Metabolic and transcriptomic analyses reveal different metabolite biosynthesis profiles between leaf buds and mature leaves in Ziziphus jujuba mill

Jujube leaf is well known for its high nutritional value and medicinal benefits. However, a thorough and dynamic assessment of the metabolites present in jujube leaves is lacking. Here, the primary and secondary metabolites from purple leaf buds and green mature leaves were investigated using ultra-high-performance liquid chromatography/tandem mass spectrometry. A total of 778 metabolites were characterized and more than 700 compounds were reported for the first time. Analysis of differentially accumulated metabolites showed that the flavonoids were the major differential metabolites and determined the leaf coloration. The transcriptome data indicated that 20 flavonoid structural genes and three main types of flavonoid regulatory genes were significantly differentially expressed. Moreover, light had a significant influence on flavonoid accumulation. These results improve our understanding of metabolite accumulation and the molecular mechanisms of flavonoid biosynthesis in jujube leaf.