Characteristics of the sigK Deletion Mutant from Bacillus thuringiensis var. israelensis Strain Bt-59
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Characteristics of the sigK Deletion Mutant from Bacillus thuringiensis var. israelensis Strain Bt‑59 Linghuan Xu1,2,3 · Guangjie Han2 · Xintong Fan1 · Jing Lv1 · Xin Zhang1 · Qi Peng1 · Jie Zhang1 · Jian Xu2,3 · Fuping Song1 Received: 16 May 2019 / Accepted: 28 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract All major insecticidal genes of Bacillus thuringiensis var. israelensis (Bti) are controlled by the sporulation-specific sigma factor Sigma E (sigE), while sigE is negatively regulated by Sigma K (sigK). Therefore, knocking out sigK plays an important role in regulating the expression of insecticidal genes in Bti. A sigK deletion mutant of B. thuringiensis var. israelensis strain Bt-59, Bt59(ΔsigK), was constructed by homologous recombination and characterized. The sigK deletion resulted in no mature spores and delayed mother cell lysis from T25 to T60, while the genetically complemented strain, Bt59(HFsigK), had mother cell lysis at T25. Compared to Bt-59, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis indicated that the expression of Cry4Aa2/4Ba1 and Cyt1Aa1 proteins in Bt59(ΔsigK) increased approximately 1.67 and 1.21 times, respectively. However, there was no significant change in Cry11Aa1 protein expression between the two strains. Bioassay results showed that the sigK deletion mutation slightly reduced the insecticidal activity of Bt-59 against Culex pipiens pallens and did not obviously affect activity against Aedes albopictus.
Introduction Bacillus thuringiensis var. israelensis (Bti) is an important biological control of vectors, such as mosquitoes and blackflies [1]. Bti has been successfully developed into a biological pesticide for broad control of mosquito vectors [2, 3]. However, there are some disadvantages of Bti for the practical control of vectors, such as low virulence and short duration [4]. These limitations are inherent in most biological control agents. But the application-wide of recombinant Linghuan Xu and Guangjie Han have contributed equally to this work. * Jian Xu bio‑[email protected] * Fuping Song [email protected] 1
State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
2
Department of Applied Microbiology, Jiangsu Lixiahe District Institute of Agricultural Sciences, Yangzhou 225007, China
3
College of Bioscience and Biotechnology, Yangzhou University, Yangzhou 225002, China
DNA technology has made it possible to improve the insecticidal effect of Bti. Bti contains at least four major crystal protoxins, Cry4Aa, Cry4Ba, Cry11Aa, and Cyt1Aa [5]. Cry4Aa is highly toxic to larvae of Culex but is less toxic to Anopheles and Aedes. Cry4Ba has high larvicidal activities against Anopheles and Aedes but not Culex. Cry11Aa is highly toxic to Aedes and Culex but less toxic to Anopheles. Cyt1Aa has very low larvicidal activity against all three of these mosquito species, but it can act synergistically wit
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