Bt Research 2025, Vol.16, No.3, 118-124 http://microbescipublisher.com/index.php/bt 119 Combining the latest achievements of high-throughput sequencing technology, the structure and function of the Bt epigenetic regulatory network are summarized to provide theoretical support for the subsequent functional improvement and application expansion of Bt (Perri et al., 2017; Gu et al., 2024). 2 Overview of Epigenetic Mechanisms in Prokaryotes 2.1 DNA methylation DNA methylation is the most common epigenetic regulatory mode in prokaryotes. Bacteria rely on DNA methyltransferases (such as Dam, CcrM, etc.) to add methyl groups to specific positions, such as the N6 position of adenine or the C5 position of cytosine. This will affect processes such as gene expression, chromosome replication, DNA repair, pathogenicity and quorum sensing. Methylation can also alter the binding of transcription factors to DNA, thereby affecting the transcriptional level of genes (Gao et al., 2023). In recent years, whole-genome analyses by high-throughput sequencing have shown that there are many ways of methylation in bacteria, which are also closely related to phenotypic changes. 2.2 Histone-like proteins Although prokaryotes do not have the typical histones found in eukaryotes, many bacteria and archaea have similar proteins, such as HU, H-NS and IHF, etc. These proteins can bind to DNA, alter the structure of chromosomes and regulate gene expression. They can also bend DNA to form higher-level structures, thereby influencing transcription initiation and chromosomal function. At this point, their role is somewhat similar to histone modification in eukaryotes (Gao et al., 2023). However, up to now, prokaryotes have not discovered a histone post-translational modification network as complex as that in eukaryotes. 2.3 Non-coding RNAs Non-coding Rnas (Ncrnas) are also involved in epigenetic regulation in prokaryotes. There are many small Rnas (srnas) in bacteria, which can complement and bind to mRNA, thereby affecting the stability and translation efficiency of mRNA. Some Ncrnas can also regulate the level or activity of DNA methylases, indirectly influencing gene expression. Although the types and functions of ncrnas in prokaryotes are not as numerous as those in eukaryotes, they still play important roles in environmental stress and metabolic regulation (Peschansky and Wahlestedt, 2014; Wei et al., 2017). 2.4 Comparison with Eukaryotic Epigenetics The epigenetic mechanisms of eukaryotes are rather complex, involving multiple levels such as DNA methylation, histone modification, chromatin remodeling and non-coding RNA. Histone modifications (such as acetylation, methylation and phosphorylation) and chromatin remodeling complexes are very important in gene expression, cell differentiation and development (Montecino et al., 2021; Zhao et al., 2021; Bure et al., 2022; Yang et al., 2022) (Figure 1). Compared with eukaryotes, the epigenetic mechanism of prokaryotes is relatively simple. It is mainly regulated by DNA methylation and histone proteins, and the role of ncRNA is also relatively limited. Of course, the two types of organisms still have some commonalities in gene expression regulation and phenotypic plasticity, and both can rapidly adapt to the environment through epigenetic methods (Bure et al., 2022; Yang et al., 2022; Gao et al., 2023). 3 Epigenetic Modifications inBacillus thuringiensis 3.1 Current evidence At present, there are not many direct studies on the epigenetic modifications of Bacillus thuringiensis (Bt), but some related studies have provided clues. For example, in the Galleria mellonella model, prolonged exposure to Bt can cause changes in DNA methylation and histone acetylation in the host, and also affect the expression of some related enzymes. Meanwhile, the changes in miRNA expression profiles are also related to the acquisition of Bt resistance. These mirnas target specific mrnas, thereby regulating immune and stress-related genes (Mukherjee et al., 2017). Although these findings mainly focused on the host, they also suggest that Bt itself may control gene expression through a similar mechanism.
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