Mechanisms of Surface Flatness Variation in "Lingwuchangzao" Jujube: A Multi-Omics and Morphological Study.

Using high- and low-surface flatness fruits of Ziziphus jujuba Mill. cv. "Lingwuchangzao" at different developmental stages as test materials, this study examined the mechanisms underlying variations in fruit appearance and internal quality. The findings revealed significant differences between high-surface flatness (S fruits) and low-surface flatness (R fruits) throughout development. S fruits were glossy, smaller, and predominantly seedless, with lower single-fruit weight and thinner pericarp and pulp, while R fruits exhibited reduced glossiness, larger size, and deeper coloration. Transcriptome analysis identified key genes, including CER1 and FAR, involved in wax synthesis, influencing cuticular wax production on the fruit surface. Additionally, genes such as AUX/IAA affected epidermal cell development, leading to smaller and denser cells in R fruits, thereby impacting surface flatness. Collectively, genes regulating cell development and wax biosynthesis determined the glossiness of "Lingwuchangzao" jujube fruits. Metabolomic analysis identified 779 metabolites, with flavonoids constituting the most abundant class. Protein interaction network analysis highlighted the hub gene ABCG31, closely linked to wax synthesis, as a critical factor in fruit surface flatness and glossiness. This study elucidates the quality differences and molecular regulatory mechanisms between high- and low-surface flatness "Lingwuchangzao" jujube fruits, offering valuable insights for genetic improvement to enhance visual appeal and commercial value.