Cadherin binding is not a limiting step for Bacillus thuringiensis subsp. israelensis Cry4Ba toxicity to Aedes aegypti larvae.

The Biochemical Journal
Claudia Rodríguez-AlmazánMario Soberón

Abstract

Bacillus thuringiensis subsp. israelensis produces three Cry toxins (Cry4Aa, Cry4Ba and Cry11Aa) that are active against Aedes aegypti larvae. The identification of the rate-limiting binding steps of Cry toxins that are used for insect control in the field, such as those of B. thuringiensis subsp. israelensis, should provide targets for improving insecticides against important insect pests. Previous studies showed that Cry11Aa binds to cadherin receptor fragment CR7-11 (cadherin repeats 7-11) with high affinity. Binding to cadherin has been proposed to facilitate Cry toxin oligomer formation. In the present study, we show that Cry4Ba binds to CR7-11 with 9-fold lower binding affinity compared with Cry11Aa. Oligomerization assays showed that Cry4Ba is capable of forming oligomers when proteolytically activated in vitro in the absence of the CR7-11 fragment in contrast with Cry11Aa that formed oligomers only in the presence of CR7-11. Pore-formation assays in planar lipid bilayers showed that Cry4Ba oligomers were proficient in opening ion channels. Finally, silencing the cadherin gene by dsRNA (double-stranded RNA) showed that silenced larvae were more tolerant to Cry11Aa in contrast with Cry4Ba, which showed similar toxic level...Continue Reading

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Citations

Sep 23, 2014·Insect Biochemistry and Molecular Biology·Su-Bum LeeSarjeet S Gill
Oct 23, 2012·Bioscience Reports·Victor V Lemeshko, Sergio Orduz
Jan 9, 2019·Applied Microbiology and Biotechnology·Qi PengFuping Song
Jul 30, 2020·Journal of Insect Science·Kashif MunawarSayed M S Khalil
Jan 10, 2017·Insects·Paul M Airs, Lyric C Bartholomay
Aug 27, 2021·Toxins·Maria Helena Neves Lobo Silva-FilhaAlejandra Bravo

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