As an important forage legume in the world, alfalfa (Medicago sativa L.) has high adaptability to various unfavorable climatic conditions and high biomass, and have been playing critical roles in animal husbandry and industrial applications. As α‐linolenic acid cannot be synthesized by animals, and most must be obtained from plants, the increasing of α‐linolenic acid content in alfalfa will greatly contribute to improve quality of livestock. However, the molecular mechanisms for α‐linolenic acid synthesis and accumulation in alfalfa are still limited. In this study, the importance of ω‐3 fatty acid desaturase (FAD) was demonstrated by analyzing α‐linolenic acid metabolic pathways, combined with the dynamics of accumulation of unsaturated fatty acids in alfalfa. Moreover, the FAD3.1 identified in alfalfa was located in the endoplasmic reticulum, and its expression level was consistent with the accumulation patterns of α‐linolenic acid in leaves. Heterologous expression in yeast cells proves that MsFAD3.1 was involved in the synthesis of α‐linolenic acid, and the α‐linolenic acid content in MsFAD3.1‐overexpression transgenic alfalfa lines was significantly increased. These results indicate that new alfalfa germplasm with high α‐linolenic acid content can be successfully created through biotechnology, providing a theoretical basis for further improving the quality of alfalfa and the nutritional value of dairy products.

中文翻译：

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苜蓿中FAD基因家族的全基因组鉴定和涉及α-亚麻酸积累的MsFAD3.1功能分析

作为世界上重要的豆科牧草，苜蓿（紫花苜蓿L.）对各种不利的气候条件和高生物量具有高度的适应性，并且在畜牧业和工业应用中起着至关重要的作用。由于动物无法合成α-亚麻酸，并且大多数必须从植物中获得，因此苜蓿中α-亚麻酸含量的增加将极大地改善牲畜的质量。但是，苜蓿中α-亚麻酸合成和积累的分子机制仍然有限。在这项研究中，通过分析α-亚麻酸的代谢途径，并结合苜蓿中不饱和脂肪酸的积累动力学，证明了ω-3脂肪酸去饱和酶（FAD）的重要性。此外，在苜蓿中鉴定出的FAD3.1位于内质网中，其表达水平与叶片中α-亚麻酸的积累模式一致。酵母细胞中的异源表达证明MsFAD3.1参与了α-亚麻酸的合成，MsFAD3.1-过表达转基因苜蓿品系中α-亚麻酸的含量显着增加。这些结果表明，可以通过生物技术成功地创造出具有高α-亚麻酸含量的新苜蓿种质，为进一步提高苜蓿的质量和乳制品的营养价值提供了理论基础。