Transcriptome Sequencing Reveals Key Genes for Sunflower Unsaturated Fatty Acid Synthesis

Background Sunflower is an important oil crop with rich nutrients. With the development of genetic engineering technology, sunflower genetic engineering breeding has become an important way for breeders to improve the quality of sunflower. Methods In this experiment five oil sunflower varieties from different regions were analyzed for fatty acid content over the growth process. The seed embryos of one of the high oleic acid varieties were subjected to transcriptome sequencing at different stages with RNA-Seq. Furthermore, quantitative fluorescent analysis was performed on the genes related to the biosynthetic pathways of unsaturated fatty acids. As the results showed, oleic acid synthesis dominated the unsaturated fatty acid synthesis pathways in seed embryos. Substantial differentially expressed genes were detected at various post-flowering stages. Specifically, the up-regulated genes were highest in quantity at 10 d after flowering, while most genes were down-regulated at 20 d after flowering. The enriched genes were rather consistent, with almost all experimental groups exhibiting enrichment to the 110894736 (FAD2) gene. In terms of correlation, the expression of FAD2 gene was highly significantly negatively correlated with the expressions of FAD6, FAD3 and FAD7 genes, During seed embryo synthesis, the expression level of FAD2 gene was highly significantly negatively correlated with the final oleic acid content, and was highly significantly positively correlated with the final linoleic acid content. Conclusion this suggests that the FAD2 gene is a key enzyme gene catalyzing the oleic to linoleic acid conversion.