Towards novel Cry toxins with enhanced toxicity/broader: a new chimeric Cry4Ba / Cry1Ac toxin
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Attempts have been made to express or to merge different Cry proteins in order to enhance toxic effects against various insects. Cry1A proteins of Bacillus thuringiensis form a typical bipyramidal parasporal crystal and their protoxins contain a highly conserved C-terminal region. A chimerical gene, called cry(4Ba-1Ac), formed by a fusion of the N-terminus part of cry4Ba and the C-terminus part of cry1Ac, was constructed. Its transformation to an acrystalliferous B. thuringiensis strain showed that it was expressed as a chimerical protein of 116 kDa, assembled in spherical to amorphous parasporal crystals. The chimerical gene cry(4Ba-1Ac) was introduced in a B. thuringiensis kurstaki strain. In the generated crystals of the recombinant strain, the presence of Cry(4Ba-1Ac) was evidenced by MALDI-TOF. The recombinant strain showed an important increase of the toxicity against Culex pipiens larvae (LC50 = 0.84 mg l−1 ± 0.08) compared to the wild type strain through the synergistic activity of Cry2Aa with Cry(4Ba-1Ac). The enhancement of toxicity of B. thuringiensis kurstaki expressing Cry(4Ba-1Ac) compared to that expressing the native toxin Cry4Ba, might be related to its a typical crystallization properties. The developed fusion protein could serve as a potent toxin against different pests of mosquitoes and major crop plants.
KeywordsBacillus thuringiensis kurstaki Chimerical protein Cry(4Ba-1Ac) Toxicity improvement to Culex pipiens
This work was supported by grants from the Tunisian Ministry of Higher Education and Scientific Research. The authors wish to thank Dr. Manel Masmoudi, assistant professor in Higher Institute of Biotechnology of Sfax, for her help in samples preparation for examination by scanning electron microscopy. They also wish to thank to Mr. Abdelmajid Dammak for his proofreading of the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declared that they have no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
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