A bit touchy: Plants' insect defenses activated by touch

Apr 09, 2012
Plant growth is affected by touch. Arabidopsis plants that were touched several times each day (right) grew shorter stems than those that were untouched (left). Rice University biologists found that this growth response is controlled by a plant hormone that protects plants from insects and fungal infections. Credit: Wassim Chehab/Rice University

A new study by Rice University scientists reveals that plants can use the sense of touch to fight off fungal infections and insects. The study, which will be published in the April 24 issue of Current Biology, finds that plant defenses are enhanced when plants are touched.

"From previous studies, we knew that change their growth in response to touch but we didn't know how these growth changes were activated," said Wassim Chehab, a faculty fellow in Rice's Department of Biochemistry and Cell Biology and lead author of the new study. "We used a widely studied plant, Arabidopsis thaliana, to test the idea that the touch-induced growth was regulated by a called jasmonate."

Jasmonate plays a critical role in initiating against plant-eating insects. When jasmonate levels go up, the plant increases production of that give herbivores an upset stomach. Jasmonate defenses, which also protect against some , are employed by virtually all plants, including tomatoes, rice and corn. The new study provides the first evidence that these defenses are triggered when plants are touched. In the study, students touched the plants in a laboratory, but the researchers say the touch-induced response could also be activated by animals, including insects, and wind.

Rice University biologists found that plant defenses against leaf-eating herbivores, like this cabbage looper caterpillar, are activated by the plant's sense of touch. CREDIT: Tommy LaVergne/Rice University

"Plants can't move, so it makes sense for them to have a highly developed to react quickly to changes in their environment," said study co-author Janet Braam, professor and chair of Rice's Department of Biochemistry and Cell Biology.

The famed uses its sense of touch to rapidly close and trap insects. But in prior research at Rice, Braam and her colleagues showed that Arabidopsis was also extremely responsive to touch. In 2000, her lab used tools of biotechnology to produce a plant that glowed with light wherever it was touched. They also showed that Arabidopsis plants that were touched regularly grew much shorter and slower -- much like trees exposed to a windy coastline will grow short and bent.

"In this new work, we show that jasmonate mediates this growth response in Arabidopsis," Braam said. "Our experiments show that plants that are repeatedly touched maintain high levels of jasmonate and therefore have enhanced insect and fungal tolerance. In addition, we found that eliminating key genes required for jasmonate production results in the inability of plants to grow shorter and slower when touched."

Braam and Chehab also found that plants that were touched often, and consequently had high levels of jasmonate, were more resistant to fungal and insect attacks.

Chehab said plants do not base their production of jasmonate on a single source of information.

"There are multiple signals that can influence the jasmonate response," Chehab said. "Touch is one, but we also recently found that this response can be mediated by the plant's internal clock, or circadian rhythm. It's a complicated picture, but by piecing it together, we get a clearer understanding of plant pest resistance."

Explore further: Rare new species of plant: Stachys caroliniana

Related Stories

Researchers JAZ(zed) about plant resistance discovery

Jul 18, 2007

The mystery of how a major plant hormone works to defend plants against invaders has been revealed, thanks to collaborative research efforts by Michigan State University and Washington State University.

Anti-cancer flower power

Aug 25, 2008

Could a substance from the jasmine flower hold the key to an effective new therapy to treat cancer? Prof. Eliezer Flescher of The Sackler Faculty of Medicine, Tel Aviv University thinks so. He and his colleagues have developed ...

Circadian clock controls plant growth hormone

Aug 13, 2007

The plant growth hormone auxin is controlled by circadian rhythms within the plant, UC Davis researchers have found. The discovery explains how plants can time their growth to take advantage of resources such ...

Recommended for you

Rare new species of plant: Stachys caroliniana

Nov 21, 2014

The exclusive club of explorers who have discovered a rare new species of life isn't restricted to globetrotters traveling to remote locations like the Amazon rainforests, Madagascar or the woodlands of the ...

Mysterious glowworm found in Peruvian rainforest

Nov 21, 2014

(Phys.org) —Wildlife photographer Jeff Cremer has discovered what appears to be a new type of bioluminescent larvae. He told members of the press recently that he was walking near a camp in the Peruvian ...

The unknown crocodiles

Nov 21, 2014

Just a few years ago, crocodilians – crocodiles, alligators and their less-known relatives – were mostly thought of as slow, lazy, and outright stupid animals. You may have thought something like that ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.