Insecticide resistance is inevitable if an insecticide is widely used to control insect pests. Fortunately, the resistance-associated fitness costs often give chances to manage resistances. In most cases, the fitness ...Insecticide resistance is inevitable if an insecticide is widely used to control insect pests. Fortunately, the resistance-associated fitness costs often give chances to manage resistances. In most cases, the fitness cost in resistant insects is often evaluated under laboratory conditions for insect development, which limits its practical application in pest control in the field. In a laboratory population R9 with 253-fold resistance to chlorpyrifos after nine-generation selection with chlorpyrifos, the relative fitness was only 0.206 under laboratory conditions （25℃, humidity 70%-80% and 16 h light/8 h dark photoperiod）, when compared to S9, a susceptible counterpart （resistance ratio = 2.25- fold） from the same origin as R9 but without any selection with insecticides. Temperatures varied the resistance-associated fitness costs, with enhanced costs at high temperatures and reduced costs at low temperatures, such as 0.174 at 32℃ and 0.527 at 18℃. The copulation rate and fecundity were two key factors for the reduced costs at low temperatures. Another finding was that R9 individuals needed much more time to recover from heat shock than that of S9, but R9 and $9 individuals were similarly sensitive to cold shock. The low fitness cost at low temperatures would increase the overwintering population, which might further increase risks of rapid development and widespread distribution of chlorpyrifos resistance in Nilaparvata lugens.展开更多
The lipid metabolism plays an essential role in the development andreproduction of insects, and lipases are important enzymes in lipid metabolism. In Nilaparvatalugens, an important insect pest on rice, triacylglycero...The lipid metabolism plays an essential role in the development andreproduction of insects, and lipases are important enzymes in lipid metabolism. In Nilaparvatalugens, an important insect pest on rice, triacylglycerol hydrolytic activities weredifferent among tissues, with high activity in integument, ovary, and fat body, but low activityin intestine. To figure out the tissue-specific triacylglycerol hydrolytic activity, weidentified 43 lipases in N. lugens. Of these 43 lipases, 23 belonged to neutral lipases, sothis group was selected to perform further experiments on triacylglycerol hydrolysis. Thecomplete motifs of catalytic triads, β9 loop, and lid motif, are required for the triacylglycerolhydrolytic activity in neutral lipases, which were found in some neutral lipases withhigh gene expression levels in integument and ovary, but not in intestine. The recombinantproteins of 3 neutral lipases with or without 3 complete motifs were obtained, and the activitydetermination confirmed the importance of 3 motifs. Silencing XM_022331066.1,which is highly expressed in ovary and with 3 complete motifs, significantly decreasedthe egg production and hatchability of N. lugens, partially through decline of the lipidmetabolism. In summary, at least one-third of important motifs were incomplete in allneutral lipases with high gene expression in intestine, which could partially explain whythe lipase activity in intestine was much lower than that in other tissues. The low activityto hydrolyze triacylglycerol in N. lugens intestine might be associated with its food resourceand nutrient components, and the ovary-specific neutral lipases were important forN. lugens reproduction.展开更多
文摘Insecticide resistance is inevitable if an insecticide is widely used to control insect pests. Fortunately, the resistance-associated fitness costs often give chances to manage resistances. In most cases, the fitness cost in resistant insects is often evaluated under laboratory conditions for insect development, which limits its practical application in pest control in the field. In a laboratory population R9 with 253-fold resistance to chlorpyrifos after nine-generation selection with chlorpyrifos, the relative fitness was only 0.206 under laboratory conditions （25℃, humidity 70%-80% and 16 h light/8 h dark photoperiod）, when compared to S9, a susceptible counterpart （resistance ratio = 2.25- fold） from the same origin as R9 but without any selection with insecticides. Temperatures varied the resistance-associated fitness costs, with enhanced costs at high temperatures and reduced costs at low temperatures, such as 0.174 at 32℃ and 0.527 at 18℃. The copulation rate and fecundity were two key factors for the reduced costs at low temperatures. Another finding was that R9 individuals needed much more time to recover from heat shock than that of S9, but R9 and $9 individuals were similarly sensitive to cold shock. The low fitness cost at low temperatures would increase the overwintering population, which might further increase risks of rapid development and widespread distribution of chlorpyrifos resistance in Nilaparvata lugens.
基金the National Natural Science Foundation of China(grant number 31830075)the National Key Research and Development Program of China(2021YFD1401100).
文摘The lipid metabolism plays an essential role in the development andreproduction of insects, and lipases are important enzymes in lipid metabolism. In Nilaparvatalugens, an important insect pest on rice, triacylglycerol hydrolytic activities weredifferent among tissues, with high activity in integument, ovary, and fat body, but low activityin intestine. To figure out the tissue-specific triacylglycerol hydrolytic activity, weidentified 43 lipases in N. lugens. Of these 43 lipases, 23 belonged to neutral lipases, sothis group was selected to perform further experiments on triacylglycerol hydrolysis. Thecomplete motifs of catalytic triads, β9 loop, and lid motif, are required for the triacylglycerolhydrolytic activity in neutral lipases, which were found in some neutral lipases withhigh gene expression levels in integument and ovary, but not in intestine. The recombinantproteins of 3 neutral lipases with or without 3 complete motifs were obtained, and the activitydetermination confirmed the importance of 3 motifs. Silencing XM_022331066.1,which is highly expressed in ovary and with 3 complete motifs, significantly decreasedthe egg production and hatchability of N. lugens, partially through decline of the lipidmetabolism. In summary, at least one-third of important motifs were incomplete in allneutral lipases with high gene expression in intestine, which could partially explain whythe lipase activity in intestine was much lower than that in other tissues. The low activityto hydrolyze triacylglycerol in N. lugens intestine might be associated with its food resourceand nutrient components, and the ovary-specific neutral lipases were important forN. lugens reproduction.
