Jasmonate and ppHsystemin Regulate Key Malonylation Steps in the Biosynthesis of 17-Hydroxygeranyllinalool Diterpene Glycosides, an Abundant and Effective Direct Defense against Herbivores in<i>Nicotiana attenuata</i>

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Natural variation can be extremely useful in unraveling the determinants of phenotypic trait evolution but has rarely been analyzed with unbiased metabolic profiling to understand how its effects are organized at the level of biochemical pathways. Native populations of Nicotiana attenuata, a wild tobacco species, have been shown to be highly genetically diverse for traits important for their interactions with insects. To resolve the chemodiversity existing in these populations, we developed a metabolomics and computational pipeline to annotate leaf metabolic responses to Manduca sexta herbivory. We selected seeds from 43 accessions of different populations from the southwestern United Statesincluding the well-characterized Utah 30th generation inbred accession-and grew 183 plants in the glasshouse for standardized herbivory elicitation. Metabolic profiles were generated from elicited leaves of each plant using a high-throughput ultra HPLC (UHPLC)-quadrupole TOFMS (qTOFMS) method, processed to systematically infer covariation patterns among biochemically related metabolites, as well as unknown ones, and finally assembled to map natural variation. Navigating this map revealed metabolic branch-specific variations that surprisingly only partly overlapped with jasmonate accumulation polymorphisms and deviated from canonical jasmonate signaling. Fragmentation analysis via indiscriminant tandem mass spectrometry (idMS/MS) was conducted with 10 accessions that spanned a large proportion of the variance found in the complete accession dataset, and compound spectra were computationally assembled into spectral similarity networks. The biological information captured by this networking approach facilitates the mining of the mass spectral data of unknowns with high natural variation, as demonstrated by the annotation of a strongly herbivory-inducible phenolic derivative, and can guide pathway analysis.plant-insect interactions | metabolomics | mass spectrometry | natural variation E lucidating the structure of metabolites underlying complex traits and the factors that maintain their variation in natural populations are important challenges in plant ecological studies (1). Many studies have notably shown that stress-responsive pathways that produce secondary metabolites are sporadically found across different plant taxa with extensive diversification (2). This important diversification suggests that particular metabolic systems have been recruited through natural selection when the set of compounds that they produce address specific ecological needs. Interactions with insects are important selection pressures that have sculpted plant metabolism, and many plant metabolites protect against herbivore attack and physical damage (3-5). The timely production of particular secondary metabolites in response to insect attack benefits plants by decreasing the costs of constitutive metabolite production. Trade-offs between defense metabolite productions and the intrinsic growth-related functions of central metabolic pathways likely prov...

Section: Resultsmentioning

confidence: 95%

Section: Significancementioning

confidence: 99%

Navigating natural variation in herbivory-induced secondary metabolism in coyote tobacco populations using MS/MS structural analysis

Baldwin

Gaquerel

2015

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“…We demonstrate that Empoasca leafhopper feeding on N. attenuata plants is independent of the accumulation of the three major classes of insecticidal compounds in N. attenuata (i.e., nicotine, trypsin PIs, and DTGs). The biosynthesis of these molecules is regulated by JA signaling, and they are known to have a strong influence on the herbivore community on N. attenuata in field experiments (45,46,58,59). Although the total herbivore damage on ir-pmt, ir-pi, ir-pmt/pi, and ir-ggpps plants was significantly higher than on control plants (Fig.…”

Section: Major Defense Molecules Of N Attenuata Do Not Affect Initialmentioning

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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113

167

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).

“…Eluted compounds were detected by a Bruker MicroToF mass spectrometer (Bruker Daltronik) equipped with an ion spray source in positiveion mode. The instrument was operated with parameters according to Heiling et al (38).…”

Section: Methodsmentioning

confidence: 99%

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

Weinhold

Baldwin

2011

186

150

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