title: Cytolytic toxin Cyt1Aa of Bacillus thuringiensis synergizes the mosquitocidal toxin Mtx1 of Bacillus sphaericus.
abstract: Using the shuttle vector pBU4, the mosquitocidal toxin gene mtx1 from Bacillus sphaericus strain SSII-1 was introduced into an acrystalliferous strain of B. thuringiensis both individually and in combination with the accessory protein gene p20 and the cytolytic protein gene cyt1Aa from B. thuringiensis subsp. israelensis. Bioassay results indicated that the recombinants B-pMT4(Mtx1) and B-pMT9(Mtx1), both individually containing mtx1, had moderate toxicities to binary toxin susceptible and binary toxin resistant Culex quinquefasciatus larvae during the vegetative growth stage, but that their toxicities declined rapidly during the sporulation phase. The LC50 values were 2.5 and 4.8 mg/ml respectively, against 3-4 instar susceptible and resistant larvae for the final sporulated cultures of recombinants B-pMT9(Mtx1), and little toxicity was detected for B-pMT4(Mtx1). Meanwhile, the recombinant B-pMPX2(Mtx1+Cyt1Aa) expressing Mtx1, P20 alone, and Cyt1Aa in combination had stable toxicities during both the vegetative phase and the sporulation phase, with a LC50 ranging from 0.45-0.58 mg/ml. Furthermore, expression of Cyt1Aa appeared to enhance the activity of Mtx1 to target mosquito larvae, suggesting a synergism between Cyt1Aa and Mtx1 toxins.
authors.affiliation: Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China.
authors.forename: Beihua
authors.initials: B
authors.lastname: Zhang
authors.forename: Ming
authors.initials: M
authors.lastname: Liu
authors.forename: Yankun
authors.initials: Y
authors.lastname: Yang
authors.forename: Zhiming
authors.initials: Z
authors.lastname: Yuan
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000235:genetics / Q000378:metabolism*; D001427:Bacterial Toxins / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology*; D001681:Biological Assay; D003465:Culex / Q000254:growth & development*; D004357:Drug Synergism; D004591:Electrophoresis, Polyacrylamide Gel; D008855:Microscopy, Electron, Scanning; D010572:Pest Control, Biological / Q000379:methods*; D010957:Plasmids / Q000737:chemistry / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology*; D014169:Transformation, Bacterial
chemical_list: D001427:Bacterial Toxins; D011994:Recombinant Proteins