Agrobacterium-mediated transformation of Nicotiana attenuata, a model ecological expression system

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Significance When hornworm ( Manduca sexta ) larvae feed on Nicotiana attenuata plants in native habitats, more disappear at night when they feed on transgenic, nicotine-free N. attenuata plants because wolf spiders ( Camptocosa parallela ) selectively prey on nicotine-free larvae. When larvae consume nicotine-replete plants, their midgut-expressed cytochrome P450 6B46 ( CYP6B46 ) is upregulated. The larvae in which CYP6B46 is silenced by plant-mediated RNAi excrete more of their ingested nicotine. Silencing CYP6B46 impairs the mechanisms of passing ingested nicotine from the midgut to the hemolymph to be exhaled from the spiracles during spider attack. Spiders are deterred by this nicotine-rich halitosis. Thus, the CYP6B46 -silenced larvae exhale less nicotine and become ready spider prey, demonstrating that CYP6B46 functions to repurpose the normally excreted nicotine for defense.

Section: Methodsmentioning

confidence: 99%

Natural history-driven, plant-mediated RNAi-based study reveals CYP6B46 ’s role in a nicotine-mediated antipredator herbivore defense

Kumar

Pandit

Steppuhn

et al. 2013

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“…The inbred line originated from seeds collected in 1988 from a natural population at the DI Ranch in southwestern Utah. Seeds were germinated and plants were grown as described (62).…”

Section: Methodsmentioning

confidence: 99%

Empoasca leafhoppers attack wild tobacco plants in a jasmonate-dependent manner and identify jasmonate mutants in natural populations

Kallenbach

Bonaventure

Gilardoni

et al. 2012

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172

Choice of host plants by phytophagous insects is essential for their survival and reproduction. This choice involves complex behavioral responses to a variety of physical and chemical characteristics of potential plants for feeding. For insects of the order Hemiptera, these behavioral responses involve a series of steps including labial dabbing and probing using their piercing mouthparts. These initial probing and feeding attempts also elicit a rapid accumulation of phytohormones, such as jasmonic acid (JA), and the induced defense metabolites they mediate. When Nicotiana attenuata plants are rendered JA deficient by silencing the initial committed step of the JA biosynthesis pathway, they are severely attacked in nature by hemipteran leafhoppers of the genus Empoasca. By producing N. attenuata plants silenced in multiple steps of JA biosynthesis and perception and in the biosynthesis of the plant's three major classes of JA-inducible insecticidal defenses, we demonstrate that the choice of plants for feeding by Empoasca leafhoppers in both nature and the glasshouse is independent of the accumulation of major insecticidal molecules. Moreover, this choice is independent of the presence of Candidatus Phytoplasma spp. and is not associated with detectable changes in plant volatiles but instead depends on the plant´s capacity to mediate JA signaling. We exploited this trait and used Empoasca leafhoppers to reveal genetic variation in JA accumulation and signaling hidden in N. attenuata natural populations. P lants provide a variety of resources, such as food, mating and oviposition sites, and shelter for a majority of phytophagous insect species. Host-plant selection by insects involves complex behavioral responses to a variety of physical and chemical characteristics of the host plant that operate at different spatial scales and include long-range olfactory (e.g., plant-derived volatiles perceived by odor receptors) and visual (e.g., plant shape, size, and color) cues and short-range chemotactic and gustatory (e.g., surface metabolites perceived by chemoreceptors) cues (1-3). The physical and chemical characteristics of plants that insects use for host selection depend on the feeding guild and the dietary behavior (e.g., polyphagy or oligophagy) of the insect species (4). For example, Drosophila melanogaster flies (order Diptera) use a wide range of olfactory cues such as methyl-, ethyl-, and propyl esters of short-chain fatty acids generated by microorganisms growing on decaying fruit (5), whereas Drosophila sechellia flies use a specific molecule (methyl hexanoate) emitted by its exclusive food plant, Morinda citrifolia (6).

“…irLOX2/3 plants are silenced in both LOX2 and LOX3 and have dramatically lower levels of GLVs (LOX2) (32) and of the signaling molecule, JA, and its conjugates (LOX3) (32,33). Seed germination was performed as described in Krügel et al (34). All plants were grown in the glasshouse in 1-L individual pots at 26-28°C under 16 h of light supplied by Philips Sun-T Agro 400-or 600-W sodium lights.…”

Section: Methodsmentioning

confidence: 99%

Trichome-derived O -acyl sugars are a first meal for caterpillars that tags them for predation

Weinhold

Baldwin

2011

198

154

Plant glandular trichomes exude secondary metabolites with defensive functions, but these epidermal protuberances are surprisingly the first meal of Lepidopteran herbivores on Nicotiana attenuata. O-acyl sugars, the most abundant metabolite of glandular trichomes, impart a distinct volatile profile to the body and frass of larvae that feed on them. The headspace composition of Manduca sexta larvae is dominated by the branched chain aliphatic acids hydrolyzed from ingested O-acyl sugars, which waxes and wanes rapidly with trichome ingestion. In native habitats a ground-hunting predator, the omnivorous ant Pogonomyrmex rugosus, but not the big-eyed bug Geocoris spp., use these volatile aliphatic acids to locate their prey.indirect defenses | dangerous body odors