Bad news for biologists, because part of the genetic research on plants may have to go in the trash: Dutch plant scientists have discovered that the most studied plant in the world appears to carry a virus.
Arabidopsis thalianaor the thale cress, has been used by biologists worldwide for decades as a ‘model plant’ for genetic research – certainly since the genome of the plant became publicly available in 2000. But in trade magazine New Phytologist Wageningen and Utrecht researchers wrote at the end of September about a hidden virus that many thale cress plants appear to carry: ArLV1 (Arabidopsis latent virus 1). As a result, data sets become contaminated and that has ‘possibly far-reaching consequences for research projects’, Utrecht University (UU) says in a statement on the website.
The virus was accidentally discovered by researchers Karen Kloth and René van der Vlugt of Wageningen University & Research (WUR). At the time, UU researcher Ava Verhoeven was working at WUR with a thale cress experiment by Kloth. In some samples, more than 90 percent of the RNA did not come from the plant, but from something else. ‘In Wageningen, the unknown RNA had already been compared with RNA from a large database,’ says Verhoeven. “Then it became clear that the RNA had to be from a still unknown virus.”
Later, together with colleagues, she also discovered unknown RNA in thale cress from the Utrecht lab, and it turned out to be the same virus. In the article in New Phytologist the scientists write how they analyzed datasets available online from other researchers to see if the virus was also present in them. They discovered that at least 8.5 percent of the data sets are infected with the virus. Presumably there are many more datasets involved, but not all studies with infected plant samples have been published in the end. In practice, RNA datasets with little plant RNA are often considered ‘failed’, and the results are therefore nowhere to be found. The virus itself does not cause obvious symptoms in plants. That way it could remain hidden for a long time.
ArLV1 occurs in a quarter of all hundreds of thale cress variants and has spread all over the world. Also with wild Arabidopsisvariants, the virus is present – it may even have ended up in the lab. The fact that it subsequently spread from lab to lab may be because biologists often exchange thale cress seed with each other.
It is not yet entirely clear what consequences the discovery will have for previously published thale cress research. A direct comparison of thale cress with and without (strong) viral infections showed no differences in gene expression, the researchers write in the article. However, it appears that ArVL1 has “a small but significant positive effect” on drought resistance, perhaps because the virus reduces the functioning of the stomata on the leaves. Other viruses are also known to make plants more resistant to drought.