Protease inhibitory, insecticidal and deterrent effects of the trypsin-inhibitor benzamidine on the velvetbean caterpillar in soybean.

Anderson M Pilon,Glaúcia Cordeiro,Carolina R Silva,Maria Goreti A Oliveira,Wellington G Campos,Camila R Silva

doi:10.1590/0001-3765201820180159

Abstract

The recognition of protease inhibitors with insecticidal activity is important as a basis for the development of mimetic peptides with potential use as biorational insecticides. We sprayed benzamidine on soybean plants and assessed whether this potent synthetic trypsin-inhibitor has protease inhibitory, insecticidal and deterrent effects on the velvetbean caterpillar Anticarsia gemmatalis Hübner (Lepidoptera: Erebidae). Activity of trypsin inhibition in soybean leaves was increased and total proteolytic activity in the midgut extract from larvae fed on these leaves was reduced by benzamidine. Different concentrations of benzamidine sprayed on the plant caused approximately 50 % of larval mortality, and larval choice and moth preference and oviposition were all negatively affected. Low concentrations of benzamidine increased mortality and hindered insect choice and oviposition as well as higher doses. Since many synthetic protease inhibitors are usually expensive, small doses of benzamidine may be effective to protect soybean against A. gemmatalis attack. Our results highlight the potential of synthetic protease inhibitors for insecticidal and deterrent purposes in insect pest management.

Highlights

To counter herbivory, plants have evolved morphological traits, secondary metabolites gut and inhibit their activity, thereby reduce protein digestion, resulting in the shortage of amino acids for the herbivore (War et al 2012)
Ingestion of potent synthetic Proteinase inhibitors (PIs) can be lethal for insects (Moreira et al 2011), even though the usage of synthetic inhibitors for insecticidal purpose remains poorly explored
Compounds derived from lipoxygenase isozymes (LOX) activity are precursors of jasmonic acid, which would in turn activate transcription of genes encoding for PIs (Farmer and Ryan 1992)

Summary

Introduction

Plants have evolved morphological traits, secondary metabolites gut and inhibit their activity, thereby reduce protein digestion, resulting in the shortage of amino acids for the herbivore (War et al 2012). We sprayed the synthetic PI benzamidine on a soybean line that lacks LOX and KTI in seeds and assessed whether this method have protease inhibitory, insecticidal and deterrent effects on the velvetbean caterpillar. The trypsin activity in the presence of PIs in soybean leaves was determined using 50 μL leaf extract, 500 μL

Results

Conclusion