Mechanisms and molecular genetics of insect resistance to insecticidal proteins from Bacillus thuringiensis

Authors: Fabrick, Jeffrey; WU, YIDONG - Nanjing Agricultural University

Submitted to: Advances in Insect Physiology
Publication Type: Book / Chapter
Publication Acceptance Date: 9/8/2023
Publication Date: 10/9/2023
Citation: Fabrick, J.A., Wu, Y. 2023. Mechanisms and molecular genetics of insect resistance to insecticidal proteins from Bacillus thuringiensis. In: Jurat-Fuentes, J.L., editor. Advances in Insect Physiology. Volume 65. Cambridge, MA: Elsevier. p. 123-183. https://doi.org/10.1016/bs.aiip.2023.09.005.
DOI: https://doi.org/10.1016/bs.aiip.2023.09.005

Interpretive Summary: Insecticidal proteins from Bacillus thuringiensis (Bt) are used globally as bioinsecticides and within genetically engineered crops, providing benefits such as enhanced pest suppression, improved yields, increased farmer profits, and reduced environmental and health risks associated with the decreased use of conventional chemical insecticides. However, the evolution of pest resistance to Bt crops reduces their benefits. A total of 44 cases of field-evolved practical resistance and early-warning resistance to Bt crops have been reported, involving 15 different pest species, 14 Bt proteins, and 9 different countries. Here, an ARS scientist at Maricopa, AZ and a collaborator from China highlight the 9 global cases of field-evolved resistance to Bt crops where the underlying molecular mechanisms causing resistance are known and provide a comprehensive update on recent advances into the understanding of molecular mechanisms of laboratory-selected resistance to Bt proteins. Furthermore, new technological advances are described that have enabled greater understanding of the molecular complexities underlying the evolution of insect pest resistance to Bt crops, including those that permit the discovery of novel genetic mechanisms of resistance and for molecular monitoring of field evolved Bt resistance. Because knowledge of the causal basis of resistance is important for monitoring, managing, and countering pest resistance to Bt crops, these insights are vital for the sustainable management of many global insect pests.

Technical Abstract: Insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) are used globally as bioinsecticides and in genetically engineered Bt crops to manage key insect pests. Transgenic Bt crops have been cumulatively planted on more than 1.5 billion hectares for more than 27 years, providing enhanced pest suppression, improved yields, increased farmer profits, and reduced environmental and health risks associated with the decreased use of conventional chemical insecticides. These benefits are reduced or lost when pests evolve resistance to Bt toxins in the field. Understanding the molecular genetic basis of resistance can be useful for monitoring, managing, and countering pest resistance to Bt crops. To date, 26 cases of field-evolved practical resistance and 18 cases of early warning of resistance to Bt crops have been reported, but the molecular genetic basis is known for only 9 of the 44 resistance cases to Bt crops. Here, we provide a comprehensive update on the molecular genetic mechanisms for these nine cases of field-evolved resistance to Bt crops and the numerous cases of laboratory-selected resistance to Bt toxins. We highlight lab-selected resistance involving regulation of Bt receptor genes and how recent research shows that regulatory pathways can be coopted to cause resistance. We further review recent technological advances in genomics and reverse genetics that have improved our ability to monitor and understand of the molecular genetic basis of pest resistance. The findings outlined here describe not only the complex genetic nature of Bt resistance, but also highlights new areas of exploration into the fundamental evolutionary basis of resistance mechanisms, which are important for sustaining the efficacy of currently available and future transgenic Bt crops.