Science & Technology - Posted by Andy Fell-UC Davis on Tuesday, July 31, 2012 10:05 - 0 Comments 
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(No Ratings Yet) Loading ...To beat ‘wiretapping’ parasite, silence RNA
By targeting the parts of the parasitic plant that penetrate the host, researchers have found a way to defeat the dodder vine, and hope to apply their findings to striga, which affects food crops in Africa. (Credit: "denseflower witchweed" by Jayesh Patil/Flickr)
UC DAVIS (US) — By attacking the spot where a parasitic vine taps into its host, plant biologists have shown how they can make plants, particularly food crops, resistant.
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The text of this article by Futurity is licensed under a Creative Commons Attribution-No Derivatives License.
Dodder vines are parasitic plants that suck water, nutrients, and information from other plants as they spread over them.
“We think that this will translate into other parasitic plants,” says Neelima Sinha, professor of plant biology at University of California, Davis, who led the project. The work was published online July 20 by the journal Plant Cell.
Sinha’s lab uses dodder as a model for more serious parasites such as Striga, which attacks the roots of maize, sorghum, and other African crops.
In earlier work, Sinha and colleagues found that when dodder taps into a host plant, it takes up RNA molecules that can act as chemical messengers in the host along with water, sugars, and other nutrients. These circulating RNA molecules act as messengers inside plants, for example coordinating growth and flowering.
The researchers wondered if they could exploit this to attack the parasite. It is possible to switch off a gene with a short piece of RNA with which it pairs. This technique is called RNA interference or RNA silencing, and it won the Nobel Prize in medicine in 2006.
To use RNA interference against dodder, the team looked for genes that could affect the parasite but not the host.
“The answer turned out to be genes I’ve worked on all my career,” Sinha says, describing a group of genes that control the activity of other genes involved in shoot and root growth.
These genes are active in both the host plant meristem (an area of active growth in roots and shoots) and in the haustoria, the junctions where the parasite penetrates the host, Sinha says.
So the researchers identified regions that were unique to the parasite, and used them to make a short DNA construct. Tobacco plants carrying this construct make short pieces of RNA that match the genes of the parasite, but not the host.
Dodder did not grow as well on the engineered plants as on control plants, Sinha says. At the same time, the dodder showed high levels of stress signals and flowered early—a reaction to stress.
The work was initiated by Steven Runo and spearheaded by Amos Alakonya, two graduate students who have now returned to Kenyatta University in Kenya, Sinha says. They hope to develop the technique to control Striga in African maize crops.
“This is the proof of concept, and now we can take it into the field,” she says.
Additional scientists from UC Davis and Kenyatta University are also authors of the paper, which was funded by the Rockefeller Foundation and the National Science Foundation.
More news from UC Davis: http://www.news.ucdavis.edu/
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