June 20,  2001

Scientists have found a natural genetic mechanism that can change the way plants protect themselves against virus attack. 

Researchers at CSIRO Plant Industry have developed a technique using 'hairpin RNA' that effectively vaccinates crop plants against viruses which cost Australia millions of dollars a year, like Barley Yellow Dwarf Virus (BYDV). 

"Just as vaccines are used to prevent human diseases, such as flu, measles, or tuberculosis, we have used gene technology to induce immunisation in plants against a virus before it attacks," says CSIRO's Dr Peter Waterhouse. 

"When the plant is invaded, it destroys the virus before it can do any damage." 

This will increase food production, but also benefit the environment as pesticides currently used to control virus-carrying insects can be reduced. 

"Scientists have the potential to target viruses that, before now, have proven to be virtually unbeatable," says Dr Waterhouse. 

Scientists have only recently pieced the puzzle together of how a plant protects itself against viral attacks. 

"When a virus attacks it uses the plant's natural mechanisms as a factory to multiply, the result being damage to the plant that can affect yield, quality or even survival," says Dr Waterhouse. 

"Barley Yellow Dwarf Virus (BYDV) is a prime example of a plant virus that can devastate crop yields and quality. In Australia lost production due to BYDV infection averages about 15 per cent in barley, 17 per cent in wheat and 25 per cent in oats. 

"For wheat alone this equates to a loss of more than eight million dollars per year," says Dr Waterhouse. 

The technique is called post-transcriptional gene silencing (PTGS) with intron-spliced 'hairpin RNA' (ihpRNA). 

"It involves inserting plant DNA that has a small, incomplete piece of virus RNA added to it. 

"That produces double stranded RNA. We called it 'hairpin' (hpRNA). 

"The plant sees the hpRNA as foreign, and activates its latent defence mechanism. This degrades the hpRNA. 

"Like a fire drill, this process is a practice run for the plant's defence mechanism, teaching it to recognise the specific sequence of the virus so, if attacked, the defence mechanism leaps into action, degrading the invading virus RNA before it can multiply. 

"The result is immunity to that specific virus." 

Dr Waterhouse says the team at CSIRO has already developed potatoes resistant to Potato Leaf Roll Virus (PLRV) using this technique. These plants have been tested in the laboratory, glasshouse and have undergone field trials. 

The research suggests that the hpRNA technique will provide a simple approach for producing reliable virus immunity that can be passed down through plant generations. 

Now that scientists know how to activate this natural mechanism, they can also use the technique to 'silence' unwanted genes like those that make allergens in nuts or pollen. 

The technique overcomes concerns raised about the use of complete viral genes because it uses only a fraction of the virus' genetic sequence and alone cannot produce protein. 

This Australian innovation has been recognised internationally with research papers detailing the technology published in Proceedings for the National Academy of Science, Nature and Molecular Plant Pathology as well as requests for technical details from hundreds of international laboratories. 

Further development of the technology has the potential to bring Australia many gains through increased yields in cereal crops, and as intellectual property. 

The project is supported by the Federal Government and growers through the Grains Research and Development Corporation, and Graingene.

CSIRO news release
N3594