Transcriptome analysis reveals the mechanism associated with dynamic changes in fatty acid and phytosterol content in foxtail millet (Setaria italica) during seed development.

Foxtail millet (Setaria italica) is an excellent source of beneficial natural fatty acids and phytosterols. However, the mechanisms underlying the dynamic changes of fatty acids and phytosterols during seed development are unknown. In this study, a comprehensive dynamic change analysis of the bioactive compounds during seed development was conducted in two cultivars with different crude fat content (high-fat, JG 35 [5.40%]; and low-fat, JG 39 [2.90%]). GC-FID/MS analysis showed that the proportion of unsaturated fatty acids (UFAs) were higher than the saturated fatty acids (SFAs). UFA content first increased, then decreased during seed development, while SFA content showed the opposite trend. Oil contents continuously increased with seed development, especially at the S2 stage. Phytosterol contents initially increased, then decreased with seed development. Transcriptome analysis revealed that 152 genes were associated with fatty acid metabolism and phytosterol biosynthesis, of which 46 and 62 were related to UFA and phytosterol biosynthesis, respectively. Furthermore, the key genes involved in fatty acid synthesis (ACCase and FATA/B), triacylglycerol biosynthesis (LACS, GPAT, and DGAT), and phytosterols synthesis (CAS1, STM1, EGR6, and DWF1) were overexpressed. This led to maximum UFA, oil, and phytosterol accumulation in JG 35 at the S2 stage. This study reveals the mechanism behind the dynamic changes of fatty acid and phytosterol contents in foxtail millet during seed development.