Department of Entomology, Instituto Aggeu Magalhães-FIOCRUZ, Av. Moraes Rego s/n, Recife, PE, 50740-465, Brazil.
Laboratory of Insect Biochemistry and Physiology, Instituto Oswaldo Cruz-FIOCRUZ, Rio de Janeiro, RJ, 21045-900, Brazil.
Parasit Vectors. 2023 Aug 9;16(1):273. doi: 10.1186/s13071-023-05893-z.
The resistance of a Culex quinquefasciatus strain to the binary (Bin) larvicidal toxin from Lysinibacillus sphaericus is due to the lack of expression of the toxin's receptors, the membrane-bound Cqm1 α-glucosidases. A previous transcriptomic profile of the resistant larvae showed differentially expressed genes coding Cqm1, lipases, proteases and other genes involved in lipid and carbohydrate metabolism. This study aimed to investigate the metabolic features of Bin-resistant individuals by comparing the activity of some enzymes, energy reserves, fertility and fecundity to a susceptible strain.
The activity of specific enzymes was recorded in midgut samples from resistant and susceptible larvae. The amount of lipids and reducing sugars was determined for larvae and adults from both strains. Additionally, the fecundity and fertility parameters of these strains under control and stress conditions were examined.
Enzyme assays showed that the esterase activities in the midgut of resistant larvae were significantly lower than susceptible ones using acetyl-, butyryl- and heptanoyl-methylumbelliferyl esthers as substrates. The α-glucosidase activity was also reduced in resistant larvae using sucrose and a synthetic substrate. No difference in protease activities as trypsins, chymotrypsins and aminopeptidases was detected between resistant and susceptible larvae. In larval and adult stages, the resistant strain showed an altered profile of energy reserves characterized by significantly reduced levels of lipids and a greater amount of reducing sugars. The fertility and fecundity of females were similar for both strains, indicating that those changes in energy reserves did not affect these reproductive parameters.
Our dataset showed that Bin-resistant insects display differential metabolic features co-selected with the phenotype of resistance that can potentially have effects on mosquito fitness, in particular, due to the reduced lipid accumulation.
致倦库蚊对球形芽孢杆菌二元（Bin）幼虫杀毒素的抗性是由于缺乏毒素受体——膜结合的 Cqm1α-葡萄糖苷酶的表达。先前对抗性幼虫的转录组图谱研究表明，编码 Cqm1、脂肪酶、蛋白酶和其他参与脂质和碳水化合物代谢的基因差异表达。本研究旨在通过比较一些酶的活性、能量储备、生育力和繁殖力，来研究 Bin 抗性个体的代谢特征，以与敏感品系进行比较。
记录抗性和敏感幼虫中肠样本中特定酶的活性。测定两种品系幼虫和成虫的脂质和还原糖含量。此外，还检测了这些品系在对照和胁迫条件下的繁殖力和繁殖力参数。
酶谱分析表明，用乙酰基、丁酰基和庚酰基-甲基伞形酮酯作为底物时，抗性幼虫中肠的酯酶活性明显低于敏感幼虫；用蔗糖和合成底物时，抗性幼虫的α-葡萄糖苷酶活性也降低。未检测到抗性幼虫和敏感幼虫的胰蛋白酶、糜蛋白酶和氨肽酶的蛋白酶活性存在差异。在幼虫和成虫阶段，抗性品系表现出能量储备的改变特征，表现为脂质水平显著降低，还原糖含量增加。两种品系雌蚊的生育力和繁殖力相似，表明这些能量储备的变化并未影响这些繁殖参数。
我们的数据集表明，Bin 抗性昆虫表现出与抗性表型共同选择的差异代谢特征，这可能会对蚊子的适应性产生影响，特别是由于脂质积累减少。
