球形芽胞杆菌Cry48Aa/Cry49Aa毒素在苏云金芽胞杆菌中的共表达及杀蚊活性

球形芽胞杆菌Cry48Aa/Cry49Aa复合杀蚊毒素对库蚊有高毒力,并能杀死二元毒素BinA/BinB抗性蚊虫,是一种比较有潜力的新型杀蚊毒素蛋白,但Cry48Aa在野生菌株中表达量较低限制了该毒素的开发与应用。本文将cry48Aa基因启动子置换,并将cry48Aa和cry49Aa在苏云金芽胞杆菌中进行共表达。SDS-PAGE检测重组蛋白表达,可见120 kD左右的Cry48Aa蛋白带和53 kD的Cry49Aa蛋白带,cry48Aa在自身启动子下表达量偏低,在置换强启动子Pcry1Aa后表达量明显提高,但Cry48Aa仍低于Cry49Aa的表达量。重组菌株BMB171-pBU-cry48Aa-cry49Aa和BMB171-pBU-Pcry1Aa-cry48Aa-cry49Aa产生典型的双锥型和方形2种晶体。两菌株发酵液对实验室饲养的二元毒素敏感(CqSL)和抗性致倦库蚊(CqRL/C3-41)品系4龄幼虫都表现出高毒力,LC₅₀分别为3.05和3.45以及0.65和0.82 μL/mL。     

Lack of cross-resistance to Mtx1 from Bacillus sphaericus in B. sphaericus-resistant Culex quinquefasciatus (Diptera: Culicidae)

The toxicities of Mtx1 toxin against dipteran and lepidopteran species have been evaluated in this study. It was shown that Mtx1 has little or no toxicity to the tested lepidopteran species, but has moderate-level toxicity to Aedes albopictus Skuse (Diptera: Culicidae) and high-level toxicity to both susceptible and binary toxin-resistant Culex quinquefasciatus Say (Diptera: Culicidae). The LC(50) values of Mtx1 against a susceptible C. quinquefasciatus colony SLCq and two resistant colonies RLCq1/C3-41 and RLCq2/IAB59 selected in the laboratory with Bacillus sphaericus (Mayer & Neide) strains C3-41 and IAB59 respectively were 0.508, 0.854 and 0.675 mg L(-1) respectively. The data indicate that Mtx1 has a different mode of action from the binary toxin, and that it could be an alternative toxin to delay or overcome resistance development to binary toxin in C. quinquefasciatus.