Silencing the Jasmonate Cascade: Induced Plant Defenses and Insect Populations

Abstract

We transformed the native tobacco, Nicotiana attenuata, to silence its lipoxygenase, hydroperoxide lyase, and allene oxide synthase genes in order to inhibit oxylipin signaling, known to mediate the plant's direct and indirect defenses. When planted into native habitats, lipoxygenase-deficient plants were more vulnerable to N. attenuata's adapted herbivores but also attracted novel herbivore species, which fed and reproduced successfully. In addition to highlighting the value of genetically silencing plants to study ecological interactions in nature, these results show that lipoxygenase-dependent signaling determines host selection for opportunistic herbivores and that induced defenses influence herbivore community composition.

Herbivory-induced volatiles function as defenses increasing fitness of the native plant Nicotiana attenuata in nature

“…For the ‘UT’ genotype of N. attenuata used in our experiments, the induction of all HIPVs except GLVs is mediated by jasmonate signaling (Halitschke and Baldwin, 2003; Kessler et al, 2004). The ir PI line A-04-186-1 (Steppuhn and Baldwin, 2007) and ir LOX2 line A-04-52-2 (Allmann et al, 2010) have been characterized previously, and neither is affected in jasmonate signaling.…”

“…The ir PI line A-04-186-1 (Steppuhn and Baldwin, 2007) and ir LOX2 line A-04-52-2 (Allmann et al, 2010) have been characterized previously, and neither is affected in jasmonate signaling. Particularly, the emission of ( E )-α-bergamotene, the best-characterized HIPV in N. attenuata apart from GLVs (Halitschke et al, 2000; Kessler et al, 2004; Halitschke et al, 2008; Skibbe et al, 2008), does not differ significantly among the lines used (N=4 measured 24–32 hr after W+OS treatment as according to Halitschke et al (2000) and normalized as a percentage of the internal standard peak: WT, 67.9±17.1%; ir PI , 30.2±13.2%; ir LOX2 , 26.6±5.8%; hemi-ir LOX2 , 42.7±23.3%; ANOVA: F 3,12 =1.338, p=0.308). The transformation process itself does not affect plant fitness or competitive ability (Schwachtje et al, 2008), TPI production or volatile emission (Figures 1–3).…”

Functional analysis of non-ribosomal peptide synthetases (NRPSs) in Trichoderma virens reveals a polyketide synthase (PKS)/NRPS hybrid enzyme involved in the induced systemic resistance response in maize

“…production of green leaf volatiles and JA; Kessler et al, 2004;Matsui, 2006) are markers for ISR (Distefano et al, 2008). Our preliminary attempt to identify the Tex13-assembled product was not successful as we failed to determine any difference in secondary metabolite profiles between the wild-type and the Dtex13 mutant grown in the presence of roots.…”

A Pharm-Ecological Perspective of Terrestrial and Aquatic Plant-Herbivore Interactions

“…In addition to high throughput approaches, genetic modification holds great promise for predicting foraging phenotypes of free-ranging herbivores (Kessler et al, 2004;Kessler et al, 2008;Wu and Baldwin, 2009). For example, silencing of the jasmonate cascade in Nicotiana attenuata improved the performance of specialist herbivores and allowed non-adapted generalist herbivores to attack (Kessler et al, 2004).…”

“…For example, silencing of the jasmonate cascade in Nicotiana attenuata improved the performance of specialist herbivores and allowed non-adapted generalist herbivores to attack (Kessler et al, 2004). Insect transgenesis has been used to manipulate agricultural and medical insect pests (Fraser, 2012) and could also be used to observe how foraging phenotypes of herbivores are influenced by control of pharmacokinetic (e.g., detoxification enzymes) and pharmacodymanic (e.g., target receptors) mechanisms.…”