昆虫中肠液性质对苏云金芽孢杆菌伴孢晶体毒力的影响

The effects of larval midgut fluid on the insecticidal activity of Bacillus thuringiensis parasporal crystal

综述了昆虫中肠液性质对苏云金芽孢杆菌Bacillusthuringiensis伴孢晶体毒力的影响。中肠液的酸碱度和蛋白酶是影响伴孢晶体溶解与原毒素活化的两大因素。中肠液的酸碱度不仅影响到伴孢晶体的溶解速度 ,还影响到各种蛋白酶的活性表现 ;而蛋白酶则直接参与了原毒素的活化 ,其组成与活性影响着原毒素的活化速度和杀虫专一性。因中肠液蛋白水解能力过高而导致原毒素的过度降解是某些昆虫对苏云金芽孢杆菌低度敏感的主要原因 ,而中肠液对原毒素活化能力的降低则与昆虫抗性的形成有关。此外 ,中肠液的沉淀作用及其它生理生化特性也影响着原毒素毒力的正常发挥。

The effects of larval midgut fluid on the toxicity of Bacillus thuringiensis parasporal crystal were reviewed in this paper. The characteristics of larval midgut juice, including pH value, the composition and activity of proteases, affect not only the crystal solubility and efficiency of protoxin activation,but also its insecticidal specificity. On the other hand, excessive degradation of protoxins in midgut juices was responsible for the low susceptibility of some insects. On the contrary, the retardation of protoxin activation in midgut juice contributes to the resistance of some insects against Bt. Moreover, the precipitation effect of gut juice on protoxins was another factor to lower Bt toxicity.