Molecular Ecology (2008) 17, 3717–3732 doi: 10.1111/j.1365-294X.2008.03862.x © 2008 The Authors Journal compilation © 2008 Blackwell Publishing Ltd Blackwell Publishing Ltd Silencing jasmonate signalling and jasmonate-mediated defences reveals different survival strategies between two Nicotiana attenuata accessions ANKE STEPPUHN, MEREDITH C. SCHUMAN and IAN T. BALDWIN Department of Molecular Ecology, Max Planck Institute for Chemical Ecology, Hans Knöll Str. 8, D-07745 Jena, Germany Abstract To determine the impact of genotypic variation in secondary metabolite production on antiherbivore resistance and plant fitness, we genetically silenced biosynthetic genes for nicotine, trypsin proteinase inhibitors (TPI), and jasmonate ( JA) production in two accessions of Nicotiana attenuata: one from Utah (UT) which responds to herbivory with JA-induced nicotine and TPI production, and one from Arizona (AZ) which is TPI-deficient but also produces JA-induced nicotine. Transient silencing of JA biosynthesis increased Manduca sexta larval growth on wild type (WT) plants of both accessions, but not on TPI-deficient UT or nicotine-deficient AZ lines, demonstrating that JA-mediated resistance to M. sexta requires TPIs in the UT and nicotine in the naturally TPI-deficient AZ accession. When transplanted into a native UT population, AZ and UT plants, rendered equally able or unable to produce nicotine and TPIs by stable transformation, received significantly different levels of her- bivory. Both accessions differed in their resistance depending on the type of herbivores: resistance to rare, voracious herbivores (Saltatoria and Mammalia) was greater in AZ than UT lines, and dependent on nicotine production, while resistance to small, abundant her- bivores (Coleoptera and Thysanoptera) was greater in UT lines, and dependent on TPI production. AZ lines produced more flowers and seed capsules than UT lines independently of TPI production costs. This fitness advantage was lost when accessions did not produce nicotine. We conclude that these two accessions have developed different survival strategies and thus differ in the cost-benefit functions of their JA-mediated defences. Keywords: costs of defences, genotypic plasticity, nicotine, plant defence, secondary metabolites, trypsin proteinase inhibitors Received 20 May 2008; revision accepted 29 May 2008 Introduction Plants persist in a world full of herbivores, relying on survival strategies which include toxic or antidigestive direct defences, indirect defences that attract predators of herbivores, and tolerance mechanisms. Variation in these survival strategies may itself be adaptive, and comprises both plasticity of a single genotype, and polymorphisms among individuals and populations. Plasticity, exemplified by the inducibility of many plant defenses, allows individual plants to adapt to changing environments (Agrawal 2001). Polymorphisms in antiherbivore resistance traits may result from varying selection pressures among populations, or from diversifying selection, which may constrain herbivores’ ability to adapt to plant defences (Meyers et al. 2005). Even single genotypes usually produce a diversity of defence traits; individual traits may positively and negatively affect each other’s functions. The wild tobacco Nicotiana attenuata produces diverse secondary metabolites, many of which are elicited via the jasmonate (JA)-signalling pathway (Halitschke & Baldwin 2003; Roda et al. 2004). Accessions of N. attenuata vary markedly in their production of antiherbivore defences (Glawe et al. 2003). Here, we describe an experimental approach to parse the contribution of known JA-mediated defence traits to herbivore resistance and fitness in two of Correspondence: Ian T. Baldwin, Fax: 49-(0)3641-571102; E-mail: baldwin@ice.mpg.de A. Steppuhn and M. C. Schuman contributed equally to this work.