Response Mechanisms of Invertebrates to Bacillus thuringiensis and Its Pesticidal Proteins

Abstract

SUMMARY Extensive use of chemical insecticides adversely affects both environment and human health. One of the most popular biological pest control alternatives is bioinsecticides based on Bacillus thuringiensis. This entomopathogenic bacterium produces different protein types which are toxic to several insect, mite, and nematode species. Currently, insecticidal proteins belonging to the Cry and Vip3 groups are widely used to control insect pests both in formulated sprays and in transgenic crops. However, the benefits of B. thuringiensis-based products are threatened by insect resistance evolution. Numerous studies have highlighted that mutations in genes coding for surrogate receptors are responsible for conferring resistance to B. thuringiensis. Nevertheless, other mechanisms may also contribute to the reduction of the effectiveness of B. thuringiensis-based products for managing insect pests and even to the acquisition of resistance. Here, we review the relevant literature reporting how invertebrates (mainly insects and Caenorhabditis elegans) respond to exposure to B. thuringiensis as either whole bacteria, spores, and/or its pesticidal proteins.

The Rapid Evolution of Resistance to Vip3Aa Insecticidal Protein in Mythimna separata (Walker) Is Not Related to Altered Binding to Midgut Receptors

“…Additionally, Vip3Aa-resistant H. virescens larvae showed dramatically reduced levels of membrane-bound alkaline phosphatase, but its involvement in resistance could not be demonstrated [ 34 ]. Therefore, unlike for Cry proteins, altered binding to membrane receptors seems not to be the main mechanism of resistance to Vip3Aa proteins, and other mechanisms should be explored [ 35 ]. Other steps in the mode of action of Vip3Aa, either prior (such as protease activation or peritrophic matrix sequestration) or after (pore forming, signal transduction, apoptosis, mitochondria disruption, etc.)…”

The regulation landscape of MAPK signaling cascade for thwarting Bacillus thuringiensis infection in an insect host

“…Biopesticide formulations and transgenic crops based on Bt insecticidal toxins are widely adopted in pest control worldwide, providing tremendous ecological and socio-economic benefits [10][11][12][13][14][15][16][17]. However, insect pests have developed intricate strategies to counteract the detrimental effects caused by Bt toxins, thus, defining these molecular mechanisms evolved in insect hosts to counteract Bt infection is pivotal to establish successful strategies to counter insect resistance to Bt toxins [18][19][20][21][22][23].…”

Which Is Stronger? A Continuing Battle Between Cry Toxins and Insects

“…First, it is necessary to speed up the search for new Bt strains to more comprehensively screen and identify new Cry toxins ( Pinos et al, 2021 ) and to uncover more details about the insecticidal mechanism of the toxins.…”

“…One should insist on using the “High Dose Refuge Strategy” to rationally arrange the planting patterns of Bt-transgenic crops ( Bravo et al, 2011 ; Xiao and Wu, 2019 ). It is also necessary, in view of the complexity of insect resistance mechanisms ( Pinos et al, 2021 ), especially for the insect cross-resistance, to use a variety of Bt preparations or the combination of Bt preparations and other insecticides to produce a synergistic insecticidal effect. These may allow one to significantly promote the green and sustainable development of agriculture in the future.…”