scholarly journals Relationships and Evolution of Double-Stranded RNA Totiviruses of Yeasts Inferred from Analysis of L-A-2 and L-BC Variants in Wine Yeast Strain Populations

2016 ◽  
Vol 83 (4) ◽  
Author(s):  
Nieves Rodríguez-Cousiño ◽  
Rosa Esteban
Keyword(s):  
Wine Yeast ◽  
Helper Virus ◽  
Medium Size ◽  
Coat Proteins ◽  
Double Stranded Rna ◽  
Content Type ◽  
Protein Toxin ◽  
Killer Toxins ◽  
Helper Activity ◽  
A Minor

ABSTRACT Saccharomyces cerevisiae killer strains secrete a protein toxin active on nonkiller strains of the same (or other) yeast species. Different killer toxins, K1, K2, K28, and Klus, have been described. Each toxin is encoded by a medium-size (1.5- to 2.3-kb) M double-stranded RNA (dsRNA) located in the cytoplasm. M dsRNAs require L-A helper virus for maintenance. L-A belongs to the Totiviridae family, and its dsRNA genome of 4.6 kb codes for the major capsid protein Gag and a minor Gag-Pol protein, which form the virions that separately encapsidate L-A or the M satellites. Different L-A variants exist in nature; on average, 24% of their nucleotides are different. Previously, we reported that L-A-lus was specifically associated with Mlus, suggesting coevolution, and proposed a role of the toxin-encoding M dsRNAs in the appearance of new L-A variants. Here we confirm this by analyzing the helper virus in K2 killer wine strains, which we named L-A-2. L-A-2 is required for M2 maintenance, and neither L-A nor L-A-lus shows helper activity for M2 in the same genetic background. This requirement is overcome when coat proteins are provided in large amounts by a vector or in ski mutants. The genome of another totivirus, L-BC, frequently accompanying L-A in the same cells shows a lower degree of variation than does L-A (about 10% of nucleotides are different). Although L-BC has no helper activity for M dsRNAs, distinct L-BC variants are associated with a particular killer strain. The so-called L-BC-lus (in Klus strains) and L-BC-2 (in K2 strains) are analyzed. IMPORTANCE Killer strains of S. cerevisiae secrete protein toxins that kill nonkiller yeasts. The “killer phenomenon” depends on two dsRNA viruses: L-A and M. M encodes the toxin, and L-A, the helper virus, provides the capsids for both viruses. Different killer toxins exist: K1, K2, K28, and Klus, encoded on different M viruses. Our data indicate that each M dsRNA depends on a specific helper virus; these helper viruses have nucleotide sequences that may be as much as 26% different, suggesting coevolution. In wine environments, K2 and Klus strains frequently coexist. We have previously characterized the association of Mlus and L-A-lus. Here we sequence and characterize L-A-2, the helper virus of M2, establishing the helper virus requirements of M2, which had not been completely elucidated. We also report the existence of two specific L-BC totiviruses in Klus and K2 strains with about 10% of their nucleotides different, suggesting different evolutionary histories from those of L-A viruses.

scholarly journals Genome Features of a New Double-Stranded RNA Helper Virus (LBCbarr) from Wine Torulaspora delbrueckii Killer Strains

2021 ◽  
Vol 22 (24) ◽  
pp. 13492
Author(s):  
Manuel Ramírez ◽  
Rocío Velázquez ◽  
Antonio López-Piñeiro ◽  
Alberto Martínez
Keyword(s):  
High Throughput Sequencing ◽  
Polymerase Activity ◽  
Helper Virus ◽  
Amino Acid Sequences ◽  
Dsrna Virus ◽  
Medium Size ◽  
Torulaspora Delbrueckii ◽  
Killer Strain ◽  
Large Size ◽  
Helper Activity

The killer phenotype of Torulaspora delbrueckii (Td) and Saccharomyces cerevisiae (Sc) is encoded in the genome of medium-size dsRNA viruses (V-M). Killer strains also contain a helper large size (4.6 kb) dsRNA virus (V-LA) which is required for maintenance and replication of V-M. Another large-size (4.6 kb) dsRNA virus (V-LBC), without known helper activity to date, may join V-LA and V-M in the same yeast. T. delbrueckii Kbarr1 killer strain contains the killer virus Mbarr1 in addition to two L viruses, TdV-LAbarr1 and TdV-LBCbarr1. In contrast, the T. delbrueckii Kbarr2 killer strain contains two M killer viruses (Mbarr1 and M1) and a LBC virus (TdV-LBCbarr2), which has helper capability to maintain both M viruses. The genomes of TdV-LBCbarr1 and TdV-LBCbarr2 were characterized by high-throughput sequencing (HTS). Both RNA genomes share sequence identity and similar organization with their ScV-LBC counterparts. They contain all conserved motifs required for translation, packaging, and replication of viral RNA. Their Gag-Pol amino-acid sequences also contain the features required for cap-snatching and RNA polymerase activity. However, some of these motifs and features are similar to those of LA viruses, which may explain that at least TdV-LBCbarr2 has a helper ability to maintain M killer viruses. Newly sequenced ScV-LBC genomes contained the same motifs and features previously found in LBC viruses, with the same genome location and secondary structure. Sequence comparison showed that LBC viruses belong to two clusters related to each species of yeast. No evidence for associated co-evolution of specific LBC with specific M virus was found. The presence of the same M1 virus in S. cerevisiae and T. delbrueckii raises the possibility of cross-species transmission of M viruses.

scholarly journals Characterization, Ecological Distribution, and Population Dynamics of Saccharomyces Sensu Stricto Killer Yeasts in the Spontaneous Grape Must Fermentations of Southwestern Spain

2011 ◽  
Vol 78 (3) ◽  
pp. 735-743 ◽  
Author(s):  
Matilde Maqueda ◽  
Emiliano Zamora ◽  
María L. Álvarez ◽  
Manuel Ramírez
Keyword(s):  
Yeast Species ◽  
Sensu Stricto ◽  
Medium Size ◽  
Double Stranded Rna ◽  
Content Type ◽  
Volatile Acidity ◽  
Killer Yeasts ◽  
Spontaneous Fermentations ◽  
Protein Toxins ◽  
Dsrna Viruses

ABSTRACTKiller yeasts secrete protein toxins that are lethal to sensitive strains of the same or related yeast species. Among the four types ofSaccharomyceskiller yeasts already described (K1, K2, K28, and Klus), we found K2 and Klus killer yeasts in spontaneous wine fermentations from southwestern Spain. Both phenotypes were encoded by medium-size double-stranded RNA (dsRNA) viruses,Saccharomyces cerevisiaevirus (ScV)-M2 and ScV-Mlus, whose genome sizes ranged from 1.3 to 1.75 kb and from 2.1 to 2.3 kb, respectively. The K2 yeasts were found in all the wine-producing subareas for all the vintages analyzed, while the Klus yeasts were found in the warmer subareas and mostly in the warmer ripening/harvest seasons. The middle-size isotypes of the M2 dsRNA were the most frequent among K2 yeasts, probably because they encoded the most intense K2 killer phenotype. However, the smallest isotype of the Mlus dsRNA was the most frequent for Klus yeasts, although it encoded the least intense Klus killer phenotype. The killer yeasts were present in most (59.5%) spontaneous fermentations. Most were K2, with Klus being the minority. The proportion of killer yeasts increased during fermentation, while the proportion of sensitive yeasts decreased. The fermentation speed, malic acid, and wine organoleptic quality decreased in those fermentations where the killer yeasts replaced at least 15% of a dominant population of sensitive yeasts, while volatile acidity and lactic acid increased, and the amount of bacteria in the tumultuous and the end fermentation stages also increased in an unusual way.

scholarly journals Site-Directed Mutagenesis of the Heterotrimeric Killer Toxin Zymocin Identifies Residues Required for Early Steps in Toxin Action

2014 ◽  
Vol 80 (20) ◽  
pp. 6549-6559 ◽  
Author(s):  
Sabrina Wemhoff ◽  
Roland Klassen ◽  
Friedhelm Meinhardt
Keyword(s):  
Kluyveromyces Lactis ◽  
Killer Toxin ◽  
Cysteine Residue ◽  
Site Directed Mutagenesis ◽  
Target Cells ◽  
Directed Mutagenesis ◽  
Content Type ◽  
Protein Toxin ◽  
Assisted Delivery

ABSTRACTZymocin is aKluyveromyces lactisprotein toxin composed of αβγ subunits encoded by the cytoplasmic virus-like element k1 and functions by αβ-assisted delivery of the anticodon nuclease (ACNase) γ into target cells. The toxin binds to cells' chitin and exhibits chitinase activityin vitrothat might be important during γ import.Saccharomyces cerevisiaestrains carrying k1-derived hybrid elements deficient in either αβ (k1ORF2) or γ (k1ORF4) were generated. Loss of either gene abrogates toxicity, and unexpectedly, Orf2 secretion depends on Orf4 cosecretion. Functional zymocin assembly can be restored by nuclear expression of k1ORF2 or k1ORF4, providing an opportunity to conduct site-directed mutagenesis of holozymocin. Complementation required active site residues of α's chitinase domain and the sole cysteine residue of β (Cys250). Since βγ are reportedly disulfide linked, the requirement for the conserved γ C231 was probed. Toxicity of intracellularly expressed γ C231A indicated no major defect in ACNase activity, while complementation of k1ΔORF4 by γ C231A was lost, consistent with a role of β C250 and γ C231 in zymocin assembly. To test the capability of αβ to carry alternative cargos, the heterologous ACNase fromPichia acaciae(P. acaciaeOrf2 [PaOrf2]) was expressed, along with its immunity gene, in k1ΔORF4. While efficient secretion of PaOrf2 was detected, suppression of the k1ΔORF4-derived k1Orf2 secretion defect was not observed. Thus, the dependency of k1Orf2 on k1Orf4 cosecretion needs to be overcome prior to studying αβ's capability to deliver other cargo proteins into target cells.

Venous rupture during transvenous approach to a carotid-cavernous fistula

1989 ◽  
Vol 71 (1) ◽  
pp. 133-137 ◽  
Author(s):  
Wesley A. King ◽  
Grant B. Hieshima ◽  
Neil A. Martin
Keyword(s):  
Carotid Artery ◽  
Cavernous Sinus ◽  
Balloon Occlusion ◽  
Alternative Methods ◽  
Ocular Motility ◽  
Carotid Cavernous Fistula ◽  
Content Type ◽  
Cavernous Fistula ◽  
A Minor ◽  
Transvenous Approach

✓ An attempt at transfemoral transarterial balloon occlusion of a high-flow spontaneous carotid-cavernous fistula was unsuccessful because the carotid artery rent was too small for this approach. During a subsequent transvenous approach to the cavernous sinus through the jugular vein, the inferior petrosal sinus was perforated. A minor subarachnoid hemorrhage occurred before the tear could be sealed by the deposition of three Gianturco coils in the vein. The patient was taken to the operating room for emergency obliteration of the fistula and petrosal sinus in order to remove the risk of further hemorrhage. Under the guidance of intraoperative digital subtraction angiography, isobutyl-2-cyanoacrylate was injected directly into the surgically exposed cavernous sinus. Successful obliteration of the fistula was achieved with preservation of the carotid artery, and the angiography catheter was removed safely from the petrosal sinus. Although initially after surgery the patient had nearly complete ophthalmoplegia, at her 1-year follow-up examination she had normal ocular motility and visual acuity. The transvenous approach to the cavernous sinus and alternative methods of treatment of carotid-cavernous fistulas are discussed.

Transformational leadership and employee creativity

2015 ◽  
Vol 53 (5) ◽  
pp. 894-910 ◽  
Author(s):  
Swati Mittal ◽  
Rajib Lochan Dhar
Keyword(s):  
Transformational Leadership ◽  
Knowledge Sharing ◽  
Leadership Style ◽  
High Performance ◽  
Hierarchical Regression ◽  
Medium Size ◽  
Employee Creativity ◽  
Content Type ◽  
Managerial Implications ◽  
Transformational Leadership Style

Purpose – Among the different styles of leadership, transformational leadership has gained most attention from organisational researchers and academics. Although transformational leadership and its work-associated outcomes have been examined in previous literature, only a small number of studies highlighted the role of transformational leadership style in fostering employee creativity, mediated through their creative self-efficacy (CSE) in the context of Indian organisations. The purpose of this paper is to observe the effect of transformational leadership on employee creativity in small and medium sized IT companies, where CSE is proposed as a mediator and knowledge sharing as a moderator through which a transformational leader tends to influence the creativity of the employees. Design/methodology/approach – Data were gathered from 348 manager-employee dyads of small and medium size IT companies operating in India. They replied to questions about their leader’s transformational leadership style, employee CSE, knowledge sharing and creativity. Findings – Findings of the present study, derived from a hierarchical regression analysis, using the data of 348 manager-employee dyads from Indian IT SMEs professionals, revealed that CSE mediates the relation between transformational leadership and employee creativity. In addition, knowledge sharing acts as a moderator for CSE and employee creativity. Research limitations/implications – A sample size is one probable limitation of the study. Another limitation of the study is that factors used for the survey were self-reported by the respondents. Self-reporting may not always produce reliable and accurate response. Practical implications – Based on the results, this study presents strong theoretical and managerial implications that can be used by IT organisations to evaluate the consequence of transformational leadership on employee creativity. Through transformational leadership style, leader can develop CSE and employee creativity to do things in a better way and develop knowledge sharing in employees for high performance. Therefore, the IT industry need to understand that creativity is one of the approaches to attaining and sustaining competitive advantage. In addition, it is important for them to find out more about the relation between transformational leadership, CSE and employee creativity. Originality/value – The study adds to the existing literature by illuminating the process through which transformational leadership has a significant effect on fostering CSE and employee creativity.

Shareholder risk-taking incentives in the presence of contingent capital

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mahmoud Fatouh ◽  
Ayowande A. McCunn
Keyword(s):  
Risk Taking ◽  
Banking System ◽  
Capital Requirements ◽  
Content Type ◽  
Basic Model ◽  
Conversion Rates ◽  
A Minor ◽  
The Impact ◽  
Practical Implications

Purpose This paper aims to present a model of shareholders’ willingness to exert effort to reduce the likelihood of bank distress and the implications of the presence of contingent convertible (CoCo) bonds in the liabilities structure of a bank. Design/methodology/approach This study presents a basic model about the moral hazard surrounding shareholders willingness to exert effort that increases the likelihood of a bank’s success. This study uses a one-shot game and so do not capture the effects of repeated interactions. Findings Consistent with the existing literature, this study shows that the direction of the wealth transfer at the conversion of CoCo bonds determines their impact on shareholder risk-taking incentives. This study also finds that “anytime” CoCos (CoCo bonds trigger-able anytime at the discretion of managers) have a minor advantage over regular CoCo bonds, and that quality of capital requirements can reduce the risk-taking incentives of shareholders. Practical implications This study argues that shareholders can also use manager-specific CoCo bonds to reduce the riskiness of the bank activities. The issuance of such bonds can increase the resilience of individual banks and the whole banking system. Regulators can use restrictions on conversion rates and/or requirements on the quality of capital to address the impact of CoCo bonds issuance on risk-taking incentives. Originality/value To model the risk-taking incentives, authors generally modify the asset processes to introduce components that reflect asymmetric information between CoCo holders and shareholders and/or managers. This paper follows a simpler method similar to that of Holmström and Tirole (1998).

The effect of export tax rebates on product quality: evidence from China's agricultural product processing industry

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Yue Liang ◽  
Jingqi Dang ◽  
Shuai Chen
Keyword(s):  
Quality Improvement ◽  
Product Quality ◽  
Policy Implications ◽  
Medium Size ◽  
Agricultural Product ◽  
Firm Innovation ◽  
Processing Industry ◽  
Content Type ◽  
Export Tax

PurposeThis study aims to establish the linkage among export tax rebate (ETR), firm innovation and product quality of Chinese agricultural product processing industry (APPI), so that more targeted policy implications can be discussed.Design/methodology/approachUsing highly disaggregated firm-product-destination-level data through 2001 to 2013 of Chinese APPI, this study employs a two-way fixed effects specification to establish the linkage between ETR and product quality, while the mediational model is adopted to examine potential mechanisms.FindingsBaseline estimates show that a 1% increase in ETR rate leads to a significant increase in the product quality of APPI by 0.12% on the whole. However, there is a nonlinear, inverse-U shaped relationship between ETR and product quality, and the optimal inflection point occurs when ERT rate equals 0.15. Mechanism analyses show that firm innovation is an important impact channel, which explains 9.8% of quality improvement induced by raising ETR. Further heterogeneous analyses reveal both the total effects of ETR on product quality and the mediation effects of innovation are dominated by young SMEs (small and medium-size enterprises).Practical implicationsAuthorities can promote the innovation and then product quality improvement of young SMEs by moderately increasing ETR rate. To ensure ETR more effective in improving quality, it is necessary for the government to encourage innovation. Authorities can reduce the risk of innovation failure for low-tech firms by increasing R&D subsidies, while ensuring innovation returns for high-tech firms in combination with stronger intellectual property protection.Originality/valueFirst, this is one of the earlier studies to explore the relationship between ETR and product quality specifically for Chinese APPI. Second, we show firm innovation as an important mediator so that policies aim at raising ETR rates are eventually beneficial to product quality. Third, using the highly disaggregated data, we allow ETR rate to vary across different products, which is an improvement in the accuracy of previous literature. Finally, our research provides additional empirical evidence for revealing the micro-mechanism of ETR affecting firm behaviors.

Three different M1 RNA-containing viruslike particle types in Saccharomyces cerevisiae: in vitro M1 double-stranded RNA synthesis

1986 ◽  
Vol 6 (5) ◽  
pp. 1552-1561
Author(s):  
R Esteban ◽  
R B Wickner
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Rna Synthesis ◽  
Major Coat Protein ◽  
Double Stranded Rna ◽  
Dsrna Molecule ◽  
Protein Toxin ◽  
New Type ◽  
Viruslike Particles ◽  
M1 Rna

Killer strains of Saccharomyces cerevisiae bear at least two different double-stranded RNAs (dsRNAs) encapsidated in 39-nm viruslike particles (VLPs) of which the major coat protein is coded by the larger RNA (L-A dsRNA). The smaller dsRNA (M1 or M2) encodes an extracellular protein toxin (K1 or K2 toxin). Based on their densities on CsCl gradients, L-A- and M1-containing particles can be separated. Using this method, we detected a new type of M1 dsRNA-containing VLP (M1-H VLP, for heavy) that has a higher density than those previously reported (M1-L VLP, for light). M1-H and M1-L VLPs are present together in the same strains and in all those we tested. M1-H, M1-L, and L-A VLPs all have the same types of proteins in the same approximate proportions, but whereas L-A VLPs and M1-L VLPs have one dsRNA molecule per particle, M1-H VLPs contain two M1 dsRNA molecules per particle. Their RNA polymerase produces mainly plus single strands that are all extruded in the case of M1-H particles but are partially retained inside the M1-L particles to be used later for dsRNA synthesis. We show that M1-H VLPs are formed in vitro from the M1-L VLPs. We also show that the peak of M1 dsRNA synthesis is in fractions lighter than M1-L VLPs, presumably those carrying only a single plus M1 strand. We suggest that VLPs carrying two M1 dsRNAs (each 1.8 kilobases) can exist because the particle is designed to carry one L-A dsRNA (4.5 kilobases).

Lending a hand: perceptions of green credit cards

2018 ◽  
Vol 36 (7) ◽  
pp. 1329-1346 ◽  
Author(s):  
Lei Huang ◽  
Julie Fitzpatrick
Keyword(s):  
Social Exchange ◽  
Undergraduate Students ◽  
Credit Card ◽  
Symbolic Interaction ◽  
Environmental Concern ◽  
Credit Cards ◽  
Medium Size ◽  
Content Type ◽  
The Usa ◽  
The Impact

Purpose The purpose of this paper is to explore the impact of donation amount and framing on financial products, this research investigates consumers’ attitudes and behaviors toward cause-related credit cards with different donation sizes and framing types. Design/methodology/approach This research investigates consumers’ perceptions of green credit cards using two experiments with a between-subject design (n =297) and a mixed design (n =238), respectively. All the participants, recruited from a major state university in the USA, are undergraduate students who use credit cards. Findings A medium-size donation optimizes the outcome of a cause-related credit card offer. Moreover, a donation framed as cash rewards has stronger effects on a consumer’s perception and consequent reactions to the “green” credit cards than an annual percentage rate framing. Finally, consumers with high levels of environmental concern and propensity to volunteer have stronger intention to adopt and are more likely to recommend the proposed credit card. Originality/value Building upon the theories of social exchange and symbolic interaction, this research is the first to provide empirical evidence regarding the application of volunteerism and perceived consumer effectiveness for financial institutions and their cause-related marketing campaign partners in selecting suitable environmental causes.

scholarly journals Finding of Agr Phase Variants in Staphylococcus aureus

mBio ◽  
2019 ◽  
Vol 10 (4) ◽  
Author(s):  
Vishal Gor ◽  
Aya J. Takemura ◽  
Masami Nishitani ◽  
Masato Higashide ◽  
Veronica Medrano Romero ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Virulence Factors ◽  
Phase Variation ◽  
Accessory Gene ◽  
Content Type ◽  
Accessory Gene Regulator ◽  
Immune Mediated ◽  
A Minor ◽  
First Time ◽  
Phase Variants

ABSTRACT Staphylococcus aureus is an important human pathogen whose success is largely attributed to its vast arsenal of virulence factors that facilitate its invasion into, and survival within, the human host. The expression of these virulence factors is controlled by the quorum sensing accessory gene regulator (Agr) system. However, a large proportion of clinical S. aureus isolates are consistently found to have a mutationally inactivated Agr system. These mutants have a survival advantage in the host but are considered irreversible mutants. Here we show, for the first time, that a fraction of Agr-negative mutants can revert their Agr activity. By serially passaging Agr-negative strains and screening for phenotypic reversion of hemolysis and subsequent sequencing, we identified two mutational events responsible for reversion: a genetic duplication plus inversion event and a poly(A) tract alteration. Additionally, we demonstrate that one clinical Agr-negative methicillin-resistant S. aureus (MRSA) isolate could reproducibly generate Agr-revertant colonies with a poly(A) tract genetic mechanism. We also show that these revertants activate their Agr system upon phagocytosis. We propose a model in which a minor fraction of Agr-negative S. aureus strains are phase variants that can revert their Agr activity and may act as a cryptic insurance strategy against host-mediated stress. IMPORTANCE Staphylococcus aureus is responsible for a broad range of infections. This pathogen has a vast arsenal of virulence factors at its disposal, but avirulent strains are frequently isolated as the cause of clinical infections. These isolates have a mutated agr locus and have been believed to have no evolutionary future. Here we show that a fraction of Agr-negative strains can repair their mutated agr locus with mechanisms resembling phase variation. The agr revertants sustain an Agr OFF state as long as they exist as a minority but can activate their Agr system upon phagocytosis. These revertant cells might function as a cryptic insurance strategy to survive immune-mediated host stress that arises during infection.

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