Comparative Study of Fatty Acid Desaturase (FAD) Members Reveals Their Differential Roles in Upland Cotton

Cottonseed oil is rich in unsaturated fatty acids (UFAs), making it suitable for use as edible oil. Fatty acid desaturases (FADs) play a major role in the conversion of monounsaturated fatty acids (MUFAs) to polyunsaturated fatty acids (PUFAs). In total, 39 GhFAD genes were detected in upland cotton and divided into five groups in the present study. Gene structure and domain analysis showed that GhFAD members within each group were highly conserved. Cis-elements associated with environmental stress and hormone responses were identified in GhFAD promoters. The predicted transcription factors and miRNAs targeting these genes suggest extensive roles for GhFADs in diverse stress conditions. Analysis of expression profiles indicated that GhFAD genes participate extensively in developmental processes and stress adaptation in cotton. Among these, the concurrent high expression of GhFAD2-1 and low expression of GhFAD3 are consistent with the typical fatty acid profile of cottonseed oil. GhFAD3-2 and GhFAD3-1 exhibit a complementary expression profiles, suggesting they may operate in a relay manner during fiber development. Additionally, experimental evidence established that GhFAD2-3 is involved in the cold stress response. This research delivers a thorough characterization of the GhFAD genes in upland cotton, thereby establishing a solid groundwork for future functional genomics studies.