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Article Writer-   Minakshi  Kumari, MSc. Biotechnology, RCA, Maharana Pratap University of Agriculture and Technology, Udaipur, Rajsthan(India)

Nucleus, genetic material containing organelle in eukaryotic cells, has been probably evolved from the giant viruses, said Masaharu Takemura, Virologist at Tokyo University.

Takemura hypothesized that the giant viruses infected early eukaryotic cells having unbound DNA. These viruses used the cytoplasmic membrane of the cell, drawing it around tight to protect the viral replication process within the cell.

By the time, the same mechanism was developed by the host cells to protect its own genetic material from viral attack along with the development of gene for histone proteins. Now, these genes are also found in viral DNA.

The similarity between the nuclear membrane and the membrane used by the virus to replicate within the cells led to the assumption that our ancestral cells fabricated a virus-like strategy to protect itself from the viral attack.

Also, there are some proteins in the eukaryotes which are also found in giant viruses but not in bacteria and archaea. Eg. Protein that caps messenger RNA. Molecular analysis of poxvirus (a kind of giant viruses) DNA polymerase is also closely related to the DNA polymerase of that of eukaryotic cells.

“I speculate that a portion of viral DNA replication may have aided host genome replication and proved evolutionarily advantageous,” Takemura wrote.

This hypothesis paves the way for discussion on the role of viruses in the evolution of the eukaryotic nucleus and further evolution of organisms.

Reference:

Medusavirus Ancestor in a Proto-Eukaryotic Cell: Updating the Hypothesis for the Viral Origin of the Nucleus, https://doi.org/10.3389/fmicb.2020.571831