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Attacked, tobacco plants call their enemy’s enemy

Aug. 27, 2010
Courtesy of Science
and World Science staff

When cater­pil­lars nib­ble on wild to­bac­co plants, the leafy vic­tims emit a dis­tress sig­nal that brings the ver­mins’ en­e­my fly­ing in to the res­cue, a new study has found.

Cat­er­pil­lar eggs, a young cat­er­pil­lar and a pred­a­to­ry bug that has just ar­rived, all are on the bot­tom of this to­bac­co leaf. (Cred­it: Max Planck In­sti­tute for Chem­i­cal Ecol­o­gy/Danny Kessler)

Damaged plants promp­tly give off chem­i­cals known as green leaf volatiles, or GLVs. If you’ve smelled freshly cut grass, you’ve smelled GLVs.

Re­search­ers found that these GLVs can send a spe­cif­ic sig­nal, at least in the case of the wild to­bac­co plant, Ni­co­ti­a­na at­ten­u­ata.

When the plant is at­tacked by to­bac­co horn­worm cater­pil­lars, Man­d­uca sexta, the cater­pil­lars’ sa­li­va causes a change in the GLVs that the plants pro­duce. 

This mod­i­fied cock­tail at­tracts pred­a­to­ry in­sects called Geo­coris, which prey on horn­worm eggs and young lar­vae, thus pro­tect­ing the plant.

More re­search will be needed to fig­ure out ex­actly how the mo­le­cules in the cat­er­pil­lar sa­li­va cause this change in the GLVs, the re­search­ers say.

The stu­dy, pub­lished in the Aug. 27 is­sue of the research jour­nal Sci­ence, was con­ducted by Silke All­mann of the Swam­mer­dam In­sti­tute for Life Sci­ences in Am­ster­dam, the Neth­er­lands and the Max Planck In­sti­tute for Chem­i­cal Ecol­o­gy in Je­na, Ger­ma­ny and Ian Bald­win of the Max Planck In­sti­tute for Chem­i­cal Ecol­o­gy in Je­na.

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When caterpillars start nibbling on wild tobacco plants, the leafy victims emit an “SOS” signal that brings the vermins’ enemy flying in to the rescue, a new study has found. The compounds that plants give off immediately upon damage are known as “green leaf volatiles,” or “GLVs.” If you’ve smelled freshly cut grass, you’ve smelled GLVs. Researchers found that these GLVs can send a specific signal, at least in the case of the wild tobacco plant, Nicotiana attenuata. When the plant is attacked by tobacco hornworm caterpillars, Manduca sexta, the caterpillars’ saliva causes a chemical change in the GLV compounds the plants produce. This modified cocktail attracts predatory insects called Geocoris, which prey on hornworm eggs and young larvae, thus protecting the plant. More research will be needed to figure out exactly how the molecules in the caterpillar saliva cause this change in the GLVs, the researchers say. The study, published in the 27 August issue of the journal Science, was conducted by Silke Allmann of the Swammerdam Institute for Life Sciences in Amsterdam, the Netherlands and the Max Planck Institute for Chemical Ecology in Jena, Germany and Ian Baldwin of the Max Planck Institute for Chemical Ecology in Jena.