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PLoS Biol

Title:		Nicotine's defensive function in nature
Author(s):		Steppuhn A; Gase K; Krock B; Halitschke R; Baldwin IT;
Address:		"Department of Molecular Ecology, Max Planck Institute for Chemical Ecology, Jena, Germany"
Journal Title:		PLoS Biol
Year:		2004
Volume:		20040817
Issue:		8
Page Number:		E217 -
DOI:		10.1371/journal.pbio.0020217
ISSN/ISBN:		1545-7885 (Electronic) 1544-9173 (Print) 1544-9173 (Linking)
Abstract:		"Plants produce metabolites that directly decrease herbivore performance, and as a consequence, herbivores are selected for resistance to these metabolites. To determine whether these metabolites actually function as defenses requires measuring the performance of plants that are altered only in the production of a certain metabolite. To date, the defensive value of most plant resistance traits has not been demonstrated in nature. We transformed native tobacco(Nicotiana attenuata) with a consensus fragment of its two putrescine N-methyl transferase (pmt) genes in either antisense or inverted-repeat (IRpmt) orientations. Only the latter reduced (by greater than 95%) constitutive and inducible nicotine. With D(4)-nicotinic acid (NA), we demonstrate that silencing pmt inhibits nicotine production, while the excess NA dimerizes to form anatabine. Larvae of the nicotine-adapted herbivore Manduca sexta (tobacco hornworm) grew faster and, like the beetle Diabrotica undecimpunctata, preferred IRpmt plants in choice tests. When planted in their native habitat, IRpmt plants were attacked more frequently and, compared to wild-type plants, lost 3-fold more leaf area from a variety of native herbivores, of which the beet armyworm, Spodoptera exigua, and Trimerotropis spp. grasshoppers caused the most damage. These results provide strong evidence that nicotine functions as an efficient defense in nature and highlights the value of transgenic techniques for ecological research"
Keywords:		"Animals Blotting, Southern DNA, Bacterial/chemistry Dimerization Ecology Ethidium/pharmacology *Gene Expression Regulation, Plant Gene Silencing Genetic Vectors Manduca Methyltransferases/metabolism Models, Genetic Molecular Sequence Data Niacin/chemistry;"
Notes:		"MedlineSteppuhn, Anke Gase, Klaus Krock, Bernd Halitschke, Rayko Baldwin, Ian T eng Research Support, Non-U.S. Gov't 2004/08/18 PLoS Biol. 2004 Aug; 2(8):E217. doi: 10.1371/journal.pbio.0020217. Epub 2004 Aug 17"