viroid

American  

[vahy-roid] / ˈvaɪ rɔɪd /

noun

1. an infectious agent of plants similar to a virus but consisting of only a short, single strand of RNA without a protein coat.

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viroid British  

/ ˈvaɪrɔɪd /

noun

1. any of various infective RNA particles, smaller than a virus and known to cause some plant diseases

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viroid Scientific  

/ vī′roid′ /

1. An infectious agent that consists solely of a single strand of RNA and causes disease in certain plants. Viroids lack the protein coat (known as a capsid) of viruses and are the smallest known infectious agents. Containing only about 250 to 375 base pairs, they are much smaller than the smallest genomes of viruses and have no genes for encoding proteins. After invading a host cell, viroids are thought to mimic the cell's DNA, so that the cell's RNA polymerase replicates them in the nucleus. Viroids are believed to cause disease by interfering with the host cell's gene regulation. They are destructive to many important commercial plants, including potatoes, tomatoes, cucumbers, coconuts, and chrysanthemums.

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Etymology

Origin of viroid

First recorded in 1946; vir(us) + -oid

Example Sentences

After identifying the viroid that caused spindle tuber disease, he helped develop a test to detect it.

From New York Times • May 8, 2023

A viroid functions in a manner similar to that of a virus, invading a cell and making it reproduce the viroid’s RNA.

From Washington Post • Apr. 13, 2023

But Dr. Diener’s research proved that a viroid — so small that it is barely visible even with an electron microscope — can indeed mount an effective attack.

From Washington Post • Apr. 13, 2023

Unlike a virus, a viroid has no protein coat.

From Washington Post • Apr. 13, 2023

Inspectors, who have to certify that the plants are free of viruslike microorganisms known as viroids, must wait until the trees bear fruit and check the apples and pears for viroid scarring and spotting.

From Time Magazine Archive