Trade‐off between thermal tolerance and insecticide resistance in Plutella xylostella

Abstract

Fitness costs associated with resistance to insecticides have been well documented, usually at normal temperature conditions, in many insect species. In this study, using chlorpyrifos-resistant homozygote (RR) and chlorpyrifos-susceptible homozygote (SS) of resistance ace1 allele of Plutella xylostella (DBM), we confirmed firstly that high temperature experience in pupal stage influenced phenotype of wing venation in insecticide-resistant and insecticide-susceptible Plutella xylostella, and SS DBM showed significantly higher thermal tolerance and lower damages of wing veins under heat stress than RR DBM. As compared to SS DBM, RR DBM displayed significantly lower AChE sensitivity to chlorpyrifos, higher basal GSTs activity and P450 production at 25°C, but higher inhibitions on the enzyme activities and P450 production as well as reduced resistance to chlorpyrifos under heat stress. Furthermore, RR DBM displayed significantly higher basal expressions of hsp69s, hsp72s, hsp20,hsp90,Apaf-1, and caspase-7 at 25°C, but lower induced expressions of hsps and higher induced expressions of Apaf-1,caspase-9, and caspase-7 under heat stress. These results suggest that fitness costs of chlorpyrifos resistance in DBM may partly attribute to excess consumption of energy caused by over production of detoxification enzymes and hsps when the proteins are less demanded at conducive environments but reduced expressions when they are highly demanded by the insects to combat environmental stresses, or to excess expressions of apoptotic genes under heat stress, which results in higher apoptosis. The evolutionary and ecological implications of these findings at global warming are discussed.

Climate change and the genetics of insecticide resistance

“…For example, a laboratory study showed that higher temperatures impose a fitness cost on the chlorpyrifos‐resistant strain of the diamondback moth, Plutella xylostella . Under heat stress, the resistant strain of Plutella xylostella has higher rates of wing vein damage and lower survival than the susceptible strain, suggesting a tradeoff between thermotolerance and insecticide resistance . Similarly, in the brown planthopper, Nilaparvata lugens , a chlorpyrifos‐resistant strain is associated with lower fitness compared to its susceptible counterparts at higher temperatures, suggesting that a common genetic mechanism could underlie chlorpyrifos resistance and tradeoffs with thermotolerance in distant species.…”

“…Under heat stress, the resistant strain of Plutella xylostella has higher rates of wing vein damage and lower survival than the susceptible strain, suggesting a tradeoff between thermotolerance and insecticide resistance. 11 Similarly, in the brown planthopper, Nilaparvata lugens, a chlorpyrifos-resistant strain is associated with lower fitness compared to its susceptible counterparts at higher temperatures, 12 suggesting that a common genetic mechanism could underlie chlorpyrifos resistance and tradeoffs with thermotolerance in distant species. The second category is that climatic adaptation will also facilitate the development of insecticide resistance, resulting in an increase in insecticide resistance alleles.…”

Susceptibilities of Candidatus Liberibacter asiaticus‐infected and noninfected Diaphorina citri to entomopathogenic fungi and their detoxification enzyme activities under different temperatures

“…Although previous studies have been conducted to show the effect of temperature on synthetic insecticides susceptibility, the alteration in entomopathogenic fungi pathogenicity due to changes in temperature was not understood (Deng, Zhang, Wu, Yu, & Wu, ; Garcia et al., ; Lasa, Williams, & Caballero, ; Zhang et al., ). However, susceptibility to entomopathogenic fungi was increased in Las‐infected as compared to uninfected D. citri , but Las infection did not affect the correlation coefficients between temperature and psyllids mortality.…”

Type of fitness cost influences the rate of evolution of resistance to transgenic Bt crops

“…2007), temperature (Zhang et al . 2015) or biotic interactions (Becker & Liess 2015). When fitness costs are context sensitive, the resistance allele frequency may not necessarily decline in the absence of selection.…”

“…Some of these factors will be ecological and may exaggerate or conceal pleiotropic effects associated with a resistance allele (Gassmann, Onstad & Pittendrigh 2009); that is, fitness costs may exhibit a degree of context dependence and may increase or only become visible to selection in the presence of additional environmental stressors. For example, fitness costs may be exaggerated by factors such as host plant variety (Bird & Akhurst 2007), parasites and pathogens (Raymond et al 2007), temperature (Zhang et al 2015) or biotic interactions (Becker & Liess 2015). When fitness costs are context sensitive, the resistance allele frequency may not necessarily decline in the absence of selection.…”