nanoviruses

Nanoviruses are a genus of exceptionally small, single-stranded DNA viruses belonging to the family Geminiviridae. These viruses are known for their unique, distinctive structure and their association with significant plant diseases. Nanoviruses are characterized by their capsids, which are icosahedral in shape and approximately 18-20 nanometers in diameter, making them among the smallest known plant viruses.

The genome of nanoviruses is monopartite, meaning it consists of a single circular DNA molecule. This genome typically encodes for a limited number of proteins, often including a replication-associated protein (Rep) essential for viral DNA replication, a movement protein (MP) that facilitates cell-to-cell spread within the plant, and a coat protein (CP) that forms the viral capsid. They replicate in the nucleus of host plant cells, utilizing the host's cellular machinery.

Nanoviruses are transmitted by specific aphid vectors, which acquire the virus while feeding on an infected plant and then transmit it to a healthy plant during subsequent feeding. This aphid-mediated transmission is crucial for the spread of nanovirus diseases. Symptoms of nanovirus infection in plants can vary but often include stunting, leaf curling, yellowing (chlorosis), and reduced yield.

Economically important crops are susceptible to nanoviruses, leading to significant agricultural losses in various regions worldwide. Examples of diseases caused by nanoviruses include faba bean necrotic yellows virus and cowpea stunt virus. Research continues to understand their biology, host interactions, and to develop strategies for disease management.