Lethal and Sublethal Effects of Methoxyfenozide on the Development, Survival and Reproduction of the Fall Armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae)

The lethal and sublethal effects of the ecdysone agonist methoxyfenozide on the fall armyworm, Spodoptera frugiperda (J. E. Smith), were investigated by feeding a methoxyfenozide-treated diet to fifth instars until pupation in doses corresponding to the LC10 and LC25 for the compound. Larval mortality reached 8 percent and 26 percent in the low and high concentration groups, respectively, on the seventh day of the experiment. A progressive larval mortality of 12 percent for the LC10 and 60 percent for the LC25 was observed before pupation. Treated larvae exhibited lower pupal weights, higher pupal mortality, presence of deformed pupae, and more deformed adults than untreated larvae. The incorporation of methoxyfenozide into the diet had a significant effect on the timing of larval development. The development period for males and females was about seven days longer than the controls for both concentrations tested. In contrast, the compound affected neither pupae nor adult longevity. Finally, S. frugiperda adults that resulted from fifth instars treated with methoxyfenozide were not affected in their mean cumulative number of eggs laid per female (fecundity), nor percentages of eggs hatched (fertility), or the sex ratio. Our results suggest that the combination of lethal and sublethal effects of methoxyfenozide may have important implications for the population dynamics of the fall armyworm.

Construction of a Yeast Model for Screening Aedes albopictus Ecdysone Agonist Pesticides / 中国寄生虫学与寄生虫病杂志

Objective To reconstitute a transactivation system in yeast (yeast model) for screening the pesticides acting on ecdysone metabolism route and eventually influencing the process of ecdysis. Methods The fragment of 5 times repeated EcRE from Drosophila melanogaster was synthesized and the HSP27 promoter from D. melanogaster genome was amplified with PCR. The two sequences were connected and followed by a reporting gene——green fluorescence protein(GFP) gene. The EcRE-HSP27 promoter-GFP fragment was inserted into the expression plasmid pPIC3.5 and integrated into the yeast chromosome to construct yeast A. EcR and USP coding sequences of Aedes albopictus were synthesized, and these two fragments were inserted into Pichia pastoris expression plasmid pGAPZ as two respective reading frames. The two reading frames were integrated into Pichia pastoris chromosome in another recombinant site(pGAPZ and pPIC3.5k share different recombinant sites while being integrated into Pichia pastoris yeast chromosome). EcR and USP were constituted and expressed in the yeast. This recombinant yeast was called yeast B. The model yeast was thus constructed. A known ecdysone agonist-tebufenozide was used to test the yeast model. The effect of tebufenozide on the model yeast was observed under fluorescent microscope. Semi-quantitative RT-PCR was used to test the transcrip-tion level of GFP in the tebufenozide affected yeast and the control. Results In the model yeast, the intracellular expressed EcR and USP constituted EcR/USP heterodimer interacting with EcRE, the expression of GFP was activated, and green fluorescence was observed in model yeast under fluorescent microscope. Tebufenozide affected model yeast showed less fluorescence in comparison to the control model yeast, indicating that the transcription of GFP was suppressed by tubufenozide. Yeast housekeeping gene Actin-1 was used as inner control, semi-quantitative RT-PCR was operated and the result was scanned. The ratio of the brightness of GFP to Actin-1 was calculated automatically, and that of tubufenozide added yeast and the control yeast was 0.614 and 1.134 respectively. This result showed a low transcription level of GFP in tebufenozide affected model yeast, comparing to that of the control. Conclusion The ecdysone-related transacting system in yeast has been constructed, and the model yeast can be used to screen the ecdysone agonists which can act on the ecdysone metabolic route.