Jasmonate, Salicylate, and Benzoate in Insect Eggs
Jasmonic acid (JA) and salicylic acid (SA) are key molecules in the initiation of plant defensive responses to attack by herbivores and pathogens, respectively. Our previous work has shown that JA occurs at high concentrations in eggs and neonates of lepidopteran species. Here, we extend our analyses to eggs of 15 non-lepidopteran insect species spanning eight orders, again screening for JA, but also including SA and one of its metabolic precursors, benzoic acid. We detected all three compounds in eggs of almost all the species examined. Moreover, concentrations of these compounds were variable across species, suggesting that species accumulate and/or utilize the compounds differently. Eggs of the fruit-feeding fly Rhagoletis pomonella contained the greatest concentrations of all three compounds, which appear to be common in fruit. The presence of these plant-derived compounds in eggs may serve defensive or other functions for insects, and could conceivably trigger plant defensive responses after oviposition.
KeywordsBenzoic acid Jasmonic acid Salicylic acid Phytohormone Plant defenses
We thank J. Saunders, A. Conrad, and C. Wagner for logistical support, E. Bogus for technical assistance, S. Colazza (University of Palermo), J. Lundgren, and C. Nielson (USDA, Brookings, SD, USA), R. Ruiz and O. Forrester (USDA, Edinburg, TX, USA), B. Thorne and N. Breisch (University of Maryland), S. Olsson and C. Smith (NY State Ag. Research Station, Geneva, NY, USA), and C. Delphia, M. Frazier, and O. Thompson (Penn State) for the eggs. The Hessian fly colony was established with the assistance of N. Bosque-Perez and D. Schotzko (University of Idaho). We thank M. Mescher and J. Runyon for comments on the manuscript. The project was supported by the USDA National Research Initiative (#2002-35302-12375), the David and Lucile Packard Foundation, and the Beckman Foundation.
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