scholarly journals Interviral Recombination between Plant, Insect, and Fungal RNA Viruses: Role of the Intracellular Ca2+/Mn2+ Pump

2019 ◽  
Vol 94 (1) ◽  
Author(s):  
Nikolay Kovalev ◽  
Judit Pogany ◽  
Peter D. Nagy
Keyword(s):  
Driving Forces ◽  
Rna Viruses ◽  
Genetic Recombination ◽  
Hot Spot ◽  
Plant Viruses ◽  
Template Switching ◽  
Rna Recombination ◽  
Content Type ◽  
Intracellular Ca

ABSTRACT Recombination is one of the driving forces of viral evolution. RNA recombination events among similar RNA viruses are frequent, although RNA recombination could also take place among unrelated viruses. In this paper, we have established efficient interviral recombination systems based on yeast and plants. We show that diverse RNA viruses, including the plant viruses tomato bushy stunt virus, carnation Italian ringspot virus, and turnip crinkle virus-associated RNA; the insect plus-strand RNA [(+)RNA] viruses Flock House virus and Nodamura virus; and the double-stranded L-A virus of yeast, are involved in interviral recombination events. Most interviral recombinants are minus-strand recombinant RNAs, and the junction sites are not randomly distributed, but there are certain hot spot regions. Formation of interviral recombinants in yeast and plants is accelerated by depletion of the cellular SERCA-like Pmr1 ATPase-driven Ca2+/Mn2+ pump, regulating intracellular Ca2+ and Mn2+ influx into the Golgi apparatus from the cytosol. The interviral recombinants are generated by a template-switching mechanism during RNA replication by the viral replicase. Replication studies revealed that a group of interviral recombinants is replication competent in cell-free extracts, in yeast, and in the plant Nicotiana benthamiana. We propose that there are major differences among the viral replicases to generate and maintain interviral recombinants. Altogether, the obtained data promote the model that host factors greatly contribute to the formation of recombinants among related and unrelated viruses. This is the first time that a host factor’s role in affecting interviral recombination is established. IMPORTANCE Viruses with RNA genomes are abundant, and their genomic sequences show astonishing variation. Genetic recombination in RNA viruses is a major force behind their rapid evolution, enhanced pathogenesis, and adaptation to their hosts. We utilized a previously identified intracellular Ca2+/Mn2+ pump-deficient yeast to search for interviral recombinants. Noninfectious viral replication systems were used to avoid generating unwanted infectious interviral recombinants. Altogether, interviral RNA recombinants were observed between plant and insect viruses, and between a fungal double-stranded RNA (dsRNA) virus and an insect virus, in the yeast host. In addition, interviral recombinants between two plant virus replicon RNAs were identified in N. benthamiana plants, in which the intracellular Ca2+/Mn2+ pump was depleted. These findings underline the crucial role of the host in promoting RNA recombination among unrelated viruses.

scholarly journals Extending the Definition of the GyrB Quinolone Resistance-Determining Region in Mycobacterium tuberculosis DNA Gyrase for Assessing Fluoroquinolone Resistance in M. tuberculosis

2012 ◽  
Vol 56 (4) ◽  
pp. 1990-1996 ◽  
Author(s):  
Alix Pantel ◽  
Stéphanie Petrella ◽  
Nicolas Veziris ◽  
Florence Brossier ◽  
Sylvaine Bastian ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Hot Spot ◽  
Dna Gyrase ◽  
Quinolone Resistance ◽  
Fluoroquinolone Resistance ◽  
Wild Type ◽  
Content Type ◽  
Highly Active ◽  
Definition Of

ABSTRACTFluoroquinolone (FQ) resistance is emerging inMycobacterium tuberculosis. The main mechanism of FQ resistance is amino acid substitution within the quinolone resistance-determining region (QRDR) of the GyrA subunit of DNA gyrase, the sole FQ target inM. tuberculosis. However, substitutions in GyrB whose implication in FQ resistance is unknown are increasingly being reported. The present study clarified the role of four GyrB substitutions identified inM. tuberculosisclinical strains, two located in the QRDR (D500A and N538T) and two outside the QRDR (T539P and E540V), in FQ resistance. We measured FQ MICs and also DNA gyrase inhibition by FQs in order to unequivocally clarify the role of these mutations in FQ resistance. Wild-type GyrA, wild-type GyrB, and mutant GyrB subunits produced from engineeredgyrBalleles by mutagenesis were overexpressed inEscherichia coli, purified to homogeneity, and used to reconstitute highly active gyrase complexes. MICs and DNA gyrase inhibition were determined for moxifloxacin, gatifloxacin, ofloxacin, levofloxacin, and enoxacin. All these substitutions are clearly implicated in FQ resistance, underlining the presence of a hot spot region housing most of the GyrB substitutions implicated in FQ resistance (residues NTE, 538 to 540). These findings help us to refine the definition of GyrB QRDR, which is extended to positions 500 to 540.

Conceptualizing and contextualizing overtourism: the dynamics of accelerating urban tourism

2020 ◽  
Vol 6 (4) ◽  
pp. 657-671 ◽  
Author(s):  
Jan Henrik Nilsson
Keyword(s):  
Scientific Literature ◽  
Driving Forces ◽  
Urban Tourism ◽  
Structural Development ◽  
Evolutionary Perspective ◽  
Holistic View ◽  
Content Type ◽  
Inner Cities ◽  
Starting Point

Purpose From the background of the dramatic increase of urban tourism, framed by the concept of overtourism, the purpose of this paper is to analyze and discuss current dynamic processes of urban tourism growth, as presented in the scientific literature. With the help of a literature review, this paper aims to discuss current definitions and conceptualizations of overtourism and discuss the driving forces for the growth of urban tourism, thereby situating overtourism in relational to general structural change. Design/methodology/approach This paper builds on a non-exhaustive review of the scientific literature about overtourism and related topics, supplemented by a review of a few central policy documents. Findings Conceptually, overtourism relates to two different, but related, perspectives. The first one concern (negative) experiences of resident population and visitors, whereas the second relates to thresholds for the carrying capacity of destinations. Most of the reviewed literature focuses on three aspects of overtourism: localized problems in inner cities, the supply of unregulated accommodation through Airbnb and Airbnbs as a driving force of gentrification. Important perspectives are missing from the literature, mainly related to the development of driving forces of urban tourism growth in time and space. This observation is the starting point for a discussion on driving forces in an evolutionary perspective with the ambition of relating the growth of urban tourism to long waves of structural development. Research limitations/implications The paper focuses on overtourism in urban contexts, rural tourism is not discussed. Practical implications In identifying the importance of driving forces for understanding the dynamics of urban tourism growth, a holistic view on managing mitigation might be possible. Originality/value The paper adds an evolutionary perspective to the discussion about overtourism and its causes. Thereby, it answers to a need to take tourism seriously in social science, as a major economic, social and ecologic force. In emphasizing the relationship between driving forces on different geographic scales and levels, power relations are highlighted. The paper discusses the role of driving forces for mitigating overtourism. An understanding of the dynamics of driving forces is essential for the development of urban sustainable tourism.

scholarly journals Conserved Regulators of Mating Are Essential for Aspergillus fumigatus Cleistothecium Formation

2010 ◽  
Vol 9 (5) ◽  
pp. 774-783 ◽  
Author(s):  
Edyta Szewczyk ◽  
Sven Krappmann
Keyword(s):  
Aspergillus Fumigatus ◽  
Genetic Recombination ◽  
Content Type ◽  
Hyphal Fusion ◽  
Expression Of Genes ◽  
Body Development ◽  
Fruiting Body Development ◽  
Genes Encoding ◽  
Long Time

ABSTRACT Sexual reproduction of the human pathogen Aspergillus fumigatus (teleomorph: Neosartorya fumigata) was assumed to be absent or cryptic until recently, when fertile crosses among geographically restricted environmental isolates were described. Here, we provide evidence for mating, fruiting body development, and ascosporogenesis accompanied by genetic recombination between unrelated, clinical isolates of A. fumigatus, and this evidence demonstrates the generality and reproducibility of this long-time-undisclosed phase in the life cycle of this heterothallic fungus. Successful mating requires the presence of both mating-type idiomorphs MAT1-1 and MAT1-2, as does expression of genes encoding factors presumably involved in this process. Moreover, analysis of an A. fumigatus mutant deleted for the nsdD gene suggests a role of this conserved regulator of cleistothecium development in hyphal fusion and hence heterokaryon formation.

scholarly journals Targeting Toxoplasma Tubules: Tubulin, Microtubules, and Associated Proteins in a Human Pathogen

2014 ◽  
Vol 14 (1) ◽  
pp. 2-12 ◽  
Author(s):  
Naomi Morrissette
Keyword(s):  
Opportunistic Infections ◽  
Genetic Recombination ◽  
Flagellar Apparatus ◽  
Content Type ◽  
Obligate Intracellular ◽  
Spiral Trajectory ◽  
Parasite Survival ◽  
Associated Proteins ◽  
Flagellar Axoneme

ABSTRACTToxoplasma gondiiis an obligate intracellular parasite that causes serious opportunistic infections, birth defects, and blindness in humans. Microtubules are critically important components of diverse structures that are used throughout theToxoplasmalife cycle. As in other eukaryotes, spindle microtubules are required for chromosome segregation during replication. Additionally, a set of membrane-associated microtubules is essential for the elongated shape of invasive “zoites,” and motility follows a spiral trajectory that reflects the path of these microtubules.Toxoplasmazoites also construct an intricate, tubulin-based apical structure, termed the conoid, which is important for host cell invasion and associates with proteins typically found in the flagellar apparatus. Last, microgametes specifically construct a microtubule-containing flagellar axoneme in order to fertilize macrogametes, permitting genetic recombination. The specialized roles of these microtubule populations are mediated by distinct sets of associated proteins. This review summarizes our current understanding of the role of tubulin, microtubule populations, and associated proteins inToxoplasma; these components are used for both novel and broadly conserved processes that are essential for parasite survival.

scholarly journals Genetic recombination of poliovirus facilitates subversion of host barriers to infection

2018 ◽  
Author(s):  
Ashley Acevedo ◽  
Andrew Woodman ◽  
Jamie J. Arnold ◽  
Ming Te Yeh ◽  
David Evans ◽  
...  
Keyword(s):  
Virus Replication ◽  
Genetic Recombination ◽  
Rna Virus ◽  
Small Population ◽  
Viral Fitness ◽  
Primary Role ◽  
Rna Recombination ◽  
Viral Mutant ◽  
The Impact

AbstractThe contribution of RNA recombination to viral fitness and pathogenesis is poorly defined. Here, we isolate a recombination-deficient, poliovirus variant and find that, while recombination is detrimental to virus replication in tissue culture, recombination is important for pathogenesis in infected animals. Notably, recombination-defective virus exhibits severe attenuation following intravenous inoculation that is associated with a significant reduction in population size during intra-host spread. Because the impact of high mutational loads manifests most strongly at small population sizes, our data suggest that the repair of mutagenized genomes is an essential function of recombination and that this function may drive the long-term maintenance of recombination in viral species despite its associated fitness costs.Significance StatementRNA recombination is a widespread but poorly understood feature of RNA virus replication. For poliovirus, recombination is involved in the emergence of neurovirulent circulating vaccine-derived poliovirus, which has hampered global poliovirus eradication efforts. This emergence illustrates the power of recombination to drive major adaptive change; however, it remains unclear if these adaptive events represent the primary role of recombination in virus survival. Here, we identify a viral mutant with a reduced rate of recombination and find that recombination also plays a central role in the spread of virus within animal hosts. These results highlight a novel approach for improving the safety of live attenuated vaccines and further our understanding of the role of recombination in virus pathogenesis and evolution.

scholarly journals RNA recombination in brome mosaic virus, a model plus strand RNA virus.

1998 ◽  
Vol 45 (4) ◽  
pp. 847-868 ◽  
Author(s):  
M Figlerowicz ◽  
J J Bujarski
Keyword(s):  
Mosaic Virus ◽  
Genetic Recombination ◽  
Rna Virus ◽  
Brome Mosaic Virus ◽  
Template Switching ◽  
Rna Recombination ◽  
Signal Sequences ◽  
Experimental Systems ◽  
Replicase Complex ◽  
Molecular Aspects

Studies on the molecular mechanism of genetic recombination in RNA viruses have progressed at the time when experimental systems of efficient recombination crossovers were established. The system of brome mosaic virus (BMV) represents one of the most useful and most advanced tools for investigation of the molecular aspects of the mechanism of RNA-RNA recombination events. By using engineered BMV RNA components, the occurrence of both homologous and nonhomologous crosses were demonstrated among the segments of the BMV RNA genome. Studies show that the two types of crossovers require different RNA signal sequences and that both types depend upon the participation of BMV replicase proteins. Mutations in the two BMV-encoded replicase polypeptides (proteins 1a and 2a) reveal that their different regions participate in homologous and in nonhomologous crossovers. Based on all these data, it is most likely that homologous and nonhomologous recombinant crosses do occur via two different types of template switching events (copy-choice mechanism) where viral replicase complex changes RNA templates during viral RNA replication at distinct signal sequences. In this review we discuss various aspects of the mechanism of RNA recombination in BMV and we emphasize future projections of this research.

scholarly journals Impact of the Novel Prophage ϕSA169 on Persistent Methicillin-Resistant Staphylococcus aureus Endovascular Infection

mSystems ◽  
2020 ◽  
Vol 5 (3) ◽  
Author(s):  
Liang Li ◽  
Genzhu Wang ◽  
Yi Li ◽  
Patrice Francois ◽  
Arnold S. Bayer ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Hot Spot ◽  
Critical Role ◽  
Bacteriophage Therapy ◽  
Methicillin Resistant ◽  
Content Type ◽  
Antimicrobial Resistance Genes

ABSTRACT Persistent methicillin-resistant Staphylococcus aureus (MRSA) endovascular infections are life-threatening syndromes with few therapeutic options. The potential impact of bacteriophages on the persistent outcome has not been well studied. In this study, we investigated the role of a novel prophage (ϕSA169) in MRSA persistence by using a lysogen-free clinically resolving bacteremia (RB) isolate and comparing it to a derivative which was obtained by infecting the RB strain with ϕSA169, which has been lysogenized in a clinical persistent MRSA bacteremia (PB) isolate. Similar to the PB isolate, the ϕSA169-lysogenized RB strain exhibited well-defined in vitro and in vivo phenotypic and genotypic signatures related to the persistent outcome, including earlier activation of global regulators (i.e., sigB, sarA, agr RNAIII, and sae); higher expression of a critical purine biosynthesis gene, purF; and higher growth rates accompanied by lower ATP levels and vancomycin (VAN) susceptibility and stronger δ-hemolysin and biofilm formation versus its isogenic parental RB isolate. Notably, the contribution of ϕSA169 in persistent outcome with VAN treatment was confirmed in an experimental infective endocarditis model. Taken together, these results indicate the critical role of the prophage ϕSA169 in persistent MRSA endovascular infections. Further studies are needed to identify the mechanisms of ϕSA169 in mediating the persistence, as well as establishing the scope of impact, of this prophage in other PB strains. IMPORTANCE Bacteriophages are viruses that invade the bacterial host, disrupt bacterial metabolism, and cause the bacterium to lyse. Because of its remarkable antibacterial activity and unique advantages over antibiotics, for instance, bacteriophage is specific for one species of bacteria and resistance to phage is less common than resistance to antibiotics. Indeed, bacteriophage therapy for treating infections due to multidrug-resistant pathogens in humans has become a research hot spot. However, it is also worth considering that bacteriophages are transferable and could cotransfer host chromosomal genes, e.g., virulence and antimicrobial resistance genes, while lysogenizing and integrating into the bacterial chromosome (prophage), thus playing a role in bacterial evolution and virulence. In the current study, we identified a novel prophage, ϕSA169, from a clinical persistent MRSA bacteremia isolate, and we determined that ϕSA169 mediated well-defined in vitro and in vivo phenotypic and genotypic signatures related to the persistent outcome, which may represent a unique and important persistent mechanism(s).

Financial planning for retirement: the role of income

2019 ◽  
Vol 37 (6) ◽  
pp. 1419-1440
Author(s):  
Milagros Vivel-Búa ◽  
Lucía Rey-Ares ◽  
Rubén Lado-Sestayo ◽  
Sara Fernández-López
Keyword(s):  
Driving Forces ◽  
Pension Plans ◽  
Retirement Savings ◽  
Content Type ◽  
Working Lives ◽  
Future Income ◽  
Wealth Inequalities ◽  
The Individual ◽  
The Impact

PurposeThe purpose of this paper is to study the driving forces of both the decision to participate in individual pension plans and the amount of money allocated to such plans. Moreover, this paper evaluates the potential role that income plays, which has not previously been considered in depth in the financial literature.Design/methodology/approachBased on a sample of the Spanish population over the period 2008–2015, this paper estimates probit and tobit models, using 165,791 observations. The driving forces of private retirement savings comprise demographic, financial and socio-economic characteristics.FindingsThis paper confirms the impact of socio-demographic and economic variables on participation and monetary contributions to pension plans. It also confirms that income plays a non-negligible role. Moreover, empirical evidence reveals that the effect of gender is related to the income stratum to which the individual belongs.Originality/valueRetirement planning plays a key role in retirees’ future income and several countries have emphasised the importance of private individual savings to supplement the minimum provided by public pension schemes. The previous literature has concluded that those who plan their retirement end their working lives with three times the wealth of non-planners. Consequently, analysis of whether people are saving enough for their retirement can contribute to avoiding future wealth inequalities among retirees. Spain is one of the countries with the greatest inequality in income distribution, so this issue is of even greater interest.

scholarly journals Two types of non-homologous RNA recombination in brome mosaic virus.

2005 ◽  
Vol 52 (4) ◽  
pp. 833-844 ◽  
Author(s):  
Magdalena Alejska ◽  
Nelli Malinowska ◽  
Anna Urbanowicz ◽  
Marek Figlerowicz
Keyword(s):  
Mosaic Virus ◽  
Genetic Recombination ◽  
Genetic Material ◽  
Brome Mosaic Virus ◽  
Homologous Sequence ◽  
Template Switching ◽  
Rna Recombination ◽  
Genomic Rnas ◽  
Site Specific ◽  
Rna Interaction

Non-homologous RNA recombination is a process enabling the exchange of genetic material between various (related or unrelated) RNA-based viruses. Despite extensive investigations its molecular mechanism remains unclear. Studies on genetic recombination in brome mosaic virus (BMV) have shown that local hybridization between genomic RNAs induces frequent non-homologous crossovers. A detailed analysis of recombinant structures suggested that local complementary regions might be involved in two types of non-homologous recombination in BMV: site-specific and heteroduplex-mediated. To verify the above hypothesis and better recognize the mechanism of the phenomenon studied we have tested how the putative types of recombination are affected by a specific mutation in the BMV polymerase gene or by changes in RNA structure. The experiments undertaken revealed substantial differences between site-specific and heteroduplex-mediated recombination, indicating that they occur according to different mechanisms. The former can be classified as homology-assisted, and the latter as homology-independent. In addition to local RNA/RNA hybridization, short regions of homology are required for site-specific crossovers to occur. They are most efficiently mediated if one homologous sequence is located at the beginning of and the second just before a double-stranded region. At present it is difficult to state what is the mechanism of heteroduplex-mediated recombination. Earlier it was postulated that strong RNA/RNA interaction enforces template switching by the viral replicase. There are, however, several observations questioning this model and indicating that some other factors, which are still unknown, may influence heteroduplex-mediated crossovers.

Image, brand relationships and customer value

2015 ◽  
Vol 25 (1) ◽  
pp. 51-74 ◽  
Author(s):  
Laszlo Sajtos ◽  
Henning Kreis ◽  
Roderick Brodie
Keyword(s):  
Customer Value ◽  
Driving Forces ◽  
Service Industries ◽  
Content Type ◽  
Classification Schemes ◽  
Employee Trust ◽  
Service Brands ◽  
Advertising Spending ◽  
The Impact

Purpose – While service brands are conceptualised as being both the company’s presented brand and the customer’s relationship experience, most research to date has supported the central role of the latter over the former in creating customer value and developing loyalty. Studies supporting the central role of relationship experience have relied on classification schemes that have been developed around the role of employees. In contrast, the purpose of this paper is to propose and test the effect of two new moderators, namely advertising spending- and labour-intensity (LI), in predicting the impact of company image and employee trust. Design/methodology/approach – Four contexts (banking, internet provider, insurance and hairdressing) were selected based on their advertising spending- and LI, and a multi-group structural equation modelling technique was employed to test for differences between contexts. Findings – Company image and employee trust were found to have a significant impact on customer value and loyalty perceptions, with considerable differences in patterns across the chosen contexts. This study has confirmed that differences in advertising spending intensity can explain discrepancies in the relative influence of customer value and loyalty drivers across multiple service industries. Originality/value – The findings of this study shed new light on the results of previous studies that relied solely on classification schemes and which supported the primary importance of employee-customer interactions for service brands. Ultimately, this research can help managers better understand the driving forces of their business.

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