Location: Biological Control of Insects ResearchTitle: Molecular basis for insecticide-enhanced thermotolerance in the brown planthopper Nilaparvata lugens Stal (Hemiptera:Delphacidae)) Author
Submitted to: Molecular Ecology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/27/2013
Publication Date: 10/16/2013
Citation: Ge, L., Huang, L., Yang, G., Song, Q., Stanley, D.W., Gurr, G.M., Wu, J. 2013. Molecular basis for insecticide-enhanced thermotolerance in the brown planthopper Nilaparvata lugens Stal (Hemiptera:Delphacidae). Molecular Ecology. 22(22):5624-5634. Interpretive Summary: Climate change will have marked effects on the activities of insect pests. Most attention has focused on their geographical ranges. A central problem, however, is the potential risks of exposing pest populations to low, non-lethal, levels of pesticides. The risks include increased numbers of generations per year, and longer daily and annual activity periods. These changes in pest populations may have severe consequences, including increased crop losses and decreased food security at the global level. In this paper we investigated the influence of the insecticide triazophos (tzp) on the brown planthopper (BPH), a pest of rice crops in temperate and tropical regions of Asia. BPHs are often present in rice crops at very high temperatures, close to BPH temperature survival limits. We tested whether tzp, an insecticide used in Asian rice production, increased the temperature survival limits of BPHs. Tzp exposure significantly decreased mortality and increased survival at high temperatures. We investigated the underlying molecular mechanism. We discovered two proteins that are essential for surviving heat stress. We propose tzp induces survival in BPHs by increasing proteins that act in cell protection mechanisms. These findings suggest that pest management programs can be improved by research to better understand stress tolerance induced by extrinsic factors. Scientists who study the influence of global climate change on pest insects will use the information in their research programs. Ultimately, this research will benefit growers who produce crops in high-temperature environments and the people who consume these crops.
Technical Abstract: Climate change will have marked effects on terrestrial ecosystems, including the activity of insect pests. Most attention has focused on the increasing geographical ranges of pests, however, if extrinsic factors enhance their thermotolerance, populations express increased voltinism, and longer daily and annual activity periods. These changes in pest populations have the potential for severe consequences, including increased crop losses and decreased food security at the global level. The brown planthopper (BPH) Nilaparvata lugens is a pest of rice crops in temperate and tropical regions of Asia. It is often present in rice microclimates at temperatures close to its maximum thermotolerance. This study tested whether triazophos (tzp), an insecticide widely used in Asian rice production, enhanced thermotolerance of BPH. Tzp exposure significantly decreased mortality (from 94% in controls to 50% at 48h post-treatment) and increased lethal mean time (LT50) of adults by 17.2 h. To investigate the underlying molecular mechanism, we selected Hsp70 and Arginine kinase (Argk) for detailed study. Transcripts encoding both proteins in 3rd instar nymphs and adult females were up-regulated, compared to controls, after exposure to tzp. RNAi silencing of both genes demonstrated that Hsp70 and Argk are essential tzp-increased thermotorelance. We propose tzp induces thermotolerance in BPHs by increasing expression of genes that act in cell protection mechanisms. The present experiment showed that tzp induced the enhancement of thermotorelance. Therefore, the two effects may be due to cross- effects, i.e., the chemicals also influence BPH thermotolerance as well as reproduction. The present findings suggest that pest management programs need better understanding of stress tolerance induced by extrinsic factors including other pesticides.