Integrated Transcriptomic and Metabolomic Profiling Provides Molecular Insights into Volatile and Nonvolatile Metabolite Dynamics during Flower Development in Chinese Jujube and Sour Jujube

Chinese jujube and sour jujube flowers are recognized for their distinct fragrance and nutritional benefits. However, the currently reported classes of metabolites in these flowers remain relatively scarce, and their underlying molecular regulation remains unclear. Using gas chromatography–mass spectrometry and ultrahigh-performance liquid chromatography-electrospray ionization-tandem mass spectrometry, 369 volatile metabolites and 1840 nonvolatile metabolites were identified. Compared to Chinese jujube flowers, sour jujube flowers showed greater relative levels of the majority of differently accumulated metabolites. Ester and terpenoid compounds were the primary volatile differentially accumulated metabolites, whereas flavonoids constituted the dominant nonvolatile differentially accumulated metabolites. ZjMYB86 expression was negatively correlated with the late flavonoid structural genes. Functional overexpression studies demonstrated that ZjMYB86 inhibited anthocyanin accumulation. The ZjMYB86-overexpressing line showed downregulation of most anthocyanin metabolites and of the late biosynthetic gene ZjBZ1 compared to the control. Overall, these results enhanced understanding of the chemical profiles and metabolite distribution patterns in jujube flowers.