The Central Question in Virology: The Origin and Evolution of Viruses

Abstract

Viruses are major threats to both animals and plants worldwide. A virus exists as a set of one or more nucleic acid molecules normally encased in a protective coat of protein or lipoprotein. It is able to replicate itself within suitable host cells, causing diseases to plants and animals. While the three domains of life trace their linages back to a single protein (the Last Universal Cellular Ancestor (LUCA), information on parental molecule from which all viruses descended is inadequate. Structural analyses of capsid proteins suggest that there is no universal viral protein and different types of virions are mostly formed independently. As a result, it is impossible to neither include viruses in the Tree of Life of LUCA nor to draw a universal tree of viruses analogous to the tree of life. Although the concepts on the origin and evolution of viruses are well documented, the structure and biological activities of viruses are paradoxical. This assay will provide a brief background on the discovery of viruses and highlight the universal hypotheses that have been adopted to explain the origin of viruses. The text will also look at the current views on the nature of viruses and how they evolved; and an attempt will be made to draw some assumptions towards understanding of how modern viruses originated. The views formulated would shed some lights on understanding of viruses and their evolution.