中文摘要：

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Bin A/Bin B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 k D左右的Cry48Aa蛋白带和53 k D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-p BU-cry48Aa-cry49Aa和BMB171-p BU-Pcry1Aacry48Aa-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（Cq SL）和抗性致倦库蚊（Cq RL/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0.82μL/m L。

英文摘要：

The Cry48Aa/Cry49 Aa, two-component toxin, shows high toxicity against Culex species, including binary toxin Bin A/Bin B-resistant Culex larvae. Being a potential novel mosquitocidal toxin, however, the low expression of Cry48 Aa in the wild strain limits its development and application. In this work, the promoter of cry48 Aa was replaced and cry48 Aa and cry49 Aa were coexpressed in Bacillus thuringiensis. The expression of recombinant proteins were detected by SDS-PAGE, visualized as a 120（Cry48Aa） and a 53 k Da（Cry49Aa） bands. The expression amount of cry48 Aa was low in its own promoter, which however, was significantly increased after the replacement of its promoter with the strong promoter Pcry1 Aa but was still lower than the expression of Cry49 Aa. Both the recombinant strains BMB171-p BU-cry48Aa-cry49 Aa and BMB171-p BU-Pcry1Aa-cry48Aacry49 Aa produced bipyramidal and squared crystals. The bioassay result showed that the two strains were effective against the 4th instar larvae of Bin-susceptible and-resistant C. quinquefasciatus, with the LC50 of 3.05 and 3.45, and 0.65 and 0.82 μL/m L, respectively.