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How Parasitic Plants Use the Language of RNA on Their Victims

A green strangleweed tendril tightens its grip on the stem of a sugar beet plant. Researchers have found that there's a vast exchange of genetic information between strangleweed plants and their hosts. / Virginia Tech

Parasitic weeds use an RNA-based "language" to communicate with their host plants — perhaps to get them to lower their defenses, scientists report.

"The discovery of this novel form of inter-organism communication shows that this is happening a lot more than anyone previously realized," Jim Westwood, a plant scientist at Virginia Tech, said Thursday in a news release. "Now that we have found that they are sharing all this information, the next question is, 'What exactly are they telling each other?'"

By interpreting the genetic language correctly, scientists may be able to disrupt the communication channels and help food-producing plants protect themselves from nutrient-sucking pests.

Time-Lapse: Attack of the Parasitic Plant 2:34

The communication involves the exchange of messenger RNA molecules. Messenger RNA, or mRNA, is typically used within living cells to pass along the genetic instructions from DNA for producing proteins.

For years, Westwood has been studying how RNA molecules are transported between plants during parasite-host interactions. In this week's issue of the journal Science, he and his colleagues describe their studies of RNA-based communication involving a type of parasitic plant known as dodder or strangleweed.

Strangleweed plants wrap their tendrils around the stems of other plants, and then insert appendages known as haustoria to suck moisture and nutrients from their hosts. In the Virginia Tech experiment, the researchers studied strangleweed's chemical exchanges with tomato plants as well as a widely studied mustard plant known as Arabidopsis.

They found that thousands of types of mRNA molecules were exchanged between the strangleweed plants and the hosts as the parasites tightened their grip.

Watch a parasitic weed 'sniff out' its prey

"We can only speculate about the importance of large-scale mRNA movement between individuals of different species," the researchers wrote. A wide variety of plants are known to be capable of mounting chemical defenses to fend off parasites — so one possibility is that the strangleweed may be telling the hosts to lower those defenses.

If that's the case, Westwood said mRNA could turn into an "Achilles' heel for parasites." Understanding the language of plants could well open up a new frontier for increasing crop yields worldwide.

"Parasitic plants such as witchweed and broomrape are serious problems for legumes and other crops that help feed some of the poorest regions in Africa and elsewhere," Julie Scholes, a professor at the University of Sheffield, observed in Virginia Tech's news release. "In addition to shedding new light on host-parasite communication, Westwood's findings have exciting implications for the design of novel control strategies based on disrupting the mRNA information that the parasite uses to reprogram the host."

In addition to Westwood, the authors of "Genomic-Scale Exchange of mRNA Between a Parasitic Plant and Its Hosts" include Gunjune Kim, Megan LeBlanc, Eric Wafula and Claude dePamphilis.