Selection for resistance to methoxyfenozide and 20‐hydroxyecdysone in cells of the beet armyworm, Spodoptera exigua

Abstract

In this report with an ecdysteroid-responsive cell line of the beet armyworm, Spodoptera exigua (Se4) selection for resistance against methoxyfenozide and the insect moulting hormone (20-hydroxyecdysone, 20E) was carried out to analyze the resulting resistant cells in order to elucidate possible mechanisms of resistance towards these compounds. From these cultures, five methoxyfenozide- and four 20E-resistant subclones were selected starting from 0.1 nM methoxyfenozide up to 100 microM and from 10 nM 20E up to 100 microM, respectively. To date, the selected cells kept their loss of susceptibility for 100 microM. Here we evaluated two processes known to be important in insecticide resistance, namely metabolism and pharmacokinetics, in the selected methoxyfenozide- and 20E-resistant subclones. Synergism experiments with piperonyl butoxide, S,S,S-tributyl phosphorotrithioate, and diethyl maleate, which are respective inhibitors of monooxygenases, esterases, and gluthation-S-transferases, did not affect the level of the resistance. To check the possible existence of active transport in the resistant cells, we used ouabain, an inhibitor of active membrane transport. In parallel, the absorption profile was studied in resistant and susceptible cells with use of 14C-methoxyfenozide. Interestingly, resistant subclones showed cross-resistance towards methoxyfenozide and 20E. The resistance was irreversible even after the compounds were removed from the medium.

Ecdysteroid signaling in ecdysteroid-resistant cell lines from the polyphagous noctuid pest Spodoptera exigua

“…These experiments indicate that, in contrast to the 20E-resistant cells, it requires continuing growth of the methoxyfenozide-resistant cells to clear the agonist from the cells' interiors. It is noted that growth in agonist-free medium for 3 passages does not affect the resistance of the cells with respect to inhibition of growth by methoxyfenozide (data not shown; Mosallanejad et al, 2008).…”

Insect cell culture and applications to research and pest management

“…Based on this principle, a similar system was developed with a "pBmbA/ERE.luciferase" construct in other lepidopteran, dipteran, and coleopteran cell lines (Mosallanejad et al 2008b). These cell systems also allow screening for insecticide resistance development (Spindler-Barth and Spindler 1998;Mosallanejad et al 2008a). These cell-based protocols will facilitate rapid screening and discovery of new anti-insect chemistries.…”

TOXICITY OF ALLYL ESTERS IN INSECT CELL LINES AND IN SPODOPTERA LITTORALIS LARVAE

“…• C and 80% relative humidity (RH) in the Laboratory of Agrozoology at Ghent University (Belgium ; midgut cells of Choristoneura fumiferana (Lepidoptera: Tortricidae)] in InsectXpress medium (BioWittacker, Verviers, Belgium) supplemented with 2.5% of FBS, as previously described (Swevers et al, 2003;Decombel et al, 2004;Mosallanejad et al, 2008;Soin et al, 2009;Shahidi-Noghabi et al, 2010).…”