Three genes are essential for the virus to replicate. Each of these carries the code for a piece of RNA, a kind of genetic material similar to DNA.
RNA can be inactivated when a matching strand binds to it. Knowing the structure of the gene that makes the RNA allows researchers to create matching genes.
This is exactly what Zhang's team did. They created 'matching' genes for the three crucial strands of RNA and inserted these into cassava plants.
They expected that whenever the modified cassava cells were infected by the virus, the RNA made by the inserted genes would find and stick to the viral RNA, inactivating it and preventing the virus from replicating.
In tests, when the plants were exposed to small amounts of the virus, the researchers could see no signs of disease, suggesting their theory was verified.
With higher doses of the virus, symptoms were reduced.
Zhan's team published their findings in the July issue of Plant Biotechnology Journal.
Reference: Plant Biotechnology Journal 3, 385 (2005)Read more about GM crops in SciDev.Net's GM crops dossier.