A virus has a very simple makeup. It is just a piece of DNA or RNA, a protein coat, and in some cases a fatty (lipid) layer. The protein coat provides protection for the piece of genetic information (DNA or RNA), and can code for different functions when the virus infects a host organism.
Viruses are considered neither alive nor dead. Viruses do not consist of cells or have any components to carry out basic functions on their own. They rely on the cell functions of their host to replicate. They hijack their host’s cells to operate in a way that allows the virus to thrive.
For this exact reason, viruses have a biological incentive to keep their hosts alive. If their hosts die, the virus can no longer replicate. Viable virus particles can exist on a surface, such as a table. But without a host, the virus can not cause disease or infection.
The first virus to be crystallized and therefore each of its parts were able to be studied, was actually a plant virus, Tobacco mosaic virus. Rosalind Franklin made this discovery in 1955. Since then, thousands of new viruses have been described.
Potato virus Y (PVY) is one of the oldest known plant viruses, and the 5th most economically important plant virus in the world, meaning that it can cause a lot of damage. Hundreds of plants can infected by PVY including potato, tomato, pepper, eggplant, tobacco, and many species of weeds.
Historically, PVY has been easy to detect in fields because of the beautiful mosaic symptoms it causes on foliage. On potatoes, other symptoms include veinal necrosis, deformed or rotting (necrotic) potatoes, and up to 70% yield losses.
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