Maize Genomics and Genetics 2024, Vol.15, No.4, 204-217 http://cropscipublisher.com/index.php/mgg 209 Additionally, CRISPR has been employed to improve the nutritional quality of maize. By editing genes involved in the biosynthesis of essential nutrients, researchers have created maize varieties with increased levels of vitamins, minerals, and other beneficial compounds. This has significant implications for addressing malnutrition and improving food security (Monsur et al., 2020; Wang and Doudna, 2023). CRISPR technology has also facilitated the development of maize varieties with improved yield and growth characteristics. By targeting genes that regulate plant architecture, flowering time, and grain development, scientists have been able to create maize plants that produce higher yields and are better suited to different growing conditions (Kumlehn et al., 2018; Li et al., 2021). 4.3 Ethical considerations and regulatory framework The rapid advancement of CRISPR technology has raised important ethical and regulatory considerations. One major concern is the potential for off-target effects, where unintended genetic modifications occur. While advancements in CRISPR technology have improved its precision, the risk of off-target effects remains, necessitating thorough evaluation and validation of edited plants (Bortesi and Fischer, 2015; Moon et al., 2019; Li et al., 2021). Ethical considerations also extend to the broader implications of genome editing in agriculture. The use of CRISPR to create genetically modified organisms (GMOs) has sparked debates about food safety, environmental impact, and the socio-economic consequences for farmers and consumers. Public perception and acceptance of CRISPR-edited crops are critical factors that influence regulatory policies and market adoption (Bortesi and Fischer, 2015; Wang and Doudna, 2023). Regulatory frameworks for CRISPR-edited crops vary globally. In some regions, such as the United States, CRISPR-edited crops are regulated similarly to traditional GMOs, with rigorous safety assessments and approval processes. In contrast, other regions, like the European Union, have stricter regulations that may limit the commercialization of CRISPR-edited crops. Harmonizing these regulatory approaches is essential to facilitate the global adoption of CRISPR technology in agriculture (Bortesi and Fischer, 2015; Moon et al., 2019; Wang and Doudna, 2023). In conclusion, CRISPR technology has significantly advanced maize breeding by enabling precise genetic modifications that enhance important agronomic traits. However, ethical considerations and regulatory frameworks must be carefully navigated to ensure the safe and responsible use of this powerful technology. Continued research and dialogue among scientists, policymakers, and the public are crucial for realizing the full potential of CRISPR in agriculture. 5 Transcriptomics and Gene Expression Profiling 5.1 Advances in transcriptome sequencing technologies The advent of advanced transcriptome sequencing technologies has revolutionized the field of maize genomics, providing unprecedented insights into gene expression and regulation. Single Molecule Real-Time (SMRT) sequencing, for instance, has significantly improved the assembly and annotation of the maize genome. This technology has enabled the identification of over 130 000 intact transposable elements and the generation of 111 000 full-length transcripts, which are crucial for understanding the functional and regulatory elements within the maize genome (Jiao et al., 2017). These advancements have facilitated the characterization of complex repeat regions and intergenic spaces, which were previously challenging to assemble accurately. Moreover, large-scale transcriptome profiling across various tissues and developmental stages has provided a comprehensive view of gene expression dynamics in maize. For example, transcriptome profiling of 23 different tissues or developmental stages in maize inbreds B73 and Mo17, as well as their F1 hybrid, revealed extensive differential expression and regulatory variation. This study highlighted the dynamic nature of gene expression and the prevalence of tissue-specific regulatory mechanisms, which are essential for understanding phenotypic variation and heterosis in maize (Figure 3) (Zhou et al., 2019).
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