Genomics and Applied Biology 2024, Vol.15, No.4, 182-190 http://bioscipublisher.com/index.php/gab 183 The primary goal of this study is to explore the application of the CRISPR/Cas9 genome editing system in rice to develop superior yield traits. By reviewing recent advancements and applications of CRISPR/Cas9 in rice breeding, and assessing the efficiency, specificity, and heritability of CRISPR/Cas9-induced gene modifications in rice, we hope to highlight its potential in enhancing rice production and ensuring food security. 2 CRISPR/Cas9 Technology: Mechanism and Applications 2.1 Mechanism of CRISPR/Cas9 in gene editing The CRISPR/Cas9 system, which stands for Clustered Regularly Interspaced Short Palindromic Repeats and CRISPR-associated protein 9, is a revolutionary genome editing tool that has transformed genetic research and crop improvement. The mechanism involves an RNA-guided DNA endonuclease, Cas9, which is directed to a specific DNA sequence by a single-guide RNA (sgRNA). The sgRNA base-pairs with the target DNA sequence, allowing Cas9 to introduce double-strand breaks (DSBs) at the specified location. These DSBs trigger the cell's natural repair mechanisms, leading to mutations that can knock out or modify the function of the target gene (Bao et al., 2019; Li et al., 2021). 2.2 Comparison with other genome editing tools CRISPR/Cas9 has several advantages over earlier genome editing technologies such as Zinc Finger Nucleases (ZFNs) and Transcription Activator-Like Effector Nucleases (TALENs). Unlike ZFNs and TALENs, which require the design and assembly of protein-DNA binding domains for each target site, CRISPR/Cas9 uses a simple RNA molecule for targeting, making it easier to design and implement. Additionally, CRISPR/Cas9 is more versatile and cost-effective, allowing for the simultaneous editing of multiple genes (multiplexing) (Zeb et al., 2022; Zegeye et al., 2022). Recent advancements have also led to the development of Cas variants like ScCas9++ and Cas9-NG, which expand the targeting scope and improve editing efficiency in plants (Ren et al., 2019; Liu et al., 2021a). 2.3 Success Stories of CRISPR/Cas9 in plant research CRISPR/Cas9 has been successfully applied in various plant research projects, particularly in rice, to improve yield, quality, and stress resistance. For instance, the CRISPR/Cas9-mediated knockout of the Os8N3 gene in rice has conferred enhanced resistance to the bacterial pathogen Xanthomonas oryzae pv. oryzae without affecting other agronomic traits (Kim et al., 2019). Another notable success is the editing of the OsSAP gene to improve drought tolerance, which is crucial for maintaining yield under adverse climatic conditions (Park et al., 2022). Additionally, CRISPR/Cas9 has been used to improve rice grain quality by targeting genes involved in grain size, shape, and nutritional content (Fiaz et al., 2019; Zeb et al., 2022) (Figure 1). These examples highlight the potential of CRISPR/Cas9 to address key challenges in crop production and food security. 3 Yield Traits in Rice: Key Targets for Improvement 3.1 Understanding yield components in rice Yield in rice is a complex trait influenced by various components, including the number of grains per panicle, grain size, and panicle length. These components are critical as they directly impact the overall productivity of rice plants. For instance, the number of grains per panicle and the size of each grain are primary determinants of yield, while panicle length can influence the number of grains that can be supported (Jaganathan et al., 2018; Liu et al., 2021b). Understanding these components is essential for targeted genetic improvements aimed at enhancing rice yield. 3.2 Genetic basis of yield traits The genetic basis of yield traits in rice involves multiple genes that regulate various aspects of plant growth and development. Advances in genome sequencing have facilitated the identification of these genes, enabling precise genetic modifications. For example, genes such as OsPIN5b, GS3, and OsMYB30 have been identified as key regulators of panicle length, grain size, and stress tolerance, respectively (Zeng et al., 2018). The genetic control of these traits is often complex, involving interactions between multiple genes and environmental factors. Therefore, a comprehensive understanding of the genetic architecture is crucial for effective yield improvement strategies.
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