Abstract
Discovery and identification of novel insecticidal proteins in Bacillus thuringiensis (Bt) strains are of crucial importance for efficient biological control of pests and better management of insect resistance. In this study, the Bt strain KhF, toxic for Plodia interpunctella and Grapholita molesta larvae, underwent genomics and proteomics analyses to achieve a better understanding of the bases of its pathogenicity. The whole-genome sequencing results revealed that the KhF strain contained nine coding sequences with homologies to Bt insecticidal genes. The lepidopteran toxic mixture of spores and crystals of this Bt strain was subjected to liquid chromatography and tandem mass spectrometry (LC-MS/MS) to assess the protein composition. The results of the proteomic analyses, combined with the toxin gene sequences, revealed that two of the main components of the crystals were two new candidate pesticidal proteins, named KhFA and KhFB. These proteins showed a similarity lower than 36% to the other known Bt toxins. The phylogenetic analysis showed that the KhFA and KhFB grouped with the newly denominated Xpp and Mpp (former ETX/Mtx) pesticidal protein groups, respectively. Altogether, this study has led to the discovery of two novel candidate pesticidal toxins in the lepidopteran toxic KhF strain.
Highlights
Bacillus thuringiensis (Bt) is the most successful and widely used microbial control agent for the management of insect pests [1]
B. thuringiensis strain KhF was originally isolated from a soil sample in Iran [21]
The protein profile of the spore/crystal mixture of KhF strain was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis, showing two main bands of almost 130 and 23 kDa and several other minor bands (Figure 1, Panel B, Lane 1)
Summary
Bacillus thuringiensis (Bt) is the most successful and widely used microbial control agent for the management of insect pests [1]. This entomopathogenic bacterium produces parasporal inclusion bodies comprised of crystal (Cry) and cytolytic (Cyt) proteins upon the sporulation [2,3]. Toxins 2020, 12, 673 several Bt strains have been characterized so far based on their genome sequencing and/or protein composition following mass-spectrometry based approaches to identify their gene content and proteome, as well to predict their biological activity [6,7,8,9,10,11,12]. The discovery of new Bt genes or proteins with different biological activity, a wider spectrum of activity, and higher insecticidal potency can lead to better management of insect pests
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