Transcriptome Analysis Reveals Key Genes Involved in Fatty Acid and Triacylglycerol Accumulation in Developing Sunflower Seeds

Abstract

Background/Objectives: Sunflower (Helianthus annuus L.) is one of the four major global oilseed crops. Understanding the molecular mechanisms regulating fatty acid synthesis and triacylglycerol (TAG) accumulation is crucial for improving oil yield and quality. In this study, the oilseed sunflower cultivar ‘T302’, which was wild-cultivated in the northwestern region of China, was analyzed for fatty acid content by targeted lipidomic analysis. RNA sequencing (RNA-seq) was performed on 15 cDNA libraries from sunflower embryos at five developmental stages (10, 17, 24, 31, and 38 days after flowering) to investigate gene expression patterns during oil accumulation. Differentially expressed genes (DEGs) related to fatty acid and triacylglycerol accumulation in developing sunflower seeds were identified. WGCNA was used to gain deeper insights into the mechanisms underlying lipid metabolism. Results: The oil composition of ‘T302’ consisted of 86.61% unsaturated fatty acids (UFA), mainly linoleic acid (48.47%) and oleic acid (37.25%). Saturated fatty acids (SFAs) accounted for 13.39%, with palmitic acid (7.46%) and stearic acid (5.04%) being the most abundant. A total of 81,676 unigenes were generated from RNA-seq data, and 91 DEGs associated with lipid metabolism were identified, including key enzymes such as FAD2-1, SAD, FATA, LACS, PDAT2, and DGAT2. In addition, we identified several novel candidate transcription factor genes, including WRI1, LEC1, FUS3, and ABI3, which were found to regulate TAG synthesis during seed maturation and are worthy of further investigation. This study provides valuable insights into the molecular mechanisms of seed oil biosynthesis in oilseed sunflower. The identified key genes and transcription factors provide potential targets for molecular breeding strategies to increase oil content and modify fatty acid compositions in sunflower and other oilseed crops.