Integrated metabolomic and transcriptomic analysis reveal the flavor formation mechanism during oat grain development

Oats are globally significant cereals that are appreciated for their nutritional composition and flavor profiles. However, the dynamic changes in volatile organic compounds (VOCs) and their associated biosynthetic genes during grain development remain poorly characterized. We hypothesized that the variation in oat flavor profiles was influenced by specific VOCs, which were synthesized via dedicated biosynthetic pathways and associated genes. To test this, GC-MS-based VOC profiling was performed during oat grain development in cultivar Neiyou 6, and the resulting semi-quantitative metabolomic data were integrated with a published transcriptomic dataset to identify candidate genes and pathways associated with aroma-related VOC accumulation. A total of 168 VOCs were identified, with terpenoids and esters as the dominant classes, accumulating predominantly during the Filling Stage. Based on database-derived odor descriptors, the identified VOCs were putatively associated with green, fruity, and sweet notes throughout grain development. KEGG pathway enrichment analysis identified monoterpenoid biosynthesis as a candidate pathway associated with aroma-related VOC accumulation; α-pinene oxide was identified as a representative differentially accumulated monoterpenoid. Integrated analysis of 113 differentially accumulated metabolites and 40,703 differentially expressed genes pinpointed four candidate cytochrome P450 genes (CYP1-4) that may relate to α-pinene oxide accumulation. WGCNA and correlation network analysis further indicated CYP2 and CYP3 as candidate genes associated with α-pinene oxide accumulation. These findings provide a descriptive and correlative foundation for understanding VOC dynamics during oat grain development and identify candidate targets for future functional studies aimed at improving oat flavor quality.