ABSTRACT
Bacillus thuringiensis (Bt) is a gram positive, ubiquitous soil microorganism that forms endospores and parasporal bodies during the stationary phase. The parasporal bodies are commonly known as δ endotoxins and are insecticidal in nature. These parasporal bodies are produced by cry genes present in the Bt. Until now, more than 75 cry genes have been reported from various strains of Bt, and they have different target insects. The variation in cry genes structure and function plays a critical role in their target insect group also their mode of action. Hence, in this chapter a vivid description about the structural and functional diversity of cry genes along with their cry receptors and their mode of action is done. Initially, the Bt is used as a biopesticide for managing various agricultural insect pests as well as forest defoliators by topical application. Until now, Bt biopesticide occupies the largest share among the microbial biopesticides in the world. The biotechnological advancements made it possible to utilize the cry genes for developing insect-resistant genetically modified (GM) plants. The utilization of different cry genes in developing insect-resistant GM plants is also given.
