Molecular Plant Breeding 2024, Vol.15, No.6, 391-402 http://genbreedpublisher.com/index.php/mpb 393 2.2.2 Medicinal field The dried bark of Eucommia has been used as a top-grade herbal medicine for thousands of years. It is described in traditional Chinese medicine as “spicy in flavor and neutral in nature” and is often combined with other medicines in clinical practice. It has the effects of “alleviating pain in the waist and knees, replenishing vital energy, strengthening muscles and bones, stabilizing pregnancy, and promoting longevity with long-term use.” Eucommia has special efficacy in treating hypertension, particularly its unique ability to “regulate blood pressure in both directions,” a feat no chemical drug can match. Recent studies also suggest that Eucommia can lower cholesterol levels, prevent arteriosclerosis, and has marked anti-aging, anti-cancer, and body-function-enhancing effects. Research results have shown that chlorogenic acid exhibits strong scavenging effects on DPPH, ABTS, and OH free radicals (Yu et al., 2022). In vitro experiments have demonstrated that Eucommia leaf polysaccharides and polyphenols also have antioxidant activity (Wu, 2022). Research has also shown that the flavonoid components in 70% ethanol extract of Eucommia leaves have anti-neuroinflammatory activity in lipopolysaccharide-induced BV-2 mouse microglial cells and neuroprotective effects against H2O2-induced PC12 cells (Hu et al., 2023). Additionally, another study suggests that a triterpene compound from Eucommia leaves can reduce neuroinflammatory responses in microglial cells and improve neuroinflammation. Chlorogenic acid and geniposidic acid in Eucommia leaf extract also have excellent lipid-lowering effects, reducing white fat content in mouse tissues and leading to weight reduction (Hirata et al., 2011). 2.2.3 Food application field As a food and medicine homologous herb, Eucommia leaves are safe and have been widely applied in food. Eucommia leaf tea, made by frying fresh leaves, has certain antioxidant activity (Xu et al., 2021). Eucommia leaf brick tea is prepared by fresh leaves following a process consistent with the production of brick tea, including pressing, fermentation, and aging. The types and content of flavonoid and phenolic acid components in the tea are associated with microorganisms during the fermentation process (Zeng et al., 2021). Adding ultra-fine Eucommia leaf powder in steamed buns improves hardness, stickiness, and chewiness compared to regular buns and also offers certain nutritional benefits (Li et al., 2022). 2.2.4 Feed additive applications Research shows that adding 4% to 6%Eucommia leaf powder to Yellow River carp feed can increase amino acid content in the fish meat, improving taste and nutritional value (Li et al., 2021). Studies also found that adding 4% Eucommia leaf powder to Green Shell chicken feed improves meat quality (Mao et al., 2021). Research by Li et al. (2022) also indicates that adding Eucommia leaf fermentation products and extracts to chicken feed promotes chick development, improves meat quality, and enhances immunity. In Nagano Prefecture, Japan, a local company added 2% to 3%Eucommia leaf powder to regular feed to produce high-quality eel feed. The fish fed with this feed had tender, delicious meat, distinct from those fed with regular feed. Using Eucommia leaves as a feed additive can greatly improve the economic benefits of the aquaculture industry. In summary, as market demand for Eucommia increases and its application fields continue to expand, improving cultivation techniques and conducting genetic modification to enhance yields to meet global demand has become an urgent priority. 3 Genetic Modification Techniques Relevant to Eucommia ulmoides 3.1 CRISPR-Cas9 and other gene editing tools The existing genome editing systems primarily include the Zinc Finger Nuclease (ZFNs) system, the Transcription Activator-Like Effector Nuclease (TALENs) system, and the CRISPR/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeat/CRISPR-associated protein 9) system. CRISPR-Cas9 technology, due to its simplicity, efficiency, and specificity, has become a revolutionary tool in the field of genetic improvement. This technology allows precise genome modification by targeting specific DNA sequences and introducing cuts. Through repair mechanisms, desired genetic changes can be introduced. CRISPR-Cas9, with its high precision in promoting targeted gene editing, has been widely applied in various fields, including plant biotechnology (Li et al., 2020; Sharma et al., 2020; Guo et al., 2023).
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