Bt Research 2024, Vol.15, No.2, 76-86 http://microbescipublisher.com/index.php/bt 84 toxin genes, as seen in strains like H3 and ATCC 10792, enhances the bacterium's ability to combat a broad spectrum of insect pests. The ability of these plasmids to transfer horizontally between species, as demonstrated by pTAND672-2, further underscores their evolutionary significance and potential for genetic engineering to develop more effective biopesticides. Additionally, the discovery of toxin-antitoxin systems on these plasmids, such as the KyAB and tasAB systems, provides insights into plasmid stability and maintenance, which are essential for the long-term efficacy of Bt-based products. Future research should focus on several key areas to further our understanding and application of plasmid-encoded toxins in Bacillus thuringiensis. Genomic and proteomic characterization efforts should continue, as sequencing and analyzing the genomes and proteomes of various Bt strains will help identify novel toxins and their genetic organizations. This can lead to the discovery of new biopesticidal agents with enhanced efficacy and specificity. Investigating the mechanisms underlying the horizontal transfer of toxin-encoding plasmids, such as pTAND672-2, can provide insights into the spread and evolution of these elements. Understanding these processes can aid in developing strategies to prevent the emergence of resistance in target insect populations. Detailed studies on the function and regulation of toxin-antitoxin systems, like KyAB and tasAB, are also crucial. These studies can reveal their roles in plasmid stability and bacterial survival, and this knowledge can be leveraged to design more stable and effective Bt strains for biopesticide production. Recombinant plasmid development should be pursued by constructing recombinant plasmids that combine genes from different Bt subspecies or other bacteria. This approach can create strains with broader host ranges and improved insecticidal properties, leading to the development of next-generation biopesticides that are more effective and environmentally friendly. By addressing these areas, researchers can enhance the utility of Bacillus thuringiensis as a biocontrol agent and contribute to sustainable agricultural practices. Acknowledgments The authors are quite grateful to two anonymous peer experts for their feedback on the manuscript of this study. Conflict of Interest Disclosure The authors affirm that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest. References Argôlo-Filho R., and Loguercio L., 2013, Bacillus thuringiensis Is an environmental pathogen and host-specificity has developed as an adaptation to human-generated ecological niches, Insects, 5: 62-91. https://doi.org/10.3390/insects5010062 Bourchookarn W., Bourchookarn A., Imtong C., Li H., and Angsuthanasombat C., 2021, His180 in the pore-lining α4 of the Bacillus thuringiensis Cry4Aa δ-endotoxin is crucial for structural arrangements of the α4-α5 transmembrane hairpin and hence biotoxicity, Biochimica et Biophysica Acta (BBA)-Proteins and Proteomics, 1869(6): 140634. https://doi.org/10.1016/j.bbapap.2021.140634 Cao B., Shu C., Geng L., Song F., and Zhang J., 2020, Cry78Ba1, one novel crystal protein fromBacillus thuringiensis with high insecticidal activity against rice planthopper, Journal of Agricultural and Food Chemistry, 68(8): 2539-2546. https://doi.org/10.1021/acs.jafc.9b07429 Chelliah R., Wei S., Park B., Park J., Park Y., Kim S., Jin Y., and Oh D., 2019, New perspectives on Mega plasmid sequence (poh1) in Bacillus thuringiensis ATCC 10792 harbouring antimicrobial, insecticidal and antibiotic resistance genes, Microbial Pathogenesis, 126: 14-18. https://doi.org/10.1016/j.micpath.2018.10.013 Clark B., Phillips T., and Coats J., 2005, Environmental fate and effects of Bacillus thuringiensis (Bt) proteins from transgenic crops: a review, Journal of Agricultural and Food Chemistry, 53(12): 4643-4653. https://doi.org/10.1021/JF040442K Coates B., 2016, Bacillus thuringiensis toxin resistance mechanisms among Lepidoptera: progress on genomic approaches to uncover causal mutations in the European corn borer, Ostrinia nubilalis, Current Opinion in Insect Science, 15: 70-77. https://doi.org/10.1016/j.cois.2016.04.003 Dhania N., Chauhan V., Chaitanya R., and Dutta-Gupta A., 2019, Midgut de novo transcriptome analysis and gene expression profiling of Achaea janata larvae exposed with Bacillus thuringiensis (Bt)-based biopesticide formulation, Comparative Biochemistry and Physiology Part D: Genomics and Proteomics, 30: 81-90. https://doi.org/10.1016/j.cbd.2019.02.005
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