Plant parasite shows vulnerability

Dodder vines are parasites that live on other plants. Most species have abandoned photosynthesis and regular roots, and live by plumbing themselves into a host plant’s vascular system (phloem) to suck up water and other nutrients. A new study from Neelima Sinha’s group shows that dodder also take up RNA molecules that travel a surprisingly long way in the dodder plant — and could be manipulated to kill the parasite.

RNA (ribonucleic acid) molecules are widely used as signaling molecules in plants — an area pioneered at UC Davis by Bill Lucas’ lab. RNA can coordinate growth in different parts of the plant, affect petal color and neutralize viruses through a process called RNA interference, where a piece of RNA attaches to a matching piece of DNA and blocks it. (The 2006 Nobel Prize for Physiology and Medicine was awarded for discovering RNA interference, but in animals, upsetting some plant biologists).

Rakefet David Schwartz, Steven Runo, Brad Townsley, Jesse Machuka and Sinha studied dodder growing on tomato plants in the lab. They were able to detect tomato RNA molecules in the dodder plant up to 30 cm (about a foot) from the site of attachment.

Tapping into these signalling molecules might be a way for the dodder to “get in sync” with its host, Sinha told Science News. But it could also open a way to use RNA interference to attack the dodder plant, according to other experts.

The original article is to be published in an upcoming issue of the journal New Phytologist. It is already available online.

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