperate climate. Dominance of onshore winds suggests that pollen preserved here reflects transport to the ocean via rivers that drain the region and integrate conditions from the coastal mountains to the Andean foothills. Down-hole changes in diagnostic pollen assemblages from xeric lowland deciduous forest (characterized by grasses, herbs, ferns, and trees such as deciduous beech, Nothofagus obliqua), mesic Valdivian Evergreen Forest (including conifers such as the endangered Prumnopitys andina), and Subantarctic Evergreen Rainforest (comprised primarily of southern beech, N. dombeyi) reveal large rapid shifts that likely reflect latitudinal movements in atmospheric circulation and storm tracks associated with the southern westerly winds. During glacial intervals (MIS 2-4, and 6), rainforests and parkland dominated by Nothofagus moved northward into the region. At the MIS 6/5e transition, coeval with the rapid shift to lower isotopic values, rainforest vegetation was rapidly replaced by xeric plant communities associated with Mediterranean-type climate. An increased prominence of halophytic vegetation suggests that MIS 5e was more arid and possibly warmer than MIS 1. Although rainforest pollen rises again at the end of MIS 5e, lowland deciduous forest pollen persists through MIS 5d and 5c, into MIS 5b. Substantial millennial-scale variations occur in both interglacial and glacial regimes, attesting to the sensitivity of the southern westerly belt to climate change. Comparison of the cool, mesic N. dombeyi rainforest assemblage from Site 1234 with δ18O in

  9. Links between pollen, atopy and the asthma epidemic.

    PubMed

    Taylor, Philip E; Jacobson, Kraig W; House, James M; Glovsky, M Michael

    2007-01-01

    Pollen allergy has been found in 80-90% of childhood asthmatics and 40-50% of adult-onset asthmatics. Despite the high prevalence of atopy in asthmatics, a causal relationship between the allergic response and asthma has not been clearly established. Pollen grains are too large to penetrate the small airways where asthma occurs. Yet pollen cytoplasmic fragments are respirable and are likely correlated with the asthmatic response in allergic asthmatics. In this review, we outline the mechanism of pollen fragmentation and possible pathophysiology of pollen fragment-induced asthma. Pollen grains rupture within the male flowers and emit cytoplasmic debris when winds or other disturbances disperse the pollen. Peak levels of grass and birch pollen allergens in the atmosphere correlated with the occurrence of moist weather conditions during the flowering period. Thunderstorm asthma epidemics may be triggered by grass pollen rupture in the atmosphere and the entrainment of respirable-sized particles in the outflows of air masses at ground level. Pollen contains nicotinamide adenine dinucleotide phosphate (reduced) oxidases and bioactive lipid mediators which likely contribute to the inflammatory response. Several studies have examined synergistic effects and enhanced immune response from interaction in the atmosphere, or from co-deposition in the airways, of pollen allergens, endogenous pro-inflammatory agents, and the particulate and gaseous fraction of combustion products. Pollen and fungal fragments also contain compounds that can suppress reactive oxidants and quench free radicals. It is important to know more about how these substances interact to potentially enhance, or even ameliorate, allergic asthma. PMID:17536216

  10. Pollen Production, Microsporangium Dehiscence and Pollen Flow in Himalayan Cedar (Cedrus deodara Roxb. ex D. Don)

    PubMed Central

    KHANDURI, V. P.; SHARMA, C. M.

    2002-01-01

    Microsporangium dehiscence, pollen production and dispersal were studied in Himalayan cedar (Cedrus deodara) during 1998 and 1999. Microsporangium dehiscence showed diurnal periodicity and was found to be related to air temperature and relative air humidity, with a strobilus taking 2 d to dehisce completely in warmer conditions and 3 d in cooler ones. The frequency of flowering in C. deodara was highly variable during the two successive years; however, cyclical production of pollen grains was observed in 50 % of the trees. The maximum concentration of pollen grains in the air was found between 1200 and 1600 h, and this period was also noted to be the best time for pollination. Studying migration of pollen grains from isolated single trees in three directions showed that migration was not uniform in all directions. Long‐distance transport of pollen grains was observed in the downhill direction. However, in the uphill and horizontal directions grains could travel only up to 97·5 and 195·1 m, respectively, and the frequency of pollen grains to the source frequency at these distances was only 1·9 and 2·5 %, respectively. The results suggest that an isolation barrier of 190 m may be considered as a minimum for the management of deodar seed orchards. PMID:12099533

  11. Direct measurement of DNA-mediated adhesion between lipid bilayers.

    PubMed

    Shimobayashi, S F; Mognetti, B M; Parolini, L; Orsi, D; Cicuta, P; Di Michele, L

    2015-06-28

    Multivalent interactions between deformable mesoscopic units are ubiquitous in biology, where membrane macromolecules mediate the interactions between neighbouring living cells and between cells and solid substrates. Lately, analogous artificial materials have been synthesised by functionalising the outer surface of compliant Brownian units, for example emulsion droplets and lipid vesicles, with selective linkers, in particular short DNA sequences. This development extended the range of applicability of DNA as a selective glue, originally applied to solid nano and colloidal particles. On very deformable lipid vesicles, the coupling between statistical effects of multivalent interactions and mechanical deformation of the membranes gives rise to complex emergent behaviours, as we recently contributed to demonstrate [Parolini et al., Nat. Commun., 2015, 6, 5948]. Several aspects of the complex phenomenology observed in these systems still lack a quantitative experimental characterisation and a fundamental understanding. Here we focus on the DNA-mediated multivalent interactions of a single liposome adhering to a flat supported bilayer. This simplified geometry enables the estimate of the membrane tension induced by the DNA-mediated adhesive forces acting on the liposome. Our experimental investigation is completed by morphological measurements and the characterisation of the DNA-melting transition, probed by in situ Förster Resonant Energy Transfer spectroscopy. Experimental results are compared with the predictions of an analytical theory that couples the deformation of the vesicle to a full description of the statistical mechanics of mobile linkers. With at most one fitting parameter, our theory is capable of semi-quantitatively matching experimental data, confirming the quality of the underlying assumptions. PMID:25989828

  12. Effect of water absorption on pollen adhesion.

    PubMed

    Lin, Haisheng; Lizarraga, Leonardo; Bottomley, Lawrence A; Carson Meredith, J

    2015-03-15

    Pollens possess a thin liquid coating, pollenkitt, which plays a major role in adhesion by forming capillary menisci at interfaces. Unfortunately, the influence of humidity on pollenkitt properties and capillary adhesion is unknown. Because humidity varies widely in the environment, the answers have important implications for better understanding plant reproduction, allergy and asthma, and pollen as atmospheric condensation nuclei. Here, pollenkitt-mediated adhesion of sunflower pollen to hydrophilic and hydrophobic surfaces was measured as a function of humidity. The results quantify for the first time the significant water absorption of pollenkitt and the resulting complex dependence of adhesion on humidity. On hydrophilic Si, adhesion increased with increasing RH for pollens with or without pollenkitt, up to 200nN at 70% RH. In contrast, on hydrophobic PS, adhesion of pollenkitt-free pollen is independent of RH. Surprisingly, when pollenkitt was present adhesion forces on hydrophobic PS first increased with RH up to a maximum value at 35% RH (∼160nN), and then decreased with further increases in RH. Independent measurement of pollenkitt properties is used with models of capillary adhesion to show that humidity-dependent changes in pollenkitt wetting and viscosity are responsible for this complex adhesion behavior. PMID:25524008

  13. Direction Selectivity Mediated by Adaptation in the Owl's Inferior Colliculus

    PubMed Central

    Peña, José Luis

    2013-01-01

    Motion direction is a crucial cue for predicting future states in natural scenes. In the auditory system, the mechanisms that confer direction selectivity to neurons are not well understood. Neither is it known whether sound motion is encoded independently of stationary sound location. Here we investigated these questions in neurons of the owl's external nucleus of the inferior colliculus, where auditory space is represented in a map. Using a high-density speaker array, we show that the preferred direction and the degree of direction selectivity can be predicted by response adaptation to sounds moving over asymmetric spatial receptive fields. At the population level, we found that preference for sounds moving toward frontal space increased with eccentricity in spatial tuning. This distribution was consistent with larger receptive-field asymmetry in neurons tuned to more peripheral auditory space. A model of suppression based on spatiotemporal summation predicted the observations. Thus, response adaptation and receptive-field shape can explain direction selectivity to acoustic motion and an orderly distribution of preferred direction. PMID:24305813

  14. Direct observation of defect-mediated cluster nucleation

    NASA Astrophysics Data System (ADS)

    Kaiser, U.; Muller, D. A.; Grazul, J. L.; Chuvilin, A.; Kawasaki, M.

    2002-10-01

    Ion implantation is widely used to introduce electrically or optically active dopant atoms into semiconductor devices. At high concentrations, the dopants can cluster and ultimately form deactivating precipitates, but deliberate nanocrystal formation offers an approach to self-assembled device fabrication. However, there is very little understanding of the early stages of how these precipitates nucleate and grow, in no small part because it requires imaging an inhomogenous distribution of defects and dopant atoms buried inside the host material. Here we demonstrate this, and address the long-standing question of whether the cluster nucleation is defect-mediated or spontaneous. Atomic-resolution illustrations are given for the chemically dissimilar cases of erbium and germanium implanted into silicon carbide. Whereas interstitial loops act as nucleation sites in both cases, the evolution of nanocrystals is strikingly different: Erbium is found to gather in lines, planes and finally three-dimensional precipitates, whereas germanium favours compact, three-dimensional structures.

  15. Direct observation of defect-mediated cluster nucleation.

    PubMed

    Kaiser, U; Muller, D A; Grazul, J L; Chuvilin, A; Kawasaki, M

    2002-10-01

    Ion implantation is widely used to introduce electrically or optically active dopant atoms into semiconductor devices. At high concentrations, the dopants can cluster and ultimately form deactivating precipitates, but deliberate nanocrystal formation offers an approach to self-assembled device fabrication. However, there is very little understanding of the early stages of how these precipitates nucleate and grow, in no small part because it requires imaging an inhomogenous distribution of defects and dopant atoms buried inside the host material. Here we demonstrate this, and address the long-standing question of whether the cluster nucleation is defect-mediated or spontaneous. Atomic-resolution illustrations are given for the chemically dissimilar cases of erbium and germanium implanted into silicon carbide. Whereas interstitial loops act as nucleation sites in both cases, the evolution of nanocrystals is strikingly different: Erbium is found to gather in lines, planes and finally three-dimensional precipitates, whereas germanium favours compact, three-dimensional structures. PMID:12618823

  16. Cytomechanical Properties of Papaver Pollen Tubes Are Altered after Self-Incompatibility Challenge

    PubMed Central

    Geitmann, Anja; McConnaughey, William; Lang-Pauluzzi, Ingeborg; Franklin-Tong, Vernonica E.; Emons, Anne Mie C.

    2004-01-01

    Self-incompatibility (SI) in Papaver rhoeas triggers a ligand-mediated signal transduction cascade, resulting in the inhibition of incompatible pollen tube growth. Using a cytomechanical approach we have demonstrated that dramatic changes to the mechanical properties of incompatible pollen tubes are stimulated by SI induction. Microindentation revealed that SI resulted in a reduction of cellular stiffness and an increase in cytoplasmic viscosity. Whereas the former cellular response is likely to be the result of a drop in cellular turgor, we hypothesize that the latter is caused by as yet unidentified cross-linking events. F-actin rearrangements, a characteristic phenomenon for SI challenge in Papaver, displayed a spatiotemporal gradient along the pollen tube; this suggests that signal propagation occurs in a basipetal direction. However, unexpectedly, local application of SI inducing S-protein did not reveal any evidence for localized signal perception in the apical or subapical regions of the pollen tube. To our knowledge this represents the first mechanospatial approach to study signal propagation and cellular responses in a well-characterized plant cell system. Our data provide the first evidence for mechanical changes induced in the cytoplasm of a plant cell stimulated by a defined ligand. PMID:15111444

  17. A CYSTEINE-RICH EXTRACELLULAR PROTEIN, LAT52, INTERACTS WITH THE EXTRACVELLULAR DOMAIN OF THE POLLEN RECEPTOR KINASE LEPRK2

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pollen germination and pollen tube growth are thought to require extracellular cues, but how these cues are perceived and transduced remains largely unknown. Pollen receptor kinases are plausible candidates for this role; they might bind extracellular ligands and thereby mediate cytoplasmic events r...

  18. A Model of Direct Gauge Mediation of Supersymmetry Breaking

    NASA Astrophysics Data System (ADS)

    Murayama, Hitoshi

    1997-07-01

    We present the first phenomenologically viable model of gauge meditation of supersymmetry breaking without a messenger sector or gauge singlet fields. The standard model gauge groups couple directly to the sector which breaks supersymmetry dynamically. Despite the direct coupling, it can preserve perturbative gauge unification thanks to the inverted hierarchy mechanism. There is no dangerous negative contribution to m2q~, m2l~ due to two-loop renormalization group equation. The potentially nonuniversal supergravity contribution to m2q~ and m2l~ can be suppressed enough. The model is completely chiral, and one does not need to forbid mass terms for the messenger fields by hand. Cosmology of the model is briefly discussed.

  19. A Model of Direct Gauge Mediation of Supersymmetry Breaking

    SciTech Connect

    Murayama, H. |

    1997-07-01

    We present the first phenomenologically viable model of gauge meditation of supersymmetry breaking without a messenger sector or gauge singlet fields. The standard model gauge groups couple directly to the sector which breaks supersymmetry dynamically. Despite the direct coupling, it can preserve perturbative gauge unification thanks to the inverted hierarchy mechanism. There is no dangerous negative contribution to m{sup 2}{sub {tilde q}} , m{sup 2}{sub {tilde l}} due to two-loop renormalization group equation. The potentially nonuniversal supergravity contribution to m{sup 2}{sub {tilde q}} and m{sup 2}{sub {tilde l}} can be suppressed enough. The model is completely chiral, and one does not need to forbid mass terms for the messenger fields by hand. Cosmology of the model is briefly discussed. {copyright} {ital 1997} {ital The American Physical Society}

  20. Direct observation of intermolecular interactions mediated by hydrogen bonding

    NASA Astrophysics Data System (ADS)

    De Marco, Luigi; Thämer, Martin; Reppert, Mike; Tokmakoff, Andrei

    2014-07-01

    Although intermolecular interactions are ubiquitous in physicochemical phenomena, their dynamics have proven difficult to observe directly, and most experiments rely on indirect measurements. Using broadband two-dimensional infrared spectroscopy (2DIR), we have measured the influence of hydrogen bonding on the intermolecular vibrational coupling between dimerized N-methylacetamide molecules. In addition to strong intramolecular coupling between N-H and C=O oscillators, cross-peaks in the broadband 2DIR spectrum appearing upon dimerization reveal strong intermolecular coupling that changes the character of the vibrations. In addition, dimerization changes the effects of intramolecular coupling, resulting in Fermi resonances between high and low-frequency modes. These results illustrate how hydrogen bonding influences the interplay of inter- and intramolecular vibrations, giving rise to correlated nuclear motions and significant changes in the vibrational structure of the amide group. These observations have direct impact on modeling and interpreting the IR spectra of proteins. In addition, they illustrate a general approach to direct molecular characterization of intermolecular interactions.

  1. Direct observation of intermolecular interactions mediated by hydrogen bonding

    SciTech Connect

    De Marco, Luigi; Reppert, Mike; Thämer, Martin; Tokmakoff, Andrei

    2014-07-21

    Although intermolecular interactions are ubiquitous in physicochemical phenomena, their dynamics have proven difficult to observe directly, and most experiments rely on indirect measurements. Using broadband two-dimensional infrared spectroscopy (2DIR), we have measured the influence of hydrogen bonding on the intermolecular vibrational coupling between dimerized N-methylacetamide molecules. In addition to strong intramolecular coupling between N–H and C=O oscillators, cross-peaks in the broadband 2DIR spectrum appearing upon dimerization reveal strong intermolecular coupling that changes the character of the vibrations. In addition, dimerization changes the effects of intramolecular coupling, resulting in Fermi resonances between high and low-frequency modes. These results illustrate how hydrogen bonding influences the interplay of inter- and intramolecular vibrations, giving rise to correlated nuclear motions and significant changes in the vibrational structure of the amide group. These observations have direct impact on modeling and interpreting the IR spectra of proteins. In addition, they illustrate a general approach to direct molecular characterization of intermolecular interactions.

  2. Cyclic nucleotide-gated channel 18 is an essential Ca2+ channel in pollen tube tips for pollen tube guidance to ovules in Arabidopsis.

    PubMed

    Gao, Qi-Fei; Gu, Li-Li; Wang, Hui-Qin; Fei, Cui-Fang; Fang, Xiang; Hussain, Jamshaid; Sun, Shu-Jing; Dong, Jing-Yun; Liu, Hongtao; Wang, Yong-Fei

    2016-03-15

    In flowering plants, pollen tubes are guided into ovules by multiple attractants from female gametophytes to release paired sperm cells for double fertilization. It has been well-established that Ca(2+) gradients in the pollen tube tips are essential for pollen tube guidance and that plasma membrane Ca(2+) channels in pollen tube tips are core components that regulate Ca(2+) gradients by mediating and regulating external Ca(2+) influx. Therefore, Ca(2+) channels are the core components for pollen tube guidance. However, there is still no genetic evidence for the identification of the putative Ca(2+) channels essential for pollen tube guidance. Here, we report that the point mutations R491Q or R578K in cyclic nucleotide-gated channel 18 (CNGC18) resulted in abnormal Ca(2+) gradients and strong pollen tube guidance defects by impairing the activation of CNGC18 in Arabidopsis. The pollen tube guidance defects of cngc18-17 (R491Q) and of the transfer DNA (T-DNA) insertion mutant cngc18-1 (+/-) were completely rescued by CNGC18. Furthermore, domain-swapping experiments showed that CNGC18's transmembrane domains are indispensable for pollen tube guidance. Additionally, we found that, among eight Ca(2+) channels (including six CNGCs and two glutamate receptor-like channels), CNGC18 was the only one essential for pollen tube guidance. Thus, CNGC18 is the long-sought essential Ca(2+) channel for pollen tube guidance in Arabidopsis. PMID:26929345

  3. Pollen Tube Discharge Completes the Process of Synergid Degeneration That Is Initiated by Pollen Tube-Synergid Interaction in Arabidopsis1[OPEN

    PubMed Central

    Leydon, Alexander R.; Tsukamoto, Tatsuya; Dunatunga, Damayanthi; Qin, Yuan; Johnson, Mark A.; Palanivelu, Ravishankar

    2015-01-01

    In flowering plant reproduction, pollen tube reception is the signaling system that results in pollen tube discharge, synergid degeneration, and successful delivery of male gametes (two sperm cells) to the site where they can fuse with female gametes (egg cell and central cell). Some molecules required for this complex and essential signaling exchange have been identified; however, fundamental questions about the nature of the interactions between the pollen tube and the synergid cells remain to be clarified. Here, we monitor pollen tube arrival, pollen tube discharge, and synergid degeneration in Arabidopsis (Arabidopsis thaliana) wild type and in male and female gametophytic mutants that disrupt development and function of the gametophytes. By combining assays used previously to study these interactions and an assay that facilitates simultaneous analysis of pollen tube discharge and synergid degeneration, we find that synergid degeneration could be initiated without pollen tube discharge. Our data support the hypothesis that pollen tube-synergid contact, or signaling via secreted molecules, initiates receptive synergid degeneration. We also find that when pollen tubes successfully burst, they always discharge into a degenerated synergid. In addition to this pollen tube-dependent promotion of synergid degeneration, we also show that a basal developmental pathway mediates synergid degeneration in the absence of pollination. Our results are consistent with the model that a complex set of interactions between the pollen tube and synergid cells promote receptive synergid degeneration. PMID:26229050

  4. A direct assessment of realized seed and pollen flow within and between two isolated populations of the food-deceptive orchid Orchis mascula.

    PubMed

    Helsen, K; Meekers, T; Vranckx, G; Roldán-Ruiz, I; Vandepitte, K; Honnay, O

    2016-01-01

    Gene flow can counteract the loss of genetic diversity caused by genetic drift in small populations. For this reason, clearly understanding gene flow patterns is of the highest importance across fragmented landscapes. However, gene flow patterns are not only dependent upon the degree of spatial isolation of fragmented populations, but are also dependent upon the life-history traits of the species. Indeed, habitat fragmentation effects appear especially unpredictable for food-deceptive orchid species, because of their highly specialised seed and pollen dispersal mechanisms. In this study we used amplified fragment length polymorphism markers and subsequent parentage and spatial autocorrelation analysis to quantify the extent and the patterns of realized gene flow within and between two adjacent fragmented populations of the food-deceptive Orchis mascula. We observed considerable gene flow between both populations, occurring mainly through pollen dispersal. Seed dispersal, on the other hand, was mainly limited to the first few meters from the mother plant in both populations, although at least one among-population seed dispersal event was observed. This, in turn, resulted in a significant spatial genetic structure for both populations. Although genetic diversity was high in both populations and mainly outcrossing occurred, reproductive output was strongly skewed toward a limited number of successful adult plants. These observed patterns are likely due to the different pollinator behaviour associated with food-deceptive plants. We conclude that these populations can be considered viable under their current fragmented state. PMID:25941020

  5. Digital Gene Expression Analysis of Populus simonii × P. nigra Pollen Germination and Tube Growth

    PubMed Central

    Zhao, Li-Juan; Yuan, Hong-Mei; Guo, Wen-Dong; Yang, Chuan-Ping

    2016-01-01

    Pollen tubes are an ideal model for the study of cell growth and morphogenesis because of their extreme elongation without cell division; however, the genetic basis of pollen germination and tube growth remains largely unknown. Using the Illumina/Solexa digital gene expression system, we identified 13,017 genes (representing 28.3% of the unigenes on the reference genes) at three stages, including mature pollen, hydrated pollen, and pollen tubes of Populus simonii × P. nigra. Comprehensive analysis of P. simonii × P. nigra pollen revealed dynamic changes in the transcriptome during pollen germination and pollen tube growth (PTG). Gene ontology analysis of differentially expressed genes showed that genes involved in functional categories such as catalytic activity, binding, transporter activity, and enzyme regulator activity were overrepresented during pollen germination and PTG. Some highly dynamic genes involved in pollen germination and PTG were detected by clustering analysis. Genes related to some key pathways such as the mitogen-activated protein kinase signaling pathway, regulation of the actin cytoskeleton, calcium signaling, and ubiquitin-mediated proteolysis were significantly changed during pollen germination and PTG. These data provide comprehensive molecular information toward further understanding molecular mechanisms underlying pollen germination and PTG. PMID:27379121

  6. Characterising dark matter searches at colliders and direct detection experiments: Vector mediators

    SciTech Connect

    Buchmueller, Oliver; Dolan, Matthew J.; Malik, Sarah A.; McCabe, Christopher

    2015-01-09

    We introduce a Minimal Simplified Dark Matter (MSDM) framework to quantitatively characterise dark matter (DM) searches at the LHC. We study two MSDM models where the DM is a Dirac fermion which interacts with a vector and axial-vector mediator. The models are characterised by four parameters: mDM, Mmed , gDM and gq, the DM and mediator masses, and the mediator couplings to DM and quarks respectively. The MSDM models accurately capture the full event kinematics, and the dependence on all masses and couplings can be systematically studied. The interpretation of mono-jet searches in this framework can be used to establish an equal-footing comparison with direct detection experiments. For theories with a vector mediator, LHC mono-jet searches possess better sensitivity than direct detection searches for light DM masses (≲5 GeV). For axial-vector mediators, LHC and direct detection searches generally probe orthogonal directions in the parameter space. We explore the projected limits of these searches from the ultimate reach of the LHC and multi-ton xenon direct detection experiments, and find that the complementarity of the searches remains. In conclusion, we provide a comparison of limits in the MSDM and effective field theory (EFT) frameworks to highlight the deficiencies of the EFT framework, particularly when exploring the complementarity of mono-jet and direct detection searches.

  7. Characterising dark matter searches at colliders and direct detection experiments: Vector mediators

    DOE PAGESBeta

    Buchmueller, Oliver; Dolan, Matthew J.; Malik, Sarah A.; McCabe, Christopher

    2015-01-09

    We introduce a Minimal Simplified Dark Matter (MSDM) framework to quantitatively characterise dark matter (DM) searches at the LHC. We study two MSDM models where the DM is a Dirac fermion which interacts with a vector and axial-vector mediator. The models are characterised by four parameters: mDM, Mmed , gDM and gq, the DM and mediator masses, and the mediator couplings to DM and quarks respectively. The MSDM models accurately capture the full event kinematics, and the dependence on all masses and couplings can be systematically studied. The interpretation of mono-jet searches in this framework can be used to establishmore » an equal-footing comparison with direct detection experiments. For theories with a vector mediator, LHC mono-jet searches possess better sensitivity than direct detection searches for light DM masses (≲5 GeV). For axial-vector mediators, LHC and direct detection searches generally probe orthogonal directions in the parameter space. We explore the projected limits of these searches from the ultimate reach of the LHC and multi-ton xenon direct detection experiments, and find that the complementarity of the searches remains. In conclusion, we provide a comparison of limits in the MSDM and effective field theory (EFT) frameworks to highlight the deficiencies of the EFT framework, particularly when exploring the complementarity of mono-jet and direct detection searches.« less

  8. Thunderstorm asthma due to grass pollen.

    PubMed

    Suphioglu, C

    1998-08-01

    It is widely known and accepted that grass pollen is a major outdoor cause of hay fever. Moreover, grass pollen is also responsible for triggering allergic asthma, gaining impetus as a result of the 1987/1989 Melbourne and 1994 London thunderstorm-associated asthma epidemics. However, grass pollen is too large to gain access into the lower airways to trigger the asthmatic response and micronic particles <5 micro m are required to trigger the response. We have successfully shown that ryegrass pollen ruptures upon contact with water, releasing about 700 starch granules which not only contain the major allergen Lol p 5, but have been shown to trigger both in vitro and in vivo IgE-mediated responses. Furthermore, starch granules have been isolated from the Melbourne atmosphere with 50-fold increase following rainfall. Free grass pollen allergen molecules have been recently shown to interact with other particles including diesel exhaust carbon particles, providing a further transport mechanism for allergens to gain access into lower airways. In this review, implication and evidence for grass pollen as a trigger of thunderstorm-associated asthma is presented. Such information is critical and mandatory for patient education and training in their allergen avoidance programs. More importantly, patients with serum IgE to group 5 allergens are at high risk of allergic asthma, especially those not protected by medication. Therefore, a system to determine the total atmospheric allergen load and devising of an effective asthma risk forecast is urgently needed and is subject to current investigation. PMID:9693274

  9. Direct observation of closure domain wall mediated spin waves

    SciTech Connect

    Mozooni, Babak McCord, Jeffrey

    2015-07-27

    The generation and guiding of spin waves from and by magnetic domain walls are demonstrated. The spin waves radiate from pinned and oscillating magnetic closure domain walls and propagate linearly along a narrow path formed by the surrounding 180° asymmetric Bloch domain walls. The propagating spin wave modes are directly visualized by time-resolved magneto-optical Kerr microscopy with picosecond temporal resolution. A linear relationship between excitation frequency, wavelength, and number of spin waves per domain exists. Independent of the field excitation frequency, a constant phase velocity of spin waves propagation is obtained. Spin waves characteristics can be tuned by varying the magnetic domain dynamics, allowing for variable spin wave characteristics with magnetic field characteristics and histories.

  10. Pollen consumption by flower mites in three hummingbird-pollinated plant species.

    PubMed

    Velázquez, Tonatiuh; Ornelas, Juan Francisco

    2010-02-01

    Laboratory studies suggest that pollen consumption by flower mites may decrease the male fitness of the plant by reducing the available pollen for dispersal. Here we assessed pollen consumption by flower mites under natural conditions in three plant species with long-lived, protandrous flowers, Moussonia deppeana (Gesneriaceae), Lobelia laxiflora and L. cardinalis (Lobeliaceae). Total pollen mass was measured after 24 and 48 h in flowers exposed to flower mites and excluded from hummingbirds, flowers exposed to mites and hummingbird visitation, and in flowers recently opened with dehisced anthers. Compared with recently opened flowers, pollen availability was reduced about half in the presence of flower mites and the same effect was observed in the three plant species. Our results suggest that flower mites are removing a great deal of pollen and the reduction of pollen implies the possibility of direct impact on pollen transfer. PMID:19763848

  11. Monarch larvae sensitivity to Bacillus thuringiensis- purified proteins and pollen

    PubMed Central

    Hellmich, Richard L.; Siegfried, Blair D.; Sears, Mark K.; Stanley-Horn, Diane E.; Daniels, Michael J.; Mattila, Heather R.; Spencer, Terrence; Bidne, Keith G.; Lewis, Leslie C.

    2001-01-01

    Laboratory tests were conducted to establish the relative toxicity of Bacillus thuringiensis (Bt) toxins and pollen from Bt corn to monarch larvae. Toxins tested included Cry1Ab, Cry1Ac, Cry9C, and Cry1F. Three methods were used: (i) purified toxins incorporated into artificial diet, (ii) pollen collected from Bt corn hybrids applied directly to milkweed leaf discs, and (iii) Bt pollen contaminated with corn tassel material applied directly to milkweed leaf discs. Bioassays of purified Bt toxins indicate that Cry9C and Cry1F proteins are relatively nontoxic to monarch first instars, whereas first instars are sensitive to Cry1Ab and Cry1Ac proteins. Older instars were 12 to 23 times less susceptible to Cry1Ab toxin compared with first instars. Pollen bioassays suggest that pollen contaminants, an artifact of pollen processing, can dramatically influence larval survival and weight gains and produce spurious results. The only transgenic corn pollen that consistently affected monarch larvae was from Cry1Ab event 176 hybrids, currently <2% corn planted and for which re-registration has not been applied. Results from the other types of Bt corn suggest that pollen from the Cry1Ab (events Bt11 and Mon810) and Cry1F, and experimental Cry9C hybrids, will have no acute effects on monarch butterfly larvae in field settings. PMID:11559841

  12. Bees use the taste of pollen to determine which flowers to visit.

    PubMed

    Muth, Felicity; Francis, Jacob S; Leonard, Anne S

    2016-07-01

    Pollen plays a dual role as both a gametophyte and a nutritional reward for pollinators. Although pollen chemistry varies across plant species, its functional significance in pollination has remained obscure, in part because little is known about how floral visitors assess it. Bees rely on pollen for protein, but whether foragers evaluate its chemistry is unclear, as it is primarily consumed by larvae. We asked whether the chemical composition of pollen influences bumblebees' foraging behaviour. Using putatively sweet and bitter pollen blends, we found that chemical composition influenced two aspects of bee behaviour relevant to plant fitness: the amount of pollen collected and the likelihood of subsequently visiting a visually similar flower. These findings offer a new perspective on the nutritional ecology of plant-pollinator interactions, as they show that pollen's taste may mediate its collection and transfer. PMID:27405383

  13. Direct simulation of amphiphilic nanoparticle mediated membrane interactions

    NASA Astrophysics Data System (ADS)

    Tahir, Mukarram; Alexander-Katz, Alfredo

    Membrane fusion is a critical step in the transport of biological cargo through membrane-bound compartments like vesicles. Membrane proteins that alleviate energy barriers for initial stalk formation and eventual rupture of the hemifusion intermediate during fusion generally assist this process. Gold nanoparticles functionalized with a combination of hydrophobic and hydrophilic alkanethiol ligands have recently been shown to induce membrane re-arrangements that are similar to those associated with these fusion proteins. In this work, we utilize molecular dynamics simulation to systematically design nanoparticles that exhibit targeted interactions with membranes. We introduce a method for rapidly parameterizing nanoparticle topology for the MARTINI biomolecular force field to permit long timescale simulation of their interactions with lipid bilayers. We leverage this model to investigate how ligand chemistry governs the nanoparticle's insertion efficacy and the perturbations it generates in the membrane environment. We further demonstrate through unbiased simulations that these nanoparticles can direct the fusion of lipid assemblies such as micelles and vesicles in a manner that mimics the function of biological fusion peptides and SNARE proteins.

  14. Pollen Viability and Pollen Tube Attrition in Cranberry (Vaccinium macrocarpon)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The content of mature seed in a cranberry fruit increases with stigmatic pollen load. On average, however, only two seeds result for every tetrad of pollen deposited. What then is the fate of the two remaining pollen grains fused in each tetrad? Germination in vitro revealed that most of the grains ...

  15. Limnic sediments and the taphonomy of Lateglacial pollen assemblages

    NASA Astrophysics Data System (ADS)

    Pennington, Winifred; Tutin, T. G.

    Pollen taphonomy, defined by R.G. West in 1973 as "the processes which govern the production of fossil (pollen) assemblages from living vegetation", introduces an additional variable into the pollen/vegetation relationship. Changes in taphonomic factors, of the kind to be expected within cold-stage Quaternary environments, may influence the composition of pollen assemblages, producing variations between them in space and time which are not directly related to variation in vegetation. Comparisons between sites — 35 Lateglacial (Late Devensian) lake sediment profiles within a 40 × 40 km region of high relief — are used to identify situations where anomalies in pollen values can be attributed to taphonomic factors. Processes involved include: redeposition of older pollen from soils (recycling) during episodes of increased instability of the land surface; spatial differentiation in deposition of sediment and pollen within the larger lakes, associated with a within-lake water circulation very different from today's; selective recruitment of pollen taxa by glacial meltwater; a) of Salix by outlet streams from small glaciers associated with favourable habitats for willows, and b) of Pinus from grains trapped by extensive mountain snowfields and larger glaciers.

  16. Pollen tube growth and guidance: roles of small, secreted proteins

    PubMed Central

    Chae, Keun; Lord, Elizabeth M.

    2011-01-01

    Background Pollination is a crucial step in angiosperm (flowering plant) reproduction. Highly orchestrated pollen–pistil interactions and signalling events enable plant species to avoid inbreeding and outcrossing as a species-specific barrier. In compatible pollination, pollen tubes carrying two sperm cells grow through the pistil transmitting tract and are precisely guided to the ovules, discharging the sperm cells to the embryo sac for fertilization. Scope In Lilium longiflorum pollination, growing pollen tubes utilize two critical mechanisms, adhesion and chemotropism, for directional growth to the ovules. Among several molecular factors discovered in the past decade, two small, secreted cysteine-rich proteins have been shown to play major roles in pollen tube adhesion and reorientation bioassays: stigma/style cysteine-rich adhesin (SCA, approx. 9·3 kDa) and chemocyanin (approx. 9·8 kDa). SCA, a lipid transfer protein (LTP) secreted from the stylar transmitting tract epidermis, functions in lily pollen tube tip growth as well as in forming the adhesive pectin matrix at the growing pollen tube wall back from the tip. Lily chemocyanin is a plantacyanin family member and acts as a directional cue for reorienting pollen tubes. Recent consecutive studies revealed that Arabidopsis thaliana homologues for SCA and chemocyanin play pivotal roles in tip polarity and directionality of pollen tube growth, respectively. This review outlines the biological roles of various secreted proteins in angiosperm pollination, focusing on plant LTPs and chemocyanin. PMID:21307038

  17. Bi-directional gap junction-mediated soma-germline communication is essential for spermatogenesis.

    PubMed

    Smendziuk, Christopher M; Messenberg, Anat; Vogl, A Wayne; Tanentzapf, Guy

    2015-08-01

    Soma-germline interactions play conserved essential roles in regulating cell proliferation, differentiation, patterning and homeostasis in the gonad. In the Drosophila testis, secreted signalling molecules of the JAK-STAT, Hedgehog, BMP and EGF pathways are used to mediate soma-germline communication. Here, we demonstrate that gap junctions may also mediate direct, bi-directional signalling between the soma and germ line. When gap junctions between the soma and germ line are disrupted, germline differentiation is blocked and germline stem cells are not maintained. In the soma, gap junctions are required to regulate proliferation and differentiation. Localization and RNAi-mediated knockdown studies reveal that gap junctions in the fly testis are heterotypic channels containing Zpg (Inx4) and Inx2 on the germ line and the soma side, respectively. Overall, our results show that bi-directional gap junction-mediated signalling is essential to coordinate the soma and germ line to ensure proper spermatogenesis in Drosophila. Moreover, we show that stem cell maintenance and differentiation in the testis are directed by gap junction-derived cues. PMID:26116660

  18. Pollen spectrum and risk of pollen allergy in central Spain.

    PubMed

    Perez-Badia, Rosa; Rapp, Ana; Morales, Celia; Sardinero, Santiago; Galan, Carmen; Garcia-Mozo, Herminia

    2010-01-01

    The present work analyses the airborne pollen dynamic of the atmosphere of Toledo (central Spain), a World Heritage Site and an important tourist city receiving over 2 millions of visitors every year. The airborne pollen spectrum, the annual dynamics of the most important taxa, the influence of meteorological variables and the risk of suffering pollen allergy are analysed. Results of the present work are compared to those obtained by similar studies in nearby regions. The average annual Pollen Index is 44,632 grains, where 70-90 percent is recorded during February-May. The pollen calendar includes 29 pollen types, in order of importance; Cupressaceae (23.3 percent of the total amount of pollen grains), Quercus (21.2 percent), and Poaceae and Olea (11.5 and 11.2 percent, respectively), are the main pollen producer taxa. From an allergological viewpoint, Toledo is a high-risk locality for the residents and tourist who visit the area, with a great number of days exceeding the allergy thresholds proposed by the Spanish Aerobiological Network (REA). The types triggering most allergic processes in Toledo citizens and tourists are Cupressaceae, Platanus, Olea, Poaceae, Urticaceae and Chenopodiaceae-Amaranthaceae. Allergic risk increases in 3 main periods: winter (January-March), with the main presence of the Cupressaceae type; spring, characterized by Poaceae, Olea, Platanus and Urticaceae pollen types; and, finally, late summer (August-September), characterized by Chenopodiaceae- Amaranthaceae pollen type, which are the main cause of allergies during these months. PMID:20684492

  19. Characteristics of modern pollen rain and the relationship to vegetation in sagebrush-steppe environments of Montana, USA

    NASA Astrophysics Data System (ADS)

    Briles, C.; Bryant, V.

    2010-12-01

    Variations in pollen production and dispersal characteristics among plant species complicate our ability to determine direct relationships between deposited pollen and actual vegetation. In order to better understand modern pollen-vegetation relationships, we analyzed pollen from 61 samples taken from sagebrush-steppe environments across Montana and compared them with the actual vegetation composition at each site. We also determined to what degree sagebrush-steppe communities can be geographically distinguished from one another based on their pollen signature. Pollen preservation was good, especially in wetter environments, with pollen degradataion ranging from 4-15%. Diploxylon Pinus was the primary contributor to the pollen rain, even in plots where pine trees did not occur or were several kilometers from the plot. Artemisia and grass pollen are underrepresented in the soils samples, while Chenopodiaceae and Juniperus pollen are overrepresented when compared to actual vegetation composition. Insect-pollinated species are present only in very minor amounts in the soil samples, even though some (e.g., Brassica) are abundant in the plots. In general, pollen spectra show significant differences between regions, however, within each region the individual spectra are not statistically significant from one another. An understanding of modern pollen-vegetation relationships and the palynological “fingerprint” of sagebrush-steppe communities aid in climatic and ecological interpretations of fossil pollen assemblages. The data also provide important control samples for forensics studies that use pollen to geolocate an object or person to a crime scene.

  20. Atmospheric conditions during high ragweed pollen concentrations in Zagreb, Croatia

    NASA Astrophysics Data System (ADS)

    Prtenjak, Maja Telišman; Srnec, Lidija; Peternel, Renata; Madžarević, Valentina; Hrga, Ivana; Stjepanović, Barbara

    2012-11-01

    We examined the atmospheric conditions favourable to the occurrence of maximum concentrations of ragweed pollen with an extremely high risk of producing allergy. Over the 2002-2009 period, daily pollen data collected in Zagreb were used to identify two periods of high pollen concentration (> 600 grains/m3) for our analysis: period A (3-4 September 2002) and period B (6-7 September 2003). Synoptic conditions in both periods were very similar: Croatia was under the influence of a lower sector high pressure system moving slowly eastward over Eastern Europe. During the 2002-2009 period, this type of weather pattern (on ~ 70% of days), in conjunction with almost non-gradient surface pressure conditions in the area (on ~ 30% of days) characterised days when the daily pollen concentrations were higher than 400 grains/m3. Numerical experiments using a mesoscale model at fine resolution showed successful multi-day simulations reproducing the local topographic influence on wind flow and in reasonable agreement with available observations. According to the model, the relatively weak synoptic flow (predominantly from the eastern direction) allowed local thermal circulations to develop over Zagreb during both high pollen episodes. Two-hour pollen concentrations and 48-h back-trajectories indicated that regional-range transport of pollen grains from the central Pannonian Plain was the cause of the high pollen concentrations during period A. During period B, the north-westward regional-range transport in Zagreb was supplemented significantly by pronounced horizontal recirculation of pollen grains. This recirculation happened within the diurnal local circulation over the city, causing a late-evening increase in pollen concentration.

  1. An operational phenological model for numerical pollen prediction

    NASA Astrophysics Data System (ADS)

    Scheifinger, Helfried

    2010-05-01

    The general prevalence of seasonal allergic rhinitis is estimated to be about 15% in Europe, and still increasing. Pre-emptive measures require both the reliable assessment of production and release of various pollen species and the forecasting of their atmospheric dispersion. For this purpose numerical pollen prediction schemes are being developed by a number of European weather services in order to supplement and improve the qualitative pollen prediction systems by state of the art instruments. Pollen emission is spatially and temporally highly variable throughout the vegetation period and not directly observed, which precludes a straightforward application of dispersion models to simulate pollen transport. Even the beginning and end of flowering, which indicates the time period of potential pollen emission, is not (yet) available in real time. One way to create a proxy for the beginning, the course and the end of the pollen emission is its simulation as function of real time temperature observations. In this work the European phenological data set of the COST725 initiative forms the basis of modelling the beginning of flowering of 15 species, some of which emit allergic pollen. In order to keep the problem as simple as possible for the sake of spatial interpolation, a 3 parameter temperature sum model was implemented in a real time operational procedure, which calculates the spatial distribution of the entry dates for the current day and 24, 48 and 72 hours in advance. As stand alone phenological model and combined with back trajectories it is thought to support the qualitative pollen prediction scheme at the Austrian national weather service. Apart from that it is planned to incorporate it in a numerical pollen dispersion model. More details, open questions and first results of the operation phenological model will be discussed and presented.

  2. Atmospheric conditions during high ragweed pollen concentrations in Zagreb, Croatia.

    PubMed

    Prtenjak, Maja Telišman; Srnec, Lidija; Peternel, Renata; Madžarević, Valentina; Hrga, Ivana; Stjepanović, Barbara

    2012-11-01

    We examined the atmospheric conditions favourable to the occurrence of maximum concentrations of ragweed pollen with an extremely high risk of producing allergy. Over the 2002-2009 period, daily pollen data collected in Zagreb were used to identify two periods of high pollen concentration (> 600 grains/m(3)) for our analysis: period A (3-4 September 2002) and period B (6-7 September 2003). Synoptic conditions in both periods were very similar: Croatia was under the influence of a lower sector high pressure system moving slowly eastward over Eastern Europe. During the 2002-2009 period, this type of weather pattern (on ~ 70% of days), in conjunction with almost non-gradient surface pressure conditions in the area (on ~ 30% of days) characterised days when the daily pollen concentrations were higher than 400 grains/m(3). Numerical experiments using a mesoscale model at fine resolution showed successful multi-day simulations reproducing the local topographic influence on wind flow and in reasonable agreement with available observations. According to the model, the relatively weak synoptic flow (predominantly from the eastern direction) allowed local thermal circulations to develop over Zagreb during both high pollen episodes. Two-hour pollen concentrations and 48-h back-trajectories indicated that regional-range transport of pollen grains from the central Pannonian Plain was the cause of the high pollen concentrations during period A. During period B, the north-westward regional-range transport in Zagreb was supplemented significantly by pronounced horizontal recirculation of pollen grains. This recirculation happened within the diurnal local circulation over the city, causing a late-evening increase in pollen concentration. PMID:22410823

  3. Patterns of pollen removal and deposition in Polemonium brandegeei (Polemoniaceae): the role of floral visitors, floral design and sexual interference.

    PubMed

    Kulbaba, M W; Worley, A C

    2014-11-01

    The arrangement, colour, shape and size of floral parts (collectively floral design) have evolved primarily to promote mating success via animal-mediated pollen transfer. Although numerous studies have examined variation in pollinator assemblages, relatively few have examined patterns of pollen removal and deposition in the presence of fluctuating pollinators and ineffective floral visitors; therefore, net pollen removal and deposition by entire visitor assemblages are unclear. We studied the timing (diurnal or nocturnal) and effects of floral traits on pollen removal and deposition under a dynamic visitor assemblage of Polemonium brandegeei. We quantified pollen grains remaining in anthers (pollen removal) and deposited on stigmas (pollen deposition) of plants visited during either the day (07:30-20:00 h) or night (20:30-07:30 h) in natural populations over two flowering seasons. Pollen removal and deposition occurred both diurnally and nocturnally during our study. Increased diurnal removal and deposition coincided with peak floral visitations in 2006. This increase in pollen removal and deposition may reflect increased visits by pollen consumers, effective hawkmoth pollinators and increased self-pollen deposition due to hot, dry weather. Nonlinear effects of style length significantly affected pollen removal, with less pollen remaining in flowers with intermediate style lengths. Pollen deposition was more complex, with herkogamy and anther height affecting deposition. Further, close proximity of stigmas and anthers increased the potential for sexual interference between pollen removal and deposition. Overall, flower visitations and pollen removal and deposition varied between years and populations, but sex organ placement consistently influenced the removal and deposition of pollen. PMID:24850527

  4. Distinct effects of pollinator dependence and self-incompatibility on pollen limitation in South African biodiversity hotspots.

    PubMed

    Rodger, James G; Ellis, Allan G

    2016-06-01

    Global synthesis indicates that limitation of plant fecundity by pollen receipt (pollen limitation) is positively related to regional plant diversity and is higher for self-incompatible than self-compatible species. While self-incompatible species are always dependent on pollinating agents, self-compatible species may be pollinator-dependent or autofertile. This should cause variation in pollen limitation among self-compatible species, with lower pollen limitation in autofertile species because they do not depend on pollinators. We hypothesized that the intensity of pollen limitation in self-incompatible compared with pollinator-dependent self-compatible species should depend on whether pollen limitation is determined more by quantity than quality of pollen received. We compared pollen limitation between these three groups using a dataset of 70 biotically pollinated species from biodiverse regions of South Africa. Comparison with a global dataset indicated that pollen limitation in the South African biodiversity hotspots was generally comparable to other regions, despite expectations of higher pollen limitation based on the global plant diversity-pollen limitation relationship. Pollen limitation was lowest for autofertile species, as expected. It was also higher for pollinator-dependent self-compatible species than self-incompatible species, consistent with increased pollen-quality limitation in the former group due to negative consequences of pollinator-mediated self-pollination. However, there was a higher frequency of plants with zygomorphic flowers, which were also more pollen-limited, among pollinator-dependent self-compatible species. Thus, we could not attribute this difference in pollen limitation exclusively to a difference in pollen quality. Nevertheless, our results indicate that comparative studies should control for both pollinator dependence and self-incompatiblity when evaluating effects of other factors on pollen limitation. PMID:27277954

  5. Intersection of two signalling pathways: extracellular nucleotides regulate pollen germination and pollen tube growth via nitric oxide

    PubMed Central

    Reichler, Stuart A.; Torres, Jonathan; Rivera, Amy L.; Cintolesi, Viviana A.; Clark, Greg; Roux, Stanley J.

    2009-01-01

    Plant and animal cells release or secrete ATP by various mechanisms, and this activity allows extracellular ATP to serve as a signalling molecule. Recent reports suggest that extracellular ATP induces plant responses ranging from increased cytosolic calcium to changes in auxin transport, xenobiotic resistance, pollen germination, and growth. Although calcium has been identified as a secondary messenger for the extracellular ATP signal, other parts of this signal transduction chain remain unknown. Increasing the extracellular concentration of ATPγS, a poorly-hydrolysable ATP analogue, inhibited both pollen germination and pollen tube elongation, while the addition of AMPS had no effect. Because pollen tube elongation is also sensitive to nitric oxide, this raised the possibility that a connection exists between the two pathways. Four approaches were used to test whether the germination and growth effects of extracellular ATPγS were transduced via nitric oxide. The results showed that increases in extracellular ATPγS induced increases in cellular nitric oxide, chemical agonists of the nitric oxide signalling pathway lowered the threshold of extracellular ATPγS that inhibits pollen germination, an antagonist of guanylate cyclase, which can inhibit some nitric oxide signalling pathways, blocked the ATPγS-induced inhibition of both pollen germination and pollen tube elongation, and the effects of applied ATPγS were blocked in nia1nia2 mutants, which have diminished NO production. The concurrence of these four data sets support the conclusion that the suppression of pollen germination and pollen tube elongation by extracellular nucleotides is mediated in part via the nitric oxide signalling pathway. PMID:19363208

  6. The mediating effects of facial expression on spatial interference between gaze direction and gaze location.

    PubMed

    Jones, Steve

    2015-01-01

    Gaze direction is an important social cue that interacts with facial expression. Cañadas and Lupiáñez (2012) reported a reverse-congruency effect such that identification of gaze direction was faster when a face was presented to the left but with the eyes directed to the right, or vice versa. In two experiments, this effect is replicated and then extended to explore the relationship between this effect and facial expression. Results show that the reverse-congruency effect is replicable with speeded gaze-direction identification, and that the effect is mediated by facial expression. The reverse-congruency effect is similar for happy and angry faces, but was not found for fearful faces. Findings are discussed in relation to the similarity of processing of incongruent gaze direction and the processing of direct gaze. PMID:25832740

  7. Diurnal variation in airborne pollen concentrations of the selected taxa in Zagreb, Croatia.

    PubMed

    Toth, Ivan; Peternel, Renata; Srnec, Lidija; Vojniković, Bozo

    2011-09-01

    The number of individuals allergic to plant pollen has recently been on a constant increase. The knowledge of diurnal distribution and abundance of allergenic pollen types, their patterns and response to source position and weather is useful to correlate hay fever symptoms with the presence of allergenic pollen in the atmosphere. The aim of this study was to determine diurnal distribution of total airborne pollen, pollen of particular allergenic taxa, possible variation in diurnal pollen distribution at measuring sites placed at different heights, and effect of some meteorological parameters on airborne pollen concentrations. A 7-day Hirst-type volumetric pollen trap was used for pollen sampling. Qualitative and quantitative pollen analysis was performed under a light microscope (magnification x400). Total pollen of all plant taxa (Ambrosia sp., Betula sp., Cupressaceae, Urticaceae, Poaceae, Quercus sp., Fraxinus sp., Alnus sp., Corylus sp., Populus sp., Pinus sp., Picea sp.) observed showed a regular diurnal distribution at both sampling sites in both study years, with a rise in the pollen concentration recorded after 4.00 a.m. and 6.00 a.m., respectively. The peak pollen concentration occurred between 12.00 a.m. and 4.00 p.m., and the lowest diurnal pollen concentrations were recorded overnight. About 50% of the 24-h pollen concentration were released to the atmosphere between 10.00 a.m. and 4.00 p.m. The timing and size of diurnal peaks were closely related to high temperature, low humidity and south-west maximum wind direction. PMID:22220402

  8. Pollen Dispersion, Pollen Viability and Pistil Receptivity in Leymus chinensis

    PubMed Central

    HUANG, ZEHAO; ZHU, JINMAO; MU, XIJIN; LIN, JINXING

    2004-01-01

    • Background and Aims Leymus chinensis is an economically and ecologically important grass that is widely distributed across eastern areas of the Eurasian steppe. A major problem facing its propagation by man is its low sexual reproductivity. The causes of low fecundity are uncertain, largely because many aspects of the reproductive biology of this species remained unknown or incomplete. This study aims to address some of these issues. • Methods Pollen dispersion, pollen viability, pollen longevity and pistil receptivity were studied in a representative, natural population of L. chinensis growing in Inner Mongolia. • Key Results Flowering of L. chinensis occurred at the end of June and lasted for 5 d. Pollination peaked between 1600 h and 1700 h, and about 56·1 % of the total pollen grains were released at this time. Pollen density was highest towards the middle of flowering spikes and lowest at the bottom over the 5 d measurement period. Pollen viability (62·4 %) assessed using TTC was more accurate than using IKI (85·6 %); 50 % of pollen arriving on stigmas germinated. Pollen remained viable for only 3 h and the pollen : ovule ratio was 79 333 : 1. Pistil receptivity lasted for only 3 h and, overall, 86·7 % of pistils were pollinated. Within the spike, the relative fecundity of different positions was middle > lower > upper throughout the period of pollination; daily variation of fecundity was similar to that of the pollen flow. The spikes that opened on the day of highest pollen density exhibited the highest fecundity (36·0 %). No seeds were produced by self‐pollination. • Conclusions The data suggest that low pollen viability, short pollen longevity and short pistil receptivity all appear to contribute to the low seed production typical of this important forage crop. PMID:14744707

  9. Chorioamnionitis-induced fetal gut injury is mediated by direct gut exposure of inflammatory mediators or by lung inflammation

    PubMed Central

    Wolfs, Tim G. A. M.; Kramer, Boris W.; Thuijls, Geertje; Kemp, Matthew W.; Saito, Masatoshi; Willems, Monique G. M.; Senthamarai-Kannan, Paranthaman; Newnham, John P.; Jobe, Alan H.

    2014-01-01

    Intra-amniotic exposure to proinflammatory agonists causes chorioamnionitis and fetal gut inflammation. Fetal gut inflammation is associated with mucosal injury and impaired gut development. We tested whether this detrimental inflammatory response of the fetal gut results from a direct local (gut derived) or an indirect inflammatory response mediated by the chorioamnion/skin or lung, since these organs are also in direct contact with the amniotic fluid. The gastrointestinal tract was isolated from the respiratory tract and the amnion/skin epithelia by fetal surgery in time-mated ewes. Lipopolysaccharide (LPS) or saline (controls) was selectively infused in the gastrointestinal tract, trachea, or amniotic compartment at 2 or 6 days before preterm delivery at 124 days gestation (term 150 days). Gastrointestinal and intratracheal LPS exposure caused distinct inflammatory responses in the fetal gut. Inflammatory responses could be distinguished by the influx of leukocytes (MPO+, CD3+, and FoxP3+ cells), tumor necrosis factor-α, and interferon-γ expression and differential upregulation of mRNA levels for Toll-like receptor 1, 2, 4, and 6. Fetal gut inflammation after direct intestinal LPS exposure resulted in severe loss of the tight junctional protein zonula occludens protein 1 (ZO-1) and increased mitosis of intestinal epithelial cells. Inflammation of the fetal gut after selective LPS instillation in the lungs caused only mild disruption of ZO-1, loss in epithelial cell integrity, and impaired epithelial differentiation. LPS exposure of the amnion/skin epithelia did not result in gut inflammation or morphological, structural, and functional changes. Our results indicate that the detrimental consequences of chorioamnionitis on fetal gut development are the combined result of local gut and lung-mediated inflammatory responses. PMID:24458021

  10. Chorioamnionitis-induced fetal gut injury is mediated by direct gut exposure of inflammatory mediators or by lung inflammation.

    PubMed

    Wolfs, Tim G A M; Kramer, Boris W; Thuijls, Geertje; Kemp, Matthew W; Saito, Masatoshi; Willems, Monique G M; Senthamarai-Kannan, Paranthaman; Newnham, John P; Jobe, Alan H; Kallapur, Suhas G

    2014-03-01

    Intra-amniotic exposure to proinflammatory agonists causes chorioamnionitis and fetal gut inflammation. Fetal gut inflammation is associated with mucosal injury and impaired gut development. We tested whether this detrimental inflammatory response of the fetal gut results from a direct local (gut derived) or an indirect inflammatory response mediated by the chorioamnion/skin or lung, since these organs are also in direct contact with the amniotic fluid. The gastrointestinal tract was isolated from the respiratory tract and the amnion/skin epithelia by fetal surgery in time-mated ewes. Lipopolysaccharide (LPS) or saline (controls) was selectively infused in the gastrointestinal tract, trachea, or amniotic compartment at 2 or 6 days before preterm delivery at 124 days gestation (term 150 days). Gastrointestinal and intratracheal LPS exposure caused distinct inflammatory responses in the fetal gut. Inflammatory responses could be distinguished by the influx of leukocytes (MPO(+), CD3(+), and FoxP3(+) cells), tumor necrosis factor-α, and interferon-γ expression and differential upregulation of mRNA levels for Toll-like receptor 1, 2, 4, and 6. Fetal gut inflammation after direct intestinal LPS exposure resulted in severe loss of the tight junctional protein zonula occludens protein 1 (ZO-1) and increased mitosis of intestinal epithelial cells. Inflammation of the fetal gut after selective LPS instillation in the lungs caused only mild disruption of ZO-1, loss in epithelial cell integrity, and impaired epithelial differentiation. LPS exposure of the amnion/skin epithelia did not result in gut inflammation or morphological, structural, and functional changes. Our results indicate that the detrimental consequences of chorioamnionitis on fetal gut development are the combined result of local gut and lung-mediated inflammatory responses. PMID:24458021

  11. Secretory activity is rapidly induced in stigmatic papillae by compatible pollen, but inhibited for self-incompatible pollen in the Brassicaceae.

    PubMed

    Safavian, Darya; Goring, Daphne R

    2013-01-01

    [In the Brassicaceae, targeted exocytosis to the stigmatic papillar plasma membrane under the compatible pollen grain is hypothesized to be essential for pollen hydration and pollen tube penetration. In contrast, polarized secretion is proposed to be inhibited in the stigmatic papillae during the rejection of self-incompatible pollen. Using transmission electron microscopy (TEM), we performed a detailed time-course of post-pollination events to view the cytological responses of the stigmatic papillae to compatible and self-incompatible pollinations. For compatible pollinations in Arabidopsis thaliana and Arabidopsis lyrata, vesicle secretion was observed at the stigmatic papillar plasma membrane under the pollen grain while Brassica napus stigmatic papillae appeared to use multivesicular bodies (MVBs) for secretion. Exo70A1, a component of the exocyst complex, has been previously implicated in the compatible pollen responses, and disruption of Exo70A1 in both A. thaliana and B. napus resulted in a loss of secretory vesicles/MVBs at the stigmatic papillar plasma membrane. Similarly, for self-incompatible pollinations, secretory vesicles/MVBs were absent from the stigmatic papillar plasma membrane in A. lyrata and B. napus; and furthermore, autophagy appeared to be induced to direct vesicles/MVBs to the vacuole for degradation. Thus, these findings support a model where the basal pollen recognition pathway in the stigmatic papilla promotes exocytosis to accept compatible pollen, and the basal pollen recognition pathway is overridden by the self-incompatibility pathway to prevent exocytosis and reject self-pollen. PMID:24386363

  12. Secretory Activity Is Rapidly Induced in Stigmatic Papillae by Compatible Pollen, but Inhibited for Self-Incompatible Pollen in the Brassicaceae

    PubMed Central

    Safavian, Darya; Goring, Daphne R.

    2013-01-01

    [In the Brassicaceae, targeted exocytosis to the stigmatic papillar plasma membrane under the compatible pollen grain is hypothesized to be essential for pollen hydration and pollen tube penetration. In contrast, polarized secretion is proposed to be inhibited in the stigmatic papillae during the rejection of self-incompatible pollen. Using transmission electron microscopy (TEM), we performed a detailed time-course of post-pollination events to view the cytological responses of the stigmatic papillae to compatible and self-incompatible pollinations. For compatible pollinations in Arabidopsis thaliana and Arabidopsis lyrata, vesicle secretion was observed at the stigmatic papillar plasma membrane under the pollen grain while Brassica napus stigmatic papillae appeared to use multivesicular bodies (MVBs) for secretion. Exo70A1, a component of the exocyst complex, has been previously implicated in the compatible pollen responses, and disruption of Exo70A1 in both A. thaliana and B. napus resulted in a loss of secretory vesicles/MVBs at the stigmatic papillar plasma membrane. Similarly, for self-incompatible pollinations, secretory vesicles/MVBs were absent from the stigmatic papillar plasma membrane in A. lyrata and B. napus; and furthermore, autophagy appeared to be induced to direct vesicles/MVBs to the vacuole for degradation. Thus, these findings support a model where the basal pollen recognition pathway in the stigmatic papilla promotes exocytosis to accept compatible pollen, and the basal pollen recognition pathway is overridden by the self-incompatibility pathway to prevent exocytosis and reject self-pollen. PMID:24386363

  13. Invited Review: DNA-mediated artificial nanobiostructures: state of the art and future directions

    NASA Astrophysics Data System (ADS)

    Bashir, R.

    2001-01-01

    DNA (deoxyribonucleic acid)-mediated assembly of nanometer and micrometer scale structures can have a profound impact in the fields of nanoelectronics and nanotechnology. Such structures can also find applications in microelectromechanical systems, hybrid bio-sensors, and the potential to continue the scaling of Moore's law beyond the 50 nm node. While engineers and scientists have been long aspiring to controllably and specifically manipulate structures at the micrometer and nanometer scale, nature has been performing these tasks and assembling structures with great accuracy and high efficiency using highly specific biological molecules such as DNA and proteins. This paper describes the motivations and fundamentals behind these assembly concepts, with a focus on DNA hybridization-mediated assembly, and presents the state of the art in this field. In addition, new ideas and directions for future research on DNA-mediated assembly of active devices and DNA-based molecular devices are also presented.

  14. A Case of Occupational Rhinitis Induced by Maize Pollen Exposure in a Farmer: Detection of IgE-Binding Components

    PubMed Central

    Sung, Se-Yong; Lee, Won-Yeon; Yong, Suk Joong; Shin, Kye Chul; Park, Hae-Sim; Kim, Hyun-Mi

    2012-01-01

    Corn is a major staple food, along with rice and wheat, in many parts of the world. There are several reports of hypersensitivity to maize pollen. However, cases of occupational allergic rhinitis induced by inhalation of maize pollen are very rare. We herein report the case of a 67-year-old male with occupational rhinitis caused by occupational exposure to maize pollen in a cornfield. He showed positive responses to maize pollen, as well as grass pollens, in skin prick tests. A high level of serum immunoglobulin E (IgE) specific to maize pollen extracts was detected by an enzyme-linked immunosorbent assay (ELISA). Laboratory tests showed a high serum level of total IgE (724 kU/L) and a high level of IgE specific to maize pollen (8.32 kU/L) using the Immuno-CAP system. Occupational rhinitis was confirmed by a nasal provocation test with maize pollen extracts. IgE ELISA inhibition tests showed antibody cross-reactivity between maize pollen and grass pollen extracts. IgE immunoblotting using maize pollen extracts demonstrated a 27 kDa IgE-binding component. These findings suggest that maize pollen can induce IgE-mediated occupational rhinitis in exposed workers. PMID:22211171

  15. Relocation of a Ca2+-dependent protein kinase activity during pollen tube reorientation

    PubMed Central

    Moutinho, A; Trewavas, AJ; Malho, R

    1998-01-01

    Pollen tube reorientation is a dynamic cellular event that is crucial for successful fertilization. We have shown previously that pollen tube orientation is regulated by cytosolic free calcium ([Ca2+]c). In this paper, we studied the activity of a Ca2+-dependent protein kinase during reorientation. The kinase activity was assayed in living cells by using confocal ratio imaging of BODIPY FL bisindolylmaleimide. We found that growing pollen tubes exhibited higher protein kinase activity in the apical region, whereas nongrowing cells showed uniform distribution. Modification of growth direction by diffusion of inhibitors/activators from a micropipette showed the spatial redistribution of kinase activity to predict the new growth orientation. Localized increases in [Ca2+]c induced by photolysis of caged Ca2+ that led to reorientation also increased kinase activity. Molecular and immunological assays suggest that this kinase may show some functional homology with protein kinase C. We suggest that the tip-localized gradient of kinase activity promotes Ca2+-mediated exocytosis and may act to regulate Ca2+ channel activity. PMID:9724696

  16. Control of Transposon-mediated Directed Mutation by the Escherichia coli Phosphoenolpyruvate:Sugar Phosphotransferase System

    PubMed Central

    Saier, Milton H.; Zhang, Zhongge

    2015-01-01

    The phosphoenolpyruvate:sugar phosphotransferase system (PTS) has been shown to control transport, cell metabolism and gene expression. We here present results supporting the novel suggestion that in certain instances, it also regulates mutation rate. Directed mutations are defined as mutations that occur at higher frequencies when beneficial than when neutral or detrimental. To date, the occurrence of directed point mutations has not been documented and confirmed, but a few examples of transposon-mediated directed mutation have been reported. Here we focus on the first and best-studied example of directed mutation, which involves the regulation of Insertion Sequence-5 (IS5) hopping into a specific site upstream of the glpFK glycerol utilization operon in Escherichia coli. This insertional event specifically activates expression of the glpFK operon, allowing growth of wild type cells with glycerol as a carbon source in the presence of non-metabolizable glucose analogues which normally block glycerol utilization. The sugar transporting PTS controls this process by regulating levels of cytoplasmic glycerol-3-phosphate and cyclic AMP as established in previous publications. Direct involvement of the glycerol repressor, GlpR, and the cyclic AMP receptor protein, Crp, in the regulation of transposon-mediated directed mutation has been demonstrated. PMID:26159081

  17. Iodine(III)-Mediated para-Selective Direct Imidation of Anilides.

    PubMed

    Pialat, Amélie; Bergès, Julien; Sabourin, Axel; Vinck, Robin; Liégault, Benoît; Taillefer, Marc

    2015-07-01

    The direct, nucleophilic imidation of acetanilide derivatives has been performed under mild, iodine(III)-mediated or -catalyzed conditions, employing lithium triflimide as the nitrogen source. The reaction exhibits exclusive regioselectivity for the para position and shows a good tolerance for varied functional groups at both the ortho or meta positions. Preliminary mechanistic data suggest that the LiNTf2 reagent plays a key role in the reactivity. PMID:26095155

  18. Migratory beekeeping practices contribute insignificantly to transgenic pollen flow among fields of alfalfa produced for seed

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Increased use of genetically engineered crops in agriculture has raised concerns over pollinator-mediated gene flow between transgenic and conventional agricultural varieties. This study evaluated whether contracted migratory beekeeping practices influence transgenic pollen flow among spatially iso...

  19. Molecular Ice Nucleation Activity of Birch Pollen

    NASA Astrophysics Data System (ADS)

    Felgitsch, Laura; Bichler, Magdalena; Häusler, Thomas; Weiss, Victor U.; Marchetti-Deschmann, Martina; Allmaier, Günter; Grothe, Hinrich

    2015-04-01

    Heterogeneous ice nucleation plays a major part in ecosystem and climate. Due to the triggering of ice cloud formation it influences the radiation balance of the earth, but also on the ground it can be found to be important in many processes of nature. So far the process of heterogeneous ice nucleation is not fully understood and many questions remain to be answered. Biological ice nucleation is hereby from great interest, because it shows the highest freezing temperatures. Several bacteria and fungi act as ice nuclei. A famous example is Pseudomonas syringae, a bacterium in commercial use (Snomax®), which increases the freezing from homogeneous freezing temperatures of approx. -40° C (for small volumes as in cloud droplets) to temperatures up to -2° C. In 2001 it was found that birch pollen can trigger ice nucleation (Diehl et al. 2001; Diehl et al. 2002). For a long time it was believed that this is due to macroscopic features of the pollen surface. Recent findings of Bernhard Pummer (2012) show a different picture. The ice nuclei are not attached on the pollen surface directly, but on surface material which can be easily washed off. This shows that not only the surface morphology, but also specific molecules or molecular structures are responsible for the ice nucleation activity of birch pollen. With various analytic methods we work on elucidating the structure of these molecules as well as the mechanism with which they trigger ice nucleation. To solve this we use various instrumental analytic techniques like Nuclear Magnetic Resonance spectroscopy (NMR), Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-MS), and Gas-phase Electrophoretic Mobility Molecular Analysis (GEMMA). Also standard techniques like various chromatographic separation techniques and solvent extraction are in use. We state here that this feature might be due to the aggregation of small molecules, with agglomerates showing a specific surface structure. Our results

  20. POLLEN FLOW IN THE ENVIRONMENT - DEVELOPMENT OF A RESEARCH PROGRAM

    EPA Science Inventory

    The USEPA Office of Research and Development seeks to provide to the agency and society the best information relating to the status of the environment and any related technology maintaining environmental quality. In this effort, a recent research workshop (Pollen Mediated Gene Fl...

  1. Evidence for landscape-level, pollen-mediated gene flow from genetically modified creeping bentgrass with CP4 EPSPS as a marker

    USGS Publications Warehouse

    Watrud, L.S.; Lee, E.H.; Fairbrother, A.; Burdick, C.; Reichman, J.R.; Bollman, M.; Storm, M.; King, G.; Van De Water, Peter K.

    2004-01-01

    Sampling methods and results of a gene flow study are described that will be of interest to plant scientists, evolutionary biologists, ecologists, and stakeholders assessing the environmental safety of transgenic crops. This study documents gene flow on a landscape level from creeping bentgrass (Agrostis stolonifera L.), one of the first wind-pollinated, perennial, and highly outcrossing transgenic crops being developed for commercial use. Most of the gene flow occurred within 2 km in the direction of prevailing winds. The maximal gene flow distances observed were 21 km and 14 km in sentinel and resident plants, respectively, that were located in primarily nonagronomic habitats. The selectable marker used in these studies was the CP4 EPSPS gene derived from Agrobacterium spp. strain CP4 that encodes 5-enol-pyruvylshikimate-3-phosphate synthase and confers resistance to glyphosate herbicide. Evidence for gene flow to 75 of 138 sentinel plants of A. stolonifera and to 29 of 69 resident Agrostis plants was based on seedling progeny survival after spraying with glyphosate in greenhouse assays and positive TraitChek, PCR, and sequencing results. Additional studies are needed to determine whether introgression will occur and whether it will affect the ecological fitness of progeny or the structure of plant communities in which transgenic progeny may become established.

  2. Evidence for landscape-level, pollen-mediated gene flow from genetically modified creeping bentgrass with CP4 EPSPS as a marker

    PubMed Central

    Watrud, Lidia S.; Lee, E. Henry; Fairbrother, Anne; Burdick, Connie; Reichman, Jay R.; Bollman, Mike; Storm, Marjorie; King, George; Van de Water, Peter K.

    2004-01-01

    Sampling methods and results of a gene flow study are described that will be of interest to plant scientists, evolutionary biologists, ecologists, and stakeholders assessing the environmental safety of transgenic crops. This study documents gene flow on a landscape level from creeping bentgrass (Agrostis stolonifera L.), one of the first wind-pollinated, perennial, and highly outcrossing transgenic crops being developed for commercial use. Most of the gene flow occurred within 2 km in the direction of prevailing winds. The maximal gene flow distances observed were 21 km and 14 km in sentinel and resident plants, respectively, that were located in primarily nonagronomic habitats. The selectable marker used in these studies was the CP4 EPSPS gene derived from Agrobacterium spp. strain CP4 that encodes 5-enol-pyruvylshikimate-3-phosphate synthase and confers resistance to glyphosate herbicide. Evidence for gene flow to 75 of 138 sentinel plants of A. stolonifera and to 29 of 69 resident Agrostis plants was based on seedling progeny survival after spraying with glyphosate in greenhouse assays and positive TraitChek, PCR, and sequencing results. Additional studies are needed to determine whether introgression will occur and whether it will affect the ecological fitness of progeny or the structure of plant communities in which transgenic progeny may become established. PMID:15448206

  3. Exchange Protein Directly Activated by cAMP Modulates Regulatory T-Cell-Mediated Immunosuppression

    PubMed Central

    Almahariq, Muayad; Mei, Fang C.; Wang, Hui; Cao, Anthony T.; Yao, Suxia; Soong, Lynn; Sun, Jiaren; Cong, Yingzi; Chen, Ju; Cheng, Xiaodong

    2016-01-01

    The cyclic adenosine monophosphate (cAMP) signaling pathway plays an essential role in immune functions. In this study we examined the role of the cAMP/EPAC1 (exchange protein directly activated by cAMP) axis in regulatory T-cell (Treg)-mediated immune suppression using genetic and pharmacologic approaches. Genetic deletion of EPAC1 in Treg and effector T-cells (Teff) synergistically attenuated Treg-mediated suppression of Teff. Mechanistically, EPAC1 inhibition enhanced activation of the transcription factor STAT3 and up-regulated SMAD7 expression while down-regulating expression of SMAD4. Consequently, CD4+T-cells were desensitized to TGF-β1, a cytokine employed by Treg cells to exert a broad inhibitory function within the immune system. Furthermore, deletion of EPAC1 led to production of significant levels of OVA-IgG antibodies in a low dose oral tolerance mouse mode. These in vivo observations are consistent with the finding that EPAC1 plays an important role in Treg-mediated suppression. More importantly, pharmacological inhibition of EPAC1 using an EPAC specific inhibitor recapitulates the EPAC1 deletion phenotype both in vivo and in vitro. Our results show that EPAC1 boosts Treg-mediated suppression, and identify EPAC1 as a target with broad therapeutic potential since Treg cells are involved in numerous pathologies including autoimmunity, infections, and a wide range of cancers. PMID:25339598

  4. Grass pollen hypersensitivity in mice

    PubMed Central

    McCaskill, A. C.; Hosking, C. S.; Hill, D. J.

    1982-01-01

    Mice were sensitized by intranasal administration of ryegrass pollen. Subsequent nasal challenge with pollen extract led to a `shock' response peaking in severity 4 hr after challenge. Histological examination of lungs revealed the development of a pneumonitis which was most severe 3 days after challenge. ImagesFigure 2 PMID:7106842

  5. LeSTIG1, an extracellular binding partner for the pollen receptor kinases LePRK1 and LePRK2, promotes pollen tube growth in vitro.

    PubMed

    Tang, Weihua; Kelley, Dior; Ezcurra, Inés; Cotter, Robyn; McCormick, Sheila

    2004-08-01

    As pollen tubes grow through the pistil they are thought to perceive and respond to diverse signals. The tomato pollen-specific receptor kinases LePRK1 and LePRK2 might participate in signaling during pollen tube growth. We previously showed that the extracellular domain of LePRK2 interacts with a pollen protein, LAT52, before but not after pollen germination. To determine whether LePRK2 might have different binding partner(s) after pollen germination, we characterized two more proteins that, like LAT52, were identified in yeast two-hybrid screens using the extracellular domains of LePRK1 and LePRK2 as baits. We show that LeSHY, a leucine-rich repeat protein from pollen, and LeSTIG1, a small cysteine-rich protein from pistil, can bind the extracellular domains of both LePRK1 and LePRK2 in vitro. In vitro binding assays with the extracellular domain of LePRK2 suggested that LeSTIG1 could displace binding of LAT52, consistent with the idea that LePRK1 and LePRK2 might interact with different ligands at different stages of pollen tube growth. Exogenous LeSTIG1 promotes pollen tube growth in vitro. The interaction of these pollen kinases with LeSTIG1 supports the notion that LePRK1 and LePRK2 are involved in mediating pollen-pistil interactions. PMID:15255864

  6. Degradation-mediated cellular traction directs stem cell fate in covalently crosslinked three-dimensional hydrogels

    NASA Astrophysics Data System (ADS)

    Khetan, Sudhir; Guvendiren, Murat; Legant, Wesley R.; Cohen, Daniel M.; Chen, Christopher S.; Burdick, Jason A.

    2013-05-01

    Although cell-matrix adhesive interactions are known to regulate stem cell differentiation, the underlying mechanisms, in particular for direct three-dimensional encapsulation within hydrogels, are poorly understood. Here, we demonstrate that in covalently crosslinked hyaluronic acid (HA) hydrogels, the differentiation of human mesenchymal stem cells (hMSCs) is directed by the generation of degradation-mediated cellular traction, independently of cell morphology or matrix mechanics. hMSCs within HA hydrogels of equivalent elastic moduli that permit (restrict) cell-mediated degradation exhibited high (low) degrees of cell spreading and high (low) tractions, and favoured osteogenesis (adipogenesis). Moreover, switching the permissive hydrogel to a restrictive state through delayed secondary crosslinking reduced further hydrogel degradation, suppressed traction, and caused a switch from osteogenesis to adipogenesis in the absence of changes to the extended cellular morphology. Furthermore, inhibiting tension-mediated signalling in the permissive environment mirrored the effects of delayed secondary crosslinking, whereas upregulating tension induced osteogenesis even in the restrictive environment.

  7. Opioid receptors mediate direct predictive fear learning: Evidence from one-trial blocking

    PubMed Central

    Cole, Sindy; McNally, Gavan P.

    2007-01-01

    Pavlovian fear learning depends on predictive error, so that fear learning occurs when the actual outcome of a conditioning trial exceeds the expected outcome. Previous research has shown that opioid receptors, including μ-opioid receptors in the ventrolateral quadrant of the midbrain periaqueductal gray (vlPAG), mediate such predictive fear learning. Four experiments reported here used a within-subject one-trial blocking design to study whether opioid receptors mediate a direct or indirect action of predictive error on Pavlovian association formation. In Stage I, rats were trained to fear conditioned stimulus (CS) A by pairing it with shock. In Stage II, CSA and CSB were co-presented once and co-terminated with shock. Two novel stimuli, CSC and CSD, were also co-presented once and co-terminated with shock in Stage II. The results showed one-trial blocking of fear learning (Experiment 1) as well as one-trial unblocking of fear learning when Stage II training employed a higher intensity footshock than was used in Stage I (Experiment 2). Systemic administrations of the opioid receptor antagonist naloxone (Experiment 3) or intra-vlPAG administrations of the selective μ-opioid receptor antagonist CTAP (Experiment 4) prior to Stage II training prevented one-trial blocking. These results show that opioid receptors mediate the direct actions of predictive error on Pavlovian association formation. PMID:17404385

  8. Dependence of 5-fluorouracil-mediated radiosensitization on DNA-directed effects

    SciTech Connect

    Lawrence, T.S.; Davis, M.A.; Maybaum, J. )

    1994-06-15

    Although 5-fluorouracil (FUra) has been demonstrated to be a radiation sensitizer both in the laboratory and the clinic, it is not known whether radiosensitization results primary from FUra's DNA or RNA-directed effects. The authors studied the radiosensitizing effects of FUra [+-] thymidine (dThd) on HT29 human colon cancer cells, which are relatively sensitive to the DNA-directed action of FUra, in comparison to SW620 and HuTu80 human colon cancer cells, which are relatively resistant to FUra's DNA-directed effects. They hypothesized that if FUra were acting chiefly through DNA dependent mechanisms, HT29 cells would (a) show greater radiosensitization than SW620 and HuTu80 cells under the same conditions of exposure; and (b) demonstrate selective reversal of radiation sensitivity (compared to cytotoxicity) in the presence of FUra + dThd, compared to FUra alone. They found that the enhancement ratio produced by a 24 h exposure to 10 [mu]M FUra was significantly greater in HT29 cells compared to SW620 and HuTu80 cells (enhancement ratios of 2.1 [+-] 0.1; 1.1 [+-] 0.1, and 1.3 [+-] 0.1, respectively). Furthermore, in HT29 cells, dThd blocked FUra-mediated radiosensitization to a greater extent than FUra-mediated cytotoxicity. Thus, the hypotheses were confirmed. These findings support the concept that the manipulation of FUra's DNA-dependent actions, for example, through modulators of thymidylate synthase (TS) activity, may increase radiosensitization in clinical trials in the treatment of gastrointestinal cancers. However, since resistance to the DNA-directed effects of fluoropyrimidines can result from mechanisms unrelated to TS inhibition, additional strategies will be required to potentiate fluoropyrimidine-mediated radiosensitization. 15 refs., 2 figs., 1 tab.

  9. A genetically encoded alkyne directs palladium-mediated protein labeling on live mammalian cell surface.

    PubMed

    Li, Nan; Ramil, Carlo P; Lim, Reyna K V; Lin, Qing

    2015-02-20

    The merging of site-specific incorporation of small bioorthogonal functional groups into proteins via amber codon suppression with bioorthogonal chemistry has created exciting opportunities to extend the power of organic reactions to living systems. Here we show that a new alkyne amino acid can be site-selectively incorporated into mammalian proteins via a known orthogonal pyrrolysyl-tRNA synthetase/tRNACUA pair and directs an unprecedented, palladium-mediated cross-coupling reaction-driven protein labeling on live mammalian cell surface. A comparison study with the alkyne-encoded proteins in vitro indicated that this terminal alkyne is better suited for the palladium-mediated cross-coupling reaction than the copper-catalyzed click chemistry. PMID:25347611

  10. Transition metal-catalyzed ketone-directed or mediated C-H functionalization.

    PubMed

    Huang, Zhongxing; Lim, Hee Nam; Mo, Fanyang; Young, Michael C; Dong, Guangbin

    2015-11-01

    Transition metal-catalyzed C-H functionalization has evolved into a prominent and indispensable tool in organic synthesis. While nitrogen, phosphorus and sulfur-based functional groups (FGs) are widely employed as effective directing groups (DGs) to control the site-selectivity of C-H activation, the use of common FGs (e.g. ketone, alcohol and amine) as DGs has been continuously pursued. Ketones are an especially attractive choice of DGs and substrates due to their prevalence in various molecules and versatile reactivity as synthetic intermediates. Over the last two decades, transition metal-catalyzed C-H functionalization that is directed or mediated by ketones has experienced vigorous growth. This review summarizes these advancements into three major categories: use of ketone carbonyls as DGs, direct β-functionalization, and α-alkylation/alkenylation with unactivated olefins and alkynes. Each of these subsections is discussed from the perspective of strategic design and reaction discovery. PMID:26185960

  11. Impacts of air pollution exposure on the allergenic properties of Arizona cypress pollens

    NASA Astrophysics Data System (ADS)

    Shahali, Y.; Pourpak, Z.; Moin, M.; Zare, A.; Majd, A.

    2009-02-01

    Epidemiological studies have demonstrated that urbanization and high levels of vehicle emissions correlated with the increasing trend of pollen-induced respiratory allergies. Numerous works have investigated the role of pollutants in the pathogenesis of respiratory diseases but impacts of anthropogenic pollution on pollen allergenic properties are still poorly understood. The objective of this survey was to evaluate impacts of the traffic-related pollution on the structure and allergenic protein content of Arizona cypress (Cupressus arizonica, CA) pollens, recognized as a rising cause of seasonal allergy in various regions worldwide. According to our results, traffic-related air pollution by its direct effects on the elemental composition of pollens considerably increased the fragility of the pollen exine, causing numerous cracks in its surface and facilitating pollen content liberation. Pollen grains were also covered by numerous submicronic orbicules which may act as effective vectors for pollen-released components into the lower regions of respiratory organs. On the other hand, this study provides us reliable explications about the low efficiency of standard commercial allergens in the diagnosis of the Arizona cypress pollen allergy in Tehran. Although traffic related pollution affects the allergenic components of CA pollens, the repercussions on the respiratory health of urban populations have yet to be clarified and need further investigations.

  12. Arabidopsis RIC1 Severs Actin Filaments at the Apex to Regulate Pollen Tube Growth

    PubMed Central

    Zhou, Zhenzhen; Shi, Haifan; Chen, Binqing; Zhang, Ruihui; Huang, Shanjin; Fu, Ying

    2015-01-01

    Pollen tubes deliver sperms to the ovule for fertilization via tip growth. The rapid turnover of F-actin in pollen tube tips plays an important role in this process. In this study, we demonstrate that Arabidopsis thaliana RIC1, a member of the ROP-interactive CRIB motif-containing protein family, regulates pollen tube growth via its F-actin severing activity. Knockout of RIC1 enhanced pollen tube elongation, while overexpression of RIC1 dramatically reduced tube growth. Pharmacological analysis indicated that RIC1 affected F-actin dynamics in pollen tubes. In vitro biochemical assays revealed that RIC1 directly bound and severed F-actin in the presence of Ca2+ in addition to interfering with F-actin turnover by capping F-actin at the barbed ends. In vivo, RIC1 localized primarily to the apical plasma membrane (PM) of pollen tubes. The level of RIC1 at the apical PM oscillated during pollen tube growth. The frequency of F-actin severing at the apex was notably decreased in ric1-1 pollen tubes but was increased in pollen tubes overexpressing RIC1. We propose that RIC1 regulates F-actin dynamics at the apical PM as well as the cytosol by severing F-actin and capping the barbed ends in the cytoplasm, establishing a novel mechanism that underlies the regulation of pollen tube growth. PMID:25804540

  13. Complex pleiotropy characterizes the pollen hoarding syndrome in honey bees (Apis mellifera L.).

    PubMed

    Page, Robert E; Fondrk, M Kim; Rueppell, Olav

    2012-11-01

    The pollen hoarding syndrome consists of a large suite of correlated traits in honey bees that may have played an important role in colony organization and consequently the social evolution of honey bees. The syndrome was first discovered in two strains that have been artificially selected for high and low pollen hoarding. These selected strains are used here to further investigate the phenotypic and genetic links between two central aspects of the pollen hoarding syndrome, sucrose responsiveness and pollen hoarding. Sons of hybrid queen offspring of these two strains were tested for sucrose responsiveness and used to produce colonies with either a highly responsive or an unresponsive father. These two colony groups differed significantly in the amount of pollen stored on brood combs and with regards to their relationship between brood and pollen amounts. Additionally, four quantitative trait loci (QTL) for pollen hoarding behavior were assessed for their effect on sucrose responsiveness. Drone offspring of two hybrid queens were phenotyped for responsiveness and genotyped at marker loci for these QTL, identifying some pleiotropic effects of the QTL with significant QTL interactions. Both experiments thus provided corroborating evidence that the distinct traits of the pollen hoarding syndrome are mechanistically and genetically linked, and that these links are complex and dependent on background genotype. The study demonstrates genetic worker-drone correlations within the context of the pollen hoarding syndrome and establishes that an indirect selection response connects pollen hoarding and sucrose responsiveness, regardless of which trait is directly selected. PMID:23226916

  14. Complex pleiotropy characterizes the pollen hoarding syndrome in honey bees (Apis mellifera L.)

    PubMed Central

    Page, Robert E.; Fondrk, M. Kim; Rueppell, Olav

    2012-01-01

    The pollen hoarding syndrome consists of a large suite of correlated traits in honey bees that may have played an important role in colony organization and consequently the social evolution of honey bees. The syndrome was first discovered in two strains that have been artificially selected for high and low pollen hoarding. These selected strains are used here to further investigate the phenotypic and genetic links between two central aspects of the pollen hoarding syndrome, sucrose responsiveness and pollen hoarding. Sons of hybrid queen offspring of these two strains were tested for sucrose responsiveness and used to produce colonies with either a highly responsive or an unresponsive father. These two colony groups differed significantly in the amount of pollen stored on brood combs and with regards to their relationship between brood and pollen amounts. Additionally, four quantitative trait loci (QTL) for pollen hoarding behavior were assessed for their effect on sucrose responsiveness. Drone offspring of two hybrid queens were phenotyped for responsiveness and genotyped at marker loci for these QTL, identifying some pleiotropic effects of the QTL with significant QTL interactions. Both experiments thus provided corroborating evidence that the distinct traits of the pollen hoarding syndrome are mechanistically and genetically linked, and that these links are complex and dependent on background genotype. The study demonstrates genetic worker-drone correlations within the context of the pollen hoarding syndrome and establishes that an indirect selection response connects pollen hoarding and sucrose responsiveness, regardless of which trait is directly selected. PMID:23226916

  15. Arabidopsis FIM5 decorates apical actin filaments and regulates their organization in the pollen tube

    PubMed Central

    Zhang, Meng; Zhang, Ruihui; Qu, Xiaolu; Huang, Shanjin

    2016-01-01

    The actin cytoskeleton is increasingly recognized as a major regulator of pollen tube growth. Actin filaments have distinct distribution patterns and dynamic properties within different regions of the pollen tube. Apical actin filaments are highly dynamic and crucial for pollen tube growth. However, how apical actin filaments are generated and properly constructed remains an open question. Here we showed that Arabidopsis fimbrin5 (FIM5) decorates filamentous structures throughout the entire tube but is apically concentrated. Apical actin structures are disorganized to different degrees in the pollen tubes of fim5 loss-of-function mutants. Further observations suggest that apical actin structures are not constructed properly because apical actin filaments cannot be maintained at the cortex of fim5 pollen tubes. Actin filaments appeared to be more curved in fim5 pollen tubes and this was confirmed by measurements showing that the convolutedness and the rate of change of convolutedness of actin filaments was significantly increased in fim5 pollen tubes. This suggests that the rigidity of the actin filaments may be compromised in fim5 pollen tubes. Further, the apical cell wall composition is altered, implying that tip-directed vesicle trafficking events are impaired in fim5 pollen tubes. Thus, we found that FIM5 decorates apical actin filaments and regulates their organization in order to drive polarized pollen tube growth. PMID:27117336

  16. Airborne pollen assemblages and weather regime in the central-eastern Loess Plateau, China

    NASA Astrophysics Data System (ADS)

    Li, Yuecong; Ge, Yawen; Xu, Qinghai; Bunting, Jane M.; Lv, Suqing; Wang, Junting; Li, Zetao

    2015-04-01

    This paper presents the results of pollen trapping studies designed to quantify the pollen assemblages carried in the winds of the Loess Plateau in Luochuan and Hunyuan. The one-year-collection samples analysis results show that pollen assemblages can be more sensitive to the change of climate than the vegetation composition, because of the change of pollen production. The analysis results of pollen traps in different weather regimes indicate that the pollen influx coming from dust weather contribute more to the total pollen influx than that coming from non-dust weather. The wind speed is the most important influenced factor to pollen assemblages, then the mean temperature and the mean relative humidity, the wind direction also contributes some. Strong wind coming from dust direction can make the percent and influx of Artemisia and Chenopodiaceae increase obviously with averagely higher than over 2.7 times in dust weather than in non-dust samples. The influences of wind speed and wind direction are not serious to some arboreal pollen such as Rosaceae, Quercus, Betula, Pinus and Ostryopsis, which are mainly influenced by temperature or the relative humidity such as Salix, Hippophae, Carpinus, Brassicaceae, Cupressaceae, Fabaceae.

  17. A novel method to directionally stabilize enzymes together with redox mediators by electrodeposition.

    PubMed

    Shi, Wentao; Lin, Nansen; Song, Yilin; Liu, Chunxiu; Zhou, Shuai; Cai, Xinxia

    2014-01-15

    This paper depicts a novel method to directionally stabilize enzymes together with redox mediators by electrodeposition. Chitosan was used as a stabilizing matrix. By electrochemical removal of local H(+), chitosan close to working electrode became locally insoluble, and enzymes and redox mediators in chitosan were stabilized. The microelectrode on home-made microelectrode array (MEA) served as the working electrode. Three model enzymes--horseradish peroxidase (HRP), glucose oxidase (GOD), and glutamate oxidase (GlOD)--were used to fabricate different biosensors, and the redox mediator model was a poly(vinylpyridine) complex of Os(bpy)2Cl and a diepoxide (PVP-Os). Biosensors fabricated by the method exhibited very high performance. For HRP biosensor fabricated by this method, the sensitivity was 5.274 nA μM(-1) mm(-2), with linear detection range (LDR) of 2-220 μM and limit of detection (LOD) of 1 μM (S/N=3); for GOD biosensor, the sensitivity was 2.65 nA μM(-1) mm(-2), with LDR of 4-500 μM and LOD of 2 μM (S/N=3); for GlOD biosensor, the sensitivity was 0.33 nA μM(-1)mm(-2), with LDR of 4-500 μM and LOD of 2 μM (S/N=3). Since this method is very simple and especially suitable for directionally introducing enzymes and redox mediators onto microelectrode without contaminating other sites in the same microenvironment, it could be used for fabricating in vivo or in vitro 2nd generation biosensors in μm-scale, especially in neuroscience. PMID:23974156

  18. The occurrence of Ambrosia pollen in Rzeszów, Kraków and Poznań, Poland: investigation of trends and possible transport of Ambrosia pollen from Ukraine

    NASA Astrophysics Data System (ADS)

    Kasprzyk, Idalia; Myszkowska, Dorota; Grewling, Łukasz; Stach, Alicja; Šikoparija, Branko; Ambelas Skjøth, Carsten; Smith, Matt

    2011-07-01

    Previous studies have shown that ragweed pollen arrives in Poland from sources in the south, in Slovakia, the Czech Republic, Hungary and Austria. It is likely that ragweed pollen also arrives from sources in the southeast (e.g. Ukraine). This hypothesis was investigated using 13 years of pollen data and back-trajectory analysis. Ambrosia pollen data were collected at three sites in Poland, Rzeszów, Kraków and Poznań. The amount of ragweed pollen recorded at Rzeszów was significantly higher than in Poznań and Kraków. This can be related to either a higher abundance of local populations of Ambrosia in south-east Poland or the proximity of Rzeszów to foreign sources of ragweed pollen. The combined results of pollen measurements and air mass trajectory calculations identified plumes of Ambrosia pollen that were recorded at Rzeszów, Kraków and Poznań on 4 and 5 September 1999 and 3 September 2002. These plumes arrived at the pollen-monitoring sites from an easterly direction, indicating sources of Ambrosia pollen in eastern Poland or Ukraine. This identifies Ukraine as a possible new source of ragweed pollen for Poland and therefore an important source area of Ambrosia pollen on the European Continent.

  19. Kin-mediated reconciliation substitutes for direct reconciliation in female baboons.

    PubMed

    Wittig, Roman M; Crockford, Catherine; Wikberg, Eva; Seyfarth, Robert M; Cheney, Dorothy L

    2007-04-22

    It has been hypothesized that group-living mammals engage in reconciliation (post-conflict affiliation between former opponents) to reduce the disruptive costs of aggression and restore opponents' tolerance to baseline levels. Recipients of aggression are sometimes reluctant to tolerate the proximity of a recent opponent, however, in apparent fear that aggression will be renewed. In such cases, reconciliatory behaviour by the aggressor's close kin may substitute for direct reconciliation. We describe a playback experiment with free-ranging baboons (Papio hamadryas ursinus) that examines whether friendly behaviour by the aggressor's kin can substitute for direct reconciliation by the aggressor herself. In the test condition, female subjects who had recently been threatened heard the friendly grunt of one of their aggressor's relatives, mimicking kin-mediated vocal reconciliation. In the control condition, subjects heard the grunt of a dominant female from a different matriline. Subjects responded significantly more strongly in test than in control trials. Moreover, in the next hour they were significantly more likely to tolerate the proximity of both their aggressor and the relative whose grunt they had heard. In contrast, subjects' behaviour towards both control females and other members of their aggressor's matriline was unaffected. We conclude that kin-mediated vocal reconciliation can substitute for direct reconciliation in baboons. PMID:17301022

  20. In vitro particulate matter exposure causes direct and lung-mediated indirect effects on cardiomyocyte function.

    PubMed

    Gorr, Matthew W; Youtz, Dane J; Eichenseer, Clayton M; Smith, Korbin E; Nelin, Timothy D; Cormet-Boyaka, Estelle; Wold, Loren E

    2015-07-01

    Particulate matter (PM) exposure induces a pathological response from both the lungs and the cardiovascular system. PM is capable of both manifestation into the lung epithelium and entrance into the bloodstream. Therefore, PM has the capacity for both direct and lung-mediated indirect effects on the heart. In the present studies, we exposed isolated rat cardiomyocytes to ultrafine particulate matter (diesel exhaust particles, DEP) and examined their contractile function and calcium handling ability. In another set of experiments, lung epithelial cells (16HBE14o- or Calu-3) were cultured on permeable supports that allowed access to both the basal (serosal) and apical (mucosal) media; the basal media was used to culture cardiomyocytes to model the indirect, lung-mediated effects of PM on the heart. Both the direct and indirect treatments caused a reduction in contractility as evidenced by reduced percent sarcomere shortening and reduced calcium handling ability measured in field-stimulated cardiomyocytes. Treatment of cardiomyocytes with various anti-oxidants before culture with DEP was able to partially prevent the contractile dysfunction. The basal media from lung epithelial cells treated with PM contained several inflammatory cytokines, and we found that monocyte chemotactic protein-1 was a key trigger for cardiomyocyte dysfunction. These results indicate the presence of both direct and indirect effects of PM on cardiomyocyte function in vitro. Future work will focus on elucidating the mechanisms involved in these separate pathways using in vivo models of air pollution exposure. PMID:25957217

  1. Enteric oxalate secretion is not directly mediated by the human CFTR chloride channel

    PubMed Central

    Hatch, Marguerite

    2013-01-01

    The secretion of the oxalate anion by intestinal epithelia is a functionally significant component of oxalate homeostasis and hence a relevant factor in the etiology and management of calcium oxalate urolithiasis. To test the hypothesis that human cystic fibrosis transmembrane conductance regulator (hCFTR) can directly mediate the efflux of the oxalate anion, we compared cAMP-stimulated 36Cl−, 14C-oxalate, and 35SO42− efflux from Xenopus oocytes expressing hCFTR with water-injected control oocytes. hCFTR-expressing oocytes exhibited a large, reversible cAMP-dependent increase in whole cell conductance measured using a two-electrode voltage clamp and a 13-fold increase in rate of cAMP-stimulated 36Cl− efflux. In contrast, the rate constants of oxalate and sulfate efflux were low and unaffected by cAMP in either control or hCFTR-expressing oocytes. We conclude that the human CFTR gene product does not directly mediate oxalate efflux in secretory epithelia and hence is not directly involved in oxalate homeostasis in humans. PMID:18563405

  2. Comparison of modern pollen distribution between the northern and southern parts of the South China Sea

    NASA Astrophysics Data System (ADS)

    Luo, Chuanxiu; Chen, Muhong; Xiang, Rong; Liu, Jianguo; Zhang, Lanlan; Lu, Jun

    2015-04-01

    The authors conducted a palynological analysis based on different number of air pollen samples for the northern and southern parts of the South China Sea, respectively, in order to give a reference to reconstruct the paleoclimate of the area. (1) Fifteen air pollen samples were collected from the northern part of the South China Sea from August to September 2011, and 13 air pollen samples were collected from the southern part of the South China Sea in December 2011. The pollen types were more abundant in the north than in the south. The total pollen number and concentration in the north was 10 times more than that in the south, which may be because of the sampling season. Airborne pollen types and concentrations have a close relationship with wind direction and distance from the sampling point to the continent. (2) Seventy-four samples were collected from surface sediments in the northern part of the South China Sea in the autumn. Thirty-three samples were collected from surface sediments in the southern part of the South China Sea in the winter. Pollen concentrations in the north were nearly 10 times higher than that in the south. This is because trilete spores are transported by rivers from Hainan Island to the sea and also by the summer monsoon-forced marine current. (3) Ten air pollen samples and 10 surface sediments samples were selected for comparison. The pollen and spores in the air were mainly herbaceous and woody pollen, excluding fern spores, having seasonal pollen characteristics. Pollen in the surface sediments were mainly trilete, Pinus, and herbaceous, and may also show a combination of annual pollen characteristics.

  3. Mycobiota and mycotoxins in bee pollen collected from different areas of Slovakia.

    PubMed

    Kačániová, Miroslava; Juráček, Miroslav; Chlebo, Róbert; Kňazovická, Vladimíra; Kadasi-Horáková, Miriam; Kunová, Simona; Lejková, Jadža; Haščík, Peter; Mareček, Ján; Simko, Milan

    2011-01-01

    Contamination by microscopic fungi and mycotoxins in different bee pollen samples, which were stored under three different ways of storing as freezing, drying and UV radiation, was investigated. During spring 2009, 45 samples of bee-collected pollen were gathered from beekeepers who placed their bee colonies on monocultures of sunflower, rape and poppy fields within their flying distance. Bee pollen was collected from bees' legs by special devices placed at the entrance to hives. Samples were examined for the concentration and identification of microscopic fungi able to grow on Malt and Czapek-Dox agar and mycotoxins content [deoxynivalenol (DON), T-2 toxin (T-2), zearalenone (ZON) and total aflatoxins (AFL), fumonisins (FUM), ochratoxins (OTA)] by direct competitive enzyme-linked immunosorbent assays (ELISA). The total number of microscopic fungi in this study ranged from 2.98 ± 0.02 in frozen sunflower bee pollen to 4.06 ± 0.10 log cfu.g(-1) in sunflower bee pollen after UV radiation. In this study, 449 isolates belonging to 21 fungal species representing 9 genera were found in 45 samples of bee pollen. The total isolates were detected in frozen poppy pollen 29, rape pollen 40, sunflower pollen 80, in dried poppy pollen 12, rape pollen 36, sunflower 78, in poppy pollen after UV radiation treatment 54, rape 59 and sunflower 58. The most frequent isolates of microscopic fungi found in bee pollen samples of all prevalent species were Mucor mucedo (49 isolates), Alternaria alternata (40 isolates), Mucor hiemalis (40 isolates), Aspergillus fumigatus (33 isolates) and Cladosporium cladosporioides (31 isolates). The most frequently found isolates were detected in sunflower bee pollen frozen (80 isolates) and the lowest number of isolates was observed in poppy bee pollen dried (12 isolates). The most prevalent mycotoxin of poppy bee pollen was ZON (361.55 ± 0.26 μg.kg(-1)), in rape bee pollen T-2 toxin (265.40 ± 0.18 μg.kg(-1)) and in sunflower bee pollen T-2 toxin

  4. Comparison between Agrobacterium-mediated and direct gene transfer using the gene gun.

    PubMed

    Gao, Caixia; Nielsen, Klaus K

    2013-01-01

    Agrobacterium-mediated transformation and direct gene transfer using the gene gun (microparticle -bombardment) are the two most widely used methods for plant genetic modification. The Agrobacterium method has been successfully practiced in dicots for many years, but only recently have efficient protocols been developed for grasses. Microparticle bombardment has evolved as a method delivering exogenous nucleic acids into plant genome and is a commonly employed technique in plant science. Here these two systems are compared for transformation efficiency, transgene integration, and transgene expression when used to transform tall fescue (Festuca arundinacea Schreb.). The tall fescue transformation protocols lead to the production of large numbers of fertile, independent transgenic lines. PMID:23104329

  5. CHARACTERIZATION OF THE MAIZE POLLEN TRANSCRIPTOME

    EPA Science Inventory

    Pollen is a primary vehicle for transgene flow from engineered plants to their non-transgenic, native or weedy relatives. Hence, gene flow will be affected by pollen fitness (e.g., how well a particular pollen grain can outcompete other pollen present on the stigma and complete ...

  6. A Simple Method for Collecting Airborne Pollen

    ERIC Educational Resources Information Center

    Kevan, Peter G.; DiGiovanni, Franco; Ho, Rong H.; Taki, Hisatomo; Ferguson, Kristyn A.; Pawlowski, Agata K.

    2006-01-01

    Pollination is a broad area of study within biology. For many plants, pollen carried by wind is required for successful seed set. Airborne pollen also affects human health. To foster studies of airborne pollen, we introduce a simple device--the "megastigma"--for collecting pollen from the air. This device is flexible, yielding easily obtained data…

  7. Direct detection signatures of self-interacting dark matter with a light mediator

    NASA Astrophysics Data System (ADS)

    Del Nobile, Eugenio; Kaplinghat, Manoj; Yu, Hai-Bo

    2015-10-01

    Self-interacting dark matter (SIDM) is a simple and well-motivated scenario that could explain long-standing puzzles in structure formation on small scales. If the required self-interaction arises through a light mediator (with mass ~ 10 MeV) in the dark sector, this new particle must be unstable to avoid overclosing the universe. The decay of the light mediator could happen due to a weak coupling of the hidden and visible sectors, providing new signatures for direct detection experiments. The SIDM nuclear recoil spectrum is more peaked towards low energies compared to the usual case of contact interactions, because the mediator mass is comparable to the momentum transfer of nuclear recoils. We show that the SIDM signal could be distinguished from that of DM particles with contact interactions by considering the time-average energy spectrum in experiments employing different target materials, or the average and modulated spectra in a single experiment. Using current limits from LUX and SuperCDMS, we also derive strong bounds on the mixing parameter between hidden and visible sector.

  8. Direct detection signatures of self-interacting dark matter with a light mediator

    SciTech Connect

    Nobile, Eugenio Del; Kaplinghat, Manoj; Yu, Hai-Bo

    2015-10-27

    Self-interacting dark matter (SIDM) is a simple and well-motivated scenario that could explain long-standing puzzles in structure formation on small scales. If the required self-interaction arises through a light mediator (with mass ∼10 MeV) in the dark sector, this new particle must be unstable to avoid overclosing the universe. The decay of the light mediator could happen due to a weak coupling of the hidden and visible sectors, providing new signatures for direct detection experiments. The SIDM nuclear recoil spectrum is more peaked towards low energies compared to the usual case of contact interactions, because the mediator mass is comparable to the momentum transfer of nuclear recoils. We show that the SIDM signal could be distinguished from that of DM particles with contact interactions by considering the time-average energy spectrum in experiments employing different target materials, or the average and modulated spectra in a single experiment. Using current limits from LUX and SuperCDMS, we also derive strong bounds on the mixing parameter between hidden and visible sector.

  9. Oxytropism: a new twist in pollen tube orientation

    NASA Technical Reports Server (NTRS)

    Blasiak, J.; Mulcahy, D. L.; Musgrave, M.

    2001-01-01

    Chemical gradients and structural features within the pistil have been previously proposed as factors determining the directionality of pollen tube growth. In this study, we examine the behavior of pollen of eight species germinated in a dynamic oxygen gradient. While the germination rates of some species decreased directly with decreasing oxygen tension, other species showed no decrease in germination at oxygen tensions as low as 2 kPa. In one species, germination was consistently greater at decreased oxygen tensions than at ambient atmospheric levels. In three of the eight species tested, the developing pollen tube showed clear directional growth away from the more-oxygenated regions of the growth medium, while in one species growth was towards the more-oxygenated region. The remaining four species showed random tube growth. The pattern of oxytropic responses among the taxa suggests that this tropic behavior is both widespread and phylogenetically unpredictable.

  10. Pollen specificity elements reside in 30 bp of the proximal promoters of two pollen-expressed genes.

    PubMed

    Eyal, Y; Curie, C; McCormick, S

    1995-03-01

    Functional analyses previously identified minimal promoter regions required for maintaining high-level expression of the late anther tomato LAT52 and LAT59 genes in tomato pollen. Here, we now define elements that direct pollen specificity. We used a transient assay system consisting of two cell types that differentially express the LAT genes and both "loss-of-function" and "gain-of-function" approaches. Linker substitution mutants analyzed in the transient assay and in transgenic plants identified 30-bp proximal promoter regions of LAT52 and LAT59 that are essential for their expression in pollen and that confer pollen specificity when fused to the heterologous cauliflower mosaic virus 35S core promoter. In vivo competition experiments demonstrated that a common trans-acting factor interacts with the pollen specificity region of both LAT gene promoters and suggested that a common mechanism regulates their coordinate expression. Adjacent upstream elements, the 52/56 box in LAT52 and the 56/59 box in LAT59, are involved in modulating the level of expression in pollen. The 52/56 box may be a target for the binding of a member of the GT-1 transcription factor family. PMID:7734969

  11. Pollen specificity elements reside in 30 bp of the proximal promoters of two pollen-expressed genes.

    PubMed Central

    Eyal, Y; Curie, C; McCormick, S

    1995-01-01

    Functional analyses previously identified minimal promoter regions required for maintaining high-level expression of the late anther tomato LAT52 and LAT59 genes in tomato pollen. Here, we now define elements that direct pollen specificity. We used a transient assay system consisting of two cell types that differentially express the LAT genes and both "loss-of-function" and "gain-of-function" approaches. Linker substitution mutants analyzed in the transient assay and in transgenic plants identified 30-bp proximal promoter regions of LAT52 and LAT59 that are essential for their expression in pollen and that confer pollen specificity when fused to the heterologous cauliflower mosaic virus 35S core promoter. In vivo competition experiments demonstrated that a common trans-acting factor interacts with the pollen specificity region of both LAT gene promoters and suggested that a common mechanism regulates their coordinate expression. Adjacent upstream elements, the 52/56 box in LAT52 and the 56/59 box in LAT59, are involved in modulating the level of expression in pollen. The 52/56 box may be a target for the binding of a member of the GT-1 transcription factor family. PMID:7734969

  12. Grass Pollen Allergens

    PubMed Central

    Augustin, Rosa; Hayward, Barbara J.

    1962-01-01

    Cocksfoot and Timothy pollen extracts are each found to contain at least fifteen components antigenic in rabbits. Most of these can also be allergens for man, but only a few are regularly so. These `principal' allergens have now been isolated in highly purified form. Procedures are given for a simple method of preparing extracts for clinical purposes and for the partial separation, concentration and purification of the allergens by means of differential extractions of the pollens and by means of ultrafiltration, isoelectric precipitation and salt fractionations (at acid and neutral pH) of the extracts. Isoelectric precipitations gave highly pigmented acid complexes, two of which moved as single sharp peaks at pH 7.4 in free electrophoresis, but proved to be hardly active by skin tests. Acid NaCl fractionation of the remainder resulted for Cocksfoot and Timothy in the isolation of a nearly white powder (T21.111121112 = T21B) which was weight for weight 1000–10,000 times as active as the pollen from which it had been derived. The powders have retained their activity for 7 years. By gel diffusion tests, they were found to contain two antigens (one in each preparation) which were immunologically partially related, but the Timothy preparation contained in addition the `innermost' `twin' antigens specific for Timothy that we had discovered previously in the crude extracts by gel diffusion methods. Skin reactions could be elicited in hay-fever subjects by prick tests with concentrations of 10-9–10-8 g./ml., which is equivalent to intradermal injections of 10-11–10-10 mg. and represents a 300-fold purification with respect to the concentrates of crude pollen extracts prepared by ultrafiltration and dialysis. Fractionation on DEAE-cellulose of one of the highly purified Timothy preparations (T21.11112112 = T21A) and other, crude Timothy and Cocksfoot extracts resulted in considerable and reproducible separation of the various antigens, with no indication of the

  13. A Taxonomic Reduced-Space Pollen Model for Paleoclimate Reconstruction

    NASA Astrophysics Data System (ADS)

    Wahl, E. R.; Schoelzel, C.

    2010-12-01

    a BHM framework. The ratio model can directly reconstruct past temperature by solving the GLM equations for T as a function of α, β, and E(r|T): T = {ln[E(r|T)/{1-E(r|T)}]-α}/β. To enable use in paleoreconstruction, the observed r values from fossil pollen data are, by assumption, treated as unbiased estimators of the true r value at each time sampled, which can be substituted for E(r|T). Uncertainty in this reconstruction is systematically evaluated in two parts: 1) the observed r values and their corresponding n values are input as parameters into the binomial distribution, Monte Carlo random pollen count draws are made, and a new ratio value is determined for each iteration; and 2) in the "traditional" GLM the estimated SEs for α and β are used with the α and β EV estimates to yield Monte Carlo random draws for each binomial draw (assuming α and β are Gaussian), in the Bayesian GLM random draws for α and β are taken directly from their estimated posterior distribution. Both methods yield nearly identical reconstructions from varved lakes in Wisconsin where the model has been tested; slightly narrower uncertainty ranges are produced by the Bayesian model. The Little Ice Age is readily identified. Pine:Oak and Fir:Oak versions of the model used in S. California show differences from MAT-based reconstructions.

  14. Initiation of Apoptosis by Granzyme B Requires Direct Cleavage of Bid, but Not Direct Granzyme B–Mediated Caspase Activation

    PubMed Central

    Sutton, Vivien R.; Davis, Joanne E.; Cancilla, Michael; Johnstone, Ricky W.; Ruefli, Astrid A.; Sedelies, Karin; Browne, Kylie A.; Trapani, Joseph A.

    2000-01-01

    The essential upstream steps in granzyme B–mediated apoptosis remain undefined. Herein, we show that granzyme B triggers the mitochondrial apoptotic pathway through direct cleavage of Bid; however, cleavage of procaspases was stalled when mitochondrial disruption was blocked by Bcl-2. The sensitivity of granzyme B–resistant Bcl-2–overexpressing FDC-P1 cells was restored by coexpression of wild-type Bid, or Bid with a mutation of its caspase-8 cleavage site, and both types of Bid were cleaved. However, Bid with a mutated granzyme B cleavage site remained intact and did not restore apoptosis. Bid with a mutation preventing its interaction with Bcl-2 was cleaved but also failed to restore apoptosis. Rapid Bid cleavage by granzyme B (<2 min) was not delayed by Bcl-2 overexpression. These results clearly placed Bid cleavage upstream of mitochondrial Bcl-2. In granzyme B–treated Jurkat cells, endogenous Bid cleavage and loss of mitochondrial membrane depolarization occurred despite caspase inactivation with z-Val-Ala-Asp-fluoromethylketone or Asp-Glu-Val-Asp-fluoromethylketone. Initial partial processing of procaspase-3 and -8 was observed irrespective of Bcl-2 overexpression; however, later processing was completely abolished by Bcl-2. Overall, our results indicate that mitochondrial perturbation by Bid is necessary to achieve a lethal threshold of caspase activity and cell death due to granzyme B. PMID:11085743

  15. Sensitivity analysis for direct and indirect effects in the presence of exposure-induced mediator-outcome confounders

    PubMed Central

    Chiba, Yasutaka

    2014-01-01

    Questions of mediation are often of interest in reasoning about mechanisms, and methods have been developed to address these questions. However, these methods make strong assumptions about the absence of confounding. Even if exposure is randomized, there may be mediator-outcome confounding variables. Inference about direct and indirect effects is particularly challenging if these mediator-outcome confounders are affected by the exposure because in this case these effects are not identified irrespective of whether data is available on these exposure-induced mediator-outcome confounders. In this paper, we provide a sensitivity analysis technique for natural direct and indirect effects that is applicable even if there are mediator-outcome confounders affected by the exposure. We give techniques for both the difference and risk ratio scales and compare the technique to other possible approaches. PMID:25580387

  16. The Regulation of Vesicle Trafficking by Small GTPases and Phospholipids during Pollen Tube Growth

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Polarized and directional growth of pollen tubes is the only means by which immotile sperm of flowering plants reach the deeply embedded female gametes for fertilization. Vesicle trafficking is among the most critical cellular activities for pollen tube growth. Vesicle trafficking maintains membrane...

  17. The direct and precursor mediated dissociation rates of H2 on a Ni(111) surface.

    PubMed

    Wang, Wenji; Zhao, Yi

    2015-02-28

    The dissociation and recombination rates of physisorbed H2, and the direct and steady state dissociation (i.e., the precursor mediated dissociation) rates of gas phase H2 on Ni(111), as well as the corresponding kinetic isotope effects, are calculated using the quantum instanton method, together with path integral Monte Carlo and adaptive umbrella sampling techniques. All these rates except the recombination one first decrease and then increase with the increasing temperature, and their minimum values appear at about 250, 300 and 250 K, respectively. These non-monotonic behaviors reveal that the quantum effect of H2 should be very remarkable at low temperatures. The steady state rates are smaller than the direct rates at low temperatures, however, they become larger than the direct ones at high temperatures, these two kinds of rates become equal at about 400 and 300 K on the rigid and quantum lattices, respectively. The quantum motion of the lattice can enhance the direct and steady state rates, and it increases the steady state rate much more than the direct one, for instance, the direct and steady state rates on the quantum lattice are 1.30 and 2.08 times larger than that on the rigid one at 300 K. The calculated kinetic isotope effects are much larger than 1, which reveals that H2 always has a larger rate than that of D2, and the direct process predicts much larger kinetic isotope effects than the steady state process at low temperatures. In addition, the kinetic isotope effects are not affected by the lattice motion. PMID:25630487

  18. Glutathione-S-Transferase: A Minor Allergen in Birch Pollen due to Limited Release from Hydrated Pollen

    PubMed Central

    Vejvar, Eva; Kitzmüller, Claudia; Gadermaier, Gabriele; Nagl, Birgit; Vrtala, Susanne; Briza, Peter; Zlabinger, Gerhard J.; Jahn-Schmid, Beatrice; Ferreira, Fatima; Bohle, Barbara

    2014-01-01

    Background Recently, a protein homologous to glutathione-S-transferases (GST) was detected in prominent amounts in birch pollen by proteomic profiling. As members of the GST family are relevant allergens in mites, cockroach and fungi we investigated the allergenic relevance of GST from birch (bGST). Methodology bGST was expressed in Escherichia coli, purified and characterized by mass spectrometry. Sera from 217 birch pollen-allergic patients were tested for IgE-reactivity to bGST by ELISA. The mediator-releasing activity of bGST was analysed with IgE-loaded rat basophil leukaemia cells (RBL) expressing human FcεRI. BALB/c mice were immunized with bGST or Bet v 1. Antibody and T cell responses to either protein were assessed. IgE-cross-reactivity between bGST with GST from house dust mite, Der p 8, was studied with murine and human sera in ELISA. The release kinetics of bGST and Bet v 1 from birch pollen were assessed in water, simulated lung fluid, 0.9% NaCl and PBS. Eluted proteins were quantified by ELISA and analysed by immunoblotting. Principle findings Only 13% of 217 birch pollen-allergic patients showed IgE-reactivity to bGST. In RBL assays bGST induced mediator release. Immunization of mice with bGST induced specific IgE and a Th2-dominated cellular immune response comparably to immunization with Bet v 1. bGST did not cross-react with Der p 8. In contrast to Bet v 1, only low amounts of bGST were released from pollen grains upon incubation in water and the different physiological solutions. Conclusion/Significance Although bGST is abundant in birch pollen, immunogenic in mice and able to induce mediator release from effector cells passively loaded with specific IgE, it is a minor allergen for birch pollen-allergic patients. We refer this discrepancy to its limited release from hydrated pollen. Hence, bGST is an example demonstrating that allergenicity depends mainly on rapid elution from airborne particles. PMID:25275548

  19. Influence of wind velocity on pollen concentration in urban canopy layer

    NASA Astrophysics Data System (ADS)

    Pospisil, J.; Jícha, M.

    2009-09-01

    POLLEN RELEASE Temperature is the basic parameter for prediction of the beginning of the pollen season and identification days with good potential for pollen release. Different approaches are used for determination of the start of the pollen season: i) the sum of daily pollen counts = x criterion (Arnold 2002), ii) the mean temperature method during pre-defined period (Sparks, 2000), iii) the temperature sum method (Jones 1992). Another parameters influencing pollen release are: day light length, morning temperature gradient, relative humidity. The mentioned parameters enable to create the "statistical” model for determination of timing of pollen potential release. But, the correct determination of pollen release timing is only the first step to correct prediction of pollen concentration in air. The above mentioned collection of parameters isn't complete for correct pollen production prediction without inclusion of the actual wind velocity. The wind velocity directly influences the pollen release rate from mother plant and subsequently transport of pollen grains. From this reason, influence of wind conditions has to be considered as exactly as possible in complex prediction models. WIND VELOCITY AND POLLEN CONCENTRATION Results of in-situ measurements were used for carried out analysis of the relation between wind velocity and pollen concentration in an urban canopy layer. The mean daily wind velocities and the mean daily pollen concentrations were used as the input data describing the pollen season 2005 in an inner part of the city of Brno (pop. 400 000). The mean daily pollen concentrations were matched to corresponding mean daily wind velocity and depicted in graphs. This procedure was done for all locally monitored aeroallergens, namely Alnus, Ambrosia, Betula, Artemis, Corylus, Fraxinus, Poaceae and Quercus. Only days with significant pollen concentration (above 10% of maximal pollen season concentration) were considered for detail analysis. Clear

  20. Seasonal variation of birch and grass pollen loads and allergen release at two sites in the German Alps

    NASA Astrophysics Data System (ADS)

    Jochner, Susanne; Lüpke, Marvin; Laube, Julia; Weichenmeier, Ingrid; Pusch, Gudrun; Traidl-Hoffmann, Claudia; Schmidt-Weber, Carsten; Buters, Jeroen T. M.; Menzel, Annette

    2015-12-01

    Less vegetated mountainous areas may provide better conditions for allergy sufferers. However, atmospheric transport can result in medically relevant pollen loads in such regions. The majority of investigations has focused on the pollen load, expressed as daily averages of pollen per cubic meter of air (pollen grains/m³); however, the severity of allergic symptoms is also determined by the actual allergen content of this pollen, its pollen potency, which may differ between high and low altitudes. We analysed airborne birch and grass pollen concentrations along with allergen content (birch: Bet v 1, grass: Phl p 5) at two different altitudes (734 and 2650 m a.s.l.) in the Zugspitze region (2009-2010). Back-trajectories were calculated for the high altitude site and for specific days with abrupt increases in pollen potency. We observed several days with medically relevant pollen concentrations at the highest site. In addition, a few days with pollen were not associated with allergens and vice versa. The calculated seasonal mean allergen release per pollen grain was 1.8-3.3 pg Bet v 1 and 5.7 pg Phl p 5 in the valley and 1.1-3.7 pg Bet v 1 and 0.7-1.5 pg Phl p 5 at the high altitude site. Back-trajectories revealed that high pollen potency at the higher site was generally associated with south-westerly to south-easterly (birch), or northerly (grass) wind directions. By investigating days with sudden increases in pollen potency, however, it was difficult to draw definitive conclusions on long- or short-range transport. Our findings suggest that people allergic to pollen might suffer less at higher altitudes and further indicate that a risk assessment relying on the actual concentration of airborne pollen does not necessarily reflect the actual allergy exposure of individuals.

  1. Simulated environmental criticalities affect transglutaminase of Malus and Corylus pollens having different allergenic potential.

    PubMed

    Iorio, Rosa Anna; Di Sandro, Alessia; Paris, Roberta; Pagliarani, Giulia; Tartarini, Stefano; Ricci, Giampaolo; Serafini-Fracassini, Donatella; Verderio, Elisabetta; Del Duca, Stefano

    2012-02-01

    Increases in temperature and air pollution influence pollen allergenicity, which is responsible for the dramatic raise in respiratory allergies. To clarify possible underlying mechanisms, an anemophilous pollen (hazel, Corylus avellana), known to be allergenic, and an entomophilous one (apple, Malus domestica), the allergenicity of which was not known, were analysed. The presence also in apple pollen of known fruit allergens and their immunorecognition by serum of an allergic patient were preliminary ascertained, resulting also apple pollen potentially allergenic. Pollens were subjected to simulated stressful conditions, provided by changes in temperature, humidity, and copper and acid rain pollution. In the two pollens exposed to environmental criticalities, viability and germination were negatively affected and different transglutaminase (TGase) gel bands were differently immunodetected with the polyclonal antibody AtPng1p. The enzyme activity increased under stressful treatments and, along with its products, was found to be released outside the pollen with externalisation of TGase being predominant in C. avellana, whose grain presents a different cell wall composition with respect to that of M. domestica. A recombinant plant TGase (AtPng1p) stimulated the secreted phospholipase A(2) (sPLA(2)) activity, that in vivo is present in human mucosa and is involved in inflammation. Similarly, stressed pollen, hazel pollen being the most efficient, stimulated to very different extent sPLA(2) activity and putrescine conjugation to sPLA(2). We propose that externalised pollen TGase could be one of the mediators of pollen allergenicity, especially under environmental stress induced by climate changes. PMID:21847612

  2. Direct interactions with both p27 and Cdk2 regulate Spy1-mediated proliferation in vivo and in vitro.

    PubMed

    Al Sorkhy, Mohammad; Fifield, Bre-Anne; Myers, Dorothy; Porter, Lisa A

    2016-01-01

    Families of cyclin-like proteins have emerged that bind and activate cyclin dependent kinases (Cdk)s, directing the phosphorylation of noncanonical Cdk substrates. One of these proteins, Spy1, has demonstrated the unique ability to directly bind and activate both Cdk1 and Cdk2, as well as binding and promoting the degradation of at least one Cdk inhibitor, p27(Kip1). Spy1 accelerates somatic cell growth and proliferation and is implicated in a number of human cancers including the breast, brain and liver. Herein we isolate key residues mediating the direct interaction with p27. We use mutants of Spy1 to determine the physiological role of direct interactions with distinct binding partners Cdk2 and p27. We demonstrate that disrupting the direct interaction with either Spy1 binding partner decreased endogenous activity of Cdk2, as well as Spy1-mediated proliferation. However, only the direct interaction with p27 was essential for Spy1-mediated effects on p27 stability. In vivo neither mutation completely prevented tumorigenesis, although each mutation slowed the rate of Spy1-mediated tumorigenesis and decreased overall tumor volumes. This work supports the conclusion that direct interaction with both p27 and Cdk2 contribute to Spy1-mediated effects on cell growth. It is important to elucidate the dynamics of these interactions and to consider these data when assessing functional outcomes. PMID:26771716

  3. Pollen from accurately dated speleothems supports alpine glacier low-stands during the early Holocene

    NASA Astrophysics Data System (ADS)

    Festi, Daniela; Hoffmann, Dirk L.; Luetscher, Marc

    2016-07-01

    Deciphering pollen assemblages from alpine speleothems holds potential to provide unique information about past vegetation in rapidly changing environments. Here, we reconstruct subsurface aerosol transport at Milchbach cave (Switzerland, 1840 m asl) based on the pollen content of two Holocene stalagmites. We demonstrate that pollen is chiefly associated with bacterially mediated calcite fabrics, typical of a well-ventilated cave system. In contrast, pollen is absent from columnar calcite fabrics confirming that hydrological transport is not a significant process for the incorporation of pollen into speleothems at Milchbach cave. Our results support significant changes in the subsurface ventilation regime, which can be associated with the waxing and waning of Upper Grindelwald glacier. Pollen assemblages obtained from six carbonate sub-samples attest the presence of a mixed deciduous forest in the Grindelwald valley during the early and middle Holocene, in agreement with coeval regional pollen records. This study demonstrates that even small amounts of calcite (0.3-2.8 cm3) are capable of delivering pollen spectra representative of the original vegetation if sufficiently elevated deposition fluxes are provided.

  4. A microsystem-based assay for studying pollen tube guidance in plant reproduction

    NASA Astrophysics Data System (ADS)

    Yetisen, A. K.; Jiang, L.; Cooper, J. R.; Qin, Y.; Palanivelu, R.; Zohar, Y.

    2011-05-01

    We present a novel microsystem-based assay to assess and quantify pollen tube behavior in response to pistil tissues. During plant reproduction, signals from female tissues (pistils) guide the sperm-carrying pollen tube to the egg cell to achieve fertilization and initiate seed development. Existing pollen tube guidance bioassays are performed in an isotropically diffusive environment (for example, a semi in vivo assay in petri dishes) instead of anisotropically diffusive conditions required to characterize guidance signal gradients. Lack of a sensitive pollen tube guidance bioassay has therefore compounded the difficulties of identifying and characterizing the guidance signals that are likely produced in minute quantities by the ovules. We therefore developed a novel microsystem-based assay that mimics the in vivo micro-environment of ovule fertilization by pollen tubes in the model research plant Arabidopsis thaliana. In this microdevice, the pollen tube growth rate, length and ovule targeting frequencies were similar to those obtained using a semi in vivo plate assay. As a direct measure of the microdevice's utility in monitoring pollen tube guidance, we demonstrated that in this device, pollen tubes preferentially enter chambers with unfertilized ovules, suggesting that the pollen tubes sense the concentration gradient and respond to the chemoattractants secreted by unfertilized ovules.

  5. The Metabolic Basis of Pollen Thermo-Tolerance: Perspectives for Breeding

    PubMed Central

    Paupière, Marine J.; van Heusden, Adriaan W.; Bovy, Arnaud G.

    2014-01-01

    Crop production is highly sensitive to elevated temperatures. A rise of a few degrees above the optimum growing temperature can lead to a dramatic yield loss. A predicted increase of 1–3 degrees in the twenty first century urges breeders to develop thermo-tolerant crops which are tolerant to high temperatures. Breeding for thermo-tolerance is a challenge due to the low heritability of this trait. A better understanding of heat stress tolerance and the development of reliable methods to phenotype thermo-tolerance are key factors for a successful breeding approach. Plant reproduction is the most temperature-sensitive process in the plant life cycle. More precisely, pollen quality is strongly affected by heat stress conditions. High temperature leads to a decrease of pollen viability which is directly correlated with a loss of fruit production. The reduction in pollen viability is associated with changes in the level and composition of several (groups of) metabolites, which play an important role in pollen development, for example by contributing to pollen nutrition or by providing protection to environmental stresses. This review aims to underline the importance of maintaining metabolite homeostasis during pollen development, in order to produce mature and fertile pollen under high temperature. The review will give an overview of the current state of the art on the role of various pollen metabolites in pollen homeostasis and thermo-tolerance. Their possible use as metabolic markers to assist breeding programs for plant thermo-tolerance will be discussed. PMID:25271355

  6. Turbulence-induced resonance vibrations cause pollen release in wind-pollinated Plantago lanceolata L. (Plantaginaceae)

    PubMed Central

    Timerman, David; Greene, David F.; Urzay, Javier; Ackerman, Josef D.

    2014-01-01

    In wind pollination, the release of pollen from anthers into airflows determines the quantity and timing of pollen available for pollination. Despite the ecological and evolutionary importance of pollen release, wind–stamen interactions are poorly understood, as are the specific forces that deliver pollen grains into airflows. We present empirical evidence that atmospheric turbulence acts directly on stamens in the cosmopolitan, wind-pollinated weed, Plantago lanceolata, causing resonant vibrations that release episodic bursts of pollen grains. In laboratory experiments, we show that stamens have mechanical properties corresponding to theoretically predicted ranges for turbulence-driven resonant vibrations. The mechanical excitation of stamens at their characteristic resonance frequency caused them to resonate, shedding pollen vigorously. The characteristic natural frequency of the stamens increased over time with each shedding episode due to the reduction in anther mass, which increased the mechanical energy required to trigger subsequent episodes. Field observations of a natural population under turbulent wind conditions were consistent with these laboratory results and demonstrated that pollen is released from resonating stamens excited by small eddies whose turnover periods are similar to the characteristic resonance frequency measured in the laboratory. Turbulence-driven vibration of stamens at resonance may be a primary mechanism for pollen shedding in wind-pollinated angiosperms. The capacity to release pollen in wind can be viewed as a primary factor distinguishing animal- from wind-pollinated plants, and selection on traits such as the damping ratio and flexural rigidity may be of consequence in evolutionary transitions between pollination systems. PMID:25297315

  7. Effects of CO₂ on Acer negundo pollen fertility, protein content, allergenic properties, and carbohydrates.

    PubMed

    Silva, M; Ribeiro, H; Abreu, I; Cruz, A; Esteves da Silva, J C G

    2015-05-01

    Atmospheric gaseous pollutants can induce qualitative and quantitative changes in airborne pollen characteristics. In this work, it was investigated the effects of carbon dioxide (CO2) on Acer negundo pollen fertility, protein content, allergenic properties, and carbohydrates. Pollen was collected directly from the anthers and in vitro exposed to three CO2 levels (500, 1000, and 3000 ppm) for 6 and 24 h in an environmental chamber. Pollen fertility was determined using viability and germination assays, total soluble protein was determined with Coomassie Protein Assay Reagent, and the antigenic and allergenic properties were investigated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and immunological techniques using patients' sera. Also, pollen fructose, sucrose, and glucose values were determined. Carbon dioxide exposure affected negatively pollen fertility, total soluble protein content, and fructose content. The patient sera revealed increased IgE reactivity to proteins of A. negundo pollen exposed to increasing levels of the pollutant. No changes were detected in the SDS-PAGE protein profiles and in sucrose and glucose levels. Our results indicate that increase in atmospheric CO2 concentrations can have a negative influence of some features of A. negundo airborne pollen that can influence the reproductive processes as well as respiratory pollen allergies in the future. PMID:25471717

  8. Pollen Forecast and Dispersion Modelling

    NASA Astrophysics Data System (ADS)

    Costantini, Monica; Di Giuseppe, Fabio; Medaglia, Carlo Maria; Travaglini, Alessandro; Tocci, Raffaella; Brighetti, M. Antonia; Petitta, Marcello

    2014-05-01

    The aim of this study is monitoring, mapping and forecast of pollen distribution for the city of Rome using in-situ measurements of 10 species of common allergenic pollens and measurements of PM10. The production of daily concentration maps, associated to a mobile phone app, are innovative compared to existing dedicated services to people who suffer from respiratory allergies. The dispersal pollen is one of the most well-known causes of allergic disease that is manifested by disorders of the respiratory functions. Allergies are the third leading cause of chronic disease and it is estimated that tens millions of people in Italy suffer from it. Recent works reveal that during the last few years there was a progressive increase of affected subjects, especially in urban areas. This situation may depend: on the ability to transport of pollutants, on the ability to react between pollutants and pollen and from a combination of other irritants, existing in densely populated and polluted urban areas. The methodology used to produce maps is based on in-situ measurements time series relative to 2012, obtained from networks of air quality and pollen stations in the metropolitan area of Rome. The monitoring station aerobiological of University of Rome "Tor Vergata" is located at the Department of Biology. The instrument used to pollen monitoring is a volumetric sampler type Hirst (Hirst 1952), Model 2000 VPPS Lanzoni; the data acquisition is carried out as reported in Standard UNI 11008:2004 - "Qualità dell'aria - Metodo di campionamento e conteggio dei granuli pollinici e delle spore fungine aerodisperse" - the protocol that describes the procedure for measuring of the concentration of pollen grains and fungal spores dispersed into the atmosphere, and reported in the "Manuale di gestione e qualità della R.I.M.A" (Travaglini et. al. 2009). All 10 allergenic pollen are monitored since 1996. At Tor Vergata university is also operating a meteorological station (SP2000, CAE

  9. Pollen taphonomy in a canyon stream

    NASA Astrophysics Data System (ADS)

    Fall, Patricia L.

    1987-11-01

    Surface soil samples from the forested Chuska Mountains to the arid steppe of the Chinle Valley, Northeastern Arizona, show close correlation between modern pollen rain and vegetation. In contrast, modern alluvium is dominated by Pinus pollen throughout the canyon; it reflects neither the surrounding floodplain nor plateau vegetation. Pollen in surface soils is deposited by wind; pollen grains in alluvium are deposited by a stream as sedimentary particles. Clay-size particles correlate significantly with Pinus, Quercus, and Populus pollen. These pollen types settle, as clay does, in slack water. Chenopodiaceae- Amaranthus, Artemisia, other Tubuliflorae, and indeterminate pollen types correlate with sand-size particles, and are deposited by more turbulent water. Fluctuating pollen frequencies in alluvial deposits are related to sedimentology and do not reflect the local or regional vegetation where the sediments were deposited. Alluvial pollen is unreliable for reconstruction of paleoenvironments.

  10. Interpolated Task Effects on Direct and Mediated False Recognition: Effects of Initial Recall, Recognition, and the Ironic Effect of Guessing

    ERIC Educational Resources Information Center

    Huff, Mark J.; Coane, Jennifer H.; Hutchison, Keith A.; Grasser, Elisabeth B.; Blais, Jessica E.

    2012-01-01

    In two experiments, participants studied two types of word lists. Direct lists were taken from the Deese-Roediger-McDermott (DRM) paradigm (e.g., "water", "bridge", "run") and contained words directly related to a nonpresented critical item (CI; e.g., "river", Roediger & McDermott, 1995). Mediated lists (e.g., "faucet", "London", "jog") contained…

  11. The Association of Birth Complications and Externalizing Behavior in Early Adolescents: Direct and Mediating Effects.

    PubMed

    Liu, Jianghong; Raine, Adrian; Wuerker, Anne; Venables, Peter H; Mednick, Sarnoff

    2009-03-01

    Prior studies have shown that birth complications interact with psychosocial risk factors in predisposing to increased externalizing behavior in childhood and criminal behavior in adulthood. However, little is known about the direct relationship between birth complications and externalizing behavior. Furthermore, the mechanism by which the birth complications predispose to externalizing behavior is not well explored. This study aims to assess whether birth complications predispose to early adolescent externalizing behavior and to test whether Intelligence Quotient (IQ) mediates relationships between predictor and outcome variables. We used data from a prospective, longitudinal birth cohort of 1,795 3-year-old boys and girls from Mauritius to test hypotheses. Birth complications were assessed from hospital record data, malnutrition from a pediatric exam at age 3 years, psychosocial adversity from parental interviews at age 3 years, and externalizing behavior problems from parental ratings at age 11 years. We found that babies with birth complications are more likely to develop externalizing behavior problems at age 11. Low IQ was associated with birth complications and was found to mediate the link between early predictors and later externalizing behavior. These prospective, longitudinal findings have potential clinical implications for the identification of early adolescent externalizing behavior and for public health attempts to prevent the occurrence of child externalizing behavior problems. PMID:22485069

  12. Macrophages Mediate the Repair of Brain Vascular Rupture through Direct Physical Adhesion and Mechanical Traction.

    PubMed

    Liu, Chi; Wu, Chuan; Yang, Qifen; Gao, Jing; Li, Li; Yang, Deqin; Luo, Lingfei

    2016-05-17

    Hemorrhagic stroke and brain microbleeds are caused by cerebrovascular ruptures. Fast repair of such ruptures is the most promising therapeutic approach. Due to a lack of high-resolution in vivo real-time studies, the dynamic cellular events involved in cerebrovascular repair remain unknown. Here, we have developed a cerebrovascular rupture system in zebrafish by using multi-photon laser, which generates a lesion with two endothelial ends. In vivo time-lapse imaging showed that a macrophage arrived at the lesion and extended filopodia or lamellipodia to physically adhere to both endothelial ends. This macrophage generated mechanical traction forces to pull the endothelial ends and facilitate their ligation, thus mediating the repair of the rupture. Both depolymerization of microfilaments and inhibition of phosphatidylinositide 3-kinase or Rac1 activity disrupted macrophage-endothelial adhesion and impaired cerebrovascular repair. Our study reveals a hitherto unexpected role for macrophages in mediating repair of cerebrovascular ruptures through direct physical adhesion and mechanical traction. PMID:27156384

  13. Parkin-mediated mitophagy directs perinatal cardiac metabolic maturation in mice.

    PubMed

    Gong, Guohua; Song, Moshi; Csordas, Gyorgy; Kelly, Daniel P; Matkovich, Scot J; Dorn, Gerald W

    2015-12-01

    In developing hearts, changes in the cardiac metabolic milieu during the perinatal period redirect mitochondrial substrate preference from carbohydrates to fatty acids. Mechanisms responsible for this mitochondrial plasticity are unknown. Here, we found that PINK1-Mfn2-Parkin-mediated mitophagy directs this metabolic transformation in mouse hearts. A mitofusin (Mfn) 2 mutant lacking PINK1 phosphorylation sites necessary for Parkin binding (Mfn2 AA) inhibited mitochondrial Parkin translocation, suppressing mitophagy without impairing mitochondrial fusion. Cardiac Parkin deletion or expression of Mfn2 AA from birth, but not after weaning, prevented postnatal mitochondrial maturation essential to survival. Five-week-old Mfn2 AA hearts retained a fetal mitochondrial transcriptional signature without normal increases in fatty acid metabolism and mitochondrial biogenesis genes. Myocardial fatty acylcarnitine levels and cardiomyocyte respiration induced by palmitoylcarnitine were concordantly depressed. Thus, instead of transcriptional reprogramming, fetal cardiomyocyte mitochondria undergo perinatal Parkin-mediated mitophagy and replacement by mature adult mitochondria. Mitophagic mitochondrial removal underlies developmental cardiomyocyte mitochondrial plasticity and metabolic transitioning of perinatal hearts. PMID:26785495

  14. Disentangling direct and growth-mediated influences on early survival: a mechanistic approach.

    PubMed

    Plard, Floriane; Yoccoz, Nigel G; Bonenfant, Christophe; Klein, François; Warnant, Claude; Gaillard, Jean-Michel

    2015-09-01

    1. Early survival is a key life-history trait that often accounts for a large part of the variation in individual fitness and shapes population dynamics. The factors influencing early survival are multiple in large herbivores, including malnutrition, predation, cohort variation or maternal effects. However, the mechanistic pathways connecting these drivers to variation in early survival are much less studied. Indeed, whether these factors influence early survival directly or indirectly through early growth remains to be disentangled. 2. In this study, we used a path analysis to separate the direct and indirect (i.e. mediated by early growth) pathways through which sex, birth date, cohort and family effects influence early survival. We used a large data set of marked roe deer newborns collected from 1985 to 2010 in the intensively monitored population of Trois Fontaines (France). 3. We found that most drivers have indirect influences on early survival through early growth. Indeed, cohort effects influenced early survival through the indirect effect of precipitation around birth on early growth. Precipitation also had direct effects on early survival. Family effects indirectly influenced early survival. Twins from the same litter grew at about the same rate, so they had the same fate. Moreover, some factors, such as birth date, had both direct and indirect effects on roe deer early survival, with fawns born early in the season benefiting from high early survival both because they have more time to grow before the harsh season and because they grow faster during their first days of life than late-born fawns. 4. These findings suggest that most drivers of early survival previously identified in large mammalian herbivores may affect early survival primarily through their influence on early growth. Disentangling the direct and indirect pathways by which different factors influence early survival is of crucial importance to understand the mechanisms shaping this key

  15. Long noncoding RNA hotair mediated angiogenesis in nasopharyngeal carcinoma by direct and indirect signaling pathways

    PubMed Central

    Hu, Bao-guang; Liang, Wei-cheng; Zhu, Xiao; Yang, Hai-di; Li, Gang; Zhang, Jin-fang

    2016-01-01

    Nasopharyngeal carcinoma (NPC), as a unique head and neck cancer type, is particularly prevalent in certain geographic areas such as eastern Asia. Until now, the therapeutic options have been restricted mainly to radiotherapy or chemotherapy. However, the clinical treatment effect remains unsatisfactory even if the combined radio-chemotherapies. Therefore, it is urgently needed to develop effective novel therapies against NPC. In this study, we discovered that lncRNA Hotair was extremely abundant in NPC cells and clinical NPC samples. Further studies showed that Hotair knockdown significantly attenuated both in vitro and in vivo tumor cell growth and angiogenesis. Our study also demonstrated that Hotair promoted angiogenesis through directly activating the transcription of angiogenic factor VEGFA as well as through GRP78-mediated upregulation of VEGFA and Ang2 expression. Therefore, Hotair may serve as a promising diagnostic marker and therapeutic target for NPC patients. PMID:26717040

  16. Identification of the glucosyltransferase that mediates direct flavone C-glucosylation in Gentiana triflora.

    PubMed

    Sasaki, Nobuhiro; Nishizaki, Yuzo; Yamada, Eri; Tatsuzawa, Fumi; Nakatsuka, Takashi; Takahashi, Hideyuki; Nishihara, Masahiro

    2015-01-01

    The major flavonoids accumulated in leaves of Japanese gentian (Gentiana triflora) were determined as isoorientin (luteolin 6-C-glucoside) and isoorientin 4'-glucoside. A cDNA (GtUF6CGT1) was isolated that encoded the UDP-glucose-dependent glucosyltransferase that is involved in C-glycosylflavone biosynthesis. The recombinant GtUF6CGT1 protein could transfer a glucose group to the C6 position of a flavone skeleton through C-linkage, using UDP-glucose as the glucosyl donor. These C-glycosylflavones also accumulated in petals. A good correlation was observed between GtUF6CGT1 expression and C-glycosylflavone accumulation in leaves and petals. GtUF6CGT1 is the first reported C-glucosyltransferase that mediates direct C-glucosylation of the flavone skeleton. PMID:25479084

  17. Silver-mediated direct trifluoromethoxylation of α-diazo esters via the (-)OCF3 anion.

    PubMed

    Zha, Gao-Feng; Han, Jia-Bin; Hu, Xiao-Qian; Qin, Hua-Li; Fang, Wan-Yin; Zhang, Cheng-Pan

    2016-06-14

    Silver-mediated direct trifluoromethoxylation of α-diazo esters and ketosteroid was disclosed. The reactions of alkyl α-diazo arylacetates with AgOCF3 or CF3SO2OCF3/AgF at -30 to 10 °C under a N2 atmosphere provided α-trifluoromethoxyl arylacetates in up to 90% yield, while alkyl α-diazo vinylacetates reacting with CF3SO2OCF3/AgF or AgOCF3 afforded γ-trifluoromethoxyl α,β-unsaturated esters in up to 94% yield. The α-diazo ketosteroid was also trifluoromethoxylated under the standard reaction conditions. This protocol allows for an effective and convenient access to a large number of synthetic building blocks, which are promising in the development of new functional OCF3-molecules. PMID:27121103

  18. Characterizing Aeroallergens by Infrared Spectroscopy of Fungal Spores and Pollen

    PubMed Central

    Zimmermann, Boris; Tkalčec, Zdenko; Mešić, Armin; Kohler, Achim

    2015-01-01

    Background Fungal spores and plant pollen cause respiratory diseases in susceptible individuals, such as asthma, allergic rhinitis and hypersensitivity pneumonitis. Aeroallergen monitoring networks are an important part of treatment strategies, but unfortunately traditional analysis is time consuming and expensive. We have explored the use of infrared spectroscopy of pollen and spores for an inexpensive and rapid characterization of aeroallergens. Methodology The study is based on measurement of spore and pollen samples by single reflectance attenuated total reflectance Fourier transform infrared spectroscopy (SR-ATR FTIR). The experimental set includes 71 spore (Basidiomycota) and 121 pollen (Pinales, Fagales and Poales) samples. Along with fresh basidiospores, the study has been conducted on the archived samples collected within the last 50 years. Results The spectroscopic-based methodology enables clear spectral differentiation between pollen and spores, as well as the separation of confamiliar and congeneric species. In addition, the analysis of the scattering signals inherent in the infrared spectra indicates that the FTIR methodology offers indirect estimation of morphology of pollen and spores. The analysis of fresh and archived spores shows that chemical composition of spores is well preserved even after decades of storage, including the characteristic taxonomy-related signals. Therefore, biochemical analysis of fungal spores by FTIR could provide economical, reliable and timely methodologies for improving fungal taxonomy, as well as for fungal identification and monitoring. This proof of principle study shows the potential for using FTIR as a rapid tool in aeroallergen studies. In addition, the presented method is ready to be immediately implemented in biological and ecological studies for direct measurement of pollen and spores from flowers and sporocarps. PMID:25867755

  19. Direct and Fe(II)-Mediated Reduction of Technetium by Fe(III)-Reducing Bacteria

    PubMed Central

    Lloyd, J. R.; Sole, V. A.; Van Praagh, C. V. G.; Lovley, D. R.

    2000-01-01

    The dissimilatory Fe(III)-reducing bacterium Geobacter sulfurreducens reduced and precipitated Tc(VII) by two mechanisms. Washed cell suspensions coupled the oxidation of hydrogen to enzymatic reduction of Tc(VII) to Tc(IV), leading to the precipitation of TcO2 at the periphery of the cell. An indirect, Fe(II)-mediated mechanism was also identified. Acetate, although not utilized efficiently as an electron donor for direct cell-mediated reduction of technetium, supported the reduction of Fe(III), and the Fe(II) formed was able to transfer electrons abiotically to Tc(VII). Tc(VII) reduction was comparatively inefficient via this indirect mechanism when soluble Fe(III) citrate was supplied to the cultures but was enhanced in the presence of solid Fe(III) oxide. The rate of Tc(VII) reduction was optimal, however, when Fe(III) oxide reduction was stimulated by the addition of the humic analog and electron shuttle anthaquinone-2,6-disulfonate, leading to the rapid formation of the Fe(II)-bearing mineral magnetite. Under these conditions, Tc(VII) was reduced and precipitated abiotically on the nanocrystals of biogenic magnetite as TcO2 and was removed from solution to concentrations below the limit of detection by scintillation counting. Cultures of Fe(III)-reducing bacteria enriched from radionuclide-contaminated sediment using Fe(III) oxide as an electron acceptor in the presence of 25 μM Tc(VII) contained a single Geobacter sp. detected by 16S ribosomal DNA analysis and were also able to reduce and precipitate the radionuclide via biogenic magnetite. Fe(III) reduction was stimulated in aquifer material, resulting in the formation of Fe(II)-containing minerals that were able to reduce and precipitate Tc(VII). These results suggest that Fe(III)-reducing bacteria may play an important role in immobilizing technetium in sediments via direct and indirect mechanisms. PMID:10966385

  20. Pollen mixing in pollen generalist solitary bees: a possible strategy to complement or mitigate unfavourable pollen properties?

    PubMed

    Eckhardt, Michael; Haider, Mare; Dorn, Silvia; Müller, Andreas

    2014-05-01

    Generalist herbivorous insects, which feed on plant tissue that is nutritionally heterogeneous or varies in its content of secondary metabolites, often benefit from dietary mixing through more balanced nutrient intake or reduced exposure to harmful secondary metabolites. Pollen is similarly heterogeneous as other plant tissue in its content of primary and secondary metabolites, suggesting that providing their offspring with mixed pollen diets might be a promising strategy for pollen generalist bees to complement nutrient imbalances or to mitigate harmful secondary metabolites of unfavourable pollen. In the present study, we compared larval performance of the pollen generalist solitary bee species Osmia cornuta (Megachilidae) on five experimental pollen diets that consisted of different proportions of unfavourable pollen diet of Ranunculus acris (Ranunculaceae) and favourable pollen diet of Sinapis arvensis (Brassicaceae). In addition, we microscopically analysed the pollen contained in the scopal brushes of field-collected females of O. cornuta and three closely related species to elucidate to what degree these pollen generalist bees mix pollen of different hosts in their brood cells. In striking contrast to a pure Ranunculus pollen diet, which had a lethal effect on most developing larvae of O. cornuta, larval survival, larval development time and adult body mass of both males and females remained nearly unaffected by the admixture of up to 50% of Ranunculus pollen diet to the larval food. Between 42% and 66% of all female scopal pollen loads analysed contained mixtures of pollen from two to six plant families, indicating that pollen mixing is a common behaviour in O. cornuta and the three related bee species. The present study provides the first evidence that the larvae of pollen generalist bees can benefit from the nutrient content of unfavourable pollen without being negatively affected by its unfavourable chemical properties if such pollen is mixed with

  1. Knockin' on pollen's door: live cell imaging of early polarization events in germinating Arabidopsis pollen

    PubMed Central

    Vogler, Frank; Konrad, Sebastian S. A.; Sprunck, Stefanie

    2015-01-01

    Pollen tubes are an excellent system for studying the cellular dynamics and complex signaling pathways that coordinate polarized tip growth. Although several signaling mechanisms acting in the tip-growing pollen tube have been described, our knowledge on the subcellular and molecular events during pollen germination and growth site selection at the pollen plasma membrane is rather scarce. To simultaneously track germinating pollen from up to 12 genetically different plants we developed an inexpensive and easy mounting technique, suitable for every standard microscope setup. We performed high magnification live-cell imaging during Arabidopsis pollen activation, germination, and the establishment of pollen tube tip growth by using fluorescent marker lines labeling either the pollen cytoplasm, vesicles, the actin cytoskeleton or the sperm cell nuclei and membranes. Our studies revealed distinctive vesicle and F-actin polarization during pollen activation and characteristic growth kinetics during pollen germination and pollen tube formation. Initially, the germinating Arabidopsis pollen tube grows slowly and forms a uniform roundish bulge, followed by a transition phase with vesicles heavily accumulating at the growth site before switching to rapid tip growth. Furthermore, we found the two sperm cells to be transported into the pollen tube after the phase of rapid tip growth has been initiated. The method presented here is suitable to quantitatively study subcellular events during Arabidopsis pollen germination and growth, and for the detailed analysis of pollen mutants with respect to pollen polarization, bulging, or growth site selection at the pollen plasma membrane. PMID:25954283

  2. Selectivity of direct and network-mediated stimulation of the retinal ganglion cells with epi-, sub- and intraretinal electrodes

    NASA Astrophysics Data System (ADS)

    Boinagrov, David; Pangratz-Fuehrer, Susanne; Goetz, Georges; Palanker, Daniel

    2014-04-01

    Objective. Intra-retinal placement of stimulating electrodes can provide close and stable proximity to target neurons. We assessed improvement in stimulation thresholds and selectivity of the direct and network-mediated retinal stimulation with intraretinal electrodes, compared to epiretinal and subretinal placements. Approach. Stimulation thresholds of the retinal ganglion cells (RGCs) in wild-type rat retina were measured using the patch-clamp technique. Direct and network-mediated responses were discriminated using various synaptic blockers. Main results. Three types of RGC responses were identified: short latency (SL, τ < 5 ms) originating in RGCs, medium latency (ML, 3 < τ < 70 ms) originating in the inner nuclear layer and long latency (LL, τ > 40 ms) originating in photoreceptors. Cathodic epiretinal stimulation exhibited the lowest threshold for direct RGC response and the highest direct selectivity (network/direct thresholds ratio), exceeding a factor of 3 with pulse durations below 0.5 ms. For network-mediated stimulation, the lowest threshold was obtained with anodic pulses in OPL position, and its network selectivity (direct/network thresholds ratio) increased with pulse duration, exceeding a factor of 4 at 10 ms. Latency of all three types of responses decreased with increasing strength of the stimulus. Significance. These results define the optimal range of pulse durations, pulse polarities and electrode placement for the retinal prostheses aiming at direct or network-mediated stimulation of RGCs.

  3. Iron-mediated oxidative C-H coupling of arenes and alkenes directed by sulfur: an expedient route to dihydrobenzofurans.

    PubMed

    Cavanagh, Craig W; Aukland, Miles H; Laurent, Quentin; Hennessy, Alan; Procter, David J

    2016-06-21

    A novel route to medicinally-relevant dihydrobenzofurans utilises a sulfur-directed C-H ortho-coupling of arenes and unactivated terminal alkenes mediated by iron, and a palladium-catalysed deallylation/heterocyclisation sequence. The iron-mediated coupling affords linear products of alkene chloroarylation in good yield and with complete regioselectivity. The coupling likely proceeds by redox-activation of the arene partner by iron(iii) and alkene addition to the resultant radical cation. PMID:27198174

  4. An algorithm for estimating potential deposition of corn pollen for environmental assessment.

    PubMed

    Kawashima, Shigeto; Matsuo, Kazuhito; Du, Mingyuan; Takahashi, Yuichi; Inoue, Satoshi; Yonemura, Seiichiro

    2004-01-01

    The safety and impact on the environment of transgenic crops are important issues, and studies have shown that pollen from transgenic Bt (Bacillus thuringiensis) corn (Zea mays L.) may kill nontarget insects. To develop an algorithm for assessing the environmental effect of transgenic crops, we arranged a field experiment in Tsukuba, Japan. Pollen dispersal and deposition were measured inside and outside a cornfield throughout the flowering period. Weather conditions such as wind speed and direction were measured at the same time. Pollen dispersal peaked 1 week after the start of flowering and continued for 12 days thereafter. The variation in daily pollen dispersal was similar at all observation points. Both pollen dispersal and deposition decreased exponentially with distance from the cornfield on all days. We estimated potential pollen deposition with a quasi-mechanistic model that incorporates the effects of wind direction, wind speed, and flowering intensity. The daily potential deposition was summed over the flowering period, and then the relationship between distance from the cornfield and the integrated potential deposition was estimated. It was possible to show the effective area of the environmental risk zone posed by genetically modified pollen by combining the distance/deposition relationship with the dose/response relationship derived from a laboratory assay. The algorithm described here can be applied to various wind-pollinated plants to estimate both potential and integrated pollen deposition. PMID:16028796

  5. Hydrogen peroxide affects ion channels in lily pollen grain protoplasts.

    PubMed

    Breygina, M A; Abramochkin, D V; Maksimov, N M; Yermakov, I P

    2016-09-01

    Ion homeostasis plays a central role in polarisation and polar growth. In several cell types ion channels are controlled by reactive oxygen species (ROS). One of the most important cells in the plant life cycle is the male gametophyte, which grows under the tight control of both ion fluxes and ROS balance. The precise relationship between these two factors in pollen tubes has not been completely elucidated, and in pollen grains it has never been studied to date. In the present study we used a simple model - protoplasts obtained from lily pollen grains at the early germination stage - to reveal the effect of H2 O2 on cation fluxes crucial for pollen germination. Here we present direct evidence for two ROS-sensitive currents on the pollen grain plasma membrane: the hyperpolarisation-activated calcium current, which is strongly enhanced by H2 O2 , and the outward potassium current, which is modestly enhanced by H2 O2 . We used low concentrations of H2 O2 that do not cause an intracellular oxidative burst and do not damage cells, as demonstrated with fluorescent staining. PMID:27115728

  6. Personalized symptoms forecasting for pollen-induced allergic rhinitis sufferers

    NASA Astrophysics Data System (ADS)

    Voukantsis, D.; Berger, U.; Tzima, F.; Karatzas, K.; Jaeger, S.; Bergmann, K. C.

    2015-07-01

    Hay fever is a pollen-induced allergic reaction that strongly affects the overall quality of life of many individuals. The disorder may vary in severity and symptoms depending on patient-specific factors such as genetic disposition, individual threshold of pollen concentration levels, medication, former immunotherapy, and others. Thus, information services that improve the quality of life of hay fever sufferers must address the needs of each individual separately. In this paper, we demonstrate the development of information services that offer personalized pollen-induced symptoms forecasts. The backbone of these services consists of data of allergic symptoms reported by the users of the Personal Hay Fever Diary system and pollen concentration levels (European Aeroallergen Network) in several sampling sites. Data were analyzed using computational intelligence methods, resulting in highly customizable forecasting models that offer personalized warnings to users of the Patient Hay Fever Diary system. The overall system performance for the pilot area (Vienna and Lower Austria) reached a correlation coefficient of r = 0.71 ± 0.17 (average ± standard deviation) in a sample of 219 users with major contribution to the Pollen Hay Fever Diary system and an overall performance of r = 0.66 ± 0.18 in a second sample of 393 users, with minor contribution to the system. These findings provide an example of combining data from different sources using advanced data engineering in order to develop innovative e-health services with the capacity to provide more direct and personalized information to allergic rhinitis sufferers.

  7. Direct and third-body mediated resonance energy transfer in dimensionally constrained nanostructures

    NASA Astrophysics Data System (ADS)

    Weeraddana, Dilusha; Premaratne, Malin; Andrews, David L.

    2015-07-01

    The process of resonance energy transfer (RET) in a nanostructure influenced by a vicinal, nonabsorbing third body is studied within the framework of molecular quantum electrodynamics. Direct RET and the influence of neighboring matter have been studied previously, mainly for molecules. However, a complete study or unified understanding of direct and indirect RET in nanostructures with different dimensionalities is still lacking. Therefore, there is a strong need for a complete theory that models RET for the cases of quantum wells, nanowires, and quantum dots. We construct a detailed picture of excitation energy transfer in nanostructures and how it is affected by another quantum object, which includes the derivation of quantum amplitudes based on second- and fourth-order time-dependent perturbation theories, and the derivation of transfer rates and distance dependencies, providing a complete picture and understanding of RET in nanostructures. The results of the derivations indicate that the dimensionality of the nanostructure determines the controllability of the RET rate. Furthermore, third-body mediation leads to a nonvanishing RET in the coupling of nanowire to nanowire and quantum dot to quantum dot.

  8. Direct binding with HDAC6 mediates the reversible recruitment of parkin to the centrosome

    PubMed Central

    Jiang, Qian; Ren, Yong; Feng, Jian

    2009-01-01

    Histone deacetylase 6 (HDAC6), a microtubule-associated tubulin deacetylase, plays a significant role in the formation of protein aggregates in many neurodegenerative disorders. Parkin, a protein-ubiquitin E3 ligase linked to Parkinson’s disease, accumulates at the centrosome in a microtubule-dependent manner in response to proteasome inhibition. Here, we show that the centrosome recruitment of parkin was mediated by its direct binding to HDAC6 through multiple interaction domains. The tubulin deacetylase activity of HDAC6 was required for the accumulation of parkin as well as its dispersion upon the reversal of proteasome inhibition. The bidirectional movements of parkin required intact microtubule network and were dependent on dynein and kinesin 1, respectively. Tubulin deacetylation increases microtubule dynamicity and may thus facilitate microtubule-based trafficking of the parkin-HDAC6 complex. The results suggest that HDAC6 acts as a sensor of proteasome inhibition and directs the trafficking of parkin by utilizing different motor proteins. PMID:19036992

  9. Polarized exocyst-mediated vesicle fusion directs intracellular lumenogenesis within the C. elegans excretory cell

    PubMed Central

    Armenti, Stephen T.; Chan, Emily; Nance, Jeremy

    2015-01-01

    Lumenogenesis of small seamless tubes occurs through intracellular membrane growth and directed vesicle fusion events. Within the C. elegans excretory cell, which forms seamless intracellular tubes (canals) that mediate osmoregulation, lumens grow in length and diameter when vesicles fuse with the expanding lumenal surface. Here, we show that lumenal vesicle fusion depends on the small GTPase RAL-1, which localizes to vesicles and acts through the exocyst vesicle-tethering complex. Loss of either the exocyst or RAL-1 prevents excretory canal lumen extension. Within the excretory canal and other polarized cells, the exocyst co-localizes with the PAR polarity proteins PAR-3, PAR-6 and PKC-3. Using early embryonic cells to determine the functional relationships between the exocyst and PAR proteins, we show that RAL-1 recruits the exocyst to the membrane, while PAR proteins concentrate membrane-localized exocyst proteins to a polarized domain. These findings reveal that RAL-1 and the exocyst direct the polarized vesicle fusion events required for intracellular lumenogenesis of the excretory cell, suggesting mechanistic similarities in the formation of topologically distinct multicellular and intracellular lumens. PMID:25102190

  10. Towards direct synthesis of alane: A predicted defect-mediated pathway confirmed experimentally

    DOE PAGESBeta

    Wang, Lin -Lin; Herwadkar, Aditi; Reich, Jason M.; Johnson, Duane D.; House, Stephen D.; Pena-Martin, Pamela; Rockett, Angus A.; Robertson, Ian M.; Gupta, Shalabh; Pecharsky, Vitalij K.

    2016-08-18

    Here, alane (AlH3) is a unique energetic material that has not found a broad practical use for over 70 years because it is difficult to synthesize directly from its elements. Using density functional theory, we examine the defect-mediated formation of alane monomers on Al(111) in a two-step process: (1) dissociative adsorption of H2 and (2) alane formation, which are both endothermic on a clean surface. Only with Ti dopant to facilitate H2 dissociation and vacancies to provide Al adatoms, both processes become exothermic. In agreement, in situ scanning tunneling microscopy showed that during H2 exposure, alane monomers and clusters formmore » primarily in the vicinity of Al vacancies and Ti atoms. Moreover, ball milling of the Al samples with Ti (providing necessary defects) showed a 10 % conversion of Al into AlH3 or closely related species at 344 bar H2, indicating that the predicted pathway may lead to the direct synthesis of alane from elements at pressures much lower than the 104 bar expected from bulk thermodynamics.« less

  11. Towards Direct Synthesis of Alane: A Predicted Defect-Mediated Pathway Confirmed Experimentally.

    PubMed

    Wang, Lin-Lin; Herwadkar, Aditi; Reich, Jason M; Johnson, Duane D; House, Stephen D; Peña-Martin, Pamela; Rockett, Angus A; Robertson, Ian M; Gupta, Shalabh; Pecharsky, Vitalij K

    2016-09-01

    Alane (AlH3 ) is a unique energetic material that has not found a broad practical use for over 70 years because it is difficult to synthesize directly from its elements. Using density functional theory, we examine the defect-mediated formation of alane monomers on Al(111) in a two-step process: (1) dissociative adsorption of H2 and (2) alane formation, which are both endothermic on a clean surface. Only with Ti dopant to facilitate H2 dissociation and vacancies to provide Al adatoms, both processes become exothermic. In agreement, in situ scanning tunneling microscopy showed that during H2 exposure, alane monomers and clusters form primarily in the vicinity of Al vacancies and Ti atoms. Moreover, ball milling of the Al samples with Ti (providing necessary defects) showed a 10 % conversion of Al into AlH3 or closely related species at 344 bar H2 , indicating that the predicted pathway may lead to the direct synthesis of alane from elements at pressures much lower than the 10(4)  bar expected from bulk thermodynamics. PMID:27535100

  12. Polarized exocyst-mediated vesicle fusion directs intracellular lumenogenesis within the C. elegans excretory cell.

    PubMed

    Armenti, Stephen T; Chan, Emily; Nance, Jeremy

    2014-10-01

    Lumenogenesis of small seamless tubes occurs through intracellular membrane growth and directed vesicle fusion events. Within the Caenorhabditis elegans excretory cell, which forms seamless intracellular tubes (canals) that mediate osmoregulation, lumens grow in length and diameter when vesicles fuse with the expanding lumenal surface. Here, we show that lumenal vesicle fusion depends on the small GTPase RAL-1, which localizes to vesicles and acts through the exocyst vesicle-tethering complex. Loss of either the exocyst or RAL-1 prevents excretory canal lumen extension. Within the excretory canal and other polarized cells, the exocyst co-localizes with the PAR polarity proteins PAR-3, PAR-6 and PKC-3. Using early embryonic cells to determine the functional relationships between the exocyst and PAR proteins, we show that RAL-1 recruits the exocyst to the membrane, while PAR proteins concentrate membrane-localized exocyst proteins to a polarized domain. These findings reveal that RAL-1 and the exocyst direct the polarized vesicle fusion events required for intracellular lumenogenesis of the excretory cell, suggesting mechanistic similarities in the formation of topologically distinct multicellular and intracellular lumens. PMID:25102190

  13. Bioassaying for ozone with pollen systems

    SciTech Connect

    Feder, W.A.

    1981-01-01

    Sensitivity to ozone of pollen germinating in vitro is closely correlated with ozone sensitivity of the pollen parent. Ozone-sensitive and tolerant pollen populations have been identified in tobacco, petunia, and tomato cultivars. The rate of tube elongation can be reversibly slowed or stopped by exposure to low concentrations of ozone. The performance of selected pollen populations can then be used to bioassay ozone in ambient air by introducing the air sample into a growth chamber where ozone-sensitive pollen in growing. Year-round pollen producion can be achieved in the greenhouse. Harvested pollen can be tested, packaged, and transported to user facilities without loss of vigor. Pollen populations are inexpensive to produce, respond reliably, and are simple to use as a bioassay for air quality.

  14. Tip-localized receptors control pollen tube growth and LURE sensing in Arabidopsis.

    PubMed

    Takeuchi, Hidenori; Higashiyama, Tetsuya

    2016-03-10

    Directional control of tip-growing cells is essential for proper tissue organization and cell-to-cell communication in animals and plants. In the sexual reproduction of flowering plants, the tip growth of the male gametophyte, the pollen tube, is precisely guided by female cues to achieve fertilization. Several female-secreted peptides have recently been identified as species-specific attractants that directly control the direction of pollen tube growth. However, the method by which pollen tubes precisely and promptly respond to the guidance signal from their own species is unknown. Here we show that tip-localized pollen-specific receptor-like kinase 6 (PRK6) with an extracellular leucine-rich repeat domain is an essential receptor for sensing of the LURE1 attractant peptide in Arabidopsis thaliana under semi-in-vivo conditions, and is important for ovule targeting in the pistil. PRK6 interacted with pollen-expressed ROPGEFs (Rho of plant guanine nucleotide-exchange factors), which are important for pollen tube growth through activation of the signalling switch Rho GTPase ROP1 (refs 7, 8). PRK6 conferred responsiveness to AtLURE1 in pollen tubes of the related species Capsella rubella. Furthermore, our genetic and physiological data suggest that PRK6 signalling through ROPGEFs and sensing of AtLURE1 are achieved in cooperation with the other PRK family receptors, PRK1, PRK3 and PRK8. Notably, the tip-focused PRK6 accumulated asymmetrically towards an external AtLURE1 source before reorientation of pollen tube tip growth. These results demonstrate that PRK6 acts as a key membrane receptor for external AtLURE1 attractants, and recruits the core tip-growth machinery, including ROP signalling proteins. This work provides insights into the orchestration of efficient pollen tube growth and species-specific pollen tube attraction by multiple receptors during male-female communication. PMID:26961657

  15. Sinorhizobium meliloti Chemoreceptor McpU Mediates Chemotaxis toward Host Plant Exudates through Direct Proline Sensing

    PubMed Central

    Webb, Benjamin A.; Hildreth, Sherry; Helm, Richard F.

    2014-01-01

    Bacterial chemotaxis is an important attribute that aids in establishing symbiosis between rhizobia and their legume hosts. Plant roots and seeds exude a spectrum of molecules into the soil to attract their bacterial symbionts. The alfalfa symbiont Sinorhizobium meliloti possesses eight chemoreceptors to sense its environment and mediate chemotaxis toward its host. The methyl accepting chemotaxis protein McpU is one of the more abundant S. meliloti chemoreceptors and an important sensor for the potent attractant proline. We established a dominant role of McpU in sensing molecules exuded by alfalfa seeds. Mass spectrometry analysis determined that a single germinating seed exudes 3.72 nmol of proline, producing a millimolar concentration near the seed surface which can be detected by the chemosensory system of S. meliloti. Complementation analysis of the mcpU deletion strain verified McpU as the key proline sensor. A structure-based homology search identified tandem Cache (calcium channels and chemotaxis receptors) domains in the periplasmic region of McpU. Conserved residues Asp-155 and Asp-182 of the N-terminal Cache domain were determined to be important for proline sensing by evaluating mutant strains in capillary and swim plate assays. Differential scanning fluorimetry revealed interaction of the isolated periplasmic region of McpU (McpU40-284) with proline and the importance of Asp-182 in this interaction. Using isothermal titration calorimetry, we determined that proline binds with a Kd (dissociation constant) of 104 μM to McpU40-284, while binding was abolished when Asp-182 was substituted by Glu. Our results show that McpU is mediating chemotaxis toward host plants by direct proline sensing. PMID:24657863

  16. Integrin-mediated cell surface recruitment of autotaxin promotes persistent directional cell migration

    PubMed Central

    Wu, Tao; Kooi, Craig Vander; Shah, Pritom; Charnigo, Richard; Huang, Cai; Smyth, Susan S.; Morris, Andrew J.

    2014-01-01

    Autotaxin (ATX) is a secreted lysophospholipase D (lysoPLD) that binds to integrin adhesion receptors. We dissected the roles of integrin binding and lysoPLD activity in stimulation of human breast cancer and mouse aortic vascular smooth muscle cell migration by ATX. We compared effects of wild-type human ATX, catalytically inactive ATX, an integrin binding-defective ATX variant with wild-type lysoPLD activity, the isolated ATX integrin binding N-terminal domain, and a potent ATX selective lysoPLD inhibitor on cell migration using transwell and single-cell tracking assays. Stimulation of transwell migration was reduced (18 or 27% of control, respectively) but not ablated by inactivation of integrin binding or inhibition of lysoPLD activity. The N-terminal domain increased transwell migration (30% of control). ATX lysoPLD activity and integrin binding were necessary for a 3.8-fold increase in the fraction of migrating breast cancer cell step velocities >0.7 μm/min. ATX increased the persistent directionality of single-cell migration 2-fold. This effect was lysoPLD activity independent and recapitulated by the integrin binding N-terminal domain. Integrin binding enables uptake and intracellular sequestration of ATX, which redistributes to the front of migrating cells. ATX binding to integrins and lysoPLD activity therefore cooperate to promote rapid persistent directional cell migration.—Wu, T., Kooi, C. V., Shah, P., Charnigo, R., Huang, C., Smyth, S. S., Morris, A. J. Integrin-mediated cell surface recruitment of autotaxin promotes persistent directional cell migration. PMID:24277575

  17. Pollen loads of eucalypt and other pollen types in birds in NW Spain

    PubMed Central

    Calviño-Cancela, María; Neumann, Max

    2015-01-01

    Here we present the amount of pollen of eucalypt and pollen of other types for birds captured in two bird ringing stations for 14 months (March 2014 to April 2015) in NW Spain. Common and latin names of all birds species captured, together with the number of captured individuals (N), prevalence of eucalypt pollen (percentage of individuals with eucalypt pollen) and of pollen of other types and average pollen loads per individual for eucalypt and other pollen types is presented. See [1] for further information and discussion. PMID:26568978

  18. Pollen loads of eucalypt and other pollen types in birds in NW Spain.

    PubMed

    Calviño-Cancela, María; Neumann, Max

    2015-12-01

    Here we present the amount of pollen of eucalypt and pollen of other types for birds captured in two bird ringing stations for 14 months (March 2014 to April 2015) in NW Spain. Common and latin names of all birds species captured, together with the number of captured individuals (N), prevalence of eucalypt pollen (percentage of individuals with eucalypt pollen) and of pollen of other types and average pollen loads per individual for eucalypt and other pollen types is presented. See [1] for further information and discussion. PMID:26568978

  19. [The epidemiology of pollen allergy].

    PubMed

    Charpin, D; Caillaud, D

    2014-04-01

    The prevalence of seasonal allergic rhinitis can be established through surveys performed in a sample of the general population. These surveys are based on a questionnaire, which could lead to an overestimate of prevalence rates, and on measurements of specific IgE, which need to be interpreted in the light of the responses to the questionnaire. Such surveys are few in France and need to be updated. Risk factors for seasonal allergic rhinitis are genetic, epigenetic and environmental. Relationships between exposure to pollen and health can be documented through ecological and panel surveys. Panel surveys may give information on threshold levels and dose-response relationships. In addition to pollen exposure, global warming and air pollutants act as cofactors. Monitoring of both pollen exposure and its health effects should be encouraged and strengthened. PMID:24750956

  20. Low molecular weight components of pollen alter bronchial epithelial barrier functions

    PubMed Central

    Blume, Cornelia; Swindle, Emily J; Gilles, Stefanie; Traidl-Hoffmann, Claudia; Davies, Donna E

    2015-01-01

    The bronchial epithelium plays a key role in providing a protective barrier against many environmental substances of anthropogenic or natural origin which enter the lungs during breathing. Appropriate responses to these agents are critical for regulation of tissue homeostasis, while inappropriate responses may contribute to disease pathogenesis. Here, we compared epithelial barrier responses to different pollen species, characterized the active pollen components and the signaling pathways leading to epithelial activation. Polarized bronchial cells were exposed to extracts of timothy grass (Phleum pratense), ragweed (Ambrosia artemisifolia), mugwort (Artemisia vulgaris), birch (Betula alba) and pine (Pinus sylvestris) pollens. All pollen species caused a decrease in ionic permeability as monitored trans-epithelial electrical resistance (TER) and induced polarized release of mediators analyzed by ELISA, with grass pollen showing the highest activity. Ultrafiltration showed that the responses were due to components <3kDa. However, lipid mediators, including phytoprostane E1, had no effect on TER, and caused only modest induction of mediator release. Reverse-phase chromatography separated 2 active fractions: the most hydrophilic maximally affected cytokine release whereas the other only affected TER. Inhibitor studies revealed that JNK played a more dominant role in regulation of barrier permeability in response to grass pollen exposure, whereas ERK and p38 controlled cytokine release. Adenosine and the flavonoid isorhamnetin present in grass pollen contributed to the overall effect on airway epithelial barrier responses. In conclusion, bronchial epithelial barrier functions are differentially affected by several low molecular weight components released by pollen. Furthermore, ionic permeability and innate cytokine production are differentially regulated. PMID:26451347

  1. Histological analysis of pollen-pistil interactions in sour passion fruit plants (Passiflora edulis Sims).

    PubMed

    Madureira, Hérika Chagas; Pereira, Telma Nair Santana; Da Cunha, Maura; Klein, Denise Espellet

    2012-08-01

    The success of sexual plant reproduction is directly influenced by specific interactions between the pollen and pistil. Light, fluorescence and scanning electron microscopy techniques were used to evaluate the steps of pollination in sour passion fruit plants (Passiflora edulis Sims). In the compatible interaction, pollen tubes grow through stigma projections towards the ovary. The pollen grain surface was found to be spheroidal and to consist of heteroreticulate exine with six colpi. Furthermore, analysis in vivo of pollen-pistil interactions indicated that stigmas of flowers 24 hours before anthesis are unable to discriminate compatible (genetically unrelated) and incompatible (genetically related) pollen grains. Taken together, these results provide insight into the cellular mechanisms underlying pollination in passion fruit plants. PMID:23185783

  2. Pollen Recovery from Insects: Light Microscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Numerous insect species feed on the pollen, nectar, and other plant exudates that are associated with flowers. As a result of this feeding activity, pollen becomes attached to the insects. Analysis of the pollen attached to these insects can reveal what insects eat, their dispersal patterns in and...

  3. Transport and radiative impacts of atmospheric pollen using online, observation-based emissions

    NASA Astrophysics Data System (ADS)

    Wozniak, M. C.; Steiner, A. L.; Solmon, F.; Li, Y.

    2015-12-01

    Atmospheric pollen emitted from trees and grasses exhibits both a high temporal variability and a highly localized spatial distribution that has been difficult to quantify in the atmosphere. Pollen's radiative impact is also not quantified because it is neglected in climate modeling studies. Here we couple an online, meteorological active pollen emissions model guided by observations of airborne pollen to understand the role of pollen in the atmosphere. We use existing pollen counts from 2003-2008 across the continental U.S. in conjunction with a tree database and historical meteorological data to create an observation-based phenological model that produces accurately scaled and timed emissions. These emissions are emitted and transported within the regional climate model (RegCM4) and the direct radiative effect is calculated. Additionally, we simulate the rupture of coarse pollen grains into finer particles by adding a second size mode for pollen emissions, which contributes to the shortwave radiative forcing and also has an indirect effect on climate.

  4. Using flow cytometry to estimate pollen DNA content: improved methodology and applications

    PubMed Central

    Kron, Paul; Husband, Brian C.

    2012-01-01

    Background and Aims Flow cytometry has been used to measure nuclear DNA content in pollen, mostly to understand pollen development and detect unreduced gametes. Published data have not always met the high-quality standards required for some applications, in part due to difficulties inherent in the extraction of nuclei. Here we describe a simple and relatively novel method for extracting pollen nuclei, involving the bursting of pollen through a nylon mesh, compare it with other methods and demonstrate its broad applicability and utility. Methods The method was tested across 80 species, 64 genera and 33 families, and the data were evaluated using established criteria for estimating genome size and analysing cell cycle. Filter bursting was directly compared with chopping in five species, yields were compared with published values for sonicated samples, and the method was applied by comparing genome size estimates for leaf and pollen nuclei in six species. Key Results Data quality met generally applied standards for estimating genome size in 81 % of species and the higher best practice standards for cell cycle analysis in 51 %. In 41 % of species we met the most stringent criterion of screening 10 000 pollen grains per sample. In direct comparison with two chopping techniques, our method produced better quality histograms with consistently higher nuclei yields, and yields were higher than previously published results for sonication. In three binucleate and three trinucleate species we found that pollen-based genome size estimates differed from leaf tissue estimates by 1·5 % or less when 1C pollen nuclei were used, while estimates from 2C generative nuclei differed from leaf estimates by up to 2·5 %. Conclusions The high success rate, ease of use and wide applicability of the filter bursting method show that this method can facilitate the use of pollen for estimating genome size and dramatically improve unreduced pollen production estimation with flow cytometry. PMID

  5. Examining Ambrosia pollen episodes at Poznań (Poland) using back-trajectory analysis

    NASA Astrophysics Data System (ADS)

    Stach, A.; Smith, M.; Skjøth, C. A.; Brandt, J.

    2007-03-01

    The pollen grains of Ambrosia spp. are considered to be important aeroallergens in parts of southern and central Europe. Back-trajectories have been analysed with the aim of finding the likely sources of Ambrosia pollen grains that arrived at Poznań (Poland). Temporal variations in Ambrosia pollen at Poznań from 1995-2005 were examined in order to identify Ambrosia pollen episodes suitable for further investigation using back-trajectory analysis. The trajectories were calculated using the transport model within the Lagrangian air pollution model, ACDEP (Atmospheric Chemistry and Deposition). Analysis identified two separate populations in Ambrosia pollen episodes, those that peaked in the early morning between 4 a.m. and 8 a.m., and those that peaked in the afternoon between 2 p.m. and 6 p.m.. Six Ambrosia pollen episodes between 2001 and 2005 were examined using back-trajectory analysis. The results showed that Ambrosia pollen episodes that peaked in the early morning usually arrived at Poznań from a southerly direction after passing over southern Poland, the Czech Republic, Slovakia and Hungary, whereas air masses that brought Ambrosia pollen to Poznań during the afternoon arrived from a more easterly direction and predominantly stayed within the borders of Poland. Back-trajectory analysis has shown that there is a possibility that long-range transport brings Ambrosia pollen to Poznań from southern Poland, the Czech Republic, Slovakia and Hungary. There is also a likelihood that Ambrosia is present in Poland, as shown by the arrival of pollen during the afternoon that originated primarily from within the country.

  6. Direct muscarinic and nicotinic receptor-mediated excitation of rat medial vestibular nucleus neurons in vitro

    NASA Technical Reports Server (NTRS)

    Phelan, K. D.; Gallagher, J. P.

    1992-01-01

    We have utilized intracellular recording techniques to investigate the cholinoceptivity of rat medial vestibular nucleus (MVN) neurons in a submerged brain slice preparation. Exogenous application of the mixed cholinergic agonists, acetylcholine (ACh) or carbachol (CCh), produced predominantly membrane depolarization, induction of action potential firing, and decreased input resistance. Application of the selective muscarinic receptor agonist muscarine (MUSC), or the selective nicotinic receptor agonists nicotine (NIC) or 1,1-dimethyl-4-phenylpiperazinium (DMPP) also produced membrane depolarizations. The MUSC-induced depolarization was accompanied by decreased conductance, while an increase in conductance appeared to underlie the NIC- and DMPP-induced depolarizations. The muscarinic and nicotinic receptor mediated depolarizations persisted in tetrodotoxin and/or low Ca2+/high Mg2+ containing media, suggesting direct postsynaptic receptor activation. The MUSC-induced depolarization could be reversibly blocked by the selective muscarinic-receptor antagonist, atropine, while the DMPP-induced depolarization could be reversibly suppressed by the selective ganglionic nicotinic-receptor antagonist, mecamylamine. Some neurons exhibited a transient membrane hyperpolarization during the depolarizing response to CCh or MUSC application. This transient inhibition could be reversibly blocked by the gamma-aminobutyric acid (GABA) antagonist, bicuculline, suggesting that the underlying hyperpolarization results indirectly from the endogenous release of GABA acting at GABA receptors. This study confirms the cholinoceptivity of MVN neurons and establishes that individual MVN cells possess muscarinic as well as nicotinic receptors. The data provide support for a prominent role of cholinergic mechanisms in the direct and indirect regulation of the excitability of MVN neurons.

  7. Neuroticism as a Moderator of Direct and Mediated Relationships Between Introversion-Extraversion and Well-Being

    PubMed Central

    Fadda, Daniela; Scalas, L. Francesca

    2016-01-01

    Among personality traits, extraversion has received major theoretical and empirical attention as predictor of subjective well-being (SWB), whereas the role of emotional stability-neuroticism has been partially neglected. The present study aims to study the role of neuroticism in the relationship between introversion-extraversion and SWB. In particular, we explored if the trait of neuroticism moderates the relationships between introversion-extraversion and SWB dimensions (Satisfaction with life, Mastery, Vigour, Social Cheerfulness), directly and by mediation of self-esteem. Indeed, previous studies have suggested that self-esteem is positively associated with high extraversion and low neuroticism and that it positively mediates the relationship between SWB and personality traits in adolescents. For this purpose, a sample of high school students (N = 1173) completed the Oxford Happiness Inventory, the Rosenberg Self-Esteem Scale and the Big Five Questionnaire. In a latent variable model, we examined the interaction effects (direct and indirect) of extraversion and neuroticism on SWB dimensions. Our results showed that the nature of differences between introverts and extraverts on SWB could be related to the level of neuroticism in relation to Satisfaction with life. Moreover, self-esteem mediated the relationship between personality traits and SWB. In particular, mediated moderation effect analysis showed that self-esteem mediates completely the relationship between the interaction term (extraversion x neuroticism) and Mastery, and partially the relationship with Satisfaction with life. Moreover, moderated mediation effect analysis showed that high levels of neuroticism moderate the effect of extraversion on Satisfaction with life and Mastery through the mediation of self-esteem. In conclusion, our results suggest that although extraversion has a cardinal role on SWB dimensions related to Vigour and Social Cheerfulness, neuroticism and the mediating role of self

  8. Neuroticism as a Moderator of Direct and Mediated Relationships Between Introversion-Extraversion and Well-Being.

    PubMed

    Fadda, Daniela; Scalas, L Francesca

    2016-02-01

    Among personality traits, extraversion has received major theoretical and empirical attention as predictor of subjective well-being (SWB), whereas the role of emotional stability-neuroticism has been partially neglected. The present study aims to study the role of neuroticism in the relationship between introversion-extraversion and SWB. In particular, we explored if the trait of neuroticism moderates the relationships between introversion-extraversion and SWB dimensions (Satisfaction with life, Mastery, Vigour, Social Cheerfulness), directly and by mediation of self-esteem. Indeed, previous studies have suggested that self-esteem is positively associated with high extraversion and low neuroticism and that it positively mediates the relationship between SWB and personality traits in adolescents. For this purpose, a sample of high school students (N = 1173) completed the Oxford Happiness Inventory, the Rosenberg Self-Esteem Scale and the Big Five Questionnaire. In a latent variable model, we examined the interaction effects (direct and indirect) of extraversion and neuroticism on SWB dimensions. Our results showed that the nature of differences between introverts and extraverts on SWB could be related to the level of neuroticism in relation to Satisfaction with life. Moreover, self-esteem mediated the relationship between personality traits and SWB. In particular, mediated moderation effect analysis showed that self-esteem mediates completely the relationship between the interaction term (extraversion x neuroticism) and Mastery, and partially the relationship with Satisfaction with life. Moreover, moderated mediation effect analysis showed that high levels of neuroticism moderate the effect of extraversion on Satisfaction with life and Mastery through the mediation of self-esteem. In conclusion, our results suggest that although extraversion has a cardinal role on SWB dimensions related to Vigour and Social Cheerfulness, neuroticism and the mediating role of self

  9. Direct measurement of the tryptophan-mediated photocleavage kinetics of a protein disulfide bond.

    PubMed

    Abaskharon, Rachel M; Gai, Feng

    2016-04-14

    Disulfide cleavage is one of the major causes underlying ultraviolet (UV) light-induced protein damage. While previous studies have provided strong evidence to support the notion that this process is mediated by photo-induced electron transfer from the excited state of an aromatic residue (e.g., tryptophan) to the disulfide bond, many mechanistic details are still lacking. For example, we do not know how quickly this process occurs in a protein environment. Herein, we design an experiment, which uses the unfolding kinetics of a protein as an observable, to directly assess the kinetics and mechanism of photo-induced disulfide cleavage. Our results show that this disulfide bond cleavage event takes place in ∼2 μs via a mechanism involving electron transfer from the triplet state of a tryptophan (Trp) residue to the disulfide bond. Furthermore, we find that one of the photoproducts of this reaction, a Trp-SR adduct, is formed locally, thus preventing the protein from re-cross-linking. Taken together, these findings suggest that a Trp-disulfide pair could be used as a photo-trigger to initiate protein folding dynamics and control the biological activities of disulfide-containing peptides. PMID:26997094

  10. Caspase-2 resides in the mitochondria and mediates apoptosis directly from the mitochondrial compartment

    PubMed Central

    Lopez-Cruzan, M; Sharma, R; Tiwari, M; Karbach, S; Holstein, D; Martin, C R; Lechleiter, J D; Herman, B

    2016-01-01

    Caspase-2 plays an important role in apoptosis induced by several stimuli, including oxidative stress. However, the subcellular localization of caspase-2, particularly its presence in the mitochondria, is unclear. It is also not known if cytosolic caspase-2 translocates to the mitochondria to trigger the intrinsic pathway of apoptosis or if caspase-2 is constitutively present in the mitochondria that then selectively mediates this apoptotic effect. Here, we demonstrate the presence of caspase-2 in purified mitochondrial fractions from in vitro-cultured cells and in liver hepatocytes using immunoblots and confocal microscopy. We show that mitochondrial caspase-2 is functionally active by performing fluorescence resonance energy transfer analyses using a mitochondrially targeted substrate flanked by donor and acceptor fluorophores. Cell-free apoptotic assays involving recombination of nuclear, cytosolic and mitochondrial fractions from the livers of wild type and Casp2−/− mice clearly point to a direct functional role for mitochondrial caspase-2 in apoptosis. Furthermore, cytochrome c release from Casp2−/− cells is decreased as compared with controls upon treatment with agents inducing mitochondrial dysfunction. Finally, we show that Casp2−/− primary skin fibroblasts are protected from oxidants that target the mitochondrial electron transport chain. Taken together, our results demonstrate that caspase-2 exists in the mitochondria and that it is essential for mitochondrial oxidative stress-induced apoptosis. PMID:27019748