Maize Genomics and Genetics 2024, Vol.15, No.3, 123-135 http://cropscipublisher.com/index.php/mgg 129 6 Transposable Elements as Agents of Evolutionary Innovation 6.1 Examples of adaptive traits in maize linked to TEs Transposable elements (TEs) have been instrumental in shaping the genetic landscape of maize, contributing to its adaptive traits and overall genetic diversity. One notable example is the role of TEs in generating allelic diversity and structural variation, which can lead to significant phenotypic changes. For instance, TIR elements, a type of Class II DNA TEs, have been shown to influence gene expression and genome structure in maize. The development of new methods for TIR element detection has revealed a much larger presence of these elements in the maize genome than previously thought, highlighting their potential impact on adaptive traits (Su et al., 2019). Moreover, TEs can facilitate adaptive responses to environmental challenges by increasing genome plasticity. This plasticity allows for rapid genetic changes that can be beneficial under stress conditions, such as drought or pest resistance. The ability of TEs to induce such changes is particularly relevant in species like maize, which frequently encounter novel environments (Schrader and Schmitz, 2018). Additionally, TEs can contribute to the formation of new regulatory sequences and genes through processes like exaptation, where TE sequences are co-opted for new functions beneficial to the host (Etchegaray et al., 2021). 6.2 Potential for TEs to drive speciation The role of TEs in speciation is a burgeoning area of research, with evidence suggesting that these elements can contribute to reproductive iso lation and the emergence of new species. TEs can alter regulatory networks and gene expression, leading to significant genomic rearrangements that may result in hybrid defects. These defects can act as barriers to gene flow between nascent species, thereby facilitating speciation (Serrato-Capuchina and Matute, 2018). In maize, the high activity and diversity of TEs create a dynamic genomic environment that can drive speciation. The interplay between TEs and the host genome can lead to the development of unique genetic traits that distinguish one population from another. For example, the insertion of TEs near genes involved in reproductive processes can result in changes that prevent interbreeding between populations, thus promoting speciation (Stitzer et al, 2019). Furthermore, TEs can contribute to the evolution of lineage-specific traits by providing raw genetic material for innovation. In vertebrates, for instance, TEs have been implicated in the evolution of key innovations such as adaptive immunity and complex brain structures (Warren et al., 2015). Similarly, in maize, TEs can drive the evolution of traits that are crucial for survival and reproduction in specific environments, thereby contributing to the diversification of the species. TEs are not merely passive elements within the genome but active players in the evolutionary process. Their ability to induce genetic variability and influence gene expression makes them powerful agents of evolutionary innovation. In maize, TEs have been linked to adaptive traits and have the potential to drive speciation by creating reproductive barriers and facilitating the evolution of unique genetic traits. Understanding the role of TEs in these processes is crucial for comprehending the broader mechanisms of evolution and genetic diversity in plants. 7 TEs and Genomic Stability 7.1 Negative impacts of TE activity Transposable elements (TEs) are known to significantly impact genomic stability, often leading to deleterious consequences. The mobilization of TEs can cause mutations, chromosomal rearrangements, and gene disruptions, which can result in diseases and other dysfunctions. For instance, TEs can induce harmful mutations by inserting themselves into essential genes or regulatory regions, thereby disrupting normal gene function and potentially leading to lethality (Klein and O’Neill, 2018; Schrader and Schmitz, 2018; Romano and Fanti, 2022). In the fungal wheat pathogen Zymoseptoria tritici, TE activity has been shown to destabilize genome integrity, although it can also confer adaptive variation in pathogenicity or resistance traits (Oggenfuss and Croll, 2023). Moreover, the proliferation of TEs can lead to genome instability by creating novel chromosome rearrangements and impacting gene expression, which can result in disease in some cases and species-specific diversity in others (Klein and O’Neill, 2018). In Drosophila species, TE mobilization poses a constant threat to genome integrity, necessitating robust defensive mechanisms to suppress their activity (Wei et al., 2022). The negative association
RkJQdWJsaXNoZXIy MjQ4ODYzNQ==