LIMITED EFFECT OF REACTIVEOXYGEN SPECIES ON THECOMPOSITION OF SUSCEPTIBLEESSENTIAL AMINO ACIDS IN THEMIDGUTS OF Lymantria DisparCATERPILLARS

摘要

The essential amino acids (EAAs) arginine, histidine, lysine, andmethionine, as well as cysteine (semiessential), are believed to be susceptibleto reactions with reactive oxygen species (ROS) in biological systems. Thedecreased availability of these EAAs could harm insect nutrition, sinceseveral of them can also be limiting for protein synthesis. However, no invivo studies have quantified the effect of ROS in the midguts of insectherbivores on EAA composition. This study examined the associationbetween elevated levels of ROS in the midgut fiuid of Lymantria disparcaterpillars and the compositions of EAAs (protein-bound + protein-free)in their midgut fiuid and frass. Contrary to expectation, the compositionsof EAAs were not significantly decreased by ROS in midgut fiuid ex vivowhen incubated with phenolic compounds. Two in vivo comparisons of low- and high-ROS-producing leaves also showed similar results: there wereno significant decreases in the compositions of EAAs in the midgut fiuidsand/or frass of larvae with elevated levels of ROS in their midguts. Inaddition, waste nitrogen excretion was not significantly increased fromlarvae on high-ROS treatments, as would be expected if ROS producedunbalanced EAA compositions. These results suggest that L. dispar larvaeare able to tolerate elevated levels of ROS in their midguts withoutnutritionally significant changes in the compositions of susceptible EAAsin their food.