Cry Proteins from Bacillus thuringiensis Active against Diamondback Moth and Fall Armyworm

Abstract

Biopesticides based on Bacillus thuringiensis and genetically modified plants with genes from this bacterium have been used to control Plutella xylostella (L.) and Spodoptera frugiperda (J.E. Smith). However, the selection pressure imposed by these technologies may undermine the efficiency of this important alternative to synthetic insecticides. Toxins with different modes of action allow a satisfactory control of these insects. The purpose of this study was to characterize the protein and gene contents of 20 B. thuringiensis isolates from soil and insect samples collected in several areas of Northeast Brazil which are active against P. xylostella and S. frugiperda. Protein profiles were obtained by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Polymerase chain reaction assays were used to determine toxin genes present within bacterial isolates. The protein profile of the majority of the isolates produced bands of approximately 130 kDa, suggesting the presence of Cry1, Cry8 and Cry9 proteins. The gene content of the isolates of B. thuringiensis investigated showed different gene profiles. Isolates LIIT-4306 and LIIT-4311 were the most actives against both species, with LC50 of 0.03 and 0.02 × 10(8) spores mL(-1), respectively, for P. xylostella, and LC50 of 0.001 × 10(8) spores mL(-1) for S. frugiperda. These isolates carried the cry1, cry1Aa, cry1Ab, cry1Ac, cry1B, cry1C, cry1D, cry1F, cry2, cry2A, cry8, and cry9C genes. The obtained gene profiles showed great potential for the control of P. xylostella and S. frugiperda, primarily because of the presence of several cry1A genes, which are found in isolates of B. thuringiensis active against these insects.

Gut Bacterial Diversity in Different Life Cycle Stages of Adelphocoris suturalis (Hemiptera: Miridae)

“…In China, due to the large-scale planting of Bt crops, A. suturalis has risen from secondary pests in cotton fields to primary pests. Among them, Cry1, Cry2, and Cry9 toxins have been reported to show high insecticidal activity against lepidopteran pests ( Palma et al, 2014 ; Silva et al, 2015 ). Once ingested by the susceptible insect larvae, these cry proteins (present in the form of protoxin) are proteolytically processed by midgut proteases to the active toxin that subsequently binds to specific protein receptors of the midgut epithelium leading to cell disruption and eventual death of the insect larvae ( Pardo-López et al, 2013 ).…”

MiR-2b-3p Downregulated PxTrypsin-9 Expression in the Larval Midgut to Decrease Cry1Ac Susceptibility of the Diamondback Moth, Plutella xylostella (L.)

“…Bt sprays or Cry transgenic crops harboring various Cry insecticidal proteins are widely used as effective strategies for pest biocontrol. Furthermore, Bt-based insecticides offer a safer and eco-friendly alternative to synthetic chemical pesticides. − However, the widespread use of Bt and the rapid adaptability of insects have led to pest resistance and resurgence. To ensure the effective long-term utilization of Bt technology, it is imperative to understand the precise mechanisms underlying insect mortality and the molecular basis of resistance evolved by insects to Bt toxins …”

Characterization of a Novel Insecticidal Protein Cry9Cb1 from Bacillus thuringiensis

“…ICPs are mostly Cry proteins, an important component of Bt biopesticides and vital tools for insect control in transgenic crops. , To date, the identified Cry proteins have been classified into Cry1–Cry78 on the basis of amino acid sequence identity (). Among these, Cry1, Cry2, and Cry9 proteins exhibit strong insecticidal activity against lepidopteran pests. − Cry1 proteins have been widely applied in transgenic cotton, corn, and soybean to control lepidopteran pests over the last 22 years. , However, there has been an increasingly rapid evolution of resistance because of years of successive planting and the same toxin being expressed by all Bt crops, hence creating high selection pressure on insect populations. Alternatively, using Cry toxins, with high insecticidal activity against major pests and involving different mechanisms of action, might help in delaying the development of insect resistance .…”