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25. Sept. 2023
Viruses are ubiquitous and versatile and are found in places where no one would look for them. Studying them helps us understand the mechanisms of their adaptability to a host (plant, animal or even human), the degree of aggression they may have, or the reasons they choose their host. The challenge for science is to grasp these mechanisms as widely as possible and to open the door for other researchers. The research, to which CEITEC MUNI scientist Danyil Grybchuk contributed, was published recently in BMC Biology journal and is a great example of the study aimed at broadening our knowledge of RNA virus diversity and evolution.
The parasitic flagellates of the family Trypanosomatidae are currently divided into more than two dozen genera. The vast majority peacefully inhabit digestive tracts of various insects. However, some of them, like Leishmania major and Trypanosoma brucei, evolved the ability to infect humans causing life-threatening diseases affecting millions of people in tropical regions. The mechanisms of diseases caused by trypanosomatids were the subject of intense studies for many years. In 2011 it was shown that an RNA virus contained in the parasite Leishmania guyanensis may worsen the symptoms of human disease caused by the parasite. “This was the moment when we decided to embark on virus hunt in all those diverse trypanosomatid species,” says Danyil Grybchuk, at that time a PhD student of University of Ostrava. “Our goal was quite simple back then: to find if there are relatives of that nasty virus. But, as usually, the reality turned out to be much more interesting. We found that it was just one of seven different types of RNA viruses infecting this group of unicellular organisms. And the quest still continues to this day.”
Current study deals with RNA viruses in only a single trypanosomatid species Leptomonas pyrrhocoris. This flagellate parasitises common firebug (Pyrrhocoris apterus), which is widespread throughout the world. Through systematic sampling across Europe, scientists have significantly expanded the range of known viruses in Leptomonas pyrrhocoris – in addition to the two previously known virus types, they have documented four new species from the family Leishbuviridae as well as a virus from family Qinviridae, the first detection of this rare virus in a trypanosomatid host.
Although many genome sequences of the Qinviridae virus were already in databases, they were from metagenomic studies of mosquitoes. This means that scientists at that time examined individual sequences of the mosquito's RNA molecules, including parts of the food and microorganisms it carried. These metagenomic studies were originally aimed at discovering new human pathogenic viruses, but as a "by-product" they also revealed a new virus family, Qinviridae. However, it was only through the work with pure cultures of unicellular organisms, that it was clearly confirmed that the host of this Qinviridae species is the parasitic flagellate Leptomonas pyrrhocoris.
Another important finding concerned the aforementioned new species of leishbuviruses, which were peculiar in having longer medium and small genomic segments compared to similar viruses in other trypanosomatids. In this regard leishbuviruses from L. pyrrhocoris were more resembling insect bunyaviruses from family Phenuiviridae. This led to conclusion that leishbuviruses evolved from insect bunyaviruses and the progressive length reduction of the medium and small genomic segments resulted from adaptation to a new host.
Either way, "this research opens up new possibilities for scientists in discovering nature, exploring patterns and learning how smaller things are arranged into larger ones. The challenge for scientists is to untangle these intricate connections and find all the nuances that have not yet been discovered," says Danyil Grybchuk of CEITEC Masaryk University, co-author of the study.
The full text of the study is published on the BMC Biology website: Diversity of RNA viruses in the cosmopolitan monoxenous trypanosomatid Leptomonas pyrrhocoris | BMC Biology | Full Text (biomedcentral.com)
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