RESUMEN
Almost two decades after the isolation of the first amoebal giant viruses, indubitably the discovery of these entities has deeply affected the current scientific knowledge on the virosphere. Much has been uncovered since then: viruses can now acknowledge complex genomes and huge particle sizes, integrating remarkable evolutionary relationships that date as early as the emergence of life on the planet. This year, a decade has passed since the first studies on giant viruses in the Brazilian territory, and since then biomes of rare beauty and biodiversity (Amazon, Atlantic forest, Pantanal wetlands, Cerrado savannas) have been explored in the search for giant viruses. From those unique biomes, novel viral entities were found, revealing never before seen genomes and virion structures. To celebrate this, here we bring together the context, inspirations, and the major contributions of independent Brazilian research groups to summarize the accumulated knowledge about the diversity and the exceptionality of some of the giant viruses found in Brazil.
Asunto(s)
Amoeba/virología , Virus Gigantes/genética , Virus Gigantes/aislamiento & purificación , Virología/historia , Biodiversidad , Brasil , Ecosistema , Genoma Viral , Virus Gigantes/clasificación , Virus Gigantes/ultraestructura , Historia del Siglo XXI , FilogeniaRESUMEN
The virosphere is fascinatingly vast and diverse, but as mandatory intracellular parasites, viral particles must reach the intracellular space to guarantee their species' permanence on the planet. While most known viruses that infect animals explore the endocytic pathway to enter the host cell, a diverse group of ancient viruses that make up the phylum Nucleocytoviricota appear to have evolved to explore new access' routes to the cell's cytoplasm. Giant viruses of amoeba take advantage of the phagocytosis process that these organisms exploit a lot, while phycodnavirus must actively break through a algal cellulose cell wall. The mechanisms of entry into the cell and the viruses themselves are diverse, varying in the steps of adhesion, entry, and uncoating. These are clues left by evolution about how these organisms shaped and were shaped by convoluting with eukaryotes.
Asunto(s)
Virus Gigantes/fisiología , Internalización del Virus , Amoeba/virología , Animales , Coevolución Biológica , Chlorella/virología , Virus Gigantes/clasificación , Acoplamiento Viral , Desencapsidación ViralRESUMEN
Giant viruses of amoebas are a remarkable group of viruses. In addition to their large size and peculiar structures, the genetic content of these viruses is also special. Among the genetic features of these viruses that stand out is the presence of coding regions for elements involved in translation, a complex biological process that occurs in cellular organisms. No viral genome described so far has such a complex genetic arsenal as those of giant viruses, which code for several of these elements. Currently, tupanviruses have the most complete set of translation genes in the known virosphere. In this review, we have condensed what is currently known about translation genes in different groups of giant viruses and theorize about their biological importance, origin, and evolution, and what might possibly be found in the coming years.
Asunto(s)
Virus Gigantes/genética , Mimiviridae/genética , Amoeba/virología , Evolución Molecular , Genoma Viral , Virus Gigantes/patogenicidad , Especificidad del Huésped/genética , Mimiviridae/metabolismo , Mimiviridae/ultraestructura , Filogenia , Biosíntesis de Proteínas , Proteoma/genética , ARN Ribosómico 16S/genética , ARN Viral/genéticaRESUMEN
Since the discovery of mimivirus, numerous giant viruses associated with free-living amoebae have been described. The genome of giant viruses can be more than 2.5 megabases, and virus particles can exceed the size of many bacteria. The unexpected characteristics of these viruses have made them intriguing research targets and, as a result, studies focusing on their interactions with their amoeba host have gained increased attention. Studies have shown that giant viruses can establish host-pathogen interactions, which have not been previously demonstrated, including the unprecedented interaction with a new group of small viruses, called virophages, that parasitize their viral factories. In this brief review, we present recent advances in virophage-giant virus-host interactions and highlight selected studies involving interactions between giant viruses and amoebae. These unprecedented interactions involve the giant viruses mimivirus, marseillevirus, tupanviruses and faustovirus, all of which modulate the amoeba environment, affecting both their replication and their spread to new hosts.
Asunto(s)
Amoeba/virología , Virus Gigantes/fisiología , Interacciones Huésped-Patógeno , Amoeba/fisiología , Vesículas Extracelulares/metabolismo , Vesículas Extracelulares/virología , Genoma Viral , Especificidad del Huésped , Mimiviridae/fisiología , Modelos Biológicos , Virófagos/fisiología , Replicación ViralRESUMEN
In the last few decades, the isolation of amoebae-infecting giant viruses has challenged established principles related to the definition of virus, their evolution, and their particle structures represented by a variety of shapes and sizes. Tupanviruses are one of the most recently described amoebae-infecting viruses and exhibit a peculiar morphology with a cylindrical tail attached to the capsid. Proteomic analysis of purified viral particles revealed that virions are composed of over one hundred proteins with different functions. The putative origin of these proteins had not yet been investigated. Here, we provide evidences for multiple origins of the proteins present in tupanvirus particles, wherein 20% originate from members of the archaea, bacteria and eukarya.
Asunto(s)
Virus Gigantes/química , Virus Gigantes/genética , Proteoma , Proteínas Virales/genética , Virión/química , Amoeba/virología , Archaea/genética , Bacterias/genética , Eucariontes/genética , Proteómica , Proteínas Virales/química , Virión/genéticaRESUMEN
The discovery of giant viruses in the last years has fascinated the scientific community due to virus particles size and genome complexity. Among such fantastic discoveries, we have recently described tupanviruses, which particles present a long tail, and has a genome that contains the most complete set of translation-related genes ever reported in the known virosphere. Here we describe a new kind of virus-host interaction involving tupanvirus. We observed that tupanvirus-infected amoebas were induced to aggregate with uninfected cells, promoting viral dissemination and forming giant host cell bunches. Even after mechanical breakdown of bunches, amoebas reaggregated within a few minutes. This remarkable interaction between infected and uninfected cells seems to be promoted by the expression of a mannose receptor gene. Our investigations demonstrate that the pre-treatment of amoebas with free mannose inhibits the formation of bunches, in a concentration-dependent manner, suggesting that amoebal-bunch formation correlates with mannose receptor gene expression. Finally, our data suggest that bunch-forming cells are able to interact with uninfected cells promoting the dissemination and increase of tupanvirus progeny.
Asunto(s)
Amoeba/virología , Agregación Celular/efectos de los fármacos , Virus Gigantes/patogenicidad , Interacciones Huésped-Patógeno , Virosis/transmisión , Amoeba/citología , Virus Gigantes/genética , Lectinas Tipo C/metabolismo , Manosa/farmacología , Receptor de Manosa , Lectinas de Unión a Manosa/metabolismo , Receptores de Superficie Celular/metabolismoRESUMEN
The discovery of giant viruses revealed a new level of complexity in the virosphere, raising important questions about the diversity, ecology, and evolution of these viruses. The family Mimiviridae was the first group of amoebal giant viruses to be discovered (by Bernard La Scola and Didier Raoult team), containing viruses with structural and genetic features that challenged many concepts of classic virology. The tupanviruses are among the newest members of this family and exhibit structural, biological, and genetic features never previously observed in other giant viruses. The complexity of these viruses has put us one step forward toward the comprehension of giant virus biology and evolution, but also has raised important questions that still need to be addressed. In this chapter, we tell the history behind the discovery of one of the most complex viruses isolated to date, highlighting the unique features exhibited by tupanviruses, and discuss how these giant viruses have contributed to redefining limits for the virosphere.
Asunto(s)
Especificidad del Huésped , Mimiviridae/fisiología , Biosíntesis de Proteínas , Proteínas Virales/genética , Amoeba/virología , Genoma Viral , Virus Gigantes/fisiología , Interacciones Huésped-Patógeno , Mimiviridae/aislamiento & purificación , Ribosomas/genética , Ribosomas/virología , Proteínas Virales/metabolismo , Replicación Viral/fisiologíaRESUMEN
Here we report the discovery of two Tupanvirus strains, the longest tailed Mimiviridae members isolated in amoebae. Their genomes are 1.44-1.51 Mb linear double-strand DNA coding for 1276-1425 predicted proteins. Tupanviruses share the same ancestors with mimivirus lineages and these giant viruses present the largest translational apparatus within the known virosphere, with up to 70 tRNA, 20 aaRS, 11 factors for all translation steps, and factors related to tRNA/mRNA maturation and ribosome protein modification. Moreover, two sequences with significant similarity to intronic regions of 18 S rRNA genes are encoded by the tupanviruses and highly expressed. In this translation-associated gene set, only the ribosome is lacking. At high multiplicity of infections, tupanvirus is also cytotoxic and causes a severe shutdown of ribosomal RNA and a progressive degradation of the nucleus in host and non-host cells. The analysis of tupanviruses constitutes a new step toward understanding the evolution of giant viruses.