Dominant Host Research Articles

Almost royal: incomplete suppression of host worker ovarian development by a social parasite wasp

Insect social parasites, like other parasites, may benefit from inhibiting their host from reproducing (complete or partial parasitic castration) because they can then exploit more of the host’s resources for their own reproduction. In particular, social parasites that kill or expel the host queen need to prevent host workers from reproducing; this is a common worker response to the absence of their queen. Indeed, host workers would benefit from detecting the presence of the parasite and investing in direct and indirect fitness. Studying whether and how social parasites control host worker reproduction can provide information about the degree of integration of the parasite in the host colony and help identify factors regulating workers’ reproductive decisions in social insects. We investigated whether the paper wasp social parasite, Polistes sulcifer, suppresses Polistes dominula (host) worker reproduction as efficiently as the dominant host female does in queen-right colonies by comparing worker reproductive efforts in parasitized and non-parasitized (control) colonies. Our results show that 6 weeks after usurpation of their colony by the social parasite, parasitized workers (1) had more developed ovaries than control workers and (2) laid more eggs as soon as the opportunity arose. This reproductive readiness of parasitized workers was not apparent 2 weeks after colony usurpation. This suggests that P. dominula workers have evolved means to react to social parasitism, as occurs in some ants, and that the parasite has only limited control over host reproduction.

Profiling and engineering of microRNAs for enhancing recombinant protein productivity in Chinese hamster ovary cells

Background Chinese hamster ovary (CHO) cells have become dominant host cells in the biopharmaceutical industry due to their capacity for proper protein folding, assembly and posttranslational modifications. However, low specific productivity (qp) places limitations on yields obtained from mammalian host cells. MicroRNAs (miRNAs), a novel class of short, non-coding RNAs which negatively regulate target gene expression at post-transcriptional levels, have emerged as promising targets for engineering of CHO cell factories to enhance recombinant protein production. While engineering of miRNAs for enhanced cell growth and delayed cell death have been reported, miRNA targets which can enhance qp have not been identified to date.

Comparison of epifaunal assemblages betweenCymodocea nodosaandCaulerpa proliferameadows in Gran Canaria (eastern Atlantic)

Epifaunal invertebrates are sensitive to changes in the identity of the dominant host plant, so assessing differences in the structure of epifaunal assemblages is particularly pertinent in areas where seagrasses have been replaced by alternative vegetation (e.g. green seaweeds). In this study, we aimed to compare the diversity, abundance and structure of epifaunal assemblages, particularly amphipods, between meadows dominated by the seagrassCymodocea nodosaand the green rhizophytic algaeCaulerpa proliferaon shallow soft bottoms of Gran Canaria Island, determining whether patterns were temporally consistent between two times. The epifaunal assemblage structure (abundance and composition) consistently differed between both plants, those assemblages associated withC. prolifera-dominated beds being more diverse and abundant relative toC. nodosameadows. Amphipods constituted ~70% of total crustaceans for the overall study, including 37 species belonging to 16 families. The amphipod abundance was ~3 times larger inC. prolifera-dominated beds than inC. nodosameadows. We detected species-specific affinities; for example,Microdeutopus stationis, Dexamine spinosa, Aora spinicornis, Ischyrocerus inexpectatusandApherusa bispinosawere more abundant inC. prolifera-dominated beds; while the caprellidMantacaprella macaronensisdominated inC. nodosameadows. However, some species, such asPseudoprotella phasmaandAmpithoe ramondi,were found in both habitats with varying abundances between times.

An econometric analysis of sub-national Clean Development Mechanism performance in China

The objective of this research is to conduct a quantitative analysis of China’s sub-national Clean Development Mechanism (CDM) performance as a case study of unbalanced CDM performance within a CDM host country. Key results are as follows: First, investment climate is the most decisive factor, which can explain about 48 % (adjusted R-squared) of China’s sub-national CDM performance at significance level 0.1 %. Second, general economic and investment conditions have a collective determination effect, which together explain about 50 % (adjusted R-squared) of sub-nationall CDM performance. Third, when compared with previous research in which the economic and investment conditions explain about 55 % (adjusted R-squared) of unbalanced CDM performance on the international level, it becomes clear that the impact of the economic and investment conditions on China’s sub-national unbalanced CDM performance resembles the unbalanced performance at the international level. Hence, we conclude that the sub-national unbalanced CDM performance in China is similar to that of the international level, and is influenced by similar determining factors. This finding casts doubt on the previous policy suggestion to fix the geographically unbalanced CDM performance simply by national discrimination, such as by revoking CDM eligibility of an entire host country. Consequently, a more tailored approach is advisable to manage that eligibility on the sub-national level. This is a more precise response to geographically unbalanced CDM performance and is less likely to discourage participation of the dominant CDM host countries in international climate mitigation.

Imaginary ‘Homeland’ and Constitution of a Collective Identity in Diasporic Experiences: An Analysis of The Hundred Secret Senses by Amy Tan

In most contemporary memory narratives that deal with diasporic experiences, the concept of ‘home’ becomes a semiotic site, in which the fluctuating images of past are in a perpetual conflict to make sense. Absence of home generates a rich ground of creativity for migratory subjects to construct an imaginary homeland, based on their present contingent socio- cultural paradigms. Formulation of fluxing, disintegrated sets of imagery of native land would transcend the national geographical boundaries; thus, a new communal identity is constructed amongst migrant communities, which is fashioned by a universal, humane sense of belonging; generally, it is a diasporic individuality that is liberated from absolute national prejudices. In diasporic portrayal of remote homeland, unlike the exilic mystified or stigmatized presentation of precedent, ‘home’ is constructed by creative innovatory, progressive interaction of past, present and future to gratify the social and individual demands. Usually, diasporic picture of home is exposed to a conscious strategy of oblivion; whereas, in the case of exilic subjects, there is a rigidified image of homeland. This would intensify the proliferation of falsified, invented picturing of home, in migration genre. These pictures are the product of a confused sense of moral commitment to preserve national heritage and a desire to be part of the dominant host culture. The present essay seeks to explore the heterogeneous procedure of constitution of collective identity in Amy Tan’s The Hundred Secret Senses, based on the artistic representation of homeland. This fabricated pristine, identity defies the national borders and enjoys a certain amount of autonomy from established definitions of homeland, which are geographical- bound. DOI: 10.5901/mjss.2013.v4n14p385

Microbial community structure of soils under four productivity classes of aspen forests in northern British Columbia

Trembling aspen (Populus tremuloides) is widely distributed in North American forests. Increased stand productivity with resource availability has been reported, but the relationship between soil microbial community structure and stand productivity remains unclear. To examine soil microbial composition of 4 aspen stand productivity classes, we assessed soil properties, microbial biomass and respiration, and bacterial and ectomycorrhizal diversity. Most variables showed no significant differences between productivity classes. However, mean values for basal respiration (0.05 to 27.99 μg CO2-C·g−1 soil·h−1), bacterial biomass, and metabolic quotient (0.08 to 5.22 CO2-C·mg−1 Cmic·h−1) were lowest in low productivity (Class 1) sites. Bacteria to fungi ratios were significantly lower (P = 0.05) in Class 1 compared to other classes. Microbial biomass ranged from 1.39 to 8.11 mg Cmic·g−1 soil. Thirty-seven distinct aspen ectomycorrhizas (ECM) were characterized, 21 were considered rare (from ≤3 trees). ECM richness did not differ significantly between classes, although relative abundance for some types did. Canonical correspondence analysis showed productivity class explained most microbial community variation, e.g., ECM fungi (80% explained) and soil bacteria (46%). Despite some differences, we could not identify statistically significant bacterial or ECM assemblages linked to stand productivity. Results may reflect a strong association between microbial processes and the dominant host, aspen. Aspen associated with widely distributed fungi common to all classes, possibly facilitating its survival and growth, including on sites exhibiting low pH and low soil fertility.

Provenance and tectonic setting of the metapelites deposits in the Bulfat Complex, NE-Iraq

Major and trace elements including rare earth elements (REEs) chemistry of the metapelitic rocks of Bulfat Complex (Iraqi Zagros Suture Zone) indicate their enrichment in large-ion Lithophile, light rare earth (LREE) elements, and relative depletion of high field strength and heavy rare earth (HREE) elements. The linear correlation coefficients between TiO2, K2O, and Al2O3 and total REE reveal that phyllosilicates (e.g., mica) and accessory minerals mainly Ti-bearing phases (e.g., ilmenite) are likely the dominant hosts for REEs. Chondrite-normalized REE patterns typical of continental margin settings with significant enrichment of LREE, prominent negative Eu anomalies, and nearly flat HREE are positively correlated with post-Archean Australian shale (PAAS) and upper continental crust (UCC) patterns. Additionally, their consistent elemental La/Sc, Th/Sc, La/Co, Th/Co, Cr/Th, and Eu/Eu* values suggest that sediments may have been originally derived from an old post-Archean upper continental crust composed chiefly of granitic component. It seems most likely that the felsic source rocks were originated by a process of intra-crustal differentiation such as partial melting and/or fractional crystallization involving fractionation of Ca-plagioclase. The geochemical evidences particularly REEs evaluation show that deposition of clasts occurred in an active continental margin setting during lower–upper Cretaceous period contemporaneous with the igneous activities. It is evident therefore that the clasts source is from the north–northeast side, i.e., from the active margin of Iranian microcontinent (Sanandaj–Sirjan Zone).

Apparent competition leaves no detectable imprint on patterns of community composition: observations from a natural experiment

Indirect interactions mediated by natural enemies shared among herbivorous insects have recently attracted much interest. While many studies have predicted a high potential for apparent competition, only a few have rigorously tested predictions derived from the food web structure in terms of realised population and community dynamics. In this study, a quantified food web was used to identify pairs of herbivore species potentially tied by strong parasitoid‐mediated interactions. The host populations and their parasitism rates over two consecutive years were then followed, during which time the abundance of one dominant host crashed. Following this natural experiment, imprints of asymmetrical, long‐term apparent competition among hosts were sought in population growth rates. The population growth revealed no signs of apparent competition as mediated by parasitoids: the abundance and parasitism rates of less abundant herbivores were uncorrelated with the relative growth rate of four dominant herbivore species with which they shared a major part of their parasitoids. Likewise, the population crash of the dominant herbivore, Cynips longiventris, did not detectably affect the abundances or parasitism rates of other herbivores with which it shared a major fraction of its parasitoids. Overall, this case study fails to add evidence to previous suggestions that apparent competition may constitute a major force in structuring natural communities. However, it suggests that dynamics should not be inferred from static food web structure alone, but rather that predictions based on structure should be verified by empirical observations of realised population dynamics.

Genetics of tan spot resistance in wheat

Tan spot is a devastating foliar disease of wheat caused by the necrotrophic fungal pathogen Pyrenophora tritici-repentis. Much has been learned during the past two decades about the genetics of wheat-P. tritici-repentis interactions. Research has shown that the fungus produces at least three host-selective toxins (HSTs), known as Ptr ToxA, Ptr ToxB, and Ptr ToxC, that interact directly or indirectly with the products of the dominant host genes Tsn1, Tsc2, and Tsc1, respectively. The recent cloning and characterization of Tsn1 provided strong evidence that the pathogen utilizes HSTs to subvert host resistance mechanisms to cause disease. However, in addition to host-HST interactions, broad-spectrum, race non-specific resistance QTLs and recessively inherited qualitative 'resistance' genes have been identified. Molecular markers suitable for marker-assisted selection against HST sensitivity genes and for race non-specific resistance QTLs have been developed and used to generate adapted germplasm with good levels of tan spot resistance. Future research is needed to identify novel HSTs and corresponding host sensitivity genes, determine if the recessively inherited resistance genes are HST insensitivities, extend the current race classification system to account for new HSTs, and determine the molecular basis of race non-specific resistance QTLs and their relationships with host-HST interactions at the molecular level. Necrotrophic pathogens such as P. tritici-repentis are likely to become increasingly significant under a changing global climate making it imperative to further characterize the wheat-P. tritici-repentis pathosystem and develop tan spot resistant wheat varieties.

MagnesiumK-edge XANES spectroscopy of geological standards

Magnesium K-edge X-ray absorption near-edge structure (XANES) spectra have been investigated to develop a systematic understanding of a suite of Mg-bearing geological materials such as silicate and carbonate minerals, sediments, rocks and chemical reagents. For the model compounds the Mg XANES was found to vary widely between compounds and to provide a fingerprint for the form of Mg involved in geologic materials. The energy positions and resonance features obtained from these spectra can be used to specify the dominant molecular host site of Mg, thus shedding light on Mg partitioning and isotope fractionation in geologic materials and providing a valuable complement to existing knowledge of Mg geochemistry.

Investigation on distribution of Yersinia enterocolitica in Henan province between 2005 and 2011

To investigate the distribution of Yersinia enterocolitica in Henan province from 2005 to 2011. A total of 6700 samples of stool specimen were collected from diarrhea patients and different domestic animals between 2005 and 2011 from Zhengzhou, Suixian and Dengfeng, as well as flies and the daub specimens of raw and cooked meat products. The bacteria were isolated by cold enrichment method, analyzed by the systematic biochemistry to determine the serotypes and bio-types, and tested the virulence genes by PCR method. A total of 216 strains of Yersinia enterocolitica were isolated from 11 kinds of animal hosts and foods, while 29.63% (64/216) of them were from swine. The dominant epidemic serotypes of the Yersinia enterocolitica were O: 5 and O: 8, accounted for 23.2% (50/216) and 20.4% (44/216), respectively; type 1A was the dominant bio-type, accounted for 84.7% (183/216). The dominant serotype and bio-type differed a lot among various hosts.16 pathogenic strains were isolated from swine, followed by diarrhea patients (6 strains) and dogs (6 strains). The distribution of the host of Yersinia enterocolitica was widespread, while swine was the dominant animal host.

Stress: A Possible Link between Genetics, Epigenetics, and Childhood Asthma

Stress: A Possible Link between Genetics, Epigenetics, and Childhood Asthma

Modulating Membrane Composition Alters Free Fatty Acid Tolerance in Escherichia coli

Microbial synthesis of free fatty acids (FFA) is a promising strategy for converting renewable sugars to advanced biofuels and oleochemicals. Unfortunately, FFA production negatively impacts membrane integrity and cell viability in Escherichia coli, the dominant host in which FFA production has been studied. These negative effects provide a selective pressure against FFA production that could lead to genetic instability at industrial scale. In prior work, an engineered E. coli strain harboring an expression plasmid for the Umbellularia californica acyl-acyl carrier protein (ACP) thioesterase was shown to have highly elevated levels of unsaturated fatty acids in the cell membrane. The change in membrane content was hypothesized to be one underlying cause of the negative physiological effects associated with FFA production. In this work, a connection between the regulator of unsaturated fatty acid biosynthesis in E. coli, FabR, thioesterase expression, and unsaturated membrane content was established. A strategy for restoring normal membrane saturation levels and increasing tolerance towards endogenous production of FFAs was implemented by modulating acyl-ACP pools with a second thioesterase (from Geobacillus sp. Y412MC10) that primarily targets medium chain length, unsaturated acyl-ACPs. The strategy succeeded in restoring membrane content and improving viability in FFA producing E. coli while maintaining FFA titers. However, the restored fitness did not increase FFA productivity, indicating the existence of additional metabolic or regulatory barriers.

Foreign Company Attractiveness to Host Country National Professionals: An Integrated Model

While attracting talent is important for company success, very little research is conducted on foreign company attractiveness to host country national (HCN) professionals. To bridge this research gap, this paper investigates foreign company attractiveness from a HCN perspective. Building on Person-Organization-Fit (P-O fit) theory, we develop an integrated model taking into account relevant organizational and individual characteristics in the foreign company context. The model tested with 800 HCN professionals in Japan show that company country-of-origin does not influence organizational attractiveness. Instead, HCN professionals prefer companies with human resource management practices, work environment, and organizational culture that are congruent with dominant host country practices. Further, the results show that HCN demographics (age and gender), international skills (English proficiency and international experiences) and individual work values (individualism and risk aversion) interact with these organizational characteristics.

Spatial stratification of various Lyme disease spirochetes in a Central European site

To determine whether the genospecies composition of Lyme disease spirochetes is spatially stratified, we collected questing Ixodes ricinus ticks in neighboring plots where rodents, birds, and lizards were present as reservoir host and compared the prevalence of various genospecies. The overall prevalence of spirochetes in questing ticks varied across the study site. Borrelia lusitaniae appeared to infect adult ticks in one plot at the same frequency as did Borrelia afzelii in the other plots. The relative density of questing nymphal and adult ticks varied profoundly. Where lizards were exceedingly abundant, these vertebrates seemed to constitute the dominant host for nymphal ticks, contributing the majority of infected adult ticks. Because lizards support solely B.lusitaniae and appear to exclude other genospecies, their narrow genospecies association results in predominance of B.lusitaniae in sites where lizards are abundant, while limiting its spread to the host's habitat range. To the extent that Central European B.lusitaniae strains are nonpathogenic, the presence of numerous lizards should locally decrease risk of infection for people. Evaluation of regional risk of infection by Lyme disease spirochetes should take the spatial effect of hosts into consideration, which stratify the distribution of specifically infected ticks on a small scale.

Early Season Host Plants of <I>Apolygus lucorum</I> (Heteroptera: Miridae) in Northern China

Apolygus lucorum (Meyer-Dür) (Heteroptera: Miridae) has become a severe pest of cotton and many other crops in northern China as a result of the widespread adoption of Bacillus thuringiensis (Berliner) cotton, with a corresponding reduction of broad-spectrum insecticide application in cotton fields. From the middle of April to middle June, A. lucorum feeds and develops on other host plants before dispersing to cotton fields. Effective suppression of A. lucorum populations before they enter cotton fields may be an excellent strategy for reducing the occurrence and damage of their subsequent generations in cotton fields. For that, basic information about the host plant range of A. lucorum during the early season is needed. Between 2006 and 2010, a total of 94 plant species from 41 families covering 39,956 square meters of land in natural conditions were sampled using the standard white pan beat method. Sixty-six plant species, including 45 weeds, 10 fruit trees, 5 timber trees, 4 pasture crops, and 2 arable crops were found to be hosts of A. lucorum. Among these species, Descurainia sophia (L.) Webb ex Prantl, Humulus scandens (Loureiro) Merrill, Zizyphus jujuba Miller, Vitis vinifera L., Viciafaba L., and Medicago sativa L. were identified as dominant host species because of their wide distribution and high population densities of A. lucorum. The results of this study provide useful information about the early season host range of A. lucorum, which can be used to develop effective strategies to control the pest before its dispersal to cotton fields.

An emergent disease causes directional changes in forest species composition in coastal California

Non‐native forest pathogens can cause dramatic and long‐lasting changes to the composition of forests, and these changes may have cascading impacts on community interactions and ecosystem functioning. Phytophthora ramorum, the causal agent of the emergent forest disease sudden oak death (SOD), has a wide host range, but mortality is concentrated in a few dominant tree species of coastal forests in California and Oregon. We examined interactions between P. ramorum and its hosts in redwood and mixed evergreen forest types over an 80,000 ha area in the Big Sur ecoregion of central California, an area that constitutes the southernmost range of the pathogen and includes forest stands on the advancing front of pathogen invasion. We established a network of 280 long‐term forest monitoring plots to understand how host composition and forest structure facilitated pathogen invasion, and whether selective mortality from SOD has led to shifts in community composition. Infested and uninfested sites differed significantly in host composition due to both historical trends and disease impacts. A reconstruction of pre‐disease forest composition showed that stands that eventually became infested with the pathogen tended to be more mature with larger stems than stands that remained pathogen‐free, supporting the hypothesis of aerial dispersal by the pathogen across the landscape followed by local understory spread. The change in species composition in uninfested areas was minimal over the study period, while infested stands had large changes in composition, correlated with the loss of tanoak (Notholithocarpus densiflorus), signaling the potential for SOD to dramatically change coastal forests through selective removal of a dominant host. Forest diversity plays an important role in pathogen establishment and spread, and is in turn changed by pathogen impacts. Asymmetric competency among host species means that impacts of P. ramorum on forest diversity are shaped by the combination and dominance of hosts present in a stand.

Host tree utilization by epiphytic orchids in different land-use intensities in Kathmandu Valley, Nepal

We studied the influence of site conditions on epiphytic orchids under a subtropical climate in the Kathmandu Valley, Nepal. We analysed 96 systematically distributed grid points situated in Kathmandu Valley across a land-use intensity gradient (national park to urbanised city area). Geographical Information System (GIS) and remote sensing were used for classification of land-use types. We identified 23 species of epiphytic orchids, within 13 genera, from 42 different host tree species. Host preference is obvious for some orchid species (e.g., Dendrobium nobile), with certain tree species (e.g., Schima wallichii, Ficus religiosa) hosting more orchid species than others. The orchid Rhynchostylis retusa was the most common species found on many different host tree species across the land-use intensity gradient. Host species and host bark characteristics (e.g., rugosity, pH and exposure to wind) played a vital role for orchid distribution, with lower abundance in areas of higher impact. Under strong human impact (urban city area), F. religiosa was the dominant host tree, with large individual trees (mean diameter in breast height, dbh = 1.3 m) providing the habitat for considerable populations of R. retusa individuals. In general, epiphytic orchids were found on larger host trees in urban areas than in areas of lower human impact. We found that some hosts are more likely to harbour orchid species, especially native host species. Older larger trees with rougher bark, low pH, exposed to wind and reduced human impact provided better habitats for orchids. We suggest these characteristics should be considered in urban planning to reduce human impact on the associated orchid epiphytic community.

Hantaviruses in rodents and humans, Xi’an, PR China

Xi'an, the capital of Shaanxi province, located in north-west China, is one of the major endemic areas for haemorrhagic fever with renal syndrome (HFRS). In this study, the epidemiological data of HFRS in Xi'an from 1959 to 2010, especially in the past ten years (2001-2010), were surveyed. The features of hantavirus (HV) host carriers, the molecular characteristics of the HV S gene from hosts and patients, and the genome of the viral isolate were also investigated. Data showed that there might be a ten-year cycle of HFRS in Xi'an. Although the main population group infected over the past ten years was still the 16-59-year-old male farmers, the composition of the population and geographical distribution of HFRS cases have changed slowly, accompanied by the development of environmental and socio-economic situations. Apodemus agrarius remains the dominant host of HV. The HV strains from host rodents and patients in Xi'an belonged to the Hantaan virus (HTNV); no Seoul virus strains were found. Phylogenetic analysis of the small segments of strains taken from hosts and patients, and the whole genome of a viral isolate showed that the virus circulating in Xi'an had high similarity to Guizhou strains. The study also indicated that the vaccine candidate strain A16 isolated during the past century in Xi'an might be a recombinant strain of HTNV and the Amur virus, thus it may not be an optimal vaccine strain.

Lethal small bowel necrosis due to aspergillosis during acute promyelocytic leukemia induction

Lethal small bowel necrosis due to aspergillosis during acute promyelocytic leukemia induction