Plants can 'switch off' virus DNA

August 22, 2014
Plants can 'switch off' virus DNA

A team of virologists and plant geneticists at Wageningen UR has demonstrated that when tomato plants contain Ty-1 resistance to the important Tomato yellow leaf curl virus (TYLCV), parts of the virus DNA (the genome) become hyper-methylated, the result being that virus replication and transcription is inhibited. The team has also shown that this resistance has its Achilles heel: if a plant is simultaneously infected with another important (RNA) virus, the Cucumber mosaic virus (CMV), the resistance mechanism is compromised.

Antiviral defence via RNAi

Plant defence to viruses usually depends on RNA interference (RNAi). The genetic material of many viruses consists of RNA. A complex process in the plant causes the virus RNA to be chopped up into pieces, which means the virus can no longer multiply. In contrast to most other disease-causing plant viruses, the genetic material in TYLCV is DNA, not RNA. Therefore antiviral RNAi defence to these viruses has to happen somewhat different.

TYLCV is one of the most economically important plant viruses in the world; for this virus a number of resistance genes (Ty-1 to Ty-6) are available to commercial plant breeders. In 2013 the researchers in Wageningen succeeded in identifying and cloning the Ty-1 gene, which happened to present a member from an important class of RNAi-pathway genes. This led to a publication in PLoS Genetics. Their recent publication in the journal PNAS shows that although Ty-1 resistance depends on RNAi, instead of the genetic material being chopped up, it is being 'blocked' by methylation of the virus DNA.

No cross protection

A well-known phenomenon in the plant world is the 'immunisation' of plants by infecting them with relatively harmless viruses. The latter ensures that the defence mechanisms in plants are activated and provide 'cross protection' against more harmful, related viruses.

To their great surprise, the Wageningen researchers discovered that infection with CMV, a virus that contains RNA as and that, as a result, is not affected by the Ty-1 resistance mechanism, actually compromised resistance to the TYLCV . According to the researchers, this is a warning to plant breeders. The use of the Ty-1 gene does provide resistance, but the mechanism will be at risk in plants grown in greenhouses and fields if the plants are attacked by various other types of viruses.

Explore further: People also have antiviral 'plant defences'

More information: Patrick Butterbach, Maarten G. Verlaan, Annette Dullemans, Dick Lohuis, Richard G. F. Visser, Yuling Bai, and Richard Kormelink. "Tomato yellow leaf curl virus resistance by Ty-1 involves increased cytosine methylation of viral genomes and is compromised by cucumber mosaic virus infection." PNAS 2014 ; published ahead of print August 18, 2014, DOI: 10.1073/pnas.1400894111

Related Stories

People also have antiviral 'plant defences'

September 27, 2010

In addition to known antiviral agents such as antibodies and interferons, people also seem to have a similar immune system to that previously identified in plants. This is the result of research carried out by Esther Schnettler ...

Virus rounds up enzymes, disarms plant

June 2, 2014

University of Tokyo researchers have described how a plant-virus protein suppresses an important plant defense mechanism that remembers viral genetic information, providing a new target for developing the first-ever chemical ...

Mammals defend against viruses differently than invertebrates

June 23, 2014

Biologists have long wondered if mammals share the elegant system used by insects, bacteria and other invertebrates to defend against viral infection. Two back-to-back studies in the journal Science last year said the answer ...

Recommended for you

New gene map reveals cancer's Achilles heel

November 25, 2015

Scientists have mapped out the genes that keep our cells alive, creating a long-awaited foothold for understanding how our genome works and which genes are crucial in disease like cancer.

Study suggests fish can experience 'emotional fever'

November 25, 2015

(—A small team of researchers from the U.K. and Spain has found via lab study that at least one type of fish is capable of experiencing 'emotional fever,' which suggests it may qualify as a sentient being. In their ...

How cells in the developing ear 'practice' hearing

November 25, 2015

Before the fluid of the middle ear drains and sound waves penetrate for the first time, the inner ear cells of newborn rodents practice for their big debut. Researchers at Johns Hopkins report they have figured out the molecular ...

How cells 'climb' to build fruit fly tracheas

November 25, 2015

Fruit fly windpipes are much more like human blood vessels than the entryway to human lungs. To create that intricate network, fly embryonic cells must sprout "fingers" and crawl into place. Now researchers at The Johns Hopkins ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.