Mechanisms of organophosphate resistance in a field population of oriental migratory locust, Locusta migratoria manilensis (Meyen)

Abstract

The susceptibilities to three organophosphate (OP) insecticides (malathion, chlorpyrifos, and phoxim), responses to three metabolic synergists [triphenyl phosphate (TPP), piperonyl butoxide (PBO), and diethyl maleate (DEM)], activities of major detoxification enzymes [general esterases (ESTs), glutathione S-transferases (GSTs), and cytochrome P450 monooxygenases (P450s)], and sensitivity of the target enzyme acetylcholinesterase (AChE) were compared between a laboratory-susceptible strain (LS) and a field-resistant population (FR) of the oriental migratory locust, Locusta migratoria manilensis (Meyen). The FR was significantly resistant to malathion (57.5-fold), but marginally resistant to chlorpyrifos (5.4) and phoxim (2.9). The malathion resistance of the FR was significantly diminished by TPP (synergism ratio: 16.2) and DEM (3.3), but was unchanged by PBO. In contrast, none of these synergists significantly affected the toxicity of malathion in the LS. Biochemical studies indicated that EST and GST activities in the FR were 2.1- to 3.2-fold and 1.2- to 2.0-fold, respectively, higher than those in the LS, but there was no significant difference in P450 activity between the LS and FR. Furthermore, AChE from the FR showed 4.0-fold higher activity but was 3.2-, 2.2-, and 1.1-fold less sensitive to inhibition by malaoxon, chlorpyrifos-oxon, and phoxim, respectively, than that from the LS. All these results clearly indicated that the observed malathion resistance in the FR was conferred by multiple mechanisms, including increased detoxification by ESTs and GSTs, and increased activity and reduced sensitivity of AChE to OP inhibition.

Study on Resistance of Culex pipiens (Diptera: Culicidae) Populations to Fenitrothion in Northern Tunisia

“…This confirms the hypothesis that somes esterases, GSTs, and cytochrome P450 enzymes may be insensitive to the action of DEF and Pb. The involvement of EST and the GST in the OPs resistance was confirmed by many previous studies [2,3,[25][26][27][28][29][30][31][32]. Our study is in agreement with previous publication on correlation between cytochrome P450 enzymes and resistance to pyrethroids [33].…”

Behavior of geladas and other endemic wildlife during a desert locust outbreak at Guassa, Ethiopia: ecological and conservation implications

“…Furthermore, not all locusts exposed to insecticides die (Rainey et al 1979;Peveling 2001). Indeed, increasing chemical pesticide resistance has become a major obstacle to migratory locust control in recent years (Yang et al 2009). During an outbreak in Australia in which locusts were sprayed with organophosphorous insecticides, locusts in weakened or dying states were the primary food item for several bird species (Story and Cox 2001).…”

RNA interference revealed the roles of two carboxylesterase genes in insecticide detoxification in Locusta migratoria

“…In Myzus persicae, the overexpression of a CarE (E4) gene by gene amplification contribute to the enhanced degradation and sequestration of many insecticides including OPs, carbamates and pyrethroids (Field and Devonshire, 1998). Previous studies have demonstrated that the increased CarE activity is responsible for malathion resistance in L. migratoria (Yang et al, 2008b). Although carbamates and pyrethroids have been used for locust control, little is known about detoxification of these insecticides by CarEs in the locust.…”