Scent of a killer: How killer yeast boost its dispersal

Vector-borne parasites often manipulate hosts to attract uninfected vectors. For example, parasites causing malaria alter host odor to attract mosquitoes. Here we discuss the ecology and evolution of fruit-colonizing yeast in a tripartite symbiosis – the so-called “killer yeast” system. “Killer yeast” consists of Saccharomyces cerevisiae yeast hosting two double stranded RNA viruses (M satellite dsRNAs, L-A dsRNA helper virus). When both dsRNA viruses occur in a yeast cell, the yeast converts to lethal toxin‑producing “killer yeast” phenotype that kills uninfected yeasts. Yeasts on ephemeral fruits attract insect vectors to colonize new habitats. As the viruses have no extracellular stage, they depend on the same insect vectors as yeast for their dispersal. Viruses also benefit from yeast dispersal as this promotes yeast to reproduce sexually, which is how viruses can transmit to uninfected yeast strains. We tested whether insect vectors are more attracted to killer yeasts than to non‑killer yeasts. In our field experiment, we found that killer yeasts were more attractive to Drosophila than non-killer yeasts. This suggests that vectors foraging on yeast are more likely to transmit yeast with a killer phenotype, allowing the viruses to colonize those uninfected yeast strains that engage in sexual reproduction with the killer yeast. Beyond insights into the basic ecology of the killer yeast system, our results suggest that viruses could increase transmission success by manipulating the insect vectors of their host.

Download Full-text

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

Applied and Environmental Microbiology ◽

10.1128/aem.06518-11 ◽

2011 ◽

Vol 78 (3) ◽

pp. 735-743 ◽

Cited By ~ 19

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.

Download Full-text

Improved detection of flaviviruses in Australian mosquito populations via replicative intermediates

Journal of General Virology ◽

10.1099/jgv.0.001617 ◽

2021 ◽

Vol 102 (7) ◽

Author(s):

Caitlin A. O'Brien ◽

Jessica J. Harrison ◽

Agathe M. G. Colmant ◽

Renee J. Traves ◽

Devina Paramitha ◽

...

Keyword(s):

Monoclonal Antibodies ◽

Untranslated Regions ◽

Fixation Method ◽

Enveloped Viruses ◽

Double Stranded Rna ◽

Vertebrate Cell ◽

Infected Cells ◽

Replicative Intermediates ◽

Dsrna Viruses ◽

Arboviral Disease

Mosquito-borne flaviviruses are significant contributors to the arboviral disease burdens both in Australia and globally. While routine arbovirus surveillance remains a vital exercise to identify known flaviviruses in mosquito populations, novel or divergent and emerging species can be missed by these traditional methods. The MAVRIC (monoclonal antibodies to viral RNA intermediates in cells) system is an ELISA-based method for broad-spectrum isolation of positive-sense and double-stranded RNA (dsRNA) viruses based on detection of dsRNA in infected cells. While the MAVRIC ELISA has successfully been used to detect known and novel flaviviruses in Australian mosquitoes, we previously reported that dsRNA could not be detected in dengue virus-infected cells using this method. In this study we identified additional flaviviruses which evade detection of dsRNA by the MAVRIC ELISA. Utilising chimeric flaviviruses we demonstrated that this outcome may be dictated by the non-structural proteins and/or untranslated regions of the flaviviral genome. In addition, we report a modified fixation method that enables improved detection of flavivirus dsRNA and inactivation of non-enveloped viruses from mosquito populations using the MAVRIC system. This study demonstrates the utility of anti-dsRNA monoclonal antibodies for identifying viral replication in insect and vertebrate cell systems and highlights a unique characteristic of flavivirus replication.

Download Full-text

Separation and sequence of the 3′ termini of M double-stranded RNA from killer yeast

Nucleic Acids Research ◽

10.1093/nar/10.5.1661 ◽

1982 ◽

Vol 10 (5) ◽

pp. 1661-1678 ◽

Cited By ~ 21

Author(s):

Dennis J. Thiele ◽

Regina W. Wang ◽

Michael J. Leibowitz

Keyword(s):

Double Stranded Rna ◽

Killer Yeast

Download Full-text

Probing the Transcription Mechanisms of Reovirus Cores with Molecules That Alter RNA Duplex Stability

Journal of Virology ◽

10.1128/jvi.02192-08 ◽

2009 ◽

Vol 83 (11) ◽

pp. 5659-5670 ◽

Cited By ~ 2

Author(s):

Alexander A. Demidenko ◽

Max L. Nibert

Keyword(s):

Small Molecules ◽

Dimethyl Sulfoxide ◽

Active Fraction ◽

Core Particle ◽

Double Stranded Rna ◽

Promoter Escape ◽

Duplex Stability ◽

Rna Duplexes ◽

Dsrna Viruses ◽

Transcript Initiation

ABSTRACT The mammalian reovirus (MRV) genome comprises 10 double-stranded RNA (dsRNA) segments, packaged along with transcriptase complexes inside each core particle. Effects of four small molecules on transcription by MRV cores were studied for this report, chosen for their known capacities to alter RNA duplex stability. Spermidine and spermine, which enhance duplex stability, inhibited transcription, whereas dimethyl sulfoxide and trimethylglycine, which attenuate duplex stability, stimulated transcription. Different mechanisms were identified for inhibition or activation by these molecules. With spermidine, one round of transcription occurred normally, but subsequent rounds were inhibited. Thus, inhibition occurred at the transition between the end of elongation in one round and initiation in the next round of transcription. Dimethyl sulfoxide or trimethylglycine, on the other hand, had no effect on transcription by a constitutively active fraction of cores in each preparation but activated transcription in another fraction that was otherwise silent for the production of elongated transcripts. Activation of this other fraction occurred at the transition between transcript initiation and elongation, i.e., at promoter escape. These results suggest that the relative stability of RNA duplexes is most important for certain steps in the particle-associated transcription cycles of dsRNA viruses and that small molecules are useful tools for probing these and probably other steps.

Download Full-text

Experimental tests of host-virus coevolution in natural killer yeast strains

Journal of Evolutionary Biology ◽

10.1111/jeb.13044 ◽

2017 ◽

Vol 30 (4) ◽

pp. 773-781 ◽

Cited By ~ 6

Author(s):

M. D. Pieczynska ◽

R. Korona ◽

J. A. G. M. De Visser

Keyword(s):

Natural Killer ◽

Experimental Tests ◽

Killer Yeast ◽

Yeast Strains

Download Full-text

Dual Role of a Viral Polymerase in Viral Genome Replication and Particle Self-Assembly

mBio ◽

10.1128/mbio.01242-18 ◽

2018 ◽

Vol 9 (5) ◽

Cited By ~ 2

Author(s):

Xiaoyu Sun ◽

Serban L. Ilca ◽

Juha T. Huiskonen ◽

Minna M. Poranen

Keyword(s):

Self Assembly ◽

Viral Genome ◽

Rna Viruses ◽

The Self ◽

Genome Replication ◽

Double Stranded Rna ◽

Polymerase Complex ◽

Viral Genome Replication ◽

Dsrna Viruses

ABSTRACTDouble-stranded RNA (dsRNA) viruses package several RNA-dependent RNA polymerases (RdRp) together with their dsRNA genome into an icosahedral protein capsid known as the polymerase complex. This structure is highly conserved among dsRNA viruses but is not found in any other virus group. RdRp subunits typically interact directly with the main capsid proteins, close to the 5-fold symmetric axes, and perform viral genome replication and transcription within the icosahedral protein shell. In this study, we utilizedPseudomonasphage Φ6, a well-established virus self-assembly model, to probe the potential roles of the RdRp in dsRNA virus assembly. We demonstrated that Φ6 RdRp accelerates the polymerase complex self-assembly process and contributes to its conformational stability and integrity. We highlight the role of specific amino acid residues on the surface of the RdRp in its incorporation during the self-assembly reaction. Substitutions of these residues reduce RdRp incorporation into the polymerase complex during the self-assembly reaction. Furthermore, we determined that the overall transcription efficiency of the Φ6 polymerase complex increased when the number of RdRp subunits exceeded the number of genome segments. These results suggest a mechanism for RdRp recruitment in the polymerase complex and highlight its novel role in virion assembly, in addition to the canonical RNA transcription and replication functions.IMPORTANCEDouble-stranded RNA viruses infect a wide spectrum of hosts, including animals, plants, fungi, and bacteria. Yet genome replication mechanisms of these viruses are conserved. During the infection cycle, a proteinaceous capsid, the polymerase complex, is formed. An essential component of this capsid is the viral RNA polymerase that replicates and transcribes the enclosed viral genome. The polymerase complex structure is well characterized for many double-stranded RNA viruses. However, much less is known about the hierarchical molecular interactions that take place in building up such complexes. Using the bacteriophage Φ6 self-assembly system, we obtained novel insights into the processes that mediate polymerase subunit incorporation into the polymerase complex for generation of functional structures. The results presented pave the way for the exploitation and engineering of viral self-assembly processes for biomedical and synthetic biology applications. An understanding of viral assembly processes at the molecular level may also facilitate the development of antivirals that target viral capsid assembly.

Download Full-text

Double-Stranded RNA Mycovirus from Fusarium graminearum

Applied and Environmental Microbiology ◽

10.1128/aem.68.5.2529-2534.2002 ◽

2002 ◽

Vol 68 (5) ◽

pp. 2529-2534 ◽

Cited By ~ 115

Author(s):

Yeon-Mee Chu ◽

Jae-Jin Jeon ◽

Sang-Jin Yea ◽

Yong-Ho Kim ◽

Sung-Hwan Yun ◽

...

Keyword(s):

Fusarium Graminearum ◽

Morphological Changes ◽

Yellow Mosaic Virus ◽

Donor Strain ◽

Biological Control Agents ◽

Rna Dependent Rna Polymerase ◽

Double Stranded Rna ◽

Hyphal Fusion ◽

Barley Yellow Mosaic Virus ◽

Dsrna Viruses

ABSTRACT Double-stranded RNA (dsRNA) viruses in some fungi are associated with hypovirulence and have been used or proposed as biological control agents. We isolated 7.5-kb dsRNAs from 13 of 286 field strains of Fusarium graminearum isolated from maize in Korea. One of these strains, DK21, was examined in more detail. This strain had pronounced morphological changes, including reduction in mycelial growth, increased pigmentation, reduced virulence towards wheat, and decreased (60-fold) production of trichothecene mycotoxins. The presence or absence of the 7.5-kb dsRNA was correlated with the changes in pathogenicity and morphology. The dsRNA could be transferred to virus-free strains by hyphal fusion, and the recipient strain acquired the virus-associated phenotype of the donor strain. The dsRNA was transmitted to approximately 50% of the conidia, and only colonies resulting from conidia carrying the mycovirus had the virus-associated phenotype. Partial nucleotide sequences of the purified dsRNA identify an RNA-dependent RNA polymerase sequence and an ATP-dependent helicase that are closely related to those of Cryphonectria hypovirus and Barley yellow mosaic virus. Collectively, these results suggest that this dsRNA isolated from F. graminearum encodes traits for hypovirulence.

Download Full-text

Cleavage of the double stranded RNA genome of killer yeast

Current Genetics ◽

10.1007/bf00435219 ◽

1982 ◽

Vol 6 (2) ◽

pp. 171-172 ◽

Cited By ~ 1

Author(s):

Friedhelm Meinhardt

Keyword(s):

Double Stranded Rna ◽

Killer Yeast ◽

Rna Genome

Download Full-text

A FIVE-YEAR SURVEY IN TUSCANY (ITALY) AND DETECTION OF XYLELLA FASTIDIOSASUBSPECIES MULTIPLEXIN POTENTIAL INSECT VECTORS, COLLECTED IN MONTE ARGENTARIO

Redia ◽

10.19263/redia-104.21.09 ◽

2021 ◽

Vol 104 ◽

pp. 75-88

Author(s):

ELISABETTA GARGANI ◽

CLAUDIA BENVENUTI ◽

LEONARDO MARIANELLI ◽

PIO FEDERICO ROVERSI ◽

MASSIMO RICCIOLINI ◽

...

Keyword(s):

High Risk ◽

Xylella Fastidiosa ◽

Xylem Sap ◽

Insect Vectors ◽

Philaenus Spumarius ◽

The Family ◽

Infected Area ◽

Vector Borne ◽

Very High ◽

Cicadella Viridis

The vector‐borne bacterium Xylella fastidiosa(Wells and Raju) causes several serious diseases to plants. Recently, different subspecies of X. fastidiosa were reported in some European countries. The risk of the bacterium’s spread on the entire European territory is very high; therefore, it has been added into the priority pest list (2019/1702/EU Regulation). The main purposes of this work were to verify the presence of potential vectors in areas at a high risk of introduction in Tuscany and to ascertain the presence of X. fastidiosa in these insect vectors. Over 4,000 Auchenorrhyncha were collected and analysed from 2015 to 2019. Among the xylem sap-feeder putative vectors, most of the insects collected belonged to the family Aphrophoridae, but also many species of leafhopper were identified. Overall, in Tuscany four species were the most represented: Philaenus spumarius(L.), Cicadella viridis(L.), Synophropsis lauri (Horvath) and Neophilaenus campestris(Fallen).In 2018 an outbreak of X. fastidiosa subsp. multiplex was reported in Monte Argentario (Grosseto province, Tuscany). In 2019 X. fastidiosa subspecies multiplex ST 87 was detected in seven P. spumarius and three N. campestris collected from the infected area.

Download Full-text

Cultivation of a lytic double-stranded RNA bacteriophage infecting Microvirgula aerodenitrificans reveals a mutualistic parasitic lifestyle

Journal of Virology ◽

10.1128/jvi.00399-21 ◽

2021 ◽

Author(s):

Xiaoyao Cai ◽

Fengjuan Tian ◽

Li Teng ◽

Hongmei Liu ◽

Yigang Tong ◽

...

Keyword(s):

Double Layer ◽

Sequence Similarity ◽

Double Stranded Rna ◽

Bacteria Growth ◽

A Genome ◽

Domains Of Life ◽

Parasitic Lifestyle ◽

Dsrna Viruses ◽

Fungal Viruses ◽

Classical Protocol

Bacteriophages are considered the most abundant entities on earth. However, there are merely seven sequenced double-stranded (ds)RNA phages compared with thousands of dsDNA phages. Interestingly, dsRNA viruses are quite common in fungi and usually have a lifestyle of commensalism or mutualism. Thus, the classical protocol of using double-layer agar plates to characterize phage plaques might be significantly biased in the isolation of dsRNA phages beyond strictly lytic lifestyles. Thus, we applied the protocol of isolating fungal viruses to identify RNA phages in bacteria and successfully isolated a novel dsRNA phage, phiNY, from Microvirgula aerodenitrificans . phiNY has a genome of three dsRNA segments, and its genome sequence has no nucleotide sequence similarity with any other phage. Although phiNY encodes a lytic protein of glycoside hydrolase and phage particles are consistently released during bacterial growth, phiNY replication did not block bacteria growth, nor did it form any plaque on agar plates. More strikingly, the phiNY-infected strain grew faster than the phiNY-negative strain, indicating a mutualistic parasitic lifestyle. Thus, this study not only reveals a new mutualistic parasitic dsRNA phage but also implies that other virus isolation methods would be valuable to identify phages with other lifestyles. Importance Viruses with dsRNA genomes are quite diverse and infect organisms in all three domains of life. Though dsRNA viruses infecting humans, plants and fungi are quite common, dsRNA viruses infecting bacteria, known as bacteriophages, are quite understudied and only seven dsRNA phages have been sequenced so far. One possible explanation for the rare isolation of dsRNA phages might be the protocols of double-layer agar plates assay. Phages beyond strictly lytic lifestyles might not form plaques. Thus, we applied the protocol of isolating fungal viruses to identify RNA phages inside bacteria and successfully isolated a novel dsRNA phage phiNY with a mutualistic parasitic lifestyle. This study implies dsRNA phages beyond strictly lytic lifestyle might be common in nature and deserves more investigations.

Download Full-text