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Proc Natl Acad Sci U S A

Title:		"Natural history-driven, plant-mediated RNAi-based study reveals CYP6B46's role in a nicotine-mediated antipredator herbivore defense"
Author(s):		Kumar P; Pandit SS; Steppuhn A; Baldwin IT;
Address:		"Department of Molecular Ecology, Max-Planck-Institute for Chemical Ecology, 07745 Jena, Germany"
Journal Title:		Proc Natl Acad Sci U S A
Year:		2014
Volume:		20131230
Issue:		4
Page Number:		1245 - 1252
DOI:		10.1073/pnas.1314848111
ISSN/ISBN:		1091-6490 (Electronic) 0027-8424 (Print) 0027-8424 (Linking)
Abstract:		"Manduca sexta (Ms) larvae are known to efficiently excrete ingested nicotine when feeding on their nicotine-producing native hostplant, Nicotiana attenuata. Here we describe how ingested nicotine is co-opted for larval defense by a unique mechanism. Plant-mediated RNAi was used to silence a midgut-expressed, nicotine-induced cytochrome P450 6B46 (CYP6B46) in larvae consuming transgenic N. attenuata plants producing MsCYP6B46 dsRNA. These and transgenic nicotine-deficient plants were planted into native habitats to study the phenotypes of larvae feeding on these plants and the behavior of their predators. The attack-behavior of a native wolf spider (Camptocosa parallela), a major nocturnal predator, provided the key to understanding MsCYP6B46's function: spiders clearly preferred CYP6B46-silenced larvae, just as they had preferred larvae fed nicotine-deficient plants. MsCYP6B46 redirects a small amount (0.65%) of ingested nicotine from the midgut into hemolymph, from which nicotine is exhaled through the spiracles as an antispider signal. CYP6B46-silenced larvae were more susceptible to spider-attack because they exhaled less nicotine because of lower hemolymph nicotine concentrations. CYP6B46-silenced larvae were impaired in distributing ingested nicotine from midgut to hemolymph, but not in the clearing of hemolymph nicotine or in the exhalation of nicotine from hemolymph. MsCYP6B46 could be a component of a previously hypothesized pump that converts nicotine to a short-lived, transportable, metabolite. Other predators, big-eyed bugs, and antlion larvae were insensitive to this defense. Thus, chemical defenses, too toxic to sequester, can be repurposed for defensive functions through respiration as a form of defensive halitosis, and predators can assist the functional elucidation of herbivore genes"
Keywords:		Animals Cytochrome P-450 Enzyme System/*genetics Gene Silencing *Herbivory Nicotine/*pharmacology Plants/*genetics *Predatory Behavior *RNA Interference Spiders Coyote tobacco Lepidoptera alkaloid reverse genetics tobacco hornworm;
Notes:		"MedlineKumar, Pavan Pandit, Sagar S Steppuhn, Anke Baldwin, Ian T eng 293926/ERC_/European Research Council/International Research Support, Non-U.S. Gov't 2014/01/01 Proc Natl Acad Sci U S A. 2014 Jan 28; 111(4):1245-52. doi: 10.1073/pnas.1314848111. Epub 2013 Dec 30"