Molecular Plant Breeding 2024, Vol.15, No.5, 317-327 http://genbreedpublisher.com/index.php/mpb 318 This study is to explore the potential of gene editing technology in improving the quality characteristics of Eucalyptus wood. It involves a comprehensive understanding of genomic strategies employed to enhance Eucalyptus wood quality, identifying potential genetic targets for future research, and gaining deep insights into the practical applications of gene editing in forestry. By thoroughly analyzing how modern genomic tools can revolutionize Eucalyptus breeding programs, the study aims to ultimately promote more efficient and sustainable forestry practices, thereby contributing to the field. 2 Genome Editing Technologies for Wood Quality Improvement 2.1 CRISPR/Cas9 system The CRISPR/Cas9 system has emerged as a groundbreaking technology in genetic engineering, enabling precise modifications of the genome. The CRISPR/Cas9 system has revolutionized genome editing due to its simplicity, efficiency, and versatility (Liu et al., 2021; Min et al., 2022). This technology 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-stranded breaks at the target site. These breaks can be repaired by non-homologous end joining (NHEJ) or homology-directed repair (HDR), leading to targeted mutations or precise gene modifications (Bortesi and Fischer, 2015; Arora and Narula, 2017; Chen et al., 2019). In Eucalyptus, the CRISPR/Cas9 system has been successfully implemented to study wood-related genes. For instance, Dai et al. (2020) demonstrated the use of CRISPR/Cas9 in Eucalyptus hairy roots to target genes involved in lignin biosynthesis and auxin signaling. The study showed that editing the Cinnamoyl-CoA Reductase1(CCR1) gene resulted in decreased lignification and altered wood properties, highlighting the potential of CRISPR/Cas9 for functional genomics and wood quality improvement in Eucalyptus. 2.2 Genome editing techniques: base editing and prime editing Recent advancements in genome editing have led to the development of base editing and prime editing technologies, which allow for precise single-nucleotide modifications without introducing double-stranded breaks. Base editors use a modified Cas9 nickase fused to a deaminase enzyme to convert specific DNA bases, while prime editors use a reverse transcriptase to directly write new genetic information into the DNA (Li et al., 2021; Molla et al., 2021; Wang et al., 2021b). These precision editing tools have been applied to various plant species, including woody plants, to achieve targeted nucleotide substitutions with high efficiency and minimal off-target effects. Molla et al. (2021) analyzed the current status of base and prime editors in plants, emphasizing their potential for precise genome modifications and their applications in improving traits such as wood quality in Eucalyptus. 2.3 Delivery methods for genome editing Efficient delivery of genome editing tools into plant cells is crucial for the success of genetic modifications. Several methods have been developed to introduce CRISPR/Cas9 components, base editors, and prime editors into Eucalyptus cells, including Agrobacterium-mediated transformation, biolistic particle delivery, and protoplast transfection (Arora and Narula, 2017; Chen et al., 2019; Wang et al., 2021a). Wang et al. (2021a) described an efficient genetic transformation method for Eucalyptus using CRISPR/Cas9 technology. The study established a fluorescence labeling system to identify successfully transformed progenies, facilitating the selection of edited plants. This method can be used to improve Eucalyptus germplasm and enhance wood quality traits through precise genome editing. 3 Genetic Basis of Wood Quality Traits 3.1 Quantitative trait loci (QTL) mapping Quantitative trait loci (QTL) mapping is a powerful tool for identifying the genetic regions associated with complex traits. QTL mapping has been instrumental in identifying the genetic basis of wood quality traits in Eucalyptus. For instance, a study on E.urophylla × tereticornis hybrids identified 108 QTLs related to growth and wood property traits, with only a few showing stability across different environments. Notably, the QTL
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