In this study, Dandekar and Escobar targeted two bacterial genes that are key to tumor formation. They used the gene-silencing technique to "turn off" those genes and prevent the galls from forming on the plants. The work was done on the tomato plant and on Arabidopsis thaliana, a small flowering plant commonly used in research.
The job of all genes is to produce proteins. Gene silencing works by interrupting or suppressing the activity of a targeted gene, preventing it from coordinating production of specific proteins. In this case, the researchers targeted the bacterial genes that cause overproduction of plant growth hormones. It is this hormonal overproduction that results in uncontrolled cell growth and gall formation.
Thus, by using the gene-silencing technique, the researchers produced genetically engineered plants that could still be infected by Agrobacterium tumefaciens but would not produce the hormones that lead to gall formation.
"Usually when you try to prevent disease, you look at stopping the bacteria or other disease-causing agents at the 'front door' and preventing them from entering the plant," said Dandekar. "Here, we're doing the opposite. We're allowing the bacteria in, then slamming the door on them."
Analytic tests indicated that there is greater than a 90 percent reduction in gall formation among the genetically engineered tomato and Arabidopsis plants. Other than the lack of galls, however, the genetically engineered plants did not look any different than their non-transgenic counterparts.
Applications for gene silencing
The researchers suggest that this gene-silencing technique will be especially useful for crops that use roots
Contact: Patricia Bailey
University of California - Davis