Triticeae Genomics and Genetics, 2024, Vol.15, No.1, 31-43 http://cropscipublisher.com/index.php/lgg 33 genome (Sabot and Schulman, 2009). This high abundance underscores the impact of TEs on genome size and structure. Figure 1 Mechanisms schematic representation of Class I and Class II TEs (Adapted from Colonna Romano and Fanti, 2022) The distribution of TEs within the genome is influenced by various factors, including the genomic context and the presence of specific regulatory mechanisms that control TE activity. For instance, TEs can be silenced through epigenetic modifications, but they can also be reactivated under certain conditions, such as environmental stress or during specific developmental stages (Ali et al., 2021; Colonna Romano and Fanti, 2022). The dynamic nature of TEs and their ability to induce genetic variability make them crucial players in the evolution of the Triticeae genome. TEs are not evenly distributed within the genome; they tend to cluster in specific regions such as near centromeres and telomeres, and are often less prevalent in gene-rich areas. For instance, CACTA elements are frequently associated with gene regions, contributing to their regulation and evolutionary significance (Wicker et al., 2003). Additionally, the composition and dynamics of TEs vary among different Triticeae species. The BARE1 element, for example, is a significant contributor to the genomes of several Triticeae species, including wheat and barley, and shows considerable variation in its abundance and activity between species (Middleton et al., 2013). 2 Transposable Elements and Genetic Diversity 2.1 Contribution to genetic variation Transposable elements (TEs) significantly contribute to genetic variation genomes by introducing novel insertions that can disrupt or alter gene functions (Figure 2). This insertional mutagenesis can generate genetic diversity and impact various traits, influencing adaptation and evolution. Recent studies have shown that TEs in Triticeae, such as in Thinopyrum intermedium and its diploid relatives, display considerable variation in copy number and abundance, highlighting their role in creating genetic diversity (Divashuk et al., 2019). Furthermore, the novel non-autonomous DNA transposon identified in the DRF1 gene in Triticum durum and other Triticeae species suggests recent evolutionary activity contributing to genetic variability (Thiyagarajan et al., 2022). 2.2 Role in gene and genome evolution TEs are integral to gene and genome evolution, facilitating the emergence of new gene functions and regulatory
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