Journal of Tea Science Research, 2024, Vol.14, No.3, 160-168 http://hortherbpublisher.com/index.php/jtsr 161 seeks to contribute to the application of CRISPR technology in agriculture and provide insights into its potential for revolutionizing tea cultivation. 2 CRISPR Technology in Plant Breeding 2.1 Mechanisms of CRISPR-Cas9 The CRISPR-Cas9 system, derived from a bacterial adaptive immune mechanism, has revolutionized genome editing by enabling precise and targeted modifications in plant genomes. The system relies on the complementarity of a guide RNA (gRNA) to a specific DNA sequence and the endonuclease activity of the Cas9 protein, which introduces double-strand breaks at the target site. These breaks are then repaired by the cell's natural repair mechanisms, either through non-homologous end joining (NHEJ) or homology-directed repair (HDR), leading to targeted gene modifications (Arora and Narula, 2017; Ahmad et al., 2020; Li et al., 2021). Recent advancements have expanded the CRISPR toolbox to include base editing and prime editing, which allow for even more precise nucleotide substitutions without introducing double-strand breaks (Chen et al., 2019; Zhu et al., 2020). 2.2 Applications of CRISPR in plant genomics CRISPR technology has been widely applied in plant genomics to enhance various traits, including disease resistance, yield, and quality. For instance, CRISPR-Cas9 has been used to develop disease-resistant crops by targeting and modifying susceptibility genes, thereby enhancing resistance to viral, fungal, and bacterial pathogens (Borrelli et al., 2018; Langner et al., 2018). Additionally, CRISPR has been employed to improve crop quality traits such as nutritional content, appearance, and palatability (Liu et al., 2021). The technology has also facilitated the creation of high-throughput mutant libraries and the fine-tuning of gene regulation, further accelerating crop improvement (Chen et al., 2019; Veillet et al., 2020). 2.3 Advantages over traditional breeding methods CRISPR technology offers several advantages over traditional breeding methods. Traditional breeding is often time-consuming and imprecise, relying on the natural occurrence of beneficial mutations and extensive backcrossing to eliminate undesirable traits. In contrast, CRISPR allows for precise, targeted modifications, significantly reducing the time required to develop new crop varieties (Arora and Narula, 2017; Ahmad et al., 2020). Moreover, CRISPR can introduce specific traits without the need for transgenes, resulting in non-GMO crops that are more acceptable to consumers and regulatory bodies (Langner et al., 2018; Ahmad et al., 2020). The versatility and efficiency of CRISPR make it a powerful tool for modern plant breeding, enabling the rapid development of crops with enhanced traits and improved resilience to environmental stresses (Schindele et al., 2018; Li et al., 2021). 3 Enhancing Tea Quality with CRISPR 3.1 Target traits for quality improvement The quality of tea is primarily determined by its flavor, aroma, and nutritional content. These traits are influenced by various biochemical compounds such as catechins, theaflavins, and volatile aromatic compounds. Enhancing these traits through genetic modification can significantly improve the overall quality of tea. For instance, increasing the levels of catechins and theaflavins can enhance the health benefits and taste profile of tea, while modifying the biosynthesis pathways of volatile compounds can improve its aroma (Liu et al., 2021). 3.2 Gene editing strategies for quality traits CRISPR/Cas9 technology offers a precise and efficient method for editing genes associated with quality traits in tea plants. This technology allows for targeted modifications in the genome, enabling the enhancement of specific traits without introducing foreign DNA. Strategies include the use of base-editing tools for targeted nucleotide substitutions and the development of DNA-free methods to avoid transgenic modifications (Chen et al., 2019). Additionally, CRISPR can be used to fine-tune gene regulation, thereby optimizing the expression of genes involved in the biosynthesis of quality-related compounds (Chen et al., 2019; Liu et al., 2021).
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