Altered proteolytic and amydolytic activity in insecticide-susceptible and -resistant strains of the maize weevil, <i>Sitophilus zeamais</i>

  • L. B. Silva Setor de Entomologia, Departamento de Biologia Animal, Universidade Federal de Viçosa, Viçosa, MG 36571-000, Brazil.
  • K. V. G. Lopes Departamento de Bioquímica e Biologia Molecular, Instituto de Biotecnologia Aplicada à Agropecuária (BIOAGRO), Universidade Federal de Viçosa, Viçosa, MG 36570-000, Brazil
  • M. G. A. Oliveira Instituto Nacional de Ciência e Tecnologia em Interações Planta-Praga (INCT-IPP), Universidade Federal de Viçosa, Viçosa, MG 36570-000, Brazil
  • R. N. C. Guedes Setor de Entomologia, Departamento de Biologia Animal, Universidade Federal de Viçosa, Viçosa, MG 36571-000, Brazil. Email address: guedes@ufv.br

Abstract

Fitness cost is usually associated with insecticide resistance and may be mitigated by increased energy accumulation and mobilization. Preliminarily evidence from tests with Sitophilus zeamais Motschulsky, the maize weevil (Coleoptera: Curculionidae) suggested possible involvement of proteinases and amylases in such a phenomenon. Therefore, trypsin-like serine-proteinases, cysteine-proteinases and α-amylases were purified and characterized from an insecticide-susceptible and two insecticide-resistant strains (one with associated fitness cost [resistant cost strain], and the other without it [resistant no-cost strain]). Trypsin-like serine-proteinases were purified by aprotinin-agarose affinity chromatography, while cysteine-proteinases were purified using thiol-sepharose affinity chromatography, and the main α-amylase of each strain was purified by glycogen precipitation and ion-exchange chromatography. The activity and inhibition profile differed among strains for each group of purified enzyme. The higher levels of activity observed for trypsin-like proteinases and amylase in the resistant no-cost strain, as well as their susceptibility to inhibition provide support for the hypothesis that enhanced trypsin-like protease and α-amylase activity may be playing a major role in mitigating fitness costs associated with insecticide resistance. In contrast, enhanced cysteine-proteinase activity is likely to play only a secondary role, if any, in mitigating the costs usually associated with insecticide resistance.

Keywords: Fitness cost mitigation, Insecticide resistance, Digestive enzymes, Amylases, Proteinases.
Veröffentlicht
2010-09-20
Rubrik
Section: Residual Insecticides - Synthetic and Botanical