Binding targets of termiticidal lectins from the bark and leaf of Myracrodruon urundeuva in the gut of Nasutitermes corniger workers

Abstract

Lectins, carbohydrate-binding proteins, from the bark (MuBL) and leaf (MuLL) of Myracrodruon urundeuva are termiticidal agents against Nasutitermes corniger workers and have been shown to induce oxidative stress and cell death in the midgut of these insects. In this study, we investigated the binding targets of MuBL and MuLL in the gut of N. corniger workers by determining the effects of these lectins on the activity of digestive enzymes. In addition, we used mass spectrometry to identify peptides from gut proteins that adsorbed to MuBL-Sepharose and MuLL-Sepharose columns. Exoglucanase activity was neutralized in the presence of MuBL and stimulated by MuLL. α-l-Arabinofuranosidase activity was not affected by MuBL but was inhibited by MuLL. Both lectins stimulated α-amylase activity and inhibited protease and trypsin-like activities. Peptides with homology to apolipophorin, trypsin-like enzyme, and ABC transporter substrate-binding protein were detected from proteins that adsorbed to MuBL-Sepharose, while peptides from proteins that bound to MuLL-Sepharose shared homology with apolipophorin. This study revealed that digestive enzymes and transport proteins found in worker guts can be recognized by MuBL and MuLL. Thus, the mechanism of their termiticidal activity may involve changes in the digestion and absorption of nutrients. © 2018 Society of Chemical Industry.