Triticeae Genomics and Genetics, 2024, Vol.15, No.1, 31-43 http://cropscipublisher.com/index.php/lgg 37 wheat transcriptional regulatory network, where lineage-specific TEs have been shown to drive regulatory innovations, particularly in response to environmental stressors (Zhang et al., 2021). Figure 3 Variability and similarity of the three subgenomic repeat compositions in wheat (Adapted from Wicker et al., 2018) Image caption: (a) shows the sequence alignment of approximately 300 kb homologous regions on chromosomes 3A, 3B, and 3D, where red and blue areas indicate regions with high sequence homology, demonstrating the high conservation of genes and the collinearity among the A-B-D genomes, but TEs are absent at the homologous positions.; (b) displays the proportions of the 20 most abundant TE families in the A, B, and D genomes of the hexaploid wheat genome; (c) presents the proportion of repetitive sequences defined by k-mers at different frequencies, showing the D genome has the highest proportion of 60-mer repeats, while the B genome has the lowest; (d) illustrates the distribution of 20-mer frequencies across the physical chromosomes, with the B genome having the lowest proportion of repeats (Adapted from Wicker et al., 2018) 5.2 Barley (Hordeum vulgare) Barley, another vital cereal crop within the Triticeae tribe, shares a close evolutionary relationship with wheat and other Triticeae species, has a genome that is heavily influenced by TEs, similar to wheat. The study of TEs in barley has provided insights into the evolutionary dynamics of these elements within the Triticeae tribe. For instance, the presence of specific TE families, such as Sabrina and Angela-A, has been observed in both barley and its diploid relatives, indicating their role in genome evolution and speciation. TEs in barley account for a substantial portion of the genome, predominantly consisting of LTR retrotransposons. The BARE1 element, a type of LTR retrotransposon, is highly prevalent in the barley genome and contributes significantly to its genetic composition (Middleton et al., 2013). Research has shown that the dynamics of TE proliferation in barley are linked to environmental stress and adaptation processes. The adaptive response facilitated by TEs is crucial for barley's survival and evolution under varying environmental conditions. This adaptive capacity is partly due to the ability of TEs to generate genetic variation, which is beneficial for coping with environmental changes (Middleton et al., 2013). The presence of lineage-specific TEs, such as the novel non-autonomous DNA transposon identified in the DRF1 gene, suggests
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