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Reversing gene foils virus.

Viruses cause diseases by invading the cells of susceptible plants and hijacking the cell reproductive mechanism. They take over the cell functions designed to replicate plant DNA and convert it to production of new virus particles.

According to University of Missouri-Columbia biochemist June Bourque, many of the most serious plant diseases are caused by viruses, but traditional control methods don't always work. "Pesticides control insects that spread viruses. But more emphasis is now placed on breeding resistant crop varieties, because we are more aware of the potential harmful effects of insecticides on the environment. Breeding crop plants for disease resistance has had limited success. Often, appropriate genes have not been found in the crop or a closely related species. Therefore, traditional plant breeding techniques of crossing and selection won't work."

Bourque aims to induce plant resistance to viruses by isolating a small, but essential, fragment of viral RNA, rearranging it so that it interferes with expression of the virus gene and incorporating it into the plant DNA. RNA and DNA are two forms of nucleic acid, the chemical that contains the code for most of the genetic information in plants and viruses. The latter have some small RNA strands that are structurally similar to plant messenger RNAs. They function as messenger RNAs during replication of the virus within the plant cell. She plans to take one of these RNA strands from the tomato spotted wilt virus, make a complementary DNA, then reverse the direction of a portion of that DNA sequence. it then should bind to a specific region of the virus RNA and prevent it from operating normally.

The result is a double-stranded RNA fragment in the plant that can not be transformed into a protein. The virus needs this protein to replicate itself and for movement from cell to cell within the plant. "This process, in essence, inhibits the expression of certain virus genes in the plant's cells that are necessary for the invading virus to cause a disease."
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Title Annotation:plant resistance to disease
Publication:USA Today (Magazine)
Date:Jun 1, 1993
Words:331
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