The Molecular Cloning and Functional Analysis of the FAD2 Gene in Hippophe rhamnoids L.

Seabuckthorn (<i>Hippophae rhamnoides</i> Linn.) is a commonly utilized medicinal crop with various applications in the treatment of different diseases. Two particularly noteworthy nutrients in seabuckthorn fruit are seabuckthorn oil and flavonoids. In recent years, seabuckthorn oil has attracted considerable attention due to its perceived benefits for beauty and healthcare. Consequently, there is a clear need for further research into seabuckthorn oil. While numerous studies have been conducted on the regulation of oil by the <i>FAD2</i> gene family, there is a paucity of literature examining the molecular mechanism of <i>FAD2</i> gene involvement in seabuckthorn oil regulation. Accordingly, two <i>FAD2</i> genes have been identified in seabuckthorn, which are classified differently and perform distinct functions. Both genes are located in the endoplasmic reticulum. Following transient expression in seabuckthorn fruits, it was observed that <i>HrFAD2-1</i> and <i>HrFAD2-3</i> were capable of influencing the synthesis of α-linolenic acid, with <i>HrFAD2-1</i> additionally demonstrated to facilitate the synthesis of lysophosphatidic acid. All of the aforementioned genes have been observed to promote jasmonic acid (JA) synthesis. The heterologous transformation of <i>Linum usitatissimum</i> demonstrates that both <i>HrFAD2-1</i> and <i>HrFAD2-3</i> are capable of promoting plant growth. The <i>HrFAD2-1</i> gene was observed to significantly increase the content of major fatty acids in <i>Linum usitatissimum</i> Linn seeds, whereas the <i>HrFAD2-3</i> gene appeared to be primarily involved in the regulation of plant growth and development. In conclusion, a preliminary investigation into the functions of the <i>HrFAD2-1</i> and <i>HrFAD2-3</i> genes in fatty acid synthesis was conducted. This revealed that <i>HrFAD2-1</i> is closely associated with oleic acid synthesis and acts as a negative regulator. Furthermore, our findings will provide a foundation for subsequent investigations into the fatty acid synthesis pathway in <i>Hippophae rhamnoides</i> oil, offering a theoretical basis for subsequent studies at the molecular level.