Identification of candidate proteins related to oleic acid accumulation during sunflower (Helianthus annuus L.) seed development through comparative proteome analysis

As a crucial oil crop, sunflower (Helianthus annuus L.) has a high content of unsaturated fatty acids (FAs). The unsaturated FAs found in sunflower oil mainly include oleic acid (OA, C18:1) and linoleic acid (LOA, C18:2). OA's antioxidant activity makes sunflower oil with high health value and suitable for storage. However, molecular mechanisms underlying differences in OA accumulation between high- and low-oleate sunflower varieties in seed development remain unexplored. Here, to identify key OA synthesis-related proteins, isobaric tag for relative and absolute quantitation (iTRAQ) was performed. Ultimately, 592 differentially expressed proteins (DEPs) (233 upregulated, 359 downregulated) were identified between high-oleate ('L-1-OL-1') and low-oleate ('86-1') maintainer lines. KEGG enrichment analysis of DEPs identified biosynthesis of unsaturated FAs as the most highly enriched biological pathway. Subsequently, combined transcriptome and proteome analysis results suggested that several proteins in this pathway might influence final seed OA content, including FAD2 (Delta 12 fatty acid desaturase). Notably, FAD2 expression was significantly downregulated in 'L-1-OL-1' versus '86-1' seeds, with results aligning with FAD2 mRNA expression results determined via qRT-PCR analysis. These findings and understanding of OA synthesis mechanisms could help improve oil quality through breeding and germplasm-based efforts in sunflower.