Maize Genomics and Genetics 2024, Vol.15, No.3, 147-159 http://cropscipublisher.com/index.php/mgg 152 transposons make up a substantial portion of the genome, with estimates suggesting that they constitute up to 90% of the total genomic content (Xue and Goldenfeld, 2016). The insertion and subsequent amplification of transposons can lead to large-scale genomic alterations, including inversions, deletions, and duplications, which can have profound effects on genome architecture (Bhat et al., 2022). Figure 2 TE-regulated mechanisms of action in the host cells (Adopted from Bhat et al., 2022) Image caption: Cis-regulatory mechanisms involving (A) promoter and (B) enhancer, integrate the activity of specific transcription factor; (C) insulator, act either through enhancer-blocking activity or chromatin barrier activity; (D) silencer, silence the expression of genes; Retrotransposon mechanism can increase the potential of transcription binding factor. (orange arrowhead indicates increased activity, blue cross indicates silencing of activity, circle with single cross indicates insulation of gene activity, grey arrow indicates direction of action) (Adopted from Bhat et al., 2022) The presence of transposons can also lead to the formation of new genomic regions with distinct structural features. For instance, the insertion of transposons can create new sites for chromatin remodeling, thereby influencing the overall organization of the genome. This dynamic restructuring of the genome by transposons is a key driver of genomic diversity and evolution (Elbarbary et al., 2016; Bhat et al., 2022). In addition to generating genetic diversity through insertional mutagenesis, transposons can also facilitate the horizontal transfer of genetic material between species. This horizontal gene transfer can introduce new genes and regulatory elements into a genome, further enhancing genetic diversity and evolutionary potential. The dual role of transposons as both creators of genetic variation and facilitators of gene transfer underscores their importance in the evolutionary process (Percharde et al., 2020; Bhat et al., 2022). 5.4 Specific examples of transposon-induced mutations One notable example of a transposon-induced mutation is the insertion of the transposable element Ac (Activator) in the maize genome, which can cause the breakage of chromosomes and lead to variegated phenotypes in maize kernels. This phenomenon was first described by Barbara McClintock and has since been recognized as a classic example of transposon activity influencing genetic traits (Perween et al., 2020). Another example is the role of the Long INterspersed Element-1 (LINE-1 or L1) in human disease. LINE-1 is a type of non-LTR retrotransposon that is currently active in humans and has been implicated in various genetic
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