Eating the evidence? Manduca sexta larvae can not disrupt specific jasmonate induction in Nicotiana attenuata by rapid consumption

Abstract

As feeding by the tobacco specialist Manduca sexta L. is known to result in significantly higher jasmonate (JA) concentrations in Nicotiana plants than do mechanical simulations of the larval damage, we investigated whether M. sexta, which is known to rapidly consume large quantities of leaf material, can impair this "recognition" response by consuming the leaf tissue before it can respond with amplified JA levels. We report that oral secretions (OS) from M. sexta, but not from the cabbage specialist Pieris rapae, amplified the wound-induced JA response of Nicotiana attenuata Torr. Ex Wats., regardless of larval diet, instar and molting stage, and were still active after boiling and when diluted to 1/1000. The largest JA response occurred within 40 min in tissues adjacent to the OS application site. When 3 mm of leaf tissue immediately adjacent to the OS application site was excised within 40 s, the signal that elicits JA amplification was found to travel rapidly into the leaf, beyond the mandibular reach of the larvae. We conclude that M. sexta is not able to consume the evidence of feeding activity.

Nitrogen Supply Influences Herbivore-Induced Direct and Indirect Defenses and Transcriptional Responses in Nicotiana attenuata

“…As is consistent with early studies (Halitschke et al, 2000;Schittko et al, 2000), application of M. sexta OS to puncture wounds in N. attenuata leaves caused a transient JA burst in both HN and LN treatments, which reached maximum values at 30 min (Fig. 2).…”

Molecular Interactions between the Specialist HerbivoreManduca sexta (Lepidoptera, Sphingidae) and Its Natural Host Nicotiana attenuata. III. Fatty Acid-Amino Acid Conjugates in Herbivore Oral Secretions Are Necessary and Sufficient for Herbivore-Specific Plant Responses

“…As previously described (Kahl et al, 2000;Schittko et al, 2000), application of M. sexta R to puncture wounds on N. attenuata leaves transiently elicits higher JA concentrations than does the addition of water to identical puncture wounds (Fig. 2B, ANOVA F 8, 26 ϭ 14.551, P Ͻ 0.0001).…”

“…These results demonstrate that other inductionmechanisms than a simple supply of FA as substrate for endogenous JA biosynthesis must account for the response activation processes in the N. attenuata-M. sexta system. The JA response is known to be very sensitive to M. sexta R, which retain their activity even when diluted to 1/1,000 with water (Schittko et al, 2000). This sensitivity also argues against a substrate supply mechanism, because the quantity of FAs delivered to a leaf as FACs in this highly diluted, but still active R is not sufficient to supply the quantity of fatty acid substrate required for the observed endogenous JA burst.…”

“…elicits responses clearly different from those induced by careful mechanical simulation of larval feeding. The wound-induced increase in jasmonic acid (JA) levels is amplified by herbivore feeding and by application of larval oral secretions and regurgitant (R) to mechanical wounds (McCloud and Baldwin, 1997;Schittko et al, 2000), whereas the wound-induced increase in nicotine-accumulation, which strongly correlates with wound-induced JA-levels (Baldwin et al, 1994a(Baldwin et al, , 1997 is suppressed (Baldwin, 1988;McCloud and Baldwin, 1997) by an ethylene-burst released by the plant after herbivore attack (Kahl et al, 2000). Furthermore, herbivore feeding and R application to plant wounds are also known to induce the release of several mono-and sesquiterpenes in N. attenuata (Halitschke et al, 2000;Kahl et al, 2000), which, in turn, are thought to function as an indirect defense, guiding parasitoids to feeding larvae.…”

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

“…feeding. Pure OS collected from fourth to fifth instar M. sexta larvae from the Jena colony fed on WT plants was diluted 1:5 with distilled water before use; even 1000-fold diluted OS is still sufficient to cause most OS-elicited responses (Schittko et al, 2000). For field-grown plants, a similar, mature, non-senescent leaf was chosen from each plant; for glasshouse-grown plants, the two adjacent older leaves (nodes +1, +2) to the leaf undergoing a source-sink transition (node 0) on rosette-stage plants were used for PI and LOX2 transcript quantification, and the +2 node of a separate set of bolting plants was used for measuring headspace volatiles.…”