Viruses are small invaders that cause many diseases, from rabies to tomato wilt virus and more recently, COVID-19 In humans. But viruses can do more than clear illness – and not all viruses are small.
Larger viruses, especially those large nucleo-cytoplasmic ones DNA The virus family can unify their genomes like their hosts – dramatically altering the organism’s genetic makeup. This family of DNA viruses, otherwise known as “giant” viruses, has long been known in scientific circles, but the extent to which they affect eukaryotic organisms is a mystery – yet.
“Viruses have a major role to play in the evolution of life on Earth. One way to shape the evolution of cellular life is through a process called endogenization, where they insert new genomic material into their hosts. When a giant virus enters the host algae’s genome, it makes a huge amount of raw material to work for evolution, ”said Frin, an assistant professor in the Department of Biological Sciences at Virginia Tech College College of Science and a subsidiary of the Global Change Center. Is.
Mohammed ‘Monir’ Moniruzzaman, a post-doctoral researcher in Alward’s lab, studies the underlying viral elements, which are fragments or complete sequences of raw viral DNA inserted into the genome of an infected host.
Together, Alvard and Moniruzmaz have recently discovered that the endocrine viral elements produced by the giant virus are more common in chlorophyll green algae than previously thought.
Their findings will be published today (November 18, 2020) Nature.
Left to right: Frank Alward, Mohamed ‘Monir’ Moniruzzaman, Elena Weinheimer, Carolina Alejandra Martinez Gutierrez. Image courtesy of Alex Croxash Hanks. Credit: Virginia Tech
A group of green algae, chlorophyll, is an important group of many photosynthetic organisms that are at the base of the food chain on many ecosystems and produce large amounts of food and oxygen on the planet. Chlorophytes thrive in our lakes and ponds – and their dynamics with giant viruses, as well as their unique evolutionary history, have been at the center of research for ward Elward and Moniruzman.
Chlorophyll algae are close relatives of soil plants, and a study of their interactions with giant viruses can shed some light on the roles played by viruses during the early development of plants.
“We now know that endocrine viral elements are common in chlorophyll, which makes you think that even plants can come into contact with this giant virus. There is some data that suggests that some early plants, such as moss and ferns, were experiencing these underlying events on an evolutionary timeline. But we are not sure about the extent of this phenomenon in other early plants, “said Moniruzmaz, the first author of this published paper.
To learn more about the prevalence of endogenous viral elements in algae, Moniruzzaman and Alvard performed bioinformatic analysis on the sequential genomes of different algae groups.
They found that 24 of the 65 organisms analyzed had some type of viral signature in their genome, resulting from repeated induction of different viruses. In an isolated organism called Tetrabaine socialis, researchers found that about 10 percent of its genes are stimulated by a virus from the nucleo-cytoplasmic large DNA virus family.
Although the endogenization of viruses has been well studied, studies are mostly limited to small RNA Viruses such as the Human Immunodeficiency Virus (HIV), retroviruses that are responsible for causing acquired immunodeficiency syndrome (AIDS).
The study of Alward and Moniruzzaman is the first to focus on large eukaryotic DNA viruses, marking large shifts in the field.
AAV’s electron micrograph image, a giant virus that infects and kills a unicellular algae that kills harmful algae. Huge viruses belonging to the same group as AAV, can repeatedly insert their genomes into the genes of their hosts. Image courtesy of Chuan Xiao and Yujao Xian, University of Texas, El Paso; Steven W. Wilhelm and Eric R. Gain, University of Tennessee, Knoxville.
“These large endogenous viral elements are much more common than previously thought. Now that we have systematic analysis, other researchers will really start paying attention. These studies show that endogenous viral elements are very common, and therefore may be the most common method of genome evolution. I think these results will expand our perspective on the role of giant viruses as mere agents of host mortality for significant players in the host genome evolution.
Now that Moniruzman and Ylward have confirmed that endogenization is taking place in the larger virus, they wonder what conditions are causing the virus to inject EVEs in green algae in the first place – and why the hosts are rejecting them. Do not show.
“We don’t know what the mechanism is or how DNA is maintained, but it is possible that endogenization is a random, almost accidental process. And once the viral DNA is endogenous, it can alter the evolutionary dynamics of the host, and it can further influence the evolution of that lineage, ”Eileward said.
Moniruzman is particularly interested in the idea of a potentially beneficial relationship between the host and his virus in the game.
“There may be a reason why the host keeps this viral genome inside them. It is not that these viral genes make hosts fail or survive in the environment. So the thing is: are end-lover viral elements beneficial to the host? And how will they get in there and stay there? Asked Moniruzman.
Ref: 18 November 2020, Nature.
DOI: 10.1038 / s41586-020-2924-2
