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LIMITED EFFECT OF REACTIVE OXYGEN SPECIES ON THE COMPOSITION OF SUSCEPTIBLE ESSENTIAL AMINO ACIDS IN THE MIDGUTS OF Lymantria Dispar CATERPILLARS

Authors

  • Raymond V. Barbehenn,

    Corresponding author
    1. Michigan Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan
    • Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan
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  • Julie Niewiadomski,

    1. Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan
    2. Michigan Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan
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  • Joseph Kochmanski,

    1. Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan
    2. Michigan Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan
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  • C. Peter Constabel

    1. Centre for Forest Biology and Department of Biology, University of Victoria, Victoria, BC, Canada
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  • Grant sponsor: National Research Initiative of the USDA Cooperative State Research, Education and Extension Service; Grant numbers: 2004-35302-14840 and 2007-35302-17803.

Correspondence to: Raymond V. Barbehenn, Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109-1048. E-mail: rvb@umich.edu

Abstract

The essential amino acids (EAAs) arginine, histidine, lysine, and methionine, as well as cysteine (semiessential), are believed to be susceptible to reactions with reactive oxygen species (ROS) in biological systems. The decreased availability of these EAAs could harm insect nutrition, since several of them can also be limiting for protein synthesis. However, no in vivo studies have quantified the effect of ROS in the midguts of insect herbivores on EAA composition. This study examined the association between elevated levels of ROS in the midgut fluid of Lymantria dispar caterpillars and the compositions of EAAs (protein-bound + protein-free) in their midgut fluid and frass. Contrary to expectation, the compositions of EAAs were not significantly decreased by ROS in midgut fluid ex vivo when incubated with phenolic compounds. Two in vivo comparisons of low- and high-ROS-producing leaves also showed similar results: there were no significant decreases in the compositions of EAAs in the midgut fluids and/or frass of larvae with elevated levels of ROS in their midguts. In addition, waste nitrogen excretion was not significantly increased from larvae on high-ROS treatments, as would be expected if ROS produced unbalanced EAA compositions. These results suggest that L. dispar larvae are able to tolerate elevated levels of ROS in their midguts without nutritionally significant changes in the compositions of susceptible EAAs in their food.

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